Showing papers by "George M. Sheldrick published in 1996"
01 Jan 1996
3,515 citations
TL;DR: The authors' structure confirms that vancomycin exists as an asymmetric dimer, and proposes that the asparagine sidechain may hold the binding pocket in a suitable conformation for peptide docking, swinging out of the way when the peptide enters the bindingpocket.
176 citations
TL;DR: In this paper, the crystal structure of a glycopeptide antibiotic A-40926 aglycone was investigated by X-ray analysis at −120° and a novel iterative real/reciprocal space procedure was successful.
Abstract: The crystal structure of a glycopeptide antibiotic A–40926 aglycone was investigated by X-ray analysis at −120°. A-40926 crystallises in the orthorhombic space group P212121 with two monomers in the asymmetric unit, a = 21.774(4), b = 28.603(7), c = 29.757(4) A. ‘Conventional’ direct methods approach failed to solve the structure, but a novel iterative real/reciprocal space procedure was successful. Refinement against 11248 F2 data led to R1 = 13.3% for 6770 F > 4σ (F). The two monomers of A-40926 have similar conformations and are bound by antiparallel H-bonds to form a ‘chain’ structure of connecting dimers. The antibiotic molecule possesses a ‘binding pocket’ for the C-terminal carboxy group of the cell-wall protein, which is consisten with suggestions based on NMR data and the recently reported crystal structure of ureido-balhimycin. In A-40926 the monomers are polymerically linked by H-bonds, quite unlike the tight dimer formation observed in ureido-balhimycin.
19 citations
TL;DR: The crystal structure of isocyclosporin A (1) has been determined at 193 (2) K as discussed by the authors, where K is the number of transannular and four intermolecular H-bonds.
Abstract: The crystal structure of isocyclosporin A (1), a rearrangement product of the immunosuppressant drug cyclosporin A, has been determined at 193 (2) K. Crystals are orthorhombic with cell dimensions a = 26.684 (7), b = 26.936 (3) A, c = 28.549 (7) A, space group C2221. The structure was solved by direct methods and refined by full-matrix least-squares methods to a conventional R value of 0.110. In contrast to the structure of cyclosprin A in solution and in the crystal, isocyclosporin A (1) has no regular secondary structural elements. The backbone adopts an open, irregular conformation with cis amide bonds between residue 2 and 3, and 3 and 4, respectively. All the other amide bonds and the ester linkage are trans. Contrary to crystal structures of cyclosporin derivatives, this crystal structure is stabilized by two transannular and four intermolecular H-bonds.
10 citations