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Title: Intramolecular Interactions Overcome Hydration to Drive the Collapse Transition of Gly 15

Abstract

Simulations and experiments show oligo-glycines, polypeptides lacking any side chains, can collapse in water. We assess the hydration thermodynamics of this collapse by calculating the hydration free energy at each of the end points of the reaction coordinate, here taken as the end-to-end distance (r) in the chain. To examine the role of the various conformations for a given r, we study the conditional distribution, P(R g|r), of the radius of gyration for a given value of r. The free energy change versus Rg, -k BT ln P(R g|r), is found to vary more gently compared to the corresponding variation in the excess hydration free energy. Using this observation within a multistate generalization of the potential distribution theorem, we calculate a tight upper bound for the hydration free energy of the peptide for a given r. On this basis, we find that peptide hydration greatly favors the expanded state of the chain, despite primitive hydrophobic effects favoring chain collapse. The net free energy of collapse is seen to be a delicate balance between opposing intrapeptide and hydration effects, with intrapeptide contributions favoring collapse.

Authors:
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory-National Energy Research Scientific Computing Center
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1480288
DOE Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry
Additional Journal Information:
Journal Volume: 121; Journal Issue: 34; Journal ID: ISSN 1520-6106
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English

Citation Formats

None, None. Intramolecular Interactions Overcome Hydration to Drive the Collapse Transition of Gly15. United States: N. p., 2017. Web. doi:10.1021/acs.jpcb.7b05469.
None, None. Intramolecular Interactions Overcome Hydration to Drive the Collapse Transition of Gly15. United States. doi:10.1021/acs.jpcb.7b05469.
None, None. Thu . "Intramolecular Interactions Overcome Hydration to Drive the Collapse Transition of Gly15". United States. doi:10.1021/acs.jpcb.7b05469.
@article{osti_1480288,
title = {Intramolecular Interactions Overcome Hydration to Drive the Collapse Transition of Gly15},
author = {None, None},
abstractNote = {Simulations and experiments show oligo-glycines, polypeptides lacking any side chains, can collapse in water. We assess the hydration thermodynamics of this collapse by calculating the hydration free energy at each of the end points of the reaction coordinate, here taken as the end-to-end distance (r) in the chain. To examine the role of the various conformations for a given r, we study the conditional distribution, P(Rg|r), of the radius of gyration for a given value of r. The free energy change versus Rg, -kBT ln P(Rg|r), is found to vary more gently compared to the corresponding variation in the excess hydration free energy. Using this observation within a multistate generalization of the potential distribution theorem, we calculate a tight upper bound for the hydration free energy of the peptide for a given r. On this basis, we find that peptide hydration greatly favors the expanded state of the chain, despite primitive hydrophobic effects favoring chain collapse. The net free energy of collapse is seen to be a delicate balance between opposing intrapeptide and hydration effects, with intrapeptide contributions favoring collapse.},
doi = {10.1021/acs.jpcb.7b05469},
journal = {Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry},
issn = {1520-6106},
number = 34,
volume = 121,
place = {United States},
year = {2017},
month = {8}
}