Activation entropy of electron transfer reactions

We report microscopic calculations of free energies and entropies for intramolecular electron transfer reactions. The calculation algorithm combines the atomistic geometry and charge distribution of a molecular solute obtained from quantum calculations with the microscopic polarization response of a polar solvent expressed in terms of its polarization structure factors. The procedure is tested on a donor–acceptor complex in which ruthenium donor and cobalt acceptor sites are linked by a four-proline polypeptide. The reorganization energies and reaction energy gaps are calculated as a function of temperature by using structure factors obtained from our analytical procedure and from computer simulations. Good agreement between two procedures and with direct computer simulations of the reorganization energy is achieved. The microscopic algorithm is compared to the dielectric continuum calculations. We found that the strong dependence of the reorganization energy on the solvent refractive index predicted by continuum models is not supported by the microscopic theory. Also, the reorganization and overall solvation entropies are substantially larger in the microscopic theory compared to continuum models.     

8－羟基喹啉纤维微柱分离富集ICP－AES测定多种痕量元素

制备了８－羟基喹啉纤维滤纸片，作为微柱填充物，同时富集了九种痕量元素，并分离了样品中的高盐组分。富集后的痕量组分采用电感耦合等离子体原子发射光谱法（ＩＣＰ－ＡＥＳ）测定，回收率为９０％～１０２％。     

Sample-induced internal pH gradients in microcolumn liquid chromatography of proteins

Summary The technique of an internal pH gradient induced by the sample is applied to the separation of proteins by liquid chromatography. Compatibility of the method with microcolumns is demonstrated and examples of separations on different types of sorbents are given.     

离子交换法从发酵液中提取谷氨酰胺工艺研究

本文系统地研究了７３２树脂和Ｄ３０１树脂对发酵液中谷氨酰胺的静态和动态吸附性能及影响因素，并对洗脱条件进行了研究。实验结果表明，在阳离子交换柱上有效地降低了谷氨酰胺向谷氨酸的转化，在阴离子交换柱上谷氨酰胺和谷氨酸实现彻底分离，谷氨酰胺的总收率达５６．６％。     

Relative retention of the fibroblast growth factors FGF-1 and FGF-2 on strong cation-exchange sorbents

The isocratic retention of two heparin-binding fibroblast growth factors, FGF-1 (acidic FGF) and FGF-2 (basic FGF), was compared on a set of six preparative strong cation-exchange adsorbents. The FGFs comprise a solute pair that are structurally equivalent, yet differ in protein parameters of potential importance in cation-exchange chromatography, such as isoelectric point, net charge, and the number and distribution of basic amino acids. The cation-exchange adsorbents comprise a diverse set of materials in common use for protein purification, with physical and chemical properties that have been characterized and described previously. Isocratic k' values for the two proteins obtained on each adsorbent at several different [NaCl] are compared with one another and with corresponding data for hen egg lysozyme, which is also strongly retained on cation-exchangers. Of the six adsorbents examined, three showed strong retention of both FGFs, with equivalent k' values for FGF-1 and FGF-2. Three others, which showed weaker overall retention for the FGF pair, showed much larger retention differences between FGF-1 and FGF-2. The trends in retention order among the stationary phases are very similar to those seen previously with other unrelated proteins. However, retention differences between the two FGFs, and between the FGFs and lysozyme, do not correlate well with simple charge properties such as net charge, indicating, as in some previous studies, the importance of local regions on the protein surface in determining retention. These observations are interpreted in terms of the structural features of the proteins and the physicochemical properties of the adsorbents.     

HPLC separation of hydrogenated derivatives of buckminsterfullerene

Summary The effect of composition and flow rate of the mobile phase on the HPLC separation of hydrogenated buckminsterfullerene (C₆₀H_n n=2–38) was investigated on BuckySep column. Toluene was used as the basic solvent and hexane, heptane, cyclohexane, THF, acetonitrile, acetone, ethanol and 2-propanol as co-solvents. The fraction of co-solvents was varied 10–80%, and the flow rate 1–0.1 mL min⁻¹. Toluene-acetonitrile 65∶35 and toluene-acetone 50∶50 provided the best separation. Under the best conditions complete separation of C₆₀H₂ and almost complete separation of the four most abundant isomers of C₆₀H₄ were achieved. Separation of derivatives with higher hydrogen content was very poor. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997     

Capillary gas chromatographic separation of C10–C12 secondary phenylalkanes on modified cyclodextrin stationary phases

The separation of isomers and enantiomers of branched C₁₀-C₁₂ phenylalkanes by gas chromatography on fused silica capillary columns coated with some modified β- and γ-cyclodextrins was studied. It was shown that the separation of positional isomers of C₁₀-C₁₂ phynylalkanes on modified cyclodextrin capillary columns is not better than that on a column coated with modified polyethylene glycol. Differences were found in the enantioselectivity of modified β- and γ-cyclodextrins for the separation of C₁₀-C₁₂ secondary phenylalkane enantiomers. While alkylderivatives of β-CDs resolve enantiomers of 3-phenylalkanes, alkyl derivatives of γ-CD resolve enantiomers of 2-phenylalkanes. Since shape selectivity factors of modified cyclodextrins have indicated no inclusion of the considered solutes in cyclodextrin cavities, enantioselective interactions most probably occur on the outer sphere of cyclodextrins.     

Determination of weight distribution ratios of Pa(V) and Np(V) with some extraction chromatography resins and the AG1-X8 resin

Literature data on distribution ratios (D_w) of Np(V) and Pa(V) for the AG1-X8 resin are scarce whereas those related on resin capacity factors (k′) values for TEVA, TRU and U/TEVA resins are absent. Therefore, batch extraction experiments for Pa(V) and Np(V) from HCl and HNO₃ media were realized, at tracer scale, with AG1-X8 and EIChroM resins (TEVA, TRU and U/TEVA). Based on the new D_w and k′ values obtained in this study, a new protocol for Pa/Np separation has been developed leading to a better separation factor of 10⁵ and a chemical yield of 97 ± 3% and 99 ± 1% for Pa and Np, respectively. A separation of ²³¹Pa from uranium matrix was successfully tested.     

用于考察外源添加剂对卷烟常规烟气指标影响的样品制备因子筛选

为筛选用于考察外源添加剂对卷烟常规烟气指标影响的样品制备关键控制因子,采用L_8(2~7)正交试验设计进行香兰素及乙基麦芽酚的添加实验.卷烟常规烟气指标变化数值通过极差分析、方差分析,结果显示:参比卷烟种类是影响卷烟烟气总粒相物、焦油、水分的高度显著因子,就试验采用的1R5F和3R4F参比卷烟而言,添加剂在高焦油3R4F卷烟中对常规烟气指标的影响比其在低焦油1R5F卷烟中的影响大;添加剂种类与浓度的交互作用不仅对卷烟烟气总粒相物有高度显著影响,而且对总粒相物中的水分也有显著影响;因此,规范样品制备,可减少误差、保证后续外源添加剂加入对卷烟常规烟气指标影响评价结果和推断的可靠性及科学性.     

Determination of gadolinium-based MRI contrast agents in biological and environmental samples: A review

The development of analytical methods and strategies to determine gadolinium and its complexes in biological and environmental matrices is evaluated in this review.