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Pfukwa NBC, Rautenbach M, Hunt NT, Olaoye OO, Kumar V, Parker AW, Minnes L, Neethling PH. Temperature-Induced Effects on the Structure of Gramicidin S. J Phys Chem B 2023; 127:3774-3786. [PMID: 37125750 DOI: 10.1021/acs.jpcb.2c06115] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
We report on the structure of Gramicidin S (GS) in a model membrane mimetic environment represented by the amphipathic solvent 1-octanol using one-dimensional (1D) and two-dimensional (2D) IR spectroscopy. To explore potential structural changes of GS, we also performed a series of spectroscopic measurements at differing temperatures. By analyzing the amide I band and using 2D-IR spectral changes, results could be associated to the disruption of aggregates/oligomers, as well as structural and conformational changes happening in the concentrated solution of GS. The ability of 2D-IR to enable differentiation in melting transitions of oligomerized GS structures is attributed to the sensitivity of the technique to vibrational coupling. Two melting transition temperatures were identified; at Tm1 in the range 41-47 °C where the GS aggregates/oligomers disassemble and at Tm2 = 57 ± 2 °C where there is significant change involving GS β-sheet-type hydrogen bonds, whereby it is proposed that there is loss of interpeptide hydrogen bonds and we are left with mainly intrapeptide β-sheet and β-turn hydrogen bonds of the smaller oligomers. Further analysis with quantum mechanical/molecular mechanics (QM/MM) simulations and second derivative results highlighted the participation of active GS side chains. Ultimately, this work contributes toward understanding the GS structure and the formulation of GS analogues with improved bioactivity.
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Affiliation(s)
- Ngaatendwe B C Pfukwa
- Department of Physics, Laser Research Institute, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
| | - Marina Rautenbach
- BIOPEP Peptide Group, Department of Biochemistry, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
| | - Neil T Hunt
- Department of Chemistry and York Biomedical Research Institute, University of York, Heslington, York YO10 5DD, U.K
| | - Olufemi O Olaoye
- Department of Physics, Laser Research Institute, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
| | - Vikas Kumar
- BIOPEP Peptide Group, Department of Biochemistry, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
| | - Anthony W Parker
- Department of Physics, Laser Research Institute, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
- Research Complex at Harwell, Rutherford Appleton Laboratory, STFC Central Laser Facility, Harwell Science and Innovation Campus, Didcot, Oxon OX11 0QX, U.K
| | - Lucy Minnes
- Department of Physics, University of Strathclyde, SUPA, 107 Rottenrow East, Glasgow G4 0NG, U.K
| | - Pieter H Neethling
- Department of Physics, Laser Research Institute, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
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2
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Price DA, Wedamulla P, Hill TD, Loth TM, Moran SD. The polarization dependence of 2D IR cross-peaks distinguishes parallel-stranded and antiparallel-stranded DNA G-quadruplexes. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 267:120596. [PMID: 34801392 DOI: 10.1016/j.saa.2021.120596] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 11/01/2021] [Accepted: 11/04/2021] [Indexed: 06/13/2023]
Abstract
Guanine-rich nucleic acid sequences have a tendency to form four-stranded non-canonical motifs known as G-quadruplexes. These motifs may adopt a wide range of structures characterized by size, strand orientation, guanine base conformation, and fold topology. Using three K+-bound model systems, we show that vibrational coupling between guanine C6 = O and ring modes varies between parallel-stranded and antiparallel-stranded G-quadruplexes, and that such structures can be distinguished by comparison of the polarization dependences of cross-peaks in their two-dimensional infrared (2D IR) spectra. Combined with previously defined vibrational frequency trends, this analysis reveals key features of a 30-nucleotide unimolecular variant of the Bcl-2 proximal promoter that are consistent with its reported structure. This study shows that 2D IR spectroscopy is a convenient method for analyzing G-quadruplex structures that can be applied to complex sequences where traditional high-resolution methods are limited by solubility and disorder.
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Affiliation(s)
- David A Price
- School of Chemical and Biomolecular Sciences, Southern Illinois University Carbondale, 1245 Lincoln Drive MC 4409, Carbondale, IL 62901, United States
| | - Poornima Wedamulla
- School of Chemical and Biomolecular Sciences, Southern Illinois University Carbondale, 1245 Lincoln Drive MC 4409, Carbondale, IL 62901, United States
| | - Tayler D Hill
- School of Chemical and Biomolecular Sciences, Southern Illinois University Carbondale, 1245 Lincoln Drive MC 4409, Carbondale, IL 62901, United States
| | - Taylor M Loth
- School of Chemical and Biomolecular Sciences, Southern Illinois University Carbondale, 1245 Lincoln Drive MC 4409, Carbondale, IL 62901, United States
| | - Sean D Moran
- School of Chemical and Biomolecular Sciences, Southern Illinois University Carbondale, 1245 Lincoln Drive MC 4409, Carbondale, IL 62901, United States.
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3
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Tumbic GW, Hossan MY, Thielges MC. Protein Dynamics by Two-Dimensional Infrared Spectroscopy. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2021; 14:299-321. [PMID: 34314221 PMCID: PMC8713465 DOI: 10.1146/annurev-anchem-091520-091009] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Proteins function as ensembles of interconverting structures. The motions span from picosecond bond rotations to millisecond and longer subunit displacements. Characterization of functional dynamics on all spatial and temporal scales remains challenging experimentally. Two-dimensional infrared spectroscopy (2D IR) is maturing as a powerful approach for investigating proteins and their dynamics. We outline the advantages of IR spectroscopy, describe 2D IR and the information it provides, and introduce vibrational groups for protein analysis. We highlight example studies that illustrate the power and versatility of 2D IR for characterizing protein dynamics and conclude with a brief discussion of the outlook for biomolecular 2D IR.
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Affiliation(s)
- Goran W Tumbic
- Department of Chemistry, Indiana University, Bloomington, Indiana 47401, USA;
| | - Md Yeathad Hossan
- Department of Chemistry, Indiana University, Bloomington, Indiana 47401, USA;
| | - Megan C Thielges
- Department of Chemistry, Indiana University, Bloomington, Indiana 47401, USA;
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4
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Su Z, Goodall B, Leitch JJ, Lipkowski J. Ion transport mechanism in gramicidin A channels formed in floating bilayer lipid membranes supported on gold electrodes. Electrochim Acta 2021. [DOI: 10.1016/j.electacta.2021.137892] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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5
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Foreman-Ortiz IU, Liang D, Laudadio ED, Calderin JD, Wu M, Keshri P, Zhang X, Schwartz MP, Hamers RJ, Rotello VM, Murphy CJ, Cui Q, Pedersen JA. Anionic nanoparticle-induced perturbation to phospholipid membranes affects ion channel function. Proc Natl Acad Sci U S A 2020; 117:27854-27861. [PMID: 33106430 PMCID: PMC7668003 DOI: 10.1073/pnas.2004736117] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Understanding the mechanisms of nanoparticle interaction with cell membranes is essential for designing materials for applications such as bioimaging and drug delivery, as well as for assessing engineered nanomaterial safety. Much attention has focused on nanoparticles that bind strongly to biological membranes or induce membrane damage, leading to adverse impacts on cells. More subtle effects on membrane function mediated via changes in biophysical properties of the phospholipid bilayer have received little study. Here, we combine electrophysiology measurements, infrared spectroscopy, and molecular dynamics simulations to obtain insight into a mode of nanoparticle-mediated modulation of membrane protein function that was previously only hinted at in prior work. Electrophysiology measurements on gramicidin A (gA) ion channels embedded in planar suspended lipid bilayers demonstrate that anionic gold nanoparticles (AuNPs) reduce channel activity and extend channel lifetimes without disrupting membrane integrity, in a manner consistent with changes in membrane mechanical properties. Vibrational spectroscopy indicates that AuNP interaction with the bilayer does not perturb the conformation of membrane-embedded gA. Molecular dynamics simulations reinforce the experimental findings, showing that anionic AuNPs do not directly interact with embedded gA channels but perturb the local properties of lipid bilayers. Our results are most consistent with a mechanism in which anionic AuNPs disrupt ion channel function in an indirect manner by altering the mechanical properties of the surrounding bilayer. Alteration of membrane mechanical properties represents a potentially important mechanism by which nanoparticles induce biological effects, as the function of many embedded membrane proteins depends on phospholipid bilayer biophysical properties.
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Affiliation(s)
| | - Dongyue Liang
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706
- Department of Chemistry, Boston University, Boston, MA 02215
| | | | - Jorge D Calderin
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706
| | - Meng Wu
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Puspam Keshri
- Department of Chemistry, University of Massachusetts, Amherst, MA 01003
| | - Xianzhi Zhang
- Department of Chemistry, University of Massachusetts, Amherst, MA 01003
| | - Michael P Schwartz
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706
| | - Robert J Hamers
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706
| | - Vincent M Rotello
- Department of Chemistry, University of Massachusetts, Amherst, MA 01003
| | - Catherine J Murphy
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Qiang Cui
- Department of Chemistry, Boston University, Boston, MA 02215
- Department of Physics, Boston University, Boston, MA 02215
- Department of Biomedical Engineering, Boston University, Boston, MA 02215
| | - Joel A Pedersen
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706;
- Department of Soil Science, University of Wisconsin-Madison, Madison, WI 53706
- Department of Civil & Environmental Engineering, University of Wisconsin-Madison, Madison, WI 53706
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6
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Coordination to lanthanide ions distorts binding site conformation in calmodulin. Proc Natl Acad Sci U S A 2018; 115:E3126-E3134. [PMID: 29545272 DOI: 10.1073/pnas.1722042115] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The Ca2+-sensing protein calmodulin (CaM) is a popular model of biological ion binding since it is both experimentally tractable and essential to survival in all eukaryotic cells. CaM modulates hundreds of target proteins and is sensitive to complex patterns of Ca2+ exposure, indicating that it functions as a sophisticated dynamic transducer rather than a simple on/off switch. Many details of this transduction function are not well understood. Fourier transform infrared (FTIR) spectroscopy, ultrafast 2D infrared (2D IR) spectroscopy, and electronic structure calculations were used to probe interactions between bound metal ions (Ca2+ and several trivalent lanthanide ions) and the carboxylate groups in CaM's EF-hand ion-coordinating sites. Since Tb3+ is commonly used as a luminescent Ca2+ analog in studies of protein-ion binding, it is important to characterize distinctions between the coordination of Ca2+ and the lanthanides in CaM. Although functional assays indicate that Tb3+ fully activates many Ca2+-dependent proteins, our FTIR spectra indicate that Tb3+, La3+, and Lu3+ disrupt the bidentate coordination geometry characteristic of the CaM binding sites' strongly conserved position 12 glutamate residue. The 2D IR spectra indicate that, relative to the Ca2+-bound form, lanthanide-bound CaM exhibits greater conformational flexibility and larger structural fluctuations within its binding sites. Time-dependent 2D IR lineshapes indicate that binding sites in Ca2+-CaM occupy well-defined configurations, whereas binding sites in lanthanide-bound-CaM are more disordered. Overall, the results show that binding to lanthanide ions significantly alters the conformation and dynamics of CaM's binding sites.
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7
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Time-resolved measurements of an ion channel conformational change driven by a membrane phase transition. Proc Natl Acad Sci U S A 2017; 114:10840-10845. [PMID: 28973859 DOI: 10.1073/pnas.1708070114] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Using temperature-jump infrared spectroscopy, we are able to trigger a gel-to-fluid phase transition in lipid vesicles and monitor in real time how a membrane protein responds to structural changes in the membrane. The melting of lipid domains in 1,2-dimyristoyl-sn-glycero-3-phosphocholine vesicles is observed to occur in as fast as 50 ns, with a temperature dependence characteristic of critical slowing. Gramicidin D (gD) added to the membrane responds primarily to the change in thickness of the membrane on a timescale coincident with the membrane melting. Using structure-based spectral modeling, we assign the conformational changes to compression and rotation of a partially dissociated gD dimer. Free energy calculations indicate that the high rate is a result of near-barrierless diffusion on a protein energy landscape that is radically reshaped by membrane thinning. The structural changes associated with the phase transition are similar to the fluctuation modes of fluid phase membranes, highlighting the importance of understanding the dynamic nature of the membrane environment around proteins.
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Stevenson P, Tokmakoff A. Ultrafast Fluctuations of High Amplitude Electric Fields in Lipid Membranes. J Am Chem Soc 2017; 139:4743-4752. [DOI: 10.1021/jacs.6b12412] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Paul Stevenson
- Department
of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts
Ave., Cambridge, Massachusetts 02139, United States
- Department
of Chemistry, James Frank Institute, and The Institute
for Biophysical Dynamics, The University of Chicago, 929 E 57th Street, Chicago, Illinois 60637, United States
| | - Andrei Tokmakoff
- Department
of Chemistry, James Frank Institute, and The Institute
for Biophysical Dynamics, The University of Chicago, 929 E 57th Street, Chicago, Illinois 60637, United States
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9
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Reppert M, Tokmakoff A. Computational Amide I 2D IR Spectroscopy as a Probe of Protein Structure and Dynamics. Annu Rev Phys Chem 2016; 67:359-86. [DOI: 10.1146/annurev-physchem-040215-112055] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Mike Reppert
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637;
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Andrei Tokmakoff
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois 60637;
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Ghosh A, Serrano AL, Oudenhoven TA, Ostrander JS, Eklund EC, Blair AF, Zanni MT. Experimental implementations of 2D IR spectroscopy through a horizontal pulse shaper design and a focal plane array detector. OPTICS LETTERS 2016; 41:524-7. [PMID: 26907414 PMCID: PMC5301998 DOI: 10.1364/ol.41.000524] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Aided by advances in optical engineering, two-dimensional infrared spectroscopy (2D IR) has developed into a promising method for probing structural dynamics in biophysics and material science. We report two new advances for 2D IR spectrometers. First, we report a fully reflective and totally horizontal pulse shaper, which significantly simplifies alignment. Second, we demonstrate the applicability of mid-IR focal plane arrays (FPAs) as suitable detectors in 2D IR experiments. FPAs have more pixels than conventional linear arrays and can be used to multiplex optical detection. We simultaneously measure the spectra of a reference beam, which improves the signal-to-noise by a factor of 4; and two additional beams that are orthogonally polarized probe pulses for 2D IR anisotropy experiments.
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