Cytochrome P-450 difference spectra: effect of chemical structure on type II spectra in mouse hepatic microsomes.

A comprehensive study of the relationship between chemical structure and binding was made with mouse hepatic microsomes. The generally reported type II spectrum (peak 424-435 nm, trough 390-410 nm) is correlated with the presence of a nitrogen atom in which sp 2 or sp 3 nonbonded electrons are "sterically accessible." Structural series showed that as substituents are placed closer to this nitrogen, spectral size is either reduced or eliminated. Other nucleophilic atoms with relatively free steric access may also cause a modified type II binding. i.e. , a bathochromic shift. Data are also presented to show that minor structural changes affect both size and type of spectrum.