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Conformational studies on the hypothalamic thyrotropin releasing factor and related compounds by 1 H nuclear magnetic resonance spectroscopy
Author(s) -
Donzel B.,
Rivier J.,
Goodman M.
Publication year - 1974
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.1974.360131217
Subject(s) - chemistry , side chain , steric effects , nuclear magnetic resonance spectroscopy , resonance (particle physics) , stereochemistry , hydrogen bond , dipole , carboxamide , molecule , crystallography , nuclear magnetic resonance , organic chemistry , physics , particle physics , polymer
Proton magnetic resonance studies at 220 MHz were carried out on the hypothalamic thyrotropin releasing factor (TRF) and a variety of synthetic analogs designed to yield specific information about side chain–side chain and side chain–backbone interactions. The results show that the very low field resonance position of one of the carboxamide protons observed for TRF dissolved in dimethylsulfoxide is neither caused by a seven‐membered nor by a ten‐membered hydrogen bonded ring, but rather is due to a short range interaction between the unprotonated histidyl side chain and the carboxamide residue. A systematic study of the preferred histidyl side chain conformation in various TRF analogs is in good agreement with this interpretation. It was demonstrated that this interaction is not strong enough to cause significant changes in the preferred back bone conformation of the hormone. The possibilities for typical dipole–dipole interaction are discussed. No such interaction has been detected in TRF dissolved in water. We conclude that the tertiary structure of TRF in polar solvents is determined primarily by the steric characteristics of the bulky side chains which maintain the molecule preferentially in an extended conformation.