Ranjit Kumble

Modeling the Transient Changesin the Soret-Resonant RamanIntensities of Hemoglobin DuringThe R→ T Transition

We have performed resonance Raman (RR) intensity calculations of the Soret-resonant Raman spectra of Ni and Zn Porphine to investigate observed core size intensity differences in the time-resolved Soret-resonant Raman (RR) spectra of hemoglobin. It was found that the metalloporphine intensities mainly derive from the expansion of the Cα—Cm and Cβ—Cβ bonds in the excited state, and that the observed differences are mainly due to the larger core-sized heme having a decreased Cα—Cm force constant and larger excited state porphyrin ring expansion.

Singlet and Triplet (π, π*) Excited States of Zinc(II) Octaalkylporphyrins: A Time-Resolved Resonance-Raman Study

The excited states of porphyrins and hydroporphyrins act as primary intermediates in processes ranging from biological energy transfer and electron transfer to photocatalysis and photodynamic therapy. We report resonance Raman (RR) spectra of the singlet S1 and triplet T1 excited states of zinc(II) octaethylporphyrin (ZnOEP) and zinc(II) etioporphyrin-I (ZnEtio), using picosecond and nanosecond RR techniques. Picosecond time-resolved resonance Raman experiments were performed using 532 nm photoexcitation pulses and 436 nm probe pulses (both 100 ps, 50 Hz); the experimental apparatus consisted of a mode-locked Nd:YAG laser (Coherent) in combination with a Nd:YAG regenerative amplifier (Continuum) and an H2 cell for stimulated Raman shifting. The apparatus used for nanosecond time-resolved RR experiments has been described previously [1]. Porphyrin samples were prepared in a nitrogen atmosphere at a concentration of 0.5 mM (tetrahydrofuran solvent).