Structure cristalline de dérivés d'acides aminés. I. L-Alanylglycine

Abstract

The crystal structure of L-alanylglycine has been determined by X-ray diffraction. L-Alanylglycine crystallizes in the space group P21 with cell dimensions a= 5.283, b= 11.810, c= 5.510/~ andfl= 101-58 ° with Z=2. This non-centrosymnaetric structure was solved by the 'quadrant permutation' method. The structure is simple but interesting in that one proceeded from the collection of data to the correct solution with scarcely any human intervention. It was refined by three-dimensional anisotropic matrix least-squares analysis (block-diagonal approximation). A final R index of 0.047 for 586 observed reflexions was obtained. The molecules are held together by hydrogen bonds forming a three-dimensional network. The planes of the carboxyl and the amide groups are nearly perpendicular. The bond lengths and angles are in close agreement with the mean values proposed by Marsh & Donohue.

Theoretical 13C chemical shift, 14N, and 2H quadrupole coupling‐ constant studies of hydrogen bonding in L‐alanylglycine dipeptide

“…There is experimental data just for the amide 2 H nucleus of L-alagly dipeptide. [19] With regard to the atomic distances reported in the literature for Lalagly, [21] L-alanine, [27] and glygly, [28] we compare the calculated results for the other nuclei of L-alanine and glycine residues with those of L-alanine amino acid [29,30] and the glygly dipeptide, [30] respectively. Three hydrogen nuclei from L-alanine [27] form strong hydrogen bonds with the oxygen atoms of the carboxyl groups of the neighboring molecules; the same is true for the L-alagly dipeptide.…”

“…[21] Koch and Germain did not report atomic coordinates of the hydrogen nuclei of the methyl group of L-alanine residue. [21] In our work, these nuclei were placed in a plane perpendicular to C-C bond direction, and at a distance determined by the experimental C-H bond length, such that the steric interference with neighboring groups was minimized. The coordinates were improved by partial geometry optimization of a single L-alagly molecule, with all of the other nuclei frozen.…”

“…[21] Therefore its chemical-shift changes have little dependence on hydrogen-bond formation. Hence for interpreting the results for this nucleus, we resort to the effects of neighboring groups.…”

The crystal structure of diglycine sulphate monohydrate

“…Thus we think that the difference in the C-O length is more significant than the nitrogen-plane separation as a test of the zwitterion character. From other studies (Marsh, 1958;Koch & Germain, 1970;Alml6f, Kvick & Thomas, 1973;Destrada, Forel & Garrigan-Lagrange, 1973;Mohana & Viswamitra, 1972; and references therein) it seems that the NH + group is formed if there is something capable of donating a proton, and the remaining H atoms subsequently fill the convenient chemical sites. The NH + and CH2 groups form a staggered configuration with minimal overlapping.…”

The crystal and molecular structure of N-(2-chloroethyl)-D-gluconamide

“…The N atom has the greatest deviation 0.037 A from the amide plane as was also observed by Johnson (1966) in the structure of an ~-D-glucosamine. The dimensions of the group do not differ significantly from those of amide groups in structures of dipeptides (Biswas, Hughes, Sharma & Wilson, 1968;Koch & Germain, 1970) and other simple peptides and related substances (Corey & Pauling, 1953), with the C(1)-N bond of 1.340 A exhibiting partial double-bond character typical of amides.…”