X-ray studies on crystalline complexes involving amino acids and peptides. XLI. Commonalities in aggregation and conformation revealed by the crystal structures of the pimelic acid complexes of L-arginine and DL-lysine

Saraswathi, N. T. ; Roy, S. ; Vijayan, M. (2003) X-ray studies on crystalline complexes involving amino acids and peptides. XLI. Commonalities in aggregation and conformation revealed by the crystal structures of the pimelic acid complexes of L-arginine and DL-lysine Acta Crystallographica Section B, 59 . pp. 641-646. ISSN 0108-7681

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Official URL: http://scripts.iucr.org/cgi-bin/paper?de0021

Related URL: http://dx.doi.org/10.1107/S0108768103013685

Abstract

The complexes of L-arginine and DL-lysine with pimelic acid are made up of singly positively charged zwitterionic amino acid cations and doubly negatively charged pimelate ions in a 2:1 ratio. In both structures, the amino acid molecules form twofold symmetric or centrosymmetric pairs that are stabilized by hydrogen bonds involving α-amino and α-carboxylate groups. In the L-arginine complex, these pairs form columns along the shortest cell dimension, stabilized by intermolecular hydrogen bonds involving α-amino and α-carboxylate groups. The columns are connected by hydrogen bonds and water bridges to give rise to an amino acid layer. Adjacent layers are then connected by pimelate ions. Unlike molecular ions aggregate into alternating distinct layers in the DL-lysine complex. In the amino acid layer, hydrogen-bonded lysinium dimers related by a glide plane are connected by hydrogen bonds involving α-amino and α-carboxylate groups into head-to-tail sequences. Interestingly, the aggregation pattern observed in L-arginine hemipimelate monohydrate is very similar to those in DL-arginine formate dihydrate, DL-arginine acetate monohydrate and L-arginine hemiglutarate monohydrate. Similarly, the aggregation of amino acid molecules is very similar in DL-lysine hemipimelate 0.53-hydrate, DL-lysine formate and DL-lysine hydrochloride. The complexes thus demonstrate how, in related structures, the effects of a change in composition, and sometimes even those of reversal in chirality, can be accommodated by minor adjustments in essentially the same aggregation pattern. It also transpires that the conformation of the argininium ion is the same in the four argininium complexes; the same is true about the conformation of the lysinium ion in the three lysinium complexes. This result indicates a relation between, and mutual dependence of, conformation and aggregation.

Item Type:Article
Source:Copyright of this article belongs to International Union of Crystallography.
Keywords:Amino Acids; Aggregation Patterns; Molecular Conformations
ID Code:53873
Deposited On:10 Aug 2011 09:35
Last Modified:10 Aug 2011 09:35

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