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A conformational analysis of leucine enkephalin as a function of pH
Author(s) -
Aburi Mahalaxmi,
Smith Paul E.
Publication year - 2002
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.10158
Subject(s) - chemistry , hydrogen bond , intramolecular force , peptide , crystallography , aqueous solution , enkephalin , stereochemistry , side chain , molecule , organic chemistry , biochemistry , receptor , opioid , polymer
The conformations of Leu enkephalin in aqueous solution have been investigated as a function of pH using molecular dynamics simulations. The simulations suggest the peptide backbone exists as a mixture of folded and unfolded forms (approximately 50% each) at neutral pH, but is always unfolded at low or high pH. The folded form at neutral pH possesses a 2 → 5 hydrogen bond and a close head to tail separation. No significant intramolecular hydrogen bonding of the carbonyl oxygens was observed in either the folded or unfolded forms of the peptide. Analysis of the Gly carbonyl oxygens and terminal groups indicated that, while the conformational population distribution of Leu enkephalin did vary noticeably as a function of pH, their hydration was essentially independent of pH and in agreement with the available NMR data. Further study indicated that the unfolded state of the peptide was not random in nature and consisted of one major unfolded backbone arrangement stabilized by a persistent hydrophobic interaction between the side chains of Tyr and Leu. © 2002 Wiley Periodicals, Inc. Biopolymers 64: 177–188, 2002