INHIBITION OF CORROSION BY HEXADECYL TRIMETHYL AMMONIUM BROMIDE LANGMUIR-BLODGETT MONOLAYERS ON CARBON-STEEL

Langmuir-Blodgett (LB) monolayers of hexadecyl trimethyl ammonium bromide (HTAB) were deposited onto a carbon steel surface to investigate the inhibition of corrosion by measurement of the polarization resistance and cyclic voltammetry. The corrosion proc

Nitrogen isotope fractionation during nitrate, ammonium and urea uptake by marine diatoms and coccolithophores under various conditions of N availability

Stable isotopes of N provide a new approach to the study of algal production in the ocean, yet knowledge of the isotope fractionation (epsilon) in various oceanic regimes is lacking. Here we report large and rapid changes in isotope composition (delta(15)N) of 2 coastal diatoms and 2 clones (open and coastal) of a coccolithophore grown in the simultaneous presence of nitrate, ammonium and urea under varying conditions of N availability (i.e. N-sufficiency and N-starvation followed by N-resupply) and hence different physiological states, During N-sufficiency, the delta(15)N of particulate organic N (PON) was well reproduced, using a model derived from Rayleigh distillation theory, with constant epsilon similar to that for growth on each individual N source. However, following N-resupply, the variations in delta(15)N(PON) could be well explained only in the case of the open ocean Emiliania huxleyi, with epsilon similar to N-sufficient conditions. It was concluded that the mechanism of isotope fractionation changed rapidly with N availability for the 3 coastal clones. However, in the case of E. huxleyi isolated from the Subarctic Pacific Ocean, no evidence of a change in mechanism was found, suggesting that perhaps open ocean species can quickly recover from N-depleted conditions.

Relevance of molecular weight of chitosan-N-2-hydroxypropyl trimethyl ammonium chloride and their antioxidant activities

The antioxidant potency of high/low molecular weight quatemary chitosan derivatives was investigated employing various established systems in vitro, such as superoxide (O-2(center dot-)) and hydroxyl (center dot OH) radicals scavenging, reducing power and iron ion chelating. As expected, we obtained several satisfying results, as follow: firstly, low molecular weight quaternary chitosan had stronger scavenging effect on O-2(center dot-) and center dot OH than high molecular weight quaternary chitosan. Secondly, the reducing power of low molecular weight quaternary chitosan was more pronounced than that of high molecular weight quaternary chitosan. Thirdly, ferrous ion chelating potency were showed to increase first and decrease afterwards with increasing concentration for two kinds of quaternary chitosans, namely, they have not concentration-dependence. However, the scavenging rate and reducing power of high and low molecular weight quaternary chitosans increased with their increasing conc centrations, and hence were concentration-dependent. (c) 2007 Elsevier Masson SAS. All rights reserved.

Studies on the phase diagram of the surfactant/1-pentanol water ternary system I: The isotropic phases

The phase diagram of the dodecyl dimethyl ammonium hydroxyl propyl sulfonate(DDAHPS)/1-pentanol(C5H11OH)/water ternary system has been established. It contains two isotropic monophase regions (L-1 and L-2) and a liquid crystalline region (L.C.). The isotropic phase regions have been investigated by means of Raman spectroscopy and conductivity.

Difference in Enzyme Activity and Conformation of Glucose Oxidase Before and After Purification

EEnzyme activity of commercial glucose oxidase was enhanced after purification through a strong anionic exchange resin. In order to get a better insight into this phenomenon, surface pressure–area ( –A) isotherms and surface pressure–time ( –t) isotherms was used to study the interaction and the absorption at different pH values of the subphases between octadecylamine and glucose oxidase purified by a styrene system quaternary ammonium type strongly basic anionic exchange resin. Circular dichroism (CD), electrophoresis and enzyme activity measurements were conducted to study these phenomena. A preliminary hypothesis has been suggested to explain why the enzyme activity of purified glucose oxidase was higher than that of the commercial one. © 2002 Elsevier Science B.V. All rights reserved.

Studies on the phase diagram of the surfactant/1-pentanol water ternary system II: The liquid crystalline phase

The phase behavior of liquid crystalline in the ternary system of dodecyl dimethyl ammonium hydroxyl propyl sulfonate(DDAHPS)/1-pentanol(C5H11OH)/water deuteron (D2O) has been investigated by polarizing optical microscopy, H-2 NMR spectroscopy methods. The results indicate that two kinds of liquid crystals (the lamellar, and the hexagonal) exist in the liquid crystalline phase region. In this paper, we also use the polarized Raman spectroscopy method to measure the values of the order/disorder parameters and the values of the environment polarity parameters for the samples selected from the liquid crystalline phase region, and compare these two parameters of the samples with those of solid state DDAHPS and liquid state pentan-1-ol.

联合固氮菌Enteroabcter gergoviae 57-7氮代谢相关基因的克隆和泌氨工程菌的构建

从构建具有稳定泌氨能力的联合固氮工程菌的目的出发，首先构建Enterobacter gergoviae57-7 (E57-7)基因文库并与所筛选的泌氨突变株进行遗传互补实验，得到可互补 泌氨特性的克隆，经Southern杂交后推测其中包含与glnA、amtB基因无关的另一类与泌 氨相关的基因。同时根据铵载体基因amtB的已知序列设计两对简并性引物，经PCR从 E57-7 DNA中扩增得到约340bp的片段，序列分析和Blast序列同源性比较后确定为amtB 基因片段，申报并获得序列号AJ132232，最终从基因库中筛选到两个包含E57-7 amtB 基因的克隆。 用K. pneumoniae的glnA基因片段为探针，通过Southern杂交从E57-7基因库中筛选到包含有glnAntrBC基因的克隆，经亚克隆后对包含有这个操纵元的4316bp片段进行了全序列分析，申报GenBank获得序列号AF072440。在体外实验中构建了Km-cassette 插入glnA的重组质粒pA，将此质粒转入E57-7野生型菌株后经筛选同源重组子获得glnA 突变的具有稳定泌氨能力的菌株15、I9。并进行了盆栽玉米接种实验，确定在灭菌上壤实验体系下I5对玉米幼苗有显著促生效应。 利用绿色荧光蛋白(GFP-S65T，V68L，S72A)基因建立分子生物学研究手段，构建了新 型克隆载体pGreenLD，建立了绿白斑筛选重组质粒的的技术。构建组成型表达gfp的质粒载体研究了E57-7在玉米根际的定殖模式;构建nifH-gfp表达载体，确定在与植物联合生活时其固氮酶结构基因nifHDK的表达与碳源物质供应密切相关。利用不同抗性基因和gfp基因片段构建出在E57-7中组成型表达抗性和GFP的质粒载体，建立了监测接种菌在土壤中释放的双标记系统。 最后克隆了E57-7 glg cluster并测定部分glgCA和glgP基因序列，申报后获得序列号AJ132233和AJ132234，这是首例从联合固氮菌中克隆得到glg cluster的报道。