Multivariate curve resolution of rapid-scan FTIR difference spectra of quinone photoreduction in bacterial photosynthetic membranes

Photosynthetic reaction centres and membranes are systems of particular interest and are often taken as models to investigate the molecular mechanisms of selected bioenergetic reactions. In this work, a multivariate curve resolution by alternating least squares procedure is detailed for resolution of time-resolved difference FTIR spectra probing the evolution of quinone reduction in photosynthetic membranes from Rhodobacter sphaeroides under photoexcitation. For this purpose, different data sets were acquired in the same time range and spectroscopic domain under slightly different experimental conditions. To enable resolution and provide meaningful results the different data sets were arranged in an augmented matrix. This strategy enabled recovery of three different species despite rank-deficiency conditions. It also results in better definition (identity and evolution) of the contributions. From the resolved spectra, the species have been attributed to: 1. the formation of ubiquinol, more precisely the disappearance of Q/appearance of QH₂; 2. conformational change of the protein in the surrounding biological medium; 3. oxidation of diaminodurene, a redox mediator. Because, moreover, results obtained from augmented data sets strategies enable quantitative and qualitative interpretation of concentration profiles, other effects, for example the consequence of repeated light excitation of the same sample, choice of illumination power, or the number of spectra accumulated could be compared and discussed.     

Redox behavior of biofilm on glassy carbon electrode

Marine and freshwater biofilm usually shift the open circuit potential (OCP) of stainless steel towards the electropositive direction by + 450 mV vs SCE. The nature of oxide film and bacterial metabolism were also correlated with ennoblement process by various investigators. Glassy carbon electrode (GCE) was used in the present study and a shifting of potential in the positive side (+ 450 mV) was noticed. It indicates that biofilm contributes to the ennoblement process without any n/p-type semiconducting oxide film. The nature of the cathodic curve for the biofilm covered GCE is compared with the previous literature on the electrochemical behavior of stainless steel. The present study explains the oxidation and reduction peaks of biofilm covered GCE by cyclic voltammetry. Electrochemical impedance result reveals the diffusion process within the manganese biofilm. The present study confirms the previous investigations that the manganese biofilm rules the electrochemical behavior of materials and suggests that oxide film is not necessary to assist the ennoblement process.     

Microbiological analysis of seawater and sediments in urban shorelines: Occurrence of heavy metals resistance bacteria on Chennai beaches, Bay of Bengal

The present study aims to evaluate the microbial diversity of bacteria, fungi and other pathogenic microorganisms present in seawater and sediments from Chennai shoreline (southeast coast of India).Chennai beaches are heavily polluted with untreated sewage effluents; municipal sewage disposal and recreational activities. Seawater was heavily contaminated with coliforms, Vibrio and Pseudomonas compare to sediment microbial contamination. Isolated bacteria are mostly pathogenic microorganisms including Vibrio, Pseudomonas, Coliforms, Salmonella and Shigella. Another potential environmental threat noticed was heavy metal resistance of these pathogenic strains against 50 mM of Ni, Cr, Cu, Co, Pb and Hg. Statistical analyses revealed that the Chennai coast may cause health risk to the recreational users and fisher folk, ultimately warrants environmental quality management to control microbial contamination     

新型耐腐蚀含氟环氧乙烯基酯树脂的合成与性能

以含氟环氧树脂（F-EP）、丙烯酸（AA）和甲基丙烯酸（MAA）为单体,用顺丁烯二酸（MA）进行改性,合成了含氟环氧乙烯基酯树脂（F-EVER）。用傅里叶红外光谱、热重分析、力学性能分析等手段对产物进行表征,研究了树脂的耐腐蚀性能。结果表明：当以N,N-二甲基甲酰胺（DMF）为催化剂,羧基与环氧基摩尔比为0.9,MA与...     

Growth mechanism of hydroxyapatite-coatings formed on pure magnesium and corrosion behavior of the coated magnesium

Hydroxyapatite (HAp) coatings were uniformly formed on pure Mg by a hydrothermal treatment using a C₁₀H₁₂N₂O₈Na₂Ca (Ca-EDTA) solution. The growth mechanism of the HAp coating was investigated with XRD, SEM and TEM. At the initial stage, dome-shape HAp precipitates were formed on the Mg. Subsequently, the precipitates grew and the coating became a dual-layer consisting of an inner dense HAp layer and outer course layer consisting of rod-like HAp crystals. The protectiveness of the coatings with different treatment times was investigated by a polarization test in a 3.5 wt.% NaCl solution. The corrosion current density decreased with the growth of the HAp coating.     

Soluble aromatic polyamides modified by incorporation of 1,2,4-triazole and pentadecyl units into the backbone of polymer

Abstract

A new series of soluble aromatic polyamides was synthesized by low temperature solution polycondensation of novel aromatic diamine namely 3,5-bis-(4′-amino phenyl)-4-(4″-methoxy-2″-pentadecyl phenyl) 1,2,4-triazole (VII) with aromatic diacid chlorides, viz. isophthaloyl chloride (IPC) and terephthaloyl chloride (TPC). The aromaticdiamine (VII) was characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C), and mass spectrometry. Copolyamides were also synthesized by employing various mole proportions of IPC and TPC with diamine (VII). Inherent viscosities of these polyamides were in the range of 0.50–0.65 dL/g in DMAc, indicating formation of moderate to high molecular weight of polyamides. These polyamides showed good solubility in polar aprotic solvents such as N,N-Dimethyl acetamide (DMAc), N-Methyl 2-pyrrolidone (NMP), N, N, Dimethyl formamide (DMF), and Dimethyl sulphoxide (DMSO), which may be due to incorporation of pendant methoxyphenyl moiety with pentadecyl units. The amorphous morphology of polyamides as evidenced by XRD. These polyamides had lower glass transition temperatures; as determined by DSC, compared to the T_g of conventional aromatic polyamides due to internal plasticization effect of long alkyl pentadecyl group. Polymers showed good thermal stability, with initial decomposition temperature above 300?°C.     

一种基于多壁碳纳米管的高灵敏捕获水样中细菌的纳米富集钓竿装置

碳纳米管因其独特的性质在生物检测方面具有广泛应用.本文基于DNA与多壁碳纳米管的相互作用而制成了作为一种新型纳米钓竿并用于水样中细菌的富集和检测.该钓竿的制备首先使用戊二醛为连接剂将经硅烷化处理的方形石英毛细管与氨基修饰的DNA相连,再依据单链DNA能缠绕多壁碳纳米管的性质将多壁碳纳米管固载在石英毛细管上制成一个纳米富集的钓竿装置.由于多壁碳纳米管与细菌细胞膜有较强的天然亲和力,因而能主动捕获细菌.实验证明,以大肠杆菌为目标检测菌,＂纳米鱼竿＂最短检测时间为15min,检测限为6.25×10CFU/mL,可以对饮用水等进行实时快速的细菌总数限量检测.     

Use of gnotobiotic mice to identify and characterize key microbes responsible for the development of the intestinal immune system

Symbiosis between intestinal microbiota and the host animal plays an important role in the homeostasis of host physiology. Since the first production of germ-free rodents in 1945, it has become increasingly clear that the intestinal immune system and the biochemical characteristics of epithelial cells differ greatly between conventional and germ-free rodents. However, questions remain about the types of microbes involved and the precise mechanism by which these microbes affect the host physiology. Here, we review experiments designed to answer these questions with the use of gnotobiotic mice. We have determined suitable biochemical and immunological markers for monitoring microbial effects in these mice. Using these markers, we have found clear differences in epithelial cell glycolipid biosynthesis and intraepithelial lymphocyte dynamics between germ-free and conventional mice. Furthermore, we have identified a key microbe that activates the mucosal immune system in the small intestine. This indigenous bacteria, called segmented filamentous bacteria, is a key symbiont in the host-microbiota interplay, including Th17 cell-inducing activity.     

锂离子动力电池隔膜的研究及发展现状

锂离子动力电池作为新能源汽车的动力之源受到广泛关注.本文对动力电池的重要组件之一——电池隔膜进行了介绍.围绕提高安全性和能量密度的设计目标,综述了其新材料、新技术的发展及现状.