The Effect of Potassium Citrate on Simultaneous Growth of Calcium Oxalate Mono-, Di-, and Trihydrate in Synthetic Urine

Kidney stone disease, which occurs in about 10% of the U.S. population, causes substantial suffering and occasional renal failure, yet the disease mechanism is poorly understood1. Kidney stones mostly contain microcrystals of calcium oxalate monohydrate (…     

Mixed micelles of polyethylene glycol (23) lauryl ether with ionic surfactants studied by proton 1D and 2D NMR

(1)H NMR chemical shift, spin-lattice relaxation time, spin-spin relaxation time, self-diffusion coefficient, and two-dimensional nuclear Overhauser enhancement (2D NOESY) measurements have been used to study the nonionic-ionic surfactant mixed micelles. Cetyl trimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) were used as the ionic surfactants and polyethylene glycol (23) lauryl ether (Brij-35) as the nonionic surfactant. The two systems are both with varying molar ratios of CTAB/Brij-35 (C/B) and SDS/Brij-35 (S/B) ranging from 0.5 to 2, respectively, at a constant concentration of 6 mM for Brij-35 in aqueous solutions. Results give information about the relative arrangement of the surfactant molecules in the mixed micelles. In the former system, the trimethyl groups attached to the polar heads of the CTAB molecules are located between the first oxy-ethylene groups next to the hydrophobic chains of Brij-35 molecules. These oxy-ethylene groups gradually move outward from the hydrophobic core of the mixed micelle with an increase in C/B in the mixed solution. In contrast to the case of the CTAB/Triton X-100 system, the long flexible hydrophilic poly oxy-ethylene chains, which are in the exterior part of the mixed micelles, remain coiled, but looser, surrounding the hydrophobic core. There is almost no variation in conformation of the hydrophilic chains of Brij-35 molecules in the mixed micelles of the SDS/Brij-35 system as the S/B increases. The hydrophobic chains of both CTAB and SDS are co-aggregated with Brij-35, respectively, in their mixed micellar cores.     

不同结构破乳剂油水界面扩张粘弹性研究

研究了支链破乳剂AE121和直链破乳剂SP169在正癸烷-水界面上的扩张粘弹性质,阐述了两种破乳剂扩张模量随扩张频率和破乳剂浓度的变化规律,考察了两种破乳剂对原油活性组分界面扩张性质的影响,测定了两种破乳剂的水溶液与正癸烷的动态界面张力,并与界面扩张流变性质进行了关联.研究结果表明,两种破乳剂的加入均会大大降低原油活性组分界面膜的扩张模量.较低浓度下直链破乳剂SP169由于吸附能力稍强,降低扩张模量效果较好；而一定浓度以上支链破乳剂AE121由于顶替能力较强,具有一定优势.由于破乳剂本身具有一定的扩张模量,在降低界面扩张模量的效果上,破乳剂的用量并非越大越好.     

Influence of carbon dioxide in the determination of oxygen in copper by reduction fusion

It has been reported that copper melted in a graphite crucible at high temperature will give off its oxygen content mainly as CO and partially as CO(2). Thus if oxygen in copper is determined by means of apparatus designed to measure only CO as the reaction product, the results are obviously liable to error. Methods of suppressing formation of CO(2) during the fusion process are proposed. When the oxygen is determined by gas chromatography, formation of CO(2) can be suppressed by adding a 0.5% Si-1.5% NiCu bath-alloy together with the copper sample or by inserting a spectrographically pure carbon rod into the graphite crucible used for the fusion. When the oxygen is determined by coulometry, formation of CO(2) can be suppressed by the addition of the SiNiCu bath-alloy or by appropriate modification of the graphite crucible to obtain an optimum working temperature. The results obtained by either method are in agreement with those obtained by a modified vacuum fusion method in which CO and CO(2) can both be measured. These methods have been validated by analysis of two standard reference materials.     

Development and application of ubiquitin-based chemical probes

Protein ubiquitination regulates almost every process in eukaryotic cells. The study of the many enzymes involved in the ubiquitination system and the development of ubiquitination-associated therapeutics are important areas of current research. Synthetic tools such as ubiquitin-based chemical probes have been making an increasing contribution to deciphering various biochemical components involved in ubiquitin conjugation, recruitment, signaling, and deconjugation. In the present minireview, we summarize the progress of ubiquitin-based chemical probes with an emphasis on their various structures and chemical synthesis. We discuss the utility of the ubiquitin-based chemical probes for discovering and profiling ubiquitin-dependent signaling systems, as well as the monitoring and visualization of ubiquitin-related enzymatic machinery. We also show how the probes can serve to elucidate the molecular mechanism of recognition and catalysis. Collectively, the development and application of ubiquitin-based chemical probes emphasizes the importance and utility of chemical protein synthesis in modern chemical biology.

This article reviews the design, synthesis, and application of different classes of Ub-based chemical probes.     

Specific interaction between Smad1 and CHIP: a surface plasmon resonance study

The TGF-β superfamily signaling pathway regulates many important biological processes, including cell growth, differentiation and embryonic pattern formation. Smad1, a member of this signaling pathway that functions downstream of serine/threonine kinase receptors, has ability to interact with carboxyl terminus of Hsc70-interacting protein (CHIP), which is an E3 ubiquitin ligase in other cases. It has been reported that Smurf1, a member of the Hect family E3 ubiquitin ligases, can target Smad1 to 26S proteasome for degradation. In this paper, we studied the interaction of Smad1 and CHIP by combination of surface plasmon resonance and supported monolayer approach. The specific binding of Smad1 to CHIP indicates that the degradation of Smad1 may also be mediated by CHIP, and CHIP may play an essential role in the TGF-β signaling pathway.     

界面张力弛豫法研究不同结构破乳剂油水界面扩张粘弹性

采用界面张力弛豫法研究了支链破乳剂AE121和直链破乳剂SP169在正癸烷-水界面上的扩张粘弹性质，并与小幅周期振荡法获得的结果进行了比较.阐述了两种破乳剂的扩张模量随扩张频率和破乳剂浓度的变化规律.研究发现，在低频率处，两种破乳剂的扩张模量均接近于零；在中间频率范围内，扩张模量随扩张频率的增加而增大；在高频率处，扩张模量的幅度接近于极限扩张弹性.在中间频率范围内，扩张模量随破乳剂浓度增大，在接近临界胶束浓度处出现一个极大值；同时还发现，界面上和界面附近的微观弛豫过程的数目随破乳剂浓度增加而增大，其贡献也呈规律性变化.     

Oxazaborolidines as functional monomers: ketone reduction using polymer-supported Corey,Bakshi, and Shibata catalysts

The first two polymer-supported versions of the Corey, Bakshi, and Shibata (CBS) catalyst have been prepared. Functional monomers based structurally upon the original B-methylated catalyst have been used to prepare catalytic polymers containing the CBS moiety bound both in a pendant fashion and in the form of a cross-link. Enantioselective reductions of two prochiral ketones have been carried out using the original catalyst in the solution phase as well as the two solid-state systems. While the pendant-bound system shows reduced stereoselectivity, the cross-linked version affords enantioselectivities almost identical to those of the solution-phase model.     

彩色套药生产流程中S_2O_3~(2-)、SO_3~(2-)在线分析法研究

提出了一种S_2O_3~(2-)和SO_3~(2-)生产流程在线分析方法,方法简便,连续采样、连续测定、浓度范围250～550 g/L,响应时间98 s,1.5 h漂移<0.15。     

CaO-MgO-Fe2O3-Al2O3-SiO2玻璃晶化机理

玻璃晶化动力学对于理解玻璃的稳定性和制备微晶玻璃十分重要．目前，通过DTA或DSC等简单技术去研究非等温过程和等温过程的动力学已取得一定的进展[1]．这些方法虽然方便，但需要事先知道晶化机理或借助XRD等技术确定Avrami参数[2]才能得到活化能．根据动力学理论，晶体生长速度与晶体生长活化能尽有直接关系[3]，通过理论计算晶体生长速度（U）可以确定玻璃体系的活化能，再结合DTA技术和Kissinger修正方程就可能确定晶体生长机理，这方面研究还未见报导．CaO－MgO－Fe2O3－AI2O3－SiO2（CMFAS）是本文综合利用废渣和尾矿制…