Studies on nucleation from solution of some analytically important metal chelates-II Nickel dimethylglyoximate

A new direct-mixing and rapid particle-counting system useful for studies on crystal nucleation solution is described. The methods used to calibrate and evaluate the system are reported together with the results obtained during studies on nucleation from solution of nickel dimethylglyoximate. The Volmer-Weber, Becker-D?ring model of the nucleation process is used to correlate the results.     

Near-infrared tunable diode laser spectrometer for the remote sensing of vehicle emissions

A near-infrared diode laser-based spectrometer has been designed and built for the remote sensing of vehicle emissions. It detects carbon monoxide and carbon dioxide absorptions around 1580 nm and can provide the ratio CO/CO(2) for vehicle exhaust studies. The system is battery powered and is designed to sit unobtrusively at the side of the road. The optics and electronics of the system is described and preliminary results are presented from field trials. Extensions to the spectrometer in terms of sensitivity by detection of the more intense first overtone of carbon monoxide around 2320 nm are described, in addition to further work on other species of interest.     

Synthesis, characterisation and high-performance liquid chromatography of C6-C16 dicarboxylyl-mono-coenzyme A and -mono-carnitine esters.

The synthesis and purification of the mono-coenzyme A and mono-carnitine esters of the homologous series of straight-chain even-numbered dicarboxylic acids (C6-C16) is described. The corresponding 3-hydroxyacyl- and 2-enoyl-CoA esters were prepared enzymatically. A reversed-phase high-performance liquid chromatographic (HPLC) system for the analysis of the intact CoA esters is described and their chromatographic behaviour documented. Reversed-phase HPLC systems for the analysis of the 4-bromophenacyl derivatives of the dicarboxylyl-mono-carnitines and the 4-nitrobenzyl derivatives of the free acids are also described. Some preliminary studies of the metabolism of [U-14C]hexadecanedionoyl-mono-CoA by rat liver peroxisomes and rat skeletal muscle mitochondria are described illustrating the application of these methods.     

Chemistry of the phenoxathiins II. Synthesis of 1-azaphenoxathiin

The synthesis of 1-azaphenoxathiin, the parent ring system of a recently reported class of novel CNS agents is described. The ¹³C-nmr spectrum and its assignment are also reported as a model for structure confirmation studies.     

Conformation as a protecting group: a regioselective aromatic bromination en route to complex pi-electron systems

A new strategy to achieve regioselective functionalization of a sterically congested aromatic system driven by conformational demands is described. Electrophilic substitution occurs at the more planarizable subunit without undesired chemistry at mutually reactive sites and without the need for protecting or masking groups that must be manipulated later. Model studies are described to understand this selectivity, and possibilities for the construction of orthogonal, differentially substituted pi-systems of relevance for molecular electronics are demonstrated.     

Enantioselective,Desymmetrizing, Bromolactonization Reactions of Symmetric Olefinic Dicarboxylic Acids

The results of studies leading to the development of enantioselective desymmetrizing, bromolactonization reactions of symmetric olefinic dicarboxylic acids, which are promoted by a C₃‐symmetric trisimidazoline catalyst, are described. These processes generated carboxylic‐acid‐containing bromolactones in moderately high enantiomeric excesses. The results of optimization studies showed that reactions in a mixed solvent system of toluene and acetone proceeded with the highest levels of enantioselectivity. NMR studies probing the interactions between the catalyst and dicarboxylic acid substrates, as well as the effect of acetone on the stereochemistry of the process, are also described.     

Molecular complexes of sulfur dioxide with organic carbonates

Spectroscopic studies made on the bisphenol A polycarbonate–sulfur dioxide system showed evidence of interaction between polymer and penetrant. Equilibrium studies made on solutions of sulfur dioxide and organic carbonates chosen as monomer analogs showed that complexes of the donor–acceptor type were formed, and that at temperatures of 15°C and less the stoichiometry of these was greater than 1:1. The procedures described are compared with those used in other donor–acceptor studies, and the results observed from the equilibrium studies are interpreted by using data reported for other sulfur dioxide–donor systems.     

Novel preloaded resins for solid-phase biotinylation of carboxylic acids

Use of solid-phase synthesis for the derivatization of carboxylic acids with biotinylated spacers consisting of ethylenoxy units is described. An aminomethylated resin provided with an acid-labile aldehyde linker is used as the polymer support and three different systems with a reactive amino group are introduced. Acylation of each system was tested with a set of model carboxylic acids and afforded crude products of excellent purity. The preloaded resins are similar to the Biotin-PEG-NovaTagTM resin but offer several advantages including simple elongation of the spacer arm. The protocols described represent a very efficient way of modifying compounds to obtain ligands for affinity chromatography studies.     

Biosynthesis of the thiamin pyrimidine: the reconstitution of a remarkable rearrangement reaction

The conversion of 5-aminoimidazole ribonucleotide (AIR) into 4-amino-2-methyl-5-hydroxymethylpyrimidine (HMP) is a fascinating reaction on the thiamin biosynthetic pathway in bacteria and is probably the most complex unresolved rearrangement in primary metabolism. We have successfully reconstituted this reaction in a cell-free system. The E. coli thiC gene product and an additional unidentified E. coli protein are required for the reaction. In addition, SAM and nicotinamide cofactors are required for full activity. Labeling studies to determine the origin of most of the atoms in the pyrimidine are described. Based on these studies, a new mechanism for HMP formation is proposed.     

Potentiometric electrode measurement of serum antibodies based on the complement fixation test

Trimethylphenylaminoniuin-selective electrodes are used in the measurement of serum antibodies to bovine serum albumin, with serum complement and sensitized, marker-loaded sheep red blood cell ghosts as mediators. The result is a sensitive and reproducible assay system for the antibody in the presence of its antigen. In addition, the method described is shown to be valuable for basic studies of immune complex—complement interactions.     

Determination of ammonia in air and aqueous samples with a gas-sensitive semiconductor capacitor

The properties of a new type of ammonia gas-sensitive semiconductor capacitor are described. The sensor is based on a palladium MOS field-effect capacitor with a thin layer (3 nm) of iridium surrounding the palladium gate. The lower limit of detection for ammonia in air is 1 ppm (0.59 mg kg^?1). The analytical characteristics and temperature-dependence of the sensor in measurements of ammonia in air are evaluated. Ammonia in aqueous solutions is determined by the use of a continuous flow system utilizing a gaspermeable membrane in combination with the sensor. The calibration plot of the voltage drop of the capacitor vs. ammonia concentration in 150-μl samples is linear in the concentration range 0.2 × 10^?6–5 × 10^?5 M. Ammonia is determined in rain and river water as well as in whole blood and blood serum; 15 samples per hour can be assayed. Analytical recovery studies and the selectivity properties of the system are described and discussed. Finally, the properties of the flow-through system in continuous monitoring are described.     

Studies of short-lived fission products by means of the multistage solvent extraction system SISAK

The multistage solvent extraction system SISAK is described. The system is used for online studies of nuclides with half-lives down to 1 s. Some of the chemical separation procedures are presented, and a survey is given on the results obtained so far. The possiblity to gain access to nuclides with even shorter half-lives is also discussed.     

Dynamic small-angle scattering system for the study of materials deformation and relaxation

A dynamic small-angle x-ray scattering system (DSAXS) for the study of materials deformation and relaxation has been developed in the National Center for Small-Angle Scattering Research, Oak Ridge National Laboratory (NCSASR-ORNL), in collaboration with Polymer Research Institute of the University of Massachusetts. The principles of DSAXS are outlined, including experimental procedures such as π-sector and Fourier expansion techniques. A few important functions required for studies of crystalline polymers, namely, static and dynamic lamellar orientation, dynamic lamellar separation, dynamic invariant function, etc., are defined. The hardware and software of the DSAXS system are described. Some preliminary results obtained for a spherulitic high-density polyethylene by π-sector technique and for a row-nucleated polybutene-1 by Fourier expansion techniques are demonstrated to evaluate the performance of the system.     

System for measuring separate impedance characteristics with a three- or four-electrode potentiostat

A system for measuring impedance components has been elaborated. Its operating principle consists, as in the case of bridges, of compensating current and comparing the impedance of the studied system with the impedance of a standard set of capacitors and resistors. Measuring system with a three- and four-electrode potentiostat are described. The system with a three-electrode potentiostat can be used in the studies of double layer capacitance and of metal-electrolyte solution electrode kinetics. The system with a four-electrode potentiostat is suitable for measuring the impedance of interfaces separating immiscible electrolyte solutions or of membranes. It is an advantage of the proposed systems that they cannot “see” the impedance of current electrodes.     

Minicomputer control of measurements of spectroelectrochemical processes: Part 2. A New Measurement System for Simultaneous Coulometric and Spectrophotometric Investigations

The design of a system for simultaneous coulometric and spectrophotometric measurements is described. A special fiber optic cell is coupled to a rapid scanning spectrophotometer. The assembly is controlled by a Nova-2 minicomputer which simultaneously acquires and processes the data. The programmed measurement procedures enable spectrophotometric and coulometric curves to be recorded for linear or stepped sweep of the electrode potential, and kinetic relations to be found for a constant electrode potential. Test measurements on chlorpromazine and trifluoroperazine showed that the system is useful for studies of kinetics and mechanisms of electrode processes. The advantages and disadvantages of the method are discussed.     

Novel tandem quadrupole-acceleration-deceleration mass spectrometer for neutralization-reionization studies

A new tandem mass spectrometer of the quadrupole-acceleration lens-deceleration. lens-quadrupole (QADQ) configuration is described. The instrument is designed for neutralization-reionization studies and consists of a 2000-u quadrupole mass analyzer as MS-I, an acceleration electrostatic lens, a series of three differentially pumped collision cells, and an electrostatic deceleration lens, energy filter, and another 2000-u quadrupole mass analyzer as MS-II. The ion optical system achieves high total ion transmission for 5–9-keV ions. Unit mass resolution in neutralization-reionization mass spectra of aromatic compounds is demonstrated. Mass, kinetic energy, and linked scans at various levels of mass resolution and sensitivity are described.     

Electrophilic cyclization of N-alkenylamides using a chloramine-T/I2 system

A new protocol for the cyclization of N-alkenylamides using chloramine-T and iodine is described. When N-alkenylsulfonamides are treated with chloramine-T and iodine, three- to six-membered N-heterocycles are obtained with complete stereoselectivity. The method is compatible with the cyclization of the allylbenzamide or allylbenzthioamide to afford an oxazoline or thiazoline derivative, respectively. Mechanistic studies indicate that the chloramine-T/I₂ system functions as an effective iodonium species.     

UV curable electrodeposition systems

This article reviews the development of a UV curable electrodeposition system. Tailor-made acrylic functionalized polyurethane resins, which have been designed, are described and basic properties of the final e-coat system are shown. In addition several fundamental studies have been performed in order to analyze as well the homogeneity of the deposition as the efficiency of the UV curing process.     

Long range phosphorus-phosphorus coupling constants in bis(phosphorylhydroxymethyl)benzene derivatives

Long range spin-spin couplings found between two phosphorus atoms are quite rare phenomena. A new example of such a coupling through seven bonds is described for 1-[(diethoxyphosphoryl)butyryloxymethyl]-4-[(diethoxyphosphoryl)hydroxymethyl]benzene and 1,4-bis[phosphorylhydroxymethyl]benzene and through six bonds for tetraethyl phenylene-1,3-(bishydroxymethylphosphonate). Coupling constants in this system are also well predicted by theoretical studies.