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Mechanical components in hydrogen energy systems, such as a fuel cell vehicle and related infrastructures, will operate in high-purity hydrogen. Especially, some seals and valves in fuel cell vehicles should articulate against metal counterface within a pressurized hydrogen gas. However, the effect of high-pressure hydrogen gas on tribological behaviour of materials used in sliding surfaces has not been identified yet. In this study, unfilled polytetrafluoroethylene (PTFE) pins and 316L austenitic stainless-steel discs were exposed to high-pressure hydrogen gas and then the chemical and physical changes in their surface and the tribological characteristics were investigated.The results of an X-ray photoelectron spectrometer analysis of the exposed stainless-steel surface indicated that metal oxides in the passive surface layer of stainless steel can be reduced significantly during the high-pressure hydrogen exposure. Increased metal contents of the stainless surface resulted in enhanced metal fluoride formation and subsequent development of a PTFE transfer film. Consequently, the exposed PTFE specimens showed lower specific wear rate when compared to the unexposed specimen.

The effects of three cyclodextrins (α-, β-, γ-CyD) on the acid hydrolysis of digoxin were examined. From the high performance liquid chromatographic tracing of each of the four components (digoxin, bisdigitoxoside, monodigitoxoside, digoxigenin) in reaction mixtures, the individual rate constants (k1-k6) were determined by analogue computer simulation. The hydrolysis was suppressed by CyDs in the order of β->γ->α-CyD, where β-CyD inhibited the appearance rates of digoxigenin (k3, k5, and k6) significantly. In the dissolution study of digoxin tablets, the increase in dissolution rate and decrease in acid hydrolysis were attained by inclusion complexation. The data are presented suggesting that CyDs are useful for improving the oral bioavailability of digoxin.

Polyethylene glycol (PEG)-linked manganese halogenated porphyrins (Chart 1) catalyzed oxidation of azo dyes (Chart 2) by H2O2 under mild conditions such as pH 8.0 at 25 °C especially when imidazole was present, causing the decoloration of azo dyes. The decoloration of azo dyes by synthetic manganese porphyrins under mild conditions was first reported. The decoloration rate depended on the structures of the porphyrins, in which the largest rate was observed in the presence of PEG−MnDCPP. The decoloration may be contributed by radical species rather than electrophilic species, consistent with the side-chain oxidation of toluene. Kinetics on polyethylene glycol-linked manganese porphyrin-catalyzed decoloration of C.I. Acid Orange 7 by hydrogen peroxide revealed that the decoloration was contributed at the oxidation process by manganese porphyrins with hydrogen peroxide in the polymer domain rather than the complex-formation process between manganese porphyrins and azo dyes.

Phospholipid-linked mesoporphyrins separated by spacer methylene groups (Cn), PE-Cn-MnMPMME (n = 0, 5, 11) (Chart 1) were synthesized. Manganese porphyrin-mediated electron transfers across a liposomal membrane and on a glassy carbon (GC) electrode covered with a phospholipid bilayer membrane were examined to provide insight into the effect of the structure of porphyrins on these electron transfers between porphyrins in lipid bilayers. Enhanced transmembrane electron transfers catalyzed by phospholipid-linked manganese porphyrin derivatives separated by spacer methylene groups (Cn)(n = 0, 5, 11) (Chart 1) were observed in a liposomal membrane only above the phase temperature of the membrane, depending on the length of the Cn and on the structure of the porphyrins. Furthermore, cyclic voltammetry on a SnO2 glass electrode or on a GC electrode modified with a DPPC membrane containing manganese porphyrins showed that one set of waves was clearly visible corresponding to the consecutive monoelectronic reduction of the manganese porphyrin unit (Mn(III)/Mn(II)) only above the phase temperature of the membrane. Phospholipid-linked manganese porphyrins on the electrode modified with a lipid bilayer membrane also caused enhanced electron transfers, depending on the length of the Cn but not on the structure of the porphyrins. Comparison of manganese porphyrin-mediated electron transfers between porphyrins in a liposomal membrane and porphyrins on a GC electrode modified with a lipid bilayer membrane is made.

Abstract:  The effect of denaturants such as urea and normal alcohols on the formation of light-harvesting (LH) polypeptides/bacteriochlorophyll a (BChla) complex (LH1 complex) in n-octyl-β-D-glucopyranoside (OG) micelle was examined to provide an insight into stability of the complex. The stabilities of the LH1 complex in OG micelle and of the complex in the chromatophore of photosynthetic bacteria were compared by addition of denaturants. The extent of stability of these complexes was monitored by the change in absorbance of Qy band of BChla in these complexes, resulting generally in the blue-shifting of the Qy band from near 870 nm to about 777 nm upon addition of these denaturants. Urea and guanidium hydrochloride (Gnd) showed a relatively weak denaturing effect. Normal alcohols showed stronger denaturing effect, depending on the hydrophobicity of the alcohols. These results imply that the stability of LH1 complex in OG micelle can be largely attributed to the hydrophobic interactions in the complex as well as that of the complex in the chromatophore of photosynthetic bacteria.

PCR was used to detect Haemophilus influenzae in samples of nasopharyngeal secretion and middle ear effusion (MEE). Nasopharyngeal secretions were collected from 102 patients with otitis media with effusion and from 111 healthy subjects. Eighty samples of MEE were collected from patients with otitis media with effusion. A pair of primers was designed to amplify a DNA segment of the gene encoding P6 outer membrane protein of H. influenzae. The amplified PCR product was detected with an internal probe that hybridized specifically to the P6 DNA of H. influenzae. Samples of MEE and nasopharyngeal secretion were also examined by a conventional culture method. The incidence of P6 gene DNA in nasopharyngeal secretions detected by PCR was about two times higher than that of H. influenzae detected by the conventional culture. Culture-positive samples were all positive in the PCR test. In MEEs, the rate of detection of the P6 gene DNA target was about five times higher than that of H. influenzae detected by the culture method. All patients who had P6 gene DNA in MEEs were found to have the DNA in nasopharyngeal secretions. These findings suggest that the presence of H. influenzae in MEEs and in nasopharyngeal secretions is more common than previously reported.

Poly(ethylene glycol) [PEG]-linked porphyrin derivatives separated by spacer methylene groups (Cn), PEG−Cn−MPFPP (M = H2, Mn; n = 0, 5, 11), PEG−C11−MTTP (M = H2, Mn), and PEG−C0−MPFPPBr8 (M = H2, Mn) (Scheme 1) were synthesized. The porphyrin portion of the poly(ethylene glycol) [PEG]-linked fluorinated porphyrin derivative has been anchored onto a lipid bilayer. PEG-linked fluorinated porphyrins easily associated with phospholipid bilayers and are chemically stable against oxidants such as H2O2. An efficient energy transfer from phospholipid-linked zinc porphyrin, PE−C0−ZnPFPP (Scheme 1), to externally added PEG−Cn−H2PFPP (n = 0, 5, 11) in the lipid bilayer was observed, depending on the length of Cn and the porphyrin structure. Ground state transmembrane electron transfer catalyzed by PEG−Cn−MnPFPP (n = 0, 5, 11) and PEG−C11−MnTTP revealed that the porphyrin causes a significant accelerated electron transfer especially when n = 11. Comparison of PEG−C11−MnPFPP- and PEG−C11−MnTTP-catalyzed electron transfer is made. The electron transfer rate was controlled not only by the separated spacer methylene groups between the porphyrin and PEG moieties but also by the structures of porphyrins.

We describe the neurologic findings in a patient with -N-acetylgalactosaminidase deficiency (Kanzaki disease). Clinical and electrophysiologic studies revealed sensory-motor polyneuropathy, and sural nerve pathology showed decreased density of myelinated fibers with axonal degeneration. The patient had mildly impaired intellectual function with abnormal brain MRI and sensory-neuronal hearing impairment with repeated episodes of vertigo attacks. These findings suggest that Kanzaki disease may develop neurologic complications in the CNS and peripheral nervous system.

The phthalazinium salts mentioned in the title are obtained as intermediates by treatment of phthalazine (I) with the acyl (II) or sulfonyl chlorides (V) and trimethyl phosphite (III).

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.