Direct Surface‐Enhanced Raman Scattering Analysis of DNA Duplexes

The exploration of the genetic information carried by DNA has become a major scientific challenge. Routine DNA analysis, such as PCR, still suffers from important intrinsic limitations. Surface‐enhanced Raman spectroscopy (SERS) has emerged as an outstanding opportunity for the development of DNA analysis, but its application to duplexes (dsDNA) has been largely hampered by reproducibility and/or sensitivity issues. A simple strategy is presented to perform ultrasensitive direct label‐free analysis of unmodified dsDNA with the means of SERS by using positively charged silver colloids. Electrostatic adhesion of DNA promotes nanoparticle aggregation into stable clusters yielding intense and reproducible SERS spectra at nanogram level. As potential applications, we report the quantitative recognition of hybridization events as well as the first examples of SERS recognition of single base mismatches and base methylations (5‐methylated cytosine and N6‐methylated Adenine) in duplexes.     

利用两种微生物的协同作用进行柴油的深度脱硫

红串红球菌通过4S途径降解二苯并噻吩(DBT)产生 和2-羟基联苯(2-HBP). 和2-HBP的存在对红串红球菌的进一步脱硫有抑制作用, 加入脱 和2-HBP 的菌株可以解除 和2-HBP对红串红球菌脱硫反应的抑制, 使该反应继续向生成产物的方向移动, 从而提高其脱硫率. 在脱硫菌和专一性降解 的水解好氧菌(代号: PYS)的协同作用下可以使高浓度的DBT从1.142 mmol/L降到0.0468 mmol/L, 降解率达到95.9%, 比没有加PYS时提高32%的脱除率. 在油水比为1∶9的条件下, 可以将柴油中的硫从554 mg/mL降到306 mg/mL, 降解率达到44.8%.     

SiO_2负载磷钨钒杂多酸杂化材料的制备及其氧化脱硫性能的研究

利用磷酸氢二钠、偏钒酸纳和钨酸钠为原料,合成了具有Keggin结构的磷钨钒杂多化合物(H5PW10V2O40),并与1-丁基-3-甲基咪唑溴(BmimBr)离子液体反应生成一种杂多酸杂化材料([Bmim]5PW10V2O40)。利用红外光谱(FT-IR)、X射线衍射光谱(XRD)和紫外可见光谱(UV-vis)对所合成的杂多酸杂化材料进行表征。结果表明,[Bmim]5PW10V2O40具有咪唑阳离子基团和Keggin型杂多阴离子基团的结构特征,并且两种基团之间存在相互作用。以SiO_2为载体制备负载型的杂多酸杂化材料催化剂[Bmim]5PW10V2O40/SiO_2,以H2O_2作为氧化剂,考察该催化剂对模拟油中DBT的氧化性能,并优化氧化反应条件,在反应温度40℃,O/S物质的量比为3.0的条件下,反应50min,模拟油品中的DBT的转化率可以达到100%。催化剂可以通过离心法分离,经过干燥之后,可以循环使用至少七次,而对DBT的氧化活性没有降低。     

Hydrolysis and Enantiodiscrimination of (R)- and (S)-Oxazepam Hemisuccinate by Methylated β-Cyclodextrins: An NMR Investigation

Partially and exhaustively methylated β-cyclodextrins [(2-methyl)-β-CD (MCD), heptakis-(2,6-di-O-methyl)-β-CD (DIMEB), and heptakis-(2,3,6-tri-O-methyl)-β-CD (TRIMEB)] have been compared in the hydrolysis and enantiodiscrimination of benzodiazepine derivative (R)- or (S)-oxazepam hemisuccinate (OXEMIS), using nuclear magnetic resonance (NMR) spectroscopy as an investigation tool. After 6 h, MCD induced an 11% hydrolysis of OXEMIS, remarkably lower in comparison with underivatized β-CD (48%), whereas no hydrolysis was detected in the presence of DIMEB or TRIMEB after 24 h. DIMEB showed greater ability to differentiate OXEMIS enantiomers in comparison to TRIMEB, by contrast MCD did not produce any splitting of racemic OXEMIS resonances. Both enantiomers of OXEMIS underwent deep inclusion of their phenyl pendant into cyclodextrins cavities from their wider rims, but tighter complexes were formed by DIMEB with respect to TRIMEB.     

A study of the partitioning and sorptive behaviour of butyltins in the aquatic environment

This study was designed to investigate the partitioning and sorptive behaviour of tributyltin(TBT), and its degradation products dibutylitin (DBT) and monobutyltin (MBT), in the aquatic environment. Factorial experiments were undertaken to determine the importance of pH and particulate matter concentration in the sorption of butyltin compounds to solid phases. Results indicate that in freshwaters MBT, and to a lesser extent TBT, will be partitioned towards the particulate phase, whereas DBT exhibits a 50:50 partitioning between particulate and solution phases. In estuarine waters, whilst MBT will almost exclusively sorb on to particulates, TBT will be predominantly in the solid-phase fractions but 10–30% may remain in solution. DBT, in contrast, is solubilized in estuarine waters. A more detailed investigation of TBT sorption and particulate matter concentration was undertaken using adsorption isotherms on different sediment types. The results from batch isotherm tests plotted according to the Freundlich adsorption model revealed that TBT adsorption varied with sediment type, increasing in the order sandy-silt < silty-sand < silty-clay. TBT sorption was found to be reversible, indicating that contaminated sediments may release TBT to overlying waters following sediment distrubance. Interstitial water partitioning studies indicate that TBT predominates in the particulate phase with partition coefficients for TBT higher than for DBT and MBT. The TBT partition coefficient in interstitial waters appears to be related to total organic carbon loadings.     

Chromatographic study of the inclusion properties of cyclodextrins: Study of inclusion from the gaseous phase

The ability of cyclodextrins to form inclusion compounds with substances in the gaseous phase was studied chromatographically. Chromatographic measurements enabled the mechanism of the inclusion process to be clarified and have shown that other forces, mainly hydrogen bonding, play a role in the process in addition to the geometric properties of the interacting substances. These facts are expressed in terms of the changes in the chromatographic quantities and of the changes in the thermodynamic characteristics that are derived from the former quantities. The selective properties of cyclodextrins have been utilized in separations of substances that are otherwise separated with difficulty (xylenes, diethylbenzenes, trimethylbenzenes, etc.).     

Synthesis and efficiency of photolysis of methylated 2-dialkylamino- and 2-piperidino-1,4-naphthoquinones

2-Dialkylamino- and 2-piperidino-1,4-naphthoquinones with a methyl group in position 3 or 5(8) of the naphthoquinone were synthesized by reacting dimethyl- and diethylamines and piperidine with 2- and 5-methyl-1,4-naphthoquinones. The quantum yields of photoconversion of the synthesized compounds in benzene were determined. A 1.2- to 6.5-fold increase of the quantum yield over that of 2-dimethylamino-1,4-naphthoquinone was established. A comparison of the quantum yields with the calculated charges on the reaction centers in the excited (T ₁) state showed that there is not a linear relationship between them.Institute of Organic Chemistry, Russian Academy of Sciences, Siberian Branch, 630090 Novosibirsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 707–714, March, 1992.     

Concise Synthesis of Ring-Fission Metabolites of Epicatechin: 5-(3,4-Dihydroxybenzyl)dihydrofuran-2(3H)-one M6

The ring-fission metabolites of epicatechin, 5-(3,4-dihydroxybenzyl)dihydrofuran-2(3H)-one M6 and 3-methylated M6, were prepared from 3,4-dihydroxybenzaldehyde and furan-2(5H)-one using two new concise methods in excellent yields (three or two steps in 40–60% overall yield).     

N~ε-甲基赖氨酸的合成

设计并合成了不同α-氨基保护的一甲基,二甲基和三甲基赖氨酸,其结构经1H NMR和MS表征.     

Random-fuzzy model for the ductile/brittle transition

IntroductionTheductile brittletransition (DBT )ofsteelalloysisinfluencedbythematerialmicrostructureandtestingtemperature[1].Availablereferencesrangingfromanalyticalapproachtoempiricaltestsaretoonumeroustolist.Mostofthesemodesaredeterministic ,whichdidnottaketherandomnessoftheparametersandman_madeerrorintoconsideration .Thebasicproposesofthispaperistounderstandthetransitionbyanewrandom_fuzzymodel.Theductile brittletransitioninvolvestheductilefracture ,brittlefractureandthetransition .Inacerta…