The electrochemistry and electrocatalysis of a number of heme proteins entrapped in agarose hydrogel films in the room-temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]) have been investigated. UV-vis and FTIR spectroscopy show that the heme proteins retain their native structure in agarose film. The uniform distribution of hemoglobin in agarose-dimethylformamide film was demonstrated by atomic force microscopy. Cyclic voltammetry shows that direct electron transfer between the heme proteins and glassy carbon electrode is quasi-reversible in [bmim][PF(6)]. The redox potentials for hemoglobin, myoglobin, horseradish peroxidase, cytochrome c, and catalase were found to be more negative than those in aqueous solution. The charge-transfer coefficient and the apparent electron-transfer rate constant for these heme proteins in [bmim][PF(6)] were calculated from the peak-to-peak separation as a function of scan rate. The heme proteins catalyze the electroreduction of trichloroacetic acid and tert-butyl hydroperoxide in [bmim][PF(6)]. The kinetic parameter I(max) (maximum current at saturation concentration of substrate) and the apparent K(m) (Michaelis-Menten constant) for the electrocatalytic reactions were evaluated.

When illuminated by near-UV light, titanium dioxide (TiO2) exhibits excellent bactericidal activity. However, there exist some different mechanisms for cell killing via photocatalysis. In the present study, the photocatalytically bactericidal mechanism of TiO2 thin films was investigated by atomic force microscopy (AFM) in conjugation with some other techniques. The decomposition process of the cell wall and the cell membrane was directly observed by AFM for the first time. The resultant change in cell permeability was confirmed by potassium ion (K+) leakage. Quantum dots (QDs) were designed originally as a probe to examine the cell permeability for macromolecules. The corresponding bactericidal activity of TiO2 thin films was examined by cell viability assay. These results suggested that the cell death was caused by the decomposition of the cell wall and the cell membrane and the resultant leakage of intracellular molecules.

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