Substrate specificity of the carbon monoxide-dependent cytochrome P-450 kinetics

Solvents effect on the absorption and fluorescence spectra of 7-diethylamino-3-thenoylcoumarin: evaluation and correlation between solvatochromism and solvent polarity parameters

Effect of solvents of varying polarities on absorption and fluorescence spectra and dipole moment of laser dye: 7-diethylamino-3-thenoylcoumarin (DETC) has been investigated. A small band shift is obtained in the absorption spectra compared to emission spectra. The spectral shifts were correlated with Catalan's parameters using linear solvation energy relationship. It reveals that non-specific interaction measured by solvent polarity has more influence on absorption and solvent dipolarity contribution is significant in case of fluorescence. A bathochromic shift observed in absorption and emission spectra with increasing solvent polarity, which implied that the transition involved is π→π(∗). The solvatochromic correlations were used to estimate the excited state dipole moment using experimentally determined ground state dipole moment. The observed single-state excited state dipole moment is found to be greater than the ground state.

Influence of solvent and substituent on excited state characteristics of laser grade coumarin dyes

Absorption and fluorescence emission of 4 and 7 substituted coumarins viz. C 440, C 490, C 485 and C 311 have been studied in various polar and non-polar organic solvents. These coumarin dyes are substituted with alkyl, amine and fluorine groups at 4- and 7-positions. They give different absorption and emission spectra in different solvents. The study leads to a possible assignment of energy level scheme for such coumarins including the effect on ground state and excited state dipole moments due to substitutions. Excited state dipole moments of these dyes are calculated by solvetochromic data experimentally and theoretically these are calculated by PM 3 method. The dipole moments in excited state, for all molecules investigated here, are higher than the corresponding values in the ground state. The increase in dipole moment has been explained in terms of the nature of excited state and resonance structure.

Selective inhibition of major drug metabolizing cytochrome P450 isozymes in human liver microsomes by carbon monoxide

The selectivity of carbon monoxide binding to specific human cytochrome P450 isozymes was investigated by studying its inhibition of prototype reactions for 3 major drug metabolizing P450s in liver microsomes: dextromethorphan O-demethylation and (+)-bufuralol 1'-hydroxylation (P450DB1, CYP2D6), diclofenac 4'-hydroxylation (P450TB, CYP2C subfamily), and midazolam 1'-hydroxylation (P450NF, CYP3A subfamily). The affinity of carbon monoxide is different for each P450 isozyme. Warburg partition coefficients were 0.35, 1.1 and 3.9 microM for P450DB1, P450TB and P450NF, respectively. Differential inhibition by carbon monoxide may be a useful tool to identify specific human cytochrome P450 isozymes in the early screening of drug biotransformation catalysts. Further studies involving other P450 isozymes and substrates should extend our understanding of the phenomena and their implications.