Fran Adar

Resonance Raman spectra of cytochrome oxidase. Evidence for photoreduction by laser photons in resonance with the Soret band

Resonance Raman spectra of cytochrome oxidase solubilized in Tween 20 and sodium cholate, and excited at 413.1 nm have been recorded. Differences in the resonance Raman spectra of the two preparations are minimal indicating that the local environment of the hemes is similar in the two preparations. As in the work of Salmeen, et al. (1973) (Biochem. Biophys. Res. Commun. 52, 1100) the strongest band appears at 1358 cm-1. Some of the other bands differ slightly in their band shapes and frequencies when compared to their spectra; these differences can be accounted for by differences in resonance enhancement of the various bands wnen exciting at 441.6 and 413.1 nm. A study of the region from 1350 to 1380 cm-1 as a function of laser intensity (10--130 mW on sample) indicate that the doublet reported by Salmeen, et al. at 1358 and 1372 cm-1 is a result of photoreduction of the preparations. In samples to which potassium ferricyanide had been added, broad luminescence bands appear at 476 and 641 nm from which it is inferred that catalytic amounts of flavin in the preparations are photoreduced providing reducing equivalents to cytochrome oxidase.

Resonance Raman spectra of the b- And c-type cytochromes of succinate-cytochrome c reductase☆

Abstract 1. Resonance Raman spectra excited by laser photons in resonance with the α and β electronic transitions of the reduced forms of cytochrome b 5 and c were recorded and used as model systems to distinguish the “ b ”- and “ c ”-type Cytochromes of succinate-cytochrome c reductase. 2. The scattering intensity of a particular cytochrome depends on the proximity of the laser excitation to the electronic transition which is involved in the resonance enhancement; thus, exciting at different wavelengths provides a method of selectively investigating one hemoprotein in a mixture of several. 3. The spectra of the reduced succinate-cytochrome c reductase excited at 514.5-nm laser light were due to both c - and b -type Cytochromes in agreement with the position of their respective electronic absorption bands. Spectra excited at 568.2 nm were due mostly to b -type cytochromes because of the proximity of the excitation wavelength to the position of their α absorption bands. 4. The identification of the individual cytochromes is aided by the set of characteristic vibrational bands recorded at each excitation wavelength. 5. A possible explanation of the differences in number of bands and frequency of normal modes, involving the strong interaction between the vinyl side groups and porphyrin ring, is suggested. 6. Comparison of spectra of purified cytochrome b 5 with the b cytochromes of the reductase preparations shows vibrational bands of protoheme in different hemeproteins which are sensitive to the particular protein environment.

Resonance Raman spectra of cytochrome b5 and its mesoheme and deuteroheme modifications

Abstract Resonance Raman spectra of proto-, meso-, and deuterohemes isolated in cytochrome b 5 have been recorded and effects due to sidegroup substituents noted. A one-to-one correspondence can be made between the fundamental Raman bands of mesoheme and deuteroheme, enabling identification of inductive effects on the porphyrin vibrations. (The saturated sidegroups of mesoheme produce Raman spectra very similar to cytochrome c .) Raman spectra of protoheme show extra structure which is produced by a resonance interaction between the vinyl sidegroups and deuteroheme core. Based on the resonance Raman data of protoheme it is possible to say that the red-shift in the absorption bands is due to extension of conjugation from the ring to the sidegroups rather than inductive effects of the sidegroups on the ring molecular orbitals.

Spectral evidence for interactions between membrane-bound hemes: resonance Raman spectra of mitochondrial cytochrome b--c1 complex as a function of redox potential.

Resonance Raman (RR) spectra of many hemeproteins [l-lo] and metalloporphyrins [ 1 l-161 have been reported since the initial analysis of the scattering enhanced by resonance between the laser frequency and porphyrin rr to n* transitions in cytochrome c by Spiro et al. [17]. Later, more detailed descriptions of the scattering phenomenon in both cytochrome c [ 18-201 and other metalloporphyrins [ 15 ,16,2 l] were presented and correlations were made between RR band frequencies and oxidation and spin states of the iron in various hemeproteins [6,22,23]. Moreover, the proposal was made that because of its high resolution capabilities, RR spectra could be exploited as a probe of interactions between hemes in functioning biological membranes [24] . A model study on the ~-0x0 dimer of tetraphenylporphin indicated that this technique was indeed sensitive to heme aggregation. Our initial work on the succinate cytochrome c reductase showed it to be a fruitful system for RR study for a variety of reasons: (1) RR spectra of isolated cytochromes exhibit well-defined marker bands [7] ; (2) The RR quantum yields of ferrous cytochromes are unusually large (lo-‘) [25] ; (3) The spectroscopic characterization of the RR effect in ferrous cytochromes is highly developed [17-191.

Exchange coupling in spinach ferredoxin determined by resonance raman spectroscopy

Summary Resonance Raman spectra have been recorded for spinach ferredoxin at 300°K and 190°K. Bands caused by antiferromagnetic exchange coupling between the irons are seen, confirming the general features of that model for the binuclear iron-sulfur clusters. Values of J red of −74 cm −1 and J ox of −172 ± 16 cm −1 are found. Bands associated with iron-sulfur stretching frequencies at 284, 330, and 395 cm −1 are also seen, and C-H stretching bands at 2840 and 2950 cm −1 have also been noted.

Resonance Raman spectra of cytochromes c557 and c558

Abstract Resonance Raman spectra of cytochromes c 557 and c 558 have been recorded and compared to other low-spin ferrous cytochromes. The data support the chemical evidence that there is one vinyl group on the heme and one thioether linkage to the protein.

Anti-ferromagnetic exchange in beef adrenodoxin as measured by resonance raman spectroscopy

ANTI-FERROMAGNETIC EXCHANGE IN BEEF ADRENODOXIN AS MEASURED BY RESONANCE RAMAN SPECTROSCOPY Fran ADAR, Haywood BLUM, J. S. LEIGH, Jr, Tomoko OHNISHI, John SALERNO Dept. of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104 and Tokuji KIMURA Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA