Premium
Melanostatin conformations in solution
Author(s) -
Schwartz Robert W.,
Mattice Wayne L.,
Spirtes Morris A.
Publication year - 1979
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.1979.360180802
Subject(s) - chemistry , intramolecular force , molecule , intermolecular force , hydrogen bond , cationic polymerization , aqueous solution , monomer , solvent , crystallography , tripeptide , computational chemistry , stereochemistry , polymer , organic chemistry , biochemistry , amino acid
The conformations of melanostatin have been studied experimentally using CD spectroscopy and via calculations. In aqueous solution and 2,2,2‐trifluoroethanol (TFE) there is no evidence that monomers of the tripeptide exist in an ordered (β‐bend) structure. In water and TFE solutions (3–6 × 10 −4 M ) the neutral molecules aggregate very slowly, taking about 3 days to attain equilibrium at room temperature. At equivalent concentrations in TFE, although not in water, the cationic molecules also slowly aggregate, although to a lesser extent. Calculations using rotational isomeric state theory give the most probable unperturbed end‐to‐end distance of the molecule at 9.3 ± 0.1 Å and indicate that a vast majority of the molecules exist in some extended conformation, end‐to‐end distance ≥6 Å. Only 0.4% of the molecules are calculated to have O…H separations compatible with a β‐bend structure. An intramolecular hydrogen bond must have an energy at least 2 kcal/mol lower than that of an intermolecular hydrogen bond to solvent if a β‐bend is to be experimentally observable.