Protecting enzymes against heat inactivation by temperature-sensitive polymer in confined space

At high temperature, many enzymes are inactivated by aggregations at hydrophobic sites which are exposed on denaturation. Isolating denatured enzymes via hydrophobic interactions with other material is a significant method to prevent enzymes from aggregation. But the temperature-sensitive polymer poly(N-isopropylacrylamide) (PNIPAAm), supposed to protect enzymes spontaneously at high temperatures, can not efficiently complex denatured carbonic anhydrase B (CAB, as a model enzyme) in bulk aqueous solution due to different phase transition speeds. Here, we present a novel method for protecting enzymes against heat inactivation, in which PNIPAAm and CAB are encapsulated in a confined space constructed by reverse microemulsion. At high temperatures, PNIPAAm forms nanoscale aggregates possessing both large specific surface areas and hydrophobic surfaces, and then adsorbs denatured CAB via hydrophobic interactions to avoid intermolecular aggregation of CAB. With cooling, CAB is released spontaneously and recovers its activity. The assays for enzymatic activity demonstrate that CAB is effectively protected against heat inactivation through this method (protection efficiency is up to 83.2%).     

Characteristics and kinetics analysis of Codonopsis pilosula pyrolysis

Eight kinds of Radix Codonopsis (RC) from different origins in China were selected as the experimental samples fort his study. Their pyrolysis processes were researched by the method of thermogravimetry analysis, in which the heating course was set in the ways of programming temperature from room temperature to 500 °C at different heating rates. Research results show that the process in the heating period of RC includes three stages: water loss, fast pyrolysis, and medium rate decomposition. For cultivated RC, the average initial decomposition temperature in the fast pyrolysis stage is 115 °C, whereas the peak temperature of the fast pyrolysis stage is changed from 189 to 225 °C, in which stage the alcohol-soluble substances are mainly decomposed. It is required to control the operational temperatures of drying and concocting processes according to initial decomposition temperature. Kissinger–Akahira–Sunose model can be used to describe the process mechanism of RC pyrolysis, and the kinetic analyses based on the fast pyrolysis stage thermogravimetric data show that the activation energies change from 141 to 207 kJ mol^?1 for cultivated RC samples and 122 to 131 kJ mol^?1for wild RC samples. The alcohol-soluble extract (ASE) content of wild RC samples is lower than that of cultivated RC samples; their thermal stability is also relatively poor.     

χ3+χ5介质中非束缚态空间亮孤子的传输行为

本文从理论上研究了主克尔型介质中非束缚态空间亮孤子的传输行为。数值计算结果表明:在主克尔型χ⁽³⁾+χ⁽⁵⁾介质中可以传输非束缚态空间亮孤子。传输稳定性与其背景平面波的横向渐近传播常数q和χ⁽³⁾,χ⁽⁵⁾系数有关,非平凡相位因子在三、五阶效应竞争中的平衡作用,是获得非束缚态空间亮孤子稳定传输的关键。     

同科电子L－S耦合原子态的确定

给出一种确定同科电子Ｌ－Ｓ耦合原子态的简便方法，同时指出如果两个同科电子组态的电子数之和等于该支壳层上的电子数，那么这两个同科电子组态具有相同的原子态．     

Observation of all-optical wavelength conversion based on cascaded effect in periodically poled lithium niobate waveguide

We experimentally demonstrate multi-channel wavelength conversion through the cascaded second-order nonlinear processes in periodically poled lithium niobate waveguide in the optical communication wavelength band of 1.5 μm. The normalized conversion efficiency as high as 90% W⁻¹ cm⁻² is obtained. Wavelength conversion over a broad wavelength range of 66 nm has been confirmed.     

对称推挽型有机聚合物电光波导调制器

提出了在极化有机聚合物民光波导调制器中使用局域极化结构。利用该结构，能够在电光调制器中实现完全对称的推挽操作。由于将集成光学电光调制器中用的平面电有改为使用眄结构的微带电极，并且将槽一结构用于接地电极，使器件性能发生变化。文中地反映光波与微波的相互作用强度的重叠积分进行了详细计算，并对器件性能的改变进行了比较。结果表明由于局域极化结构的使用，将大大提高器件的调制性能。     

Photochromic kinetic spectra and intermediates of BR-D96N

BR-D96N is a kind of genetically site-specific mutant of bacteriorhodopsin (BR) with obvious photochromic effect. Compared to the wild type BR, the lifetime of M state of BR-D96N is prolonged to several minutes so that the photochromic kinetics and the intermediates formation can be studied by the conventional spectra analysis. In the experiment, the absorption spectra of the sample at different time after light illumination are measured with spectrophotometer. By fitting and analyzing the variation of the spectra, we suppose there are three main states in the photochromic process, i.e. B state (light-adapted state), M state and D state (dark-adapted state). The absorption spectra of the B state, M state and D state are extracted from the experimental data based on this three-state model and the spectra at various time are fitted with the least square method. So, the variations of population percentages of the M state, B state and D state are obtained and the M state and B state lifetimes are estimated. In another way, from measuring the absorption dynamics at 407 nm and 568 nm, the M state and B state lifetimes are also obtained by two exponential data fitting, which give coincident results with those of the spectra analysis.     

A Highly Sensitive Electrochemical Immunosensor for Fumonisin B1 Detection in Corn Using Single‐Walled Carbon Nanotubes/Chitosan

A sensitive electrochemical immunosensor was developed for detecting fumonisin B₁ (FB₁) in corn using the single‐walled carbon nanotubes/chitosan. The detection mechanism of immunosensor was based on an indirect competitive binding to a fixed amount of anti‐FB₁ between free FB₁ and FB₁‐bovine serum albumin, which was conjugated on covalently functionalized nanotubes/chitosan laid on the glass carbon electrode. The anti‐rabbit immunoglobulin G secondary antibody labeled with alkaline phosphatase was then bound to the electrode surface through reactisubstrate α‐naphthyl phosphate, which produced electrochemical signal. Under optimized conditions, this method could detect FB₁ from 0.01 to 1000 ng mL^?1 with a detection limit of 2 pg mL^?1. This is well below the detection limit required from European Union legislation, 2–4 mg L^?1. Moreover, good recoveries were obtained for the detection of spiked corn samples and actual corn samples. As the method has good sensitivity and recovery for detecting FB₁, it is a practical detection method.     

Synthesis of a novel series of polymerizable surfactants and application in emulsion polymerization

A series of polymerization surfactants (surfmers) was synthesized, whose structures combined the characteristics of polyoxyethylene as nonionic group and quaternary ammonium a as cationic group. The structures of the product were confirmed by MS, and the content of cationic‐activity matter was determined by two‐phase titration. The surfmers were then used with constant addition profiles in semicontinuous polymerization of vinyl acetate–butyl acrylate–Veova 10–hexafluorobutyl methacrylate, and the polydispersity indexes (PDI) were lower than 0.1. The particle size, amount of coagulum, and stability against electrolyte and freeze/thaw were evaluated. As a reference, an unreactive surfactant cetyl trimethyl ammonium bromide (CTAB) was also used for the polymerization. Compared to CTAB, the surfmers behaved much better. Not only stabilities to electrolyte and water resistance were improved, but also freeze/thaw stability got a superior performance. Copyright © 2008 John Wiley & Sons, Ltd.