Survival of B c mesons in a hot plasma within a potential model

We extend a previous work on the study of heavy charmonia and bottomonia in a deconfined quark-gluon plasma by considering the B _c family of mesons. With the introduction of this bound state of a charm and a beauty quark, we investigate at finite temperature the behavior of the quarkonium, in an energy region between the ψ and the Y states.     

Molecular structure and spectroscopic characterization of tetrakis (2,5-diamino-1,3,4-thiadiazolium) decabromodibismuthate(III)

The title compound [C₂H₅N₄S]₄[Bi₂Br₁₀]; [HL]₄[Bi₂Br₁₀] (L=2,5-diamino-1,3,4-thiadiazole) was prepared and characterized by means of X-ray, and IR measurements. The structure was solved by the heavy-atom method, and least-squares refinement of structural parameters led to a conventionalR factor of 0.036 (R _w =0.032) for 2425 independent reflections. The crystal consists of a condensed [Bi₂Br₁₀]^4– anion and four HL⁺ cations. The anion has three bromine atoms involved in hydrogen bonds with N-bonded H atoms; the nonprotonated nitrogen atom of the cation is involved in hydrogen bonds too. The metal atoms have distorted octahedral geometry.     

Extraction studies of metal complexes with some macrocyclic tetraaza ligands and xanthene dyes : Spectrophotometric determination of Cadmium(II) with Tetramethyltetraazacyclotetradecane and Erythrosin A

The liquid-liquid extraction of ion-pair complexes of zinc(II), copper(II) and cadmium(II) is described. The macrocyclic ligands 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (4Me-cyclam-14) and rac-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (Tet b) are used with xanthene dyes as the counter ions. The apparent extraction constants (D′_c) are reported. The sequences of extraction efficiency of both ligands are related to the structure of the complexes. The apparent molar absorptivity of the Cd(4Me-cyclam-14)—erythrosin A ion-associate is 1.1 × 10⁵ l mol^? cm^?1. The calibration graph is linear over the range 0—10^?5 M, which allows even 0.05 μg ml^?1 cadmium to be determined in a 0.5 M sodium hydroxide medium. No interference was observed from Ni²⁺, Pb²⁺, Zn²⁺, Mg²⁺, Sn⁴⁺, Ga³⁺, Al³⁺ and Fe³⁺. Interferences were Cu²⁺, Hg²⁺, Ag⁺ and large anions.     

Spectroscopic characterization of site-specific [Fe(4)S(4)] cluster chemistry in ferredoxin:thioredoxin reductase: implications for the catalytic mechanism

Light regulation of enzyme activities in oxygenic photosynthesis is mediated by ferredoxin:thioredoxin reductase (FTR), a novel class of disulfide reductase with an active site comprising a [Fe(4)S(4)](2+) cluster and an adjacent disulfide, that catalyzes reduction of the thioredoxin disulfide in two sequential one-electron steps using a [Fe(2)S(2)](2+/+) ferredoxin as the electron donor. In this work, we report on spectroscopic (EPR, VTMCD, resonance Raman, and M?ssbauer) and redox characterization of the active site of FTR in various forms of the enzyme, including wild-type FTR, point-mutation variants at each of the active-site cysteine residues, and stable analogues of the one-electron-reduced FTR-Trx heterodisulfide intermediate. The results reveal novel site-specific Fe(4)S(4)-cluster chemistry in oxidized, one-electron-reduced, and two-electron-reduced forms of FTR. In the resting enzyme, a weak interaction between the Fe(4)S(4) cluster and the active-site disulfide promotes charge buildup at a unique Fe site and primes the active site to accept an electron from ferredoxin to break the disulfide bond. In one-electron-reduced analogues, cleavage of the active-site disulfide is accompanied by coordination of one of the cysteine residues that form the active-site disulfide to yield a [Fe(4)S(4)](3+) cluster with two cysteinate ligands at a unique Fe site. The most intriguing result is that two-electron-reduced FTR in which the disulfide is reduced to a dithiol contains an unprecedented electron-rich [Fe(4)S(4)](2+) cluster comprising both valence-delocalized and valence-localized Fe(2+)Fe(3+) pairs. These results provide molecular level insights into the catalytic mechanism of FTR, and two viable mechanisms are proposed.     

Absolute Configuration and Crystal Structure of a Phosphonate Analogue of Tyrosine Produced by Actinomycetes

Abstract

Levorotatory 1-amino-2-(4-hydroxyphenyl)ethylphosphonic acid (TyrP) of unknown configuration is a part of hypotensive tri-peptides produced by Actinomycetes¹ and is the only 1-aminoalkane phosphonate found so far in living organisms. Nitration of enantiomers of PheP followed by reduction of the p-nitro group and diazotization yielded enantiomers of TyrP of specific rotations +67 and ?67° (c.0.9;1n HCl). Single crystal X-ray analysis showed S configuration for dextrorotatory TyrP. Thus, natural levorotatory TyrP has the R configuration and belongs to the L series of aminoacids.     

Asymmetric synthesis of (R)-[2,2-2H2]-1-aminocyclopropane-1-phosphonic acid (ACPP derivative) conformationally constrained ACC analogue using a chiral sulfinyl auxiliary

The asymmetric cyclopropanation of vinylphosphonate using (S)-dimethylsulfonium-(p-tolylsulfinyl)methylide was applied to obtain a dideuterated cyclopropyl sulfoxide. A three-step synthesis of enantiopure (+)-(1R)-1-amino-2,2-dideuteriocyclopropanephosphonic acid (+)-17-d₂ was developed.     

Quality of Soybean Products in Terms of Essential Amino Acids Composition

The content of protein, moisture content and essential amino acids in conventional and genetically modified soybean grain and selected soybean products (soybean pâté, soybean drink, soybean dessert, tofu) was analyzed in this paper. The following comparative analysis of these products has not yet been carried out. No differences were observed in the amino acid profiles of soybeans and soybean products. The presence of essential amino acids was confirmed except for tryptophan. Its absence, however, may be due not to its absence in the raw material, but to its decomposition as a result of the acid hydrolysis of the sample occurring during its preparation for amino acid determination. Regardless of the type of soybean grain, the content of protein, moisture content and essential amino acids was similar (statistically insignificant difference). Thus, the type of raw material did not determine these parameters. There was a significant imbalance in the quantitative composition of essential amino acids in individual soybean products. Only statistically significant variation was found in genetically modified and conventional soybean pâté. Moreover, in each soy product their amount was lower irrespective of the raw material from which they were manufactured. Therefore, the authors indicate the necessity of enriching soybean products with complete protein to increase their nutritional value.     

A rapid and precise method for the determination of oxygen in certain gases: Modified brady method

The modified brady method is a rapid one, requiring only about one hour for the analysis, but requires large samples of gas, 5 to 20 liters. The precision of the method described here-in is ± 0.004 to ± 0.4 in the low range of oxygen-concentration (0.01 to 0. 10 part per million oxygen),± 0.01 to ± 0.07 in the medium range of oxygen-concentration (0.1 to l .0 part per million oxygen)and ± 0.0 to ± 0.2 in the upper range of oxygen-concentration (1 to 15 parts per million oxygen). The liest precision (winkler method) previously reported was ± 0.3 part per million oxygen. The range of the method is 0.01 to 15 parts per million oxygen. The minimum amount of oxygen detectible is 0.005 part per million.