A Pencil Graphite Electrode In Situ Modified by Monovalent Copper: a Promising Tool for the Determination of Methylxanthines

A pencil graphite electrode (PeGE) exhibits a promising tool for the electrochemical analysis of xanthine (Xan) and its N‐methyl derivatives (1‐, 3‐, 7‐ and 9‐mXan). The changes in their level in blood, serum, urine, as products of purine catabolism, can indicate the development of some diseases. Sensitivity‐enhanced voltammetric detection of mXans was achieved by forming of complex with Cu(I) and application of elimination procedure. The Cu(I)‐mXan complex was identified by means of titration of electrochemically produced cuprous ions by mXan. Our approach enables separation of overlapped mXan oxidation signals. Based on the obtained results, we found that the effect of methyl group position on the xanthine skeleton was significant and it was also discussed.     

Photo-induced ligand substitution at a remote site via electron transfer in a porphyrin-appended rhenium carbonyl supermolecule

The photochemical and electrochemical properties of a Zn-porphyrin appended rhenium(I) tricarbonyl bipyridine 3-Me-pyridine complex have been investigated; visible-light sensitisation of electron transfer results in ligand substitution at a site remote from the chromophore.     

A convenient route to diazepines by intramolecular cyclisation of carbonylazides

The appropriate substituted carbonylazides I treated with warm acetic acid give the corresponding acetamide IV or the cyclic lactam VI . This is a convenient route to 10,11-Dihydro-5H-pyrrolo[1,2-a][1,4]-benzodiazepin-11-one and 10,11-Dihydro-4H-thieno[2,3-e]pyrrolo[1,2-a][1,4]diazepin-10-one.     

Microscopy and single molecule detection in photosynthesis

Progress in various fields of microscopy techniques brought up enormous possibilities to study the photosynthesis down to the level of individual pigment-protein complexes. The aim of this review is to present recent developments in the photosynthesis research obtained using such highly advanced techniques. Three areas of microscopy techniques covering optical microscopy, electron microscopy and scanning probe microscopy are reviewed. Whereas the electron microscopy and scanning probe microscopy are used in photosynthesis mainly for structural studies of photosynthetic pigment-protein complexes, the optical microscopy is used also for functional studies.     

Response of a Si-diode-based device to fast neutrons

Semiconductor devices based on a Si-detector are frequently used for charged particle's detection; one application being in the investigation of cosmic radiation fields. From the spectra of energy deposition events in such devices, the total energy deposited by the radiation in silicon can be derived. This contribution presents the results of studies concerning the response of this type of detector to fast neutrons. First, the spectrum of energy deposition was established in fast neutron radiation fields with average energies from 0.5 to 50 MeV. It was found that these spectra vary significantly with the neutron energy. The comparison with the spectra registered in photon beams permitted an estimation of the part of energy deposited that could be attributed to neutrons. It was found that this part increases rapidly with neutron energy. The possibilities to use this type of detector for neutron detection and dosimetry for radiation protection are analysed and discussed.     

Monolithic columns with a gradient of functionalities prepared via photoinitiated grafting for separations using capillary electrochromatography

Stationary phases for capillary electrochromatography with a longitudinal gradient of functionalities have been prepared via photoinitiated grafting of polymer chains onto the pore surface of a porous polymer monolith. In order to achieve the desired retention and electroosmotic flow, the hydrophobic poly(butyl methacrylate-co-ethylene dimethacrylate) monolith with optimized porous properties was grafted with a layer of ionizable polymer, poly(2-acrylamido-2-methyl-1-propanesulfonic acid). A moving shutter and a neutral density filter were used to control the dose of UV light received at different locations along the monolith in order to create the longitudinal gradient of functionalities. Formation of the desired gradients was confirmed using electron probe microanalysis of different locations along the column. The preparation technique significantly affects performance in the CEC mode as demonstrated on the separations of a model mixture using columns both with homogeneous distribution of grafts and with a gradient of functionality. Columns grafted with the gradient of functionalities were found superior to those functionalized uniformly. A comparison of the performance of the gradient column with another containing evenly distributed functionalities showed the performance benefits of the "gradient" column.