KINETICS OF THE IRREVERSIBLE MODIFICATION OF ENZYME ACTIVITY IN A SYSTEM OF COUPLED ENZYME ASSAY (Ⅰ)——ONLY PRIMARY ENZYME MODIFIED BY REAGENT Y

Kinetic equations are derived for the substrate reaction during simultaneous irreversible modification of enzyme activity for systems using coupled enzyme assay. It has been shown that the method proposed previously by Tsou for determining the irreversible inhibition constants can also be used in the present situation. Moreover, the criteria proposed to distinguish between different inhibition types are also applicable.     

BIOLOGICAL FUNCTIONS OF MODIFIED NUCLEOTIDES IN tRNA MOLECULES (Ⅲ)——SYNTHESIS AND BIOLOGICAL ACTIVITY OF ANALOGS OF YEAST ALANYL tRNA WITH m~1I_(37) REPLACED BY A, G OR C

A thirty-nine nucleotide fragment (nucleotides 38—76) of yeast alanyl tRNA was prepared by using calf spleen phosphodiesterase to delete C_(36)m~1I_(37) from the 3′-half molecule of this tRNA under controlled conditions. Analogs of yeast alanyl tRNA with A, G or C instead of m~1I_(37) were synthesized and their biological activities determined. The results indicated that the aminoacylation activity of these analogs was not affected in the rat liver aminoacyl-tRNA synthetase system, compared with natural yeast alanyl tRNA. However, the incorporation activity (i. e. the activity of transferring alanine into proteins) of these analogs was significantly reduced to 20—30% of that of natural yeast alanyl tRNA in the rabbit reticulocyte lysate cell-free protein synthesizing system.     

γ-PICOLINIUM CHLOROCHROMATE (γ-PCC): A NEW AND EFFICIENT REAGENT FOR THE OXIDATION OF PRIMARY AND SECONDARY ALCOHOLS

The preparation of γ-picolinium chlorochromate as a new and efficient reagent for the oxidation of primary and secondary alcohols to their corresponding carbonyl compounds in dichloromethane at ambient temperature is described.     

STUDIES OF UNUSUAL OXIDATION STATES OF TRANSITION METALS (Ⅰ)——KINETICS AND MECHANISM OF OXIDATION OF POTASSIUM THIOCYANATE BY DIPERIODATOARGENTATE(Ⅲ) ION IN ALKALINE MEDIUM

The kinetics of oxidation of potassium thiocyanate by diperiodatoargentate (Ⅲ) (DPA) ions was studied in aqueous alkaline medium ([OH~-]=7.00×10~(-3)—0.200 mol. dm~(-3)) at a constant ionic strength (μ=0.30 mol. dm~(-3)). It is found that the reaction order in DPA is unity. The dependence of the rate on [OH~-] implies that there are two pathways through which the reaction proceeds. In each pathway, the order in NCS-is fractional and the kinetic data fit well in with Michaelis-Menten process. The influence of ligand on the reaction is examined and the reactive species are inferred. Two pathways of inner-sphere two-electrons transfer are believed to be involved in the oxidation. The rate equations are derived and all the equilibrium constants and rate constants are evaluated. Activation parameters of one pathway are determined.     

SYNTHESIS AND CRYSTAL STRUCTURE OF THE FIRST THREE DIMENSIONAL NETWORK CU(Ⅱ) COMPLEX BRIDGED BY BOTH OXAMIDE AND AZIDE

A novel three dimensional network complex polymer [Cu_4(oxen)_2(N_3)_3]_n(ClO_4)_n·2nH_2O, where oxen is N,N' -bis(2-aminoethyl)oxamide dianion, has been synthesized. It crystallizes in triclinic system, space group P(?), with a=11.486(2), b=11.706(3), c=12.291(3) (?), α=77.42(2), β=67.59(2), γ=77.96(2)°, and z=2. The least-square refinements converged at R=0.047, with 3416 observed unique reflections. The complex has a pronounced three-dimensional character and can be viewed as the tetranuclear asymmetric repeating units through inversion and translation operations to extend a three-dimensional network. The structure of Cu_4 asymmetric unit consists of two square planar and two square pyramidal Cu central atoms linked by both azide ligands in end-on and end-to-end bonding modes, and oxamidate bridge in trans conformation.     

CATALYTIC COPOLYMERIZATION OF STYRENE AND ETHYLENE BY NEUTRAL NICKEL(Ⅱ) COMPLEXES IN EMULSION

Emulsion copolymerization of styrene and ethylene catalyzed by a series of neutral nickel(Ⅱ) complexes was carried out in an aqueous system to give high-molecular-weight copolymers.The copolymers and emulsions were characterized by an array of techniques including NMR,GPC,TEM,WAXD and DSC.The results indicate that the copolymers obtained are mostly block copolymers of polyethylene with random insertion of styrene units,and their M_W is in the range of 10~5-10~6.By enhancing the electron withdrawing of th...     

BIOLOGICAL FUNCTION OF MODIFIED NUCLEOTIDES IN tRNA MOLECULES——SYNTHESIS AND BIOLOGICAL ACTIVITY OF THE ANALOGUES OF YEAST ALANYL tRNA WITH I_(34) REPLACED BY A_(34) OR G_(34)

Analogues of yeast alanyl tRNA with I_(34) replaced by A_(34) or G_(34) were synthesized. Synthetic analoguesof yeast alanyl tRNT occupy the same position as the natural yeast alanyl tRNA on polyacrylamide gelelectrophoresis, and their purity is about 95% after electrophoresis on a 10% or 20% polyacrylamide gel.The two terminal and nearest neighbour nucleotides of the analogues are all correct. The accepting acti-vity of the synthetic analogues is similar to that of the reconstituted natural yeast alanyl tRNA. The in-corporation activity of alanine into proteins of the synthetic analogues is about 30% of that of the naturalof reconstituted natural yeast alanyl tRNA when I_(34) is replaced by A, and is 90% when I_(34) is replaced byG.The reason of the variation in biological function of the analogues of yeast alanyl tRNA after I_(34) re-placed by A or G was discussed.     

TERMINATION AND TRANSFER OF THE CHAIN RADICALS IN THE POLYMERIZATION OF ACRYLONITRILE INITIATED BY VANADIUM(V)-THIOUREA REDOX SYSTEM

The dependence of the molecular weights on the concentration of reactants in the polymerization of acrylonitrile initiated by vanadium (V)-thiourea redox system has been investigated. It was found that the molecular weights of the polymer change nonlinearly with increasing concentrations of nitric acid and thiourea. Probably, the composition of the complexes exert a great influence on the chain initiation and termination. The reaction of "complextermination" gives rise to the decrease of the molecular weights markedly while the concentrations of thiourea and vanadium (V)in the range from one to three molar ratios.     

MICELLAR CATALYSIS-THE KINETICS OF Ni(Ⅱ)AND PYRIDYLAZO DYES COMPLEX FORMATION IN THE PRESENCE OF SODIUM DODECYL SULFATE MICELLES

By means of the Stopped—Flow Spectrophotometry,the kinetics of the reactions betweennickel(Ⅱ)and the ligand 5—bromopyridylazo diethylaminophenol(5-BrPADAP)and 3,5—dibromopyridylazo diethylaminophenol(3,5—2BrPADAP)have been investigated in themicellar solution of sodium dodecyl sulfate(SDS).The reaction rate(compared with thatmeasured in aqueous solution for the same Ni~(2+)concentration)was enhanced up to a factorof 400.Kinetic analysis indicates that the rate enhancement can be explained in terms of theconcentration effect of the micelles on the rcactants(i.e.partitioning coefficient effects).Aquantitative expression for the rate enhancement is derived,using the psudo—phase modeland Berezin’s original micellar-catalysis coneepts.The influenccs of hydrophobic character-istics of ligands on the micellar-catalysis effect have been studied also.     

SYNTHESIS AND STRUCTURE OF A NOVEL INFINITE-LAYER COPPER(Ⅱ)COMPLEX BRIDGED BY OXAMIDE AND PYRIMIDINE

The complex polymer[Cu_2(oxap)(pyr)_2]_n(ClO_4)_(2n),where oxap~(2-)stands for N,N'-bis(2—aminopropyl)oxamide,have been synthesized.It crystallizes in monoclinic system,space group P2_1/C,with a=8.721(2),b=8.679(2),c=16.741(2),β=98.59(0),Z=4.Theleast-square refinement coverged at R=0.054,R_w=0.055 with 1869 unique reflections.Thewhole structure of the complcx consists of layers of two-dimensional network arrayingalong a-axis with perchlorate ions interspersed in the gap between layers.Inside the layer.trans-oxamide-bridged copper(Ⅱ)dimers connected by pyrimidine in an asymmetric fashionspread out along be plane to form an infinite two-dimensional network.     

A NOVEL EOR POLYMER (Ⅱ)——INVESTIGATION ON IN-SITU GELATION OF SMRF SYSTEM IN BEREA CORE

In-situ gelation of aqueous sulfomethylated resorcinol formaldehyde (SMRF) system inBerea core has been investigated. Two sets of displacement experiments were conducted with thissystem (containing 5% NaCl, 0. 036% CaCl_2. 2H_2O). The brine permeabilities of the coreswere reduced significantly from about 600 to 0.1 md. The in-situ gelation in Berea core occurreda little bit earlier than gelation anticipated from bulk test in the experiments. The gel time waseasier to control at initial pH between 6 and 8. During injection of SMRF system, the apparentviscosity was less than 1 mPa·s at 41℃.     

STUDY ON THE MODIFICATION OF ULTRASTABLE Y-TYPE ZEOLITES WITH H_2C_4H_4O_6 IN UNBUFFERED SYSTEM Ⅱ.PREPARATION AND CHARACTERIZATION

探索了非缓冲条件下，用酒石酸对超稳Ｙ型分子筛进一步脱铝改性的可能性。系统地考察了反应时间、反应温度、酒石酸溶液加入量、溶剂加入量、滴加速度及溶液ｐＨ值对处理过程的影响，并对改性后的分子筛样品采用Ｘ射线衍射测试、差热分析等手段进行了结构与性能的表征。结果表明，所用的分子筛脱铝方法在合适的处理条件下能制备出硅铝比达１２左右的超稳Ｙ型分子筛。改性后的超稳Ｙ型分子筛的晶体结构热稳定性随着骨架硅铝比的提高而增加。     

SYNTHESIS OF CONDENSATION POLYMERS OF SALICYLIC ACID, FORMALDEHYDE AND ALKYL PRIMARY AMINES AND ITS APPLICATION AS A CATALYST FOR THE HYDROLYSIS OF p-NITROPHENYL ACETATE (PNPA) IN AQUEOUS SOLUTION

As a model of serine hydrolase, the condensation polymers of salicylic acid, formaldehyde and methyl amine, n-propyl amine, n-hexyl amine or n-lauryl amine were prepared by polycondensation catalyzed by sulfuric acid. It was confirmed by potentiometric titration and infrared spectrum that the polymers containing tertiary amino group possess the structure which resembles the internal salt of amino acid in weak basic and weak acidic solution:     

NUMERICAL SIMULATION OF BENARD CONVECTION IN A CLOSED RECTANGLE (Ⅱ)——THREE-DIMENSIONAL CASE

In the paper, numerical simulation is performed for Benard convection in a closed three-dimensional rectangle with non-slippery bound. Numerical results show that when Rayleigh number Ra<3.6×104, Benard convection is steady, and when Ra≥3.6×104 it is unsteady and irregular. The cross sections and correlation coefficients of various fields are studied, and it is found that the external correlation scales of flow decrease as Ra increases when Ra≥ 7.5×104. Moreover, statistical analyses show that the Taylor inner scales (λv,λθv and so on) also decrease as Ra increases, and that the changing rates of λv and λθv with height are very different to each other in the vicinity of upper and lower bounds. Furthermore, statistical analyses show that the computed Nusselt number Nu is close to the lower limit of many experimental values, and in the transient region of flow pattern d1gNu/d1gRa is relatively greater than that in other region. In addition, other statistical quantities of the fields of temperat     

HYDROGENATION OF A DELOCALIZED DIIMINATE SIX-MEMBERED CHELATE RING IN TETRAAZAMACROCYCLIC NICKEL(II) COMPLEXES BY SODIUM BOROHYDRIDE IN WATER—EFFECT OF PROTONATION-DEPROTONATION EQUILIBRIA AND STEREOSELECIVE REDUCTION

Abstract

Charge delocalized diiminate six-membered chelate rings in the 5,7-dimethyl-1,4,8,11-tetraazacyclotetradecane-4,6-dienatonickel(II) ion(1) and the α,α′-bis(5,7-dimethyl-1,4,8, 11-tetraazacyclotetradeca-4,6-dienato-6-yl)-xylenedinicke(II) ion(2) were hydrogenated in aqueous media by sodium borohydride. In the reduction reactions, control of the pH of the reaction mixture was essential, and the pH of the solution was kept during the reaction at 3 and at 5–6 for hydrogenations of 1 and 2, respectively. The delocalized diiminate chelate ring is in protonation-deprotonation equilibrium with the β diimine form and the pK_a of the equilibrium for 2 was determined to be 9.0 for 2a (o-xylylene bridged complex), 9.3 for 2b (m-xylylene bridged complex), and 10.0 for 2c (p-xylylene bridged complex). The appropriate pH values in the hydrogenation reactions were based on the pK_a′s. X-ray structure analyses on two reduction products of 1 show that the chirality of the two asymmetric carbons in the cyclam ring is of the meso-form in the major reduction product whereas that in the minor product is of the racemic form. In the major reduction product of 2, two chiral carbons in each cyclam ring take the meso-form.     

REGULATION OF GLUCOCORTICOID RECEPTOR BY GLUCOCORTICOIDS(Ⅱ) ——THE STUDIES ON RAT LIVER, BRAIN AND SPLEEN

The concentration of glucocorticoids (GC) in plasma was maintained at stress level, 20--40μg/dl, for 3 days by subcutaneous injection of hydrocortisone (F) in polyvinyl alcohol (PVA) into rats, and the specific binding of [~3H]Dexamethasone (Dex) in liver, spleen and brain was determined before and after injection. The binding capacity of glucocorticoid receptor (GR) in liver and spleen was decreased significantly 1 h after injection and maintained at low level for several days after the concentration of GC in plasma had returned to the normal level. The K_d was not altered. The changes of GR in brain was not significant. Thus it may be concluded that GC can down-regulate GR in rats, but with different characteristics in various target organs.     

HEXAMETHYLDISILAZANE IN THE PRESENCE OF N,N′,N″,N‴-TETRAMETHYLTETRA-2,3-PYRIDINOPORPHYRAZINATO COPPER (II) IS A NEW,MILD AND HIGHLY EFFICIENT REAGENT FOR SILYLATION OF ALCOHOLS AND PHENOLS

Alcohols and phenols are protected with hexamethyldisilazane in the presence of N,N′,N′,N?-tetramethyletra-2,3-pyridinoporphyrazinato copper (II) in good-to-excellent yields at room temperature.     

STUDIES ON BIO-ANTIOXIDANTS (Ⅴ)——INHIBITION OF AUTOXIDATION OF LINOLEIC ACID BY VITAMIN E, VITAMIN C AND LIPOPHILIC VITAMIN C DERIVATIVES IN MICELLES

The antioxidation activity of vitamin E, vitamin C and lipophilic derivatives of vitaminC, i.e. ascorbyl--6-caprylate, 6-laurate and 6-palmitate, on the autoxidation of linoleic acidwere studied in SDS, Triton X-100 and CTAB micelles. The effect of the lipophilicity ofthe antioxidants and micellar effects on the antioxidation activity are discussed.     

SYNTHESIS, CHARACTERIZATION AND CATALYTIC ACTIVITY OF N,N''''-BIS(3-ALLYL SALICYLIDENE)ETHYLENEDIAMINE COBALT(Ⅱ) SCHIFF BASE COMPLEX ANCHORED ON A NEW POLYMER SUPPORT

INTRODUCTIONAlthough homogeneous catalysts have higher selectivity and act under mild experimental conditions in variousreactions they have problems of separation and recovery from reaction products. Hence current research activitiesare aimed at developing catalysts of coordination compounds anchored on suitable supports[1,2]. This techniqueof immobilization of catalyst on an inert support increases the catalytic activity, selectivity, efficiency[3],operational flexibility and stability. …     

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.