Direct monitoring of the electron pool effect of cytochrome<Emphasis Type="Italic"> c</Emphasis><Subscript>3</Subscript> by highly sensitive EQCM measurements

Cytochrome c₃ from Desulfovibrio vulgaris has four hemes per molecule, and a redox change at the hemes alters the conformation of the protein, leading to a redox-dependent change in the interaction of cytochrome c₃ with redox partners (an electron acceptor or an electron donor). The redox-dependent change in this interaction was directly monitored by the high-performance electrochemical quartz crystal microbalance (EQCM) technique that has been improved to give high sensitivity in solution. In this method, cytochrome c₃ molecules in solution associate electrostatically with a viologen-immobilized quartz crystal electrode as a monolayer, and redox of the associating cytochrome c₃ is controlled by the immobilized viologen. This technique makes it possible to measure the access of cytochrome c₃ to the electrode or repulsion from the electrode, and hence interconversion between an electrostatic complex and an electron transfer complex on the cytochrome c₃ and the viologen as a mass change accompanying a potential sweep is monitored. In addition, simultaneous measurement of a mass change and a potential step reveals that the cytochrome c₃ stores electrons when the four hemes are reduced (an electron pool effect), that is, the oxidized cytochrome c₃ facilitates acceptance of electrons from the immobilized viologen molecule, but the reduced cytochrome c₃ donates the accepted electrons to the viologen with difficulty.     

Photoinduced hydrogen evolution with peptide dendrimer-multi-Zn(II)-porphyrin, viologen, and hydrogenase

To construct an artificial photosynthetic system, multi-Zn(II)-mesoporphyrins in peptide dendrimers were equipped as a photosensitizer of photoinduced hydrogen evolution in a four-component system (electron donor, photosensitizer, electron carrier, and catalyst), so that hydrogen was evolved effectively by the dendrimer architecture, for the first time. The hydrogen evolution activity was correlated to the photoreduction ability of viologen by the Zn-porphyrin-peptide dendrimers. Additionally, using positively charged methyl-viologen as an electron carrier, the photoinduced hydrogen evolution function with the positively charged peptide dendrimer was superior to that with the negatively charged peptide dendrimer, despite that the positive dendrimer did not strongly bind the positively charged methyl-viologen with the electrostatic interaction. By contrast, when zwitterionic propylviologen sulfonate was used, photoreduction and hydrogen evolution properties were identical between the positively and the negatively charged dendrimers. These results demonstrated that the dynamic interaction between the positive dendrimer and methyl-viologen was preferable for the photoreduction and hydrogen evolution, and that the three-dimensional assembly of Zn(II)-mesoporphyrins using the peptide dendrimers was effective as a photosensitizer in the artificial photosynthesis.     

Two trehalose-hydrolyzing enzymes from Crenarchaeon Sulfolobus acidocaldarius exhibit distinct activities and affinities toward trehalose

Applied Microbiology and Biotechnology - Two archaeal trehalase-like genes, Saci1250 and Saci1816, belonging to glycoside hydrolase family 15 (GH15) from the acidophilic Crenarchaeon Sulfolobus...     

A Study of the Association between Sleep Habits and Problematic Behaviors in Preschool Children

This preliminary study examined the association between sleep habits and problematic behaviors in healthy preschool children using an internationally standardized method. Two groups of 4–6‐yr‐old healthy Japanese children were recruited. Children in Group A (n=68) met one or more of the following three conditions: they went out from their home with adults after 21∶00 h two or more times a week, they went to bed after 23∶00 h four or more times a week, and they returned home after 21∶00 h three or more times a week, while those in Group B (n=67) met none of these conditions. Sleep‐wake logs and the Child Behavior Checklist (CBCL)/4–18 were completed daily for two weeks. The CBCL consists of questions with 113 items categorized into eight subscale items: (I) Withdrawn, (II) Somatic complaints, (III) Anxious/depressed, (IV) Social problems, (V) Thought problems, (VI) Attention problems, (VII) Delinquent behavior, and (VIII) Aggressive behavior. Internalizing (I+II+III), externalizing (VII+VIII), and total scale scores were also derived. Generally, the higher the score, the greater the likelihood of problematic behaviors in that scale. We compared both the CBCL scores and distribution of the CBCL score‐determined clinical classification of behavior (normal, borderline, and abnormal) between the groups. Correlation coefficients between CBCL scores and each of the seven indices of the studied sleep habits (wake‐up times, bedtimes, nocturnal sleep duration, nap duration, total sleep duration, and range of variation in wake‐up and bedtime) were also assessed. Group A children showed significantly shorter average nocturnal sleep, nap, and total sleep duration, significantly later average bedtimes and wake‐up times, and a significantly greater range of variation in bedtimes and wake‐up times than Group B children. The CBCL score of the total scale was significantly higher in Group A than Group B children. The distribution of the clinical classifications of behavior between the two groups showed no significant differences. Although nocturnal sleep, nap, and total sleep duration did not correlate with total CBCL score, it showed a high positive correlation with wake‐up times, bedtimes, and ranges of variation in both wake‐up and bed times. The distribution of the clinical classification for the total scale showed significant differences between early and late risers, and also between regular and irregular sleepers. The number of children classified as normal for the total scale score was higher in early risers and regular sleepers than in late risers and irregular sleepers. Preschool children of Group A, late risers, late sleepers, irregular risers, and irregular sleepers were likely to show problematic behaviors.     

β-Glucanases in Malt That Form Insoluble Materials

When brewing barley malt extracts were incubated with malt β-glucans, insoluble materials were formed in the reaction mixture. To investigate the cause of this, we studied various factors that may participate in the formation of these materials. The isolated malt β-glucans were similar to barley β-glucans with the β-(l→3) and (1→4)-linkages in a molar ratio of 1:2.38, and the molecular weight was 950,000. Three enzymes were detected and purified from malt by ammonium sulfate precipitation, ion exchange chromatography, gel filtration, and isoelectric focusing. One of these enzymes was β-(1→4)-d-glucanase (I) with a molecular weight of 40,000 and an optimum pH of 5.0. The other enzyme was β-(l→3), (l→4)-d-glucan 4-glucanohydrolase, with a molecular weight of 33,000 and an optimum pH 5.0. The third enzyme was β-(1→4)-d-glucanase (II), with a molecular weight of 49,000 and an optimum pH of 4.5. Among these three β-glucanases, β(1→4)-d-glucanases (I) and (II) had not been identified before in malt, and β-(l→4)-d-glucanase (II) was most stable on heat treatment and formed most of the precipitates in the reaction mixture.     

Volatile and Nonvolatile Maillard Reaction Products between l-Lysine and d-Glucose

The killer toxin produced by the Pichia farinosa KK1 strain was purified by ammonium sulfate precipitation, gel filtration, ion-exchange chromatography and reverse-phase HPLC. The molecular weight of the killer toxin was about 25 kd and its isoelectric point was 6.4. A significant amount of carbohydrate was not detected in the purified killer toxin, suggesting that the toxin is not glycosylated. Its N-terminal amino acid sequence showed no homology with other proteins. The stability and efficacy of the toxin’s killer activity was examined. The toxin completely retained activity at pH 2.5 ~ 4.0 and 5°C, but lost activity at higher temperatures. Killer activity increased with increasing NaCl or KC1 concentration, although NaCl was more effective than KCl.