title: 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.
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.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India.
authors.forename: M
authors.initials: M
authors.lastname: Selvaraj
authors.forename: S
authors.initials: S
authors.lastname: Thamotharan
authors.forename: Siddhartha
authors.initials: S
authors.lastname: Roy
authors.forename: M
authors.initials: M
authors.lastname: Vijayan
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D001120:Arginine / Q000737:chemistry; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008239:Lysine / Q000737:chemistry; D046911:Macromolecular Substances / Q000737:chemistry; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D013237:Stereoisomerism; D013644:Tartrates / Q000737:chemistry
chemical_list: D000596:Amino Acids; D046911:Macromolecular Substances; D010455:Peptides; D013644:Tartrates; D001120:Arginine; D008239:Lysine; C029768:tartaric acid