Molecular Mechanisms of Succinimide Formation from Aspartic Acid Residues Catalyzed by Two Water Molecules in the Aqueous Phase

Aspartic acid (Asp) residues are prone to nonenzymatic isomerization via a succinimide (Suc) intermediate. The formation of isomerized Asp residues is considered to be associated with various age-related diseases, such as cataracts and Alzheimer’s disease. In the present paper, we describe the reaction pathway of Suc residue formation from Asp residues catalyzed by two water molecules using the B3LYP/6-31+G(d,p) level of theory. Single-point energies were calculated using the MP2/6-311+G(d,p) level of theory. For these calculations, we used a model compound in which an Asp residue was capped with acetyl and methylamino groups on the N- and C-termini, respectively. In the aqueous phase, Suc residue formation from an Asp residue was roughly divided into three steps, namely, iminolization, cyclization, and dehydration, with the activation energy estimated to be 109 kJ mol⁻¹. Some optimized geometries and reaction modes in the aqueous phase were observed that differed from those in the gas phase.     

Electro-oxidation of N-hydroxy imides for redox mediator in acetonitrile containing lutidine as a base

The electrochemical properties of two N-hydroxy imides, N-hydroxymaleimide and N-hydroxysuccinimide, at a glassy carbon electrode in acetonitrile were examined by cyclic voltammetry. N-hydroxysuccinimide, which contains no olefinic linkage, indicated a chemically reversible redox response, and its ability as a mediator for the oxidation of benzyl alcohol was confirmed by rotating disk electrode voltammetry.     

Adrenergic regulation of bone metabolism: possible involvement of sympathetic innervation of osteoblastic and osteoclastic cells

It has been demonstrated that human osteoblastic as well as osteoclastic cells are equipped with adrenergic receptors and neuropeptide receptors and that they constitutively express diffusible axon guidance molecules that are known to function as a chemoattractant and/or chemorepellent for growing nerve fibers. These findings suggest that the extension of axons of sympathetic and peripheral sensory neurons to osteoblastic and osteoclastic cells is required for the dynamic neural regulation of local bone metabolism. Recently, bone resorption modulated by sympathetic stimulation was demonstrated to be associated with ODF (osteoclast differentiation factor) and OCIF (osteoclastogenesis inhibitory factor) produced by osteoblasts/stromal cells. This review summarizes the evidence implicating sympathetic neuron action in bone metabolism. The possible function of osteoclastogenesis, which could result in the initiation of sympathomimetic bone resorption, is also discussed.     

Use of Double Wash-Coatings of Platinum and Zeolite Catalysts to Improve Selective Reduction of NOx by Hydrocarbons

The selective catalytic reduction by hydrocarbons (HC-SCR) of NO _x under lean conditions has been improved by the use of double-layered catalysts with a lower layer of Pt/SiO₂ and an upper layer of a zeolite such as H-, Ce-, and Cu-ferrierite (-FER). H-FER wash-coated over Pt/SiO₂ (H-FER//Pt/SiO₂) performed best among the samples examined. The promotional effect was attributed to the synergy of the oxidation catalyst (Pt/SiO₂) in converting NO into NO₂, which is more reactive to C₃H₆, and the HC-SCR catalyst (H-FER). Cu-FER//Pt/SiO₂ was also effective at widening the temperature window, but with this combination the performance was attributed to a simple summation of the activity of two HC-SCR catalysts that were active at different temperatures.     

A study on flammability limits of fuel mixtures

Flammability limit measurements were made for various binary and ternary mixtures prepared from nine different compounds. The compounds treated are methane, propane, ethylene, propylene, methyl ether, methyl formate, 1,1-difluoroethane, ammonia, and carbon monoxide. The observed values of lower flammability limits of mixtures were found to be in good agreement to the calculated values by Le Chatelier's formula. As for the upper limits, however, some are close to the calculated values but some are not. It has been found that the deviations of the observed values of upper flammability limits from the calculated ones are mostly to lower concentrations. Modification of Le Chatelier's formula was made to better fit to the observed values of upper flammability limits. This procedure reduced the average difference between the observed and calculated values of upper flammability limits to one-third of the initial value.     

On the pressure dependence of flammability limits of CH2=CFCF3, CH2F2 and methane

Flammability limits of CH₂=CFCF₃ (HFO-1234 yf), CH₂F₂ (HFC-32), and methane were measured at pressures from ambient to 2500 kPa in a 5 l stainless-steel spherical vessel. For HFO-1234 yf, as the pressure rises from ambient, the lower flammability limit is shifted downward and the upper limit is shifted upward. The changes to the lower flammability limits are, in general, small compared to the upper flammability limits. Both the lower and upper flammability limits of this compound can be approximated by simple logarithmic functions of pressure. For HFC-32, the behavior of lower flammability limit is similar to that for HFO-1234 yf, but the behavior for the upper limit is rather complicated. As the pressure is increased, it begins to rise upward gradually. Then, as the pressure becomes larger than about 1000 kPa it begins to rise upward rapidly, and then the change becomes moderate again. This must be due to a change of combustion reaction mechanism below 1000 kPa and above 1500 kPa in the upper flammability limit region for this compound. On the other hand, both the flammability limits of methane change almost linearly with pressure, at least in the pressure region considered.     

A non-blocking locking method and performance evaluation on network of workstations

A network of workstation(NOW) can act as a single and scalable powerful computer by building a paralle and distributed computing platform on top of it.WAKASHI is such a platform system that supports persitent object management and makes full use of resources of NOW for high perforance transaction processing,One of the main difficulties to overcome is the bottleneck caused by concurrency control mechanism.Therefore,a non-bloking locking method is designed,by adopting several novel techniques to make it outperform the other typical locking methods such as 2PL:1) an SDG (Semantic Dependency Graph)based non-blocking locking protocol for fast transaction scheduling;2) a nmassively virtual memory based backup-page undo algorithm for fast restart;and 3) a multi-processor and multi-thread based transaction manager for fast execution.The new mechanisms have been implemented in WAKASHI and the performance comparison experiments have been implemented in WAKASHI and the performance comparison experiments with 2PL and DWDL have been done.The results show that the new method can outperform 2PL and DWDL under certain conditons.This is meaningful for choosing effective concurrency control mechanisms for improving transaction-rpocessing performance in NOW environments.     

Stereochemical effects on the fragmentation in mass spectrometry of stereoregular oligomers of methyl methacrylate

Summary The effects of stereochemical structure of MMA oligomers on the fragmentation during ionization process in electron-impact ionization and chemical ionization mass spectrometry were studied using the oligomers prepared by stereospecific living oligomerization. The MMA oligomers having t-C₄H₉-group at the left end and methine proton at the right end showed strong tacticity dependence in their fragmentation process. Fragmentation of MMA tetramer having one head-to-head linkage in the middle of the chain was also studied.     

Hepatitis B virus with X gene mutation is associated with the majority of serologically "silent" non-b, non-c chronic hepatitis

Hepatitis B virus (HBV) with X gene mutations has been a putative pathogen of chronic hepatitis without serological markers of known hepatitis viruses. The aim of this study was to reconfirm whether the HBV with the X gene mutation is associated with these serologically "silent" non-B, non-C (NBNC) chronic hepatitis, alcoholic liver disease (ALD) and autoimmune hepatitis (AIH). HBV DNA was amplified from serum and sequenced in 30 patients with NBNC chronic hepatitis in comparison with 20 patients with ALD and 5 patients with AIH. HBV DNA was identified in 21 patients (70%) in NBNC chronic hepatitis by nested polymerase chain reaction while only one patient (5%) in ALD and none in AIH showed HBV DNA. Eighteen (85.7%) of the 21 identified HBV DNAs had an identical 8-nucleotide deletion mutation at the distal part of the X region. This mutation affected the core promoter and the enhancer II sequence of HBV DNA and created a translational stop codon which truncated the X protein by 20 amino acids from the C-terminal end. All the HBV DNAs had a precore mutation at the 83rd nucleotide resulting in disruption of HBe antigen synthesis. These results indicate that HBV mutants are closely associated with the majority of serologically "silent" NBNC chronic hepatitis cases and the population of such mutant HBV DNAs is not uniform.     

One-electron redox reaction of di-tert-butyl nitroxide at platinum electrode in acetonitrile

The electrochemical oxidation of di-tert-butyl nitroxide (DTBN) at a platinum electrode in acetonitrile was examined. The cyclic voltammogram indicated an irreversible response during a normal time scale measurement, whereas chemically reversible voltammograms were obtained during a shorter time using a micro disk electrode with relatively fast sweep rates. The apparent formal redox potential and heterogeneous electron transfer rate constant were estimated to be 0.218 V (versus Fc⁺|Fc) and 0.035 ± 0.015 cm s⁻¹ from the digital simulation analysis.