Rates of intra- and intermolecular electron transfers in hydrogenase deduced from steady-state activity measurements

Electrons are transferred over long distances along chains of FeS clusters in hydrogenases, mitochondrial complexes, and many other respiratory enzymes. It is usually presumed that electron transfer is fast in these systems, despite the fact that there has been no direct measurement of rates of FeS-to-FeS electron transfer in any respiratory enzyme. In this context, we propose and apply to NiFe hydrogenase an original strategy that consists of quantitatively interpreting the variations of steady-state activity that result from changing the nature of the FeS clusters which connect the active site to the redox partner, and/or the nature of the redox partner. Rates of intra- and intermolecular electron transfer are deduced from such large data sets. The mutation-induced variations of electron transfer rates cannot be explained by changes in intercenter distances and reduction potentials. This establishes that FeS-to-FeS rate constants are extremely sensitive to the nature and coordination of the centers.     

Examination of Template Structural Effects on CEC Chiral Separation Performance of Molecule Imprinted Polymers Made by a Generalized Preparation Protocol

Some acidic chiral templates were used to prepare open tubular (OT) molecule imprinted polymer (MIP) capillary columns to explore the effects of molecular structures of templates on chiral recognition capabilities and to verify the feasibility of the general MIP preparation protocol introduced in the previous study. The templates are phenyl carboxylic acids and their derivatives. Optimization was carried out for chiral separation of template enantiomers for each MIP column through varying pH and composition of eluent. It was found that the preparation protocol can be successfully applied for the appropriate templates with functional groups fulfilling the three-points interaction rule. The chiral separation performances were quite satisfactory for MIPs of such templates although they are yet inferior to the separation performances of the MIP columns fabricated with the templates of profen drugs (2-arylpropionic acids with a large substituent on the phenyl ring). Subtle variations of the template molecular structures have been found to be critical to enhance chiral recognition ability of the resultant MIP column.     

Theoretical study with vibration–rotation and dipole moment calculations of quartet states of the CrCl molecule

The potential energy curves have been investigated for the 10 lowest quartet electronic states in the ^2s+1Λ^± representation below 30,000 cm^?1 of the molecule CrCl via CASSCF and MRCI (singly and doubly excitation with Davidson correction) calculations. The harmonic frequency ω_e, the internuclear distance r_e, the rotational constant B_e, the electronic energy with respect to the ground state T_e, and the permanent dipole moment μ have been calculated. By using the canonical functions approach, the eigenvalues E_v, the rotational constant B_v, and the abscissas of the turning points r_min and r_max have been calculated for the considered electronic states up to the vibrational level v = 19. Seven electronic states have been studied here theoretically for the first time. The comparison of these values to the theoretical results available in the literature shows a good agreement. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Experimental analysis on vortex tube energy separation performance

The present study reports the effect of several operating parameters on the thermal performance of the vortex tube. The experimental results indicate that the inlet pressure and the cold fraction are the most significant parameters influencing the vortex tube performance. The experimental data point out that insulation has minimal effect on the vortex tube performance. The same inlet pressure tests show that energy separation increases as number of inlet nozzle increases.     

An Identification Problem for First-Order Degenerate Differential Equations

We study a first-order identification problem in a Banach space. We discuss the nondegenerate and mainly the degenerate case. As a first step, suitable hypotheses on the involved closed linear operators are made in order to obtain unique solvability after reduction to a nondegenerate case; the general case is then handled with the help of new results on convolutions. Some applications to partial differential equations motivate this abstract approach.Communicated by I. GalliganiWork partially supported by MIUR (Ministero dell’ Istruzione, dell’ Università e dalla Ricerca), Project PRIN 2004011204 “Analisi Matematica nei Problemi Inversi,” and by the University of Bologna Funds for Selected Research Topics.     

The influence of nonuniform coating and taylor dispersion on the evaluation of capillary column inverse gas chromatography

A mathematical model which takes into account the combined effect of Taylor dispersion and film eccentricity on the elution profiles has been developed for the analysis of a capillary column inverse gas chromatography (CCIGC) experiment. In this paper, we present an additional improvement on the model presented by Hamdan et al. [E. Hamdan, J. F. Milthorpe, J. C. S. Lai, J. Chromatogr. A, 1078 (2005) 144] to include the effect of coating nonuniformity. The new model shows that while Taylor dispersion effect has a very significant effect on the elution profiles at low values of beta and gamma, the general effect of film asymmetry is to reduce this effect. At sufficiently large gamma and/or beta values, Taylor dispersion effect becomes negligible and the elution profiles will be mainly affected by film asymmetry. The inclusion of Taylor dispersion effect will increase the variance of the elution curves which could significantly affect the estimated value of the diffusivity Dp. The error in the estimated Dp values obtained using the Pawlisch et al. [C. A. Pawlisch, J. R. Bric, R.L. Laurence, Macromolecules 21 (1988) 1685] nonuniform model increases as gamma and/or beta are reduced and when the coated polymer exhibits less deviation from uniform films.     

Photo-physical properties and amplified spontaneous emission of a new derivative of fluorescein

The synthesis of new high-performance dyes and the implementation of new ways of incorporating the organic molecules into the solid host matrices have produced a great deal of activity in the field of solid-state dye lasers. In this article, the new laser dye, 2-(6-allyl-3-oxo-3H-xanthen-9-yl)-benzoic acid ethyl ester [AXBE] has been synthesized, and its chemical structure was confirmed by ¹H NMR, ¹³C NMR, IR and elemental analysis. This new dye was covalently bonded with methyl methacrylate (MMA) and 2-hydroxy ethyl methacrylate (HEMA) copolymer backbone and evaluated as the active medium of the solid-state laser dye. Its optical properties were experimentally investigated. Amplified spontaneous emission (ASE) and photostability were studied by pumping the dye sample with 355 nm (8 ns) pulsed Nd-YAG laser.     

Cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction and HPLC–DAD analysis of ezetimibe and simvastatin in human plasma and urine

A new cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction (CA–HF–SLPME) followed by high‐performance liquid chromatography–diode array detection (HPLC–DAD) method was developed for simultaneous determination of ezetimibe and simvastatin in human plasma and urine samples. To prepare the CA–HF–SLPME device, the cetyl‐alcohol was immobilized into the pores of a 2.5 cm hollow fiber micro‐tube and the lumen of the micro‐tube was filled with 1‐octanol with the two ends sealed. Afterwards, the prepared device was introduced into 10 mL of the sample solution containing the analytes with agitation. Under optimized conditions, calibration curves plotted in spiked plasma and urine samples were linear in the ranges of 0.363–25/0.49–25 μg L^?1 for ezetimibe/simvastatin and 0.193–25/0.312–25 μg L^?1 for ezetimibe/simvastatin in plasma and urine samples, respectively. The limit of detection was 0.109/0.174 μg L^?1 for ezetimibe/simvastatin in plasma and 0.058/0.093 μg L^?1 for ezetimibe/simvastatin in urine. As a potential application, the proposed method was applied to determine the concentration of selected analytes in patient plasma and urine samples after medication and satisfactory results were achieved. In comparison with reference methods, the CA–HF–SLPME–HPLC–DAD method demonstrates considerable potential in the biopharmaceutical analysis of selected drugs.     

In vitro evaluation of potential complexation between bovine insulin and bovine serum albumin

The objective of this study was to examine the possible binding of bovine insulin (BI) with bovine serum albumin (BSA) to form a new potential diabetogenic irreversible complex protein. Several preparations of BSA and BI were prepared. Both capillary electrophoresis and spectrophotometric analysis were undertaken to test the possibility of complexation between BI and BSA. HPLC was used to test whether the potential complex of BI and BSA is reversible or irreversible. The optimum deviation between the real and calculated absorbances was observed at a BI/BSA ratio of 2. Moreover, the migration time of BI decreased substantially with increasing ratio of BI to BSA until it became almost constant at equal molar ratio of BI/BSA. While the majority of the 2:1 BI–BSA sample detached during the HPLC analysis, which confirms the reversible character of BI–BSA binding, the HPLC chromatogram also emphasizes the formation of an irreversible complexation between the two proteins. This study provides evidence of the formation of reversible and irreversible new BI–BSA complexes under physiological conditions. This highlights the importance of examining the possible diabetogenicity of BI–BSA complex in genetically susceptible people. Copyright © 2013 John Wiley & Sons, Ltd.     

Dispersion of polymeric-coated–silica aerogel particles in unsaturated polyester composites: Effects on thermal-mechanical properties

The thermal-mechanical properties of unsaturated polyester (UP) composite were enhanced by the dispersion of silica aerogel (SA) with preserved pores. Low-cost SA was prepared from rice husk via the sol-gel process and ambient pressure drying. A new method was proposed to encapsulate the hydrophobic aerogel surface pores with hydrophilic polyvinyl alcohol (PVA) film using the fluidized-bed coating process. The dispersion of PVA-coated aerogel with preserved pores in the polyester matrix resulted in an increase of specific compressive strength (44.1?MPa?·?cm³?g^?1), thermal insulation (0.23?W?m^?1?K^?1), and thermal stability (T_onset?=?310°C), but decreased the glass transition temperature (T_g?=?260°C).