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On Intrahelical Hydrogen Bonding and Stability of β‐Helices: The behavior of some D , L ‐alternating oligoleucines with an N ‐methylated residue
Author(s) -
Römer Daniel Urs,
FenudeSchoch Emma,
Lorenzi Gian Paolo,
Rüegger Heinz
Publication year - 1993
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19930760129
Subject(s) - chemistry , hydrogen bond , residue (chemistry) , oligopeptide , crystallography , stereochemistry , helix (gastropod) , peptide , molecule , organic chemistry , biochemistry , snail , biology , ecology
An N methylated residue at the n – 3 position of the chain was used to reduce the maximum number of H‐bonds realizable y some D , L ‐alternating oligopeptides in β 4.4 ‐, ↑↑ 5.6 ‐ and ↑↓ 5.6 ‐helices and thus increase for the oligopeptides, the relative stability of larger β‐helices. With D , L ‐alternating oligoleucines of the series Boc‐Leu n ‐OMe, however, this approach did not produce the helices expected. Although ↑↓ 7.2 ‐helices with only one free NH per strand would theoretically be possible, the N ‐methylated oligoleucines formed instead flawed β 4.4 ‐helices having three free NH's in CHCl 3 as well as in other solvents of low polarity. These observations confirm that the stability of β‐helices does not depend only on the number of intra‐or interstrand H‐bonds, and corroborate the idea that β‐helices with large cavities are inherently unstable.