Photo-induced transient responses corresponding to proton release and uptake of bacteriorhodopsin at the electrode/electrolyte interface were investigated for the purpose to clarify the role of charged amino acid residues in the retinal binding pocket. Mutants of bacteriorhodopsin, lacking one or both of the charged amino acid residues Arg-82 and Asp-212 in the pocket, were investigated. pH-dependent photoresponse profiles revealed that proton pumping activity nearly disappears in single mutants R82Q, R82A and D212N while it is well recovered in a double mutant R82Q/D212 N, indicating that a net charge balance created by ion pairs between charged residues is crucial for driving the photocycle and proton transport reaction.
A cetyltrimethylammonium bromide modified carbon paste electrode (CTAB/CPE) was developed. The modification was based on the hydrophobic adsorption of CTAB on the surface of CPE. This electrode exhibited excellent catalytic activity toward the reduction of dioxygen (O2). Compared with the poor signals at bare CPE, O2 had much larger reduction current and more positive peak potential at CTAB /CPE, which may arise from the formation of a positively charged layer of CTAB on the surface of CPE. The effects of some parameters on the O2 reduction were examined, including electrolyte pH, amount of modifier, scan rate and composition of carbon paste. The preparation of this electrode not only produced a new chemically modified carbon paste electrode but also provided a useful sensor for the determination of O2.
The electropolymerization of 5-amino-1,4-dihydroxy-9,10-anthraquinone (5-aminoquinizarine: 5-AQ) in acetonitrile solution containing 0.1 M of tetraethylammonium perchlorate (TEAP) results in the formation of the polymer films, which are adherent on Pt electrodes. FTIR studies indicate that the aromatic amine groups take part in the polymerization process. This polymer film is electroactive in acetonitrile solution containing 0.1 M TEAP, and also has good cycleability more than 50 cycles in the potential range between 0.0 and +1.0 V vs. Ag/AgCl. Scanning the potential between 0.0 and + 1.4 V vs. Ag/AgCl results in the polymer deterioration gradually. In the negative region than 0 V vs. Ag/AgCl the polymer is eliminated from the Pt electrode.
Powders of RuO2•0.5H2O have been successfully characterized for their electrochemical capacitive performance using a microporous electrode (PME) that does not require the use of binder. The cavity at the tip of the PME was filled with less than 100 ng of RuO2•0.5H2O powder. Cyclic voltammetry; constant current charge-discharge, and electrochemical impedance spectroscopy were carried out in 0.5 M H2SO4 aqueous solution. Capacitances as high as 950 F g-1 are reported for the first time concerning this material. These values are more than 25% larger than these previously reported in the literature for RuO2•0.5H2O characterized by means of composite electrodes.
We have been studied the relation between electronic states, and cycle performances of LiMn2-xMxO4 (M = Mn, Mg, Al, Co, Ni, Zn) as cathode active materials for 4 V class Li secondary battery. The electronic density maps of the LiMn2-xMxO4 (M = Mn, Mg, Al, Co, Ni, Zn) shows the covalent bonding of Mn-O of LiMn2-xMxO4 (M = Mn, Mg, Al, Co, Ni, Zn) is stronger than that of LiMn2O4. On the other hands, we calculated that the net charge of each atom, the bond overlap population of Li-O, Mn-O, M-O, the density of states, and the electron density of LiMn1.75M0.25O4 (M = Mn, Mg, Al, Co, Ni, Zn) using first principles calculation by DV-Xα method. Li ionicity always keeps high and the covalent bonding of Mn-O in the octahedron of each LiMn1.75M0.25O4 is stronger than that of LiMn2O4.
Nitrogen (N) and phosphorus (P) in wastewater should be removed as they cause serious damages on the environment. Biological methods have so far been used to treat wastewater to remove N & P, however they are not prevailing due to their drawbacks such as slow treatment rate and temperature sensitivity. In order to solve these problems, electrolytic methods have drawn our attention because of their higher treatment rate and temperature insensitivity. Here, we adopted a pair of iron electrodes to treat a model wastewater consisting of nitrate and found that iron cathode was able to reduce nitrate to ammonia. N and P removal was further accomplished by combining ammonia oxidation by hypochlorite produced at platinum-iridium anode and phosphorus removal by iron anode.
Rapid detection system for nitrifying bacteria was developed using photon correlation spectroscope (PCS) technique. The method is based on that nitrifying bacterial cells reacted with anti-nitrifying bacteria antibody were able to analyze by PCS technique. When nitrifying bacterial cells were reacted with the antibody beads, the size distribution was shifted to larger range. In contrast, in the reference bacterial cells, the size distribution shows little change. The phenomenon was assumed that since the antibody reacted with nitrifying bacteria selectively, they were aggregated with bacterial cells, and the distribution size increased. Thus, it is possible to discriminate between aimed nitrifying bacteria and other species of bacterial cells using PCS technique. One assay could be completed in 10 min, and the total PCS assay time including sample preparation was within 60 min.