Lysozyme requires fluctuation of the active site for the manifestation of activity

Mutations around His15 which lie far away from the active site,stimulated glycol chitin activity of lysozyme at physiologicaltemperature. Del-Argl4Hisl5 lysozyme, a mutant lysozyme whoseArgl4 and Hisl5 were deleted together, and has the highest activityamong these mutant lysozymes, had a similar binding abilityto a trimer of N-acetyl-glucosamine, a substrate analogue, relativeto native lysozyme. This suggests that the increased activitywas due to an increased k_cat in the catalysis reaction. TheH-D exchange rate of the N-1 proton in the Trp63 which is locatedin the active site cleft, was enhanced in the Del-Argl4Hisl5lysozyme, while 2-D proton NMR analysis revealed no conformationalchange around Trp63. We conclude that some sort of fluctuationat the active site might be required for the manifestation ofactivity. This theory is supported by the finding that the Del-Argl4Hisl5lysozyme showed a shift in temperature dependency of activityto lower temperatures compared with that of native lysozyme.     

Synthesis of sulfonated organic–inorganic hybrids through the radical copolymerization of vinyl sulfonate esters and vinyl trialkoxysilanes

Novel organic–inorganic hybrids with sulfonic acid groups were prepared using random copolymers composed of vinyl sulfonate esters and vinyl trialkoxysilanes. Five vinyl sulfonate esters with different substituent groups were employed as protecting monomers for the production of the poly(vinyl sulfonic acid) component, and three vinyl trialkoxysilanes were used as cross-linkable monomers. Free radical and reversible addition-fragmentation chain transfer (RAFT) copolymerizations were performed for the production of random copolymers with two different functional groups. The selective deprotection of the sulfonate esters of the copolymers proceeded smoothly and resulted in the formation of copolymers with lithium vinyl sulfonate units and cross-linkable trialkoxysilane units. The co-condensation of the trialkoxysilane moieties in the deprotected copolymers with cross-linkers yielded transparent hybrid films that contained lithium sulfonate groups without aromatic rings or ester linkages.     

Superoxide dismutase-based third-generation biosensor for superoxide anion

A third-generation biosensor for superoxide anion (O2-) was developed by immobilizing superoxide dismutase (SOD) on a self-assembled monolayer of cysteine on gold electrode; i.e., a SOD/cysteine-modified gold electrode (SOD/Cys/Au) was fabricated. A rapid and direct electron transfer of SOD was realized at the gold electrode by using the cysteine molecule as an electron-transfer promoter. The promoted direct electron transfer of SOD and biomolecular recognition by the exploitation of specific and significant enzyme-substrate reactivity of SOD toward O2- combined with the low operating potential enabled a sensitive measurement of O2-. At SOD/Cys/Au, O2- could be specifically oxidized and reduced to O2 and hydrogen peroxide, respectively, through the inherent catalytic reaction of SOD. This allowed us to measure O2- by polarizing the electrode both anodically and cathodically. We could successfully measure O2- by suitably polarizing the electrode, typically at 300 and -200 mV versus Ag/AgCl without the virtual interference from physiological levels of H2O2, ascorbic acid, uric acid, and metabolites of neurotransmitters. The response mechanism of SOD/Cys/Au to O2- and its sensor characteristics are also presented and discussed.     

Intra-molecular mobility of holes along rod-like helical Si backbones in optically active polysilanes

Intra-molecular mobility of positive charge carriers in poly(n-hexyl-[S]-2-methylbutylsilane) (PHMBS) films doped with N,N′-bis(2,5-di-tert-buthylphenyl)-3,4,9,10-perylenedicarboximide (PDI) is studied by time-resolved microwave conductivity (TRMC) measurements. PHMBS with optically active side chains has a rod-like tightly locked Si catenation with unlikely long persistence length compared with conventional dialkyl-substituted polysilanes. It was found that PDI is a suitable electron acceptor for PHMBS as it provides the high product of photo carrier generation yield ? as ～0.08% under an excitation at 355 nm. The efficient electron transfer reaction from PHMBS to PDI gives clear conductivity transients ascribed to the positive charges on the Si catenation of PHMBS by TRMC measurements. The estimated value of isotropic mobility along the tightly locked Si catenation is 0.36 cm² V^?1 s^?1, suggesting the presence of mobile holes on the backbones of PHMBS.     

Low dissipation current GaAs prescaler IC

A 1 GHz variable modulus freqency divider with very low dissipation current has been developed. Using a high-transconductance (200?250 mS/mm) FET by Pt burying technology and series gating source-coupled FET logic, the dissipation current of the fabricated IC was reduced to 3.2 mA at 1 GHz operation.     

A facile approach to the fabrication of ultrathin polymer films and application to optical lenses

A facile approach to the fabrication of ultrathin polymer films on a flat or curved substrate is presented. Polymers with unsaturated pendant groups were spin-coated on a photoinitiator tethered surface, which was then photoirradiated and washed with a solvent. The obtained films were uniform, smooth (R_a < 0.2 nm) and exhibited robustness toward solvents. The thickness of the films was determined by the molecular weight of the coated polymer and was not dependent on the initial spin-coated thickness. A mechanism for the formation of the ultrathin film and application to optical lenses is presented.     

PIV measurement and turbulence scale in turbulent combustion

We have investigated turbulent combustion by PIV (Particle Image Velocimetry) technique. Comparing with LDV data, the validity of PIV measurements has been confirmed. Particularly, the conditions of sampling number and spatial resolution have been shown to yield reliable data using PIV. Based on the velocity fields in cold flow and combustion, the interaction between flame and flow has been discussed. It was observed that the flow field is changed by combustion and the turbulence is reduced. In order to determine statistical quantities such as mean velocity and RMS of velocity fluctuation, a sampling number of 1000 is needed. Moreover, the velocity correlation coefficient was evaluated to obtain the integral length scale of the flow. For both cold flow and combustion, the PIV estimated scale is very close to that of LDV based on the assumption of Taylor's hypothesis. As a result, the spatial resolution in this study is about 6 times smaller than the integral length scale. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(7): 501–512, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20129