Diagonal chromatographic selection of cysteinyl peptides modified with benzoquinones

The derivatization of cysteine-containing peptides with benzoquinone compounds is rapid, quantitative and specific in acidic media. The conversion of cysteines into hydrophobic benzoquinone-adducted residues in peptides is used here to alter the chromatographic properties of cysteinyl peptides during liquid chromatography separation. The benzoquinone derivatization is shown to allow the accurate selection of cysteine-containing peptides of bovine serum albumin tryptic digest by diagonal reversed-phase chromatography, which consists of one primary and a series of secondary identical liquid chromatographic separations, before and after a cysteinyl-targeted modification of the peptides by benzoquinone compounds. Figure Diagonal chromatographic selection of cysteinyl peptides modified with benzoquinone

On-line electrogeneration of copper-peptide complexes in microspray mass spectrometry

The interaction of copper ions with peptides was investigated by electrospray mass spectrometry. Two electrospray micro-emitters were compared, the first one with a platinum electrode using a copper(II) electrolyte solution containing a peptide sample, and the second one with a sacrificial copper anode in a water/methanol solution containing only a peptide (i.e., angiotensin III, bradykinin, or Leu-enkephalin). The former yielded mainly Cu2+ complexes either with histidine residues or with the peptide backbone (Cu+ complexes can be also formed due to gas-phase reactions), whereas the latter can generate a mixture of both Cu+ and Cu2+ aqueous complexes that yield different complexation patterns. This study shows that electrospray emitters with soluble copper anodes enable the study of Cu(I)-peptide complexes in solutio

Bubble cell for magnetic bead trapping in capillary electrophoresis

A bubble cell capillary classically used to extend the optical path length for UV-vis detection is employed here to trap magnetic beads. With this system, a large amount of beads can be captured without inducing a strong pressure drop, as it is the case with magnetic beads trapped in a standard capillary, thereby having less effect on the experimental conditions. Using numerical simulations and microscopic visualizations, the capture of beads inside a bubble cell was investigated with two magnet configurations. Pressure-driven and electro-osmotic flow velocities were measured for different amounts of protein-A-coated beads or C18-functionalized beads (RPC-18). Solid-phase extraction of a model antibody on protein-A beads and preconcentration of fluorescein on RPC-18 beads were performed as proof of concept experiments. Figure Isovalues of the magnetic induction produced by two permanent magnets in attraction configuration with a capillary placed between the

Non-Precious Electrodes for Practical Alkaline Water Electrolysis

Water electrolysis is a promising approach to hydrogen production from renewable energy sources. Alkaline water electrolyzers allow using non-noble and low cost materials. An analysis of common assumptions and experimental conditions (low concentrations, low temperature, low current densities and short-term experiments) found in the literature is reported. The steps to estimate the reaction overpotentials for hydrogen and oxygen reaction are reported and discussed. The results of some of the most investigated electrocatalysts, namely from the iron group elements (iron, nickel and cobalt) and chromium are reported. Past findings and recent progress in the development of efficient anode and cathode materials appropriate for large-scale water electrolysis are presented. The experimental work is done involving the direct-current electrolysis of highly concentrated potassium hydroxide solutions at temperatures between 30 and 100°C which are closer to industrial applications than what usually found in literature. Stable cell components and a good performance was achieved using as a cathode Raney nickel and stainless steel 316L as an anode by means of a monopolar cell at 75°C which ran for one month at 300 mA cm?2. Finally, the proposed catalysts show a total kinetic overpotential of circa 550 mV at 75 °C and 1 A cm?2.Fil: Colli, Alejandro Nicolás. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; ArgentinaFil: Girault, Hubert. Ecole Polytechnique Federale de Lausanne; FranciaFil: Battistel, Alberto. Ecole Polytechnique Federale de Lausanne; Franci

Molecular electrocatalysis at soft interfaces

The fundamental aspects of electrochemistry at liquid–liquid interfaces are introduced to present the concept of molecular electrocatalysis. Here, a molecular catalyst is adsorbed at the interface to promote a proton coupled electron transfer reaction such as hydrogen evolution or oxygen reduction using lipophilic electron donors

Dual-Channel Electrospray Microchip

A dual-channel electrospray microchip has been developed for electrospray ionization mass spectrometry (ESI-MS) where aqueous samples are mixed at the Taylor cone with an organic buffer. Due to the fast and effective mixing in the Taylor cone, the aqueous sample can be well ionized with a high ion intensity. The influence of geometric parameters such as the distance between the two microchannels at their junction at the tip of the emitter has been investigated together with chemical parameters such as the organic buffer compositio