Fully reversible procedure for silver staining improves densitometry of complex mixtures of biopolymers resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis

Due to its high sensitivity, silver staining is a widely popular method for the revelation of biopolymers separated by both native and denaturing electrophoresis. A step-by-step method for the destaining and restaining of overdeveloped/overloaded silver-stained bands is described that is applicable to both proteins and nucleic acids. The procedure significantly improves densitometric analysis of gels that have been silver stained with either commercial kits or solutions made in-house. The method permits reproducible densitometry of silver-stained gels and allows quantification of both main and minor components in complex mixture of molecules resolved on the same gel slab. All steps may be interrupted and are readily reversible, allowing for facile densitometric analyses and photographic recording under optimized conditions. Furthermore, common artifacts such as differential staining of the two gel surfaces, localized uneven yellow-ochre background, and the presence of fold marks and fingerprints can be easily removed.     

In Situ Study of the Solid-State Formation of U(1-x)Am(x)O(2±δ) Solid Solution

In order to reduce the nuclear waste inventory and radiotoxicity, U(1-x)Am(x)O(2±δ) materials are promising fuels for heterogeneous transmutation. In this context, they are generally fabricated from UO(2+δ) and AmO(2-δ) dioxide powders. In the subsequent solid solution, americium is assumed to be trivalent whereas uranium exhibits a mixed-valence (+IV/+V) state. However, no formation mechanisms were ever evidenced and, more particularly, it was not possible to know whether the reduction of Am(IV) to Am(III) occurs before the solid-solution formation, or only once it is established. In this study, we used high-temperature X-ray diffraction on a UO(2±δ)/AmO(2-δ) (15 mol?%) mixture to observe in situ the formation of the U(1-x)Am(x)O(2±δ) solid solution. We show that UO(2+δ) is, at relatively low temperature (<700 K), oxidized to U(4)O(9-δ), which is likely to be caused by oxygen release from the simultaneous AmO(2-δ) reduction to cubic Am(2)O(3±δ). Cubic Am(2)O(3+δ) then transforms to hexagonal Am(2)O(3) at 1300 K. Thus, the initial Am(IV) is fully reduced to Am(III) before the solid solution starts forming at 1740 K. The UO(2) fluorite phase vanishes after 4 h at 1970 K, indicating that the formation of the solid solution is completed, which proves that this solid solution is formed after the complete reduction of Am(IV) to Am(III).     

The SAMBA quick‐EXAFS monochromator: XAS with edge jumping

Results and performances of the QEXAFS double monochromator of the SAMBA beamline (Synchrotron SOLEIL) are presented. The device is capable of speeds of up to 40 Hz, while giving the user the possibility to choose the amplitude of the scan from 0.1° to 4° in a few seconds. The device is composed of two independent units and it is possible to perform scans alternating between two different crystals, literally jumping from low (4 keV) to high (37 keV) energies.     

Self-assembly of soluble anthracene, tetracene and pentacene derivatives

New soluble disubstituted acenes (tetracene, pentacene) have been designed in order to mimic 2,3-alkoxy derivatives of anthracene. They have been shown to self-assemble and gellify a large variety of organic solvents. This process involves the formation of nano-fibres through non-covalent molecular interactions (van der Waals, π-π stacking), weaving a three-dimensional supramolecular network. Efficient transfer of excitation energy through these nano-structures has been evidenced in an anthracene light-harvesting matrix doped with less than 1 mol% of a tetracene energy trap.     

Direct formation of fullerene monolayers using [4+2] Diels-Alder cycloaddition

The formation of covalent C(60) monolayers through [4+2] Diels-Alder cycloaddition between C(60) and anthracene monolayers grafted onto a silicon oxide surface was investigated by ellipsometry, fluorescence and by atomic force microscopy.     

Metal Analyses in Environmental and Pharmaceutical Samples by Capillary Electrophoresis with Methyl 3‐Amino‐3‐(pyridin‐3‐yl)propanoate Dihydrochloride as a New Ion‐Pairing Reagent

Separation and determination of some common metal ions was achieved with methyl 3‐amino‐3‐(pyridin‐3‐yl)propanoate dihydrochloride (MAPP) as an ion‐pairing reagent and pyridine as a detectable counter‐ion for indirect UV detection at 254 nm. The effects of the complexing reagent and chromophore concentrations, applied voltage, and organic solvent content on the separation were investigated. The optimized separation was carried out in a running electrolyte containing 16 mM MAPP and 20 mM pyridine at pH 4.0 and was successfully applied to the qualitative and quantitative analysis of Li⁺, Na⁺, Mg²⁺, Ca²⁺, Ba²⁺, Ni²⁺, and Zn²⁺ in pharmaceutical vitamin preparations and various water samples.     

Single-pulse KrF laser ablation and nanopatterning in vacuum of β-titanium alloys used in biomedical applications

We report the KrF laser (248 nm) nanosecond single-pulse irradiation in vacuum of a mirror-polished surface of a model -titanium alloy. A series of single-pulse laser-annealing experiments is performed with increasing fluence adjusted to obtain conditions from submelting (a few mJ/cm²) up to intense laser ablation (30 J/cm²). The structural and morphological changes are followed by atomic force microscopy and scanning electron microscopy, as well as with other analytical techniques, and compared with the starting equilibrium mixture of the untreated sample. The results are discussed and related to the theoretical estimation of fluences corresponding to the -transus, melting, boiling and intense ablation (phase-explosion) thresholds as well as to the estimates of melt depth and lifetime evaluation as a function of fluence. By carrying out laser annealing in vacuum the surface oxidation is avoided while roughening and phase transformations are favoured within the laser-heated depth. The mirror-polished starting surface is composed of nanometric -precipitates embedded in a -matrix, whose surface is systematically 5–10 nm above the -surface. Upon laser annealing with increasing fluence the -nanocrystals transform progressively into -phase, resulting in an increasing relief. At higher fluence the conditions for increasing roughness are studied. Submicrometre roughness is expected to improve cell adhesion to -titanium alloys and hence osteointegration. PACS 81.05.-t; 68.37.Ps; 68.55.Jk