Absorption spectra of Cytochrome c Peroxidase (CcP) in phosphate buffer at
pH 6.5 were recorded from 700 to 250 nm. The CcP solution was then
encapsulated in sol-gel derived glass. The absorption spectra of CcP in
xerogels were compared to those in buffer solutions. An increase in
absorptivity at the Soret maximum, a decrease between 360 and 380 nm, and a
spectral shift of the charge-transfer band from 645 to 620 nm was observed
for CcP in gel matrix as compared to those in solution. Those spectral
observations indicate a change in the coordination of the iron porphyrin
ring in CcP from penta-coordinated in solutions to hexa-coordinated in gels.
The oxidant H2O2, reductant
Na2S2O4, and inhibitors NaF and
KN3 were allowed to diffuse through the porous glass, to react
or to complex with the encapsulated CcP in sol-gel glass. The results show
that H2O2 and S2O42- lead to a change of oxidation state from Fe(III) to Fe(IV) and
to Fe(II), respectively. Moreover, F- results in an enhancement
of high-spin CcP, and N3- promotes a spin state change to a
low-spin CcP. For CcP in xerogels, the chemical changes caused by inhibitors
were found to be reversible when washed with deionized water. The possible
applications of CcP immobilized xerogels in chemical and biochemical sensor
technologies are discussed.