Resonance Raman spectra of protohemin and protohemin‐imidazole complex

Abstract

Resonance Raman spectra of aqueous solutions of protohemin and its complex with imidazole have been obtained using several exciting lines from Ar+ and HeCd lasers. The effects of different axial ligands to iron in hemin are reflected in the resonance Raman spectra of their respective complexes. Within experimental limits, hemin does not show any anomalously polarized bands (~i > 2) while its complex with imidazole shows several such bands when excitation is in the n and B absorption regions. When excitation is in the Soret region, a polarized band N 1500 cm-l appears in the spectra of hemin-imidazole complex and heme proteins. It is proposed as a spin state marker as well as to characterize the position of the iron ion relative to the porphyrin plane.Excitation profiles for some of the bands of hemin confirm the assigment of the LY band near 5300 A in the unresolved visible absorption spectrum.

Raman spectra of platinum hematoporphyrin complexes

“…The present results agree also with the prediction of Felton et al [26] concerning the lines at 1588 and 1555 cm-'. We have found a systematic frequency increase in the 1500 cm-' region due to the planarity of the molecules (See Table I) similar to that reported by Verma and Bernstein [17].…”

High Performance Reduction of H2O2 with an Electron Transport Decaheme Cytochrome on a Porous ITO Electrode

“…Confocal RR spectroscopy was used to obtain structural insights into the protein integrity and heme environment of MtrC in solution and adsorbed onto ITO as well as in the presence of H 2 O 2 . Excitation at 413 nm afforded intense RR spectra in the region from 1300 to 1700 cm –1 , dominated by the heme marker modes ν 4 , ν 3 , ν 2 , and ν 10 , indicating the heme’s oxidation, coordination, and spin state . Potentiometric RR titration from +0.2 to −0.55 V shows that the vast majority of the heme groups are redox active and reduced upon applying a cathodic potential, demonstrated by the appearance of marker bands of the reduced heme species (Figure ).…”

“…Excitation at 413 nm afforded intense RR spectra in the region from 1300 to 1700 cm –1 , dominated by the heme marker modes ν 4 , ν 3 , ν 2 , and ν 10 , indicating the heme’s oxidation, coordination, and spin state. 22 Potentiometric RR titration from +0.2 to −0.55 V shows that the vast majority of the heme groups are redox active and reduced upon applying a cathodic potential, demonstrated by the appearance of marker bands of the reduced heme species ( Figure 4 ). Comparison of MtrC RR spectra in solution and on ITO shows no significant spectral differences ( Figure S9b ), which supports that the heme environment is not distorted upon adsorption of MtrC onto ITO ( Figure 4 b).…”

Resonance Raman scattering from metalloporphyrins. Metal and ligand dependence of the vibrational frequencies of octaethylporphyrins

“…The Raman spectrum of a protein-free ferrous heme was measured first in the present study although the ferric one was reported previously. 15 The Raman bands at 1359, 1492, 1537, and 1617 cm""1 of Fe2+(PP)(Im)2 show high wavenumber shift to 1374, 1503,1562, and 1638 cm-1 in Fe3+(PP)(Im)2, in good agreement with the corresponding wavenumber shifts (from 2631 1361, 1493, 1538, and 1617 cm""1 to 1375, 1505, 1563, and 1639 cm-1) observed for cytochrome 65. 21 The corresponding wavenumber shifts due to the oxidation of the iron ion for Fe(OEP)(L)2 and Fe(PPME)(L)2 (PPME = protoporphyrin dimethyl ester) are compared with those of Fe-(PP)(Im)2 in Table II.…”