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Interpretation of energy‐transfer experiments by theoretical studies of model compounds using semiempirical potential functions. I. Three‐linked aromatic peptide units
Author(s) -
Guillard R.,
Englert A.
Publication year - 1976
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.1976.360150707
Subject(s) - chemistry , dipole , interpretation (philosophy) , computational chemistry , torsion (gastropod) , degrees of freedom (physics and chemistry) , valence (chemistry) , side chain , orientation (vector space) , chemical physics , thermodynamics , statistical physics , physics , geometry , organic chemistry , mathematics , polymer , medicine , surgery , computer science , programming language
It is shown that theoretical conformational analysis, based on the evaluation of semiempirical potential functions, can be used to compute the quantities relevant to the interpretation of energy‐transfer experiments. The relevant properties are computed for a segment of a polypeptide chain with the sequence Tyr‐Tyr. In particular, the average value of the orientation factor 〈κ 2 〉 and its distribution ƒ(κ 2 ) are examined. It appears that the degrees of freedom for rotation of the side chains are not sufficient to randomize completely the orientation factor of the transition dipoles. Two additional degrees of freedom, namely the torsion angles around the valence bonds of the backbone, ψ 1 and ϕ 2 , bring 〈κ 2 〉 close to the value that corresponds to randomly oriented transition dipoles.