X‐ray studies on crystalline complexes involving amino acids and peptides. XXXVI. Crystal structures of hydrated glycyl‐l‐histidine andl‐histidyl‐l‐alanine complexes with oxalic acid

Abstract

The crystal structures of the complexes of oxalic acid with glycyl-L-histidine and L-histidyl-L-alanine were determined. The three crystallographically independent peptide molecules in the complexes have closed conformations. The terminal carboxyl group of the dipeptide and the oxalate ion in the Gly-His complex exhibit unusual ionization states and are connected by a symmetric O- - -O hydrogen bond. The peptide aggregation in the complex is almost identical to that in the corresponding semisuccinate complex and is similar to one of the predicted aggregation patterns for Ala-Ala, demonstrating that dipeptide aggregation is controlled primarily by main-chain interactions and is substantially unaffected by disturbing influences such as those arising from polar side chains, ions and water molecules. The peptide molecules in the highly pseudosymmetric crystals of the His-Ala complex, however, exhibit a hitherto unobserved aggregation pattern. Thus, in spite of the repeated occurrence of a few patterns, the possibility of the existence of new patterns needs to be taken into account.

Effects of conformation and hydrogen bonding on the CC and NCN stretching Raman bands of N‐deuterated histidinium

“…While obtaining the values of hydrogen bonding parameters, the positions of the H atoms bound to N π and N τ were calculated by assuming a standard NH bond length of 0.1009 nm20 and an NH direction equally bisecting the CNC angle. The use of a common NH bond geometry was based on the reason that the coordinates of hydrogen atoms were not available for some crystals,16, 18 and the accuracy of the reported hydrogen coordinates in the other crystals appeared to significantly differ from crystal to crystal 11–15, 17, 19. Normalization of the bond lengths of NH, OH, etc.…”

“…Ace‐His·D 2 O and His‐Ala·Oxa contain two crystallographically inequivalent molecules per unit cell 15, 19. The Raman spectrum of Ace‐His·D 2 O, however, exhibits only one Raman band in each of the ν CC and ν NCN wavenumber regions (trace 5 in Fig.…”

“…L ‐Histidine, DL ‐histidine, N ‐acetyl‐ L ‐histidine, L ‐histidyl‐ L ‐alanine, glycyl‐ L ‐histidine, and the other reagents required for the preparation of crystals containing N ‐deuterated histidinium were all obtained commercially. The crystals prepared were DL ‐histidine hydrochloride dihydrate ( DL ‐His·DCl · 2D 2 O),11 L ‐histidine hydrochloride monohydrate (His·DCl·D 2 O),12 L ‐histidine dihydrochloride (His· 2DCl),13 L ‐histidine trimesate‐1/3 acetone (His·Tma),14 N ‐acetyl‐ L ‐histidine monohydrate (Ace‐His·D 2 O),15 L ‐histidine oxalate (His·Oxa),16 DL ‐histidine bis(oxalate) ( DL ‐His· 2Oxa),16 L ‐histidine glycolate (His·Glc),17 L ‐histidine formate formic acid (His·Fmt),18 DL ‐histidine formate ( DL ‐His·Fmt),18 L ‐histidyl‐ L ‐alanine oxalate (His‐Ala·Oxa),19 and glycyl‐ L ‐histidine oxalate (Gly‐His·Oxa) 19. Deuterium replacement of the labile hydrogen atoms including those bound to N π and N τ was performed by lyophilization from dilute D 2 O solution prior to crystallization in DCl, D 2 O, D 2 O/acetone, or D 2 O/acetonitrile.…”

“…Deuterium replacement of the labile hydrogen atoms including those bound to N π and N τ was performed by lyophilization from dilute D 2 O solution prior to crystallization in DCl, D 2 O, D 2 O/acetone, or D 2 O/acetonitrile. The crystallization was achieved in glass capillaries according to the methods described in the papers on X‐ray or neutron crystallographic studies 11–19…”

The one-dimensional zigzag coordination polymercatena-poly[[[triaquazinc(II)]-μ-N,N′-(benzene-1,4-dicarboxamido)diacetato-κ2O:O′] dihydrate]

“…For example, an N-substituted aromatic amide has rigidity owing to the amide group (-CO-N-) conjugating with the aromatic ring, while the -rotation about the N-C bond could induce flexibility in the molecule. Moreover, the imine group N-H could serve as a better hydrogen-bonding donor and the amide C O could also act as a better hydrogen-bonding acceptor (Manoj & Vijayan, 2000). Therefore, we have designed and synthesized a semi-flexible amide ligand, 2,2 0 -[1,4-bis(benzamido)]diacetic acid (H 2 L), and employed it with Zn II ions to assemble the title coordination polymer, (I).…”