Core expansion and electronic structure of the porphyrin in the neutral pH form of copper cytochrome c

Abstract

for model 4-, 5-, and 6-coordinate copper porphyrins show considerable destabilization of the a2u orbital caused by addition of a ir-donating axial ligand. Thus, the calculations support previous interpretations of spectral changes based on addition of an axial fifth ligand in the copper-modified heme proteins and copper porphyrins in coordinating solvents. The

Intermolecular interaction of photoexcited Cu(TMpy-P4) with water studied by transient resonance Raman and picosecond absorption spectroscopies

“…According to this study, there is an electronic state whose energy is located below that of the Q band, which is mostly d(z 2) ~ d(x 2 -y2) but with appreciable CT a2u('rr)~ d(x 2 _y2) character. Thus, although previous calculations [2,3] stated that only the excited CT state can be sufficiently low in energy for 5-coordinate CuP and participates in excitation relaxation processes, this recent study [17] showed that the excited (d, d) state likely plays an important role in excitation deactivation, a conclusion which is consistent with the experimental data of our current and previous [4][5][6][7][8] studies of CuP.…”

“…As predicted by theoretical calculations [2,3], such an axial ligation of CuP results in a considerable energy decrease of both the intramolecular chargetransfer (CT) [a2u('rr), d(x 2-y2)] and the ligandfield [d(z2), d(x:-y2)] states. It is the intramolecular CT state of CuP which is generally thought to be responsible for the efficient radiationless excitation deactivation, although this state was not reliably detected spectroscopically, presumably because of its short lifetime [2,3,11,12].…”

“…It is the intramolecular CT state of CuP which is generally thought to be responsible for the efficient radiationless excitation deactivation, although this state was not reliably detected spectroscopically, presumably because of its short lifetime [2,3,11,12]. Thus it is assumed here that the major part of ligated Cu(TMpy-P4) molecules decays rapidly to the ground state via the CT pathway.…”

“…In particular, a vacancy in the upper d(x2-y 2) orbital results in a bigger affinity of excited CuP for nitrogen (N)-and oxygen (O)-containing molecules from the environment, whose con- ' Corresponding author. sequence is a possible reversible binding of these molecules to the central copper ion as a fifth axial ligand [2][3][4][5][6][7][8][9][10]. It has recently been reported that the excited triplet (~, "rr *) state (T I) of the water-soluble cationic Cu(II) derivative of 5,10,15,20-tetrakis[4-N-methylpyridyl]porphyrin (Cu(TMpy-P4)) has a short lifetime of ca.…”

Resonance Raman spectroscopic studies in copper reconstituted and hybrid hemoglobins: Probe into subunit heterogeneity

“…18 The Raman core size 19,20 and oxidation state marker bands 20 -23 were found to be good indicators of the electronic state of the central porphyrin core resulting from changes in the state of ligation of the metal. 24,25 We used RR spectroscopy to investigate the metal ion coordination of Cu(II) and Ni(II) ions in some of the Cu and Ni containing heme proteins and thereby correlate the quaternary structural changes associated with different heme environments to the structural heterogeneity within the subunits.…”