In:
Chemistry – A European Journal, Wiley, Vol. 15, No. 32 ( 2009-08-10), p. 8015-8025
Abstract:
C α ‐Methyl‐ L ‐proline, or L ‐(αMe)Pro, is probably the most conformationally constrained α‐amino acid. In particular, its ω and ϕ torsion angles are restricted to about 180 and −60°, respectively, and only three ranges of values are theoretically available for ψ in mono‐ or longer peptides, namely, about −30° ( cis′ , 3 10 /α‐helical structure), 60° (inverse γ turn), or 140° ( trans′ , poly( L ‐Pro) n II structure). In this work, we examined the tendency of a number of N α ‐acyl dipeptide N′‐alkylamides of the type RCO‐(αMe)Pro‐Xxx‐NHR′ or RCO‐Xxx‐(αMe)Pro‐NHR′, in which Xxx is L (or D )‐Ala, Aib (α‐aminoisoburyric acid), or L (or D )‐(αMe)Pro, long enough to fold into intramolecularly hydrogen‐bonded γ or β turns. The results are compared with those obtained for the corresponding dipeptides based on Pro, a well‐known turn‐forming residue. For the crystal‐state 3D‐structural analysis we used X‐ray diffraction, whereas our solution conformational analysis was heavily based on the FTIR absorption and 1 H and 13 C NMR spectroscopy techniques. We conclude that (αMe)Pro is able to explore both trans′ and cis′ ψ areas of the conformational space, but in (αMe)Pro the latter is overwhelmingly more populated, in marked contrast to the Pro preference. This finding is a clear indication that in (αMe)Pro the major 3D‐structural determinant is the C α ‐methyl group. The circular dichroism (CD) signature of a peptide type III′ β‐turn conformation is also proposed.
Type of Medium:
Online Resource
ISSN:
0947-6539
,
1521-3765
DOI:
10.1002/chem.200900688
Language:
English
Publisher:
Wiley
Publication Date:
2009
detail.hit.zdb_id:
1478547-X
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