Controlled formation of peptide bonds in the gas phase

Photoexcitation (using 157 nm vacuum ultraviolet radiation) of proton-bound peptide complexes leads to water elimination and the formation of longer amino acid chains. Thus, it appears that proton-bound dimers are long-lived intermediates along the pathway to peptide formation. Product specificity can be controlled by selection of specific complexes and the incorporation of blocking groups at the N- or C-termini. The product peptide sequences are confirmed using collision-induced dissociation.     

Mechanistic study of palladium catalyzed S-S and Se-Se bonds addition to alkynes

The mechanistic study of palladium catalyzed S-S and Se-Se bonds addition to alkynes revealed the involvement of dinuclear transition metal complexes in the catalytic cycle. Coordination of alkyne to dinuclear transition metal complex was found to be the rate determining step of the reaction. An unusual phosphine ligand effect increasing the yield of addition reaction was found in the studied system. A new synthetic procedure was developed to perform the catalytic reaction using easily available Pd(II) complex. The scope of the reaction and the reactivity of S-S and Se-Se bonds toward alkynes were investigated. The X-ray structure of the product of S-S bond addition reaction showed favorable geometry for the possible application as a chelate ligand.     

Simulation in Micro-Computers

Visual colour simulation development on APPLE computers is described in the context of a project to assess an expensive capital installation. The project was successful and showed the value and power of graphics on cheap computers when attention is paid to correct programme design. Emphasis is laid on rapid working, portability and the removal of communication barriers between analyst and management.     

Parametric inference for discrete observations of diffusion processes with mixed effects

Stochastic differential equations with mixed effects provide means to model intra-individual and inter-individual variability in repeated experiments leading to longitudinal data. We consider N i.i.d. stochastic processes defined by a stochastic differential equation with linear mixed effects which are discretely observed. We study a parametric framework with distributions leading to explicit approximate likelihood functions and investigate the asymptotic behavior of estimators under the asymptotic framework : the number N of individuals (trajectories) and the number n of observations per individual tend to infinity within a fixed time interval. The estimation method is assessed on simulated data for various models.     

PASE synthesis of 1-azolyl-1H-1,2,4-triazoles by the reaction of diazoazoles with ethyl isocyanoacetate

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Introducing tox-Profiles of Chemical Reactions

In this Essay, we present a critical analysis of two common practices in modern chemistry—that is, of using speculations about the “greenness” and “nontoxicity” of developed synthesis procedures and of a priori labelling various compounds derived from natural sources as being environmentally safe. We note that every organic molecule that contains functional groups should be biologically active. Thus, analysis of the particular greenness and the potential environmental impact of a given chemical process should account for the biological activity of all its components in a measureable (rather than empirical) way. We highlight the necessity of clarifying discussions on biological activity and toxicity and propose possible ways of introducing tox-Profiles as a reliable overview of the overall toxicity of chemical reactions.