X‐ray studies on crystalline complexes involving amino acids and peptides. IX. Crystal structure of l‐ornithine l‐aspartate hemihydrate
- 1 August 1983
- journal article
- research article
- Published by Wiley in International Journal of Peptide and Protein Research
- Vol. 22 (2) , 154-160
- https://doi.org/10.1111/j.1399-3011.1983.tb02080.x
Abstract
L-Ornithine L-aspartate hemihydrate crystallizes in the space group C2 with a = 21.858(2), b = 4.718(1), c = 18.046(2) .ANG. and .beta. = 137.4(1).degree.. The crystal structure, solved by direct methods, was refined to an R value of 0.041 for 1270 observed reflections. The conformation of the 2 amino acid molecules in the structure are somewhat different from those observed in other crystal structures which contain them. The crystal structure is stabilized by ionic interactions accompanied by H-bonds. The unlike molecules aggregate into separate 2-fold helices; each helix of one type is surrounded by, and is in H-bonded contact with, 4 helices of the other type. The structure can be described as consisting of alternating, hydrophilic and hydrophobic regions. The hydrophilic regions contain H-bonded loops, each made up of 2 amino groups and 2 carboxylate groups. The structure also provides the 1st example of a head-to-tail sequence involving 2 types of amino acids. [This type of sequence may be of relevance to prebiotic polymerization.].Keywords
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