Brain acetylhydrolase that inactivates platelet-activating factor is a G-protein-like trimer

The platelet-activating factor PAF (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a potent lipid first messenger active in general cell activation, fertilization, inflammatory and allergic reactions, asthma, HIV pathogenesis, carcinogenesis, and apoptosis. There is substantial evidence that PAF is involved in intracellular signalling, but the pathways are poorly understood. Inactivation of PAF is carried out by specific intra- and extracellular acetylhydrolases (PAF-AHs), a subfamily of phospholipases A2 that remove the sn-2 acetyl group. Mammalian brain contains at least three intracellular isoforms, of which PAF-AH(Ib) is the best characterized. This isoform contains a heterodimer of two homologous catalytic subunits alpha1 and alpha2, each of relative molecular mass 26K, and a non-catalytic 45K beta-subunit, a homologue of the beta-subunit of trimeric G proteins. We now report the crystal structure of the bovine alpha1 subunit of PAF-AH(Ib) at 1.7 A resolution in complex with a reaction product, acetate. The tertiary fold of this protein is closely reminiscent of that found in p21(ras) and other GTPases. The active site is made up of a trypsin-like triad of Ser 47, His 195 and Asp 192. Thus, the intact PAF-AH(Ib) molecule is an unusual G-protein-like (alpha1/alpha2)beta trimer.     

Quasi-cyclic dyadic codes in the Walsh-Hadamard transform domain

A code is s-quasi-cyclic (s-QC) if there is an integer s such that cyclic shift of a codeword by s-positions is also a codeword. For s = 1, cyclic codes are obtained. A dyadic code is a code which is closed under all dyadic shifts. An s-QC dyadic (s-QCD) code is one which is both s-QC and dyadic. QCD codes with s = 1 give codes that are cyclic and dyadic (CD). We obtain a simple characterization of all QCD codes (hence of CD codes) over any field of odd characteristic using Walsh-Hadamard transform defined over that finite field. Also, it is shown that dual a code of an s-QCD code is also an s-QCD code and s-QCD codes for a given dimension are enumerated for all possible values of s.     

The propeptide of the vitamin K-dependent carboxylase substrate accelerates formation of the gamma-glutamyl carbanion intermediate

Vitamin K-dependent carboxylase catalyzes the post-translational gamma-carboxylation of 9-12 glutamyl residues of several blood coagulation proteins. Carboxylase purified from Chinese hamster ovary (CHO) cells as a recombinant FLAG-carboxylase fusion protein [Sugiura, I., et al. (1996) J. Biol. Chem. 271, 17837-17844] was utilized with pentapeptide substrate FL[3H-R,S]EAL with high specific radioactivity to probe the timing of glutamyl Cgamma-3H cleavage relative to Cgamma-COO- bond formation by 14CO2 incorporation rates. Studies were conducted over a range of NaH14CO3 concentrations to assess uncoupling of gamma-glutamyl carbanion formation and over a range of concentrations of ProPT18, the 18-residue peptide corresponding to the -18 to -1 propeptide region of prothrombin known to affect the catalytic efficiency of carboxylase. At saturation, ProPT18 accelerates Cgamma-3H cleavage 11-13-fold and Cgamma-14CO2- formation 6-7-fold, converting a Cgamma-3H cleavage/Cgamma-14CO2- formation ratio of 1.2-1.4 in the absence of ProPT18 to 2.3-2.8 in its presence, a relative increase in and uncoupling of Cgamma-3H cleavage from C-C bond formation. When the HCO3- concentration was varied, the V/K3H+/V/K14CO2 ratios rose as HCO3- fractional saturation dropped to a ratio of 9.3-10.8/l at low bicarbonate, indicating an uncoupling of nine out of ten gamma-glutamyl carbanion formations from carboxylative capture, consistent with prior reports on microsomal enzyme [Larson, A. E., et al. (1981) J. Biol. Chem. 256, 11032-11035]. These results with pentapeptide substrate FLEAL validate reversible gamma-glutamyl carbanion formation by pure carboxylase and indicate the ProPT18 increase in catalytic efficiency is in selective lowering of an energy barrier preceding the gamma-glutamyl carbanion intermediate.     

Standardization of the Chinese MMPI–A in Hong Kong: A preliminary study.

The Chinese Minnesota Multiphasic Personality Inventory—Adolescents (MMPI—A) was applied in Hong Kong to a normative sample of 565 male and 664 female students ages 14–18. The Chinese adolescents' MMPI–A T scores based on the U.S. adolescent norms were elevated more than 1 SD on Scale 2. Similar elevations were found on Scale L (Lie) for the female students and on Scale A-lse (Adolescent Low Self-Esteem) for the male students. Moderate elevations were also shown on several scales, although none of the clinical scales exceeded a T score of 65, the clinical cutoff point based on U.S. norms. Whether these elevations were due to cultural differences in item interpretation or higher levels of psychopathology among the Hong Kong students cannot be concluded from the present data. However, previous findings on the Chinese MMPI favors the former explanation. These cultural differences should be taken into consideration in clinical interpretations of elevated scores on the Chinese MMPI—A. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Degenerate-cross-phase modulation of femtosecond laser pulses in a birefringent single-mode optical fiber

Degenerate-cross-phase modulation has been observed for femtosecond laser pulses propagating through a short birefringent single-mode optical fiber. The difference in the spectral broadening of the two output polarization components of a single laser pulse was attributed to the combination of self-phase modulation and degenerate-cross-phase modulation processes in the optical fiber. Theoretical simulations based on the solutions of the two coupled nonlinear Schrodinger equations are in good agreement with the measured results.     

直接拉伸试验及Superpave规范系统研究蜡对沥青低温性能的影响

用两种不同分子量的石蜡及一种微晶蜡掺和在沥青中,来研究蜡的性能(如分子量分布、平均分子量等)对沥青低温性能的影响.用Superpave沥青胶结料性能规范系统的BBR、DTT、临界龟裂温度(Tcritical)及玻璃转换温度(Tg)来研究掺有3%或6%蜡的沥青低温性能,低分子量及分子量分布窄的石蜡降低了沥青的DTT破坏应力,同时增加了正割模量(Secant Modulus)及BBR的热应力.微晶蜡对沥青的DTT破坏应力的影响比较少,并且不影响正割模量,但增加了BBR的热应力;但当将不同蜡的沥青混合,即将蜡的分子量分布扩大,则DTT破坏应力略为降低,正割模量不变,而BBR的热应力则减少.换言之,如果将含不同蜡的沥青混合,则蜡对沥青低温性能的影响降低,这会改善含蜡沥青的低温性能,原因可能是蜡的凝结受其分子量所影响,较宽的分子量分布会导致蜡在较宽的温度范围内慢慢凝结,缓和了蜡突然结晶对沥青低温性能的有害反应.     

Hemostatic risk factors of coronary artery disease in the Chinese

Induction of the mitochondrial permeability transition in vitro is well-characterized and widely implicated in the mechanism of oxidant-induced cell death. Despite an abundance of in vitro evidence, implication of mitochondrial dysfunction in the mechanism of chemical toxicity in vivo awaits demonstration of the induction of the mitochondrial permeability transition in tissues from intoxicated animals. Menadione (2-methyl-1,4-naphthoquinone), an agent known to induce the permeability transition in isolated liver mitochondrial in vitro, was administered as a single bolus to adult male rats, and hepatic mitochondria were isolated 24 h later. Mitochondria from menadione-treated rats exhibited an increased sensitivity to calcium-induced inhibition of state 3 respiration and loss of respiratory control, as well as a greater sensitivity to calcium-induced calcium release that was inhibited by cyclosporine A. Associated with this was the depolarization of membrane potential and swelling of mitochondria from menadione-treated animals, but not control animals. Both the calcium-dependent depolarization and swelling of mitochondria from menadione-treated rats were inhibited by adding either cyclosporine A or ruthenium red. The results are consistent with the induction of the mitochondrial permeability transition and provide the first evidence for the manifestation of an increased sensitivity to this response as a result of chemical exposure in vivo.     

Fabrication of a highly bendable LCD with an elastomer substrate by using a replica‐molding method

Abstract— A highly bendable liquid‐crystal display was fabricated by using a multi‐functional elastomer substrate of self‐aligning LC molecules without any surface treatment. One of the two substrates is a plastic substrate while the other is a multi‐functional elastomer substrate produced by a replica‐molding technique. The multi‐functional elastomer substrate has pixel‐encapsulating walls that serve as spacers and provide mechanical stability and reproducibility against bending deformations. The highly bendable LCD demonstrates great flexibility, durability, and excellent electro‐optic performances in a highly bent state.     

TEM studies of strain-induced martensitic formation in fatigued Fe-18Mn alloy

Austenitic Fe-18Mn alloy was cyclically deformed at various total strain amplitudes. The structural changes induced by cyclic straining in Fe-18Mn alloy were investigated by transmission electron microscopy. At a low strain amplitude of 0.4%, the formation ofε-martensite associated with deformation twins and stacking faults was observed in this alloy. As the applied strain amplitude was increased to 1.0%,α′-martensite embryos were induced in the alloy investigated. These embryos coalesce into a lath structure upon subsequent cyclic deformation.