Evidence of Hexa-Coordination CcP Immobilized in Sol-Gel Glass

Abstract

ABSTRACTAbsorption 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 KN3were allowed to diffuse through the porous glass, to react or to complex with the encapsulated CcP in sol-gel glass. The results show that H2O2and 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.