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The role of water in the crystal structure of N-acetyl-L-4-hydroxyproline

✍ Scribed by M. Hospital; C. Courseille; F. Leroy; B. P. Roques

Publisher
Wiley (John Wiley & Sons)
Year
1979
Tongue
English
Weight
358 KB
Volume
18
Category
Article
ISSN
0006-3525

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✦ Synopsis

The crystal structure of N-acetyl-~-4-hydroxyproline (Hyp) was determined by direct methods. (The crystal is orthorhombic with the space group P212121.) The acetyl group is in the trans conformation and the pyrrolidine ring puckers a t Cr (CsCr envelope), as in most Hyp residues. According to the rotation angle J/ = -30°, the N-acetyl-~-.iHyp has the same conformation as an a-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-~-Pro-L-4Hyp),. A second bridge involves the two hydrogens of the water molecule and the carbonyl groups of two neighboring 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 ( G ~Y -L -P ~O -L -~H ~~) , , .

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