On-capillary derivatization and analysis of amino acids in human plasma by capillary electrophoresis with laser-induced fluorescence detection: application to diagnosis of aminoacidopathies

A capillary electrophoresis with laser-induced fluorescence detection method for the analysis of free amino acids (AA) in human plasma was developed. A mixture of 16 AA was on-capillary derivatized with 3-(2-furoyl)quinoline-2-carboxaldehyde (FQ) and separated inside the capillary in less than 30 min using 70 mM borax-3.5 mM SDS pH 9.3 as running buffer. Four plasma samples from a healthy donor and patients suffering from phenylketonuria, propionic acidemia, and tyrosinemia type II were studied. Repeatabilities calculated as intra-day RSD (n = 3) values for the AA involved in these aminoacidopathies (glycine, phenylalanine, and tyrosine) were in the range of 0.3 to 1.2% for migration time and 3.7 to 8.2% for peak height. Reproducibilities calculated as inter-day RSD (n = 4) values for the same AA were between 0.7 and 1.4% for migration time and 4.7 and 9.1% for peak height. A fast qualitative analysis allowed the identification of the corresponding disease by comparing the electrophoretic profiles from the patient and the healthy donor and noting the increased level of the specific AA accompanying each individual disease. The results of the quantitative analysis for glycine, phenylalanine, and tyrosine in the plasma samples studied using the developed method showed a good agreement with those provided by the Center of Diagnosis of Molecular Diseases using a standard method for AA analysis.     

CH4 dissociation on Ni surfaces: Density functional theory study

CH₄ dissociation on Ni surfaces, which is important in CH₄ reforming reactions, was discussed by using density functional theory. It was found that the CH_x species were changed to anions after chemisorption. The site preference of CH_x (x = 0-3) species on Ni(1 1 1), Ni(1 0 0) and Ni(1 1 0) was located on the basis of the computed chemisorption energies. Ni(1 0 0) is the most preferred surface for CH₄ dissociation, compared to Ni(1 1 0) and the widely investigated Ni(1 1 1).     

Density Functional Theory Calculations on Ni-Ligand Bond Dissociation Enthalpies

The formation and breaking of Ni-L (L=N-heterocyclic carbene, tertiary phosphine etc.) bond is involved in many Ni-catalyzed/mediated reactions. The accurate prediction of Ni-L bond dissociation enthalpies (BDEs) is potentially important to understand these Ni-complex involving reactions. We assess the accuracy of diffierent DFT functionals (such as B3LYP, M06, MPWB1K, etc.) and diffierent basis sets, including both effective core potentials for Ni and the all electron basis sets for all other atoms in predicting the Ni-L BDE values reported recently by Nolan et al. [J. Am. Chem. Soc. 125, 10490 (2003) and Organometallics 27, 3181 (2008)]. It is found that the MPWB1K/LanL2DZ:6-31+G(d,p)//MPWB1K/LanL2DZ:6-31G(d) method gives the best correlations with the experimental results. Meanwhile, the solvent effect calculations (with CPCM, PCM, and SMD models) indicate that both CPCM and PCM perform well.     

Strong dependency of lithium diffusion on mechanical constraints in high-capacity Li-ion battery electrodes

The effect of external constraints on Li diffusion in high-capacity Li-ion battery electrodes is investigated us- ing a coupled finite deformation theory. It is found that thin- film electrodes on rigid substrates experience much slower diffusion rates compared with free-standing films with the same material properties and geometric dimensions. More importantly, the study reveals that mechanical driving forces tend to retard diffusion in highly-constrained thin films when lithiation-induced softening is considered, in contrast to the fact that mechanical driving forces always enhance diffusion when deformation is fully elastic. The results provide further proof that nano-particles are a better design option for next-generation alloy-based electrodes compared with thin films.     

The saturated five‐membered heterocyclic molecules as organic hydride donors: a computational study

Several five‐membered heterocyclic molecules were studied theoretically as organic hydride donors. The density functional theory and ab initio methods are employed to study the direct one‐step or multistep sequence suggested for the hydride transfer from the selected molecules: H atom/electron, electron/proton/electron or electron/H atom. Out of the three multistep mechanisms, electron/H atom seems to be a probable pathway in the presence of suitable catalyst/photoreaction that can cause ionization. In the lack of such catalyst/photoreaction, the direct hydride transfer seems to be most probable with the presence of suitable hydride acceptor. A detailed mechanism of the hydride transfer from the five‐membered heterocylic compounds is important in understanding chemical and biological reactions and required for scientifically designing and synthesizing new desired five‐membered heterocyclic compounds as organic hydride donor. Copyright © 2014 John Wiley & Sons, Ltd.     

Stable Cross‐linked Fluorescent Polymeric Nanoparticles for Cell Imaging

Aggregation‐induced emission (AIE) dye‐based cross‐linked fluorescent polymeric nanoparticles (FPNs) are facilely prepared via a two‐step polymerization process including emulsion polymerization and subsequent anhydride cross‐linking. Then, a variety of characterization methods are carried out to determine the performance of the FPNs, which show high dispersibility and strong fluorescence in an aqueous solution due to the hydrophilic carboxyl groups on the surfaces and the AIE components as the cores. Biocompatibility evaluation and cell imaging results suggest that these FPNs are biocompatible for cell imaging. More importantly, this cross‐linking strategy is proven to overcome the issue of critical micelle concentration and opens the opportunity to develop more robust fluorescent bioprobes.

     

The production of prop-2-ynylideneamine by thermolysis of N-chloropropargylamine,N-fluoropropargylamine and N-hydroxypropargylamine: a computational study

Ab initio molecular orbital calculations using MP2 and DFT/B3LYP methods at the 6-311++G(d,p) and aug-cc-pvdz basis sets were applied to characterise the kinetics of the thermal dissociation of HC≡CCH₂NHX [where X = OH(I), F(II) and Cl(III)] to produce Z- and E-prop-2-ynylideneamines (HC≡CCH=NH) (IV and V, respectively), which tautomerise to vinyl cyanide (CH₂=CHC≡N) (VI). The optimised geometries and electronic energies of reactants, transition states and products were estimated and discussed. A concerted proton migration and HX abstraction mechanism was proposed for the imine formation. The reliance of these properties on the elected levels of theory was discussed. The activation energies and barrier heights for the Z- and E-forms and their vinyl cyanide tautomers were estimated and analysed. The Z-form was computed to be more stable than the E-form. Using natural bond orbital calculations, the origin of the preference of the Z-form was attributed mainly to the N lone pair delocalisations. Vinyl cyanide was located to have a lower energy (33–35 kcal/mol) than prop-2-ynylideneamine. The provenance of the preference of the former and its tautomerisation mechanism will be addressed in a separate publication.     

Experimental investigation of light storage of diffraction-free and quasi-diffraction-free beams in hot atomic gas cell

In this article we report on the experimental investigation of light storage for several types of diffractionfree beams (Bessel and Airy beams) and quasi-diffraction-free beams by utilizing electromagnetically induced transparency (EIT) technique in a hot atomic gas cell. The experimental results show that the diffraction-free and quasi-diffraction-free beams have better storage performances when compared with ordinary images possessing similar spatial profiles. Meanwhile, the Bessel beams and the quasidiffraction-free images are able to maintain their spatial profiles with a long storage time while the sidelobes of the Airy beam are gradually depleted with the increment of the storage time. We quantitatively analyze the storage results and give physical explanations behind these phenomena. Furthermore, the self-healing of the retrieved diffraction-free beams is verified, signifying that their characteristics preserve well after storage.