1
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Li J, Hu Z, Beuerman R, Verma C. Molecular Environment Modulates Conformational Differences between Crystal and Solution States of Human β-Defensin 2. J Phys Chem B 2017; 121:2739-2747. [DOI: 10.1021/acs.jpcb.7b00083] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jianguo Li
- Singapore Eye Research Institute, 11 Third Hospital Avenue, #06-00, Singapore 168751
- Bioinformatics Institute (A*-STAR), 30 Biopolis Street, #07-01 Matrix, Singapore 138671
| | - Zhongqiao Hu
- Bioinformatics Institute (A*-STAR), 30 Biopolis Street, #07-01 Matrix, Singapore 138671
| | - Roger Beuerman
- Singapore Eye Research Institute, 11 Third Hospital Avenue, #06-00, Singapore 168751
- Department
of Ophthalmology, National University of Singapore, Singapore 119074
- School of
Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637459
| | - Chandra Verma
- Singapore Eye Research Institute, 11 Third Hospital Avenue, #06-00, Singapore 168751
- Bioinformatics Institute (A*-STAR), 30 Biopolis Street, #07-01 Matrix, Singapore 138671
- School
of Biological Sciences, Nanyang Technological University, Singapore 637551
- Department
of Biological Sciences, National University of Singapore, Singapore 117543
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2
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De Sancho D, Kubas A, Wang PH, Blumberger J, Best RB. Identification of Mutational Hot Spots for Substrate Diffusion: Application to Myoglobin. J Chem Theory Comput 2015; 11:1919-27. [PMID: 26574395 PMCID: PMC6132223 DOI: 10.1021/ct5011455] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The pathways by which small molecules (substrates or inhibitors) access active sites are a key aspect of the function of enzymes and other proteins. A key problem in designing or altering such proteins is to identify sites for mutation that will have the desired effect on the substrate transport properties. While specific access channels have been invoked in the past, molecular simulations suggest that multiple routes are possible, complicating the analysis. This complexity, however, can be captured by a Markov State Model (MSM) of the ligand diffusion process. We have developed a sensitivity analysis of the resulting rate matrix, which identifies the locations where mutations should have the largest effect on the diffusive on rate. We apply this method to myoglobin, which is the best characterized example both from experiment and simulation. We validate the approach by translating the sensitivity parameter obtained from this method into the CO binding rates in myoglobin upon mutation, resulting in a semi-quantitative correlation with experiments. The model is further validated against an explicit simulation for one of the experimental mutants.
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Affiliation(s)
- David De Sancho
- Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, United Kingdom
- CIC nanoGUNE , Tolosa Hiribidea 76, 20018 Donostia-San Sebastian, Spain
- IKERBASQUE, Basque Foundation for Science , Maria Diaz de Haro 3, 48013 Bilbao, Spain
| | - Adam Kubas
- Department of Physics and Astronomy, University College London , Gower Street, London WC1E 6BT, United Kingdom
| | - Po-Hung Wang
- Department of Physics and Astronomy, University College London , Gower Street, London WC1E 6BT, United Kingdom
- Theoretical Molecular Science Laboratory , 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - Jochen Blumberger
- Department of Physics and Astronomy, University College London , Gower Street, London WC1E 6BT, United Kingdom
| | - Robert B Best
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892-0520, United States
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3
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Pohl G, Asensio A, Dannenberg JJ. Capping parallel β-sheets of acetyl(Ala)6NH2 with an acetyl(Ala)5ProNH2 can arrest the growth of the sheet, suggesting a potential for curtailing amyloid growth. An ONIOM and density functional theory study. Biochemistry 2014; 53:617-23. [PMID: 24422496 PMCID: PMC3985835 DOI: 10.1021/bi401366w] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present ONIOM calculations using B3LYP/d95(d,p) as the high level and AM1 as the medium level on parallel β-sheets containing four strands of Ac-AAAAAA-NH2 capped with either Ac-AAPAAA-NH2 or Ac-AAAPAA-NH2. Because Pro can form H-bonds from only one side of the peptide linkage (that containing the C═O H-bond acceptor), only one of the two Pro-containing strands can favorably add to the sheet on each side. Surprisingly, when the sheet is capped with AAPAAA-NH2 at one edge, the interaction between the cap and sheet is slightly more stabilizing than that of another all Ala strand. Breaking down the interaction enthalpies into H-bonding and distortion energies shows the favorable interaction to be due to lower distortion energies in both the strand and the four-stranded sheet. Because another strand would be inhibited for attachment to the other side of the capping (Pro-containing) strand, we suggest the possible use of Pro residues in peptides designed to arrest the growth of many amyloids.
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Affiliation(s)
- Gabor Pohl
- Department of Chemistry, City University of New York, Hunter College and the Graduate School , 695 Park Avenue, New York, New York 10065, United States
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4
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Ioannou F, Leontidis E, Archontis G. Helix Formation by Alanine-Based Peptides in Pure Water and Electrolyte Solutions: Insights from Molecular Dynamics Simulations. J Phys Chem B 2013; 117:9866-76. [DOI: 10.1021/jp406231g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Filippos Ioannou
- Department
of Chemistry, and ‡Deparment of Physics, University of Cyprus, PO20537, CY1678, Nicosia, Cyprus
| | - Epameinondas Leontidis
- Department
of Chemistry, and ‡Deparment of Physics, University of Cyprus, PO20537, CY1678, Nicosia, Cyprus
| | - Georgios Archontis
- Department
of Chemistry, and ‡Deparment of Physics, University of Cyprus, PO20537, CY1678, Nicosia, Cyprus
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5
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Marianski M, Asensio A, Dannenberg JJ. Comparison of some dispersion-corrected and traditional functionals as applied to peptides and conformations of cyclohexane derivatives. J Chem Phys 2012; 137:044109. [PMID: 22852599 DOI: 10.1063/1.4737517] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We compare the energetic and structural properties of fully optimized α-helical and antiparallel β-sheet polyalanines and the energetic differences between axial and equatorial conformations of three cyclohexane derivatives (methyl, fluoro, and chloro) as calculated using several functionals designed to treat dispersion (B97-D, ωB97x-D, M06, M06L, and M06-2X) with other traditional functionals not specifically parametrized to treat dispersion (B3LYP, X3LYP, and PBE1PBE) and with experimental results. Those functionals developed to treat dispersion significantly overestimate interaction enthalpies of folding for the α-helix and predict unreasonable structures that contain Ramachandran φ and ψ and C = O...N H-bonding angles that are out of the bounds of databases compiled the β-sheets. These structures are consistent with overestimation of the interaction energies. For the cyclohexanes, these functionals overestimate the stabilities of the axial conformation, especially when used with smaller basis sets. Their performance improves when the basis set is improved from D95∗∗ to aug-cc-pVTZ (which would not be possible with systems as large as the peptides).
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Affiliation(s)
- Mateusz Marianski
- Department of Chemistry, City University of New York - Hunter College and the Graduate School, 695 Park Avenue, New York, New York 10065, USA
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6
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Pandey PR, Roy S. Distinctions in early stage unwinding mechanisms of zwitterionic, capped, and neutral forms of different α-helical homopolymeric peptides. J Phys Chem B 2012; 116:4731-40. [PMID: 22448707 DOI: 10.1021/jp301556x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molecular dynamics simulations of α-helical polyalanine, polyleucine, polylysine, and poly(glutamic acid) with different forms of terminal groups in water at 300 K showed sharp distinctions in their unwinding mechanisms. Zwitterionic, capped, and neutral forms of polyalanine, polyleucine, and polylysine have been explored to elucidate their unwinding mechanism at very early stage, e.g., initial time window. Role of water in the unwinding mechanisms of the various helices has been envisaged. Also, it is evident from our calculations that the short- and long-range nonbonded interactions among the side chains is an important factor determining the unwinding mechanisms of the various homopolymeric α-helices. These findings can be helpful in constructing predictive models for understanding of the unwinding of α-helical proteins and peptides.
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Affiliation(s)
- Prithvi Raj Pandey
- Physical Chemistry Division, National Chemical Laboratory , Pune 411008, India
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7
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López GE, Colón-Díaz I, Cruz A, Ghosh S, Nicholls SB, Viswanathan U, Hardy JA, Auerbach SM. Modeling Nonaqueous Proton Wires Built from Helical Peptides: Biased Proton Transfer Driven by Helical Dipoles. J Phys Chem A 2012; 116:1283-8. [DOI: 10.1021/jp210208m] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gustavo E. López
- Department of Chemistry, University of Puerto Rico at Mayagüez, Mayagüez, Puerto Rico 00681
- Department of Chemistry, Lehman College-CUNY, Bronx, New York 10034, United States
| | - Inara Colón-Díaz
- Department of Chemistry, University of Puerto Rico at Mayagüez, Mayagüez, Puerto Rico 00681
| | - Anthony Cruz
- Department of Chemistry, University of Puerto Rico at Mayagüez, Mayagüez, Puerto Rico 00681
- Department of Chemistry, Lehman College-CUNY, Bronx, New York 10034, United States
| | - Sumana Ghosh
- Department of Chemistry, University of Massachusetts at Amherst, Amherst, Massachusetts 01003, United States
| | - Samantha B. Nicholls
- Department of Chemistry, University of Massachusetts at Amherst, Amherst, Massachusetts 01003, United States
| | - Usha Viswanathan
- Department of Chemistry, University of Massachusetts at Amherst, Amherst, Massachusetts 01003, United States
| | - Jeanne A. Hardy
- Department of Chemistry, University of Massachusetts at Amherst, Amherst, Massachusetts 01003, United States
| | - Scott M. Auerbach
- Department of Chemistry, University of Massachusetts at Amherst, Amherst, Massachusetts 01003, United States
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8
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Chen YF, Dannenberg JJ. The effect of polarization on multiple hydrogen-bond formation in models of self-assembling materials. J Comput Chem 2011; 32:2890-5. [PMID: 21717481 DOI: 10.1002/jcc.21870] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Revised: 05/01/2011] [Accepted: 05/23/2011] [Indexed: 01/27/2023]
Abstract
We report density functional theory calculations at the B3LYP/D95(d,p) level on several different cyclic H-bonding dimers, where the monomers of each are connected by a pair of N-H···O=C H-bonding interactions, and the H-bonding donors and acceptors on each monomer are separated by polarizable spacers. Depending on the structures, the individual H-bonds vary in strength (enthalpy) by over a factor of four, from 2.41 to 10.99 kcal/mol. We attribute most of the variation in interaction energies to differences in the extent of polarization due to each of the H-bonds, which can either combine constructively or destructively. The dipole-dipole interactions between the pair of H-bonds also contribute somewhat to the relative stabilities. The relevance of these results to the design of self-assembling materials is discussed.
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Affiliation(s)
- Yung-Fou Chen
- Department of Chemistry, Hunter College and the Graduate School, City University of New York, 695 Park Avenue, New York, New York 10065, USA
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9
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Best RB, Mittal J. Protein Simulations with an Optimized Water Model: Cooperative Helix Formation and Temperature-Induced Unfolded State Collapse. J Phys Chem B 2010; 114:14916-23. [DOI: 10.1021/jp108618d] [Citation(s) in RCA: 210] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Robert B. Best
- Cambridge University, Department of Chemistry, Lensfield Road, Cambridge CB2 1EW, United Kingdom, and Lehigh University, Department of Chemical Engineering, Bethlehem, Pennsylvania 18015, United States
| | - Jeetain Mittal
- Cambridge University, Department of Chemistry, Lensfield Road, Cambridge CB2 1EW, United Kingdom, and Lehigh University, Department of Chemical Engineering, Bethlehem, Pennsylvania 18015, United States
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10
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Balamurugan K, Gopalakrishnan R, Raman SS, Subramanian V. Exploring the Changes in the Structure of α-Helical Peptides Adsorbed onto a Single Walled Carbon Nanotube Using Classical Molecular Dynamics Simulation. J Phys Chem B 2010; 114:14048-58. [DOI: 10.1021/jp106177n] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- K. Balamurugan
- Chemical Laboratory, Central Leather Research Institute, Council of Scientific and Industrial Research, Adyar, Chennai- 600020, India
| | - R. Gopalakrishnan
- Chemical Laboratory, Central Leather Research Institute, Council of Scientific and Industrial Research, Adyar, Chennai- 600020, India
| | - S. Sundar Raman
- Chemical Laboratory, Central Leather Research Institute, Council of Scientific and Industrial Research, Adyar, Chennai- 600020, India
| | - V. Subramanian
- Chemical Laboratory, Central Leather Research Institute, Council of Scientific and Industrial Research, Adyar, Chennai- 600020, India
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11
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Nasr KA, Schubert CR, Török M, Kennedy RJ, Kemp DS. Helix-coil energetics for helix formers and breakers reflect context and temperature: mutants of helically robust, guest-sensitive homopeptide hosts. Biopolymers 2010; 91:311-20. [PMID: 19117030 DOI: 10.1002/bip.21129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The natural amino acids are primarily helix breakers at the low assignment temperatures characteristic of many studies, but recent genomic analyses of thermophilic proteins suggest that at high temperatures, some breakers may become strong helix formers. Moreover, the breaker/former inventory has not been previously characterized at the physiologically relevant temperature of 37 degrees C. The versatility of 13C==O NMR chemical shifts as helicity reporters allows construction of two mutant peptide series, tailored to expand the range of temperature assignments for helical propensities and derived from the core hosts tL-Ala9XxxAla9-tL and tL-AlaNva4XxxNva4Ala9-tL, Nva=norvaline. For three limiting guests Xxx, the helix former Nva and the breakers Gly and Pro, we report wXxx[T] assignments at seven temperatures from 2 to 80 degrees C, validating our reasoning and paving the way for assignment of a definitive wXxx[T] data-base.
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Affiliation(s)
- Khaled A Nasr
- Department of Chemistry, Room 6-433, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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12
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Moreau RJ, Schubert CR, Nasr KA, Török M, Miller JS, Kennedy RJ, Kemp DS. Context-independent, temperature-dependent helical propensities for amino acid residues. J Am Chem Soc 2009; 131:13107-16. [PMID: 19702302 PMCID: PMC2770013 DOI: 10.1021/ja904271k] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Assigned from data sets measured in water at 2, 25, and 60 degrees C containing (13)C=O NMR chemical shifts and [theta](222) ellipticities, helical propensities are reported for the 20 genetically coded amino acids, as well as for norvaline and norleucine. These have been introduced by chemical synthesis at central sites within length-optimized, spaced, solubilized Ala(19) hosts. The resulting polyalanine-derived, quantitative propensity sets express for each residue its temperature-dependent but context-independent tendency to forego a coil state and join a preexisting helical conformation. At 2 degrees C their rank ordering is: P << G < H < C, T, N < S < Y, F, W < V, D < K < Q < I < R, M < L < E < A; at 60 degrees C the rank becomes: H, P < G < C < R, K < T, Y, F < N, V < S < Q < W, D < I, M < E < A < L. The DeltaDeltaG values, kcal/mol, relative to alanine, for the cluster T, N, S, Y, F, W, V, D, Q, imply that at 2 degrees C all are strong breakers: DeltaDeltaG(mean) = +0.63 +/- 0.11, but at 60 degrees C their breaking tendencies are dramatically attenuated and converge toward the mean: DeltaDeltaG(mean) = +0.25 +/- 0.07. Accurate modeling of helix-rich proteins found in thermophiles, mesophiles, and organisms that flourish near 0 degrees C thus requires appropriately matched propensity sets. Comparisons are offered between the temperature-dependent propensity assignments of this study and those previously assigned by the Scheraga group; the special problems that attend propensity assignments for charged residues are illustrated by lysine guest data; and comparisons of errors in helicity assignments from shifts and ellipticity data show that the former provide superior precision and accuracy.
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Affiliation(s)
- Robert J Moreau
- Department of Chemistry, Room 6-433, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Best RB, Hummer G. Optimized molecular dynamics force fields applied to the helix-coil transition of polypeptides. J Phys Chem B 2009; 113:9004-15. [PMID: 19514729 PMCID: PMC3115786 DOI: 10.1021/jp901540t] [Citation(s) in RCA: 649] [Impact Index Per Article: 43.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Obtaining the correct balance of secondary structure propensities is a central priority in protein force-field development. Given that current force fields differ significantly in their alpha-helical propensities, a correction to match experimental results would be highly desirable. We have determined simple backbone energy corrections for two force fields to reproduce the fraction of helix measured in short peptides at 300 K. As validation, we show that the optimized force fields produce results in excellent agreement with nuclear magnetic resonance experiments for folded proteins and short peptides not used in the optimization. However, despite the agreement at ambient conditions, the dependence of the helix content on temperature is too weak, a problem shared with other force fields. A fit of the Lifson-Roig helix-coil theory shows that both the enthalpy and entropy of helix formation are too small: the helix extension parameter w agrees well with experiment, but its entropic and enthalpic components are both only about half the respective experimental estimates. Our structural and thermodynamic analyses point toward the physical origins of these shortcomings in current force fields, and suggest ways to address them in future force-field development.
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Affiliation(s)
- Robert B Best
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
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14
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Bhate MP, Woodard JC, Mehta MA. Solvation and Hydrogen Bonding in Alanine- and Glycine-Containing Dipeptides Probed Using Solution- and Solid-State NMR Spectroscopy. J Am Chem Soc 2009; 131:9579-89. [DOI: 10.1021/ja902917s] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Manasi P. Bhate
- Department of Chemistry and Biochemistry, Oberlin College, Oberlin, Ohio 44074
| | - Jaie C. Woodard
- Department of Chemistry and Biochemistry, Oberlin College, Oberlin, Ohio 44074
| | - Manish A. Mehta
- Department of Chemistry and Biochemistry, Oberlin College, Oberlin, Ohio 44074
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Stability and Design of α-Helical Peptides. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2008; 83:1-52. [DOI: 10.1016/s0079-6603(08)00601-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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16
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Job GE, Kennedy RJ, Heitmann B, Miller JS, Walker SM, Kemp* DS. Temperature- and length-dependent energetics of formation for polyalanine helices in water: assignment of w(Ala)(n,T) and temperature-dependent CD ellipticity standards. J Am Chem Soc 2007; 128:8227-33. [PMID: 16787087 PMCID: PMC1560101 DOI: 10.1021/ja060094y] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Length-dependent helical propensities w(Ala)(n,T) at T = 10, 25, and 60 degrees C are assigned from t/c values and NMR 13C chemical shifts for series 1 peptides TrpLys(m)Inp2(t)Leu-Ala(n)(t)LeuInp2Lys(m)NH2, n = 15, 19, and 25, m = 5, in water. Van't Hoff analysis of w(Ala)(n,T) show that alpha-helix formation is primarily enthalpy-driven. For series 2 peptides Ac-Trp Lys5Inp2(t)Leu-(beta)AspHel-Ala(n)-beta-(t)LeuInp2Lys5NH2, n = 12 and 22, which contain exceptionally helical Ala(n) cores, protection factor-derived fractional helicities FH are assigned in the range 10-30 degrees C in water and used to calibrate temperature-dependent CD ellipticities [theta](lambda,H,n,T). These are applied to CD data for series 1 peptides, 12 < or = n < or = 45, to confirm the w(Ala)(n,T) assignments at T = 25 and 60 degrees C. The [theta](lambda,H,n,T) are temperature dependent within the wavelength region, 222 +/- 12 nm, and yield a temperature correction for calculation of FH from experimental values of [theta](222,n,T,Exp).
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17
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Quapp W. Finding the transition state without initial guess: The growing string method for Newton trajectory to isomerization and enantiomerization reaction of alanine dipeptide and poly(15)alanine. J Comput Chem 2007; 28:1834-47. [PMID: 17342714 DOI: 10.1002/jcc.20688] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We report a new, high-dimensional application of a method for finding a transition state (TS) between a reactant and a product on the potential energy surface: the search of a growing string along a reaction path defined by any Newton trajectory in combination with the Berny method (Quapp, J Chem Phys (2005), 122, 174106; we have provided this algorithm on a web page). Two given minima are connected by a one-dimensional, but usually curvilinear reaction coordinate. It leads to the TS region. The application of the method to alanine dipeptide finds the TS of the isomerisation C(7 ax) --> C(5), some TSs of the enantiomerisation of C(7 ax) from L-form to quasi-D-form, and it finds the TS region of a transition of a partly unfolded, bent structure which turns back into a mainly alpha-helix in the Ac(Ala)(15)NHMe polyalanine (all at the quantum mechanical level B3LYP/6-31G: the growing string calculation is interfaced with the Gaussian03 package). The formation or dissolvation of some alpha- or 3(10)-hydrogen bonds of the helix are discussed along the TS pathway, as well as the case of an enantiomer at the central residue of the helix.
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Affiliation(s)
- Wolfgang Quapp
- Mathematical Institute, University of Leipzig, Augustus-Platz, D-04109 Leipzig, Germany.
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18
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Mikhonin AV, Asher SA, Bykov SV, Murza A. UV Raman spatially resolved melting dynamics of isotopically labeled polyalanyl peptide: slow alpha-helix melting follows 3(10)-helices and pi-bulges premelting. J Phys Chem B 2007; 111:3280-92. [PMID: 17388440 DOI: 10.1021/jp0654009] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We used UV resonance Raman (UVRR) to examine the spatial dependence of the T-jump secondary structure relaxation of an isotopically labeled 21-residue mainly Ala peptide, AdP. The AdP penultimate Ala residues were perdeuterated, leaving the central residues hydrogenated, to allow separate monitoring of melting of the middle versus the end peptide bonds. For 5 to 30 degrees C T-jumps, the central peptide bonds show a approximately 2-fold slower relaxation time (189 +/- 31 ns) than do the exterior peptide bonds (97 +/- 15 ns). In contrast, for a 20 to 40 degrees C T-jump, the central peptide bond relaxation appears to be faster (56 +/- 6 ns) than that of the penultimate peptide bonds (131 +/- 46 ns). We show that, if the data are modeled as a two-state transition, we find that only exterior peptide bonds show anti-Arrhenius folding behavior; the middle peptide bonds show both normal Arrhenius-like folding and unfolding. This anti-Arrhenius behavior results from the involvement of pi-bulges/helices and 3(10)-helix states in the melting. The unusual temperature dependence of the (un)folding rates of the interior and exterior peptide bonds is due to the different relative (un)folding rates of 3(10)-helices, alpha-helices, and pi-bulges/helices. Pure alpha-helix unfolding rates are approximately 12-fold slower (approximately 1 micros) than that of pi-bulges and 3(10)-helices. In addition, we also find that the alpha-helix is most stable at the AdP N-terminus where eight consecutive Ala occur, whereas the three hydrophilic Arg located in the middle and at the C-terminus destabilize the alpha-helix in these regions and induce defects such as pi-bulges and 3(10)-helices.
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Affiliation(s)
- Aleksandr V Mikhonin
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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