(e, 3e) test on e-e correlations in helium

The angular variations of the five-fold differential cross section obtained by using different wave functions of helium are compared with experimental data. It is found that in the coplanar geometry two kinematical arrangements, (i) equal energy sharing between the two ejected electrons with one of them ejected along the momentum transfer direction and the other along varying direction and (ii) the Bethe ridge condition with fixed sum of ejected electron energies and varying angle between them, are very sensitive to e-e correlations contained in the target wave function. This comparison has been used to show that open-shell class of wave functions better incorporate e-e correlations than the closed-shell class.     

Fast Marching Method for Calculating Reactive Trajectories for Chemical Reactions

We present a method for computing classical Newtonian trajectories that minimize the path length or transit time from reactant to product. Our approach is based on a generalization of the fast-marching method, which allows us to construct the solution of the Hamilton-Jacobi equation for the action that optimizes the desired quantity. The resulting “reactive paths” can be interpreted as reaction coordinates but, unlike more conventional choices, they contain dynamical information about the chemical system of interest.     

Phase Transfer Catalysis Preparation of Acyl Isothiocyanates

The use of phase transfer catalysis, PTC, for nucleophillic substitution reactions is well documented.^1,2 Included among these reactions is the preparation of both alkyl³ and aryl⁴ thiocyanates. However, PTC reactions at an acyl carbon are much less common. Brándstróm⁵ has reported the preparation of acyl azides and Weber⁶ has used PTC to prepare benzoyl cyanide. Recently Illi⁷ has used PTC to acylate sterically crowded phenols.     

Se-Adenosyl-l-selenomethionine Cofactor Analogue as a Reporter of Protein Methylation

Posttranslational methylation by S-adenosyl-l-methionine(SAM)-dependent methyltransferases plays essential roles in modulating protein function in both normal and disease states. As such, there is a growing need to develop chemical reporters to examine the physiological and pathological roles of protein methyltransferases. Several sterically bulky SAM analogues have previously been used to label substrates of specific protein methyltransferases. However, broad application of these compounds has been limited by their general incompatibility with native enzymes. Here we report a SAM surrogate, ProSeAM (propargylic Se-adenosyl-l-selenomethionine), as a reporter of methyltransferases. ProSeAM can be processed by multiple protein methyltransferases for substrate labeling. In contrast, sulfur-based propargylic SAM undergoes rapid decomposition at physiological pH, likely via an allene intermediate. In conjunction with fluorescent/affinity-based azide probes, copper-catalyzed azide-alkyne cycloaddition chemistry, in-gel fluorescence visualization and proteomic analysis, we further demonstrated ProSeAM's utility to profile substrates of endogenous methyltransferases in diverse cellular contexts. These results thus feature ProSeAM as a convenient probe to study the activities of endogenous protein methyltransferases.     

Theory of sheath in a collisional multi-component plasma

The aim of this brief report is to study the behaviour of sheath structure in a multi-component plasma with dust-neutral collisions. The plasma consists of electrons, ions, micron size negatively charged dust particles and neutrals. The sheath-edge potential and sheath width are calculated for collisionally dominated sheath. Comparison of collisionless and collisionally dominated sheath are made.     

Quantitative determination of itazigrel in rodent diet by reversed-phase HPLC and evaluation of its stability at 20 degrees C

A simple, accurate and precise procedure for the quantitation of itazigrel (a potent lipophilic inhibitor of collagen and arachidonic acid-induced aggregation being studied for its effects on peripheral vascular disease) from granulated rodent diet is presented. The drug was extracted from rodent diet using methanol + water (80:20) following dissolution of the diet in water. Samples of the supernatant were injected into the HPLC and the eluent was monitored with a fluorescent detector (lambda ex = 320 and lambda em = 430) to achieve analytical specificity. Interday coefficients of variation of the calibration curve slope were +/- 6% on standards between 0 and 1000 micrograms/g. Potency and homogeneity of the drug spiked diet prepared over a 1 year interval at 70, 200 and 600 micrograms/g was 99.3 +/- 2.5%, 100 +/- 1.8%, and 101 +/- 1.9% of label, respectively. Samples prepared for chromatography were stable for 24 h at 20 degrees C, and drug in diet was stable for 102 days when protected from light and stored at 20 degrees C.     

Lantibiotics as surface active agents for biomedical applications

The unique physical structure of lantibiotics, (e.g. double bonds, thioethers rings, and unusual amino acid residues), makes these antimicrobial peptides highly reactive, and thus different in mode-of-action from clinical antibiotics. Members of the lantibiotic group have been successfully tested against pathogenic organisms for decades. Some lantibiotics have been studied for use in treating skin infections, and several have been characterized for their anti-viral activity. In addition to their antimicrobial capabilities, lantibiotics possess amphiphilic characteristics, making them potentially valuable as emulsifiers in drug formulations. The small size and surface activity of these peptides also may allow them to enhance the transport of therapeutic compounds across cell membranes. Over 30 lantibiotics are presently known, and more are being discovered each year. With the rising incidence of resistant bacteria, lantibiotics offer considerable potential as safe, antimicrobial barriers for use on synthetic material surfaces, as emulsifiers in formulation of hydrophobic drugs, and as absorption promoters for selected compounds across mucosal membranes. The major hindrance to research in this area is that lantibiotics are difficult to obtain. But with improved methods for production and purification of these unusual antimicrobial agents, the promise of cost-effective application of lantibiotics may eventually be realized.     

Competitive adsorption of bacteriophage T4 lysozyme stability variants at hydrophilic glass surfaces

The competitive adsorption behavior exhibited by the wild-type T4 lysozyme and two of its structural stability variants was studied by 125I radioisotope labeling. The mutant lysozymes were produced by substitution of the isoleucine residue at position 3 in the wild type with a tryptophan residue, resulting in a protein with lower structural stability, or with a cysteine residue, resulting in a protein with higher structural stability. Adsorption kinetics were recorded for binary protein mixtures in contact with a clean glass surface, in which one variant had been radiolabeled and the other had not. All pair permutations were tested. The kinetic data show that in instances in which exchange reactions between adsorbed protein and dissolved protein occur, they occur such that more stable variants are removed from the surface by less stable variants. The less stable proteins thus exhibited an advantage in competitive adsorption over the more stable proteins, in these tests.