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Conformations and time‐resolved fluorescence of oligomers of (−)‐epicatechin with 4β → 8 interflavan bonds
Author(s) -
Cho Donghwan,
Porter Lawrence J.,
Mattice Wayne L.
Publication year - 1991
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.360310509
Subject(s) - chemistry , monomer , trimer , pentamer , oligomer , tetramer , fluorescence , dimer , crystallography , stereochemistry , polymer chemistry , polymer , organic chemistry , biochemistry , physics , quantum mechanics , enzyme
Abstract Oligomers of (−)‐epicatechin with 4β → 8 interflavan bonds, and as many as five monomer units, have been studied by conformational analysis and time‐resolved fluorescence. The conformational analysis yields 2 x −1 conformations for each oligomer with x monomer units. There are two conformations accessible at each interflavan bond. These conformations are denoted by + and −. The dominant conformations for the trimer and higher oligomers have an interaction between the phenolic hydroxyl groups on monomers i and i +2. This interaction involves the hydroxyl group at C(5) on monomer i , and either C(13) or C(8) of monomer i +2, depending on whether the conformation of the two intervening interflavan bonds is + + or + −, respectively. Minor contributions to the ensemble for the tetramer and pentamer are made by conformations that contain the sequence of successive interflavan bonds denoted by −+ or −−. In −+ the interaction between monomer units i and i + 2 involves an aliphatic hydroxyl with a phenolic hydroxyl, and there are no hydroxyl‐hydroxyl interactions between units i and i + 2 in −−. The onset of a different decay law for the fluorescence when x increases from 3 to 4 may be associated with the appearance of the −+ and −− conformations as minor constituents in the ensemble.