Three hydrophobic amino acids in <Emphasis Type=Italic>Escherichia coli</Emphasis> HscB make the greatest contribution to the stability of the HscB-IscU complex

Background  

General iron-sulfur cluster biosynthesis proceeds through assembly of a transient cluster on IscU followed by its transfer to a recipient apo-protein. The efficiency of the second step is increased by the presence of HscA and HscB, but the reason behind this is poorly understood. To shed light on the function of HscB, we began a study on the nature of its interaction with IscU. Our work suggested that the binding site of IscU is in the C-terminal domain of HscB, and two different triple alanine substitutions ([L92A, M93A, F153A] and [E97A, E100A, E104A]) involving predicted binding site residues had detrimental effects on this interaction. However, the individual contribution of each substitution to the observed effect remains to be determined as well as the possible involvement of other residues in the proposed binding site.     

Mineral?le

Ohne Zusammenfassung     

Performance Tested Method multiple laboratory validation study of ELISA-based assays for the detection of peanuts in food

Performance Tested Method multiple laboratory validations for the detection of peanut protein in 4 different food matrixes were conducted under the auspices of the AOAC Research Institute. In this blind study, 3 commercially available ELISA test kits were validated: Neogen Veratox for Peanut, R-Biopharm RIDASCREEN FAST Peanut, and Tepnel BioKits for Peanut Assay. The food matrixes used were breakfast cereal, cookies, ice cream, and milk chocolate spiked at 0 and 5 ppm peanut. Analyses of the samples were conducted by laboratories representing industry and international and U.S governmental agencies. All 3 commercial test kits successfully identified spiked and peanut-free samples. The validation study required 60 analyses on test samples at the target level 5 microg peanut/g food and 60 analyses at a peanut-free level, which was designed to ensure that the lower 95% confidence limit for the sensitivity and specificity would not be <90%. The probability that a test sample contains an allergen given a prevalence rate of 5% and a positive test result using a single test kit analysis with 95% sensitivity and 95% specificity, which was demonstrated for these test kits, would be 50%. When 2 test kits are run simultaneously on all samples, the probability becomes 95%. It is therefore recommended that all field samples be analyzed with at least 2 of the validated kits.     

An analytical strategy for quaternary ammonium neuromuscular blocking agents in a forensic setting using LC-MS/MS on a tandem quadrupole/time-of-flight instrument

An analytical strategy is described for analyzing quaternary ammonium neuromuscular blocking agents in a wide variety of biological specimens in a forensic setting. Neuromuscular blocking agents such as succinylcholine, pancuronium, and tubocurarine, often used as paralytic agents during surgery, are occasionally suspected as paralytic poisoning agents involved in suspected homicide and suicide cases. Because suspicion in such cases can develop slowly, the age, nature, and quality of available specimens varies greatly. The compounds are challenging analytically because of their simultaneous precharged yet lipophilic character. An analytical strategy has been devised for extracting these compounds from complex matrices using a combination of a modified Bligh and Dyer liquid-liquid extraction (used in reverse) followed by reverse-phase ion pairing solid-phase extraction using heptafluorobutyric acid as an ion pairing reagent. Final analysis is by LC-MS/MS using a tandem quadrupole orthogonal acceleration time of flight instrument (Q-TOF) with repetitive product ion scanning at high resolution. Native and spiked specimens are compared for both quantitative and especially qualitative purposes. The method has been applied to a wide variety of fluid and tissue specimen types, including numerous specimens from exhumation autopsies. For most specimens, detection limits are in the 2 to 10 ng/g range. Succinylmonocholine has been demonstrated to be present at low levels in normal posthumous kidney and liver. The Q-TOF is an excellent platform for forensic analytical investigations. This analytical strategy should also be applicable to other problematic analytes and sample matrices.     

以香豆素为基用以识别氟离子的新型比色化学传感器

以香豆素作为发色团,胺基为氢键供体,以—C=N键桥连设计合成了可裸眼识别氟离子的化学传感器1,吸收光谱结果表明在乙腈中它可以高选择性识别氟离子,光谱红移70 nm,溶液颜色由橙色变为蓝紫色,而其它离子如Cl~-、Br~-、I~-、H_2PO_4~-、NO_3~-、HSO_4~-、AcO~-等均不影响其对氟离子的识别.通过核磁共振氢谱考察其识别机制,表明传感分子通过与F~-间的质子转移反应,使整个体系电子离域,分子内电荷转移更加显著,从而导致吸收光谱大幅红移.     

ortho-Directed electrophilic boronation of a benzyl ketone: the preparation, X-ray crystal structure, and some reactions of 4-ethyl-1-hydroxy-3-(4-hydroxyphenyl)-2-oxa-1-boranaphthalene

4-Ethyl-1-hydroxy-3-(4-hydroxyphenyl)-2-oxa-1-boranaphthalene (4) is formed in 78% yield from the reaction of 1-(4-methoxyphenyl)-2-phenylbutan-1-one with an of excess boron tribromide in dichloromethane followed by treatment with water. Reaction of 4 with iodine in aqueous sodium hydroxide gives a second oxaboracycle, 3-ethyl-1-hydroxy-3-(4-hydroxybenzoyl)-2,1-benzoxaborolane (5). The X-ray crystal structure determinations of both boron heterocycles are reported. Other new compounds reported are 1-(4-hydroxyphenyl)-2-(1-hydroxyphenyl)-butan-1-one (6), formed by reaction of 4 with alkaline hydrogen peroxide, and 1-(4-hydroxyphenyl)-2-(2-biphenyl)-butan-1-one (8), formed by coupling of 4 with bromobenzene in the presence of Pd(PPh₃) ₄.