Chromophores pyridine-77-oxide

Because calixarenes have rather low molar absorption coefficients, more efficient chromophores were attached to calixarene moieties in order to obtain strongly absorbing ligands for Eu3+ and Tb3+ com-plexation. Complexes of ligand 61, which contained four pyridine-N-oxide... 

Type I substrates such as hexobarbital, ethylmorphine and testosterone which cause loss of absorbance at 420nm with a concomitant increase at 385nm, and Type II substrates such as aniline, pyridine and acetanilide which cause an increase in absorbance at 430nm and a decrease at 400nm. Such alterations in the heme chromophore reflect interaction at or near the active site of the enzyme. Type II substrates have nonbonding electron pairs which are thought to interact with the heme iron. Three types of EPR spectra have been seen for oxidized cytochrome P-450, two low spin forms and one high spin form. One of the low spin forms is associated with substrate-free oxidized P-450, while the other is observed... 

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