X-ray fluorescence spectroscopy study of the charge state of hetero atoms in organic compounds of row III elements. 9. Compounds containing P=S and P-S fragments

The dependences of the shift of the K line of sulfur on the effective charge on the S atom, calculated by the CNDO/S method, are decomposed into two linear dependences: one for a compound of thione sulfur, the other for the rest of sulfur-containing systems. The dependences of the shift of the K line of P on the effective charge on the P atom, calculated by the CNDO/S method, are also decomposed into two linear dependences; one for compounds of three-coordinate P, the other for compounds of P with coordination number >3. In thiophosphoryl compounds, the electron density on the S atom varies symbatically with that for the P atom. In systems containing the P-S bond, the magnitudes of the effective charge on the S atom remain virtually constant.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1345–1348. June, 1990.     

A further study of the substrate specificity in the reduction of 20-oxosteroids with a culture ofActinomyces roseochromogenus

Chemistry of Natural Compounds - A culture ofActinomyces roseochromogenus ATCC 3347 reduces 17-hydroxy- and 16α, 17α-epoxy-20-oxopregnenes to the corresponding 20α-alcohols, but is...     

Covering Results and Perturbed Roper–Suffridge Operators

This work is devoted to the advanced study of Roper–Suffridge type extension operators. For a given non-normalized spirallike function (with respect to an interior or boundary point) on the open unit disk of the complex plane, we construct perturbed extension operators in a certain class of Banach spaces and prove that these operators preserve the spirallikeness property. In addition, we present an extension operator for semigroup generators. We use a new geometric approach based on the connection between spirallike mappings and one-parameter continuous semigroups. It turns out that the new one-dimensional covering results established below are crucial for our investigation.     

A validated positive chemical ionization GC/MS method for the identification and quantification of amphetamine, opiates, cocaine, and metabolites in human postmortem brain

A sensitive and specific method for the simultaneous detection and quantification of amphetamine, opiates, and cocaine and metabolites in human postmortem brain was developed and validated. Analytes of interest included amphetamine, morphine, codeine, 6-acetylmorphine, cocaine, benzoylecgonine, ecgonine methyl ester, ecgonine ethyl ester, cocaethylene, and anhydroecgonine methyl ester. The method employed ultrasonic homogenization of brain tissue in pH 4.0 sodium acetate buffer and solid phase extraction. Extracts were derivatized with N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide and N,O-bis(trimethylsilyl) trifluoroacetamide. Separation and quantification were accomplished on a bench-top positive chemical ionization capillary gas chromatograph/mass spectrometer with selected ion monitoring. Eight deuterated analogs were used as internal standards. Limits of quantification were 50 ng/g of brain. Calibration curves were linear to 1000 ng/g for anhydroecgonine methyl ester and 6-acetylmorphine, and to 2000 ng/g for all other analytes. Accuracy across the linear range of the assay ranged from 90.2 to 112.2%, and precision, as percent relative standard deviation, was less than 16.6%. Quantification of drug concentrations in brain is a useful research tool in neurobiology and in forensic and postmortem toxicology, identifying the type, relative magnitude, and recency of abused drug exposure. This method will be employed to quantify drug concentrations in human postmortem brain in support of basic and clinical research on the physiologic, biochemical, and behavioral effects of drugs in humans.     

Separation of isomers of new psychoactive substances and isotope-labeled amphetamines using UHPSFC-MS/MS and UHPLC-MS/MS

The use of sub-2?µm particles columns is finding its use in ultrahigh-pressure supercritical fluid chromatography (UHPSFC), opening up for fast analysis and high-resolution separations. The development of new and more robust systems also makes the technique more interesting for bioanalytical analysis, where the need for reproducible and fast analysis with little downtime is great. One area where the use of UHPSFC could become a useful tool is in the separation of structural isomers of new psychoactive substances (NPS). 2-, 3-, and 4- structural isomers of fluoroamphetamine, fluoromethamphetamine, and methylmethcathinone, isomeric pairs of the synthetic cannabinoids UR-144/UR-144 degradant, XLR-11/XLR-11 degradant, JWH-015/JWH-073, and JWH-019/JWH-122, as well as amphetamine and several stable isotope-labeled amphetamine internal standards were separated with UHPSFC-MS/MS and compared with ultrahigh-pressure liquid chromatography (UHPLC) MS/MS. NPS isomers that were difficult to separate with reversed-phase UHPLC-MS/MS were separated by UHPSFC; in most cases with an orthogonal retention order to UHPLC. In contrast to the behavior seen when using reversed-phase UHPLC, the deuterated amphetamines eluted later than amphetamine with UHPSFC. ¹³C₆-labeled amphetamine coeluted with amphetamine for all conditions, making this the best choice of an internal standard.