Acta Crystallographica Section B

Structural Science

Volume 58, Part 4 (August 2002)

research papers

Acta Cryst. (2002). B58, 734-739 [ doi:10.1107/S0108768102008819 ]

X-ray studies on crystalline complexes involving amino acids and peptides. XXXIX. Crystal structures of malonic acid complexes of DL- and L-histidine. Preservation of aggregation pattern on reversal of chirality

N. T. Saraswathi and M. Vijayan

Abstract: The malonic acid complexes of DL- and L-histidine are made up of zwitterionic positively charged histidinium ions and semimalonate (hydrogen malonate) ions. They crystallise in space groups P2₁/n and P2₁, respectively, with nearly the same unit-cell parameters. The molecules aggregate in the two complexes in a remarkably similar manner. The two sets of crystallographically independent molecules are related by a pseudo-glide plane. This pseudo-symmetry is almost exact except in the case of the [alpha] -carboxylate group and, to some extent, the [alpha] -C and the [alpha] -N atoms. Preservation of the aggregation pattern to such an extent on the reversal of chirality of half the amino-acid molecules is observed for the first time in amino-acid complexes. This is achieved at the cost of considerable conformational strain in one of the two histidinium ions in the L-histidine complex.

Keywords: amino acids; peptides; DL-histidine; L-histidine; preservation of aggregation pattern.


	Structure factor file (CIF format) (105.0 kbytes) Contains datablock DL

	Structure factor file (CIF format) (105.5 kbytes) Contains datablock L

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