The potential of mass spectrometry to study iron-containing proteins used in clinical diagnosis

Many proteins contain iron as metal ion either within their own structures or bound to their active sites. These iron-containing proteins are involved in numerous biological processes and some of them serve as biomarkers of clinical pathologies, not only related to iron homeostasis but also to other physiological disorders. Thus, a variety of analytical strategies have been developed over the last years in order to conduct studies on Fe-containing proteins. Among them, mass spectrometric (MS) methods still remain as preferred tools since they provide the capabilities of structure elucidation together with quantitative possibilities. Therefore, in this work we have tried to summarize the most recent applications of elemental and molecular mass spectrometric-based methods for the characterization (mostly qualitative but quantitative in some cases) of the high abundant Fe-containing proteins used for clinical diagnosis.     

A procedure to design the mainline system in natural gas networks

With the start up of West–East Natural Gas Transmission Project, the construction of natural gas-pipeline will enter on a new era in China. The development tendency will be towards large-diameter, high-pressure and long-distance for natural gas-pipelines. Correspondingly, the life cycle cost of natural gas-pipeline networks is increasing gradually. The mainline system is a vital part of natural gas network systems. The investment required for the mainline system is enormous, usually accounting for 80% of the total investment for this system. In general, the investment required for a gas-pipeline depends on its operating parameters. Therefore, based on the characteristics of gas networks, optimization for investment becomes indispensable to gas networks design. A comprehensive and optimal mathematic model of a gas networks system is established in this paper which considers all the factors influencing the total investment of a gas networks system (e.g. pipe diameter, thickness, pressure, length, compression ratio, etc). From the standpoint of the characteristics of a model comprising both continuous and discrete variables, a new methodology, rank-optimization, is presented. On the basis of this model, a simple and visual high-pressure networks optimization program has been compiled. Furthermore, the developed optimization program has been applied to a practical project and the effects of operating parameters on the total investment have been analyzed. The simulation model in this paper is shown to be an effective method to solve optimization on mainline system in high-pressure gas networks.     

An investigation of thermodynamic states during high-pressure fuel injection using equilibrium thermodynamics

A numerical investigation of mixing processes between an injected fuel (an n-alkane) and a chamber inert gas (nitrogen) was carried out for high-pressure fuel injection. The objective is to determine conditions for the coexistence of both liquid and gas phases under the typical ambient conditions encountered in diesel engines. A phenomenological investigation was built by coupling phase stability analysis with the energy conservation equation. Phase changes (including separation and combination) are predicted to occur so as to yield the lowest Gibbs free energy. It is also shown that predicted states without considering phase transitions can be very different from the corresponding thermodynamically correct states. By comparing four n-alkane/nitrogen mixtures it is shown that the lower limit of the two-phase region occurs at similar temperatures. However, heavy n-alkane/nitrogen mixtures have a larger upper limit, and phase separation occurs at higher temperatures. The present model predicts the existence of multiple phases locally in the dense spray jet under high temperature and pressure ambient conditions due to the significant reduction of the mixture temperature caused by vaporization and cooling.     

聚甲基乙烯基醚的局部构象

采用低能构象方法和构象扫描方法,在Dreiding力场下,对含有3种不同侧基取向的PVME的全同二单元体和间同二单元体进行全松弛优化.通过统计平均得到PVME各种构象状态的几何参数和构象能.由统计平均的结果确立了包含侧基所有可能取向信息的PVME链的RIS模型,并利用MontCarlo方法计算了PVME链的特征比,结合实验数据讨论了侧基取向行为的影响.     

In situ XPS study of Pd(1 1 1) oxidation at elevated pressure, Part 2: Palladium oxidation in the 10 mbar range

The oxidation of the Pd(1 1 1) surface was studied by in situ XPS during heating and cooling in 0.4 mbar O₂. The in situ XPS data were complemented by ex situ TPD results. A number of oxygen species and oxidation states of palladium were observed in situ and ex situ. At 430 K, the Pd(1 1 1) surface was covered by a 2D oxide and by a supersaturated O_ads layer. The supersaturated O_ads layer transforms into the Pd₅O₄ phase upon heating and disappears completely at approximately 470 K. Simultaneously, small clusters of PdO, PdO seeds, are formed. Above 655 K, the bulk PdO phase appears and this phase decomposes completely at 815 K. Decomposition of the bulk oxide is followed by oxygen dissolution in the near-surface region and in the bulk. The oxygen species dissolved in the bulk is more favoured at high temperatures because oxygen cannot accumulate in the near-surface region and diffusion shifts the equilibrium towards the bulk species. The saturation of the bulk “reservoir” with oxygen leads to increasing the uptake of the near-surface region species. Surprisingly, the bulk PdO phase does not form during cooling in 0.4 mbar O₂, but the Pd₅O₄ phase appears below 745 K. This is proposed to be due to a kinetic limitation of PdO formation because at high temperature the rate of PdO seed formation is compatible with the rate of decomposition.     

Glucuronide conjugation of phenols in isolated rabbit hepatocytes measured by high-pressure liquid chromatography

Summary High-pressure liquid chromatography has been applied for the assay of reactants of UDP-glucuronyltransferase from isolated hepatocytes with different phenols. The substrate donor molecule UDP-glucuronic acid, its primary product of hydrolysis UMP, the products of glucuronidation -glucuronide and UDP, and the substrate can be assayed in a single run. The method is based on ion-pair chromatography and may be extended for the study of various pathways in the biotransformation of drugs and other endogenous and exogenous phenolic toxins.     

高气压CO2激光器宽带输出频谱特性的理论研究

从理论上研究了高气压CO2激光器的宽带输出频谱特性.结果表明,在20个大气压下,CO2激光器有宽带输出,带宽高达5.0 cm-1(相当于150 GHz),从971 cm-1~976 cm-1,峰值在10R(16)线处,10R(14)线和10R(18)线差不多对称地分布其两侧.很小的增益差异(4.6%)造成了很大的能量输出差异(100多倍).比较了谐振腔内有无色散元件时的输出频谱,理论证明了谐振腔内无任何色散元件时的宽带输出频谱是光滑连续的,而频率依赖的反馈引起了输出频谱很强的精细结构.理论计算结果与实验测量结果符合较好.     

Screening methodology for coal-derived organic contaminants in water

A screening methodology designed to detect the presence of organic materials that leach into water from coal deposits was developed and evaluated. Analytical objectives included the ability to detect 16 polynuclear aromatic hydrocarbons (PAHs) at the lowest practical levels, capability for fingerprint analysis of other compounds, and ease of use under remote field conditions. The approach developed involved drawing 1?L water samples through a styrene divinylbenzene-based solid-phase extraction cartridge by suction, elution of the cartridge with tetrahydrofuran/hexane, evaporative concentration of the eluent, and reconstitution in acetonitrile, followed by analysis using high-pressure liquid chromatography with ultraviolet absorption and fluorescence detectors. The method was found to be easy to use under field conditions, providing generally acceptable recoveries and, in most cases, lower detection limits than current regulatory methods. The ability to detect PAHs and other organic compounds in simulated coal leachate solutions was demonstrated.     

高压覆膜制样X射线荧光光谱法测定土壤和水系沉积物中的氯研究

氯是化探样品分析中的重要元素,而X射线荧光光谱法是测定卤族元素的重要技术手段。已有研究表明,X射线荧光光谱法在测定氯时,同一样片中氯的测定值随重复测定次数的增加而逐渐增大或减小。采用高压覆膜制样技术制片,测定土壤和水系沉积物中的氯,氯（24～40 000 μg·g-1）校准曲线的相关系数明显改善,RMS（均方根）由未贴膜的0.009 63,改善为贴膜后的RMS 0.001 98。氯的检出限由未贴膜的30 μg·g-1,改善为贴膜后的21 μg·g-1。且高压覆膜制样,同一样片连续测定10次,还是10 d内隔天测定1次,氯的测定值都保持不变或略有下降。从抽真空时间,X光管应用功率,烘样和不烘样,氯元素存在形式等角度解释了氯的测定值随重复测定次数的增加而逐渐增大或略减小的原因。高压覆膜制样,样品表面的聚酯膜,可以阻止在抽真空过程中氯随水分向样片表面迁移扩散或分解损失。高压未覆膜的样片在测定过程中,因样片表面吸附了水及空气分子,因而随抽真空时间的增加及解吸附作用,真空度下降明显,氯的强度变化明显。而高压覆膜样片在测定过程中,真空度下降不明显,氯的测定值基本不变或略有下降。高压制样（1 600 kN）可以将不同类型的地质样品压制成型,高压覆膜制样技术,完全消除了粉尘效应,对下照射的X射线荧光光谱仪具有重要意义。测过的样片可以重复测定氯,标准样片可长期保存,避免了标准样品的浪费。用该方法可以准确测定土壤和水系沉积物中32个组分。该样品制备方法也适用于测定其他难以成型的样品及其荧光强度由于真空和长时间辐射而强度变化的元素分析。