Characterization for didodecyldimethylammonium bromide liquid crystal filmentrapping catalase with enhanced direct electron transfer rate

Direct electrochemistry for catalase (CAT) embedded in the liquid crystal f ilm of didodecyldimethylammonium bromide (DDAB) was investigated at pyrolyt ic graphite (PG) electrode by voltammetric methods. The reduction reaction involved the redox couple in CAT, i.e. Fe-III/Fe-II couple. The electron tr ansfer between the incorporated CAT and PG electrode was found to be greatl y enhanced by DDAB. The heterogeneous electron transfer rate constant k(s) was fitted as 3.0 +/- 0.4 s(-1) using the nonlinear regression analysis of the square wave voltammograms at a series of pulse heights. The pH dependen ce of the formal potential for CAT in DDAB film was 57 mV/pH, which suggest ed one-proton-transfer together with a one-electron reaction. Visible absor ption and reflectance-absorbance infrared (RAIR) spectra inferred the simil ar heme environment of CAT in DDAB film to its native status. Circular dich roism (CD) results indicated DDAB affected slightly on the second structure of CAT. (C) 2001 Elsevier Science B.V. All rights reserved.