Comparative study of the structure of products of plasma modification of globular and fibrillar proteins

The molecular-mass distribution and amino acid composition of globular (albumin, lysozyme) and fibrillar (collagen) proteins subjected to treatment in electron-beam plasmas of various gases were experimentally studied. The samples were treated in the forms of powders and freeze-dried thin films. The electron-beam plasma treatment of powdered collagen resulted in the formation of low-molecular-mass compounds only. The modification of albumin and lysozyme was accompanied by polymerization of the proteins against the background of insignificant degradation. The plasma-stimulated processes occurred in the surface layer of powder particles, whereas the bulk of the sample remained intact. The degradation and polymerization processes in thin films of globular proteins occurred throughout the entire volume of the sample.     

Competition of monomolecular and bimolecular reactions of the alkyl radicals of artemisinin

The competition between monomolecular and bimolecular reactions of alkyl radicals of artemisinin is considered theoretically. The enthalpies of these reactions are calculated. The activation energies and rate constants of intramolecular hydrogen atom transfer, of the decyclization of the alkyl radicals of artemisinin, and of the bimolecular reactions of these radicals with C-H, S-H, and O-H bonds of biological substrates and their analogues are calculated in the framework of the parabolic model. The intramolecular hydrogen transfer reactions proceed at the highest rate. The bimolecular reactions occur somewhat less rapidly. The fastest of them are the reactions of the alkyl radicals with the thio groups of cysteine. The decyclization reactions of all artemisinin alkyl radicals are very slow.     

分子聚集体的光谱模拟

采用Frenkel激子理论研究了一维线性和二维人字形分子聚集体的吸收和发射光谱.通过引入激子离域长度的概念,将聚集体与单分子的光谱线形函数联系起来.计算的光谱结果表明,聚集体的光谱与分子在聚集体中的排列紧密相关.分析了一维J聚集光谱发生红移以及二维人字形分子聚集体吸收光谱形成J和H激子谱带的内在原因.模拟得到的聚集体的...     

Quantitative Evaluation of the Influence of Physicochemical Properties of Solvents on the Kinetics of Formation of Phosphorus-Containing Semicarbazides

The kinetics of the reaction of diphenylphosphinic acid hydrazide with phenyl isocyanate in various solvents at 25°C was studied. The results can be quantitatively correlated with the physicochemical characteristics of solvents using the four-parameter Koppel-Palm equation. This relationship allows quantitative analysis of the solvation effects. The decisive influence on the reaction rate is exerted by the basicity and polarity of solvents. The reaction mechanism is discussed, and the possible scheme of solvation is suggested.     

Effect of form of reagent on particle sizes of precipitates

The particle size of an ionic precipitate is much smaller when one of the reactants is introduced as a solid rather than as a solution The effect is enhanced as the particle size of the solid reagent is decreased. The presence of a freshly dissolved inert electrolyte also influences the particle size of a precipitate The affects are not attributable merely to the degree of supersaturation but rather to the provision by the freshly dissolved material of sites upon which nucleation can be induced.     

Mechanism of oligomerization reactions of silica

The mechanism of the oligomerization reaction of silica, the initial step of silica formation, has been studied by quantum chemical techniques. The solvent effect is included by using the COSMO model. The formation of various oligomers (from dimer to tetramer) was investigated. The calculations show that the anionic pathway is kinetically preferred over the neutral route. The first step in the anionic mechanism is the formation of the SiO-Si linkage between the reactants to form a five-coordinated silicon complex, which is an essential intermediate in the condensation reaction. The rate-limiting step is water removal leading to the oligomer product. The activation energies for dimer and trimer formation ( approximately 80 kJ/mol) are significantly higher than those of the subsequent oligermerization. The activation energies for the ring closure reaction ( approximately 100 kJ/mol) are even higher. The differences in activation energies can be related to the details in intra- and intermolecular hydrogen bonding of the oligomeric complexes.     

Thermal analysis of synthesis of wulfenite

A derivatograph was used in a thermal analysis study of the synthesis of wulfenite (lead molybdate) by the sintering of cerussite or lead oxide with molybdite. The reaction products were identified microscopically and by using a Siemens crystalloflex diffractometer. The DTA curves of mixtures of cerussite with molybdite show first the characteristic peaks of cerussite. The sharp endothermic peak at 300°C reflects the dehydration of hydrocerussite associated with cerussite. The endothermic peak at 350°C indicates the first step of cerussite decomposition, into PbO·PbCO₃, and that at 400°C indicates the second step of its decomposition, into lead oxide. The formation of wulfenite takes place at 520°C in an exothermic reaction. The medium endothermic peaks at 880 and 955°C reflect the melting and volatilization of unreacted lead and molybdenum oxides. The DTA curve of sintering of molybdite with lead oxide reveals the formation of wulfenite at 500°C. The melting and volatilization of unreacted lead and molybdenum oxides appear in only one large and sharp endothermic peak at 980°C.The resulting wulfenite is pale-yellow in thin section, and crystallizes in the tetragonal system, in the form of square tabular crystals, with distinct (011) cleavage.     

两种含杂环的氨基萘醌化合物的合成

以2,3-二氯-1,4-萘醌为主要原料,分别与吗啡啉和糠胺在一定条件下反应生成2种含杂环的氨基萘醌类化合物。2,3-二氯-1,4-萘醌与吗啡啉及2,3-二氯-1,4-萘醌与糠胺物质的量比均为1∶2,反应温度为60℃,溶剂为乙醇。2,3-二氯-1,4-萘醌与吗啡啉反应时间为1 h,产物2-氯-3-吗啡啉基萘-1,4-二酮(a)收率为93.5%;2,3-二氯-1,4-萘醌与糠胺反应时间为4 h,产物N~2,N~3-二(2-呋喃甲基)-1,4-二((2-呋喃甲基)亚胺)-1,4-二氢化萘-2,3-二氯化铵(d)收率为46.7%。对产物进行IR、Uv、MS和H-NMR等分析表征。     

SOL-detectability of liver SPECT--analysis of the structure of ROC-curve

The purpose of this study is to evaluate the clinical efficacy of liver SPECT (single photon emission computed tomography). The two examinations were performed in 76 cases with SOL (space occupying lesion) and 58 normal cases. The results of the image reading by the planar image only (PS) and that of the image reading by the combination of PS and SPECT (PS + SPECT) were analyzed by ROC (receiver operating characteristic) analysis. The ROC curves showed that SPECT appears to reduce the number of results which were equivocal by the image reading of PS only. The detectability of SPECT for SOL in the left lobe of liver was less than that of PS without statistical significance. However, the performance of SPECT for SOL in the right lobe of liver was significantly better than that of PS.     

卷烟化学指标的因子分析

运用因子分析法对A牌号卷烟的18个化学指标进行分析,结果表明:烟丝的总糖、还原糖、总氮、总植物碱、水分、氯离子、钾离子、葡萄糖、麦芽糖、苹果酸、异戊酸、苯甲醇、茄酮、β-大马酮14个指标,及主流烟气的水分、CO、烟碱、焦油4个指标所含的信息可由8个因子来表示。该8个因子模型解释了试验数据总方差的86.7%;烟丝的致香成分、水分、糖类物质、有机酸类物质对卷烟A的质量风格具有重要影响,特别是致香成分在进行卷烟质量表征时应该重点关注。因子分析结果为卷烟的化学表征和质量控制提供了有用的参考。     

HPLC study of the efficiency of extraction of phenolic compounds

Summary The rate of extraction of phenolic compounds in two different solvents has been studied by liquid chromatography (HPLC) under reverse phase, gradient elution conditions. The solvents were diethyl ether and ethyl acetate. The method has been applied to two natural samples, a white wine and apple pulp.     

Determination of the additive physical properties of the components of complex mixtures

Summary The density, refractive index and absorptivities at chosen wave numbers were determined for all the components of three-component mixtures. The mixtures were treated of three-component mixtures. The mixtures were treated as being of unknown qualitative and quantitative composition. The quantitative gas chromatographic analysis by means of the method of linear relationship was carried out and the values of the physical properties of complex mixtures were measured. The corresponding properties of acetone, benzene and toluene were evaluated from the set of appropriate equations.     

Gibbs energies of formation of hydroxides of lanthanides and yttrium

The pH values of the formation of hydrates in solutions of yttrium(III), cerium(III), samarium(III), europium(III), erbium(III), and ytterbium(III) were determined by conductometric titration. The solubility products and Gibbs energies of formation for hydroxides for the elements listed were calculated. The average Gibbs energy of dissolution for lanthanide hydroxides was found to be approximately 149.83 ± 0.90 kJ/mol. The Gibbs energies of formation for hydroxides of the remaining lanthanides were assessed on this basis.     

溶剂化效应对6-亚甲基环戊二烯酮与HCN的反应机理影响的理论研究

在B3LYP/6-311+G**计算水平上, 采用导体极化连续模型研究了溶剂化效应对6-亚甲基环戊二烯酮与HCN反应生成主要产物b类酸的反应机理的影响. 计算结果表明, 在溶剂中的反应机理与在气相中的反应机理一致. 溶剂化效应使反应路径中各驻点的自由能降低, 稳定化了各物质. 溶液中的活化自由能与气相相比也有所降低, 反应更容易发生, 其中CC进攻方式的活化自由能降低得更多.     

交联聚丙烯酰胺溶液染色研究

采用显微镜研究了预交联聚合物凝胶溶液的染色过程,结果表明由于静电作用,亚甲基蓝溶液中阳离子基团与凝胶颗粒中的阴离子基团相互作用形成一种深蓝色的缔合物;交联聚物线团也可以与亚甲基蓝分子形成深蓝色的缔合物,使交联聚合物线团显色,能够直接观测到交联聚合物线团在溶液中的形态。采用扫描电镜、动态光散射、流变仪和岩心封堵实验研究了染色后交联聚合物的线团形态尺寸和溶液的流变性、封堵特性。结果表明,染色后的交联聚合物线团仍是几百纳米左右的在水中分散的球形体,在形态和尺寸上与未染色的交联聚合物溶液没有发生较大的变化;染色后交联聚合物溶液在一定剪切速率范围内表现为胀流性和负触变性。     

竹材非等温热解动力学

利用热重分析技术对竹材在高纯N2条件下,从室温至1273K进行了非等温热解分析,研究了升温速率(5、10、20和40K/min)对热解过程的影响,探讨了其热解机理。研究表明,竹材非等温热解过程主要分为失水干燥、快速热解和缓慢分解三个阶段组成,其中第二阶段是整个过程的主要阶段,析出大量挥发分造成明显失重。升温速率对热解过程有显著影响,随着升温速率的增加,最大热解速度增大,对应的峰值温度升高,热滞后现象加重,热解各阶段向高温侧移动。热解机理满足一维扩散Parabolic法则,反应机理函数为g(α)=α2。不同升温速率下活化能为75.32-82.99kJ.mol-1,指前因子为1.17×105-1.12×106min-1。     

Investigation of the kinetics of the nitration of thiophene derivatives

The kinetics of the nitration of thiophene derivatives with nitric acid in acetic anhydride were investigated. The nitration of 2-substituted thiophenes is a second-order reaction. The rate constants and activation parameters of the reaction were calculated. The possibility of the use of the Hanmett and Yukawa-Tsuno equations for this reaction series is demonstrated. An isokinetic dependence is observed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 167–170, February, 1982.     

Acid hydrolysis of carboxymethylcellulose of low degree of substitution

Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position.     

Quantitative evaluation of the mechanism of electroreduction of benzoyl cyanides

The mechanism of reduction of benzoyl cyanide, 6, p-methoxybenzoyl cyanide, 7, and p-chlorobenzoyl cyanide, 8, has been studied in acetonitrile (6 and 7), N,N-dimethylformamide (6), and acetonitrile containing water (all three compounds). The reaction proceeds by initial reduction to form the anion radical followed by dimerization to produce an intermediate dianion, the dianion of the dicyanohydrin of benzil. The latter loses cyanide to give the anion of the monocyanohydrin of benzil, which undergoes two parallel reactions: expulsion of cyanide to give the corresponding benzil and rearrangement to the monoanion of mandelonitrile benzoate. The addition of water brings about an increase in the dimerization rate constant and an associated increase in the amount of benzil that is produced. The standard potentials for the initial reduction step have been evaluated, and their dependence on the substituent is discussed. The dimerization rate constants have also been evaluated.     

Calculation of enthalpies of hydrogenation of hydrocarbons

Sets of hydrogen molecule equivalents have been developed which permit the calculation of hydrogenation of different types of carbon-carbon bonds from ab initio total energies (3-21G and 6-31G* basis sets, and, to a more limited extent, for MP2/6-31G* data) of reactants and products. The calculated enthalpies of hydrogenation are in good agreement with experiment for unstrained molecules, with average errors on the order of 2 kcal/mol. The 6-31G* equivalents allow the enthalpies for strained molecules to be calculated accurately, but the 3-21G equivalents do not. The equivalents for both basis sets have been tested by calculating the enthalpies of hydrogenation of carbon-carbon bonds in nitrogen- and oxygen-containing organic molecules, free radicals, and classical carbocations. The results are in good agreement with experiment in most cases.