We have observed detailed and informative resonance Raman spectra from the heme proteins cytochrome P450 and cytochrome c using near ultraviolet laser excitation. We propose to extend our measurements into the visible using our tunable dye laser and further into the ultraviolet using harmonic generation and optical multichannel analyzer (OMA) detection. We plan to specifically focus on Raman spectral studies of important catalytic intermediate states such as the reduced and oxygenated P450 complexes in order to help deduce mechanisms involved in oxygen binding and cleavage in this important class of metabolic enzymes. The long term objective is to use resonance Raman scattering to gain new information about the active site structure and function of cytochrome P450 and other heme proteins and to achieve a better understanding of metalloporphyrin optical absorption spectra. Photosensitive intermediate states will be studied using OMA detection and our dual arm Raman difference spectrometer will be utilized in a variety of experiments involving cryogenic temperatures, isotopic labels, pH and pressure perturbations, etc. The theoretical implications of 3-body normal mode oscillator models will be further pursued and the """"""""transform"""""""" based theories relating absorption and Raman excitation profile measurements will be applied to heme protein systems such as cytochrome c, hemoglobin and cytochrome P450. Fluorescence excitation profile measurements of heme systems will be made using our newly developed technique for absolute quantum yield determination. Photoacoustic spectroscopy will be used to aid in our understanding of these fluoresecence experiments and the accompanying rapid nonradiative relaxation channels present in heme protein systems.

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National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
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Metallobiochemistry Study Section (BMT)
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Northeastern University
Schools of Arts and Sciences
United States
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Karunakaran, Venugopal; Sun, Yuhan; Benabbas, Abdelkrim et al. (2014) Investigations of the low frequency modes of ferric cytochrome c using vibrational coherence spectroscopy. J Phys Chem B 118:6062-70
Sun, Yuhan; Zeng, Weiqiao; Benabbas, Abdelkrim et al. (2013) Investigations of heme ligation and ligand switching in cytochromes p450 and p420. Biochemistry 52:5941-51
Zeng, Weiqiao; Sun, Yuhan; Benabbas, Abdelkrim et al. (2013) Investigations of ferric heme cyanide photodissociation in myoglobin and horseradish peroxidase. J Phys Chem B 117:4042-9
Sun, Yuhan; Karunakaran, Venugopal; Champion, Paul M (2013) Investigations of the low-frequency spectral density of cytochrome c upon equilibrium unfolding. J Phys Chem B 117:9615-25
Benabbas, Abdelkrim; Karunakaran, Venugopal; Youn, Hwan et al. (2012) Effect of DNA binding on geminate CO recombination kinetics in CO-sensing transcription factor CooA. J Biol Chem 287:21729-40
Barabanschikov, Alexander; Demidov, Alexander; Kubo, Minoru et al. (2011) Spectroscopic identification of reactive porphyrin motions. J Chem Phys 135:015101
Karunakaran, Venugopal; Benabbas, Abdelkrim; Youn, Hwan et al. (2011) Vibrational coherence spectroscopy of the heme domain in the CO-sensing transcriptional activator CooA. J Am Chem Soc 133:18816-27
Karunakaran, Venugopal; Denisov, Ilia; Sligar, Stephen G et al. (2011) Investigation of the low frequency dynamics of heme proteins: native and mutant cytochrome P450(cam) and redox partner complexes. J Phys Chem B 115:5665-77
Karunakaran, Venugopal; Benabbas, Abdelkrim; Sun, Yuhan et al. (2010) Investigations of low-frequency vibrational dynamics and ligand binding kinetics of cystathionine beta-synthase. J Phys Chem B 114:3294-306
Benabbas, Abdelkrim; Ye, Xiong; Kubo, Minoru et al. (2010) Ultrafast dynamics of diatomic ligand binding to nitrophorin 4. J Am Chem Soc 132:2811-20

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