Quantification of analytes in overlapping peaks from capillary electrophoresis using multivariate curve resolution-alternating least squares methods

Application of multivariate curve resolution with alternating least squares (ALS) methods to second-order data from capillary electrophoresis diode array detector (CE-DAD) is shown. Second-order data are easily obtained by setting individual data matrix of CE run one in top of the other. Initial qualitative solutions obtained by evolving factor analysis can be further optimized by simultaneous analysis of multiple electrophoresis run data with ALS regression. Quantification is achieved by the comparison of the analyte peak areas with that of pure standards. During the ALS regression procedure, the following constraints were applied: (i) both concentrations and unit pure spectra of the resolved components must be positive; (ii) elution profiles have an unimodal shape; (iii) correspondence exists between common species in the different data matrices; (iv) the pure spectrum of each species is the same in all runs where it is present. The above methods were applied for the determination of dinitrotoluene (DNT) isomeric compounds in overlapping peaks from CE.     

The first mu3-oxalato-bridged copper complex with tridentate Schiff base ligand N-ethyl-N'-salicylidene-1,2-diaminoethane: synthesis,structure, and magnetic properties

The first mu(3)-oxalato-bridged copper(II) complex, [[Cu(3)(L)(3)(mu(3)-C(2)O(4))][Cu(L)(H(2)O)](ClO(4))(2)] x 0.5(H(2)O) x 0.5(CH(3)OH), where HL = N-ethyl-N'-salicylidene-1,2-diaminoethane, has been synthesized and characterized by variable-temperature magnetic susceptibility measurement. The complex exhibits ferromagnetic coupling between the oxalato-bridged copper atoms and antiferromagnetic coupling between the oxygen-bridged copper atoms.     

分解水制氢的KNO3—I2循环之研究：Ⅲ.代替电解反应的一个子循环

本文提出了一个硫酸中间盐子循环用以代替分解水制氢的KNO_3-I_2混合循环中的电解反应,从而使原混合循环变为一个纯热化学循环。     

Parallel iterative reaction path optimization in ab initio quantum mechanical/molecular mechanical modeling of enzyme reactions

The determination of reaction paths for enzyme systems remains a great challenge for current computational methods. In this paper we present an efficient method for the determination of minimum energy reaction paths with the ab initio quantum mechanical/molecular mechanical approach. Our method is based on an adaptation of the path optimization procedure by Ayala and Schlegel for small molecules in gas phase, the iterative quantum mechanical/molecular mechanical (QM/MM) optimization method developed earlier in our laboratory and the introduction of a new metric defining the distance between different structures in the configuration space. In this method we represent the reaction path by a discrete set of structures. For each structure we partition the atoms into a core set that usually includes the QM subsystem and an environment set that usually includes the MM subsystem. These two sets are optimized iteratively: the core set is optimized to approximate the reaction path while the environment set is optimized to the corresponding energy minimum. In the optimization of the core set of atoms for the reaction path, we introduce a new metric to define the distances between the points on the reaction path, which excludes the soft degrees of freedom from the environment set and includes extra weights on coordinates describing chemical changes. Because the reaction path is represented by discrete structures and the optimization for each can be performed individually with very limited coupling, our method can be executed in a natural and efficient parallelization, with each processor handling one of the structures. We demonstrate the applicability and efficiency of our method by testing it on two systems previously studied by our group, triosephosphate isomerase and 4-oxalocrotonate tautomerase. In both cases the minimum energy paths for both enzymes agree with the previously reported paths.     

Liquid Densities and Excess Molar Volumes for Binary Systems (Ionic Liquids + Methanol or Water) at 298.15, 303.15 and 313.15 K,and at Atmospheric Pressure

Binary excess molar volumes, V _m ^E, have been evaluated from density measurements, using a vibrating tube densimeter over the entire composition range for binary liquid mixtures of ionic liquids 1-ethyl-3-methyl-imidazolium diethyleneglycol monomethylethersulphate [EMIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻ or 1-butyl-3-methyl-imidazolium diethyleneglycol monomethylethersulphate [BMIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻ or 1-methyl-3-octyl-imidazolium diethyleneglycol monomethylethersulphate [MOIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻+methanol and [EMIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻+water at 298.15, 303.15 and 313.15 K. The V _m ^E values were found to be negative for all systems studied. The V _m ^E results are explained in terms of intermolecular interactions and packing effects. The experimental data were fitted by the Redlich-Kister polynomial.     

Interference of Copper(II) ions with Non-covalent Interactions in Uridine or Uridine 5′-Monophosphate Systems with Adenosine,Cytidine, Thymidine and their Monophosphates in Aqueous Solution

Coordination reactions of copper(II) ions and their effect on non-covalent interactions in uridine (Urd) or uridine 5′-monophosphate (UMP) systems with nucleosides (Ado, Cyd, Thd) and nucleotides (AMP and CMP) in aqueous solutions have been studied. At high pH the effective coordination centers are deprotonated N(3) atoms from Urd and Thd, whereas at low pH, the N(3) atoms of pyrimidine nucleosides are blocked for coordination and the metallation sites are endocyclic nitrogen atoms from Ado, Cyd, AMP and CMP. Moreover, at low pH, the main reaction center in nucleotide solutions is the phosphate group. The NMR study has proven the occurrence of non-covalent ion-dipole interactions and stacking interactions in the systems considered. Introduction of a copper ion in the majority of systems causes the disappearance of weak interactions between ligands. The structures of the complexes in solution have been inferred from the equilibrium study: an analysis of the pH range of their occurrence with respect to the pH range of deprotonation of particular groups in the compounds studied, using Vis, EPR and ¹³C as well as ³¹P NMR spectral analysis.     

Fast Marching Method for Calculating Reactive Trajectories for Chemical Reactions

We present a method for computing classical Newtonian trajectories that minimize the path length or transit time from reactant to product. Our approach is based on a generalization of the fast-marching method, which allows us to construct the solution of the Hamilton-Jacobi equation for the action that optimizes the desired quantity. The resulting “reactive paths” can be interpreted as reaction coordinates but, unlike more conventional choices, they contain dynamical information about the chemical system of interest.     

Modification of the halogen end groups of polystyrene prepared by ATRP

The stabilization modification of the halogen end groups of polystyrene prepared by atom transfer radical polymerization (ATRP) has been attempted. The reaction mechanism adopted is radical chain transfer reaction, and iso-propylbenzene is employed as not only the chain transfer agent but also the solvent. Moreover, Cu⁰ is used as the acceptor of the transformed halogen atom in some experiments. As evidenced by ¹H NMR analysis of the modified products, the halogen end group can really be converted into the much more stable carbon-hydrogen structure. When Cu⁰ is not used, the conversion of the halogen end groups rises rapidly during the early stage and the increase rate slows down after about 8 h reaction. In view of the influence of reaction temperature on the modification, the conversion increases almost exponentially with temperature in the range of 80-100 °C, and the increase rate slows down at higher temperature. ¹H NMR and SEC analyses prove that the modification reaction does not destroy the polymer backbone and the molecular weights remain almost the same as those of the unmodified samples. When Cu⁰ is introduced, the modification reaction proceeds much rapidly, the conversion of the halogen end groups rises almost linearly at the early stage and the nearly complete (>95%) dehalogenation of the polymeric chains is observed after only 12 h reaction. However, the molecular weights rise and the polydispersities become wider after the modification, which implies that the modification is accompanied with the couple termination of the polystyrene radicals besides chain transfer reaction. Furthermore, the couple termination can be restrained at some lower catalyst concentration. Indeed, the modified polymers show improved thermal stability, the initial weight loss temperatures is increased from 196 °C to 378 °C for the linear polystyrene and from 203 °C to 261 °C for the hyperbranched polystyrene.     

Ab initio and infrared spectral study of 4′-substituted phenylthiolbenzoates

The geometry of the 4′-cyano-(4′-CNPTB) and the 4′-methoxy-(4′-MePTB) phenylthiolbenzoates were obtained by ab initio calculations employing 6–31G basis set at Hartee-Fock level of theory. The results predict an extended form of the molecules and torsional angle between the phenyl rings at 90.85(6)⁰ and 90.87(3)⁰, respectively. On the basis of vibrational analysis the frequency assignment was carried out. The calculated frequencies were compared with the experimental IR spectral data in carbon tetrachloride, carbon disulfide solutions and in solid state.     

Cell detection based on protein array using modified glass slides

A protein array for cell detection was fabricated by spotting different antibodies on modified glass slides. Glass slides were modified to allow antibodies to be immobilized on it and to selectively bind antigens. Antibodies were specially selected with the cells to be detected as targets, which permitted target cells in samples to bind specifically to the array with little nonspecific binding. Results can be obtained by directly putting the samples onto the array for 1 h or a little longer to let the cells specifically interact with the antibodies. After washing the unbound samples away, images were observed with a microscope and captured with a CCD camera. The assessment of antibody-cell binding was evaluated by capturing red blood cells (RBCs) in human blood with blood group antibodies (anti-A and anti-B). Blood group antibodies were spotted on the modified glass slide and kept at 4<.deg> degrees C overnight for immobilization. Human blood samples diluted to different concentrations were used to examine the sensitivity and specificity of the method.