Modulation of the flavin-protein interactions in NADH peroxidase and mercuric ion reductase: a resonance Raman study.

NADH peroxidase (Npx) and mercuric ion reductase (MerA) are flavoproteins belonging to the pyridine nucleotide:disulfide oxidoreductases (PNDO) and catalyzing the reduction of toxic substrates, i.e., hydrogen peroxide and mercuric ion, respectively.

Redox effects on the coordination geometry and heme conformation of bis(N-methylimidazole) complexes of superstructured Fe-porphyrins. A spectroscopic study.

Electronic absorption, electron paramagnetic resonance (EPR), and Soret-excited resonance Raman (RR) spectra are reported for bis(N-alkylimidazole) complexes of various iron(III)-"basket-handle" (Fe(III)BHP(+)) and "picket-fence" (Fe(III)PFP(+)) porphyrins in methylene chloride. The Fe(III)BHP(+) derivatives consist of four cross-trans (CT) and two adjacent-cis (AC) -linked in which the composition and the length of the handles are variable (CT Fe(III)[(C(11)Im)(2)(+)], CT and AC Fe(III)[((C(4))(2)phi)(2)](+), CT Fe(III)[((C(3))(2)phi)(C(12))](+), CT and AC Fe(III)[((C(3))(2)phi)(2)](+)). The meso-alphaalpha betabeta and meso-alphabeta alphabeta atropisomers of Fe(III)-tetrakis(o-pivalamidophenyl)-porphyrins represents the Fe(III)PFP(+) derivatives (Fe(III)alphaalpha betabeta-T(piv)PP(+) and Fe(III)alphabeta alphabeta-T(piv)PP(+), respectively).

Interaction of glutathione reductase with heavy metal: the binding of Hg(II) or Cd(II) to the reduced enzyme affects both the redox dithiol pair and the flavin.

To determine the inhibition mechanism of yeast glutathione reductase (GR) by heavy metal, we have compared the electronic absorption and resonance Raman (RR) spectra of the enzyme in its oxidized (Eox) and two-electron reduced (EH2) forms, in the absence and the presence of Hg(II) or Cd(II). The spectral data clearly show a redox dependence of the metal binding. The metal ions do not affect the absorption and RR spectra of Eox.

Nonplanar distortions of bis-base low-spin iron(II)-porphyrinates: absorption and resonance Raman investigations of cross-trans-linked iron(II)-basket-handle porphyrin complexes.

Electronic absorption and Soret-excited resonance Raman (RR) spectra are reported for bis-N-alkylimidazole and bis-pyridine complexes of various cross-trans-linked iron(II)-"basket-handle" porphyrins (Fe(II)-BHP) in methylene chloride. These compounds enable us to characterize the spectroscopic properties of ruffled six-coordinated low-spin Fe(II)-porphyrin complexes. The visible absorption spectra show that the Q and B bands are progressively red-shifted when the handles are shortened and/or when the steric hindrance of the axial ligands is increased.

Absorption and resonance Raman investigations of ligand rotation and nonplanar heme distortion in bis-base low-spin iron(II)-tetrakis(o-pivalamidophenyl)porphyrin complexes.

The absorption and resonance Raman (RR) spectra of the bis-N-methylimidazole, bis-1,5-dicyclohexylimidazole, and bis-pyridine complexes of the meso-alphaalphabetabeta and meso-alphabetaalphabeta atropisomers of Fe(II)-tetrakis(o-pivalamidophenyl)porphyrins (Fe(II)TpivPP) were obtained in methylene chloride. The different spatial arrangements of the o-pivalamide pickets in these two Fe(II)TpivPP compounds are expected to control the absolute and relative positions of the axial ligand rings with respect to the Fe-N(pyrrole) bonds. In particular, the spectroscopic data obtained for the bis-N-methylimidazole and bis-dicyclohexylimidazole complexes of the Fe(II)[alphabetaalphabeta-TpivPP] derivative showed the most important differences.

Electrostatic control of the isoalloxazine environment in the two-electron reduced states of yeast glutathione reductase.

The resonance Raman spectra of the oxidized and two-electron reduced forms of yeast glutathione reductase are reported. The spectra of the oxidized enzyme indicate a low electron density for the isoalloxazine ring. As far as the two-electron reduced species are concerned, the spectral comparison of the NADPH-reduced enzyme with the glutathione- or dithiothreitol-reduced enzyme shows significant frequency differences for the flavin bands II, III, and VII.