ISSN:
1573-5001
Keywords:
J coupling
;
Rotamer averaging
;
γ-Gauche interaction
;
13C chemical shift
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary We have used a spin-echo difference NMR pulse sequence to measure three-bond J couplings between δ- and α-carbons of the leucine residues in a micelle-associated helical peptide dimer that corresponds to residues 62–101 of the transmembrane erythrocyte protein glycophorin A. The observed 3J couplings correlate strongly with the 13C chemical shift of the δ-methyl groups, and within experimental error both the shift distribution of the methyl carbons and the variations in 3J can be accounted for by variations in side-chain rotamer populations. We infer that all leucine side chains in this peptide dimer are in fast exchange among X 2 rotamers and sample two of the three possible rotameric states, even when the side chain forms part of the dimer interface. The observed correlation of chemical shift with couplings can be traced to a γ-gauche interaction of methyl and α-carbons. This correlation may provide an alternate route to rotamer analysis in some protein systems.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00202043
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