Biomedical subjects
Publications and source records attributed to David VanderVelde.
Multiple deuterium exchange between DMSO-d6 and amide hydrogens in two hexaamido cryptand fluoride receptors has been verified by 19F and 2H NMR and FAB mass spectral studies. Structural results for one of the complexes indicate a tricapped trigonal prism hydrogen bond coordination geometry around an encapsulated fluoride, with hydrogen bonds from fluoride to six amide and three phenyl hydrogens.
The Asn residue in the pentapeptide Asn-Gln-Asn-Glu-Gly undergoes racemization at the Calpha center in the course of deamidation of this residue through a succinimide intermediate. The succinimide intermediate is known to racemize at the corresponding center, leading to racemized products of deamidation. Return of this intermediate to reactant Asn is very unlikely in dilute solution where attack of product ammonia on the succinimide is precluded, and Asn racemization has not been previously observed. We give evidence that the observed racemization occurs at the tetrahedral-intermediate stage preceding the succinimide intermediate. The observation is significant for protein stability in vivo and in vitro and has importance in medicine, food chemistry, and archaeological/palaeological dating.
An anion receptor derived from a tren-based amide cryptand with pyridine spacers has been synthesized and characterized. Two crystal structures are reported: the hydrochloride salt and the fluoride complex. The cryptand shows extremely high binding with fluoride ion in DMSO-d6. Both the crystal structure and solution 19F NMR data indicate an encapsulated fluoride ion with very high symmetry.