RESUMO
A tensorial formalism adapted to the case of transition-metal hexafluorides in a degenerate electronic state has been developed on the basis of preceding works about spherical-top molecules in a nondegenerate electronic state. We have introduced electronic operators constructed using group theory features and some physical considerations. Vibronic couplings (Jahn-Teller effect, etc.) have been reviewed for the triply degenerate vibrational modes nu(5)(F(2g)) and nu(3)(F(1u)) leading to the identification of the main vibronic parameters. For the first time, an effective rovibronic Hamiltonian as well as the effective transition moment operators (dipole moment and polarizability) for rovibronic transitions have been studied qualitatively thanks to the tensorial algebra properties. Copyright 2000 Academic Press.
RESUMO
The modulatory effect of heparin and dextran sulfate 500,000 (sulfated polysaccharides) was studied on ATPDase and 5'-nucleotidase activities. These enzymes participate in the degradation of ATP and adenosine production at the synaptic cleft level. Nucleotide hydrolysis was inhibited by heparin and dextran sulfate 500,000. For ADP, the inhibition was more evident at low cation concentrations (0.15 mM Ca2+ or Mg2+), reaching a maximum of 75%. For ATP, the inhibitory effect was less prominent and independent of divalent cation concentration, reaching a maximum of 25%. For AMP, the inhibition observed was similar with either relatively high (1 mM) or with low Mg2+ concentrations tested (0.1 mM) and reached a maximum of 35%. K+ did not change the inhibitory potency of sulfated polysaccharide suggesting that its effects were not exclusively related to charge interaction. These results suggest that heparin and possibly other naturally occurring sulfated polysaccharides may have a potential role as modulator of extracellular nucleotide hydrolysis in the synaptic cleft region.