Beta galactosidase enzyme fragment complementation as a novel technology for high throughput screening

In this review, the applications of beta galactosidase complementation are described. alpha Complementation is a naturally occurring process in bacteria and in engineered cells, and can also occur in eukaryotic cells. Two forms of alpha complementation have been used in high throughput screening (HTS), in which interacting fragments complement with either low or high affinity. Low affinity complementation is used to monitor protein protein interactions, such as those occurring in homodimerization of the epidermal growth factor receptor (EGFR), and provides a robust screen for detection of EGFR inhibitors. High affinity complementation provides the basis for several HTS assays, in which analytes, such as cAMP or IP(3), are detected in crude cell lysates. A development of the latter approach is protein labeling, providing for measurement of cell protein expression and trafficking. Collectively, the use of beta galactosidase complementation provides a novel and flexible technology for highly sensitive, homogeneous HTS assay development.     

Quantitative softness parameters and their application in elucidation of Structure of Bimetallic Tetrathiocyanate Complexes

〉₂M(NCS)₂M′(SCN)₂〈 and [ML₆][M′(SCN)₄], (M = Co(II) and Ni(II), M′ = Zn(II), Cd(II) and Hg(II) and L = aniline(ani), p-toluidine(tol), pyridine(py), nicotinamide(nia), 2,2′-bipyridine(bipy) and 4-aminopyridine (apy)) have been prepared and characterized. Their structure have been proposed on the basis of molar conductance, magnetic moment, group theoretical calculations, ligand field parameters, infrared and electronic spectral studies. The proposed structures have also been supported by quantitative values of softness ?\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm E}_{\rm n}^{_ + ^ +},{\rm E}_{\rm m}^{_{\rm +}^{\rm +}} $\end{document}”?,. Total softness of M and M′ and their difference \documentclass{article}\pagestyle{empty}\begin{document}$ \Delta {\rm TE}_{\rm n}^{_ + ^ +} \left({{\rm M} - {\rm M}'} \right) $\end{document} have also been derived by the following equations and related to the structure of the complexes. .     

Fluctuating boundary layers in combined convection flows along a vertical surface

The effect of buoyancy force on laminar boundary layer in two dimensional flow and heat transfer along a semi-infinite vertical surface, when the velocity of the on-coming stream oscillates in magnitude about a steady mean, is analysed. Two separate solutions valid for low and high frequency ranges are developed. It is found that for low frequency oscillations the phase angles of oscillatory components of skin friction and the rate of heat transfer increase as the Grashof number increases. For very high frequencies, the velocity field is of shear-wave type unaffected by the mean flow; the phase lead in the skin friction is, then, /4 and the rate of heat transfer fluctuation indicates a phase lag of /2 over that of the free stream oscillations.The authors are thankful to referee for many useful suggestions.     

A class of exact solutions for doubly anharmonic oscillators

The solution of a difference equation in the form of an infinite continued fraction is used to obtain a class of exact solutions for the eigenfunctions and eigenvalues of doubly anharmonic oscillators described by potentials of the type (1/2)²x²+(1/4)x⁴+(1/6)x⁶, n>0, provided certain constraints on the couplings are satisfied. The class is denumerably infinite but not complete.     

Amperometric ascorbimetric determination of cerium(IV) and Iron(III) with two polarized electrodes

Summary Amperometric ascorbimetric determinations of cerium(IV) and ferric iron have been carried out at 50°C with two polarized electrodes at 200 and 100 mV respectively. The results obtained are fairly accurate and precise within ±1.0 per cent. A simple method for successive determination of cerium and iron has been developed; and conditions for such estimations have been established. At an acidity of 2.5 M with respect to sulphuric acid, it is possible to ward off the reduction of ferric iron and thereby cerium(IV) is successfully titrated with ascorbic acid in this medium. After completion of the reaction and then lowering the acid concentration to p_H 1.5 with aid of ammonium hydroxide, Fe^III is titrated with standard ascorbic acid yielding good results.     

A spectrophotometric method for uranium determination

A very sensitive extraction spectrophotometric method for the analysis of uranium based on the extraction of a uranium—benzoate—crystal violet complex by a mixture of xylene and benzene is described. The absorbance maximum is at 606 nm and molar absorptivity is 4.28·10⁴ l·mol⁻¹·cm⁻¹. The interference due to a number of anions and cations studied without any pre-extraction was found to be within permissible limits. The method has been used for determining uranium in a synthetic solution, i.e., uranium in the presence of various other ions. The interference due to some cations was eliminated by the use of a masking agent (boric acid).     

Rotational relaxation of neutral red in alkanes: effect of solvent size on probe rotation

Rotational reorientation times of a polar molecule neutral red (NR) have been measured in n-alkanes using steady-state fluorescence depolarization technique. The rotational dynamics of NR in alkanes is described by the Stokes-Einstein-Debye hydrodynamic theory with slip boundary condition. However, we have observed that as the size of the solvent molecule becomes bigger than the size of the solute molecule, the probe molecule experiences reduced friction and the experimentally measured reorientation times are shorter than those predicted by the hydrodynamic theory. These size effects have been analyzed using quasihydrodynamic theories.     

Electrophilic fluorinating reagent mediated synthesis of fluorinated alpha-keto Ethers,benzil, and 6,6'-dialkoxy-2,2'-bipyridines

Interactions of various fluorinated and nonfluorinated alcohols with trans-stilbene in the presence of electrophilic reagents were studied. Under neat conditions, reactions of trans-stilbene (1) with fluorinated alcohols, R(f)OH (R(f) = CF3CH2-, CFH2CH2-, CF3CF2CH2-, CF2H(CF2)3CH2-, (CF3)2CH-, (CF3)3C- (2a-f) in the presence of an electrophilic reagent, 1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor) or N,N-difluoro-2,2'-bipyridinium bis(tetrafluoroborate) (MEC-31), gave alpha-keto ethers (3a-f) and benzil (4) in good to moderate yields. alpha-Keto ether and benzil formation was very much dependent on the reaction time, the degree of fluorination of the alcohols, and whether a solvent such as CH3CN, DMF or DMA was utilized. In solution, alpha-keto ethers and benzil did not form. Interestingly, under neat conditions, nonfluorinated alcohols, ROH (R = CH3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2CH2-, CH3CH2CH2CH2CH2CH2-) (5g-k) did not react with trans-stilbene in the presence of MEC-31 but gave 6,6'-dialkoxy-2,2'-bipyridines (6g-k), regioselectively, in excellent isolated yields. On the other hand, fluorinated alcohols did not react with MEC-31. Reaction of MEC-31 with an excess of diethylene glycol (7) gave the bipyridine derivative (8) in 88% isolated yield. Reaction of 8 either with diethylaminosulfur trifluoride (DAST) or bis(2-methoxyethyl)aminosulfur trifluoride (Deoxofluor) readily produced the corresponding difluoro derivative (9) in 85% isolated yield. All new compounds have been characterized by spectroscopic and elemental analysis.     

Electrophoresis simulations using Chebyshev pseudo-spectral method on a moving mesh

We present the implementation and demonstration of the Chebyshev pseudo-spectral method coupled with an adaptive mesh method for performing fast and highly accurate electrophoresis simulations. The Chebyshev pseudo-spectral method offers higher numerical accuracy than all other finite difference methods and is applicable for simulating all electrophoresis techniques in channels with open or closed boundaries. To improve the computational efficiency, we use a novel moving mesh scheme that clusters the grid points in the regions with poor numerical resolution. We demonstrate the application of the Chebyshev pseudo-spectral method on a moving mesh for simulating nonlinear electrophoretic processes through examples of isotachophoresis (ITP), isoelectric focusing (IEF), and electromigration-dispersion in capillary zone electrophoresis (CZE) at current densities as high as 1000 A/m. We also show the efficacy of our moving mesh method over existing methods that cluster the grid points in the regions with large concentration gradients. We have integrated the adaptive Chebyshev pseudo-spectral method in the open-source SPYCE simulator and verified its implementation with other electrophoresis simulators.     

γ-radiolysis of acetylated cotton cellulose: An ESR study

The nature and behavior of free radicals induced in acetylated cotton celluloses irradiated with γ-rays have been studied by electron spin resonance (ESR) spectroscopy. Dehydrogenation and deacetylation appear to be responsible for the free radicals observed from samples irradiated at 77°K. The degree of substitution enhanced the yield of acetyl radicals when the samples were irradiated at 77°K and adversely affected the overall radical concentration when irradiation was done at 300°K. In addition, the ESR spectra of samples irradiated under vacuum at 300°K were more intense than those obtained from samples irradiated in air. The nature, yield, and post-irradiation behavior of the primary radicals are discussed in the light of the ultimate chemical effects observed.