Vibrational spectroscopy and structural properties of model compounds of photosynthetic reaction center and cytochrome oxidase

The photosynthetic reaction center is a protein complex that converts captured solar energy into electrical and chemical energy in the first steps of photosynthesis. In order to assess the effects of structural and electronic properties on its initial charge separation process, different model compounds were synthesized. In this work, the photoinducted charge separated state of a covalently linked magnesium porphyrin and free base porphyrin heterodimer complex (Mg-H{dollar}sb2{dollar}) is investigated by picosecond time-resolved, two-color, pump-probe resonance Raman spectroscopy. The charge separated state is detected within 30 picoseconds of laser excitation; recombination occurs within 500 picoseconds. The time scales of the charge transfer and recombination processes observed by Raman are consistent with those measured earlier by optical methods. In the charge separated state of the Mg-H{dollar}sb2{dollar} diporphyrin complex, vibrational mode correlations showed that the magnesium porphyrin cation half of the dimer is in its {dollar}sp2{dollar}A{dollar}sb{lcub}rm lu{rcub}{dollar} electronic state. The free base porphyrin anion half of the charge transfer state has vibrational characteristics that are interpreted in terms of data available on the free base octaethylporphyrin anion.; In previous work of this lab, time-resolved vibrational spectroscopy has been used to investigate the reduction of dioxygen by mitochondrial enzyme, cytochrome oxidase. A series of intermediates were detected and assigned to oxy (Fe{dollar}sp{lcub}2+{rcub}{dollar}-O{dollar}sb2{dollar}), peroxy (Fe{dollar}sp{lcub}3+{rcub}{dollar}-O{dollar}sp-{dollar}-O{dollar}sp-{dollar}(H)) and ferryl (Fe{dollar}sp{lcub}4+{rcub}{dollar}=O) species. In this work, (1) semi-empirical calculation has been performed on the peroxy species to evaluate the effect of electron transfer on the bond cleavage and bond formation. The Fe{dollar}sp{lcub}3+{rcub}{dollar}-O{dollar}sp-{dollar}-O{dollar}sp-{dollar}(H) bonding interaction and excited state transition energies are calculated. Their impacts on electronic structure and conformation are compared to experimental results. (2) the {dollar}mu{dollar}-oxo compounds have been widely suggested existing in different enzyme catalytic cycles which included the cytochrome c oxidase. A series of synthesized porphyrin based {dollar}mu{dollar}-oxo complexes (i.e., Fe-O-Fe and Fe-O-Cu) have been characterized by resonance Raman and other analytical techniques. Their structural implications on enzyme catalytic cycle are discussed.; A particle in a one-dimensional box is a classic quantum theory problem. However, it has been discussed mostly in the position space and its momentum distributions is misdescribed or incompleted in many textbooks. In this work, we present a simplified and explicit expression of a free particle in momentum space.