Geometry optimization at the B3LYP/6-31＋＋G＊ level of theory has been undertaken on clusters containing L-Met （L-methionine） or L-Cys （L-cysteine） surrounded by eight water molecules. The comparison of the struc...Geometry optimization at the B3LYP/6-31＋＋G＊ level of theory has been undertaken on clusters containing L-Met （L-methionine） or L-Cys （L-cysteine） surrounded by eight water molecules. The comparison of the structural parameters of L-Met and L-Cys with X-ray experimental values is in good agreement within 4.8%. This result shows that the privileged positions of water molecules and the possible hydrogen bonding network formed around the backbone of both AAs （amino acids） are adequate. Subsequent calculations of the harmonic vibrational modes followed by a post-processing treatment enable us to assign the vibrational modes of L-Met and L-Cys surrounded explicitly by eight water molecules. The frequencies of the assigned modes are in good agreement with available IR （infra red） and Raman values within 5%.展开更多
An electrochemical quartz crystal impedance system has been applied to monitorgeneration of precipitate and adsorption of the precipitate onto An electrode during electrochmicaloxidation and Fe(CN)_6,3-/Fe(CN),6 4- el...An electrochemical quartz crystal impedance system has been applied to monitorgeneration of precipitate and adsorption of the precipitate onto An electrode during electrochmicaloxidation and Fe(CN)_6,3-/Fe(CN),6 4- electrochemical catalytic oxidation of L-cysteine in phosphateaqueous buffer (pH 7.4). Significant decreases in the resonant frequency and increases in themotional resistance and the static capacitance were found during the precipitate adsorption, and thefrequency shift found in solution was ca. 2 times that in air. Similar responses of quartz crystalimpedance and a white precipitate were obtained during redox titration of L-cysteine solutionusing K_3Fe(CN)_6 solution. FT-IR analysis indicated that the white precipitate is cystine. Theelectrode collection efficiency of the electrogenerated cystine was estimated.展开更多
文摘Geometry optimization at the B3LYP/6-31＋＋G＊ level of theory has been undertaken on clusters containing L-Met （L-methionine） or L-Cys （L-cysteine） surrounded by eight water molecules. The comparison of the structural parameters of L-Met and L-Cys with X-ray experimental values is in good agreement within 4.8%. This result shows that the privileged positions of water molecules and the possible hydrogen bonding network formed around the backbone of both AAs （amino acids） are adequate. Subsequent calculations of the harmonic vibrational modes followed by a post-processing treatment enable us to assign the vibrational modes of L-Met and L-Cys surrounded explicitly by eight water molecules. The frequencies of the assigned modes are in good agreement with available IR （infra red） and Raman values within 5%.
文摘An electrochemical quartz crystal impedance system has been applied to monitorgeneration of precipitate and adsorption of the precipitate onto An electrode during electrochmicaloxidation and Fe(CN)_6,3-/Fe(CN),6 4- electrochemical catalytic oxidation of L-cysteine in phosphateaqueous buffer (pH 7.4). Significant decreases in the resonant frequency and increases in themotional resistance and the static capacitance were found during the precipitate adsorption, and thefrequency shift found in solution was ca. 2 times that in air. Similar responses of quartz crystalimpedance and a white precipitate were obtained during redox titration of L-cysteine solutionusing K_3Fe(CN)_6 solution. FT-IR analysis indicated that the white precipitate is cystine. Theelectrode collection efficiency of the electrogenerated cystine was estimated.
