Phosphorescence/microwave double-resonance spectra of tryptophan perturbed by methylmercury(II).

AUTOR(ES)

Davis, J M

RESUMO

Amplitude-modulated phosphorescence/microwave double-resonance (AM-PMDR) spectra are reported for complexes of methylmercury(II) cation, designated CH3Hg(II), with tryptophan and glyceraldehyde-3-phosphate dehydrogenase (GPDHase; from rabbit muscle). Wavelength shifts are observed in the AM-PMDR spectra of CH3Hg(II)-tryptophan, which are obtained by microwave pumping in distinct zero-field D + E magnetic resonance transitions, demonstrating that AM-PMDR can be used to display selectively the phosphorescence spectra of structurally distinct complexes with different zero-field splittings. The AM-PMDR spectra accurately represent the phosphorescence of CH3Hg(II)-tryptophan. Binding of CH3Hg(II) to a cysteine site of GDPHase perturbs the luminescence of one of the two optically resolved tryptophan. The AM-PMDR spectrum of the perturbed tryptophan is obtained by microwave pumping of the D + E magnetic resonance signal, which can be observed optically only in the presence of a heavy atom perturbation. The resulting spectrum is broadened and shifted to the blue relative to the corresponding tryptophan phosphorescence spectrum of the uncomplexed enzyme. Comparison of the AM-PMDR spectra of CH3Hg(II)-tryptophan and CH3Hg(II)-GPDHase suggests that there are differences in the mechanisms of heavy atom perturbation in these complexes.

Documentos Relacionados

• Homonuclear 1H double-resonance difference spectroscopy of the rat brain in vivo.
• Methylmercury(II) binding to single-stranded and duplex DNA: complexes formed are distinguishable by optical detection of magnetic resonance spectroscopy.
• Long-range electron exchange measured in proteins by quenching of tryptophan phosphorescence
• Long-range electron exchange measured in proteins by quenching of tryptophan phosphorescence.
• Glycerol effects on protein flexibility: a tryptophan phosphorescence study.