TY - JOUR
T1 - Effects of a thiolate axial ligand on the π→π* electronic states of oxoferryl porphyrins
T2 - A study of the optical and resonance Raman spectra of compounds I and II of chloroperoxidase
AU - Egawa, Tsuyoshi
AU - Proshlyakov, Denis A.
AU - Miki, Hideho
AU - Makino, Ryu
AU - Ogura, Takashi
AU - Kitagawa, Teizo
AU - Ishimura, Yuzuru
PY - 2001/9/17
Y1 - 2001/9/17
N2 - Optical absorption and resonance Raman spectra have been investigated for enzymatic intermediates, compounds I and II, of chloroperoxidase (CPO) which contains a thiolate-ligated iron porphyrin. Compound I of CPO (CPO-I), an oxoferryl porphyrin π cation radical, gave an apparently asymmetric single-peaked Soret band at 367 nm, for which band fitting analyses revealed the presence of two transition bands around 365 and 415 nm. Compound II of CPO (CPO-II), an oxoferryl neutral porphyrin, gave a split Soret spectrum with two bands (blue and red Soret bands) at 373 and 436 nm. Thus both CPO-I and CPO-II can be categorized as hyperporphyrins. The maximum extinction coefficients (εb and εr) and energies (Eb and Er) of the blue and red Soret bands of CPO-II were found to fall on an εb/εr versus Eb-Er correlation line derived from data reported for six-coordinate ferrous derivatives of cytochrome P450 and CPO. Corresponding data for CPO-I did not fall on the correlation line. Resonance enhancement of the FeIV=O stretching (νFeO) Raman band was found for CPO-I when Raman scattering was excited at wavelengths within both transition bands around 365 and 415 nm, while the νFeO Raman band was not identified for CPO-II at any of the excitation wavelengths examined here. These findings suggest that the thiolate axial ligand causes Soret band splitting of CPO-II through configuration interaction between the sulfur→porphyrin eg* charge transfer and porphyrin a1u,a2u→eg* transitions, while the FeO portion is important in determining the shape of the Soret band of CPO-I.
AB - Optical absorption and resonance Raman spectra have been investigated for enzymatic intermediates, compounds I and II, of chloroperoxidase (CPO) which contains a thiolate-ligated iron porphyrin. Compound I of CPO (CPO-I), an oxoferryl porphyrin π cation radical, gave an apparently asymmetric single-peaked Soret band at 367 nm, for which band fitting analyses revealed the presence of two transition bands around 365 and 415 nm. Compound II of CPO (CPO-II), an oxoferryl neutral porphyrin, gave a split Soret spectrum with two bands (blue and red Soret bands) at 373 and 436 nm. Thus both CPO-I and CPO-II can be categorized as hyperporphyrins. The maximum extinction coefficients (εb and εr) and energies (Eb and Er) of the blue and red Soret bands of CPO-II were found to fall on an εb/εr versus Eb-Er correlation line derived from data reported for six-coordinate ferrous derivatives of cytochrome P450 and CPO. Corresponding data for CPO-I did not fall on the correlation line. Resonance enhancement of the FeIV=O stretching (νFeO) Raman band was found for CPO-I when Raman scattering was excited at wavelengths within both transition bands around 365 and 415 nm, while the νFeO Raman band was not identified for CPO-II at any of the excitation wavelengths examined here. These findings suggest that the thiolate axial ligand causes Soret band splitting of CPO-II through configuration interaction between the sulfur→porphyrin eg* charge transfer and porphyrin a1u,a2u→eg* transitions, while the FeO portion is important in determining the shape of the Soret band of CPO-I.
KW - Oxoferryl porphyrin
KW - Resonance Raman spectroscopy
UR - http://www.scopus.com/inward/record.url?scp=0034845631&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0034845631&partnerID=8YFLogxK
U2 - 10.1007/s007750000181
DO - 10.1007/s007750000181
M3 - Article
C2 - 11191222
AN - SCOPUS:0034845631
VL - 6
SP - 46
EP - 54
JO - Journal of Biological Inorganic Chemistry
JF - Journal of Biological Inorganic Chemistry
SN - 0949-8257
IS - 1
ER -