Peptide and protein separations by capillary electrophoresis in the presence of mono- and diquaternarized diamines

Two compounds, derivatives of 1,4-diazobicyclo[2,2,2]octane (DABCO), have been evaluated as potential quenchers of silanol interactions with peptides and proteins during their capillary zone electrophoresis (CZE) separations. They are: 1-(4-iodobutyl)4-aza-1-azoniabicyclo[2,2,2]octane iodide (M7C4I) and 1,4-didecyl-1,4-diazoniabicyclo [2,2,2]octane dibromide (C10M7C10). The first compound is known to react with the wall, by forming a covalent bond via alkylation of silanols. On the contrary, the second one (C10M7C10) can only loosely interact with silica due to lack of reactive iodine and to a much too short distance (a C(2)) between the two quaternary nitrogens. Very good peptide maps of protein digests can be obtained in isoelectric glutamic acid (Glu) buffer, at pH 3.52 by utilizing the M7C4I. However, in the case of total tissue extracts, excellent resolution is obtained only with the first eluting part of the analyte spectrum (i.e., peptides and smaller proteins). With larger proteins, interaction with the wall and loss of resolution is experienced. When using the C10M7C10, good resolution of di- and tripeptides is obtained, while a loss of resolution is observed with entire protein digest. M7C4I does not seem to interact with the peptide/protein analytes, and simply repels them from the wall via its positive charges; it is believed that disalt (C10M7C10) acts by interacting with the same compounds, possibly by forming micelles in solution.     

Curving Newtonian Space

We show that the advance of the perihelion of Mercury (and other planets), as well as the deflection of light by the Sun, can be accurately calculated in Newtonian gravity, if one takes into account the fact of the curvature of space.     

Digital simulation of electrochemical processes involving very fast chemical reactions : Part 1. A simple general approach

A simple approach based on the steady-state assumption and linear concentration profiles in the reaction layer is proposed to simulate electrochemical systems involving very fast homogeneous chemical reactions. The flux equations are derived in detail and the method is shown to be suitable for catalytic e.c.e and dimerization reaction mechanism. The accuracy of the proposed method is checked by comparing the results obtained with those already available in the literature.     

Description and validation of an analytical method for the determination of paromomycin sulfate in medicated animal feeds

A procedure for the extraction of paromomycin from different animal feed matrices (rabbit, chicken, pig feeds) and its subsequent determination via a reversed-phase ion-pair HPLC separation coupled with pulsed amperometric detection is described. The procedure optimised in terms of the extracting solvent and the solid phase extraction stationary phase allows the total recovery of the aminoglycoside antibiotic. The criteria used for the validation of the analytical method applied to the cited matrices are the linear dynamic range of the response, the detection limit, the repeatability, the intermediate repeatability and the accuracy. A comparison with a method described in the literature for the bulk analysis of this antibiotic is made.     

Microemulsions as reaction media for the synthesis of Pt nanoparticles

For the synthesis of Pt nanoparticles we used water-in-oil droplet microemulsions as templates. The focus was on the correlation between the size of the microemulsion droplets and that of the resulting Pt particles. To study this correlation in a systematic way, all particles were synthesized at the water emulsification failure boundaries where the microemulsion droplets are spherical and where their size can easily be tuned by the amount of added water. The metallic particles were synthesized by mixing two microemulsions one of which contains the metal salt H(2)PtCl(6) and the other the reducing agent NaBH(4). The size and structure of the microemulsion droplets was studied via small-angle X-ray scattering, while the Pt particles were characterized by high-resolution transmission electron microscopy in combination with energy-dispersive X-ray spectroscopy and selected area electron diffraction. The clear correlation between droplet and particle size was further supported by accompanying Monte Carlo simulations.     

A DFT study on a calix[5]crown-based heteroditopic receptor

The structures and binding energies of complexes formed between tris-ureido-calix[5]crown 1 and n- and 2-phenylethylammonium chloride have been determined by density functional calculations. Density functional theory analysis shows that the heteroditopic receptor 1 binds organic salt species with positive cooperativity.     

Synthesis of Indenes via Graphene Oxide Mediated Manipulation of Morita-Baylis-Hillman Alcohols

A new metal-free synthetic approach to functionalized indenes is documented. The use of commercially available graphene oxide (GO) allowed the direct access to indenyl cores (yield up to 80 %) via intramolecular Friedel-Crafts-type allylic alkylations with readily available Morita-Baylis-Hillman alcohols. Combined experimental and spectroscopic investigations contributed to shed light on the reaction mechanism dealing with a nanostructured carbon material-based C−C bond forming reaction.     

Insertion of Copper(II)/Schiff‐Base Complexes with NLO Properties into Commercial Polycarbonates by Thermal Processes

The preparation of a bisphenol‐A carbonate copolymer, containing Cu‐diimine units with nonlinear optical (NLO) properties, and its MALDI‐TOF mass spectrometric characterization are reported. Contrary to the usual synthetic method, NLO groups were inserted directly into a commercial polycarbonate by prolonged heating at 250 °C. This innovative procedure allows to obtain a Cu/diimine‐containing polymer of high molecular weight.

     

Si-Tethered Bis- and Tris-Malonates for the Regioselective Preparation of Fullerene Multi-Adducts

Bis- and tris-malonates constructed around a silicon atom have been prepared by reaction of malonate derivatives bearing an alcohol function with di-tert-butylsilyl bis(trifluoromethanesulfonate) and tert-butyl(trichloro)silane, respectively. These compounds have been used for the regioselective bis- and tris-functionalization of C₆₀ under Bingel conditions. By changing the nature of the linker between the central Si atom and the reactive malonate groups, the malonate precursors have been optimized to produce specific bis- and tris-adducts with excellent regioselectivity. A complete understanding of the electronic and stereochemical factors governing the regioselectivity has been obtained by combining computational studies with a complete analysis of the by-products formed during the reactions of the Si-tethered tris-malonates with C₆₀. Finally, desilylation reactions of the resulting fullerene bis- and tris-adducts have been carried out to generate the corresponding acyclic fullerene bis- and tris-adducts bearing alcohol functions.