Fragmentation studies of pentacoordinated bisaminoacylspirophosphoranes by negative electrospray ionization mass spectrometry.
Fragmentation pathways of a series of pentacoordinated bisaminoacylspirophosphoranes were elucidated by electrospray ionization multistage mass spectrometry (ESI-MS(n)) in negative mode. The deprotonated ions of pentacoordinated bisaminoacylspirophosphoranes tend to eliminate a corresponding amino acid to form base peak. The hydrogen/deuterium exchange experiment, the high-resolution mass spectrometry, (13)C stable isotope labeling experiment and theoretical calculations were used to rationalize the proposed fragmentation pathways and to verify the differences between the fragmentation pathways. The results indicate that the negative molecular ions of pentacoordinated bisaminoacylspirophosphoranes dissociate through its open-chain tricoordinated tautomers. The relative Gibbs free energies (ΔG) of the product ions and proposed fragmentation pathways were estimated using the B3LYP/6-31 + + G(d, p) model. The results have some potential applications in the identification structures of similar spirophosphorane compounds by ESI-MS(n).
Chemical confirmation of a pentavalent phosphorane in complex with beta-phosphoglucomutase.
This communication reports the X-ray crystal structure of the alpha-d-galactose-1-phosphate complex with that of Lactococcus lactis beta-phosphoglucomutase (beta-PGM) crystallized in the presence of Mg2+ cofactor and the enzyme-to-phosphorus ratio determined by protein and phosphate analyses of the crystalline complex. The 1:1 ratio determined for this complex was compared to the 1:2 ratio determined for the crystals of beta-PGM grown in the presence of substrate and Mg2+ cofactor. This result verifies the published structure assignment of this latter complex as the phosphorane adduct formed by covalent bonding between the active site Asp8 carboxylate to the C(1)phosphorus of the beta-glucose 1,6-bisphosphate ligand and rules out the proposal of a beta-PGM-glucose-6-phosphate-1-MgF3- complex.
Mécanisme de formation et de transformation des spirophosphoranes : V. Synthèse et tautomérie PIII ⇌ PV des spirophosphoranes liaison PH dérivant des α aminoalcools substitués au carbone et à l'azote
The synthesis of about forty new spirophosphoranes containing a PH bond offers examples of new cases of tautomeric equilibrium between the triand pentacoordinated forms as shown by: (a) recording the 31P NMR spectra between 20 and 150°, (b) using a chemical test which is specific of the PIII form. These results allowed us to discuss factors influencing the equilibrium PIII ⇌ PV.