1
|
Hassan I, Ferraro F, Imhof P. Effect of the Hydration Shell on the Carbonyl Vibration in the Ala-Leu-Ala-Leu Peptide. Molecules 2021; 26:2148. [PMID: 33917998 PMCID: PMC8068333 DOI: 10.3390/molecules26082148] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 03/30/2021] [Accepted: 03/30/2021] [Indexed: 11/16/2022] Open
Abstract
The vibrational spectrum of the Ala-Leu-Ala-Leu peptide in solution, computed from first-principles simulations, shows a prominent band in the amide I region that is assigned to stretching of carbonyl groups. Close inspection reveals combined but slightly different contributions by the three carbonyl groups of the peptide. The shift in their exact vibrational signature is in agreement with the different probabilities of these groups to form hydrogen bonds with the solvent. The central carbonyl group has a hydrogen bond probability intermediate to the other two groups due to interchanges between different hydrogen-bonded states. Analysis of the interaction energies of individual water molecules with that group shows that shifts in its frequency are directly related to the interactions with the water molecules in the first hydration shell. The interaction strength is well correlated with the hydrogen bond distance and hydrogen bond angle, though there is no perfect match, allowing geometrical criteria for hydrogen bonds to be used as long as the sampling is sufficient to consider averages. The hydrogen bond state of a carbonyl group can therefore serve as an indicator of the solvent's effect on the vibrational frequency.
Collapse
Affiliation(s)
- Irtaza Hassan
- Institute for Theoretical Physics, Freie Universtiät Berlin, Arnimallee 14, 14195 Berlin, Germany;
| | - Federica Ferraro
- Computer Chemistry Center, Friedrich-Alexander University (FAU) Erlangen-Nürnberg, Nägelsbachstrasse 25, 91052 Erlangen, Germany;
| | - Petra Imhof
- Institute for Theoretical Physics, Freie Universtiät Berlin, Arnimallee 14, 14195 Berlin, Germany;
- Computer Chemistry Center, Friedrich-Alexander University (FAU) Erlangen-Nürnberg, Nägelsbachstrasse 25, 91052 Erlangen, Germany;
| |
Collapse
|
2
|
Baiz CR, Błasiak B, Bredenbeck J, Cho M, Choi JH, Corcelli SA, Dijkstra AG, Feng CJ, Garrett-Roe S, Ge NH, Hanson-Heine MWD, Hirst JD, Jansen TLC, Kwac K, Kubarych KJ, Londergan CH, Maekawa H, Reppert M, Saito S, Roy S, Skinner JL, Stock G, Straub JE, Thielges MC, Tominaga K, Tokmakoff A, Torii H, Wang L, Webb LJ, Zanni MT. Vibrational Spectroscopic Map, Vibrational Spectroscopy, and Intermolecular Interaction. Chem Rev 2020; 120:7152-7218. [PMID: 32598850 PMCID: PMC7710120 DOI: 10.1021/acs.chemrev.9b00813] [Citation(s) in RCA: 173] [Impact Index Per Article: 43.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Vibrational spectroscopy is an essential tool in chemical analyses, biological assays, and studies of functional materials. Over the past decade, various coherent nonlinear vibrational spectroscopic techniques have been developed and enabled researchers to study time-correlations of the fluctuating frequencies that are directly related to solute-solvent dynamics, dynamical changes in molecular conformations and local electrostatic environments, chemical and biochemical reactions, protein structural dynamics and functions, characteristic processes of functional materials, and so on. In order to gain incisive and quantitative information on the local electrostatic environment, molecular conformation, protein structure and interprotein contacts, ligand binding kinetics, and electric and optical properties of functional materials, a variety of vibrational probes have been developed and site-specifically incorporated into molecular, biological, and material systems for time-resolved vibrational spectroscopic investigation. However, still, an all-encompassing theory that describes the vibrational solvatochromism, electrochromism, and dynamic fluctuation of vibrational frequencies has not been completely established mainly due to the intrinsic complexity of intermolecular interactions in condensed phases. In particular, the amount of data obtained from the linear and nonlinear vibrational spectroscopic experiments has been rapidly increasing, but the lack of a quantitative method to interpret these measurements has been one major obstacle in broadening the applications of these methods. Among various theoretical models, one of the most successful approaches is a semiempirical model generally referred to as the vibrational spectroscopic map that is based on a rigorous theory of intermolecular interactions. Recently, genetic algorithm, neural network, and machine learning approaches have been applied to the development of vibrational solvatochromism theory. In this review, we provide comprehensive descriptions of the theoretical foundation and various examples showing its extraordinary successes in the interpretations of experimental observations. In addition, a brief introduction to a newly created repository Web site (http://frequencymap.org) for vibrational spectroscopic maps is presented. We anticipate that a combination of the vibrational frequency map approach and state-of-the-art multidimensional vibrational spectroscopy will be one of the most fruitful ways to study the structure and dynamics of chemical, biological, and functional molecular systems in the future.
Collapse
Affiliation(s)
- Carlos R. Baiz
- Department of Chemistry, University of Texas at Austin, Austin, TX 78712, U.S.A
| | - Bartosz Błasiak
- Department of Physical and Quantum Chemistry, Wroclaw University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - Jens Bredenbeck
- Johann Wolfgang Goethe-University, Institute of Biophysics, Max-von-Laue-Str. 1, 60438, Frankfurt am Main, Germany
| | - Minhaeng Cho
- Center for Molecular Spectroscopy and Dynamics, Seoul 02841, Republic of Korea
- Department of Chemistry, Korea University, Seoul 02841, Republic of Korea
| | - Jun-Ho Choi
- Department of Chemistry, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea
| | - Steven A. Corcelli
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, U.S.A
| | - Arend G. Dijkstra
- School of Chemistry and School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U.K
| | - Chi-Jui Feng
- Department of Chemistry, James Franck Institute and Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, U.S.A
| | - Sean Garrett-Roe
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, U.S.A
| | - Nien-Hui Ge
- Department of Chemistry, University of California at Irvine, Irvine, CA 92697-2025, U.S.A
| | - Magnus W. D. Hanson-Heine
- School of Chemistry, University of Nottingham, Nottingham, University Park, Nottingham, NG7 2RD, U.K
| | - Jonathan D. Hirst
- School of Chemistry, University of Nottingham, Nottingham, University Park, Nottingham, NG7 2RD, U.K
| | - Thomas L. C. Jansen
- University of Groningen, Zernike Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Kijeong Kwac
- Center for Molecular Spectroscopy and Dynamics, Seoul 02841, Republic of Korea
| | - Kevin J. Kubarych
- Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, MI 48109, U.S.A
| | - Casey H. Londergan
- Department of Chemistry, Haverford College, Haverford, Pennsylvania 19041, U.S.A
| | - Hiroaki Maekawa
- Department of Chemistry, University of California at Irvine, Irvine, CA 92697-2025, U.S.A
| | - Mike Reppert
- Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Shinji Saito
- Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Myodaiji, Okazaki, 444-8585, Japan
| | - Santanu Roy
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6110, U.S.A
| | - James L. Skinner
- Institute for Molecular Engineering, University of Chicago, Chicago, IL 60637, U.S.A
| | - Gerhard Stock
- Biomolecular Dynamics, Institute of Physics, Albert Ludwigs University, 79104 Freiburg, Germany
| | - John E. Straub
- Department of Chemistry, Boston University, Boston, MA 02215, U.S.A
| | - Megan C. Thielges
- Department of Chemistry, Indiana University, 800 East Kirkwood, Bloomington, Indiana 47405, U.S.A
| | - Keisuke Tominaga
- Molecular Photoscience Research Center, Kobe University, Nada, Kobe 657-0013, Japan
| | - Andrei Tokmakoff
- Department of Chemistry, James Franck Institute and Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, U.S.A
| | - Hajime Torii
- Department of Applied Chemistry and Biochemical Engineering, Faculty of Engineering, and Department of Optoelectronics and Nanostructure Science, Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Naka-Ku, Hamamatsu 432-8561, Japan
| | - Lu Wang
- Department of Chemistry and Chemical Biology, Institute for Quantitative Biomedicine, Rutgers University, 174 Frelinghuysen Road, Piscataway, NJ 08854, U.S.A
| | - Lauren J. Webb
- Department of Chemistry, The University of Texas at Austin, 105 E. 24th Street, STOP A5300, Austin, Texas 78712, U.S.A
| | - Martin T. Zanni
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706-1396, U.S.A
| |
Collapse
|
3
|
Wang J. Ultrafast two-dimensional infrared spectroscopy for molecular structures and dynamics with expanding wavelength range and increasing sensitivities: from experimental and computational perspectives. INT REV PHYS CHEM 2017. [DOI: 10.1080/0144235x.2017.1321856] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Jianping Wang
- Beijing National Laboratory for Molecular Sciences, Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, The Chinese Academy of Sciences, Beijing, P.R. China
- College of Chemistry, University of Chinese Academy of Sciences, Beijing, P.R. China
| |
Collapse
|
4
|
Farag MH, Ruiz-López MF, Bastida A, Monard G, Ingrosso F. Hydration Effect on Amide I Infrared Bands in Water: An Interpretation Based on an Interaction Energy Decomposition Scheme. J Phys Chem B 2014; 119:9056-67. [PMID: 25233436 DOI: 10.1021/jp508675a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The sensitivity of some infrared bands to the local environment can be exploited to shed light on the structure and the dynamics of biological systems. In particular, the amide I band, which is specifically related to vibrations within the peptide bonds, can give information on the ternary structure of proteins, and can be used as a probe of energy transfer. In this work, we propose a model to quantitatively interpret the frequency shift on the amide I band of a model peptide induced by the formation of hydrogen bonds in the first solvation shell. This method allows us to analyze to what extent the electrostatic interaction, electronic polarization and charge transfer affect the position of the amide I band. The impact of the anharmoniticy of the pontential energy surface on the hydration induced shift is elucidated as well.
Collapse
Affiliation(s)
- Marwa H Farag
- †Departamento de Química Física, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia, 30100 Murcia, Spain
| | - Manuel F Ruiz-López
- ‡Université de Lorraine, SRSMC UMR 7565, Vandœuvre-lès-Nancy, F-54506, France.,§CNRS, SRSMC UMR 7565, Vandœuvre-lès-Nancy, F-54506, France
| | - Adolfo Bastida
- †Departamento de Química Física, Regional Campus of International Excellence "Campus Mare Nostrum", Universidad de Murcia, 30100 Murcia, Spain
| | - Gérald Monard
- ‡Université de Lorraine, SRSMC UMR 7565, Vandœuvre-lès-Nancy, F-54506, France.,§CNRS, SRSMC UMR 7565, Vandœuvre-lès-Nancy, F-54506, France
| | - Francesca Ingrosso
- ‡Université de Lorraine, SRSMC UMR 7565, Vandœuvre-lès-Nancy, F-54506, France.,§CNRS, SRSMC UMR 7565, Vandœuvre-lès-Nancy, F-54506, France
| |
Collapse
|
5
|
Błasiak B, Lee H, Cho M. Vibrational solvatochromism: towards systematic approach to modeling solvation phenomena. J Chem Phys 2014; 139:044111. [PMID: 23901964 DOI: 10.1063/1.4816041] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Vibrational solvatochromic frequency shift of IR probe is an effect of interaction between local electric field and IR probe in condensed phases. Despite prolonged efforts to develop empirical maps for vibrational frequency shifts and transition dipoles of IR probes, a systematic approach to ab initio calculation of vibrational solvatochromic charges and multipoles has not been developed. Here, we report on density functional theory (DFT) calculations of N-methylacetamide (NMA) frequency shifts using implicit and coarse-grained models. The solvatochromic infrared spectral shifts are estimated based on the distributed multipole analysis of electronic densities calculated for gas-phase equilibrium structure of NMA. Thus obtained distributed solvatochromic multipole parameters are used to calculate the amide I vibrational frequency shifts of NMA in water clusters that mimic the instantaneous configurations of the liquid water. Our results indicate that the spectral shifts are primarily electrostatic in nature and can be quantitatively reproduced using the proposed model with semi-quantitative accuracy when compared to the corresponding DFT results.
Collapse
Affiliation(s)
- Bartosz Błasiak
- Department of Chemistry, Korea University, Seoul 136-701, South Korea
| | | | | |
Collapse
|
6
|
Reppert M, Tokmakoff A. Electrostatic frequency shifts in amide I vibrational spectra: direct parameterization against experiment. J Chem Phys 2013; 138:134116. [PMID: 23574217 DOI: 10.1063/1.4798938] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The interpretation of protein amide I infrared spectra has been greatly assisted by the observation that the vibrational frequency of a peptide unit reports on its local electrostatic environment. However, the interpretation of spectra remains largely qualitative due to a lack of direct quantitative connections between computational models and experimental data. Here, we present an empirical parameterization of an electrostatic amide I frequency map derived from the infrared absorption spectra of 28 dipeptides. The observed frequency shifts are analyzed in terms of the local electrostatic potential, field, and field gradient, evaluated at sites near the amide bond in molecular dynamics simulations. We find that the frequency shifts observed in experiment correlate very well with the electric field in the direction of the C=O bond evaluated at the position of the amide oxygen atom. A linear best-fit mapping between observed frequencies and electric field yield sample standard deviations of 2.8 and 3.7 cm(-1) for the CHARMM27 and OPLS-AA force fields, respectively, and maximum deviations (within our data set) of 9 cm(-1). These results are discussed in the broader context of amide I vibrational models and the effort to produce quantitative agreement between simulated and experimental absorption spectra.
Collapse
Affiliation(s)
- Mike Reppert
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | | |
Collapse
|
7
|
Maekawa H, Ballano G, Toniolo C, Ge NH. Linear and Two-Dimensional Infrared Spectroscopic Study of the Amide I and II Modes in Fully Extended Peptide Chains. J Phys Chem B 2010; 115:5168-82. [DOI: 10.1021/jp105527n] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Hiroaki Maekawa
- Department of Chemistry, University of California at Irvine, Irvine, California, 92697-2025
| | - Gema Ballano
- Institute of Biomolecular Chemistry, CNR, Padova Unit, Department of Chemistry, University of Padova, 35131 Padova, Italy
| | - Claudio Toniolo
- Institute of Biomolecular Chemistry, CNR, Padova Unit, Department of Chemistry, University of Padova, 35131 Padova, Italy
| | - Nien-Hui Ge
- Department of Chemistry, University of California at Irvine, Irvine, California, 92697-2025
| |
Collapse
|
8
|
Maekawa H, De Poli M, Moretto A, Toniolo C, Ge NH. Toward detecting the formation of a single helical turn by 2D IR cross peaks between the amide-I and -II modes. J Phys Chem B 2010; 113:11775-86. [PMID: 19642666 DOI: 10.1021/jp9045879] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have combined two-dimensional infrared (2D IR) spectroscopy and isotope substitutions to reveal the vibrational couplings between a pair of amide-I and -II modes that are several residues away but directly connected through a hydrogen bond in a helical peptide. This strategy is demonstrated on a 3(10)-helical hexapeptide, Z-Aib-L-Leu-(Aib)2-Gly-Aib-OtBu, and its 13C=18O-Leu monolabeled and 13C=18O-Leu/15N-Gly bis-labeled isotopomers in CDCl3. The isotope-dependent amide-I/II cross peaks clearly show that the second and fourth peptide linkages are vibrationally coupled as they are in proximity, forming a 3(10)-helical turn. The experimental spectra are compared to simulations based on a vibrational exciton Hamiltonian model that fully takes into account the amide-I and -II modes. The amide-II local mode frequency is evaluated by a new model based on the effects of hydrogen-bond geometry and sites. Ab initio nearest-neighbor coupling maps of the amide-I/I, -I/II, -II/I and -II/II modes are generated by isotopically isolating the local modes of N-acetyl-glycine N'-methylamide (AcGlyNHMe). Longer range couplings are modeled by transition charge interactions. The effects of the capping groups are incorporated and isotope effects are analyzed based on ab initio calculations of six model compounds. The main features of the 2D IR spectra are reproduced by this modeling. The conformational sensitivity of the isotope-dependent amide-I/II cross peaks is discussed in comparison with the calculated spectra for a semiextended structure. Our experimental and theoretical study demonstrates that the combination of 2D IR and 13C=18O/15N labeling is a useful structural method for detecting helical turn formation with residue-level specificity.
Collapse
Affiliation(s)
- Hiroaki Maekawa
- Department of Chemistry, University of California at Irvine, Irvine, California 92697-2025, USA
| | | | | | | | | |
Collapse
|
9
|
Maekawa H, Ge NH. Comparative Study of Electrostatic Models for the Amide-I and -II Modes: Linear and Two-Dimensional Infrared Spectra. J Phys Chem B 2010; 114:1434-46. [DOI: 10.1021/jp908695g] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hiroaki Maekawa
- Department of Chemistry, University of California at Irvine, Irvine, California 92697-2025
| | - Nien-Hui Ge
- Department of Chemistry, University of California at Irvine, Irvine, California 92697-2025
| |
Collapse
|
10
|
Maekawa H, De Poli M, Toniolo C, Ge NH. Couplings between peptide linkages across a 3(10)-helical hydrogen bond revealed by two-dimensional infrared spectroscopy. J Am Chem Soc 2009; 131:2042-3. [PMID: 19199613 DOI: 10.1021/ja807572f] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Vibrational couplings between the amide modes are keenly dependent on peptide structure. Site-specific couplings can inform us of molecular conformation in detail. For example, when an amide-I mode couples to an amide-II mode that is three residues away because they are brought into proximity in the presence of an intramolecular C=O...H-N hydrogen bond, the coupling can provide direct evidence for single helical turn formation, a proposed key step in coil-helix transition. In this work, we measure 2D IR spectra of a 3(10)-helical hexapeptide, Z-Aib-l-Leu-(Aib)(2)-Gly-Aib-OtBu, and its (13)C=(18)O-Leu monolabeled and (13)C=(18)O-Leu/(15)N-Gly bis-labeled isotopomers in CDCl(3). The isotope-dependent amide-I/II cross-peaks clearly reveal the existence of vibrational coupling between the second and fourth peptide linkages that are connected through a 3(10)-helical hydrogen bond. Our results demonstrate that the combination of 2D IR and (13)C=(18)O/(15)N labeling is a useful structural method for probing local peptide conformation with residue-level specificity.
Collapse
Affiliation(s)
- Hiroaki Maekawa
- Department of Chemistry, University of California at Irvine, Irvine, California 92697-2025, USA
| | | | | | | |
Collapse
|
11
|
Maekawa H, Formaggio F, Toniolo C, Ge NH. Onset of 3(10)-helical secondary structure in aib oligopeptides probed by coherent 2D IR spectroscopy. J Am Chem Soc 2008; 130:6556-66. [PMID: 18444622 DOI: 10.1021/ja8007165] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
We have investigated the onset of the secondary structure and the evolution of two-dimensional infrared (2D IR) spectral patterns as a function of chain length with a study of 3(10)-helical peptides. The results show that 2D IR is highly sensitive to peptide conformation, disorder, and size. An extensive set of 2D IR spectra of C (alpha)-methylated homopeptides, Z-(Aib) n -O tBu ( n = 3, 5, 8, and 10), in CDCl 3 was measured in the amide-I region. The 2D spectral patterns of the tripeptide are quite different from those of the longer peptides. The spectral signatures begin to converge at the pentapeptide and become almost the same for the octa- and decapeptide. Simulations employing a vibrational exciton model were performed, with the local mode frequency shifts estimated from the intramolecular hydrogen bond electrostatic energies. The 2D spectra are well simulated using dihedral angle distributions around the average values (phi, psi) approximately (-57 degrees , -31 degrees) with a width of approximately 21 degrees. The simulated site-dependent amide-I local mode frequencies are in agreement with those from scaled semiempirical AM1 calculations. The tripeptide exhibits a more noticeable discrepancy between the experimental and simulated cross-peak patterns. This behavior suggests the presence of a peptide population outside the single beta-turn conformation. The onset of the 3(10)-helical secondary structure appears to already occur at the pentapeptide level.
Collapse
Affiliation(s)
- Hiroaki Maekawa
- Department of Chemistry, University of California at Irvine, Irvine, California 92697-2025, USA
| | | | | | | |
Collapse
|
12
|
Affiliation(s)
- Minhaeng Cho
- Department of Chemistry and Center for Multidimensional Spectroscopy, Korea University, Seoul 136-701, Korea.
| |
Collapse
|
13
|
Maekawa H, Toniolo C, Broxterman QB, Ge NH. Two-Dimensional Infrared Spectral Signatures of 310- and α-Helical Peptides. J Phys Chem B 2007; 111:3222-35. [PMID: 17388471 DOI: 10.1021/jp0674874] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Two-dimensional infrared (2D IR) spectra of Calpha-alkylated model octapeptides Z-(Aib)8-OtBu, Z-(Aib)5-L-Leu-(Aib)2-OMe, and Z-[L-(alphaMeVal)]8-OtBu have been measured in the amide I region to acquire 2D spectral signatures characteristic of 3(10)- and alpha-helical conformations. Phase-adjusted 2D absorptive spectra recorded with parallel polarizations are dominated by intense diagonal peaks, whereas 2D rephasing spectra obtained at the double-crossed polarization configuration reveal cross-peak patterns that are essential for structure determination. In CDCl3, all three peptides are of the 3(10)-helix conformation and exhibit a doublet cross-peak pattern. In 1,1,1,3,3,3-hexafluoroisopropanol, Z-[L-(alphaMeVal)]8-OtBu undergoes slow acidolysis and 3(10)-to-alpha-helix transition. In the course of this conformational change, its 2D rephasing spectrum evolves from an elongated doublet, characteristic of a distorted 3(10)-helix, to a multiple-peak pattern, after becoming an alpha-helix. The linear IR and 2D absorptive spectra are much less informative in discerning the structural changes. The experimental spectra are compared to simulations based on a vibrational exciton Hamiltonian model. The through-bond and through-space vibrational couplings are modeled by ab initio coupling maps and transition dipole interactions. The local amide I frequency is evaluated by a new approach that takes into account the effects of hydrogen-bond geometry and sites. The static diagonal and off-diagonal disorders are introduced into the Hamiltonian through statistical models to account for conformational fluctuations and inhomogeneous broadening. The sensitivity of cross-peak patterns to different helical conformations and the chain length dependence of the spectral features for short 3(10)- and alpha-helices are discussed.
Collapse
Affiliation(s)
- Hiroaki Maekawa
- Department of Chemistry, University of California at Irvine, Irvine, California 92697-2025, USA
| | | | | | | |
Collapse
|
14
|
Reducing the vibrational coupling network in N-methylacetamide as a model for ab initio infrared spectra computations of peptides. Chem Phys 2006. [DOI: 10.1016/j.chemphys.2005.08.037] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
15
|
DeCamp MF, DeFlores L, McCracken JM, Tokmakoff A, Kwac K, Cho M. Amide I Vibrational Dynamics ofN-Methylacetamide in Polar Solvents: The Role of Electrostatic Interactions. J Phys Chem B 2005; 109:11016-26. [PMID: 16852342 DOI: 10.1021/jp050257p] [Citation(s) in RCA: 207] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The vibrational frequency of the amide I transition of peptides is known to be sensitive to the strength of its hydrogen bonding interactions. In an effort to account for interactions with hydrogen bonding solvents in terms of electrostatics, we study the vibrational dynamics of the amide I coordinate of N-methylacetamide in prototypical polar solvents: D2O, CDCl3, and DMSO-d6. These three solvents have varying hydrogen bonding strengths, and provide three distinct solvent environments for the amide group. The frequency-frequency correlation function, the orientational correlation function, and the vibrational relaxation rate of the amide I vibration in each solvent are retrieved by using three-pulse vibrational photon echoes, two-dimensional infrared spectroscopy, and pump-probe spectroscopy. Direct comparisons are made to molecular dynamics simulations. We find good quantitative agreement between the experimentally retrieved and simulated correlation functions over all time scales when the solute-solvent interactions are determined from the electrostatic potential between the solvent and the atomic sites of the amide group.
Collapse
Affiliation(s)
- M F DeCamp
- Department of Chemistry and George R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | | | | | | | | | | |
Collapse
|
16
|
Czarnecki MA, Haufa KZ. Effect of Temperature and Concentration on the Structure of N-Methylacetamide−Water Complexes: Near-Infrared Spectroscopic Study. J Phys Chem A 2005; 109:1015-21. [PMID: 16833408 DOI: 10.1021/jp0471150] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Generalized two-dimensional (2D) FT-NIR correlation spectroscopy and chemometric methods have been used to study temperature-dependent spectral changes in pure N-methylacetamide (NMA) and NMA-water mixtures. We also examined the effect of varying water content on the structure of the mixture. It has been found that the extent of self-association of NMA in CCl4 is very high; the association occurs even at concentration of 0.001 M. In the pure liquid NMA, the population of the monomers is negligible and the structure is dominated by the linear associates. An increase in temperature reduces the number of hydrogen bonds, but in contrast to alcohols their strength remains nearly the same. This reflects a difference in the mechanism of thermal breaking of the associates of NMA and alcohols. The present results reveal that the interaction between NMA and water in the NMA-rich region (X(H2O) < 0.1) does not have a significant effect on the intrinsic structure of NMA. The structure of NMA is dominant, and the molecules of water do not form separate clusters but are dispersed and incorporated into the structure of NMA. We did not observe the presence of the free OH groups in the mixture. This led to the suggestion that each molecule of water forms two hydrogen bonds to two different molecules of NMA. An analysis of the asynchronous spectra reveals that most of the peaks observed in the asynchronous spectra, constructed from the temperature-dependent data, simply result from the frequency shift. This assumption is supported by the simulation studies.
Collapse
Affiliation(s)
- Mirosław A Czarnecki
- Faculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50-383 Wrocław, Poland.
| | | |
Collapse
|