罗丹明S酶催化光度法测定过氧化氢

在pH 4.4的HAc-NaAc介质中,以辣根过氧化物酶(HRP)催化H2O2氧化KI生成I2,过量的I-与I2结合形成I3-,而I3-与罗丹明S(RhS)反应形成RhS-I3缔合微粒,该微粒导致体系在526 nm处的吸收值线性降低,据此建立了检测H2O2的分光光度分析新方法。研究了pH值,HRP,KI及RhS用量等因素对体系的影响,并对水中Cu2+,Zn2+,Ca2+,Fe3+,Mg2+,Al3+等常见离子进行了干扰试验。在最佳实验条件下,H2O2的浓度在36.72~734.4μg/L范围内与吸光度降低值呈良好的线性关系,相关系数为0.9917。方法的检出限为10μg/L。该法用于测定废水中过氧化氢,结果与纳米金光度法的结果相一致。     

Direct reduction process using fines and with reduced CO2 emission

Abstract

A direct reduction process for refractory oxides and a life cycle analysis comparison with conventional pelletising and sintering process for chargechrome are presented. The new route has potential to reduce the environmental impact of the ferroalloy industry and to extend the use of nonrenewable resources by utilising waste that is not economically recoverable by conventional technologies; increasing metal recoveries; significantly reducing CO₂ emissions; reducing or eliminating the use of coke; and reducing electricity consumption during smelting.     

Study on percutaneous rate of P-aminobenzoates using molecular orbital method

The use of a dome osteotomy in the treatment of infantile tibia vara is reportedly associated with insufficient intraoperative assessment of the correction achieved. This article discusses a method to overcome this problem and the long-term advantages of using a dome osteotomy in the treatment of this disease.     

Ab initio phase determination and phase extension using non-crystallographic symmetry

Non-crystallographic symmetry (NCS) can be used to improve, extend or find ab initio phases to be associated with a set of observed structure amplitudes, resulting in an interpretable electron-density map. The simplest application is merely to improve the accuracy of the phases by cyclically averaging the electron density, Fourier back-transformation of the modified map, and recomputing a new map with the newly found phases. The first sophistication of this procedure is to phase extend, in successive small steps, the currently available phase information to higher resolution, where only observed amplitudes were previously available. A further sophistication is to initiate the phase extension from very low resolution where a simple geometric model, or an electron microscope image, would be consistent with the chosen resolution. A number of recent examples of virus structure determination exist where such ab initio phasing was successful. The ultimate ab initio phase determination would be to extend phases given only an estimate of the F(000) term.     

火焰原子发射光谱法直接测定钠盐表面活性剂中钠

在加热下用硝酸(1+1)-OP溶液溶解钠盐表面活性剂样品,配制成均匀透明的样品溶液。为消除电离干扰,取适量样品溶液加入消电离剂硝酸钾溶液配制成试液,喷入空气-乙炔火焰测定钠,建立了火焰原子发射光谱法直接测定钠盐表面活性剂中钠的分析方法。以空白溶液为参比,用工作曲线法测定。对样品溶解条件、电离干扰、试液与空白溶液粘度一致性进行了考察。测定结果的相对标准偏差小于2.4%,加标回收率97.8%~105.0%,线性范围0~1.6μg/mL,方法简便。     

Investigation of the solution structure of chymotrypsin inhibitor 2 using molecular dynamics: comparison to x-ray crystallographic and NMR data

The native solution structure and dynamics of chymotrypsin inhibitor 2 (CI2) have been studied using a long (5.3 ns) molecular dynamics (MD) simulation without any imposed restraints. The majority of the experimentally observed spin-spin coupling constants, short- and long-range nuclear Overhauser effect (NOE) cross peaks and the amide hydrogen exchange behavior were reproduced by the MD simulation. This good correspondence suggests that the major structural features of the protein during the simulation are representative of the true protein structure in solution. Two water molecules formed hydrogen bond bridges between beta2 and beta3, in agreement with X-ray crystallographic data and a recent reassessment of the solution structure using time-averaged NMR restraints during MD refinement. The active-site loop of the protein displayed the greatest structural changes and the highest mobility. When this loop region was excluded, the average Calpha r.m.s. deviation of the simulated solution structures from the crystal structure was approximately 1.5 Angstrom from 0.5 to 5.3 ns. There is structural heterogeneity in particular regions of the NMR-derived solution structures, which could be a result of imprecision or true internal motion. A study of the distribution of mobility through the protein allows us to distinguish between these two alternatives. In particular, deviations in the active-site loop appear to be a result of heightened mobility, which is also supported by good correspondence between calculated and experimental S2 N-H order parameters. On the other hand, other ill-defined regions of the NMR-derived structures are well defined in the simulation and are probably the result of a lack of structural restraints (i.e. NOEs), as opposed to reflecting the true mobility.