Characterization of atenolol transformation products in ozonation by using rapid resolution high-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry

This experiment investigated the transformation pathway of atenolol, a widely used β-blocker, in the ozonation process through the identification of generated intermediate compounds. In order to characterize the contribution of ozone and hydroxyl radical (•OH) in the transformation of atenolol, ozonation were performed at pH 2, 7 and 9. 15 major transformation products have been identified based on the chromatographic behavior of these compounds and the information obtained from accurate mass MS and MS/MS spectra. By comparing to the elution pattern of the identified transformation products and its fragmentation pattern in the MS/MS spectrum, a variety of isomers of the transformation products were characterized.Identified transformation products of atenolol are including its mono-, di and tri-hydroxylated derivatives as well as the aliphatic and aromatic ring breakdown products. Transformation of atenolol in the ozonation involved hydroxylation reaction, aromatic ring opening reaction, oxidation and cleavage of 2-hydroxy-3-(isopropylamino)propoxy group of atenolol. In ozonation, aromatic ring of atenolol was transformed through the reaction with both ozone and •OH whereas the aliphatic chain of atenolol was degraded mainly through the reaction with •OH. The results also indicated that both •OH and ozone involved in the aromatic ring opening reaction.     

α-Iithioalkylphosphonates as Functional Group Carriers. an in Situ Acrylic Ester Synthesis

Condensation of α -lithioalkylphosphonates with diethylcarbonate in the presence of LDA generates carbetoxy-alkylphoshonate anions which upon treatment at room temperature with aldehydes constitutes an in situ acrylic ester synthesis.     

Molecular dynamics simulations on the inhibition of Cyclin-Dependent Kinases 2 and 5 in the presence of activators

Interests in CDK2 and CDK5 have stemmed mainly from their association with cancer and neuronal migration or differentiation related diseases and the need to design selective inhibitors for these kinases. Molecular dynamics (MD) simulations have not only become a viable approach to drug design because of advances in computer technology but are increasingly an integral part of drug discovery processes. It is common in MD simulations of inhibitor/CDK complexes to exclude the activator of the CDKs in the structural models to keep computational time tractable. In this paper, we present simulation results of CDK2 and CDK5 with roscovitine using models with and without their activators (cyclinA and p25). While p25 was found to induce slight changes in CDK5, the calculations support that cyclinA leads to significant conformational changes near the active site of CDK2. This suggests that detailed and structure-based inhibitor design targeted at these CDKs should employ activator-included models of the kinases. Comparisons between P/CDK2/cyclinA/roscovitine and CDK5/p25/roscovitine complexes reveal differences in the conformations of the glutamine around the active sites, which may be exploited to find highly selective inhibitors with respect to CDK2 and CDK5.     

Fabrication of aligned carbon nanotubes on Cu catalyst by dc plasma-enhanced catalytic decomposition

Aligned multi-walled carbon nanotubes (ACNTs) are deposited using copper (Cu) catalyst on Chromium (Cr)-coated substrate by plasma-enhanced chemical vapor deposition at temperature of 700 °C. Acetylene gas has been used as the carbon source while ammonia is used for diluting and etching. The thicknesses of Cu films on Cr-coated Si (100) substrates are controlled by deposition time of magnetron sputtering. The growth behaviors and quality of ACNTs are investigated by scanning electron microscopy (SEM) and transmission electron microscopy. The different performance of ACNTs on various Cu films is explained by referring to the graphitic order as detected by Raman spectroscopy. The results indicate that the ACNTs are formed in tip-growth model where Cu is used as a novel catalyst, and the thickness of Cu films is responsible to the diameter and quality of synthesized CNTs.     

Abrupt stress induced transformation in amorphous carbon films with a highly conductive transition phase

We demonstrate that when, and only when, the biaxial stress is increased above a critical value of 6+/-1 GPa during the growth of a carbon film at room temperature, tetrahedral amorphous carbon is formed. This confirms that the stress present during the formation of an amorphous carbon film determines its sp;{3} bonding fraction. In the vicinity of the critical stress, a highly oriented graphitelike material is formed which exhibits low electrical resistance and provides Ohmic contacts to silicon. Atomistic simulations reveal that the structural transitions are thermodynamically driven and not the result of dynamical effects.     

Rigidity of multi-graphs. I. Linking rigid bodies in n-space

A linkage of rigid bodies in n-space consists of a set of n-dimensional rigid bodies in n-space, certain pairs of which are linked together by one or more rigid bars using universal (ball) joints. Such a structure is canonically associated (bodies to vertices, bars to edges) with a multi-graph. We show that a multi-graph can be realized as a rigid linkage of rigid bodies in n-space if and only if it contains $\text{n(n + 1)}\text{2}$ edge disjoint spanning trees. Some techniques for generating rigid linkages are also discussed.     

条纹投影形貌测量的品质评估位相展开

0Introduction Phaseunwrappingisrelatedtomanyresearchdisciplinesincludingopticalmetrology,synthetic apertureradar,acousticimaging,magneticresonanceimaging(MRI)andmicrowaveinterferometry.AnexcellenttextbookbyGhigliaandPritt[1]presentedthefundamentaltheoryan…     

Floating resistivity detector for microchip electrophoresis

A newly developed conductivity detector, the floating resistivity detector (FRD), for microchip electrophoresis was introduced in this work. The detector design permits decoupling of the detection circuit from the high separation voltage without compromising separation efficiency. This greatly simplifies the integration of microchip electrophoresis systems. Its method of detection relies on platinum electrodes being dipped in two buffer-filled branched detection probe reservoirs on the microchip device. In this way, analytes passing through the detection window will not pass through and subsequently adsorb onto the electrodes, alleviating problems of electrode fouling due to analyte contamination and surface reactions. A customized microchip design was proposed and optimized stepwise for the new FRD system. Each branched detection probe was determined to be 4.50 mm long with a 0.075 mm detection window gap between them. The distance between the detection window and buffer waste reservoir was determined to be 1.50 mm. The optimized microchip design was subsequently used in the analysis of four groups of analytes - inorganic cations, amino acids, aminoglycosides antibiotics, and biomarkers. Based on the preliminary results obtained, the detection limits were in the range of 0.4-0.7 mg/L for the inorganic cations and 1.5-15 mg/L for the amino compounds.