Free energy barrier estimation of unfolding the alpha-helical surfactant-associated polypeptide C

Zangi, R., Kovacs, H., van Gunsteren, W. F., Johansson, J. and Mark, A. E. (2001) Free energy barrier estimation of unfolding the alpha-helical surfactant-associated polypeptide C. Proteins-structure Function And Genetics, 43 4: 395-402. doi:10.1002/prot.1052


Author Zangi, R.
Kovacs, H.
van Gunsteren, W. F.
Johansson, J.
Mark, A. E.
Title Free energy barrier estimation of unfolding the alpha-helical surfactant-associated polypeptide C
Journal name Proteins-structure Function And Genetics   Check publisher's open access policy
ISSN 0887-3585
Publication date 2001-01-01
Sub-type Article (original research)
DOI 10.1002/prot.1052
Volume 43
Issue 4
Start page 395
End page 402
Total pages 8
Place of publication New York
Publisher Wiley-liss
Language eng
Abstract Molecular dynamics simulations were conducted to estimate the free energy barrier of unfolding surfactant-associated polypeptide C (SP-C) from an or-helical conformation. Experimental studies indicate that while the helical fold of SP-C is thermodynamically stable in phospholipid micelles, it is metastable in a mixed organic solvent of CHCl3/CH3OH/0.1 M HCl at 32:64:5 (v/v/v), in which it undergoes an irreversible transformation to an insoluble aggregate that contains beta -sheet. On the basis of experimental observations, the free energy barrier was estimated to be similar to 100 kJ/mole by applying Eyring's transition state theory to the experimental rate of unfolding [Protein Sci 1998;7:2533-2540]. These studies prompted us to carry out simulations to investigate the unwinding process of two helical turns encompassing residues 25-32 in water and in methanol. The results give an upper bound estimation for the free energy barrier of unfolding of SP-C of similar to 20 kJ/mole. The results suggest a need to reconsider the applicability of a single-mode activated process theory to protein unfolding. Proteins 2001; 43:395-402. (C) 2001 Wiley-Liss, Inc.
Keyword Biochemistry & Molecular Biology
Biophysics
MD simulations
free energy barrier
alpha-SP-C
protein unfolding
Molecular-dynamics Simulations
Protein Sp-c
Pulmonary Surfactant
Secondary Structure
Water
Orientation
Peptides
System
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Chemistry and Molecular Biosciences
 
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Created: Thu, 20 Sep 2007, 02:28:06 EST