1
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Bustorff N, Fitter J. Features of Protein Unfolding Transitions and Their Relation to Domain Topology Probed by Single-Molecule FRET. Biomolecules 2023; 13:1280. [PMID: 37759680 PMCID: PMC10526189 DOI: 10.3390/biom13091280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 08/10/2023] [Accepted: 08/19/2023] [Indexed: 09/29/2023] Open
Abstract
A protein fold is defined as a structural arrangement of a secondary structure in a three-dimensional space. It would be interesting to know whether a particular fold can be assigned to certain features of the corresponding folding/unfolding transitions. To understand the underlying principles of the manifold folding transitions in more detail, single-molecule FRET is the method of choice. Taking the two-domain protein phosphoglycerate kinase (PGK) as an example, we investigated denaturant-induced unfolded states of PGK using the above method. For this purpose, different intramolecular distances within the two domains were measured. In addition to the known two-state transition, a transition with a compact folding intermediate was also identified in each of the two domains. Based on the structural homology of the domains (characterized by a Rossmann fold) and the striking similarity in the features of the measured distance changes during unfolding, clear evidence emerged that the underlying domain topology plays an important role in determining the observed structural changes.
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Affiliation(s)
- Nuno Bustorff
- ER-C-3 Structural Biology & IBI-6 Cellular Structural Biology, Forschungszentrum Jülich, 52425 Jülich, Germany;
| | - Jörg Fitter
- ER-C-3 Structural Biology & IBI-6 Cellular Structural Biology, Forschungszentrum Jülich, 52425 Jülich, Germany;
- AG Biophysik, I. Physikalisches Institut (IA), RWTH Aachen University, 52074 Aachen, Germany
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2
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Barth A, Opanasyuk O, Peulen TO, Felekyan S, Kalinin S, Sanabria H, Seidel CAM. Unraveling multi-state molecular dynamics in single-molecule FRET experiments. I. Theory of FRET-lines. J Chem Phys 2022; 156:141501. [PMID: 35428384 PMCID: PMC9014241 DOI: 10.1063/5.0089134] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Conformational dynamics of biomolecules are of fundamental importance for their function. Single-molecule studies of Förster Resonance Energy Transfer (smFRET) between a tethered donor and acceptor dye pair are a powerful tool to investigate the structure and dynamics of labeled molecules. However, capturing and quantifying conformational dynamics in intensity-based smFRET experiments remains challenging when the dynamics occur on the sub-millisecond timescale. The method of multiparameter fluorescence detection addresses this challenge by simultaneously registering fluorescence intensities and lifetimes of the donor and acceptor. Together, two FRET observables, the donor fluorescence lifetime τD and the intensity-based FRET efficiency E, inform on the width of the FRET efficiency distribution as a characteristic fingerprint for conformational dynamics. We present a general framework for analyzing dynamics that relates average fluorescence lifetimes and intensities in two-dimensional burst frequency histograms. We present parametric relations of these observables for interpreting the location of FRET populations in E–τD diagrams, called FRET-lines. To facilitate the analysis of complex exchange equilibria, FRET-lines serve as reference curves for a graphical interpretation of experimental data to (i) identify conformational states, (ii) resolve their dynamic connectivity, (iii) compare different kinetic models, and (iv) infer polymer properties of unfolded or intrinsically disordered proteins. For a simplified graphical analysis of complex kinetic networks, we derive a moment-based representation of the experimental data that decouples the motion of the fluorescence labels from the conformational dynamics of the biomolecule. Importantly, FRET-lines facilitate exploring complex dynamic models via easily computed experimental observables. We provide extensive computational tools to facilitate applying FRET-lines.
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Affiliation(s)
- Anders Barth
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Oleg Opanasyuk
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Thomas-Otavio Peulen
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Suren Felekyan
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Stanislav Kalinin
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Hugo Sanabria
- Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29631, USA
| | - Claus A. M. Seidel
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, Düsseldorf, Germany
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3
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Yukhnovets O, Höfig H, Bustorff N, Katranidis A, Fitter J. Impact of Molecule Concentration, Diffusion Rates and Surface Passivation on Single-Molecule Fluorescence Studies in Solution. Biomolecules 2022; 12:biom12030468. [PMID: 35327660 PMCID: PMC8946791 DOI: 10.3390/biom12030468] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 03/09/2022] [Accepted: 03/16/2022] [Indexed: 12/04/2022] Open
Abstract
For single-molecule studies in solution, very small concentrations of dye-labelled molecules are employed in order to achieve single-molecule sensitivity. In typical studies with confocal microscopes, often concentrations in the pico-molar regime are required. For various applications that make use of single-molecule Förster resonance energy transfer (smFRET) or two-color coincidence detection (TCCD), the molecule concentration must be set explicitly to targeted values and furthermore needs to be stable over a period of several hours. As a consequence, specific demands must be imposed on the surface passivation of the cover slides during the measurements. The aim of having only one molecule in the detection volume at the time is not only affected by the absolute molecule concentration, but also by the rate of diffusion. Therefore, we discuss approaches to control and to measure absolute molecule concentrations. Furthermore, we introduce an approach to calculate the probability of chance coincidence events and demonstrate that measurements with challenging smFRET samples require a strict limit of maximal sample concentrations in order to produce meaningful results.
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Affiliation(s)
- Olessya Yukhnovets
- AG Biophysik, I. Physikalisches Institut (IA), RWTH Aachen University, 52074 Aachen, Germany;
- Correspondence: (O.Y.); (J.F.)
| | - Henning Höfig
- AG Biophysik, I. Physikalisches Institut (IA), RWTH Aachen University, 52074 Aachen, Germany;
| | - Nuno Bustorff
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C-3), Institute of Biological Information Processing IBI-6, Forschungszentrum Jülich, 52425 Jülich, Germany; (N.B.); (A.K.)
| | - Alexandros Katranidis
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C-3), Institute of Biological Information Processing IBI-6, Forschungszentrum Jülich, 52425 Jülich, Germany; (N.B.); (A.K.)
| | - Jörg Fitter
- AG Biophysik, I. Physikalisches Institut (IA), RWTH Aachen University, 52074 Aachen, Germany;
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C-3), Institute of Biological Information Processing IBI-6, Forschungszentrum Jülich, 52425 Jülich, Germany; (N.B.); (A.K.)
- Correspondence: (O.Y.); (J.F.)
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4
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Ghosh R, Singh S, Mukherjee D, Mondal S, Das M, Pal U, Adhikari A, Bhushan A, Bose S, Bhattacharyya SS, Pal D, Saha-Dasgupta T, Bhattacharyya M, Bhattacharyya D, Mallick AK, Das R, Pal SK. Host-assisted delivery of a model drug to genomic DNA: Key information from ultrafast spectroscopy and in silico study. Chembiochem 2022; 23:e202200109. [PMID: 35225409 DOI: 10.1002/cbic.202200109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Indexed: 11/10/2022]
Abstract
Intended drug delivery to a target without adverse effect is one of the major criteria for its acceptance in real use. Herein, we have made an attempt to explore the delivery efficacy of SDS surfactant in a monomer and micellar stage during the delivery of model drug, Toluidine Blue (TB) from micellar cavity to DNA. Molecular recognition of pre-micellar SDS encapsulated TB with DNA occurs at a rate constant (k1~652 s-1). On the contrary, no significant release of encapsulated TB at micellar concentration was observed within the experimental time frame. This originated from the higher binding affinity of TB towards the nano cavity of SDS at micellar concentration which doesn't allow the delivery of TB from the nano cavity of SDS micelle to DNA. Thus, molecular recognition controls the extent of DNA recognition by TB which in turn modulates the rate of delivery of TB from SDS in a concentration dependent morphology.
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Affiliation(s)
- Ria Ghosh
- S N Bose National Centre for Basic Sciences, CBMS, Block JD, Sector 3, Salt lake,, 700106, Kolkata, INDIA
| | - Soumendra Singh
- S N Bose National Centre for Basic Sciences, Technical Research Centre, Block JD, Sector 3, Salt Lake, 700106, Kolkata, INDIA
| | - Dipanjan Mukherjee
- S N Bose National Centre for Basic Sciences, CBMS, Block JD, Sector 3, Salt lake, 700106, Kolkata, INDIA
| | - Susmita Mondal
- S N Bose National Centre for Basic Sciences, CBMS, Block JD, Sector 3, Salt lake, 700106, Kolkata, INDIA
| | - Monojit Das
- Vidyasagar University, Zoology, 7221102, Midnapore, INDIA
| | - Uttam Pal
- S N Bose National Centre for Basic Sciences, Technical Research Centre, Block JD, Sector 3, Salt Lake, 700106, Kolkata, INDIA
| | - Aniruddha Adhikari
- S N Bose National Centre for Basic Sciences, CBMS, Block JD, Sector 3, Salt lake, 700106, Kolkata, INDIA
| | - Aman Bhushan
- Thapar University: Thapar Institute of Engineering and Technology, Biotechnology, Bhadson Road, Patiala, Punjab, 147004, Patiala, INDIA
| | - Surajit Bose
- KSDJ Dental College and Hospital, Oral and Maxillofacial Pathology, 700002, Kolkata, INDIA
| | | | - Debasish Pal
- Uluberia College, Zoology, 711315, Howrah, INDIA
| | - Tanusri Saha-Dasgupta
- S N Bose National Centre for Basic Sciences, CMPS, Block JD, Sector 3, Salt Lake, 700106, Kolkata, INDIA
| | - Maitree Bhattacharyya
- University of Calcutta, Biochemistry, 35, Ballygunge Circular Rd, Ballygunge, 700019, Kolkata, INDIA
| | - Debasis Bhattacharyya
- Nilratan Sircar Medical College and Hospital, Gynecology and Obstetrics, 138, AJC Bose Road, Sealdah, Raja Bazar,, 700014, Kolkata, INDIA
| | - Asim Kumar Mallick
- Nilratan Sircar Medical College and Hospital, Pediatric Medicine, 138, AJC Bose Road, Sealdah, Raja Bazar, 700014, Kolkata, INDIA
| | - Ranjan Das
- West Bengal State University, Chemistry, 700126, Kolkata, INDIA
| | - Samir Kumar Pal
- SNBNCBS, CBMS, Block JD, Sector III, Salt Lake City, 700098, Kolkata, INDIA
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5
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Nasser M, Meller A. Lifetime-based analysis of binary fluorophores mixtures in the low photon count limit. iScience 2022; 25:103554. [PMID: 34977508 PMCID: PMC8689154 DOI: 10.1016/j.isci.2021.103554] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Revised: 10/18/2021] [Accepted: 11/30/2021] [Indexed: 11/28/2022] Open
Abstract
Single biomolecule sensing often requires the quantification of multiple fluorescent species. Here, we theoretically and experimentally use time-resolved fluorescence via Time Correlated Single Photon Counting (TCSPC) to accurately quantify fluorescent species with similar chromatic signatures. A modified maximum likelihood estimator is introduced to include two fluorophore species, with compensation of the instrument response function. We apply this algorithm to simulated data of a simplified two-fluorescent species model, as well as to experimental data of fluorophores' mixtures and to a model protein, doubly labeled with different fluorophores' ratio. We show that 100 to 200 photons per fluorophore, in a 10-ms timescale, are sufficient to provide an accurate estimation of the dyes' ratio on the model protein. Our results provide estimation for the desired photon integration time toward implementation of TCSPC in systems with fast occurring events, such as translocation of biomolecules through nanopores or single-molecule burst analyses experiments. Exact ratios of emission-similar dyes in binary mixtures were quantified by TCSPC MLE-based analysis with IRF compensation was implemented for two fluorescent dyes Dual dye bioconjugation on a model protein was quantified at limited photon counts
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Affiliation(s)
- Maisa Nasser
- Department of Biomedical Engineering, Technion - IIT, Haifa 32000, Israel
| | - Amit Meller
- Department of Biomedical Engineering, Technion - IIT, Haifa 32000, Israel
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6
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Mukherjee D, Hasan MN, Ghosh R, Ghosh G, Bera A, Prasad SE, Hiwale A, Vemula PK, Das R, Pal SK. Decoding the Kinetic Pathways toward a Lipid/DNA Complex of Alkyl Alcohol Cationic Lipids Formed in a Microfluidic Channel. J Phys Chem B 2022; 126:588-600. [PMID: 35041417 DOI: 10.1021/acs.jpcb.1c07263] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Complexes of cationic liposomes with DNA have emerged as promising nonviral vectors for delivering genetic information into cells for gene therapy. Kinetics of the liposome/DNA complex (lipoplex) formation on a millisecond time scale are studied by monitoring time evolution of fluorescence of 8-anilino-1-naphthalene sulfonic acid (ANS) and ethidium bromide (EtBr) in a continuous flow microfluidic channel coupled to a fluorescence microscope. The formation of lipoplexes between calf thymus DNA and liposomes based on two novel cationic lipids (Lip1810 and Lip1814) are found to follow a two-step process with kinetic constants for the Lip1814/DNA complex (k1 = 1120-1383 s-1, k2 = 0.227-1.45 s-1) being significantly different from those (k1 = 68.53-98.5 s-1, k2 = 32.3-60.19 s-1) corresponding to formation of the Lip1810/DNA complex. The kinetic pathway leading to the formation of Lip1814/DNA complex is diffusion-controlled whereas the formation of Lip1810/DNA complex occurs by a conformational rearrangement-controlled pathway. The observed difference in the kinetics of lipoplex formation likely originates from different structures of the lipid/DNA complexes.
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Affiliation(s)
- Dipanjan Mukherjee
- Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
| | - Md Nur Hasan
- Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
| | - Ria Ghosh
- Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India.,Department of Biochemistry, University of Calcutta, 35 Ballygunge Circular Road, Ballygunge, Kolkata 700019, India
| | - Gourab Ghosh
- Department of Chemistry, West Bengal State University, Barasat, Kolkata 700126, India
| | - Arpan Bera
- Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
| | - Sujanthi Easwara Prasad
- Institute for Stem Cell Science and Regenerative Medicine (instem), GKVK Campus, Bellary Road, Bangalore, 560065 KA, India.,School of Chemical and Biotechnology, SASTRA University, Thanjavur 613401, TN, India
| | - Ankita Hiwale
- Institute for Stem Cell Science and Regenerative Medicine (instem), GKVK Campus, Bellary Road, Bangalore, 560065 KA, India
| | - Praveen K Vemula
- Institute for Stem Cell Science and Regenerative Medicine (instem), GKVK Campus, Bellary Road, Bangalore, 560065 KA, India
| | - Ranjan Das
- Department of Chemistry, West Bengal State University, Barasat, Kolkata 700126, India
| | - Samir Kumar Pal
- Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
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7
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Gebhardt C, Lehmann M, Reif MM, Zacharias M, Gemmecker G, Cordes T. Molecular and Spectroscopic Characterization of Green and Red Cyanine Fluorophores from the Alexa Fluor and AF Series*. Chemphyschem 2021; 22:1566-1583. [PMID: 34185946 PMCID: PMC8457111 DOI: 10.1002/cphc.202000935] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 06/01/2021] [Indexed: 12/23/2022]
Abstract
The use of fluorescence techniques has an enormous impact on various research fields including imaging, biochemical assays, DNA-sequencing and medical technologies. This has been facilitated by the development of numerous commercial dyes with optimized photophysical and chemical properties. Often, however, information about the chemical structures of dyes and the attached linkers used for bioconjugation remain a well-kept secret. This can lead to problems for research applications where knowledge of the dye structure is necessary to predict or understand (unwanted) dye-target interactions, or to establish structural models of the dye-target complex. Using a combination of optical spectroscopy, mass spectrometry, NMR spectroscopy and molecular dynamics simulations, we here investigate the molecular structures and spectroscopic properties of dyes from the Alexa Fluor (Alexa Fluor 555 and 647) and AF series (AF555, AF647, AFD647). Based on available data and published structures of the AF and Cy dyes, we propose a structure for Alexa Fluor 555 and refine that of AF555. We also resolve conflicting reports on the linker composition of Alexa Fluor 647 maleimide. We also conducted a comprehensive comparison between Alexa Fluor and AF dyes by continuous-wave absorption and emission spectroscopy, quantum yield determination, fluorescence lifetime and anisotropy spectroscopy of free and protein-attached dyes. All these data support the idea that Alexa Fluor and AF dyes have a cyanine core and are a derivative of Cy3 and Cy5. In addition, we compared Alexa Fluor 555 and Alexa Fluor 647 to their structural homologs AF555 and AF(D)647 in single-molecule FRET applications. Both pairs showed excellent performance in solution-based smFRET experiments using alternating laser excitation. Minor differences in apparent dye-protein interactions were investigated by molecular dynamics simulations. Our findings clearly demonstrate that the AF-fluorophores are an attractive alternative to Alexa- and Cy-dyes in smFRET studies or other fluorescence applications.
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Affiliation(s)
- Christian Gebhardt
- Physical and Synthetic Biology, Faculty of BiologyLudwig-Maximilians-Universität MünchenGroßhadernerstr. 2–482152Planegg-MartinsriedGermany
| | - Martin Lehmann
- Plant Molecular Biology, Faculty of BiologyLudwig-Maximilians-Universität MünchenGroßhadernerstr. 2–482152Planegg-MartinsriedGermany
| | - Maria M. Reif
- Theoretical Biophysics (T38), Physics DepartmentTechnical University of MunichCenter for Functional Protein Assemblies (CPA), Ernst-Otto-Fischer-Str. 885748GarchingGermany
| | - Martin Zacharias
- Theoretical Biophysics (T38), Physics DepartmentTechnical University of MunichCenter for Functional Protein Assemblies (CPA), Ernst-Otto-Fischer-Str. 885748GarchingGermany
| | - Gerd Gemmecker
- Bavarian NMR Center (B NMRZ), Department of ChemistryTechnical University of MunichLichtenbergstr. 485748GarchingGermany
| | - Thorben Cordes
- Physical and Synthetic Biology, Faculty of BiologyLudwig-Maximilians-Universität MünchenGroßhadernerstr. 2–482152Planegg-MartinsriedGermany
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Schepers B, Gohlke H. AMBER-DYES in AMBER: Implementation of fluorophore and linker parameters into AmberTools. J Chem Phys 2021; 152:221103. [PMID: 32534525 DOI: 10.1063/5.0007630] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Molecular dynamics (MD) simulations of explicit representations of fluorescent dyes attached via a linker to a protein allow, e.g., probing commonly used approximations for dye localization and/or orientation or modeling Förster resonance energy transfer. However, setting up and performing such MD simulations with the AMBER suite of biomolecular simulation programs has remained challenging due to the unavailability of an easy-to-use set of parameters within AMBER. Here, we adapted the AMBER-DYES parameter set derived by Graen et al. [J. Chem. Theory Comput. 10, 5505 (2014)] into "AMBER-DYES in AMBER" to generate a force field applicable within AMBER for commonly used fluorescent dyes and linkers attached to a protein. In particular, the computationally efficient graphics processing unit (GPU) implementation of the AMBER MD engine can now be exploited to overcome sampling issues of dye movements. The implementation is compatible with state-of-the-art force fields such as GAFF, GAFF2, ff99SB, ff14SB, lipid17, and GLYCAM_06j, which allows simulating post-translationally modified proteins and/or protein-ligand complexes and/or proteins in membrane environments. It is applicable with frequently used water models such as TIP3P, TIP4P, TIP4P-Ew, and OPC. For ease of use, a LEaP-based workflow was created, which allows attaching (multiple) dye/linker combinations to a protein prior to further system preparation steps. Following the parameter development described by Graen et al. [J. Chem. Theory Comput. 10, 5505 (2014)] and the adaptation steps described here, AMBER-DYES in AMBER can be extended by additional linkers and fluorescent molecules.
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Affiliation(s)
- Bastian Schepers
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
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Cerminara M, Schöne A, Ritter I, Gabba M, Fitter J. Mapping Multiple Distances in a Multidomain Protein for the Identification of Folding Intermediates. Biophys J 2020; 118:688-697. [PMID: 31916943 PMCID: PMC7002912 DOI: 10.1016/j.bpj.2019.12.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 11/13/2019] [Accepted: 12/10/2019] [Indexed: 10/27/2022] Open
Abstract
The investigation and understanding of the folding mechanism of multidomain proteins is still a challenge in structural biology. The use of single-molecule Förster resonance energy transfer offers a unique tool to map conformational changes within the protein structure. Here, we present a study following denaturant-induced unfolding transitions of yeast phosphoglycerate kinase by mapping several inter- and intradomain distances of this two-domain protein, exhibiting a quite heterogeneous behavior. On the one hand, the development of the interdomain distance during the unfolding transition suggests a classical two-state unfolding behavior. On the other hand, the behavior of some intradomain distances indicates the formation of a compact and transient molten globule intermediate state. Furthermore, different intradomain distances measured within the same domain show pronounced differences in their unfolding behavior, underlining the fact that the choice of dye attachment positions within the polypeptide chain has a substantial impact on which unfolding properties are observed by single-molecule Förster resonance energy transfer measurements. Our results suggest that, to fully characterize the complex folding and unfolding mechanism of multidomain proteins, it is necessary to monitor multiple intra- and interdomain distances because a single reporter can lead to a misleading, partial, or oversimplified interpretation.
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Affiliation(s)
- Michele Cerminara
- Forschungszentrum Jülich, Institute of Complex Systems ICS-5, Jülich, Germany.
| | - Antonie Schöne
- Forschungszentrum Jülich, Institute of Complex Systems ICS-5, Jülich, Germany
| | - Ilona Ritter
- Forschungszentrum Jülich, Institute of Complex Systems ICS-5, Jülich, Germany
| | - Matteo Gabba
- Forschungszentrum Jülich, Institute of Complex Systems ICS-5, Jülich, Germany
| | - Jörg Fitter
- Forschungszentrum Jülich, Institute of Complex Systems ICS-5, Jülich, Germany; RWTH Aachen University, I. Physikalisches Institut (IA), Aachen, Germany.
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Mukherjee D, Singh P, Rakshit T, Puthiya-Purayil TP, Vemula PK, Sengupta J, Das R, Pal SK. Deciphering the response of asymmetry in the hydrophobic chains of novel cationic lipids towards biological function. Phys Chem Chem Phys 2020; 22:1738-1746. [PMID: 31898698 DOI: 10.1039/c9cp05405g] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cationic liposomes, a type of non-viral vectors, often play the important biological function of delivering nucleic acids during cell transfection. Variations in the molecular architecture of di-alkyl dihydroxy ethyl ammonium chloride-based cationic lipids involving hydrophobic tails have been found to influence their biological function in terms of cell transfection efficiency. For example, liposomes based on a cationic lipid (Lip1814) with asymmetry in the hydrophobic chains were found to display higher transfection efficacy in cultured mammalian cell lines than those comprising of symmetric Lip1818 or asymmetric Lip1810. The effect of variations in the molecular architecture of the cationic lipids on the biological activity of liposomes has been explored here via the photophysical studies of 8-anilino-1-naphthalenesulphonate (ANS) and Nile Red (NR) in three cationic liposomes, namely Lip1810, Lip1814 and Lip1818. Time-resolved fluorescence of ANS revealed reduced hydration at the lipid-water interface and enhanced relaxation dynamics of surface water (lipid headgroup bound water molecules) in Lip1810- and Lip1814-based liposomes in the presence of cholesterol. As the probe ANS failed to be incorporated into the lipid-water interface of Lip1818 due to the significantly high rigidity of these liposomes, no information concerning the extent of hydration of the lipid-water interface or the interfacial water dynamics could be obtained. Time-resolved polarization-gated anisotropy measurements of NR in the presence of cholesterol revealed the rigidity of the cationic liposomes to be increasing in the order of Lip1810 < Lip1814 < Lip1818. In the presence of cholesterol, moderately higher rigidity, reduced membrane hydration and enhanced relaxation dynamics of the interfacial water molecules gave rise to the superior cell transfection efficacy of Lip1814-based cationic liposomes than those of the highly flexible Lip1810 or the highly rigid Lip1818.
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Affiliation(s)
- Dipanjan Mukherjee
- Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India.
| | - Priya Singh
- Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India.
| | - Tatini Rakshit
- Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India.
| | - Theja P Puthiya-Purayil
- Laboratory of Self-Assembled Biomaterials and Translational Research, National Center for Biological Science, Rajiv Gandhi Nagar, Kodigehalli, Bengaluru, Karnataka 560097, India
| | - Praveen Kumar Vemula
- Laboratory of Self-Assembled Biomaterials and Translational Research, National Center for Biological Science, Rajiv Gandhi Nagar, Kodigehalli, Bengaluru, Karnataka 560097, India
| | - Jhimli Sengupta
- Department of Chemistry, West Bengal State University, Barasat, Kolkata 700126, India.
| | - Ranjan Das
- Department of Chemistry, West Bengal State University, Barasat, Kolkata 700126, India.
| | - Samir Kumar Pal
- Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India.
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11
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Höfig H, Yukhnovets O, Remes C, Kempf N, Katranidis A, Kempe D, Fitter J. Brightness-gated two-color coincidence detection unravels two distinct mechanisms in bacterial protein translation initiation. Commun Biol 2019; 2:459. [PMID: 31840104 PMCID: PMC6897966 DOI: 10.1038/s42003-019-0709-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 11/22/2019] [Indexed: 01/19/2023] Open
Abstract
Life on the molecular scale is based on a complex interplay of biomolecules under which the ability of binding is crucial. Fluorescence based two-color coincidence detection (TCCD) is commonly used to characterize molecular binding, but suffers from an underestimation of coincident events. Here, we introduce a brightness-gated TCCD which overcomes this limitation and benchmark our approach with two custom-made calibration samples. Applied to a cell-free protein synthesis assay, brightness-gated TCCD unraveled a previously disregarded mode of translation initiation in bacteria.
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Affiliation(s)
- Henning Höfig
- I. Physikalisches Institut (IA), RWTH Aachen University, Aachen, Germany
- Institute of Complex Systems ICS-5, Forschungszentrum Jülich, Jülich, Germany
| | - Olessya Yukhnovets
- I. Physikalisches Institut (IA), RWTH Aachen University, Aachen, Germany
- Institute of Complex Systems ICS-5, Forschungszentrum Jülich, Jülich, Germany
| | - Cristina Remes
- Institute of Complex Systems ICS-5, Forschungszentrum Jülich, Jülich, Germany
- Present Address: Max Planck Institute for the Biology of Ageing, Cologne, Germany
| | - Noemie Kempf
- Institute of Complex Systems ICS-5, Forschungszentrum Jülich, Jülich, Germany
- Present Address: Laboratoire de Biologie Moléculaire Eucaryote LBME—Center for Integrative Biology CBI, University of Toulouse, Toulouse, France
| | | | - Daryan Kempe
- I. Physikalisches Institut (IA), RWTH Aachen University, Aachen, Germany
- Present Address: EMBL Australia, Single Molecule Science Node, School of Medical Sciences, University of New South Wales, Sydney, NSW Australia
| | - Jörg Fitter
- I. Physikalisches Institut (IA), RWTH Aachen University, Aachen, Germany
- Institute of Complex Systems ICS-5, Forschungszentrum Jülich, Jülich, Germany
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12
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Junker NO, Vaghefikia F, Albarghash A, Höfig H, Kempe D, Walter J, Otten J, Pohl M, Katranidis A, Wiegand S, Fitter J. Impact of Molecular Crowding on Translational Mobility and Conformational Properties of Biological Macromolecules. J Phys Chem B 2019; 123:4477-4486. [PMID: 31059260 DOI: 10.1021/acs.jpcb.9b01239] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Effects of molecular crowding on structural and dynamical properties of biological macromolecules do depend on the concentration of crowding agents but also on the molecular mass and the structural compactness of the crowder molecules. By employing fluorescence correlation spectroscopy (FCS), we investigated the translational mobility of several biological macromolecules ranging from 17 kDa to 2.7 MDa. Polyethylene glycol and Ficoll polymers of different molecular masses were used in buffer solutions to mimic a crowded environment. The reduction in translational mobility of the biological tracer molecules was analyzed as a function of crowder volume fractions and was generally more pronounced in PEG as compared to Ficoll solutions. For several crowding conditions, we observed a molecular sieving effect, in which the diffusion coefficient of larger tracer molecules is reduced to a larger extent than predicted by the Stokes-Einstein relation. By employing a FRET-based biosensor, we also showed that a multiprotein complex is significantly compacted in the presence of macromolecular crowders. Importantly, with respect to sensor in vivo applications, ligand concentration determining sensors would need a crowding specific calibration in order to deliver correct cytosolic ligand concentration.
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Affiliation(s)
- Niklas O Junker
- I. Physikalisches Institut (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Farzaneh Vaghefikia
- I. Physikalisches Institut (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Alyazan Albarghash
- I. Physikalisches Institut (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Henning Höfig
- I. Physikalisches Institut (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Daryan Kempe
- I. Physikalisches Institut (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | - Julia Walter
- I. Physikalisches Institut (IA) , RWTH Aachen University , 52074 Aachen , Germany
| | | | | | | | - Simone Wiegand
- Physikalische Chemie , Universität zu Köln , 50923 Köln , Germany
| | - Jörg Fitter
- I. Physikalisches Institut (IA) , RWTH Aachen University , 52074 Aachen , Germany
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13
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Katranidis A, Fitter J. Single-Molecule Techniques and Cell-Free Protein Synthesis: A Perfect Marriage. Anal Chem 2019; 91:2570-2576. [PMID: 30648382 DOI: 10.1021/acs.analchem.8b03855] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Single-molecule techniques are currently an essential tool to study conformational changes as well as the synthesis and folding of proteins. However, the preparation of suitable protein samples is often time-consuming and demanding. The rapid development of cell-free protein synthesis over the last few years opened new perspectives for fast and easy sample preparation, but this was not fully exploited until now. Here, we take a look at the advancements in sample preparation as well as in the development of technical approaches and analytical tools, which unavoidably lead to the combination of single-molecule techniques and cell-free protein synthesis. It is an ideal combination that can unlock the full potential of studying complex biological processes in the near future.
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Affiliation(s)
| | - Jörg Fitter
- Forschungszentrum Jülich , Institute of Complex Systems ICS-5, Jülich , Germany.,RWTH Aachen , I. Physikalisches Institut (IA) , Aachen , Germany
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14
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Ingargiola A, Weiss S, Lerner E. Monte Carlo Diffusion-Enhanced Photon Inference: Distance Distributions and Conformational Dynamics in Single-Molecule FRET. J Phys Chem B 2018; 122:11598-11615. [PMID: 30252475 DOI: 10.1021/acs.jpcb.8b07608] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Single-molecule Förster resonance energy transfer (smFRET) is utilized to study the structure and dynamics of many biomolecules, such as proteins, DNA, and their various complexes. The structural assessment is based on the well-known Förster relationship between the measured efficiency of energy transfer between a donor (D) and an acceptor (A) dye and the distance between them. Classical smFRET analysis methods called photon distribution analysis (PDA) take into account photon shot-noise, D-A distance distribution, and, more recently, interconversion between states in order to extract accurate distance information. It is known that rapid D-A distance fluctuations on the order of the D lifetime (or shorter) can increase the measured mean FRET efficiency and thus decrease the estimated D-A distance. Nonetheless, this effect has been so far neglected in smFRET experiments, potentially leading to biases in estimated distances. Here we introduce a PDA approach dubbed Monte Carlo diffusion-enhanced photon inference (MC-DEPI). MC-DEPI recolor detected photons of smFRET experiments taking into account dynamics of D-A distance fluctuations, multiple interconverting states, and photoblinking. Using this approach, we show how different underlying conditions may yield identical FRET histograms and how the additional information from fluorescence decays helps in distinguishing between the different conditions. We also introduce a machine learning fitting approach for retrieving the D-A distance distribution, decoupled from the above-mentioned effects. We show that distance interpretation of smFRET experiments of even the simplest dsDNA is nontrivial and requires decoupling the effects of rapid D-A distance fluctuations on FRET in order to avoid systematic biases in the estimation of the D-A distance distribution.
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Affiliation(s)
- Antonino Ingargiola
- Department of Chemistry and Biochemistry , University of California Los Angeles , Los Angeles , California , United States
| | - Shimon Weiss
- Department of Chemistry and Biochemistry , University of California Los Angeles , Los Angeles , California , United States
| | - Eitan Lerner
- Department of Chemistry and Biochemistry , University of California Los Angeles , Los Angeles , California , United States.,Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences , The Hebrew University , Jerusalem , Israel
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15
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Lerner E, Ingargiola A, Weiss S. Characterizing highly dynamic conformational states: The transcription bubble in RNAP-promoter open complex as an example. J Chem Phys 2018; 148:123315. [PMID: 29604842 DOI: 10.1063/1.5004606] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Bio-macromolecules carry out complicated functions through structural changes. To understand their mechanism of action, the structure of each step has to be characterized. While classical structural biology techniques allow the characterization of a few "structural snapshots" along the enzymatic cycle (usually of stable conformations), they do not cover all (and often fast interconverting) structures in the ensemble, where each may play an important functional role. Recently, several groups have demonstrated that structures of different conformations in solution could be solved by measuring multiple distances between different pairs of residues using single-molecule Förster resonance energy transfer (smFRET) and using them as constrains for hybrid/integrative structural modeling. However, this approach is limited in cases where the conformational dynamics is faster than the technique's temporal resolution. In this study, we combine existing tools that elucidate sub-millisecond conformational dynamics together with hybrid/integrative structural modeling to study the conformational states of the transcription bubble in the bacterial RNA polymerase-promoter open complex (RPo). We measured microsecond alternating laser excitation-smFRET of differently labeled lacCONS promoter dsDNA constructs. We used a combination of burst variance analysis, photon-by-photon hidden Markov modeling, and the FRET-restrained positioning and screening approach to identify two conformational states for RPo. The experimentally derived distances of one conformational state match the known crystal structure of bacterial RPo. The experimentally derived distances of the other conformational state have characteristics of a scrunched RPo. These findings support the hypothesis that sub-millisecond dynamics in the transcription bubble are responsible for transcription start site selection.
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Affiliation(s)
- Eitan Lerner
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA
| | - Antonino Ingargiola
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA
| | - Shimon Weiss
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA
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16
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Single-Molecule Studies on a FRET Biosensor: Lessons from a Comparison of Fluorescent Protein Equipped versus Dye-Labeled Species. Molecules 2018; 23:molecules23123105. [PMID: 30486450 PMCID: PMC6320824 DOI: 10.3390/molecules23123105] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 11/23/2018] [Accepted: 11/24/2018] [Indexed: 11/16/2022] Open
Abstract
Bacterial periplasmic binding proteins (PBPs) undergo a pronounced ligand-induced conformational change which can be employed to monitor ligand concentrations. The most common strategy to take advantage of this conformational change for a biosensor design is to use a Förster resonance energy transfer (FRET) signal. This can be achieved by attaching either two fluorescent proteins (FPs) or two organic fluorescent dyes of different colors to the PBPs in order to obtain an optical readout signal which is closely related to the ligand concentration. In this study we compare a FP-equipped and a dye-labeled version of the glucose/galactose binding protein MglB at the single-molecule level. The comparison demonstrates that changes in the FRET signal upon glucose binding are more pronounced for the FP-equipped sensor construct as compared to the dye-labeled analog. Moreover, the FP-equipped sensor showed a strong increase of the FRET signal under crowding conditions whereas the dye-labeled sensor was not influenced by crowding. The choice of a labeling scheme should therefore be made depending on the application of a FRET-based sensor.
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17
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Qu S, Liu C, Liu Q, Wu W, Du B, Wang J. Solvent effect on FRET spectroscopic ruler. J Chem Phys 2018; 148:123331. [PMID: 29604875 DOI: 10.1063/1.5004205] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
A discrepancy has emerged in recent years between single-molecule Förster resonance energy transfer (smFRET) measurements and small angle X-ray scattering (SAXS) or small angle neutron scattering experiments in the study of unfolded or intrinsically disordered proteins in denaturing solutions. Despite significant advances that have been made in identifying various factors which may have contributed to the manifestation of the so-called smFRET-SAXS discrepancy, no consensus has been reached so far on its original source or eventual resolution. In this study, we investigate this problem from the perspective of the solvent effect on FRET spectroscopic ruler (SEFSR), a generic term we use to describe various solvent-dependent factors affecting the accuracy of the FRET experimental method that is known as a "spectroscopic ruler." Some factors belonging to SEFSR, such as direct dye-solvent interaction and labeling configuration, seem to have not received due attention regarding their significance in contributing to the discrepancy. We identify SEFSR by measuring a rigid segment of a double-stranded DNA in various solutions using the smFRET method and evaluate its relative importance in smFRET experiments by measuring segments of a single-stranded DNA and polyethylene glycol (PEG) in solutions. We find that SEFSR can produce non-negligible FRET-inferred interdye distance changes in various solutions, with an intensity following the Hofmeister series in ionic solutions and dependent on labeling configurations. SEFSR is found to be significant in GuHCl and urea solutions, which can fully cover the apparent expansion signal of dye-labeled PEG. Our findings suggest that SEFSR may have played an important role in contributing to the smFRET-SAXS discrepancy.
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Affiliation(s)
- Songyuan Qu
- College of Physics, Jilin University, Changchun, Jilin 130012, People's Republic of China
| | - Chuanbo Liu
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, People's Republic of China
| | - Qiong Liu
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, People's Republic of China
| | - Wei Wu
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, People's Republic of China
| | - Baoji Du
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, People's Republic of China
| | - Jin Wang
- College of Physics, Jilin University, Changchun, Jilin 130012, People's Republic of China
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18
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Eilert T, Kallis E, Nagy J, Röcker C, Michaelis J. Complete Kinetic Theory of FRET. J Phys Chem B 2018; 122:11677-11694. [DOI: 10.1021/acs.jpcb.8b07719] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Tobias Eilert
- Institute of Biophysics, Ulm University, Albert-Einstein-Allee 11, Ulm 89081, Germany
| | - Eleni Kallis
- Institute of Biophysics, Ulm University, Albert-Einstein-Allee 11, Ulm 89081, Germany
| | - Julia Nagy
- Center for Translational Imaging (MoMAN), Ulm University, Albert-Einstein-Allee 11, Ulm 89091, Germany
| | - Carlheinz Röcker
- Institute of Biophysics, Ulm University, Albert-Einstein-Allee 11, Ulm 89081, Germany
| | - Jens Michaelis
- Institute of Biophysics, Ulm University, Albert-Einstein-Allee 11, Ulm 89081, Germany
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19
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Vandenberk N, Barth A, Borrenberghs D, Hofkens J, Hendrix J. Evaluation of Blue and Far-Red Dye Pairs in Single-Molecule Förster Resonance Energy Transfer Experiments. J Phys Chem B 2018. [DOI: 10.1021/acs.jpcb.8b00108] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Niels Vandenberk
- Laboratory for Photochemistry and Spectroscopy, Division for Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
| | - Anders Barth
- Physical Chemistry, Department of Chemistry, Munich Center for Integrated Protein Science, Nanosystems Initiative Munich and Centre for Nanoscience, Ludwig-Maximilians-Universität München, 80539 Munich, Germany
| | - Doortje Borrenberghs
- Laboratory for Photochemistry and Spectroscopy, Division for Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
| | - Johan Hofkens
- Laboratory for Photochemistry and Spectroscopy, Division for Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
| | - Jelle Hendrix
- Laboratory for Photochemistry and Spectroscopy, Division for Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
- Dynamic Bioimaging Lab, Advanced Optical Microscopy Centre and Biomedical Research Institute, Hasselt University, Agoralaan C (BIOMED), Diepenbeek, B-3590, Belgium
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20
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Sadoine M, Cerminara M, Gerrits M, Fitter J, Katranidis A. Cotranslational Incorporation into Proteins of a Fluorophore Suitable for smFRET Studies. ACS Synth Biol 2018; 7:405-411. [PMID: 29370697 DOI: 10.1021/acssynbio.7b00433] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Single-molecule FRET (smFRET) is a powerful tool to investigate conformational changes of biological molecules. In general, smFRET studies require protein samples that are site-specifically double-labeled with a pair of donor and acceptor fluorophores. The common approaches to produce such samples cannot be applied when studying the synthesis and folding of the polypeptide chain on the ribosome. The best strategy is to incorporate two fluorescent amino acids cotranslationally using cell-free protein synthesis systems. Here, we demonstrate the cotranslational site-specific incorporation into a model protein of Atto633, a dye with excellent photophysical properties, suitable for single molecule spectroscopy, together with a second dye using a combination of the sense cysteine and the nonsense amber codon. In this work we show that cotranslational incorporation of good fluorophores into proteins is a viable strategy to produce suitable samples for smFRET studies.
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Affiliation(s)
- Mayuri Sadoine
- Forschungszentrum Jülich, Institute of Complex Systems
ICS-5, 52428 Jülich, Germany
| | - Michele Cerminara
- Forschungszentrum Jülich, Institute of Complex Systems
ICS-5, 52428 Jülich, Germany
| | - Michael Gerrits
- Biocatalysis
Group, Department of Chemistry, Technische Universität Berlin, 10623 Berlin, Germany
| | - Jörg Fitter
- Forschungszentrum Jülich, Institute of Complex Systems
ICS-5, 52428 Jülich, Germany
- RWTH Aachen University, I.Physikalisches
Institut (IA), 52062 Aachen, Germany
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21
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Matveeva AG, Nekrasov VM, Maryasov AG. Analytical solution of the PELDOR inverse problem using the integral Mellin transform. Phys Chem Chem Phys 2018; 19:32381-32388. [PMID: 29185558 DOI: 10.1039/c7cp04059h] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We describe a new model-free approach to solve the inverse problem in pulsed double electron-electron resonance (PELDOR, also known as DEER) spectroscopy and obtain the distance distribution function between two radicals from time-domain PELDOR data. The approach is based on analytical solutions of the Fredholm integral equations of the first kind using integral Mellin transforms to provide the distance distribution function directly. The approach appears to confine the noise in the computed distance distribution to short distances and does not introduce systematic distortions. Thus, the proposed analysis method can be a useful supplement to current methods to determine complicated distance distributions.
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Affiliation(s)
- Anna G Matveeva
- Voevodsky Institute of Chemical Kinetics and Combustion, 630090 Novosibirsk, Russia.
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22
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Sadoine M, Cerminara M, Kempf N, Gerrits M, Fitter J, Katranidis A. Selective Double-Labeling of Cell-Free Synthesized Proteins for More Accurate smFRET Studies. Anal Chem 2017; 89:11278-11285. [DOI: 10.1021/acs.analchem.7b01639] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mayuri Sadoine
- Forschungszentrum
Jülich, Institute of Complex Systems ICS-5, 52425 Jülich, Germany
| | - Michele Cerminara
- Forschungszentrum
Jülich, Institute of Complex Systems ICS-5, 52425 Jülich, Germany
| | - Noémie Kempf
- Forschungszentrum
Jülich, Institute of Complex Systems ICS-5, 52425 Jülich, Germany
| | | | - Jörg Fitter
- Forschungszentrum
Jülich, Institute of Complex Systems ICS-5, 52425 Jülich, Germany
- 1. Physikalisches
Institut (IA), RWTH Aachen, 52062 Aachen, Germany
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23
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Peulen TO, Opanasyuk O, Seidel CAM. Combining Graphical and Analytical Methods with Molecular Simulations To Analyze Time-Resolved FRET Measurements of Labeled Macromolecules Accurately. J Phys Chem B 2017; 121:8211-8241. [PMID: 28709377 PMCID: PMC5592652 DOI: 10.1021/acs.jpcb.7b03441] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
![]()
Förster resonance energy transfer
(FRET) measurements from
a donor, D, to an acceptor, A, fluorophore are frequently used in vitro and in live cells to reveal information on the
structure and dynamics of DA labeled macromolecules. Accurate descriptions
of FRET measurements by molecular models are complicated because the
fluorophores are usually coupled to the macromolecule via flexible
long linkers allowing for diffusional exchange between multiple states
with different fluorescence properties caused by distinct environmental
quenching, dye mobilities, and variable DA distances. It is often
assumed for the analysis of fluorescence intensity decays that DA
distances and D quenching are uncorrelated (homogeneous quenching
by FRET) and that the exchange between distinct fluorophore states
is slow (quasistatic). This allows us to introduce the FRET-induced
donor decay, εD(t), a function solely
depending on the species fraction distribution of the rate constants
of energy transfer by FRET, for a convenient joint analysis of fluorescence
decays of FRET and reference samples by integrated graphical and analytical
procedures. Additionally, we developed a simulation toolkit to model
dye diffusion, fluorescence quenching by the protein surface, and
FRET. A benchmark study with simulated fluorescence decays of 500
protein structures demonstrates that the quasistatic homogeneous model
works very well and recovers for single conformations the average
DA distances with an accuracy of < 2%. For more complex
cases, where proteins adopt multiple conformations with significantly
different dye environments (heterogeneous case), we introduce a general
analysis framework and evaluate its power in resolving heterogeneities
in DA distances. The developed fast simulation methods, relying on
Brownian dynamics of a coarse-grained dye in its sterically accessible
volume, allow us to incorporate structural information in the decay
analysis for heterogeneous cases by relating dye states with protein
conformations to pave the way for fluorescence and FRET-based dynamic
structural biology. Finally, we present theories and simulations to
assess the accuracy and precision of steady-state and time-resolved
FRET measurements in resolving DA distances on the single-molecule
and ensemble level and provide a rigorous framework for estimating
approximation, systematic, and statistical errors.
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Affiliation(s)
- Thomas-Otavio Peulen
- Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität , Universitätsstraße 1, 40225 Düsseldorf, Germany
| | - Oleg Opanasyuk
- Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität , Universitätsstraße 1, 40225 Düsseldorf, Germany
| | - Claus A M Seidel
- Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität , Universitätsstraße 1, 40225 Düsseldorf, Germany
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24
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Kempe D, Cerminara M, Poblete S, Schöne A, Gabba M, Fitter J. Single-Molecule FRET Measurements in Additive-Enriched Aqueous Solutions. Anal Chem 2016; 89:694-702. [PMID: 27966879 DOI: 10.1021/acs.analchem.6b03147] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The addition of high amounts of chemical denaturants, salts, viscosity enhancers or macro-molecular crowding agents has an impact on the physical properties of buffer solutions. Among others, the (microscopic) viscosity, the refractive index, the dielectric constant, and the ionic strength can be affected. Here, we systematically evaluate the importance of solvent characteristics with respect to single-molecule FRET (smFRET) data. First, we present a confocal based method for the determination of fluorescence quantum yields to facilitate a fast characterization of smFRET-samples at sub-nM-concentrations. As a case study, we analyze smFRET data of structurally rigid, double-stranded DNA-oligonucleotides in aqueous buffer and in buffers with specific amounts of glycerol, guanidine hydrochloride (GdnHCl), and sodium chloride (NaCl) added. We show that the calculation of interdye distances, without taking into account solvent-induced spectral and photophysical changes of the labels, leads to deviations of up to 4 Å from the real interdye distances. Additionally, we demonstrate that electrostatic dye-dye repulsions are negligible for the interdye distance regime considered here (>50 Å). Finally, we use our approach to validate the further compaction of the already unfolded state of phosphoglycerate kinase (PGK) with decreasing denaturant concentrations, a mechanism known as coil-globule transition.
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Affiliation(s)
- Daryan Kempe
- AG Biophysik, I. Physikalisches Institut (IA), RWTH Aachen University , 52056 Aachen, Germany
| | | | | | | | | | - Jörg Fitter
- AG Biophysik, I. Physikalisches Institut (IA), RWTH Aachen University , 52056 Aachen, Germany
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25
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Dimura M, Peulen TO, Hanke CA, Prakash A, Gohlke H, Seidel CA. Quantitative FRET studies and integrative modeling unravel the structure and dynamics of biomolecular systems. Curr Opin Struct Biol 2016; 40:163-185. [PMID: 27939973 DOI: 10.1016/j.sbi.2016.11.012] [Citation(s) in RCA: 113] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 11/11/2016] [Accepted: 11/11/2016] [Indexed: 01/11/2023]
Abstract
Förster Resonance Energy Transfer (FRET) combined with single-molecule spectroscopy probes macromolecular structure and dynamics and identifies coexisting conformational states. We review recent methodological developments in integrative structural modeling by satisfying spatial restraints on networks of FRET pairs (hybrid-FRET). We discuss procedures to incorporate prior structural knowledge and to obtain optimal distance networks. Finally, a workflow for hybrid-FRET is presented that automates integrative structural modeling and experiment planning to put hybrid-FRET on rails. To test this workflow, we simulate realistic single-molecule experiments and resolve three protein conformers, exchanging at 30μs and 10ms, with accuracies of 1-3Å RMSD versus the target structure. Incorporation of data from other spectroscopies and imaging is also discussed.
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Affiliation(s)
- Mykola Dimura
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany; Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Thomas O Peulen
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Christian A Hanke
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Aiswaria Prakash
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Claus Am Seidel
- Chair for Molecular Physical Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany.
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Wang S, Vyas R, Dwyer C. Fluorescent taggants with temporally coded signatures. OPTICS EXPRESS 2016; 24:15528-15545. [PMID: 27410827 DOI: 10.1364/oe.24.015528] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In this paper, resonance energy transfer (RET) networks between chromophores are used to implement fluorescent taggants with temporally coded signatures. Because the temporal signature of such a fluorescent taggant is a phase-type distribution defined by the geometry of its RET network, the taggant design is not constrained by resolvable dyes and has a significantly larger coding capacity than spectrally or lifetime coded fluorescent taggants. Meanwhile, the detection process becomes highly efficient when the signatures are coded in the time domain. The taggant identification method is based on the multinomial distribution of detected photons and Maximum Likelihood Estimation, which guarantees high accuracy even with only a few hundred photons and also applies to a mixture of taggants in multiplex detection. Therefore, these temporally coded fluorescent taggants have great potential for both in situ and Lidar applications.
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Hildebrandt LL, Preus S, Birkedal V. Quantitative single molecule FRET efficiencies using TIRF microscopy. Faraday Discuss 2015; 184:131-42. [PMID: 26416760 DOI: 10.1039/c5fd00100e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Förster resonance energy transfer (FRET) microscopy at the single molecule level has the potential to yield information on intra and intermolecular distances within the 2-10 nm range of molecules or molecular complexes that undergo frequent conformation changes. A pre-requirement for obtaining accurate distance information is to determine quantitative instrument independent FRET efficiency values. Here, we applied and evaluated a procedure to determine quantitative FRET efficiencies directly from individual fluorescence time traces of surface immobilized DNA molecules without the need for external calibrants. To probe the robustness of the approach over a wide range of FRET efficiencies we used a set of doubly labelled double stranded DNA samples, where the acceptor position was varied systematically. Interestingly, we found that fluorescence contributions arising from direct acceptor excitation following donor excitation are intrinsically taken into account in these conditions as other correction factors can compensate for inaccurate values of these parameters. We give here guidelines, that can be used through tools within the iSMS software (), for determining quantitative FRET and assess uncertainties linked with the procedure. Our results provide insights into the experimental parameters governing quantitative FRET determination, which is essential for obtaining accurate structural information from a wide range of biomolecules.
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Affiliation(s)
- Lasse L Hildebrandt
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark.
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Special issue: single molecule techniques. Molecules 2015; 20:7772-4. [PMID: 26007165 PMCID: PMC6272226 DOI: 10.3390/molecules20057772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Accepted: 04/27/2015] [Indexed: 12/04/2022] Open
Abstract
Technological advances in the detection and manipulation of single molecules have enabled new insights into the function, structure and interactions of biomolecules. This Special Issue was launched to account for the rapid progress in the field of “Single Molecule Techniques”. Four original research articles and seven review articles provide an introduction, as well as an in-depth discussion, of technical developments that are indispensable for the characterization of individual biomolecules. Fluorescence microscopy takes center stage in this Special Issue because it is one of the most sensitive and flexible techniques, which has been adapted in many variations to the specific demands of single molecule analysis. Two additional articles are dedicated to single molecule detection based on atomic force microscopy.
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