FT-Raman, FT-IR and normal-mode analysis of carcinogenic polycyclic aromatic hydrocarbons. Part I - a density functional theory study of benzo(a)pyrene (BaP) and benzo(e)pyrene (BeP)
Hp. Chiang et al., FT-Raman, FT-IR and normal-mode analysis of carcinogenic polycyclic aromatic hydrocarbons. Part I - a density functional theory study of benzo(a)pyrene (BaP) and benzo(e)pyrene (BeP), J RAMAN SP, 32(1), 2001, pp. 45-51
In the mechanistic study of the oxygenation of polycyclic aromatic hydrocar
bons (PAHs) by mixed-function oxidase, we employed hemoglobin (Hb) as a mod
el compound for cytochrome P450. We found that the relative intensities of
several Raman peaks of benzo(a)pyrene (BaP) and benzo(e)pyrene (BeP) in the
region between 600 and 1600 cm(-1) are significantly enhanced by the oxyge
nated Hb but not by the deoxygenated Hb. This seems to indicate that these
affected vibrations could be the modes involved in PAH epoxidation by the h
eme-bound oxygen. Density functional theoretical calculations were carried
out using a commercially available software package. The DN** basis set app
ears to give the most satisfactory results. The difference in wave numbers
between observed and calculated wave numbers is estimated to be <20 cm(-1).
Peak assignment through animation shows that all these heme-bound oxygen-a
ffected modes are in-plane vibrations. This seems to indicate that BaP mole
cules, in forming the activated complexes, are more likely vibrating in-pla
ne than out-of-plane, In other words, BaP molecules may diffuse out of the
heme pocket without interaction if their vibrations do not enhance orbital
overlapping with the heme-bound oxygen molecules. Copyright (C) 2001 John W
iley & Sons, Ltd.