ORCID Profile
0000-0002-2655-0313
Current Organisation
CNRS
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Publisher: American Chemical Society (ACS)
Date: 15-03-2018
Abstract: A comparative study of syn vs anti carboxylic acids in hybrid peptides based on experimental electron density studies and theoretical calculations shows that, in the anti form, all three bond angles surrounding C
Publisher: International Union of Crystallography (IUCr)
Date: 27-03-2015
DOI: 10.1107/S1399004715002382
Abstract: Examination of protein structure at the subatomic level is required to improve the understanding of enzymatic function. For this purpose, X-ray diffraction data have been collected at 100 K from cholesterol oxidase crystals using synchrotron radiation to an optical resolution of 0.94 Å. After refinement using the spherical atom model, nonmodelled bonding peaks were detected in the Fourier residual electron density on some of the in idual bonds. Well defined bond density was observed in the peptide plane after averaging maps on the residues with the lowest thermal motion. The multipolar electron density of the protein–cofactor complex was modelled by transfer of the ELMAM2 charge-density database, and the topology of the intermolecular interactions between the protein and the flavin adenine dinucleotide (FAD) cofactor was subsequently investigated. Taking advantage of the high resolution of the structure, the stereochemistry of main-chain bond lengths and of C=O...H—N hydrogen bonds was analyzed with respect to the different secondary-structure elements.
Publisher: International Union of Crystallography (IUCr)
Date: 23-03-2022
DOI: 10.1107/S2052520622001457
Abstract: A new cocrystal hydrate of gallic acid with pyrazine (4GA, Py, 4H 2 O GA 4 PyW 4 ) was obtained and characterized by single crystal X-ray diffraction. In addition to structure determination, experimental charge density analysis was carried out in terms of Multipole Modelling (MP), X-ray wavefunction refinement (XWR) and maximum entropy method (MEM). As a part of XWR, the structural refinement via Hirshfeld atom refinement was carried out and resulted in O—H bond lengths close to values from neutron diffraction. A systematic comparison of molecular conformations and aromatic interactions in this new cocrystal hydrate was performed with other existing polymorphs of gallic acid. In GA 4 PyW 4 , the two symmetry-independent gallic acid molecules have a syn COOH orientation and form the common (COOH) 2 dimeric synthon. The carboxyl C atom displays the characteristics of π-holes with electropositive regions above and below the molecular plane and engages in acceptor–donor interactions with oxygen atoms of acidic O—H groups and phenol groups of neighbouring gallic acid molecules. The signature of the π-hole was identified from experimental charge density analysis, both in static density maps in MP and XWR as well as dynamic density in MEM, but it cannot be pinned down to a specific atom–atom interaction. This study presents the first comparison between an XWR and a MEM experimental electron-density determination.
Publisher: International Union of Crystallography (IUCr)
Date: 26-01-2011
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