生物信息学方法推测脊椎动物血红蛋白相互作用机制

目的 通过分析脊椎动物血红蛋白(Hb)分子进化过程,解释Hb相互作用的现象并推测作用机制.方法 采用NCBI、PDB等在线生物信息学网站及SMS、ANTHEPROT 5.0、Clustalx 2.0、MEGA 4、Vector NTI 9等软件包对比脊椎动物门各纲羊膜和非羊膜动物Hb氨基酸多序列的同源相似性,查找保守位点,构建分子进化树,预测二级结构,对比三级结构模型,推测Hb相互作用现象的发生机制.结果 氨基酸多序列对比显示,非羊膜动物α链没有保守氨基酸(cAA),β链有3个cAA,羊膜动物α链、β链分别有27个和68个cAA;分子进化树显示非羊膜动物Hb氨基酸每位点替代值(SpS)远大于羊膜动物(P<0.01);预测二级结构分析Hb作用面发现非羊膜动物α链40位氨基酸主要参与无规则卷曲结构,羊膜动物α链40位和β链94位氨基酸均主要参与α螺旋结构;对比空间结构模型发现羊膜动物α链均有一个苏氨酸(41位)与β链的组氨酸(98位)形成氢键,而非羊膜动物不能形成此氢键.结论 脊椎动物Hb相互作用发生的关键可能在于是否存在α链苏氨酸(41位)与β链组氨酸(98位) 形成的氢键.     

Photocatalytic Hydrogen Evolution from Artificial Seawater Splitting over Amorphous Carbon Nitride: Optimization and Process Parameters Study via Response Surface Modeling

Photocatalytic water splitting has garnered tremendous attention for its capability to produce clean and renewable H₂ fuel from inexhaustible solar energy. Until now, most research has focused on scarce pure water as the source of H₂, which is not consistent with the concept of sustainable energy. Hence, the importance of photocatalytic splitting of abundant seawater in alleviating the issue of pure water shortages. However, seawater contains a wide variety of ionic components which have unknown effects on photocatalytic H₂ production. This work investigates photocatalytic seawater splitting conditions using environmentally friendly amorphous carbon nitride (ACN) as the photocatalyst. The individual effects of catalyst loading (X₁), sacrificial reagent concentration (X₂), salinity (X₃), and their interactive effects were studied via the Box–Behnken design in response surface modeling towards the H₂ evolution reaction (HER) from photocatalytic artificial seawater splitting. A second-order polynomial regression model is predicted from experimental data where the variance analysis of the regressions shows that the linear term (X₁, X₂), the two-way interaction term X₁X₂, and all the quadratic terms (X₁₂, X₂₂, X₂₃) pose significant effects towards the response of the HER rate. Numerical optimization suggests that the highest HER rate is 7.16 µmol/h, achievable by dosing 2.55 g/L of ACN in 45.06 g sea salt/L aqueous solution containing 17.46 vol% of triethanolamine. Based on the outcome of our findings, an apparent effect of salt ions on the adsorption behavior of the photocatalyst in seawater splitting with a sacrificial reagent has been postulated.     

枸橼酸氢钾钠溶解肾集合管结晶的临床观察

目的探讨枸橼酸氢钾钠溶解。肾集合管结晶的疗效。方法筛选22例肾集合管结晶患者，给予枸橼酸氢钾钠10g／d，比较治疗前后症状和实验室检查的变化。结果治疗后，患者腰痛和尿路刺激症状明显减少（86．4％vs13．6％，68．2％VS4．5％，P〈O．05），同时尿红细胞和白细胞大幅减少，肾脏多普勒显示集合管结晶有明显改善（95．5％vs9．1％，68．2％vs13．6％，100％掷22．7％，P〈0．05）。结论枸橼酸氢钾钠能有效溶解肾集合管结晶，减少肾结石的发生。     

缬沙坦对过氧化氢损伤乳鼠心肌细胞的保护作用

目的探讨缬沙坦对过氧化氢（H2O2）致心肌细胞氧化损伤的保护作用及其机制。方法用H2O2作用于新生SD大鼠心肌细胞,建立心肌细胞H2O2损伤模型。用缬沙坦预处理后,观察心肌细胞结构,测定心肌细胞存活率、乳酸脱氢酶（LDH）、丙二醛（MDA）及一氧化氮（NO）水平。结果缬沙坦提高心肌细胞过氧化损伤的细胞存活率（P〈0.05）,减少损伤时LDH、MDA和NO的生成（P〈0.05）。结论缬沙坦通过抗氧化、抗脂质过氧化反应,对心肌细胞过氧化损伤起保护作用。     

Hydrogen Transportation Behaviour of V–Ni Solid Solution: A First-Principles Investigation

Hydrogen embrittlement causes deterioration of materials used in metal–hydrogen systems. Alloying is a good option for overcoming this issue. In the present work, first-principles calculations were performed to systematically study the effects of adding Ni on the stability, dissolution, trapping, and diffusion behaviour of interstitial/vacancy H atoms of pure V. The results of lattice dynamics and solution energy analyses showed that the V–Ni solid solutions are dynamically and thermodynamically stable, and adding Ni to pure V can reduce the structural stability of various VH_x phases and enhance their resistance to H embrittlement. H atoms preferentially occupy the characteristic tetrahedral interstitial site (TIS) and the octahedral interstitial site (OIS), which are composed by different metal atoms, and rapidly diffuse along both the energetically favourable TIS → TIS and OIS → OIS paths. The trapping energy of monovacancy H atoms revealed that Ni addition could help minimise the H trapping ability of the vacancies and suppress the retention of H in V. Monovacancy defects block the diffusion of H atoms more than the interstitials, as determined from the calculated H-diffusion barrier energy data, whereas Ni doping contributes negligibly toward improving the H-diffusion coefficient.     

Transforming Pt-SnO2 Nanoparticles into Pt-SnO2 Composite Nanoceramics for Room-Temperature Hydrogen-Sensing Applications

Many low-dimensional nanostructured metal oxides (MOXs) with impressive room-temperature gas-sensing characteristics have been synthesized, yet transforming them into relatively robust bulk materials has been quite neglected. Pt-decorated SnO₂ nanoparticles with 0.25–2.5 wt% Pt were prepared, and highly attractive room-temperature hydrogen-sensing characteristics were observed for them all through pressing them into pellets. Some pressed pellets were further sintered over a wide temperature range of 600–1200 °C. Though the room-temperature hydrogen-sensing characteristics were greatly degraded in many samples after sintering, those samples with 0.25 wt% Pt and sintered at 800 °C exhibited impressive room-temperature hydrogen-sensing characteristics comparable to those of their counterparts of as-pressed pellets. The variation of room-temperature hydrogen-sensing characteristics among the samples was explained by the facts that the connectivity between SnO₂ grains increases with increasing sintering temperature, and Pt promotes oxidation of SnO₂ at high temperatures. These results clearly demonstrate that some low-dimensional MOX nanocrystals can be successfully transformed into bulk MOXs with improved robustness and comparable room-temperature gas-sensing characteristics.     

Catalase-mimetic gold nanoparticles inhibit the antagonistic action of Lactobacillus gasseri toward foodborne enteric pathogens in associative cultures

Gold nanoparticles (AuNPs) have been previously shown to induce gut dysbiosis during colitis in mice, but the underlying mechanism is not clear yet. Here, we evaluated the effects of AuNPs (5?nm diameter, coated with tannic acid, polyvinylpyrrolidone or citrate) on H₂O₂ accumulation and pathogen antagonization by an intestinal strain of Lactobacillus gasseri under aerobic cultural conditions. AuNPs (0.65?μg/mL) reduced over 50% of H₂O₂ accumulation by L. gasseri, and significantly inhibited the antagonistic action of L. gasseri on growth of four foodborne enteric pathogens, i.e. Salmonella enterica serovar Typhimurium, Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus in associative cultures.     

Blood-Brain Barrier Permeability of Asiaticoside,Madecassoside and Asiatic Acid in Porcine Brain Endothelial Cell Model

Neurotherapeutic potentials of Centella asiatica and its reputation to boost memory, prevent cognitive deficits and improve brain functions are widely acknowledged. The plant's bioactive compounds, i.e. asiaticoside, madecassoside and asiatic acid were reported to have central nervous system (CNS) actions, particularly in protecting the brain against neurodegenerative disorders. Hence, it is important for these compounds to cross the blood-brain barrier (BBB) to be clinically effective therapeutics. This study aimed to explore the capability of asiaticoside, madecassoside and asiatic acid to cross the BBB using in vitro BBB model from primary porcine brain endothelial cells (PBECs). Our findings showed that asiaticoside, madecassoside and asiatic acid are highly BBB permeable with apparent permeability (P_app) of 70.61 ± 6.60, 53.31 ± 12.55 and 50.94 ± 10.91 × 10^?6 cm/s respectively. No evidence of cytotoxicity and tight junction disruption of the PBECs were observed in the presence of these compounds. Asiatic acid showed cytoprotective effect towards the PBECs against oxidative stress. This study reported for the first time that Centella asiatica compounds demonstrated high capability to cross the BBB, comparable to central nervous system drugs, and therefore warrant further development as therapeutics for the treatment of neurodegenerative diseases.     

Hydrogen Production by Steam Reforming of Ethanol over Nickel Catalysts Supported on Sol Gel Made Alumina: Influence of Calcination Temperature on Supports

Selecting a proper support in the catalyst system plays an important role in hydrogen production via ethanol steam reforming. In this study, sol gel made alumina supports prepared for nickel (Ni) catalysts were calcined at different temperatures. A series of (Ni/Al_S.G.) catalysts were synthesized by an impregnation procedure. The influence of varying the calcination temperature of the sol gel made supports on catalyst activity was tested in ethanol reforming reaction. The characteristics of the sol gel alumina supports and Ni catalysts were affected by the calcination temperature of the supports. The structure of the sol gel made alumina supports was transformed in the order of γ → (γ + θ) → θ-alumina as the calcination temperature of the supports increased from 600 °C to 1000 °C. Both hydrogen yield and ethanol conversion presented a volcano-shaped behavior with maximum values of 4.3 mol/mol ethanol fed and 99.5%, respectively. The optimum values were exhibited over Ni/Al_S.G800 (Ni catalyst supported on sol gel made alumina calcined at 800 °C). The high performance of the Ni/Al_S.G800 catalyst may be attributed to the strong interaction of Ni species and sol gel made alumina which lead to high nickel dispersion and small particle size.