Vibrational spectra of benzophenone conformers

We have used direct quantum DFT methods to calculate the parameters of the adiabatic potential of four benzophenone conformers. According to the data obtained, the existence of only one conformer is possible (C₁ symmetry) for the free benzophenone molecule, for which torsional vibrations of the benzene moieties are reproduced and for which we calculated the vibrational spectrum in the anharmonic approximation of the theory of molecular vibrations. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 561–564, September–October, 2007.     

Effect of junction constraints on rubber elasticity in multiaxial states of stress

The strains obtained in an amorphous polymer network subject to multiaxial states of stress are calculated according to a recent molecular theory which takes account of constraints on junctions in real networks. Experimental measurements for biaxial states of stress, for pure shear superposed on tension, and for combined torsion and simple extension, are seen to compare favorably with the predictions of the theory.     

Palladium-catalyzed alkoxycarbonylation of (Z)-2-en-4-yn carbonates leading to 2,3,5-trienoates

Pd(0)-catalyzed carbonylation of (Z)-2-en-4-yn carbonates in the presence of a balloon pressure of CO in an alcohol donates vinylallenyl esters with an exclusively E-configuration and in high yields. The fact that no such reactivity could be observed with E-configured enyne carbonates may indicate that the reaction is promoted via the cooperative coordination of palladium with both alkynyl and carbonate moieties.     

Design parameter investigation of industrial size ultrasound textile treatment bath

Design requirements for industrial size ultrasound bath for textile treatments have been determined. For this purpose, effects of sound pressure level, bath temperature, bath volume, textile material type and hydrophility degree of fabric were examined extensively. Finite element analysis (FEA) was used to investigate spacing and alignment of the ultrasound source transducers to reach effective and homogenous acoustic pressure distribution in the bath. It was found that textile material type, bath temperature and volume led to significant changes at sound pressure level. These parameters should be taken into consideration in designing of industrial size ultrasound bath for textile treatments. Besides, wettability of textiles is highly dependent to the distance from the transducers.     

The elastic net algorithm and protein structure prediction

Predicting protein structures from their amino acid sequences is a problem of global optimization. Global optima (native structures) are often sought using stochastic sampling methods such as Monte Carlo or molecular dynamics, but these methods are slow. In contrast, there are fast deterministic methods that find near-optimal solutions of well-known global optimization problems such as the traveling salesman problem (TSP). But fast TSP strategies have yet to be applied to protein folding, because of fundamental differences in the two types of problems. Here, we show how protein folding can be framed in terms of the TSP, to which we apply a variation of the Durbin-Willshaw elastic net optimization strategy. We illustrate using a simple model of proteins with database-derived statistical potentials and predicted secondary structure restraints. This optimization strategy can be applied to many different models and potential functions, and can readily incorporate experimental restraint information. It is also fast; with the simple model used here, the method finds structures that are within 5-6 A all-Calpha-atom RMSD of the known native structures for 40-mers in about 8 s on a PC; 100-mers take about 20 s. The computer time tau scales as tau approximately n, where n is the number of amino acids. This method may prove to be useful for structure refinement and prediction.     

Effect of high hydrostatic pressure and high dynamic pressure on stability and rheological properties of model oil-in-water emulsions

Both static and dynamic high pressure applications provide interesting modifications in food structures which lead to new product formulations. In this study, the effects of two different treatments, high hydrostatic pressure (HHP) and high dynamic pressure (HDP), on oil-in-water emulsions were identified and compared. Microfluidization was selected from among the HDP homogenization techniques. The performance of each process was analyzed in terms of rheological modifications and emulsion stability improvements compared with the coarse emulsions. The stability of the emulsions was determined comparatively by using an analytical photo-centrifuge device employing novel analysis technology. Whey protein isolate (WPI) in combination with a food polysaccharide (xanthan gum, guar gum or locust bean gum) were used as emulsifying and stabilizing ingredients. The effective disruption of oil droplets and the degradation of polysaccharides by the shear forces under high pressure in HDP microfluidization yielded finer emulsions with lower viscosities, leading to distinctive improvements in emulsion stability. On the other hand, improvements in stability obtained with HHP treatment were due to the thickening of the emulsions mainly induced by protein unfolding. The corresponding increases in viscosity were intensified in emulsion formulations containing higher oil content. Apart from these, HHP treatment was found to be relatively more contributive to the enhancements in viscoelastic properties.     

Moduli of model elastomeric networks prepared from polymer chains having a high plateau modulus,and their interpretation in terms of the constrained-chain model

High-molecular weight polybutadiene chains having approximately 47% cis-1,4 units and 45% trans-1,4 units were crosslinked through their carbon-carbon double bonds using p-bis(dimethylsilyl) benzene as crosslinking agent and chloroplatinic acid as catalyst. This particular polymer was chosen because the high plateau modulus it exhibits in the un-crosslinked state is taken to indicate large numbers of chain entanglements, and stress–strain measurements on such networks have frequently been interpreted with the assumption that the trapping of such entanglements during crosslinking should contribute significantly to their modull. It is shown in the present investigation that such results are equally well interpreted in terms of the new constrained-chain theory of rubbery elasticity. © 1993 John Wiley & Sons, Inc.     

Biogels of cytochrome c : Cytochrome c peroxidase complex studied by electron paramagnetic resonance spectroscopy

Cytochrome c: cytochrome c peroxidase (Cc: CcP in 1: 1 ratio) complex was successfully encapsulated in sol-gel derived glass. The electron paramagnetic resonance (e.p.r.) and optical absorption techniques were used to characterize the coordination number, spin state, charge-transfer activity and structural orientation of Cc: CcP complex and its constituents. The sol-gel encapsulation of metalloproteins allows, for the first time, the detection of e.p.r. signals of biological systems at room temperature. CcP exhibits an e.p.r. spectrum representing the high spin and purely axial symmetry with parameters at g 6 and g 2 and an electronic absorption spectrum with a descent in spectral intensity of shoulder band at 380 nm and a blue-shifted charge-transfer band at 620 nm. Cc shows an e.p.r. spectrum characterizing a mixture of high spin (g 6 and g 2) and low spin (g _x=2.7, g _y=2.2 and g _z=1.8) components. Upon complexation, Cc:CcP pair displays a single and broad e.p.r. spectrum at g 2 and a light absorption spectrum with a red-shifted Soret band at 423 nm, a blue-shifted charge-transfer band at 620 nm and an intensified charge-transfer band at 507 nm. These results suggest that the sol-gel encapsulated Cc:CcP complex has the following chemical and physical characteristics: (a) a hexa-coordination, (b) a high-spin state, (c) an active charge-transfer (or redox) pair, and (d) the direction of the g paramagnetic center of Cc : CcP complex lies nearly parallel to that of the heme normal. The structural coordinations of the sol-gel encapsulated Cc, CcP and Cc : CcP are examined. Moreover, the possible use of biogels at the sol, gelation, and xerogel stages during gel processing to control the structural rigidity and spatial separation/orientation of the encapsulated heme proteins and to study their possible routes of long-range electron transfer reactions are also discussed.