Controllable electrocatalytic activity of heme peptide in a phase transition gel

A phase transition gel based on N-isopropylacrylamide was coated on the ele ctrode surface, and heme peptide as a peroxidase model compound was covalen tly entrapped in the gel. Apparent catalytic activity of the gel for H2O2 e lectroreduction was controlled by swelling (less than or equal to 30 degree s C) and shrinking (greater than or equal to 40 degrees C) the gel; the shr unken gel exhibited higher apparent activity. Formation of the mu-oxo dimer , or oligomers of heme peptide in the swollen gel and the dissociation in t he shrunken gel due to low mobility of heme peptide molecules and steric hi ndrance, may be responsible for the activity changes. As a result of the co mparison with a similar gel containing hemin in place of the heme peptide, it was found that hydrophilicity or hydrophobicity of the active site may a ffect critically the temperature-dependence of the catalytic activity. (C) 2000 The Electrochemical Society. S1099-0062(00)01-013-0. All rights reserv ed.