The role of the conserved threonine in P450 BM3 oxygen activation: substrate-determined hydroxylation activity of the Thr268Ala mutant

The hydroxylation activity of the Thr268Ala mutant of P450(BM3) has been shown to occur to varying degrees with small alterations in the structure of a fatty-acid substrate. Ten substrates were investigated, including straight chain, branched chain and cis-cyclopropyl substituted fatty acids with a straight-chain length that varied between 12 and 16 carbon atoms. The efficacy of the hydroxylation activity appeared to be governed by the chain length of the substrate. Substrates possessing 14 to 15 carbons afforded the highest levels of activity, which were comparable with the wild-type enzyme. Outside of this window, straight-chain fatty acids showed reduced activity over the other substrate types. These results provide a cautionary tale concerning the loss of ferryl activity in such cytochrome P450 threonine to alanine mutants, as the nature of the substrate can determine the extent to which hydroxylation chemistry is abolished.     

注射工艺对稀土β成核剂改性PP力学性能影响

考察了工艺参数对稀土β成核剂改性聚丙烯(β-PP)力学性能的影响.当注射速率在20～80 mm/s变动时,β-PP冲击强度的最大值与最小值相比提高了12.2%,熔体温度在190～250℃、保压压力在20～50 MPa和保压时间在2～60 s变动时,冲击强度相对应的提高幅度分别为22.2%,31.8%和97.7%;同时对比了不同工艺条件对α-PP(未添加β成核剂聚丙烯)和β-PP冲击性能影响的差异.结果表明.β-PP对注射工艺条件的变化更敏感.     

钽等离子体渗氮的表面过程分析

对钽表面渗氮的固－气界面反应过程进行了热力学和动力学分析,从到理论预测了各种参数（压力、气体、组成、温度、电参数等）对表面过程的影响,并借助于等离子体,在较你廿获得由层与Ｎ在ＴＡ中的固溶体组成的表面硬化层,层为六方晶系的Ｔａ６Ｎ２,５７和／或非昌态。通过调整工艺参数有效地抑制了钽表面氧的渗入和Ｔａ２Ｏ５的形成,使得离子渗氮后,仍保持较低的表面粗糙度。     

超磁致伸缩薄膜材料及其应用

超磁致伸缩薄膜是一种应用于微型机电系统及传感器的新型材料 ,它具有很高的机电耦合系数、较高的响应速度以及非接触式驱动等优点。对磁致伸缩薄膜的研究现状进行了综述 ,介绍了磁致伸缩薄膜的制备方法 ,性能特征及应用前景。     

Modelling of the disulphide-swapped isomer of human insulin-like growth factor-1: implications for receptor binding

Insulin-like growth factor-1 (IGF-1) is a serum protein whichunexpectedly folds to yield two stable tertiary structures withdifferent disulphide connectivities; native IGF-1 [18–61,6–48,47–52]and IGF-1 swap [18–61,6–47, 48–52]. Here we demonstratein detail the biological properties of recombinant human nativeIGF-1 and IGF-1 swap secreted from Saccharomyces cerevisiae.IGF-1 swap had a ~30 fold loss in affinity for the IGF-1 receptoroverexpressed on BHK cells compared with native IGF-1.The parallelincrease in dose required to induce negative cooperativity togetherwith the parallel loss in mitogenicity in NIH 3T3 cells impliesthat disruption of the IGF-1 receptor binding interaction ratherthan restriction of a post-binding conformational change isresponsible for the reduction in biological activity of IGF-1swap. Interestingly, the affinity of IGF-1 swap for the insulinreceptor was ~200 fold lower than that of native IGF-1 indicatingthat the binding surface complementary to the insulin receptor(or the ability to attain it) is disturbed to a greater extentthan that to the IGF-1 receptor. A 1.0 ns high-temperature moleculardynamics study of the local energy landscape of IGF-1 swap resultedin uncoiling of the first A-region -helix and a rearrangementin the relative orientation of the A- and B-regions. The modelof IGF-1 swap is structurally homologous to the NMR structureof insulin swap and CD spectra consistent with the model arepresented. However, in the model of IGF-1 swap the C-regionhas filled the space where the first A-region -helix has uncoiledand this may be hindering interaction of Val44 with the secondinsulin receptor binding pocket.     

COMPOSITION AND QUALITY OF THE GASOLINE OBTAINED FROM SYNGAS ON Cr2O3-ZnO/ZSM5 CATALYSTS

The kinetic equations for the formation of the lumps of the gasoline produced (C₅⁺ fraction), paraffins (C₅-C₈), xylenes (o-xylene, m-xylene and p-xylene) and aromatics (benzene, toluene, C₉-C₁₁) in the transformation of syngas on Cr₂O₃-ZnO/ZSM5 bifunctional catalyst have been established as a function of the concentration of both reactants (CO and H₂) and CO₂ byproduct. The effect of the operating conditions on the RON and on the molecular weight of the gasoline has been studied by experimentation in an integral fixed bed reactor in the range between 10 and 50atm and between 300 and 425°C. The octane index increases with Cr/Zn atomic ratio of the Cr₂O₃-ZnO metallic function, with Si/Al ratio of the HZSM5 zeolite, with space time and with the CO/H₂ molar ratio in the feed, in that order, whereas it passes through a maximum with pressure (at 20 atm) and with temperature (at 375°C). On the other hand, the molecular weight of the gasoline increases with the Cr/Zn atomic ratio, pressure, CO/H₂ molar ratio and space time, and decreases with the Si/Al ratio and temperature.     

Theoretical Evaluation of the Microporosity of Pillared Layered Double Hydroxides

Over the last ten years, the concept of pillaring has frequently been applied on layered double hydroxides (LDHs). Due to the variety of possible anionic pillaring species and the adjustable layer charge density, LDHs offer good perspectives with regard to the creation of porous adsorbents and catalysts. But despite these possibilities, their porosity properties can still not compete with those of industrially applicable materials like zeolites. In this study, theoretical calculations based on geometrical models and performed on both Fe(CN)₆-MgAl-LDHs (A) and [PV₂W¹⁰ O⁴⁰]-ZnAl-LDHs (B) were reported. Properties such as the micropore volume and the interpillar distance were calculated, and compared to experimental data. For a M(II)/M(III) ratio in the layers of 3, the theoretical maximum micropore volumes were 0.3843 cm³/g (A) and 0.1497 cm³/g (B), respectively. By implementing parameters like the stack size, pillars on the outside of the stacks and the possibility of collapse, the model was adjusted in order to create a realistic picture of the microstructure of pillared LDHs. This led to a better understanding of the limiting factors, and gave an explanation for the relatively low micropore volumes of pillared LDHs. For the Fe(CN)₆-MgAl-LDHs, small interpillar distances were responsible for the partial inaccessibility of the interlayer regions by N₂. This effect was the most pronounced for high charge density LDHs. The situation for the [PV₂W¹⁰O⁴⁰]-ZnAl-LDHs is more complex. Probably due to an incomplete pillaring process, the theoretical maximum values are not reached.     

Chemical Defenses Against Fish Predation in Three Brazilian Octocorals: 11β,12β-Epoxypukalide as a Feeding Deterrent in Phyllogorgia dilatata

The feeding-deterrence properties of crude extracts of three Brazilian octocoral species, Neospongodes atlantica Kükenthal (Alcyonacea, Nephtheidae), Plexaurella regia Castro (Gorgonacea, Plexauridae), and Phyllogorgia dilatata Esper (Gorgonacea, Gorgoniidae), were investigated. All the extracts were incorporated into food strips at the concentrations occurring in the living organisms. Crude extract and its ethyl acetate fraction obtained from P. dilatata collected in Armação dos Búzios (Rio de Janeiro State), when incorporated into artificial diets and tested in the habitat of origin, reduced consumption of food strips by fishes, relative to controls. Crude extracts from two octocoral species collected at the National Marine Park of Abrolhos (Bahia State), N. atlantica and P. regia, had no apparent feeding-deterrence properties; in fact, they seemed to stimulate feeding. Bioassay-guided fractionation of the bioactive P. dilatata crude extract revealed that the deterrent property was restricted to a medium polarity fraction. Field palatability experiments with two pure compounds isolated from this fraction revealed that the furanocembranolide 11,12-epoxypukalide is a potent feeding deterrent produced by P. dilatata against fish. Apparently, furanocembranolides are a particular class of compounds with feeding deterrent properties, protecting some octocorals from potential fish predator species in both tropical and temperate environments.     

共混方式对高密度聚乙烯/聚碳酸酯共混体系形态与性能的影响

研究了不同共混方式对高密度聚乙烯（ＨＤＰＥ）／聚碳酸酯（ＰＣ）共混体系形态与性能的影响。将不同组成的ＨＤＰＥ／ＰＣ分别在双螺杆、单螺杆挤出机中共混后注射成型,测试注射样条的力学性能并用扫描电子显微镜（ＳＥＭ）对样条断面进行形态观察。结果发现,共混方式对共混体系拉伸强度影响不大,但对冲击强度和断面形态影响较大。当ＰＣ含量低时,双螺杆的共混效果不如单螺杆;当ＰＣ含量较高时,双螺杆的共混效果优于单螺杆。