Ionic Liquids as Mobile Phase Additives for Separation of Nucleotides in High-Performance Liquid Chromatography

Ionic liquids are a type of salts that are liquid at low temperature (＜100℃). Because of their some special properties, they have been widely used as new “green solvents” for many chemical reactions and liquid-liquid extraction in the past several years. In this paper, a new method for the separation of nucleotides is developed and the essential feature of the method is that 1-alkyl-3-methylimidazolium salts are used as mobile phase additives, resulting in a baseline separation of nucleotides without need of gradient elution and need of organic solvent addition as currently used in RP-HPLC. This study shows the potential application of ionic liquids as mobile phase additives in reversed-phase liquid chromatograohy.     

HEAT FLOW ON THE QINGHAI-XIZANG(TIBETAN) PLATEAU AND THE MODELING OF THE TECTONO-THERMAL EVOLUTION

Thirteen observed heat flow values in combination with relevant geological and geophysical information are employed in the current paper to conduct a model study by means of direct inversion. The modeling demonstrates the tectono-thermal evolution of the Tibetan Plateau during the last 40 Ma since the continent-continent collision. The authors stress the fact that the tectonic deformations of terranes are usually the inducing factors for the deep-seated thermal activities in the crust and upper mantle. On this basis a series of kinematic equations of 3-D deformations of terranes in forms of shortening-thickening-uplifting-erosion-mass sliding were deduced using the principle of plate kinematics. These equations are further used as systematically defined initial and boundary conditions for simulating the integrated processes of tectono-thermal evolution, The results of the model study suggest that there exist sharp differences in the tectono-thermal evolution between the old northern terranes and the new     

气相色谱分析中是否一定要用质谱检测器？

The detector, as well as being an essential supporting device for the gas chromatography (GC) has also played a critical role in the development of the technique as a whole. The mass spectrometer (MS) is still the commonly praised detector as before. In fact, the information of fragmentation patterns is seldom used in practice, and the GC-MS instrument is even more expensive. For today’s analytical problems, it seems that element specific detectors can and should be used for many applications rather than GC-MS.     

Molecular Simulations using Spherical Harmonics

Computer-aided drug design is to develop a chemical that binds to a target macromolecule known to play a key role in a disease state. In recognition of ligands by their protein receptors, molecular surfaces are often used because they represent the in-teracting part of molecules and they should reflex the comple-mentarity between ligand and receptor. However, assessing the surface complementarity by searching all relative position of two surfaces is often computationally expensive. The comple-mentarity of lobe-hole is very important in protein-ligand inter-actions. Spherical harmonic models based on expansions of spherical harmonic functions were used as a f‘mgerprint to ap-proximate the binding cavity and the ligand, respectively. This defines a new way to identify the complementarity between lobes and holes. The advantage of this method is that two spherical harmonic surfaces to be compared can be defined sep-arately. This method can be used as a filter to eliminate candi-dates among a large number of conformations, and it will speed up the docking procedure. Therefore, it is possible to select complementary ligands or complementary conformations of a ligand and the macromolecules, by comparing their fingerprints previously stored in a database.     

A STOICHIOMETRIC DISPLACEMENT MODEL OF SOLUTE ADSORPTION IN LIQUID-SOLID SYSTEM

Based on five thermodynamic equilibria involving solutes, solvents and adsorbents, a stoichiometric displacement adsorption model adaptable to various adsorption systems consisting of different types of solutes, solvents and adsorbents has been presented. The kernel of this model is that as the solute molecules are adsorbed by the adsorbent, a stoichiometric number of the solvent molecules is necessarily released. The model was tested with originally published data from an extensive literature. The linear parameter values from the model have been used for quantitatively explaining the phenomenon of the liquid-solid adsorption. Having compared with Langmuir model in many respects, it is found that this model is better.     

Transfer Hydrogenation of C= C Double Bonds Catalyzed by Ruthenium Amido-Complexes: Scopes, Limitation and Enantioselectivity

The reduction of C = C double bonds is one of the most fundamental synthetic transformations and plays a key role in the manufacturing of a wide variety of bulk and fine chemicals. Hydrogenation of olefinic substrates can be achieved readily with molecular hydrogen in many cases, but transfer hydrogenation methods using suitable donor molecules such as formic acid or alcohols are receiving increasing attention as possible synthetic alternatives because it requires no special equipment and avoids the handling of potentially hazardous gaseous hydrogen.     

Hydride-Based Separation Materials for High Performance Liquid Chromatography and Open Tubular Capillary Electrochromatography

 Silica hydride is a recent development in chromatographic support materials for high performance liquid chromatography (HPLC) where hydride groups replace 95% of the silanols on the surface. This conversion changes many of the fundamental properties of the material as well as the bonded stationary phases that are the result of further chemical modification of the hydride surface. Some unique chromatographic properties of hydride-based phases are described as well as some general application areas where these bonded materials may be used in preference to or have advantages not available from typical stationary phases. The fabrication, properties and applications of etched chemically modified capillaries for electrophoretic analysis are also reviewed. It is shown that the etching process creates a surface that is fundamentally different than a bare fused silica capillary. The new surface matrix produces unique electroosmotic flow properties and is more compatible with basic and biological compounds. After chemical modification of the surface, the bonded organic moiety (stationary phase) contributes to the control of migration of solutes in the capillary. Both electrophoretic and chromatographic processes take place in the etched chemically modified capillaries leading to a variety of experimental variables that can be used to optimize separations. A number of examples of separations on these capillaries are described.     

三聚氰胺-甲醛加成反应的研究

The addition reaction between melamine and formaldehyde involves the conversion of melamine into nine different methylol melamines.The reaction mechanism of the complex system can be summarized in a simple reaction model as below:(这里有图片19890824-878-1.gif)The rate equations of above reactions are evaluated by using Runge-Kutta method, and the rate constants are determined by means of fitting them to reaction species concentrations at various times.The molecular distribution formula of methylol derivatives of polyamine, which we developed previously, is used to form simultaneous equations with reaction rate equations and the contents of various meth-ylol-melamine are calculated.The results are good in agreement with the experiment data.     

Photocatalysis: an overview of recent developments and technological advancements

Photocatalysis,which is the catalyzation of redox reactions via the use of energy obtained from light sources,is a topic that has garnered a lot of attention in recent years as a means of addressing the environmental and economic issues plaguing society today.Of particular interest are photosynthesis can potentially mimic a variety of vital reactions,many of which hold the key to develop sustainable energy economy.In light of this,many of the technological and procedural advancements that have recently occurred in the field are discussed in this review,namely those linked to:(1)photocatalysts made from metal oxides,nitride,and sulfides;(2)photocatalysis via polymeric carbon nitride(PCN);and(3)general advances and mechanistic insights related to TiO2-based catalysts.The challenges and opportunities that have arisen over the past few years are discussed in detail.Basic concepts and experimental procedures which could be useful for eventually overcoming the problems associated with photocatalysis are presented herein.     

Synthesis of 4-Methyl-2-Isopropyl-1,3-Dioxolane by TiSiW_(12)O_(40)/TiO_2 as Catalyst

Acetals and ketals are a kind of the important compounds and used to protect carbonyl, middle material of the organic synthesis. What’s more, they are a sort of the widely use flavor substance. 4-Methyl-2-isopropyl-1,3-dioxolane has fresh fruit odor and apple note. It is used to producing many sorts of essence. And the conventional method to synthesize 4-methyl-2-isopropyl-1,3-dioxolane makes use of sulfuric acid as catalyst in factories. But it causes many problems, such as the erosion of p…     

Fullerenes for rechargeable battery applications:Recent developments and future perspectives

The development of high-performance batteries is inseparable from the exploration of new materials.Among them,fullerene C60 as an allotrope of carbon has many unique properties that are beneficial for battery applications,including precise structure,controllable derivatization,good solubility,and rich redox chemistry.In this review,we summarize the recent progress of fullerene-based materials in the field of rechargeable batteries and the key issues that need to be solved in the future application of fullerene.We hope this review can provide guidance and stimulate research about the applications of fullerenes in the field of energy storage.     

THEORETICAL AND COMPUTATIONAL INVESTIGATIONS OF NONLINEAR WAVE PROPAGATIONS IN ARTERIES (Ⅰ)——A THEORETICAL MODEL OF NONLINEAR PULSE WAVE PROPAGATIONS

In this paper, a new theoretical model of nonlinear wave propagations in arteries with surrounding tissues was put forward. The equations of motion for the blood vessels and their peripheral tissues as a system have been derived. These equations were expressed in terms of the stresses of the vessel wall and fluid, and the geometry of the blood vessel. They can be used to solve numerically the problems for the propagations of nonlinear pulse waves in arteries together with the momentum and continuity equations of incompressible-viscous flow, as well as the constitutive equations of fluid and vessel wall. The numerical solutions can involve pressure, velocities and flowrate of the blood flow, as well as displacements, velocities and stresses of the vessel wall. These physical variables of propagations of pulse waves in arteries are all of significance physiologically and clinically.     

Studies on Thermal Stability and Fluid Property of PVC Filled with Hydrotalcite

IntroductionIt is well known that PVC is a kind of valuableplastic and used in many fields.But PVC isunstable against heat and light,and at the heat-molding step,the thermal decomposition of it maytake place.Finally,the decomposition will reducethe mechanical strength and lose otherproperties ofPVC.In order to overcome those disadvantages,athermal stabilizer is added in the PVC material toreduce the thermal decomposition,and organiccompounds of metals such as Sn,Pb,Ca,Ba,Znand Cd are u…     

NMR STUDY ON THE MAJOR COMPONENTS IN HEMATOPORPHYRIN DERIVATIVE YHPD

The hematoporphyrin derivative YHPD, a China-made product, has been clinically used in photodynamic therapy of tumors as a good photosensitizing drug. The NMR study on the structure of its major components is reported here. In terms of high performance liquid chromatography (HPLC) four major components A, B, C and D were isolated. The NMR results showed that the component A is O-acetylhematoporphyrin, B and C are two isomers of vinyldeuteroporphyrin. The spectra of 2-dimensional homonuclear correlation NMR, 2-dimensional NOE (nuclear overhauser enhancement), ~(13)C-NMR and off-resonance as well as FAB (fast atom bombarding) mass spectrum of component D indicate that it is a protoporphyrin dimer linked by carbon-carbon bond. This finding may providea chemical basis for understanding the difference in biological activity between YHPD and other foreign commercial HPD, as well as the composition of clincally used alkali-treated HPD and its effective component.     

Investigation of Quantitative Relationship between Adsorbed Amount of Solute and Solvent Concentration at Relatively High Solute Con－centration by Frontal Analysis in RPLC

In previous paper a new adsorption isotherm which relates the amount of solute absorbed to the solvent concentration is pro-posed and simplified, and it only can be used at lower solute concentration. In this article the scope of the new adsorption isotherm is extended and the expressions with three and four parameters are obtained. The equations with multi-parameters are valid when the adsorbed mounts are larger and show non-linear logarithmic relationships. Tests with a homologue of are-matic alcohols by frontal analysis in reversed phase liquid chro-matography demonstrate that the experimental results fit those equations well. In addition, the predicted values by the multi-parameters were found to fit the experimental values well also. The parameters have physical meaning only for the two-param-eter equation for the aromatic alcohols.     

Electroreduction of Benzoylformic Acid in 1-Ethyl-3-methylimidazolium Bromide Room Temperature Ionic Liquid

The chemical industry is under considerable pressure to replace many volatile organic compounds that are widely used as solvents in organic synthesis. This trend leads to the exploration for novel reaction media. Room temperature ionic liquids as environmentally benign media for organic synthesis and catalytic reactions have been gradually recognized and accepted Owing to their unique chemical and physical properties, ionic liquids become promising candidates as recyclable reaction media for “ Green” applications. These nonvolatile solvents have been used as media or catalysts in dozens of fields, such as organic synthesis, organometallic catalytic reactions, separation and extraction processes.     

Preparation and Catalytic Activity of SO_4~(2-)/TiO_2-La_2O_3 in Synthesis of Butyl Butyrate

Butyl butyrate is a very important compound, which is transparent liquid and has the pear, apple flavor. Natural exist is in the fruit, such as apple, pear, banana, grape and strawberry, etc. Primarily used for to prepare the edible spice and is also widely used in industrial intermediate product, solvent and synthetic perfumery. Until now, there are many methods to synthesize it. Conventionally H2SO4 was reported, but it causes many problems, such as the erosion of equipment, easily causes …     

Theoretical Chemistry Study of the Hydrogen-bonded Interaction between Acylamine and Chloromethane Compounds

1 INTRODUCTION The mutual interaction of molecules is related with many properties of the material, such as optics, electricity and magnetism. Moreover, chemical re- action and molecule recognition are related to the mutual interaction among molecules too. So, the weak interactions among molecules have attracted many chemists’ attentions. The law of mutual interaction of molecules has been widely used in many research fields, such as, studying the mechanism of organic reaction and de- si…     

LONG-RANGE CORRELATIONS IN DNA SEQUENCES USING TWO-DIMENSIONAL DNA WALKS

The characterization of long-range correlations and fractal properties of DNA sequences has proved to be a difficult though rewarding task mainly due to the mosaic character of DNA consisting of many patches of various lengths with different nucleotide constitutions. In this paper we investigate statistical correlations among different positions in DNA sequences using the two-dimensional DNA walk. The root-mean-square fluctuation F(l) is described by a power law. The autocorrelation function C(l), which is used to measure the linear dependence and periodicity, exists a power law of C(l) -τμ. We also calculate the mean-square distance ＜R2(l)＞ along the DNA chain, and it may be expressed as ＜R2(l)＞ - l r with 2 ＞γ＞ 1. Our investigations can provide some insights into long-range correlations in DNA sequences.     

MEASUREMENT METHOD AND PHYSICAL MODEL OF VSC CONDUCTIVITY AND ITS APPLICATIONS IN CONDUCTING POLYMERS

Method of VSC (Voltage Shorted Compaction)can be used to determine the intrinsic temperature dependence ofconductivity ofpolycrystalline compaction. The experimental conditions and technical key for preparation of VSC device and its physical model as well as its applications in conducting polymers are discussed in detail.