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The role of water in the crystal structure of N ‐acetyl‐ L ‐4‐hydroxyproline
Author(s) -
Hospital M.,
Courseille C.,
Leroy F.,
Roques B. P.
Publication year - 1979
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.1979.360180509
Subject(s) - chemistry , orthorhombic crystal system , molecule , collagen helix , hydrogen bond , crystal structure , pyrrolidine , crystallography , ring (chemistry) , crystal (programming language) , stereochemistry , hydroxyproline , group (periodic table) , triple helix , organic chemistry , biochemistry , computer science , programming language
The crystal structure of N ‐acetyl‐ L ‐4‐hydroxyproline (Hyp) was determined by direct methods. (The crystal is orthorhombic with the space group P 2 1 2 1 2 1 .) The acetyl group is in the trans conformation and the pyrrolidine ring puckers at C γ (C s C γ envelope), as in most Hyp residues. According to the rotation angle ψ = −30°, the N ‐acetyl‐ L ‐4Hyp has the same conformation as an α‐helix of prolyl residues. The crystal packing is stabilized by hydrogen bonds between three different molecules and the same molecule of water. One of the water bridges involves the carbonyl of the N ‐acetyl group of one molecule and the hydrogen atom of the 4‐OH group of another. Such an arrangement has been proposed to explain the high stability of (Gly‐ L ‐Pro‐ L ‐4Hyp) n . A second bridge involves the two hydrogens of the water molecule and the carbonyl groups of two neighbouring molecules, as already proposed in a dihydrated model of collagen. These experimental features, which are discussed in relation to the different models of collagen, allow us to propose an hypothetical arrangement for the water molecule which is strongly retained in the triple helix of (Gly‐ L ‐Pro‐ L ‐4Hyp) n .