Sulfur ylides. 10. Modified method for the synthesis of pyrrolizine- and indolizinediones

A modified method for the synthesis of derivatives of pyrrolizinedione and indolizinedione was proposed. The method is based on the intramolecular cyclization of keto-stabilized sulfur ylides generated in situ from diazo ketones and Me₂S in the presence of Rh₂(OAc)₄.     

Density functional calculations for modeling the active site of nickel-iron hydrogenases. 2. Predictions for the unready and ready States and the corresponding activation processes

ZORA relativistic DFT calculations are presented which aim to model the geometric and electronic structure of the active site of NiFe hydrogenases in its EPR-active oxidized states Ni-A (unready state) and Ni-B (ready state). Starting coordinates are taken from the X-ray structure of a mutant of Desulfovibrio fructosovorans hydrogenase refined at 1.81 A resolution. Nine possible candidates for Ni-A and Ni-B are analyzed in terms of their geometric and electronic structure. Comparison of calculated geometric and magnetic resonance parameters with available experimental data indicates that both oxidized states have a micro-hydroxo bridge between the two metal centers. The different electronic structures of both forms can be explained by a modification of a terminal cysteine in Ni-B, best modeled by protonation of the sulfur atom. A possible mechanism for the activation of both oxidized forms is presented.     

Streptonigrin and related compounds IV. Precursors for the a-ring

The synthesis of streptonigrin or its tricyclic (ABC) analogues by the Friedlander condensation requires a 2-nitrobenzaldehyde with all the necessary functionalities. A number of alternative syntheses are examined. It is shown that oxidation of 8-amino-5,6-dimethoxy-2,2-pyridylquinoline leads to 8-amino-2,2-pyridylqunoline-5,6-dione instead of 6-methoxy-2,2-pyridylquinoline-5,8-dione. The synthesis of two useful precursors: 4-bromo-3-hydroxy-5,6-dimethoxy-2-nitrobenzaldehyde and 4-bromo-3-hydroxy-5-methoxy-2-nitrobenzaldehyde is described.     

Scaled Quantum Mechanical Force Fields for the Peroxynitrates. II. Fluorocarbonyl Peroxynitrate and Chlorocarbonyl Peroxynitrate.

The vibrational properties of fluorocarbonyl peroxynitrate, FC(O)OONO₂ and chlorocarbonyl peroxynitrate, ClC(O)OONO₂ were studied by means of density functional theory (DFT) methods. The obtained results served to revise the reported experimental spectra and their corresponding assignments. Subsequently, the revised data were used in the definition of scaled quantum mechanics (SQM) force fields for these peroxynitrates. A set of internal force constants was also calculated from such force fields.     

Methodology for the U.S. Food and Drug Administration's radionuclides in foods program

The U.S. Food and Drug Administration (FDA) is responsible for the wholesomeness of the nation's food supply. The FDA modified its food monitoring program in January, 1973, to include radioactive isotopes. The methodology used to perform, analyses on these food products are taken from the standerd setting societies such as the AOAC International, American Society for Testing Materials and American Public Health Association Standard Methods. In addition, methods not tested by these societies are taken from the literature or from Department of Energy manuals such as the Health and Safety Laboratory and also from Environmental Protection Agency, Public Health Service, and Food and Agricultural Organization manuals. These include the methods for long-lived radionuclides such as tritium, strontium-90, cesium-137 and plutonium. Also, the short-lived radionuclides such as iodine-131, radiocesium, radiocerium and radioruthenium. In addition, they include the natural occurring radionuclides such as radium and uranium isotopes. The activity concentrations of gamma-emitters such as radiocesium, iodine-131 and radioruthenium are determined by gamma-ray spectrometry. This is done using intrinsic germanium detectors with the appropriate hardware and software. The alpha and “pure” beta-emitters are determined by various radiochemical methods and techniques. The radiochemical methodology and equipment used in analyzing these radionuclides are described and discussed. Also, the methodology and equipment for the gamma-emitters are described in more detail in this paper. In addition, the limits of detection for the methods used will be discussed.     

Nuclear methods for food analysis at the U. S. Food and Drug Administration

An overview of radioanalytical techniques used in support of research,monitoring programs, and field assignments directed by the U. S. Food andDrug Administration's Center for Food Safety and Applied Nutrition (CFSAN)is presented. The Winchester Engineering and Analytical Center annually determinesradionuclide concentrations in 260 Total Diet Study foods, approximately 80imported foods, and a selection of domestic foods collected near U. S. nuclearpower plants. Radioanalytical techniques used at CFSAN's neutron activationanalysis laboratory at the National Institute of Standards and Technologyare discussed along with applications for research, quality control, and specialprojects.     

Simple method for the isolation and purification of hemoglobin components.

A simple method for the isolation and purification of hemoglobin components from starch gel by electrophoresis is described. An inverted bottle with a cut off bottom is used. Pieces of gel containing the hemoglobin are embedded in potato starch, wetted with buffer, and placed in the neck of the inverted bottle, the mouth of which has been closed with filter paper and tape. Connection with the negative tank buffer is achieved by inserting a layer of starch gel between the potato starch and the negative tank buffer. By electrophoresis, the hemoglobin migrates and accumulates in a dialysing tube tied around the mouth of the bottle and hanging into the positive tank buffer.