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.
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 P2(1)/n and P2(1), 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.
Saraswathi
N T
NT
Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India.
Vijayan
M
M
D018360:Crystallography, X-Ray; D006639:Histidine / Q000737:chemistry*; D006860:Hydrogen Bonding; D008314:Malonates / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D013237:Stereoisomerism
D008314:Malonates; D010455:Peptides; D006639:Histidine; C030290:malonic acid