Regioselectivity of olefin oxidation by iodosobenzene catalyzed by metalloporphyrins : control by the catalyst

The regioselectivity of the oxidation of three monosubstituted olefins, 6-phenoxyhex-1-ene, hex-1-ene and styrene, by iodosobenzene in the presence of various Fe-, Mn- or Cr-tetraaryl-porphyrins, was studied. It was found that, besides epoxides, known products from such systems, allylic alcohols and aldehydes were formed, the latter not being derived from the corresponding epoxides. The relative importance of these reactions greatly depends upon both the metal and porphyrin constituents of the catalyst. More particularly, the competition between epoxidation and allylic hydroxylation can be efficiently controlled by non-bonded interactions between the olefin and porphyrin substituents. No hydroxylation of the aromatic rings and no oxidative dealkylation of the ether function was detected.     

Electrogravimetric Analysis by Quartz-Crystal Microbalance on the Consumption of the Neurotransmitter Acetylcholine by Acetylcholinesterase

Electrogravimetric analysis was performed on the consumption of the neurotransmitter Acetylcholine (ACh) by Acetylcholinesterase (AChE) in situ and in real time. Michaelis-Menten assumption was achieved by using an enzyme micro-reactor in which the total enzyme was anchored in a quartz crystal microbalance chip (QCM-chip) with a strategically engineered self-assembled monolayer (SAM) of alkanethiols, which can prevent diffusion-controlled or spatially restricted kinetics. The real-time frequency changes indicated the rate of the products formation from enzymatic reaction. The QCM-chip was tested showing that it could demonstrate AChE inhibition by physostigmine.     

On the magnitude of the chelate effect for the recognition of proteins by pharmacophores scaffolded by self-assembling oligonucleotides

The simultaneous interaction of the binding moieties of a bidentate ligand on adjacent epitopes of a target protein represents an attractive avenue for the discovery of specific, high-affinity binders. We used short DNA fragments in heteroduplex format to scaffold pairs of binding molecules with defined spatial arrangements. Iminobiotin derivates were coupled either via bifunctional linkers or by using various oligonucleotides, thus allowing monovalent or bivalent binding to streptavidin. We determined the binding affinities of the synthesized constructs in solution. We also investigated the efficiency of recovery of superior bidentate ligands in affinity capture experiments, by using both radioactive counts and DNA microarrays as readouts. This analysis confirmed the suitability of the DNA heteroduplex as a scaffold for the identification of synergistic pairs of binding moieties, capable of a high-affinity interaction with protein targets by virtue of the chelate effect.     

Synthesis of vinylindoles and vinylpyrroles by the Peterson olefination or by use of the Nysted reagent

Vinylindoles and vinylpyrroles were prepared from their corresponding aldehydes or ketones using the Peterson olefination, or by use of the Nysted reagent, a commercially available gem‐dimetallic compound. The two methods provide efficient and convenient access to these useful heterocyclic 1,3‐diene systems. J. Heterocyclic Chem., (2011).     

Complexation of the lanthanides by pyrazinecarboxylate

The stability constants of the lanthanide pyrazinecarboxylate complexes in aqueous solution have been determined in the ionic medium of 1.0 M NaClO₄ at 25°C. The stability of the lanthanide pyrazinecarboxylates is relatively larger than those of the monodentate ligands, indicating that the heterocyclic 1-nitrogen atom of the ligand is involved in the chelate formation.     

Interpretation of the experimental data on the reduction reaction of NO by CO on rhodium by Monte Carlo simulations and by solving the kinetic equations of the reaction mechanism

Some mechanisms of the reduction reaction of NO by CO on rhodium are analyzed and discussed, solving the kinetics equations and using Monte Carlo simulations, in terms of its ability to interpret the recent experiments of Zaera et al., who used a molecular beam method to study experimentally the kinetics of the reaction. Critical use is also made of the information on rate constants available for this system in the literature. Uniform catalytic surfaces and the statistical incipient percolation cluster (IPC) fractal are considered in the simulations.     

应用超临界流体萃取分离-气相色谱-质谱分析法建立中药温郁金的指纹图谱及其系统聚类分析

收集生长于浙江省瑞安市8个产地的温郁金样品14批次,分别经清洗、冷冻干燥及碾磨粉碎,得到通过0.425mm筛孔药筛的粉末状样品14个。称取此样品各30g,分别按试验选定的最佳条件[萃取温度35℃,萃取压力15MPa,萃取时间(静态30min,动态90min)]进行超临界流体萃取分离,所得萃取物收集于甲醇5mL中,并进行气相色谱-质谱法(GC-MS)分析。色谱分离采用HP-5ms石英毛细管色谱柱和在50~220℃之间程序升温模式;质谱测定采用电子轰击离子源(EI),在质荷比(m/z)50~650内进行扫描。所得总离子流色谱图中共有50多个色谱峰,选择保留时间在40min以内的共有峰26个作为考察对象,选择保留时间为17.12min的莪术二酮为参考峰,计算共有峰的相对保留时间α和峰面积百分比S以及各样品与S3的S值的最大差值ΔS(Max)%,并建立了14个样品的指纹图谱。根据GC-MS分析所得结果并与NIST 14谱库比对,对共有峰作出鉴定。通过SPSS 16.0软件,采用系统聚类分析法对所分析的14批次温郁金样品的指纹图谱进行分类比较。应用指纹图谱对2个市售温郁金产品作了组分鉴定和产地认定。     

Synthesis of hydroxyethylhydrazine by the Raschig process and comparison with synthesis by the alkylation process

The Raschig synthesis of hydroxyethylhydrazine (HEH) is studied, that is, the reaction of monochloramine on ethanolamine. The formation of HEH is monitored by UV spectrometry, and the influence of temperature and pH is studied. The primary reaction is an SN₂‐type mechanism, whereas the main secondary reaction is the oxidation of HEH by monochloramine. This reaction is also monitored by UV spectrometry, and the oxidation product is identified by GC–MS analysis, showing the formation of hydroxyethylhydrazone. The reaction mechanisms and the rate constants were determined, and the results permit establishing the main reactions occurring during HEH synthesis. These reactions were validated in a concentrated medium, with the systematic study of the influence of the molar ratio p ([HEH]₀/[NH₂Cl]₀) and the final sodium hydroxide concentration and temperature. A comparison is made with the other synthesis process already published, that is, the alkylation of hydrazine by either chloroethanol or epoxide. © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 331–344, 2011     

Influence of the column radial heterogeneity on the determination of single-component isotherms by the elution by characteristic point method

The influence of the column radial heterogeneity on the determination of equilibrium isotherm data by the elution by characteristic point (ECP) method is studied using nondimensional numerical calculations and taking into account typical radial distributions of the mobile phase flow velocity and the column efficiency across a column. Overloaded elution peaks were calculated with the equilibrium-dispersive model as a function of four dimensionless parameters, the number of theoretical plates at the center of the column, the Langmuir equilibrium constant, the retention and the loading factors. The influence of the mass transfer resistances and the radial heterogeneity of the column on the ECP data was analyzed by comparing the true isotherm and the one estimated from the diffuse profile of overloaded peaks. The results provide information on the accuracy of the ECP method. The error made increases with increasing degree of radial heterogeneity. This error can be corrected by using the results of the nondimensional numerical calculations, allowing a further extension of the applicability of the ECP method.     

Characterization of thermoreversible polymer gels by the degree of crystallinity by surface area

A characterization for crystalline junction polymer gels has been extended by introducing a new parameter which implies a measure of the number of the polymer molecules passing through the crystallizing junctions. The parameter has been considered in a theoretical gel melting relation derived by Takahashi, Nakamura, and Kagawa and a crystallite size distribution has also been considered. The equation obtained was examined on ethylene–propylene copolymer gels by using the previous data of melting temperatures determined from DSC, crystallite sizes from x-ray and DSC measurements, and reaction probabilities from ¹³C-NMR measurements. Consequently, the parameter was found to be helpful as one additional measure. Also, it was confirmed that the average crystallite sizes estimated in several different ways were all in good agreement with the conventional data. © 1996 John Wiley & Sons, Inc.     

Modification of textile materials by the deposition of nanocoatings by magnetron ion-plasma sputtering

Possibilities of surface modification of textile materials and polymer films by the deposition of nano-coatings using magnetron ion-plasma sputtering are considered. Technical characteristics of the new industrial equipment for these processes are presented. Examples of materials thus produced are given and the prospects of the new technology are discussed.     

Fluorescence Enhancement of Oxadiazole by Albumin and the Microdetermination of Albumin by Fluorospectrophotometry

A simple, rapid, and sensitive fluorometric method for determining microamount albumin selectively is presented. The fluorescence of 2,5-di(orthoamino phenyl)-1,3,4-oxadiazole is enhanced greatly by the addition of albumin. Based on this, a range of 6.8–47.6 μg/ml albumin can be detected. All other proteins have little interferences on the assay. Experimental parameters are optimized. In detection of serum albumin, the method gives values close to those of the BCG method. Scatchard analyses show that the association constant of bovine serum albumin with oxadiazole is 6.82 × 10⁴M⁻¹. Fluorescence displacement data indicate that oxadiazole binds to the bilirubin site.     

Synthesis of 1,2-benzoquinones by the oxidation of 1,4-benzodioxins by peroxide derivatives

The oxidation reaction of 1,4-benzodioxin 1 by m-chloroperbenzoic acid (m-CPBA) and t-butyl hydroperoxide (t-BHP) are reported. 1,2-Benzoquinone 2 was given in moderate yields by the m-CPBA oxidation of 1,4-benzodioxin 1 , while 1,2-benzoquinone 2 was predominantly formed by t-BHP oxidation.     

Determination of the critical conditions for fiber formation by the fibroin of natural silk by polarization-optical methods

The processes of fiber formation by the fibroin of natural silk have been studied by the methods of birefringence in a longitudinal hydrodynamic field and optical rotatory dispersion. The experiments were performed with the direct drawing of a fiber from the secretion of the silk glands of the silkwormBombyx mori. The position of appearance of a longitudinal hydrodynamic field within the gland has been detected and experimental results have been obtained which permit an evaluation of the critical condition for the - structural transition of the fibroin chains.Institute of the Chemistry and Physics of Polymers, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 44 26 61. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 623–627, July–August, 1997.