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Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/100/14253

Title: Stereochemistry and Solvent Role in Protein Folding: Nuclear Magnetic Resonance and Molecular Dynamics Studies of Poly-L and Alternating-L,D Homopolypeptides in Dimethyl Sulfoxide
Authors: SRIVASTAVA, KR
KUMAR, A
GOYAL, B
DURANI, S
Keywords: PARTICLE MESH EWALD
POLYPROLINE-II
CONFORMATIONAL PREFERENCES
BACKBONE CONFORMATION
POLYPEPTIDE-CHAINS
UNFOLDED PROTEINS
ALPHA-HELICES
PEPTIDE
SOLVATION
SEQUENCE
Issue Date: 2011
Publisher: AMER CHEMICAL SOC
Citation: JOURNAL OF PHYSICAL CHEMISTRY B,115(20)6700-6708
Abstract: The competing interactions folding and unfolding protein structure remain obscure. Using homopolypeptides, we ask if poly-L structure may have a role. We mutate the structure to alternating-L,D stereochemistry and substitute water as the fold-promoting solvent with methanol and dimethyl sulfoxide (DMSO) as the fold-denaturing solvents. Circular dichroism and molecular dynamics established previously that, while both isomers were folded in water, the poly-L isomer was unfolded and alternating-L,D isomer folded in methanol. Nuclear magnetic resonance and molecular dynamics establish now that both isomers are unfolded in DMSO. We calculated energetics of folding-unfolding equilibrium with water and methanol as solvents. We have now calculated interactions of unfolded polypeptide structures with DMSO as solvent. Methanol was found to unfold and water fold poly-L structure as a dielectric. DMSO has now been found to unfold both poly-L and alternating-L,D structures by strong solvation of peptides to disrupt their hydrogen bonds. Accordingly, we propose that while linked peptides fold protein structure with hydrogen bonds they unfold the structure electrostatically due to the stereochemical effect of the poly-L structure. Protein folding to ordering of peptide hydrogen bonds with water as canonical solvent may thus involve two specific and independent solvent effects-one, strong screening of electrostatics of poly-L linked peptides, and two, weak dipolar solvation of peptides. Correspondingly, protein denaturation may involve two independent solvent effects-one, weak dielectric to unfold poly-L structure electrostatically, and two, strong polarity to disrupt peptide hydrogen bonds by solvation of peptides.
URI: http://dx.doi.org/10.1021/jp200743w
http://dspace.library.iitb.ac.in/jspui/handle/100/14253
ISSN: 1520-6106
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