1
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Takeda R, Tsutsumi E, Okatsu K, Fukai S, Takeda K. Structural characterization of green fluorescent protein in the I-state. Sci Rep 2024; 14:22832. [PMID: 39353998 PMCID: PMC11445422 DOI: 10.1038/s41598-024-73696-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2024] [Accepted: 09/19/2024] [Indexed: 10/03/2024] Open
Abstract
Green fluorescent protein (GFP) is widely utilized as a fluorescent tag in biochemical fields. Whereas the intermediate (I) state has been proposed in the photoreaction cycle in addition to the A and B states, until now the structure of I has only been estimated by computational studies. In this paper, we report the crystal structures of the I stabilizing variants of GFP at high resolutions where respective atoms can be observed separately. Comparison with the structures in the other states highlights the structural feature of the I state. The side chain of one of the substituted residues, Val203, adopts the gauche- conformation observed for Thr203 in the A state, which is different from the B state. On the other hand, His148 interacts with the chromophore by ordinary hydrogen bonding with a distance of 2.85 Å, while the weaker interaction by longer distances is observed in the A state. Therefore, it was indicated that it is possible to distinguish three states A, B and I by the two hydrogen bond distances Oγ-Thr203···Oη-chromophore and Nδ1-His148···Oη-chromophore. We discuss the characteristics of the I intermediate of wild-type GFP on the bases of the structure estimated from the variant structures by quantum chemical calculations.
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Affiliation(s)
- Ryota Takeda
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Erika Tsutsumi
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Kei Okatsu
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Shuya Fukai
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Kazuki Takeda
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan.
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2
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Tutol J, Ong WSY, Phelps SM, Peng W, Goenawan H, Dodani SC. Engineering the ChlorON Series: Turn-On Fluorescent Protein Sensors for Imaging Labile Chloride in Living Cells. ACS CENTRAL SCIENCE 2024; 10:77-86. [PMID: 38292617 PMCID: PMC10823515 DOI: 10.1021/acscentsci.3c01088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 11/02/2023] [Accepted: 11/27/2023] [Indexed: 02/01/2024]
Abstract
Beyond its role as the "queen of electrolytes", chloride can also serve as an allosteric regulator or even a signaling ion. To illuminate this essential anion across such a spectrum of biological processes, researchers have relied on fluorescence imaging with genetically encoded sensors. In large part, these have been derived from the green fluorescent protein found in the jellyfish Aequorea victoria. However, a standalone sensor with a turn-on intensiometric response at physiological pH has yet to be reported. Here, we address this technology gap by building on our discovery of the anion-sensitive fluorescent protein mNeonGreen (mNG). The targeted engineering of two non-coordinating residues, namely K143 and R195, in the chloride binding pocket of mNG coupled with an anion walking screening and selection strategy resulted in the ChlorON sensors: ChlorON-1 (K143W/R195L), ChlorON-2 (K143R/R195I), and ChlorON-3 (K143R/R195L). In vitro spectroscopy revealed that all three sensors display a robust turn-on fluorescence response to chloride (20- to 45-fold) across a wide range of affinities (Kd ≈ 30-285 mM). We further showcase how this unique sensing mechanism can be exploited to directly image labile chloride transport with spatial and temporal resolution in a cell model overexpressing the cystic fibrosis transmembrane conductance regulator. Building from this initial demonstration, we anticipate that the ChlorON technology will have broad utility, accelerating the path forward for fundamental and translational aspects of chloride biology.
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Affiliation(s)
- Jasmine
N. Tutol
- Department
of Chemistry and Biochemistry and Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Whitney S. Y. Ong
- Department
of Chemistry and Biochemistry and Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Shelby M. Phelps
- Department
of Chemistry and Biochemistry and Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Weicheng Peng
- Department
of Chemistry and Biochemistry and Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Helen Goenawan
- Department
of Chemistry and Biochemistry and Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Sheel C. Dodani
- Department
of Chemistry and Biochemistry and Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas 75080, United States
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3
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Chen C, Zhang H, Zhang J, Ai HW, Fang C. Structural origin and rational development of bright red noncanonical variants of green fluorescent protein. Phys Chem Chem Phys 2023; 25:15624-15634. [PMID: 37211909 PMCID: PMC10330862 DOI: 10.1039/d3cp01315d] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The incorporation of noncanonical amino acids (ncAAs) into fluorescent proteins is promising for red-shifting their fluorescence and benefiting tissue imaging with deep penetration and low phototoxicity. However, ncAA-based red fluorescent proteins (RFPs) have been rare. The 3-aminotyrosine modified superfolder green fluorescent protein (aY-sfGFP) represents a recent advance, yet the molecular mechanism for its red-shifted fluorescence remains elusive while its dim fluorescence hinders applications. Herein, we implement femtosecond stimulated Raman spectroscopy to obtain structural fingerprints in the electronic ground state and reveal that aY-sfGFP possesses a GFP-like instead of RFP-like chromophore. Red color of aY-sfGFP intrinsically arises from a unique "double-donor" chromophore structure that raises ground-state energy and enhances charge transfer, notably differing from the conventional conjugation mechanism. We further developed two aY-sfGFP mutants (E222H and T203H) with significantly improved (∼12-fold higher) brightness by rationally restraining the chromophore's nonradiative decay through electronic and steric effects, aided by solvatochromic and fluorogenic studies of the model chromophore in solution. This study thus provides functional mechanisms and generalizable insights into ncAA-RFPs with an efficient route for engineering redder and brighter fluorescent proteins.
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Affiliation(s)
- Cheng Chen
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, USA.
| | - Hao Zhang
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, USA.
- Department of Molecular Physiology and Biological Physics and Center for Membrane and Cell Physiology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
| | - Jing Zhang
- Department of Molecular Physiology and Biological Physics and Center for Membrane and Cell Physiology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
| | - Hui-Wang Ai
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, USA.
- Department of Molecular Physiology and Biological Physics and Center for Membrane and Cell Physiology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
- The UVA Comprehensive Cancer Center, University of Virginia, Charlottesville, Virginia 22908, USA
| | - Chong Fang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, USA.
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4
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Deligönül N, Yildiz I, Bilgin S, Gokce I, Isildak O. Green Fluorescent Protein-Multi Walled Carbon Nanotube based Polymeric Membrane Electrode for Bismuth Ion Detection. Microchem J 2023. [DOI: 10.1016/j.microc.2023.108710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
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5
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Krueger TD, Tang L, Chen C, Zhu L, Breen IL, Wachter RM, Fang C. To twist or not to twist: From chromophore structure to dynamics inside engineered photoconvertible and photoswitchable fluorescent proteins. Protein Sci 2023; 32:e4517. [PMID: 36403093 PMCID: PMC9793981 DOI: 10.1002/pro.4517] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 10/31/2022] [Accepted: 11/15/2022] [Indexed: 11/21/2022]
Abstract
Green-to-red photoconvertible fluorescent proteins (FPs) are vital biomimetic tools for powerful techniques such as super-resolution imaging. A unique Kaede-type FP named the least evolved ancestor (LEA) enables delineation of the evolutionary step to acquire photoconversion capability from the ancestral green fluorescent protein (GFP). A key residue, Ala69, was identified through several steady-state and time-resolved spectroscopic techniques that allows LEA to effectively photoswitch and enhance the green-to-red photoconversion. However, the inner workings of this functional protein have remained elusive due to practical challenges of capturing the photoexcited chromophore motions in real time. Here, we implemented femtosecond stimulated Raman spectroscopy and transient absorption on LEA-A69T, aided by relevant crystal structures and control FPs, revealing that Thr69 promotes a stronger π-π stacking interaction between the chromophore phenolate (P-)ring and His193 in FP mutants that cannot photoconvert or photoswitch. Characteristic time constants of ~60-67 ps are attributed to P-ring twist as the onset for photoswitching in LEA (major) and LEA-A69T (minor) with photoconversion capability, different from ~16/29 ps in correlation with the Gln62/His62 side-chain twist in ALL-GFP/ALL-Q62H, indicative of the light-induced conformational relaxation preferences in various local environments. A minor subpopulation of LEA-A69T capable of positive photoswitching was revealed by time-resolved electronic spectroscopies with targeted light irradiation wavelengths. The unveiled chromophore structure and dynamics inside engineered FPs in an aqueous buffer solution can be generalized to improve other green-to-red photoconvertible FPs from the bottom up for deeper biophysics with molecular biology insights and powerful bioimaging advances.
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Affiliation(s)
| | - Longteng Tang
- Department of ChemistryOregon State UniversityCorvallisOregonUSA
| | - Cheng Chen
- Department of ChemistryOregon State UniversityCorvallisOregonUSA
| | - Liangdong Zhu
- Department of ChemistryOregon State UniversityCorvallisOregonUSA
| | - Isabella L. Breen
- School of Molecular Sciences, Center for Bioenergy and Photosynthesis, Biodesign Center for Applied Structural DiscoveryArizona State UniversityTempeArizonaUSA
| | - Rebekka M. Wachter
- School of Molecular Sciences, Center for Bioenergy and Photosynthesis, Biodesign Center for Applied Structural DiscoveryArizona State UniversityTempeArizonaUSA
| | - Chong Fang
- Department of ChemistryOregon State UniversityCorvallisOregonUSA
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6
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Liu J, He X. Recent advances in quantum fragmentation approaches to complex molecular and condensed‐phase systems. WIRES COMPUTATIONAL MOLECULAR SCIENCE 2022. [DOI: 10.1002/wcms.1650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Jinfeng Liu
- Department of Basic Medicine and Clinical Pharmacy China Pharmaceutical University Nanjing China
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, Shanghai Frontiers Science Center of Molecule Intelligent Syntheses, School of Chemistry and Molecular Engineering East China Normal University Shanghai China
| | - Xiao He
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, Shanghai Frontiers Science Center of Molecule Intelligent Syntheses, School of Chemistry and Molecular Engineering East China Normal University Shanghai China
- New York University‐East China Normal University Center for Computational Chemistry New York University Shanghai Shanghai China
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7
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John AM, Sekhon H, Ha JH, Loh SN. Engineering a Fluorescent Protein Color Switch Using Entropy-Driven β-Strand Exchange. ACS Sens 2022; 7:263-271. [PMID: 35006676 DOI: 10.1021/acssensors.1c02239] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Protein conformational switches are widely used in biosensing. They are often composed of an input domain (which binds a target ligand) fused to an output domain (which generates an optical readout). A central challenge in designing such switches is to develop mechanisms for coupling the input and output signals via conformational changes. Here, we create a biosensor in which binding-induced folding of the input domain drives a conformational shift in the output domain that results in a sixfold green-to-yellow ratiometric fluorescence change in vitro and a 35-fold intensiometric fluorescence increase in cultured cells. The input domain consists of circularly permuted FK506 binding protein (cpFKBP) that folds upon binding its target ligand (FK506 or rapamycin). cpFKBP folding induces the output domain, an engineered green fluorescent protein (GFP) variant, to replace one of its β-strands (containing T203 and specifying green fluorescence) with a duplicate β-strand (containing Y203 and specifying yellow fluorescence) in an intramolecular exchange reaction. This mechanism employs the loop-closure entropy principle, embodied by the folding of the partially disordered cpFKBP domain, to couple ligand binding to the GFP color shift. This study highlights the high-energy barriers present in GFP folding which cause β-strand exchange to be slow and are also likely responsible for the shift from the β-strand exchange mechanism in vitro to ligand-induced chromophore maturation in cells. The proof-of-concept design has the advantages of full genetic encodability and potential for modularity. The latter attribute is enabled by the natural coupling of binding and folding and circular permutation of the input domain, which theoretically allows different binding domains to be compatible for insertion into the GFP surface loop.
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Affiliation(s)
- Anna Miriam John
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, United States
| | - Harsimranjit Sekhon
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, United States
| | - Jeung-Hoi Ha
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, United States
| | - Stewart N Loh
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, United States
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8
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Chemically stable fluorescent proteins for advanced microscopy. Nat Methods 2022; 19:1612-1621. [PMID: 36344833 PMCID: PMC9718679 DOI: 10.1038/s41592-022-01660-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Accepted: 09/26/2022] [Indexed: 11/09/2022]
Abstract
We report the rational engineering of a remarkably stable yellow fluorescent protein (YFP), 'hyperfolder YFP' (hfYFP), that withstands chaotropic conditions that denature most biological structures within seconds, including superfolder green fluorescent protein (GFP). hfYFP contains no cysteines, is chloride insensitive and tolerates aldehyde and osmium tetroxide fixation better than common fluorescent proteins, enabling its use in expansion and electron microscopies. We solved crystal structures of hfYFP (to 1.7-Å resolution), a monomeric variant, monomeric hyperfolder YFP (1.6 Å) and an mGreenLantern mutant (1.2 Å), and then rationally engineered highly stable 405-nm-excitable GFPs, large Stokes shift (LSS) monomeric GFP (LSSmGFP) and LSSA12 from these structures. Lastly, we directly exploited the chemical stability of hfYFP and LSSmGFP by devising a fluorescence-assisted protein purification strategy enabling all steps of denaturing affinity chromatography to be visualized using ultraviolet or blue light. hfYFP and LSSmGFP represent a new generation of robustly stable fluorescent proteins developed for advanced biotechnological applications.
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9
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Tam C, Zhang KYJ. FPredX: Interpretable models for the prediction of spectral maxima, brightness, and oligomeric states of fluorescent proteins. Proteins 2021; 90:732-746. [PMID: 34676905 DOI: 10.1002/prot.26270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 09/19/2021] [Accepted: 10/15/2021] [Indexed: 11/06/2022]
Abstract
Fluorescent protein (FP) design is among the challenging protein design problems due to the tradeoffs among multiple properties to be optimized. Despite the accumulated efforts in design and characterization, progress has been slow in gaining a full understanding of sequence-property relationships to tackle the multiobjective design problem in FPs. In this study, we approach this problem by developing FPredX, a collection of gradient-boosted decision tree models, which mapped FP sequences to four major design targets of FPs, including excitation maximum, emission maximum, brightness, and oligomeric state. By training using one-hot encoded multiple aligned sequences with hyperparameters optimization in each model, FPredX models showed excellent prediction performance for all target properties compared with existing methods. We further interpreted the FPredX models by comparing the importance of positions along the aligned FP sequence to the predictive performance and suggested positions, which showed differential importance deemed by FPredX models to the prediction of each target property.
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Affiliation(s)
- Chunlai Tam
- Laboratory for Structural Bioinformatics, Center for Biosystems Dynamics Research, RIKEN, Yokohama, Japan.,Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Kam Y J Zhang
- Laboratory for Structural Bioinformatics, Center for Biosystems Dynamics Research, RIKEN, Yokohama, Japan.,Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
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10
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Scholz L, Neugebauer J. Protein Response Effects on Cofactor Excitation Energies from First Principles: Augmenting Subsystem Time-Dependent Density-Functional Theory with Many-Body Expansion Techniques. J Chem Theory Comput 2021; 17:6105-6121. [PMID: 34524815 DOI: 10.1021/acs.jctc.1c00551] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
We investigate the possibility of describing protein response effects on a chromophore excitation by means of subsystem time-dependent density-functional theory (sTDDFT) in combination with a many-body expansion (MBE) approach. While sTDDFT is in principle intrinsically able to include such contributions, addressing cofactor excitations in protein models or entire proteins with full environment-response treatments is currently out of reach. Taking different model structures of the green fluorescent protein (GFP) and bovine rhodopsin as examples, we demonstrate that an embedded-MBE approach based on sTDDFT in its simplest version leads to a good agreement of the predicted protein response effect already at second order. To reproduce reference response effects from nonsubsystem TDDFT calculations quantitatively (error ≤ 5%), however, a third- or even fourth-order MBE may be required. For the latter case, we explore a selective inclusion of fourth-order terms that drastically reduces the computational burden. In addition, we demonstrate how this sTDDFT-MBE treatment can be utilized as an analysis tool to identify residues with dominant response contributions. This, in turn, can be employed to arrive at smaller structural models for light-absorbing proteins, which still feature all of the main characteristics in terms of photoresponse properties.
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Affiliation(s)
- Linus Scholz
- Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Computation, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
| | - Johannes Neugebauer
- Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Computation, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
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11
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Müller-Schüssele SJ, Schwarzländer M, Meyer AJ. Live monitoring of plant redox and energy physiology with genetically encoded biosensors. PLANT PHYSIOLOGY 2021; 186:93-109. [PMID: 34623445 PMCID: PMC8154060 DOI: 10.1093/plphys/kiab019] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 01/07/2021] [Indexed: 05/03/2023]
Abstract
Genetically encoded biosensors pave the way for understanding plant redox dynamics and energy metabolism on cellular and subcellular levels.
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Affiliation(s)
- Stefanie J Müller-Schüssele
- Institute of Crop Science and Resource Conservation (INRES), University of Bonn, Friedrich-Ebert-Allee 144, D-53113 Bonn, Germany
| | - Markus Schwarzländer
- Institute of Plant Biology and Biotechnology, University of Münster, Schlossplatz 8, D-48143 Münster, Germany
| | - Andreas J Meyer
- Institute of Crop Science and Resource Conservation (INRES), University of Bonn, Friedrich-Ebert-Allee 144, D-53113 Bonn, Germany
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12
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Pletneva NV, Maksimov EG, Protasova EA, Mamontova AV, Simonyan TR, Ziganshin RH, Lukyanov KA, Muslinkina L, Pletnev S, Bogdanov AM, Pletnev VZ. Amino acid residue at the 165th position tunes EYFP chromophore maturation. A structure-based design. Comput Struct Biotechnol J 2021; 19:2950-2959. [PMID: 34136094 PMCID: PMC8163865 DOI: 10.1016/j.csbj.2021.05.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 05/06/2021] [Accepted: 05/09/2021] [Indexed: 01/07/2023] Open
Abstract
For the whole GFP family, a few cases, when a single mutation in the chromophore environment strongly inhibits maturation, were described. Here we study EYFP-F165G - a variant of the enhanced yellow fluorescent protein - obtained by a single F165G replacement, and demonstrated multiple fluorescent states represented by the minor emission peaks in blue and yellow ranges (~470 and ~530 nm), and the major peak at ~330 nm. The latter has been assigned to tryptophan fluorescence, quenched due to excitation energy transfer to the mature chromophore in the parental EYFP protein. EYFP-F165G crystal structure revealed two general independent routes of post-translational chemistry, resulting in two main states of the polypeptide chain with the intact chromophore forming triad (~85%) and mature chromophore (~15%). Our experiments thus highlighted important stereochemical role of the 165th position strongly affecting spectral characteristics of the protein. On the basis of the determined EYFP-F165G three-dimensional structure, new variants with ~ 2-fold improved brightness were engineered.
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Key Words
- Ala (A), alanine
- Arg (R), arginine
- Asn (R), asparagine
- Chromophore maturation
- DTT, dithiothreitol
- EC, extinction coefficient
- EET, excitation energy transfer
- EGFP, enhanced green fluorescent protein
- ESET, excited-state electron transfer
- EYFP
- EYFP, enhanced yellow fluorescent protein
- Excitation energy transfer
- FLIM, fluorescence lifetime imaging microscopy
- FP, fluorescent protein
- FQY, fluorescence quantum yield
- FRET, Förster resonance energy transfer
- FTIR, Fourier-transform infrared (spectroscopy
- Femtosecond spectroscopy
- Fluorescent proteins
- GFP, green fluorescent protein
- GYG, glycine-tyrosine-glycine
- Gln (Q), glutamine
- Glu (E), glutamic acid
- Gly (G), glycine
- His (H), histidine
- IVA-cloning, in vivo assembly cloning
- Leu (L), leucine
- PBS, phosphate buffered saline
- PCR, polymerase chain reaction
- Phe (F), phenylalanine
- REACh, resonance energy-accepting chromoprotein
- Ser (S), serine
- Structure-guided mutagenesis
- Trp (W), tryptophan
- Tryptophan fluorescence
- Tyr (Y), tyrosine
- Val (V), valine
- X-ray structure
- avGFP, Aequorea victoria green fluorescent protein
- sfGFP, superfolder GFP
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Affiliation(s)
- Nadya V. Pletneva
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow 117997, Russia
| | - Eugene G. Maksimov
- Faculty of Biology, Lomonosov Moscow State University, 119992 Moscow, Russia
| | - Elena A. Protasova
- Faculty of Biology, Lomonosov Moscow State University, 119992 Moscow, Russia
| | - Anastasia V. Mamontova
- Center of Life Sciences, Skolkovo Institute of Science and Technology, Moscow 121205, Russia
| | - Tatiana R. Simonyan
- Center of Life Sciences, Skolkovo Institute of Science and Technology, Moscow 121205, Russia
| | - Rustam H. Ziganshin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow 117997, Russia
| | - Konstantin A. Lukyanov
- Center of Life Sciences, Skolkovo Institute of Science and Technology, Moscow 121205, Russia
| | - Liya Muslinkina
- Structural Biology Section, Research Technologies Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Sergei Pletnev
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Alexey M. Bogdanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow 117997, Russia,Corresponding authors at: Depatment of biophotonics (both), Laboratory of genetically encoded molecular tools ( A.M.B.), Laboratory of of X-ray study ( V.Z.P.).
| | - Vladimir Z. Pletnev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow 117997, Russia,Corresponding authors at: Depatment of biophotonics (both), Laboratory of genetically encoded molecular tools ( A.M.B.), Laboratory of of X-ray study ( V.Z.P.).
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13
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Mechanism of ArcLight derived GEVIs involves electrostatic interactions that can affect proton wires. Biophys J 2021; 120:1916-1926. [PMID: 33744263 PMCID: PMC8204334 DOI: 10.1016/j.bpj.2021.03.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 02/28/2021] [Accepted: 03/10/2021] [Indexed: 11/24/2022] Open
Abstract
The genetically encoded voltage indicators ArcLight and its derivatives mediate voltage-dependent optical signals by intermolecular, electrostatic interactions between neighboring fluorescent proteins (FPs). A random mutagenesis event placed a negative charge on the exterior of the FP, resulting in a greater than 10-fold improvement of the voltage-dependent optical signal. Repositioning this negative charge on the exterior of the FP reversed the polarity of voltage-dependent optical signals, suggesting the presence of “hot spots” capable of interacting with the negative charge on a neighboring FP, thereby changing the fluorescent output. To explore the potential effect on the chromophore state, voltage-clamp fluorometry was performed with alternating excitation at 390 nm followed by excitation at 470 nm, resulting in several mutants exhibiting voltage-dependent, ratiometric optical signals of opposing polarities. However, the kinetics, voltage ranges, and optimal FP fusion sites were different depending on the wavelength of excitation. These results suggest that the FP has external, electrostatic pathways capable of quenching fluorescence that are wavelength specific. One mutation to the FP (E222H) showed a voltage-dependent increase in fluorescence when excited at 390 nm, indicating the ability to affect the proton wire from the protonated chromophore to the H222 position. ArcLight-derived sensors may therefore offer a novel way to map how conditions external to the β-can structure can affect the fluorescence of the chromophore and transiently affect those pathways via conformational changes mediated by manipulating membrane potential.
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14
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Dhamija S, De AK. Elucidating Contributions from Multiple Species during Photoconversion of Enhanced Green Fluorescent Protein (EGFP) under Ultraviolet Illumination. Photochem Photobiol 2021; 97:980-990. [PMID: 33624317 DOI: 10.1111/php.13409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 02/21/2021] [Indexed: 11/30/2022]
Abstract
Photocycle in wild-type green fluorescent protein (wt-GFP) involves generation of a bright fluorescent deprotonated chromophore from feebly fluorescent protonated form via excited-state proton transfer. In addition to this usual photocycle, wt-GFP is also known to exhibit irreversible photoconversion upon illumination with ultraviolet and visible radiation. However, a detailed understanding of photoconversion in enhanced GFP (EGFP: S65T/F64L mutant of wt-GFP), which predominantly exists in deprotonated form, is yet to be explored. Using 254 nm irradiation, we study how photoconversion proceeds in EGFP. The key findings are observation of spreading out of an isosbestic point and existence of an initial lag phase in spectral kinetics of absorbance, indicative of sequential photoconversion through an intermediate. Fluorescence kinetics of EGFP and its photoproduct are estimated by assigning two unique fluorescence lifetimes which is further complicated by the fact that their fluorescence are spectrally inseparable, as evident from global analysis of fluorescence lifetime. Time-resolved fluorescence anisotropy studies further suggest minimal structural changes in protein scaffold upon photoconversion. Based on these findings, an analytic model is developed to account for the overall decay in fluorescence (as photoconversion proceeds) that inherently incorporates the initial lag phase and a summary of energetics and processes involved is provided.
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Affiliation(s)
- Shaina Dhamija
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, SAS Nagar, Punjab, India
| | - Arijit K De
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, SAS Nagar, Punjab, India
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15
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Antonescu ON, Rasmussen A, Damm NAM, Heidemann DF, Popov R, Nesterov-Mueller A, Johansson KE, Winther JR. Substitutional landscape of a split fluorescent protein fragment using high-density peptide microarrays. PLoS One 2021; 16:e0241461. [PMID: 33534832 PMCID: PMC7857580 DOI: 10.1371/journal.pone.0241461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 12/21/2020] [Indexed: 11/23/2022] Open
Abstract
Split fluorescent proteins have wide applicability as biosensors for protein-protein interactions, genetically encoded tags for protein detection and localization, as well as fusion partners in super-resolution microscopy. We have here established and validated a novel platform for functional analysis of leave-one-out split fluorescent proteins (LOO-FPs) in high throughput and with rapid turnover. We have screened more than 12,000 variants of the beta-strand split fragment using high-density peptide microarrays for binding and functional complementation in Green Fluorescent Protein. We studied the effect of peptide length and the effect of different linkers to the solid support. We further mapped the effect of all possible amino acid substitutions on each position as well as in the context of some single and double amino acid substitutions. As all peptides were tested in 12 duplicates, the analysis rests on a firm statistical basis allowing for confirmation of the robustness and precision of the method. Based on experiments in solution, we conclude that under the given conditions, the signal intensity on the peptide microarray faithfully reflects the binding affinity between the split fragments. With this, we are able to identify a peptide with 9-fold higher affinity than the starting peptide.
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Affiliation(s)
- Oana N. Antonescu
- Department of Biology, Linderstrøm-Lang Centre for Protein Science, Section for Biomolecular Sciences, University for Copenhagen, Copenhagen, Denmark
| | - Andreas Rasmussen
- Department of Biology, Linderstrøm-Lang Centre for Protein Science, Section for Biomolecular Sciences, University for Copenhagen, Copenhagen, Denmark
| | - Nicole A. M. Damm
- Department of Biology, Linderstrøm-Lang Centre for Protein Science, Section for Biomolecular Sciences, University for Copenhagen, Copenhagen, Denmark
| | - Ditte F. Heidemann
- Department of Biology, Linderstrøm-Lang Centre for Protein Science, Section for Biomolecular Sciences, University for Copenhagen, Copenhagen, Denmark
| | - Roman Popov
- Institute of Microstructure Technology, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany
| | - Alexander Nesterov-Mueller
- Institute of Microstructure Technology, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany
| | - Kristoffer E. Johansson
- Department of Biology, Linderstrøm-Lang Centre for Protein Science, Section for Biomolecular Sciences, University for Copenhagen, Copenhagen, Denmark
| | - Jakob R. Winther
- Department of Biology, Linderstrøm-Lang Centre for Protein Science, Section for Biomolecular Sciences, University for Copenhagen, Copenhagen, Denmark
- * E-mail:
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16
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Drobizhev M, Molina RS, Callis PR, Scott JN, Lambert GG, Salih A, Shaner NC, Hughes TE. Local Electric Field Controls Fluorescence Quantum Yield of Red and Far-Red Fluorescent Proteins. Front Mol Biosci 2021; 8:633217. [PMID: 33763453 PMCID: PMC7983054 DOI: 10.3389/fmolb.2021.633217] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 01/06/2021] [Indexed: 12/17/2022] Open
Abstract
Genetically encoded probes with red-shifted absorption and fluorescence are highly desirable for imaging applications because they can report from deeper tissue layers with lower background and because they provide additional colors for multicolor imaging. Unfortunately, red and especially far-red fluorescent proteins have very low quantum yields, which undermines their other advantages. Elucidating the mechanism of nonradiative relaxation in red fluorescent proteins (RFPs) could help developing ones with higher quantum yields. Here we consider two possible mechanisms of fast nonradiative relaxation of electronic excitation in RFPs. The first, known as the energy gap law, predicts a steep exponential drop of fluorescence quantum yield with a systematic red shift of fluorescence frequency. In this case the relaxation of excitation occurs in the chromophore without any significant changes of its geometry. The second mechanism is related to a twisted intramolecular charge transfer in the excited state, followed by an ultrafast internal conversion. The chromophore twisting can strongly depend on the local electric field because the field can affect the activation energy. We present a spectroscopic method of evaluating local electric fields experienced by the chromophore in the protein environment. The method is based on linear and two-photon absorption spectroscopy, as well as on quantum-mechanically calculated parameters of the isolated chromophore. Using this method, which is substantiated by our molecular dynamics simulations, we obtain the components of electric field in the chromophore plane for seven different RFPs with the same chromophore structure. We find that in five of these RFPs, the nonradiative relaxation rate increases with the strength of the field along the chromophore axis directed from the center of imidazolinone ring to the center of phenolate ring. Furthermore, this rate depends on the corresponding electrostatic energy change (calculated from the known fields and charge displacements), in quantitative agreement with the Marcus theory of charge transfer. This result supports the dominant role of the twisted intramolecular charge transfer mechanism over the energy gap law for most of the studied RFPs. It provides important guidelines of how to shift the absorption wavelength of an RFP to the red, while keeping its brightness reasonably high.
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Affiliation(s)
- Mikhail Drobizhev
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT, United States
| | - Rosana S Molina
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT, United States
| | - Patrik R Callis
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, United States
| | | | - Gerard G Lambert
- Department of Neurosciences, UC San Diego, San Diego, CA, United States
| | - Anya Salih
- Antares & Fluoresci Research, Dangar Island, NSW, Australia
| | - Nathan C Shaner
- Department of Neurosciences, UC San Diego, San Diego, CA, United States
| | - Thomas E Hughes
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT, United States
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17
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Schneider F, Sych T, Eggeling C, Sezgin E. Influence of nanobody binding on fluorescence emission, mobility, and organization of GFP-tagged proteins. iScience 2021; 24:101891. [PMID: 33364580 PMCID: PMC7753935 DOI: 10.1016/j.isci.2020.101891] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 11/02/2020] [Accepted: 12/01/2020] [Indexed: 12/22/2022] Open
Abstract
Advanced fluorescence microscopy studies require specific and monovalent molecular labeling with bright and photostable fluorophores. This necessity led to the widespread use of fluorescently labeled nanobodies against commonly employed fluorescent proteins (FPs). However, very little is known how these nanobodies influence their target molecules. Here, we tested commercially available nanobodies and observed clear changes of the fluorescence properties, mobility and organization of green fluorescent protein (GFP) tagged proteins after labeling with the anti-GFP nanobody. Intriguingly, we did not observe any co-diffusion of fluorescently labeled nanobodies with the GFP-labeled proteins. Our results suggest significant binding of the nanobodies to a non-emissive, likely oligomerized, form of the FPs, promoting disassembly into monomeric form after binding. Our findings have significant implications on the application of nanobodies and GFP labeling for studying dynamic and quantitative protein organization in the plasma membrane of living cells using advanced imaging techniques.
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Affiliation(s)
- Falk Schneider
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
| | - Taras Sych
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, 171 65 Solna, Sweden
| | - Christian Eggeling
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
- Institute of Applied Optics and Biophysics, Friedrich-Schiller-University Jena, Max-Wien Platz 4, 07743 Jena, Germany
- Leibniz Institute of Photonic Technology e.V., Albert-Einstein-Straße 9, 07745 Jena, Germany
- Jena Center of Soft Matters, Friedrich-Schiller-University Jena, Philosophenweg 7, 07743 Jena, Germany
| | - Erdinc Sezgin
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, 171 65 Solna, Sweden
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18
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Coppola F, Perrella F, Petrone A, Donati G, Rega N. A Not Obvious Correlation Between the Structure of Green Fluorescent Protein Chromophore Pocket and Hydrogen Bond Dynamics: A Choreography From ab initio Molecular Dynamics. Front Mol Biosci 2020; 7:569990. [PMID: 33195416 PMCID: PMC7653547 DOI: 10.3389/fmolb.2020.569990] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 09/11/2020] [Indexed: 11/23/2022] Open
Abstract
The Green Fluorescent Protein (GFP) is a widely studied chemical system both for its large amount of applications and the complexity of the excited state proton transfer responsible of the change in the protonation state of the chromophore. A detailed investigation on the structure of the chromophore environment and the influence of chromophore form (either neutral or anionic) on it is of crucial importance to understand how these factors could potentially influence the protein function. In this study, we perform a detailed computational investigation based on the analysis of ab-initio molecular dynamics simulations, to disentangle the main structural quantities determining the fine balance in the chromophore environment. We found that specific hydrogen bonds interactions directly involving the chromophore (or not), are correlated to quantities, such as the volume of the cavity in which the chromophore is embedded and that it is importantly affected by the chromophore protonation state. The cross-correlation analysis performed on some of these hydrogen bonds and the cavity volume, demonstrates a direct correlation among them and we also identified the ones specifically involved in this correlation. We also found that specific interactions among residues far in the space are correlated, demonstrating the complexity of the chromophore environment and that many structural quantities have to be taken into account to properly describe and understand the main factors tuning the active site of the protein. From an overall evaluation of the results obtained in this work, it is shown that the residues which a priori are perceived to be spectators play instead an important role in both influencing the chromophore environment (cavity volume) and its dynamics (cross-correlations among spatially distant residues).
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Affiliation(s)
- Federico Coppola
- Department of Chemical Sciences, University of Naples Federico II, Naples, Italy
| | - Fulvio Perrella
- Department of Chemical Sciences, University of Naples Federico II, Naples, Italy
| | - Alessio Petrone
- Department of Chemical Sciences, University of Naples Federico II, Naples, Italy
| | - Greta Donati
- Department of Chemical Sciences, University of Naples Federico II, Naples, Italy
| | - Nadia Rega
- Department of Chemical Sciences, University of Naples Federico II, Naples, Italy.,Center for Advanced Biomaterials for Healthcare@CRIB, Naples, Italy
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19
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Jin X, Glover WJ, He X. Fragment Quantum Mechanical Method for Excited States of Proteins: Development and Application to the Green Fluorescent Protein. J Chem Theory Comput 2020; 16:5174-5188. [PMID: 32551640 DOI: 10.1021/acs.jctc.9b00980] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Understanding the excited-state properties of luminescent biomolecules is of central importance to their biophysical applications. In this study, we develop the Electrostatically Embedded Generalized Molecular Fractionation with Conjugate Caps (EE-GMFCC) method for quantitatively characterizing properties of covalently bonded systems with localized excitations (i.e., involving a single chromophore), such as fluorescent proteins. The excitation energy, transition dipole moment, and oscillator strength of wild-type Green Fluorescent Protein (wt-GFP) calculated by EE-GMFCC are found to be in excellent agreement with full system time-dependent density functional theory results. We also applied the Polarized Protein-Specific Charge model to wt-GFP, and found that electronic polarization of the protein is critical in stabilizing hydrogen bonding interactions in wt-GFP, which influences its absorption spectrum. The predicted absorption spectra of wt-GFP in the A and B states qualitatively agree with experiment. The fragmentation approach further allows a straightforward per residue decomposition of the excitation which reveals the influence of the protein environment on the absorption spectra of wt-GFP A and B states. Our results demonstrate that the EE-GMFCC method is both accurate and efficient for excited-state property calculations on proteins.
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Affiliation(s)
- Xinsheng Jin
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - William J Glover
- NYU Shanghai, 1555 Century Avenue, Shanghai 200122, China.,NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai 200062, China.,Department of Chemistry, New York University, New York, New York 10003, United States
| | - Xiao He
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China.,NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai 200062, China
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20
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Rodriguez-Alvarez M, Kim D, Khobta A. EGFP Reporters for Direct and Sensitive Detection of Mutagenic Bypass of DNA Lesions. Biomolecules 2020; 10:biom10060902. [PMID: 32545792 PMCID: PMC7357151 DOI: 10.3390/biom10060902] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 06/05/2020] [Accepted: 06/10/2020] [Indexed: 02/06/2023] Open
Abstract
The sustainment of replication and transcription of damaged DNA is essential for cell survival under genotoxic stress; however, the damage tolerance of these key cellular functions comes at the expense of fidelity. Thus, translesion DNA synthesis (TLS) over damaged nucleotides is a major source of point mutations found in cancers; whereas erroneous bypass of damage by RNA polymerases may contribute to cancer and other diseases by driving accumulation of proteins with aberrant structure and function in a process termed “transcriptional mutagenesis” (TM). Here, we aimed at the generation of reporters suited for direct detection of miscoding capacities of defined types of DNA modifications during translesion DNA or RNA synthesis in human cells. We performed a systematic phenotypic screen of 25 non-synonymous base substitutions in a DNA sequence encoding a functionally important region of the enhanced green fluorescent protein (EGFP). This led to the identification of four loss-of-fluorescence mutants, in which any ulterior base substitution at the nucleotide affected by the primary mutation leads to the reversal to a functional EGFP. Finally, we incorporated highly mutagenic abasic DNA lesions at the positions of primary mutations and demonstrated a high sensitivity of detection of the mutagenic DNA TLS and TM in this system.
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Affiliation(s)
- Marta Rodriguez-Alvarez
- Unit “Responses to DNA Lesions", Institute of Toxicology, University Medical Center of the Johannes Gutenberg University Mainz, Obere Zahlbacher Str. 67, 55131 Mainz, Germany;
| | - Daria Kim
- Novosibirsk State University, 1 Pirogova St., 630090 Novosibirsk, Russia;
- Laboratory of Genome and Protein Engineering, SB RAS Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Ave., 630090 Novosibirsk, Russia
| | - Andriy Khobta
- Unit “Responses to DNA Lesions", Institute of Toxicology, University Medical Center of the Johannes Gutenberg University Mainz, Obere Zahlbacher Str. 67, 55131 Mainz, Germany;
- Correspondence:
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21
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Lin CY, Boxer SG. Mechanism of Color and Photoacidity Tuning for the Protonated Green Fluorescent Protein Chromophore. J Am Chem Soc 2020; 142:11032-11041. [PMID: 32453950 DOI: 10.1021/jacs.0c02796] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The neutral or A state of the green fluorescent protein (GFP) chromophore is a remarkable example of a photoacid naturally embedded in the protein environment and accounts for the large Stokes shift of GFP in response to near UV excitation. Its color tuning mechanism has been largely overlooked, as it is less preferred for imaging applications than the redder anionic or B state. Past studies, based on site-directed mutagenesis or solvatochromism of the isolated chromophore, have concluded that its color tuning range is much narrower than its anionic counterpart. However, as we performed extensive investigation on more GFP mutants, we found that the color of the neutral chromophore can be more sensitive to protein electrostatics than can the anionic counterpart. Electronic Stark spectroscopy reveals a fundamentally different electrostatic color tuning mechanism for the neutral state of the chromophore that demands a three-form model as compared to that of the anionic state, which requires only two forms ( J. Am. Chem. Soc. 2019, 141, 15250-15265). Specifically, an underlying zwitterionic charge-transfer state is required to explain its sensitivity to electrostatics. As the Stokes shift is tightly linked to excited-state proton transfer (ESPT) of the protonated chromophore, we infer design principles of the GFP chromophore as a photoacid through the color tuning mechanisms of both protonation states. The three-form model could also be applied to similar biological and nonbiological dyes and complements the failure of the two-form model for donor-acceptor systems with localized ground-state electronic distributions.
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Affiliation(s)
- Chi-Yun Lin
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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22
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Barykina NV, Sotskov VP, Gruzdeva AM, Wu YK, Portugues R, Subach OM, Chefanova ES, Plusnin VV, Ivashkina OI, Anokhin KV, Vlaskina AV, Korzhenevskiy DA, Nikolaeva AY, Boyko KM, Rakitina TV, Varizhuk AM, Pozmogova GE, Subach FV. FGCaMP7, an Improved Version of Fungi-Based Ratiometric Calcium Indicator for In Vivo Visualization of Neuronal Activity. Int J Mol Sci 2020; 21:ijms21083012. [PMID: 32344594 PMCID: PMC7215472 DOI: 10.3390/ijms21083012] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2020] [Revised: 04/22/2020] [Accepted: 04/23/2020] [Indexed: 01/06/2023] Open
Abstract
Genetically encoded calcium indicators (GECIs) have become a widespread tool for the visualization of neuronal activity. As compared to popular GCaMP GECIs, the FGCaMP indicator benefits from calmodulin and M13-peptide from the fungi Aspergillus niger and Aspergillus fumigatus, which prevent its interaction with the intracellular environment. However, FGCaMP exhibits a two-phase fluorescence behavior with the variation of calcium ion concentration, has moderate sensitivity in neurons (as compared to the GCaMP6s indicator), and has not been fully characterized in vitro and in vivo. To address these limitations, we developed an enhanced version of FGCaMP, called FGCaMP7. FGCaMP7 preserves the ratiometric phenotype of FGCaMP, with a 3.1-fold larger ratiometric dynamic range in vitro. FGCaMP7 demonstrates 2.7- and 8.7-fold greater photostability compared to mEGFP and mTagBFP2 fluorescent proteins in vitro, respectively. The ratiometric response of FGCaMP7 is 1.6- and 1.4-fold higher, compared to the intensiometric response of GCaMP6s, in non-stimulated and stimulated neuronal cultures, respectively. We reveal the inertness of FGCaMP7 to the intracellular environment of HeLa cells using its truncated version with a deleted M13-like peptide; in contrast to the similarly truncated variant of GCaMP6s. We characterize the crystal structure of the parental FGCaMP indicator. Finally, we test the in vivo performance of FGCaMP7 in mouse brain using a two-photon microscope and an NVista miniscope; and in zebrafish using two-color ratiometric confocal imaging.
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Affiliation(s)
- Natalia V. Barykina
- Laboratory for Neurobiology of Memory, P.K. Anokhin Research Institute of Normal Physiology, 125315 Moscow, Russia; (N.V.B.); (O.I.I.); (K.V.A.)
| | - Vladimir P. Sotskov
- Institute for Advanced Brain Studies, M.V. Lomonosov Moscow State University, 119991 Moscow, Russia; (V.P.S.); (A.M.G.)
| | - Anna M. Gruzdeva
- Institute for Advanced Brain Studies, M.V. Lomonosov Moscow State University, 119991 Moscow, Russia; (V.P.S.); (A.M.G.)
- Complex of NBICS Technologies, National Research Center “Kurchatov Institute”, 123182 Moscow, Russia; (O.M.S.); (V.V.P.); (A.V.V.); (D.A.K.); (A.Y.N.); (T.V.R.)
- Sensorimotor Control Research Group, Max Planck Institute of Neurobiology, 82152 Martinsried, Germany; (Y.K.W.); (R.P.)
| | - You Kure Wu
- Sensorimotor Control Research Group, Max Planck Institute of Neurobiology, 82152 Martinsried, Germany; (Y.K.W.); (R.P.)
| | - Ruben Portugues
- Sensorimotor Control Research Group, Max Planck Institute of Neurobiology, 82152 Martinsried, Germany; (Y.K.W.); (R.P.)
- Institute of Neuroscience, Technical University of Munich, 80802 Munich, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Oksana M. Subach
- Complex of NBICS Technologies, National Research Center “Kurchatov Institute”, 123182 Moscow, Russia; (O.M.S.); (V.V.P.); (A.V.V.); (D.A.K.); (A.Y.N.); (T.V.R.)
| | - Elizaveta S. Chefanova
- Department of NBIC-technologies, Moscow Institute of Physics and Technology, 123182 Moscow, Russia;
| | - Viktor V. Plusnin
- Complex of NBICS Technologies, National Research Center “Kurchatov Institute”, 123182 Moscow, Russia; (O.M.S.); (V.V.P.); (A.V.V.); (D.A.K.); (A.Y.N.); (T.V.R.)
- Department of NBIC-technologies, Moscow Institute of Physics and Technology, 123182 Moscow, Russia;
| | - Olga I. Ivashkina
- Laboratory for Neurobiology of Memory, P.K. Anokhin Research Institute of Normal Physiology, 125315 Moscow, Russia; (N.V.B.); (O.I.I.); (K.V.A.)
- Institute for Advanced Brain Studies, M.V. Lomonosov Moscow State University, 119991 Moscow, Russia; (V.P.S.); (A.M.G.)
- Complex of NBICS Technologies, National Research Center “Kurchatov Institute”, 123182 Moscow, Russia; (O.M.S.); (V.V.P.); (A.V.V.); (D.A.K.); (A.Y.N.); (T.V.R.)
| | - Konstantin V. Anokhin
- Laboratory for Neurobiology of Memory, P.K. Anokhin Research Institute of Normal Physiology, 125315 Moscow, Russia; (N.V.B.); (O.I.I.); (K.V.A.)
- Institute for Advanced Brain Studies, M.V. Lomonosov Moscow State University, 119991 Moscow, Russia; (V.P.S.); (A.M.G.)
| | - Anna V. Vlaskina
- Complex of NBICS Technologies, National Research Center “Kurchatov Institute”, 123182 Moscow, Russia; (O.M.S.); (V.V.P.); (A.V.V.); (D.A.K.); (A.Y.N.); (T.V.R.)
| | - Dmitry A. Korzhenevskiy
- Complex of NBICS Technologies, National Research Center “Kurchatov Institute”, 123182 Moscow, Russia; (O.M.S.); (V.V.P.); (A.V.V.); (D.A.K.); (A.Y.N.); (T.V.R.)
| | - Alena Y. Nikolaeva
- Complex of NBICS Technologies, National Research Center “Kurchatov Institute”, 123182 Moscow, Russia; (O.M.S.); (V.V.P.); (A.V.V.); (D.A.K.); (A.Y.N.); (T.V.R.)
| | - Konstantin M. Boyko
- Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, 119071 Moscow, Russia;
| | - Tatiana V. Rakitina
- Complex of NBICS Technologies, National Research Center “Kurchatov Institute”, 123182 Moscow, Russia; (O.M.S.); (V.V.P.); (A.V.V.); (D.A.K.); (A.Y.N.); (T.V.R.)
- Laboratory of Hormonal Regulation Proteins, M.M. Shemyakin and Yu.A. Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, 117997 Moscow, Russia
| | - Anna M. Varizhuk
- Department of Biophysics, Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, 119435 Moscow, Russia; (A.M.V.); (G.E.P.)
- Department of Biophysics, Center for Precision Genome Editing and Genetic Technologies for Biomedicine, 119435 Moscow, Russia
| | - Galina E. Pozmogova
- Department of Biophysics, Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, 119435 Moscow, Russia; (A.M.V.); (G.E.P.)
- Department of Biophysics, Center for Precision Genome Editing and Genetic Technologies for Biomedicine, 119435 Moscow, Russia
| | - Fedor V. Subach
- Complex of NBICS Technologies, National Research Center “Kurchatov Institute”, 123182 Moscow, Russia; (O.M.S.); (V.V.P.); (A.V.V.); (D.A.K.); (A.Y.N.); (T.V.R.)
- Correspondence: ; Tel.: +07-499-196-7100-3389
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23
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Romei MG, Lin CY, Mathews II, Boxer SG. Electrostatic control of photoisomerization pathways in proteins. Science 2020; 367:76-79. [PMID: 31896714 DOI: 10.1126/science.aax1898] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 06/04/2019] [Accepted: 10/31/2019] [Indexed: 12/23/2022]
Abstract
Rotation around a specific bond after photoexcitation is central to vision and emerging opportunities in optogenetics, super-resolution microscopy, and photoactive molecular devices. Competing roles for steric and electrostatic effects that govern bond-specific photoisomerization have been widely discussed, the latter originating from chromophore charge transfer upon excitation. We systematically altered the electrostatic properties of the green fluorescent protein chromophore in a photoswitchable variant, Dronpa2, using amber suppression to introduce electron-donating and electron-withdrawing groups to the phenolate ring. Through analysis of the absorption (color), fluorescence quantum yield, and energy barriers to ground- and excited-state isomerization, we evaluate the contributions of sterics and electrostatics quantitatively and demonstrate how electrostatic effects bias the pathway of chromophore photoisomerization, leading to a generalized framework to guide protein design.
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Affiliation(s)
- Matthew G Romei
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA.
| | - Chi-Yun Lin
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA.
| | - Irimpan I Mathews
- Stanford Synchrotron Radiation Lightsource, Menlo Park, CA 94025, USA
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
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24
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Unzueta U, Roldán M, Pesarrodona M, Benitez R, Sánchez-Chardi A, Conchillo-Solé O, Mangues R, Villaverde A, Vázquez E. Self-assembling as regular nanoparticles dramatically minimizes photobleaching of tumour-targeted GFP. Acta Biomater 2020; 103:272-280. [PMID: 31812843 DOI: 10.1016/j.actbio.2019.12.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 11/29/2019] [Accepted: 12/03/2019] [Indexed: 11/25/2022]
Abstract
Fluorescent proteins are useful imaging and theranostic agents, but their potential superiority over alternative dyes is weakened by substantial photobleaching under irradiation. Enhancing protein photostability has been attempted through diverse strategies, with irregular results and limited applicability. In this context, we wondered if the controlled oligomerization of Green Fluorescent Protein (GFP) as nanoscale supramolecular complexes could stabilize the fluorophore through the newly formed protein-protein contacts, and thus, enhance its global photostability. For that, we have here analyzed the photobleaching profile of several GFP versions, engineered to self-assemble as tumour-homing nanoparticles with different targeting, size and structural stability. This has been done under prolonged irradiation in confocal laser scanning microscopy and by small-angle X-ray scattering. The results show that the oligomerization of GFP at the nanoscale enhances, by more than seven-fold, the stability of fluorescence emission. Interestingly, GFP nanoparticles are much more resistant to X-ray damage than the building block counterparts, indicating that the gained photostability is linked to enhanced structural resistance to radiation. Therefore, the controlled oligomerization of self-assembling fluorescent proteins as protein nanoparticles is a simple, versatile and powerful method to enhance their photostability for uses in precision imaging and therapy. STATEMENT OF SIGNIFICANCE: Fluorescent protein assembly into regular and highly symmetric nanoscale structures has been identified to confer enhanced structural stability against radiation stresses dramatically reducing their photobleaching. Being this the main bottleneck in the use of fluorescent proteins for imaging and theranostics, this protein architecture engineering principle appears as a powerful method to enhance their photostability for a broad applicability in precision imaging, drug delivery and theranostics.
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25
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York EM, Weilinger NL, LeDue JM, MacVicar BA. Green fluorescent protein emission obscures metabolic fluorescent lifetime imaging of NAD(P)H. BIOMEDICAL OPTICS EXPRESS 2019; 10:4381-4394. [PMID: 31565496 PMCID: PMC6757450 DOI: 10.1364/boe.10.004381] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 05/10/2019] [Accepted: 05/17/2019] [Indexed: 05/23/2023]
Abstract
Autofluorescence of endogenous molecules can provide valuable insights in both basic research and clinical applications. One such technique is fluorescence lifetime imaging (FLIM) of NAD(P)H, which serves as a correlate of glycolysis and electron transport chain rates in metabolically active tissue. A powerful advantage of NAD(P)H-FLIM is the ability to measure cell-specific metabolism within heterogeneous tissues. Cell-type specific identification is most commonly achieved with directed green fluorescent protein (GFP) expression. However, we demonstrate that NAD(P)H-FLIM should not be analyzed in GFP-expressing cells, as GFP molecules themselves emit photons in the blue spectrum with short fluorescence lifetimes when imaged using two-photon excitation at 750 nm. This is substantially different from the reported GFP emission wavelength and lifetime after two-photon excitation at 910 nm. These blue GFP photons are indistinguishable from free NAD(P)H by both emission spectra and fluorescence lifetime. Therefore, NAD(P)H-FLIM in GFP-expressing cells will lead to incorrect interpretations of metabolic rates, and thus, these techniques should not be combined.
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Affiliation(s)
- Elisa M York
- Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, British Columbia, Canada
| | - Nicholas L Weilinger
- Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, British Columbia, Canada
| | - Jeffrey M LeDue
- Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, British Columbia, Canada
| | - Brian A MacVicar
- Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, British Columbia, Canada
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26
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Iachina I, Brewer JR. Strain-Dependent Structural Changes in Major and Minor Ampullate Spider Silk Revealed by Two-Photon Excitation Polarization. Biomacromolecules 2019; 20:2384-2391. [PMID: 31074979 DOI: 10.1021/acs.biomac.9b00368] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Spider silk's mechanical properties make it an interesting material for many industrial applications. The structure and nanoscopic organization of its proteins are the basis of these qualities. In this study, the emission maxima of the autofluorescence from the protein core of major and minor ampullate silk fibers from the orb-web-weaving spider Nephila madagascariensis are determined and found to be 534 ± 11 and 547 ± 19 nm, respectively. Molecular conformational changes during applied strain are observed in both fiber types using two-photon excitation polarization measurements. Our findings showed that within the fibers the autofluorescent dipoles are separated into two distinct populations, one randomly orientated (amorphous regions) and one with aligned dipoles as found in crystalline structures. The crystalline-amorphous ratio was determined, and it was found that the crystalline dipoles made up around 30 and 20% of the autofluorescent dipoles in major and minor ampullate silk fibers, respectively. Using two-photon polarization measurements, it is possible to directly observe that the major and minor ampullate silk fibers structurally adapt to the applied stress, as well as discern different molecular conformational changes between major and minor ampullates. It was seen that the crystalline-amorphous ratio increased, with up to 9% for major fibers and 6% for minor fibers, as strain was applied, suggesting a conformational adaptation of the fiber, interpreted as noncrystalline 310-helices transforming into crystalline β-sheets.
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Affiliation(s)
- Irina Iachina
- Department of Biochemistry and Molecular Biology , University of Southern Denmark , 5230 Odense , Denmark
| | - Jonathan R Brewer
- Department of Biochemistry and Molecular Biology , University of Southern Denmark , 5230 Odense , Denmark
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27
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Schramm S, Weiß D. Fluorescent heterocycles: Recent trends and new developments. ADVANCES IN HETEROCYCLIC CHEMISTRY 2019. [DOI: 10.1016/bs.aihch.2018.10.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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28
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Spectral and structural analysis of large Stokes shift fluorescent protein dKeima570. J Microbiol 2018; 56:822-827. [DOI: 10.1007/s12275-018-8319-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Revised: 07/16/2018] [Accepted: 07/18/2018] [Indexed: 02/05/2023]
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29
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Liu B, Mavrova SN, van den Berg J, Kristensen SK, Mantovanelli L, Veenhoff LM, Poolman B, Boersma AJ. Influence of Fluorescent Protein Maturation on FRET Measurements in Living Cells. ACS Sens 2018; 3:1735-1742. [PMID: 30168711 PMCID: PMC6167724 DOI: 10.1021/acssensors.8b00473] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Förster resonance
energy transfer (FRET)-based sensors are
a valuable tool to quantify cell biology, yet it remains necessary
to identify and prevent potential artifacts in order to exploit their
full potential. We show here that artifacts arising from slow donor
mCerulean3 maturation can be substantially diminished by constitutive
expression in both prokaryotic and eukaryotic cells, which can also
be achieved by incorporation of faster-maturing FRET donors. We developed
an improved version of the donor mTurquoise2 that matures faster than
the parent protein. Our analysis shows that using equal maturing fluorophores
in FRET-based sensors or using constitutive low expression conditions
helps to reduce maturation-induced artifacts, without the need of
additional noise-inducing spectral corrections. In general, we show
that monitoring and controlling the maturation of fluorescent proteins
in living cells is important and should be addressed in in
vivo applications of genetically encoded FRET sensors.
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Affiliation(s)
- Boqun Liu
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Sara N. Mavrova
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Jonas van den Berg
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Sebastian K. Kristensen
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Luca Mantovanelli
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Liesbeth M. Veenhoff
- European Research Institute for the Biology of Ageing, University of Groningen, University
Medical Center Groningen, 9713 AV Groningen, The Netherlands
| | - Bert Poolman
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Arnold J. Boersma
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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30
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Kaur J, Yadav NS, Singh MK, Khan MJ, Sen S, Dixit A, Choudhury D. Role of Ser65, His148 and Thr203 in the Organic Solvent-dependent Spectral Shift in Green Fluorescent Protein. Photochem Photobiol 2018; 95:543-555. [PMID: 30240005 DOI: 10.1111/php.13018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 09/04/2018] [Indexed: 01/10/2023]
Abstract
The photophysics of green fluorescent protein (GFP) is remarkable because of its exceptional property of excited state proton transfer (ESPT) and the presence of a functional proton wire. Another interesting property of wild-type GFP is that its absorption and fluorescence excitation spectra are sensitive to the presence of polar organic solvents even at very low concentrations. Here, we use a combination of methodologies including site-specific mutagenesis, absorption spectroscopy, steady-state and time-resolved fluorescence measurements and all-atom molecular dynamics simulations in explicit solvent, to uncover the mechanism behind the unique spectral sensitivity of GFP toward organic solvents. Based on the evidences provided herein, we suggest that organic solvent-induced changes in the proton wire prevent ground state movement of a proton through the wire and thus bring about the spectral changes observed. The present study can not only help to understand the mechanism of proton transfer by further dissecting the intricate steps in GFP photophysics but also encourages to develop GFP-based organic solvent biosensors.
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Affiliation(s)
- Jasvir Kaur
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | - Neetu Singh Yadav
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | | | - Mohd Jahir Khan
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | - Sobhan Sen
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Aparna Dixit
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
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31
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Lolli G, Raboni S, Pasqualetto E, Benoni R, Campanini B, Ronda L, Mozzarelli A, Bettati S, Battistutta R. Insight into GFPmut2 pH Dependence by Single Crystal Microspectrophotometry and X-ray Crystallography. J Phys Chem B 2018; 122:11326-11337. [PMID: 30179482 DOI: 10.1021/acs.jpcb.8b07260] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The fluorescence of Green Fluorescent Protein (wtGFP) and variants has been exploited in distinct applications in cellular and analytical biology. GFPs emission depends on the population of the protonated (A-state) and deprotonated (B-state) forms of the chromophore. Whereas wtGFP is pH-independent, mutants in which Ser65 is replaced by either threonine or alanine (as in GFPmut2) are pH-dependent, with a p Ka around 6. Given the wtGFP pH-independence, only the structure of the protonated form was determined. The deprotonated form was deduced on the basis of the crystal structure of the Ser65Thr mutant at basic pH, assuming that it corresponds to the conformation populated in solution. Here, we present an investigation where structures of the protonated and deprotonated forms of GFPmut2 were determined from crystals grown in either MPD at pH 6 or PEG at pH 8.5, and moved to either higher or lower pH. Both crystal forms of GFPmut2 were titrated monitoring the process via polarized absorption microspectrophotometry in order to precisely correlate the protonation process with the structures. We found that (i) in solution, chromophore titration is not thermodynamically coupled with any residue and Glu222 is always protonated independent of the protonation state of the chromophore; (ii) the lack of coupling is reflected in the structural behavior of the chromophore and Glu222 environments, with only the former showing variations with pH; (iii) titrations of low-pH and high-pH grown crystals exhibit a Hill coefficient of about 0.75, indicating an anticooperative behavior not observed in solution; (iv) structures where pH was changed in the crystal point to Glu222 as the ionizable group responsible for the outset of the anticooperative behavior; and (v) in GFPmut2 the canonical GFP proton wire involving the chromophore is not interrupted at the level of Ser205 and Glu222 at basic pH as in the Ser65Thr mutant. This allows proposing the structure of the deprotonated state of GFPmut2 as an alternative model for the analogous state of wtGFP.
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Affiliation(s)
- Graziano Lolli
- Centro di Biologia Integrata - CIBIO , Università di Trento , 38123 Povo , Trento , Italy
| | - Samanta Raboni
- Dipartimento di Scienze degli Alimenti e del Farmaco , Università di Parma , 43124 Parma , Italy
| | - Elisa Pasqualetto
- Dipartimento di Scienze Chimiche , Università degli Studi di Padova and Istituto di Chimica Biomolecolare, Consiglio Nazionale delle Ricerche , 35131 Padua , Italy
| | - Roberto Benoni
- Dipartimento di Medicina e Chirurgia , Università di Parma , 43125 Parma , Italy
| | - Barbara Campanini
- Dipartimento di Scienze degli Alimenti e del Farmaco , Università di Parma , 43124 Parma , Italy
| | - Luca Ronda
- Dipartimento di Medicina e Chirurgia , Università di Parma , 43125 Parma , Italy
| | - Andrea Mozzarelli
- Dipartimento di Scienze degli Alimenti e del Farmaco , Università di Parma , 43124 Parma , Italy.,Istituto di Biofisica , Consiglio Nazionale delle Ricerche , 56124 Pisa , Italy.,Istituto Nazionale Biostrutture e Biosistemi , 00136 Rome , Italy
| | - Stefano Bettati
- Dipartimento di Medicina e Chirurgia , Università di Parma , 43125 Parma , Italy.,Istituto Nazionale Biostrutture e Biosistemi , 00136 Rome , Italy
| | - Roberto Battistutta
- Dipartimento di Scienze Chimiche , Università degli Studi di Padova and Istituto di Chimica Biomolecolare, Consiglio Nazionale delle Ricerche , 35131 Padua , Italy
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32
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Storti B, Margheritis E, Abbandonato G, Domenichini G, Dreier J, Testa I, Garau G, Nifosì R, Bizzarri R. Role of Gln222 in Photoswitching of Aequorea Fluorescent Proteins: A Twisting and H-Bonding Affair? ACS Chem Biol 2018; 13:2082-2093. [PMID: 29878744 DOI: 10.1021/acschembio.8b00267] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Reversibly photoswitchable fluorescent proteins (RSFPs) admirably combine the genetic encoding of fluorescence with the ability to repeatedly toggle between a bright and dark state, adding a new temporal dimension to the fluorescence signal. Accordingly, in recent years RSFPs have paved the way to novel applications in cell imaging that rely on their reversible photoswitching, including many super-resolution techniques such as F-PALM, RESOLFT, and SOFI that provide nanoscale pictures of the living matter. Yet many RSFPs have been engineered by a rational approach only to a limited extent, in the absence of clear structure-property relationships that in most cases make anecdotic the emergence of the photoswitching. We reported [ Bizzarri et al. J. Am Chem Soc. 2010 , 102 , 85 ] how the E222Q replacement is a single photoswitching mutation, since it restores the intrinsic cis-trans photoisomerization properties of the chromophore in otherwise nonswitchable Aequorea proteins of different color and mutation pattern (Q-RSFPs). We here investigate the subtle role of Q222 on the excited-state photophysics of the two simplest Q-RSFPs by a combined experimental and theoretical approach, using their nonswitchable anacestor EGFP as benchmark. Our findings link indissolubly photoswitching and Q222 presence, by a simple yet elegant scenario: largely twisted chromophore structures around the double bond (including hula-twist configurations) are uniquely stabilized by Q222 via H-bonds. Likely, these H-bonds subtly modulate the electronic properties of the chromophore, enabling the conical intersection that connects the excited cis to ground trans chromophore. Thus, Q222 belongs to a restricted family of single mutations that change dramatically the functional phenotype of a protein. The capability to distinguish quantitatively T65S/E222Q EGFP ("WildQ", wQ) from the spectrally identical EGFP by quantitative Optical Lock-In Detection (qOLID) witnesses the relevance of this mutation for cell imaging.
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Affiliation(s)
- Barbara Storti
- NEST, Scuola Normale Superiore and NANO-CNR, 56127 Pisa, Italy
| | - Eleonora Margheritis
- Center for Nanotechnology Innovation @ NEST, Istituto Italiano di Tecnologia, 56127 Pisa, Italy
| | | | | | - Jes Dreier
- Department of Applied Physics and Science for Life Laboratory, KTH Royal Institute of Technology, Tomtebodavägen 23A, 171 65 Stockholm, Sweden
| | - Ilaria Testa
- Department of Applied Physics and Science for Life Laboratory, KTH Royal Institute of Technology, Tomtebodavägen 23A, 171 65 Stockholm, Sweden
| | - Gianpiero Garau
- Center for Nanotechnology Innovation @ NEST, Istituto Italiano di Tecnologia, 56127 Pisa, Italy
| | - Riccardo Nifosì
- NEST, Scuola Normale Superiore and NANO-CNR, 56127 Pisa, Italy
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33
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Nolan R, Alvarez LA, Griffiths SC, Elegheert J, Siebold C, Padilla-Parra S. Calibration-free In Vitro Quantification of Protein Homo-oligomerization Using Commercial Instrumentation and Free, Open Source Brightness Analysis Software. J Vis Exp 2018:58157. [PMID: 30080195 PMCID: PMC6126508 DOI: 10.3791/58157] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Number and brightness is a calibration-free fluorescence fluctuation spectroscopy (FFS) technique for detecting protein homo-oligomerization. It can be employed using a conventional confocal microscope equipped with digital detectors. A protocol for the use of the technique in vitro is shown by means of a use case where number and brightness can be seen to accurately quantify the oligomeric state of mVenus-labelled FKBP12F36V before and after the addition of the dimerizing drug AP20187. The importance of using the correct microscope acquisition parameters and the correct data preprocessing and analysis methods are discussed. In particular, the importance of the choice of photobleaching correction is stressed. This inexpensive method can be employed to study protein-protein interactions in many biological contexts.
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Affiliation(s)
- Rory Nolan
- Cellular Imaging Group, Wellcome Centre Human Genetics, University of Oxford
| | - Luis A Alvarez
- Cellular Imaging Group, Wellcome Centre Human Genetics, University of Oxford
| | - Samuel C Griffiths
- Division of Structural Biology, Wellcome Centre Human Genetics, University of Oxford
| | - Jonathan Elegheert
- Division of Structural Biology, Wellcome Centre Human Genetics, University of Oxford
| | - Christian Siebold
- Division of Structural Biology, Wellcome Centre Human Genetics, University of Oxford
| | - Sergi Padilla-Parra
- Cellular Imaging Group, Wellcome Centre Human Genetics, University of Oxford; Division of Structural Biology, Wellcome Centre Human Genetics, University of Oxford; Dynamic Structural Virology Group, Biocruces Health Research Centre; IKERBASQUE, Basque Foundation for Science;
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34
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Steiert F, Petrov EP, Schultz P, Schwille P, Weidemann T. Photophysical Behavior of mNeonGreen, an Evolutionarily Distant Green Fluorescent Protein. Biophys J 2018; 114:2419-2431. [PMID: 29706225 DOI: 10.1016/j.bpj.2018.04.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 04/06/2018] [Accepted: 04/09/2018] [Indexed: 12/31/2022] Open
Abstract
Fluorescent proteins (FPs) feature complex photophysical behavior that must be considered when studying the dynamics of fusion proteins in model systems and live cells. In this work, we characterize mNeonGreen (mNG), a recently introduced FP from the bilaterian Branchiostoma lanceolatum, in comparison to the well-known hydrozoan variants enhanced green fluorescent protein (EGFP) and Aequorea coerulescens GFP by steady-state spectroscopy and fluorescence correlation spectroscopy in solutions of different pH. Blind spectral unmixing of sets of absorption spectra reveals three interconverting electronic states of mNG: a nonfluorescent protonated state, a bright state showing bell-shaped pH dependence, and a similarly bright state dominating at high pH. The gradual population of the acidic form by external protonation is reflected by increased flickering at low pH in fluorescence correlation spectroscopy measurements, albeit with much slower flicker rates and lower amplitudes as compared to Aequorea GFPs. In addition, increased flickering of mNG indicates a second deprotonation step above pH 10 leading to a slight decrease in fluorescence. Thus, mNG is distinguished from Aequorea GFPs by a two-step protonation response with opposite effects that reflects a chemically distinct chromophore environment. Despite the more complex pH dependence, mNG represents a superior FP under a broad range of conditions.
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Affiliation(s)
- Frederik Steiert
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried, Germany; Physics Department, Technical University Munich, Garching, Germany
| | - Eugene P Petrov
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried, Germany; Faculty of Physics, Ludwig Maximilian University of Munich, Munich, Germany
| | - Peter Schultz
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Petra Schwille
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Thomas Weidemann
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried, Germany.
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35
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Chen F, Zhao X, Liang W. One- and two-photon absorption spectra of the yellow fluorescent protein citrine: effects of intramolecular electron-vibrational coupling and intermolecular interactions. Mol Phys 2018. [DOI: 10.1080/00268976.2018.1426130] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Fasheng Chen
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Xiamen, China
- Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China
| | - Xinyi Zhao
- Department of Science and Technology for Inspection, Xiamen Huaxia University, Xiamen, China
| | - WanZhen Liang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Xiamen, China
- Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China
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36
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Köker T, Fernandez A, Pinaud F. Characterization of Split Fluorescent Protein Variants and Quantitative Analyses of Their Self-Assembly Process. Sci Rep 2018; 8:5344. [PMID: 29593344 PMCID: PMC5871787 DOI: 10.1038/s41598-018-23625-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 03/16/2018] [Indexed: 02/01/2023] Open
Abstract
Many biotechniques use complementary split-fluorescent protein (sFPs) fragments to visualize protein-protein interactions, image cells by ensemble or single molecule fluorescence microscopy, or assemble nanomaterials and protein superstructures. Yet, the reassembly mechanisms of sFPs, including fragment binding rates, folding, chromophore maturation and overall photophysics remain poorly characterized. Here, we evolved asymmetric and self-complementing green, yellow and cyan sFPs together with their full-length equivalents (flFPs) and described their biochemical and photophysical properties in vitro and in cells. While re-assembled sFPs have spectral properties similar to flFPs, they display slightly reduced quantum yields and fluorescence lifetimes due to a less sturdy β-barrel structure. The complementation of recombinant sFPs expressed in vitro follows a conformational selection mechanism whereby the larger sFP fragments exist in a monomer-dimer equilibrium and only monomers are competent for fluorescence complementation. This bimolecular fragment interaction involves a slow and irreversible binding step, followed by chromophore maturation at a rate similar to that of flFPs. When expressed as fusion tags in cells, sFPs behave as monomers directly activated with synthetic complementary fragments. This study resulted in the development of sFP color variants having improved maturation kinetics, brightness, and photophysics for fluorescence microscopy imaging of cellular processes, including single molecule detection.
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Affiliation(s)
- Tuğba Köker
- Department of Biological Sciences, University of Southern California, 1050 Child Way, Los Angeles, 90089, California, USA
| | - Anthony Fernandez
- Department of Biological Sciences, University of Southern California, 1050 Child Way, Los Angeles, 90089, California, USA
| | - Fabien Pinaud
- Department of Biological Sciences, University of Southern California, 1050 Child Way, Los Angeles, 90089, California, USA. .,Department of Chemistry, University of Southern California, 1050 Child Way, Los Angeles, 90089, California, USA. .,Department of Physics and Astronomy, University of Southern California, 1050 Child Way, Los Angeles, 90089, California, USA.
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37
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Crystal Structure of Green Fluorescent Protein Clover and Design of Clover-Based Redox Sensors. Structure 2018; 26:225-237.e3. [PMID: 29307487 DOI: 10.1016/j.str.2017.12.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 10/31/2017] [Accepted: 12/06/2017] [Indexed: 11/23/2022]
Abstract
We have determined the crystal structure of Clover, one of the brightest fluorescent proteins, and found that its T203H/S65G mutations relative to wild-type GFP lock the critical E222 side chain in a fixed configuration that mimics the major conformer of that in EGFP. The resulting equilibrium shift to the predominantly deprotonated chromophore increases the extinction coefficient (EC), opposes photoactivation, and is responsible for the bathochromic shift. Clover's brightness can further be attributed to a π-π stacking interaction between H203 and the chromophore. Consistent with these observations, the Clover G65S mutant reversed the equilibrium shift, dramatically decreased the EC, and made Clover photoactivatable under conditions that activated photoactivatable GFP. Using the Clover structure, we rationally engineered a non-photoactivatable redox sensor, roClover1, and determined its structure as well as that of its parental template, roClover0.1. These high-resolution structures provide deeper insights into structure-function relationships in GFPs and may aid the development of excitation-improved ratiometric biosensors.
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38
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Lee HB, Cong A, Leopold H, Currie M, Boersma AJ, Sheets ED, Heikal AA. Rotational and translational diffusion of size-dependent fluorescent probes in homogeneous and heterogeneous environments. Phys Chem Chem Phys 2018; 20:24045-24057. [DOI: 10.1039/c8cp03873b] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Macromolecular crowding effects on diffusion depend on the fluorophore structure, the concentration of crowding agents, and the technique employed.
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Affiliation(s)
- Hong Bok Lee
- Department of Chemistry and Biochemistry
- Swenson College of Science and Engineering
- University of Minnesota Duluth
- Duluth
- USA
| | - Anh Cong
- Department of Chemistry and Biochemistry
- Swenson College of Science and Engineering
- University of Minnesota Duluth
- Duluth
- USA
| | - Hannah Leopold
- Department of Chemistry and Biochemistry
- Swenson College of Science and Engineering
- University of Minnesota Duluth
- Duluth
- USA
| | - Megan Currie
- Department of Chemistry and Biochemistry
- Swenson College of Science and Engineering
- University of Minnesota Duluth
- Duluth
- USA
| | | | - Erin D. Sheets
- Department of Chemistry and Biochemistry
- Swenson College of Science and Engineering
- University of Minnesota Duluth
- Duluth
- USA
| | - Ahmed A. Heikal
- Department of Chemistry and Biochemistry
- Swenson College of Science and Engineering
- University of Minnesota Duluth
- Duluth
- USA
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39
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Ghosh A, Isbaner S, Veiga-Gutiérrez M, Gregor I, Enderlein J, Karedla N. Quantifying Microsecond Transition Times Using Fluorescence Lifetime Correlation Spectroscopy. J Phys Chem Lett 2017; 8:6022-6028. [PMID: 29183125 DOI: 10.1021/acs.jpclett.7b02707] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Many complex luminescent emitters such as fluorescent proteins exhibit multiple emitting states that result in rapid fluctuations of their excited-state lifetime. Here, we apply fluorescence lifetime correlation spectroscopy (FLCS) to resolve the photophysical state dynamics of the prototypical fluorescence protein enhanced green fluorescent protein (EGFP). We quantify the microsecond transition rates between its two fluorescent states, which have otherwise highly overlapping emission spectra. We relate these transitions to a room-temperature angstrom-scale rotational isomerism of an amino acid next to its fluorescent center. With this study, we demonstrate the power of FLCS for studying the rapid transition dynamics of a broad range of light-emitting systems with complex multistate photophysics, which cannot be easily done by other methods.
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Affiliation(s)
- Arindam Ghosh
- III. Institute of Physics, Georg August University , 37077 Göttingen, Germany
| | - Sebastian Isbaner
- III. Institute of Physics, Georg August University , 37077 Göttingen, Germany
| | | | - Ingo Gregor
- III. Institute of Physics, Georg August University , 37077 Göttingen, Germany
| | - Jörg Enderlein
- III. Institute of Physics, Georg August University , 37077 Göttingen, Germany
| | - Narain Karedla
- III. Institute of Physics, Georg August University , 37077 Göttingen, Germany
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40
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Disruption of the hydrogen bonding network determines the pH-induced non-fluorescent state of the fluorescent protein ZsYellow by protonation of Glu221. Biochem Biophys Res Commun 2017; 493:562-567. [DOI: 10.1016/j.bbrc.2017.08.152] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 08/30/2017] [Indexed: 11/18/2022]
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41
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Slocum JD, Webb LJ. A Double Decarboxylation in Superfolder Green Fluorescent Protein Leads to High Contrast Photoactivation. J Phys Chem Lett 2017; 8:2862-2868. [PMID: 28598160 DOI: 10.1021/acs.jpclett.7b01101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A photoactivatable variant of superfolder green fluorescent protein (GFP) was created by replacing the threonine at position 203 with aspartic acid. Photoactivation by exposure of this mutant to UV light resulted in conversion of the fluorophore from the neutral to the negatively charged form, accompanied by a ∼95-fold increase in fluorescence under 488 nm excitation. Mass spectrometry before and after exposure to UV light revealed a change in mass of 88 Da, attributed to the double decarboxylation of Glu 222 and Asp 203. Kinetics studies and nonlinear power-dependence of the initial rate of photoconversion indicated that the double decarboxylation occurred via a multiphoton absorption process at 254 nm. In addition to providing a photoactivatable GFP with robust folding properties, a detailed mechanistic understanding of this double decarboxylation in GFP will lead to a better understanding of charge transfer in fluorescent proteins.
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Affiliation(s)
- Joshua D Slocum
- Department of Chemistry, Center for Nano and Molecular Science and Technology, and Institute for Cell and Molecular Biology, The University of Texas at Austin , 105 East 24th Street STOP A5300, Austin, Texas 78712-1224, United States
| | - Lauren J Webb
- Department of Chemistry, Center for Nano and Molecular Science and Technology, and Institute for Cell and Molecular Biology, The University of Texas at Austin , 105 East 24th Street STOP A5300, Austin, Texas 78712-1224, United States
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42
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Barnett LM, Hughes TE, Drobizhev M. Deciphering the molecular mechanism responsible for GCaMP6m's Ca2+-dependent change in fluorescence. PLoS One 2017; 12:e0170934. [PMID: 28182677 PMCID: PMC5300113 DOI: 10.1371/journal.pone.0170934] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 01/12/2017] [Indexed: 11/19/2022] Open
Abstract
The goal of this work is to determine how GCaMP6m's fluorescence is altered in response to Ca2+-binding. Our detailed spectroscopic study reveals the simplest explanation for how GCaMP6m changes fluorescence in response to Ca2+ is with a four-state model, in which a Ca2+-dependent change of the chromophore protonation state, due to a shift in pKa, is the predominant factor. The pKa shift is quantitatively explained by a change in electrostatic potential around the chromophore due to the conformational changes that occur in the protein when calmodulin binds Ca2+ and interacts with the M13 peptide. The absolute pKa values for the Ca2+-free and Ca2+-saturated states of GCaMP6m are critical to its high signal-to-noise ratio. This mechanism has important implications for further improvements to GCaMP6m and potentially for other similarly designed biosensors.
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Affiliation(s)
- Lauren M. Barnett
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, Montana, United States
| | - Thomas E. Hughes
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, Montana, United States
| | - Mikhail Drobizhev
- Department of Cell Biology and Neuroscience, Montana State University, Bozeman, Montana, United States
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43
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Banerjee S, Schenkelberg CD, Jordan TB, Reimertz JM, Crone EE, Crone DE, Bystroff C. Mispacking and the Fitness Landscape of the Green Fluorescent Protein Chromophore Milieu. Biochemistry 2017; 56:736-747. [PMID: 28074648 PMCID: PMC6193456 DOI: 10.1021/acs.biochem.6b00800] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The autocatalytic maturation of the chromophore in green fluorescent protein (GFP) was thought to require the precise positioning of the side chains surrounding it in the core of the protein, many of which are strongly conserved among homologous fluorescent proteins. In this study, we screened for green fluorescence in an exhaustive set of point mutations of seven residues that make up the chromophore microenvironment, excluding R96 and E222 because mutations at these positions have been previously characterized. Contrary to expectations, nearly all amino acids were tolerated at all seven positions. Only four point mutations knocked out fluorescence entirely. However, chromophore maturation was found to be slower and/or fluorescence reduced in several cases. Selected combinations of mutations showed nonadditive effects, including cooperativity and rescue. The results provide guidelines for the computational engineering of GFPs.
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Affiliation(s)
- Shounak Banerjee
- Department of Biological Sciences, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Christian D. Schenkelberg
- Department of Biological Sciences, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Thomas B. Jordan
- Department of Biological Sciences, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Julia M. Reimertz
- Department of Biological Sciences, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Emily E. Crone
- Department of Biology, Colgate University, Hamilton, New York 13346, United States
| | - Donna E. Crone
- Department of Biological Sciences, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Christopher Bystroff
- Department of Biological Sciences, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
- Department of Computer Science, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
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44
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Märk J, Wagener A, Zhang E, Laufer J. Photoacoustic pump-probe tomography of fluorophores in vivo using interleaved image acquisition for motion suppression. Sci Rep 2017; 7:40496. [PMID: 28091571 PMCID: PMC5238439 DOI: 10.1038/srep40496] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 12/07/2016] [Indexed: 01/28/2023] Open
Abstract
In fluorophores, the excited state lifetime can be modulated using pump-probe excitation. By generating photoacoustic (PA) signals using simultaneous and time-delayed pump and probe excitation pulses at fluences below the maximum permissible exposure, a modulation of the signal amplitude is observed in fluorophores but not in endogenous chromophores. This provides a highly specific contrast mechanism that can be used to recover the location of the fluorophore using difference imaging. The practical challenges in applying this method to in vivo PA tomography include the typically low concentrations of fluorescent contrast agents, and tissue motion. The former results in smaller PA signal amplitudes compared to those measured in blood, while the latter gives rise to difference image artefacts that compromise the unambiguous and potentially noise-limited detection of fluorescent contrast agents. To address this limitation, a method based on interleaved pump-probe image acquisition was developed. It relies on fast switching between simultaneous and time-delayed pump-probe excitation to acquire PA difference signals in quick succession, and to minimise the effects of tissue motion. The feasibility of this method is demonstrated in tissue phantoms and in initial experiments in vivo.
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Affiliation(s)
- Julia Märk
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstraße 36A, 10623 Berlin, Germany
| | - Asja Wagener
- Medizinische Klinik mit Schwerpunkt Hepatologie und Gastroenterologie, Charité - Universitätsmedizin Berlin, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Edward Zhang
- Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London WC1E 6BT, UK
| | - Jan Laufer
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstraße 36A, 10623 Berlin, Germany.,Institut für Radiologie, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
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45
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Wiens MD, Shen Y, Li X, Salem MA, Smisdom N, Zhang W, Brown A, Campbell RE. A Tandem Green-Red Heterodimeric Fluorescent Protein with High FRET Efficiency. Chembiochem 2016; 17:2361-2367. [PMID: 27781394 DOI: 10.1002/cbic.201600492] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Indexed: 12/28/2022]
Abstract
The tetrameric red fluorescent protein from Discosoma sp. coral (DsRed) has previously been engineered to produce dimeric and monomeric fluorescent variants with excitation and emission profiles that span the visible spectrum. The brightest of the effectively monomeric DsRed variants is tdTomato-a tandem fusion of a dimeric DsRed variant. Here we describe the engineering of brighter red (RRvT), green (GGvT), and green-red heterodimeric (GRvT) tdTomato variants. GRvT exhibited 99 % intramolecular FRET efficiency, resulting in long Stokes shift red fluorescence. These new variants could prove useful for multicolor live-cell imaging applications.
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Affiliation(s)
- Matthew D Wiens
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta, T6G 2G2, Canada
| | - Yi Shen
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta, T6G 2G2, Canada
| | - Xi Li
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta, T6G 2G2, Canada
| | - M Alaraby Salem
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta, T6G 2G2, Canada
| | - Nick Smisdom
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta, T6G 2G2, Canada
- Present address: Faculty of Medicine and Life Sciences, Universiteit Hasselt, Martelarenlaan 42, 3500, Hasselt, Belgium
| | - Wei Zhang
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta, T6G 2G2, Canada
| | - Alex Brown
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta, T6G 2G2, Canada
| | - Robert E Campbell
- Department of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta, T6G 2G2, Canada
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46
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Araujo JV, Rifaie-Graham O, Apebende EA, Bruns N. Self-reporting Polymeric Materials with Mechanochromic Properties. BIO-INSPIRED POLYMERS 2016. [DOI: 10.1039/9781782626664-00354] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The mechanical transduction of force onto molecules is an essential feature of many biological processes that results in the senses of touch and hearing, gives important cues for cellular interactions and can lead to optically detectable signals, such as a change in colour, fluorescence or chemoluminescence. Polymeric materials that are able to visually indicate deformation, stress, strain or the occurrence of microdamage draw inspiration from these biological events. The field of self-reporting (or self-assessing) materials is reviewed. First, mechanochromic events in nature are discussed, such as the formation of bruises on skin, the bleeding of a wound, or marine glow caused by dinoflagellates. Then, materials based on force-responsive mechanophores, such as spiropyrans, cyclobutanes, cyclooctanes, Diels–Alder adducts, diarylbibenzofuranone and bis(adamantyl)-1,2-dioxetane are reviewed, followed by mechanochromic blends, chromophores stabilised by hydrogen bonds, and pressure sensors based on ionic interactions between fluorescent dyes and polyelectrolyte brushes. Mechanobiochemistry is introduced as an important tool to create self-reporting hybrid materials that combine polymers with the force-responsive properties of fluorescent proteins, protein FRET pairs, and other biomacromolecules. Finally, dye-filled microcapsules, microvascular networks, and hollow fibres are demonstrated to be important technologies to create damage-indicating coatings, self-reporting fibre-reinforced composites and self-healing materials.
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Affiliation(s)
- Jose V. Araujo
- Adolphe Merkle Institute, University of Fribourg Chemin des Verdiers 4 1700 Fribourg Switzerland
| | - Omar Rifaie-Graham
- Adolphe Merkle Institute, University of Fribourg Chemin des Verdiers 4 1700 Fribourg Switzerland
| | - Edward A. Apebende
- Adolphe Merkle Institute, University of Fribourg Chemin des Verdiers 4 1700 Fribourg Switzerland
| | - Nico Bruns
- Adolphe Merkle Institute, University of Fribourg Chemin des Verdiers 4 1700 Fribourg Switzerland
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47
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Park JW, Rhee YM. Electric Field Keeps Chromophore Planar and Produces High Yield Fluorescence in Green Fluorescent Protein. J Am Chem Soc 2016; 138:13619-13629. [PMID: 27662359 DOI: 10.1021/jacs.6b06833] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The green fluorescent protein and its designed variants fluoresce efficiently. Because the isolated chromophore is not fluorescent in a practical sense, it is apparent that the protein environment plays a crucial role in its efficiency. Because of various obstacles in studying excited state dynamics of complex systems, however, the detailed mechanism of this efficiency enhancement is not yet clearly elucidated. Here, by adopting excited state nonadiabatic molecular dynamics simulations together with an interpolated quantum chemical potential model of the chromophore, we find that the strong electric field from the protein matrix contributes dominantly to the motional restriction of the chromophore. The delay in twisting motion subsequently obstructs the nonradiative decay that competes with fluorescence, leading naturally to an enhancement in light-emitting efficiency. Surprisingly, steric constraints make only a minor contribution to these aspects. Through residue specific analyses, we identify a group of key residues that control the excited state behavior. Testing a series of mutant GFPs with different brightnesses also supports the view regarding the importance of protein electrostatics. Our findings may provide a useful guide toward designing new fluorescent chemical systems in the future.
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Affiliation(s)
- Jae Woo Park
- Center for Self-assembly and Complexity, Institute for Basic Science (IBS) , Pohang 37673, Korea.,Department of Chemistry, Pohang University of Science and Technology (POSTECH) , Pohang 37673, Korea
| | - Young Min Rhee
- Center for Self-assembly and Complexity, Institute for Basic Science (IBS) , Pohang 37673, Korea.,Department of Chemistry, Pohang University of Science and Technology (POSTECH) , Pohang 37673, Korea
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48
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Park JW, Rhee YM. Emission shaping in fluorescent proteins: role of electrostatics and π-stacking. Phys Chem Chem Phys 2016; 18:3944-55. [DOI: 10.1039/c5cp07535a] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We obtained the fluorescence spectrum of the GFP with trajectory simulations, and revealed the role of the protein sidechains in emission shifts.
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Affiliation(s)
- Jae Woo Park
- Center for Self-assembly and Complexity
- Institute for Basic Science (IBS)
- Pohang 37673
- Korea
- Department of Chemistry
| | - Young Min Rhee
- Center for Self-assembly and Complexity
- Institute for Basic Science (IBS)
- Pohang 37673
- Korea
- Department of Chemistry
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49
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Märk J, Schmitt FJ, Theiss C, Dortay H, Friedrich T, Laufer J. Photoacoustic imaging of fluorophores using pump-probe excitation. BIOMEDICAL OPTICS EXPRESS 2015; 6:2522-2535. [PMID: 26203378 PMCID: PMC4505706 DOI: 10.1364/boe.6.002522] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 05/18/2015] [Accepted: 05/21/2015] [Indexed: 06/08/2023]
Abstract
A pump-probe technique for the detection of fluorophores in tomographic PA images is introduced. It is based on inducing stimulated emission in fluorescent molecules, which in turn modulates the amount of thermalized energy, and hence the PA signal amplitude. A theoretical model of the PA signal generation in fluorophores is presented and experimentally validated on cuvette measurements made in solutions of Rhodamine 6G, a fluorophore of known optical and molecular properties. The application of this technique to deep tissue tomographic PA imaging is demonstrated by determining the spatial distribution of a near-infrared fluorophore in a tissue phantom.
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Affiliation(s)
- Julia Märk
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Franz-Josef Schmitt
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Christoph Theiss
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Hakan Dortay
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Thomas Friedrich
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Jan Laufer
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
- Institut für Radiologie, Charité – Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
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50
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Kikot P, Polat A, Achilli E, Fernandez Lahore M, Grasselli M. Immobilized palladium(II) ion affinity chromatography for recovery of recombinant proteins with peptide tags containing histidine and cysteine. J Mol Recognit 2015; 27:659-68. [PMID: 25277090 DOI: 10.1002/jmr.2389] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 04/28/2014] [Accepted: 04/28/2014] [Indexed: 11/10/2022]
Abstract
Fusion of peptide-based tags to recombinant proteins is currently one of the most used tools for protein production. Also, immobilized metal ion affinity chromatography (IMAC) has a huge application in protein purification, especially in research labs. The combination of expression systems of recombinant tagged proteins with this robust chromatographic system has become an efficient and rapid tool to produce milligram-range amounts of proteins. IMAC-Ni(II) columns have become the natural partners of 6xHis-tagged proteins. The Ni(II) ion is considered as the best compromise of selectivity and affinity for purification of a recombinant His-tagged protein. The palladium(II) ion is also able to bind to side chains of amino acids and form ternary complexes with iminodiacetic acid and free amino acids and other sulfur-containing molecules. In this work, we evaluated two different cysteine- and histidine-containing six amino acid tags linked to the N-terminal group of green fluorescent protein (GFP) and studied the adsorption and elution conditions using novel eluents. Both cysteine-containing tagged GFPs were able to bind to IMAC-Pd(II) matrices and eluted successfully using a low concentration of thiourea solution. The IMAC-Ni(II) system reaches less than 20% recovery of the cysteine-containing tagged GFP from a crude homogenate of recombinant Escherichia coli, meanwhile the IMAC-Pd(II) yields a recovery of 45% with a purification factor of 13.
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Affiliation(s)
- Pamela Kikot
- Laboratorio de Materiales Biotecnológicos (LaMaBio), Universidad Nacional de Quilmes-IMBICE (CONICET), Roque Sáenz Peña 352, B1876BXD, Bernal, Argentina
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