X-ray Studies on Crystalline Complexes Involving Amino Acids and Peptides. XIII. Effect of Chirality on Molecular Aggregation: The Crystal Structures of $L$-Arginine $D$-Aspartate and $L$-Arginine $D$-Glutamate Trihydrate

Suresh, CG and Ramaswamy, Jayanthi and Vijayan, M (1986) X-ray Studies on Crystalline Complexes Involving Amino Acids and Peptides. XIII. Effect of Chirality on Molecular Aggregation: The Crystal Structures of $L$-Arginine $D$-Aspartate and $L$-Arginine $D$-Glutamate Trihydrate. In: Acta Crystallographica, B42 (5). pp. 473-478.

 PDF x_ray_studies.pdf Restricted to Registered users only Download (707Kb) | Request a copy

Abstract

The crystal structures of (1) $L$-arginine $D$-asparate, $C_6$$H_15N_4$$0_2^+.C_4H_6NO_4^-$ [triclinic, P1, a = 5.239(1), b = 9.544(1), $c = 14.064(2) \AA$, $\alpha = 85.58(1)$, $\beta = 88.73 (1)$, $\gamma = 84.35 (1)^0$, Z = 2] and (2) $L$-arginine $D$-glutamate trihydrate, $C_6H_15N_40^-.3H_20$ [monoclinic, $P_2_1$, a = 9.968(2), b = 4.652(1), $c = 19.930 (2) \AA$, $\beta = 101.20 (1)^0$, Z = 2] have been determined using direct methods. They have been refined to R =0.042 and 0.048 for 2829 and 2035 unique reflections respectively $[I>2 \sigma (I)]$. The conformations of the two arginine molecules in the aspartate complex are different from those observed so far in the crystal structures of arginine, its salts and complexes. In both complexes, the molecules are organized into double layers stacked along the longest axis. The core of each double layer consists of two parallel sheets made up of main-chain atoms, each involving both types of molecules. The hydrogen bonds within each sheet and those that interconnect the two sheets give rise to $LL$-, $DD$- and $DL$-type head-to-tail sequences. Adjacent double layers in (1) are held together by side-chain-side-chain interactions whereas those in (2) are interconnected through an extensive network of water molecules which interact with sidechain guanidyl and carboxylate groups. The aggregation pattern observed in the two $LD$ complexes is fundamentally different from that found in the corresponding $LL$ complexes.

Item Type: Journal Article Copyright of this article belongs to International Union of Crystallography. Division of Biological Sciences > Molecular Biophysics Unit 24 Jun 2008 19 Sep 2010 04:46 http://eprints.iisc.ernet.in/id/eprint/14638