SPECTROSCOPIC CHARACTERIZATION OF NATIVE AND CO(II)-SUBSTITUTED ZUCCHINI MAVICYANIN

Mavicyanin from zucchini peelings has been characterized by electronic absorption, circular dichroism (CD), magnetic circular dichroism (MCD ), resonance Raman (RR), and electron paramagnetic resonance (EPR) spe ctra. The electronic absorption, CD, MCD, and EPR spectra are apprecia bly similar to those of stellacyanin from lacquer, in which the tetrah edral Cu center has a donor set composed of four amino acid residues [ 2 histidine (His), cysteine (Cys), and glutamine (Gln)]. Under neutral conditions, mavicyanin and stellacyanin show intense blue bands at 59 9 and 604 nm, respectively. However, the RR spectrum of mavicyanin bet ween 300 and 450 cm(-1), which is believed to originate from the predo minant Cu-S stretching vibration, is remarkably different from that of stellacyanin. This might be due to a slight distortion of the tetrahe dral Cu(II) center toward tetragonal geometry in mavicyanin. Moreover, the d-d transition bands of Co(II)-substituted mavicyanin are slightl y blue-shifted compared with those of Co(II)-substituted stellacyanin. This finding also suggests a difference in distortion between these t etrahedral Co(II) centers in spite of the same donor sets.