A simple dot-blot–Sirius red-based assay for collagen quantification

The assessment of collagen content in tissues is important in biomedical research, since this protein is altered in numerous diseases. Hydroxyproline and Sirius red based assays are the most common methods for collagen quantification. However, these procedures have some pitfalls, such as the requirement of oxygen-free medium or expensive equipment and large sample size or being unsuitable for hydrolyzed collagen, respectively. Our objective was to develop a specific, versatile, and user-friendly quantitative method applicable to small tissue samples and extracts obtained from elastin purification, therefore, suitable for simultaneous quantification of elastin. This method is based on the binding of Sirius red to collagen present in a sample immobilized on a PVDF membrane, as in the dot-blot technique, and quantified by a scanner and image analysis software. Sample loading, Sirius red concentration, temperature and incubation time, type of standard substance, albumin interference, and quantification time are optimized. The method enabled the quantification of (1) intact collagen in several rat tissue homogenates, including small resistance-sized arteries, (2) partially hydrolyzed collagen obtained from NaOH extracts, compatible with elastin purification, and (3) for the detection of differences in collagen content between hypertensive and normotensive rats. We conclude that the developed technique can be widely used since it is versatile (quantifies intact and hydrolyzed collagen), requires small sample volumes, is user-friendly (low-cost, easy to use, minimum toxic materials, and reduced time of test), and is specific (minimal interference with serum albumin).

Nonsmooth Lur’e Dynamical Systems in Hilbert Spaces

In this paper, we study the well-posedness and stability analysis of set-valued Lur’e dynamical systems in infinite-dimensional Hilbert spaces. The existence and uniqueness results are established under the so-called passivity condition. Our approach uses a regularization procedure for the term involving the maximal monotone operator. The Lyapunov stability as well as the invariance properties are considered in detail. In addition, we give some sufficient conditions ensuring the robust stability of the system in finite-dimensional spaces. The theoretical developments are illustrated by means of two examples dealing with nonregular electrical circuits and an other one in partial differential equations. Our methodology is based on tools from set-valued and variational analysis.     

Synthesis, characterization and activity in cyclohexene epoxidation of V2O5–TiO2 anatase xerogel

The system of V₂O₅?CTiO₂ catalysts with V₂O₅ contents from 5 to 20 wt% were prepared by the sol?Cgel route and calcined at 500?°C. The mixed oxide series presented the crystalline structure of TiO₂ anatase phase. BET analysis showed a medium surface area decreasing from 73 to 19?m² g^?1 when V₂O₅ content rose from 5 to 20 wt%. The results of pyridine adsorption followed by FT-IR indicate that the catalysts display identical surface acid densities, independently of the V₂O₅ content, and both Br?nsted and Lewis acid sites are present on their surfaces. The V₂O₅ system presents an activity and selectivity during the cyclohexene oxidation reaction. The presence of V₂O₅ increases the catalyst efficiency and leads to a selectivity change from cyclohexenol (blank test) to epoxide, with a maximum for 15 wt% V₂O₅. The conversion of cyclohexene was 46?% while the selectivity to epoxide was higher (75?%).     

Theoretical determination of the favorable mechanism of the reaction between AlX and HX (X = Br, Cl, and F)

The reaction mechanism between AlX and HX (X = Br, Cl, and F) have been characterized in detail using DFT as well as the ab initio method. The reaction yielding AlX₃ and molecular hydrogen was calculated to be highly exothermic. The present calculations also show that the possible routes to the trihalides species start more favorable with the primary insertion product AlX₂H than with the biadduct AlX(HX)₂ one.      

Mode coherence measurements across a 1.5 THz spectral bandwidth of a passively mode-locked quantum dash laser

The mode coherence of adjacent and non-adjacent spectral modes of a passively mode locked quantum dash (QDash) semiconductor laser are deduced through radio frequency beat-tone linewidth measurements. A wavelength conversion scheme that uses degenerate four wave mixing in a semiconductor optical amplifier is proposed which considerably extends the mode spacing beyond the limit imposed by conventional fast-photodetection and electrical spectrum analysis of around 100 GHz. Using this scheme, the mode coherence of the QDash laser was measured out to the thirty-first harmonic, or a mode separation of 1.5 THz.     

ChemInform Abstract: G2(MP2) Molecular Orbital Study of [H3AlXH3]‐ (X: C,Si, and Ge) and H3AlYH3 (Y: N,P, and As) Complexes.

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