X-ray studies of crystalline complexes involving amino acids and peptides. XLIV. Invariant features of supramolecular association and chiral effects in the complexes of arginine and lysine with tartaric acid

Selvaraj, M and Thamotharan, S and Roy, Siddhartha and Vijayan, M (2007) X-ray studies of crystalline complexes involving amino acids and peptides. XLIV. Invariant features of supramolecular association and chiral effects in the complexes of arginine and lysine with tartaric acid. In: Acta Crystallographica Section B: Structural Science, 63 (3). pp. 459-468.

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Abstract

The tartaric acid complexes with arginine and lysine exhibit two stoichiometries depending upon the ionization state of the anion. The structures reported here are $DL$-argininium $DL$hydrogen tartrate, bis($L$-argininium) $L$-tartrate, bis($DL$-lysinium) $DL$-tartrate monohydrate, $L$-lysinium $D$-hydrogen tartrate and $L$-lysinium $L$-hydrogen tartrate. During crystallization, $L$-lysine preferentially interacts with $D$-tartaric acid to form a complex when $DL$-tartaric acid is used in the experiment. The anions and the cations aggregate into separate alternating layers in four of the five complexes. In bis($L$-argininium) $L$-tartrate, the amino acid layers are interconnected by individual tartrate ions which do not interact among themselves. The aggregation of argininium ions in the $DL$- and the $L$-arginine complexes is remarkably similar, which is in turn similar to those observed in other dicarboxylic acid complexes of arginine. Thus, argininium ions have a tendency to assume similar patterns of aggregation, which are largely unaffected by a change in the chemistry of partner molecules such as the introduction of hydroxyl groups or a change in chirality or stoichiometry. On the contrary, the lysinium ions exhibit fundamentally different aggregation patterns in the $DL-DL$ complexes on the one hand and $L-D$ and $L-L$ complexes on the other. Interestingly, the pattern in the $L-D$ complex is similar to that in the $L-L$ complex. The lysinium ions in the $DL-DL$ complex exhibit an aggregation pattern similar to those observed in the $DL$-lysine complexes involving other dicarboxylic acids. Thus, the effect of change in the chirality of a subset of the component complexes could be profound or marginal, in an unpredictable manner. The relevant crystal structures appear to indicate that the preference of $L$-lysine for $D$-tartaric acid is perhaps caused by chiral discrimination resulting from the amplification of a small energy difference.

Item Type:	Journal Article
Publication:	Acta Crystallographica Section B: Structural Science
Publisher:	International Union of Crystallography
Additional Information:	Copyright of this article belongs to International Union of Crystallography.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	25 Jun 2008
Last Modified:	19 Sep 2010 04:46
URI:	http://eprints.iisc.ac.in/id/eprint/14591

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