Nitro derivatives of phenyl-1,2,3-triazole

A number of tri- and tetranitro-N-phenyl-1,2,3-triazolyl compounds were synthesized by a combination of condensation, cycloaddition, and nitration reactions, and their crystal densities, impact sensitivities, and thermal stabilities were determined.     

Spectroscopic diffusion coefficient of methane at 3.39 micron wavelength by a laser study

A novel differential re-analysis of Hubbert's (1976) laser study data of the 3.39 m absorption (Dicke-narrowed) of methane shows that the spectroscopic diffusion coefficient is 10% different from the calculated self-diffusion coefficient. More accurate studies above 10 torr pressure are needed.     

Amperometric measuring cell for the determination of putrescine oxidase activity

A microfabricated, flat form, amperometric microcell (microchip) is used in a simple, two-electrode arrangement for putrescine oxidase enzyme activity determinations. The cell contains a platinum microdisk working electrode and an Ag/AgCl reference electrode covered by a porous, hydrophilic membrane. An electrochemically-prepared size-exclusion layer is applied on the working electrode surface, to avoid the effect of electroactive interferences in the sample. The hydrophilic membrane, resting on the bottom of the cell, is soaked with a small volume of buffered substrate solution and a few mul enzyme containing sample solution is dispensed over the electrodes. During the enzyme activity measurement a catalytic reaction takes place in the membrane-supported liquid film over the working electrode surface. The hydrogen peroxide produced in the reaction is detected amperometrically. The amperometric current-time curves are used for evaluation. In our work putrescine was used as a substrate to determine the unknown putrescine oxidase enzyme activity of the sample. Elevated diamine oxidase enzyme activity in the vaginal milieu can indicate premature rupture of the amniotic membrane. Results with membrane discs, containing all the necessary chemicals in solid or lyophilized form, are very encouraging with respect of a single use, 'reagentless' biosensor for home care.     

The first report of unusual flipping of the cycloadducts from 1,3-dipolar cycloaddition of 3,4,5,6-tetrahydropyridine N-oxide to N-cinnamoyl piperidines

A series of cycloadducts possessing unusual flipping modes have been isolated from the 1,3-dipolar cycloaddition of 3,4,5,6-tetrahydropyridine N-oxide to piperidides of cinnamic acid and para-substituted cinnamic acids and these were analyzed by X-ray crystallography to reveal novel solid-state structures. The presence of two different flippomers arising due to flipping of the six/five bicyclic ring was confirmed both in solid state and in solution. This is the first observation of 1,3-dipolar cycloadducts having two different flippomers arising due to flipping of the isoxazolidine ring.     

Development of a diamine biosensor

An amperometric diamine sensor is developed for clinical applications in diagnosis of bacterial vaginosis (BV). The sensor is based on crosslinked putrescine oxidase (PUO) which catalyzes the conversion of diamines (mainly putrescine and cadaverine) to products including hydrogen peroxide. The hydrogen peroxide is detected anodically at platinum electrode polarized at 0.5 V versus Ag/AgCl. Platinum-plated gold electrodes used as a substrate for the sensor construction, are batch-fabricated on a flexible polyimide foil (Kapton(R), DuPont). A three-electrode cell configuration is used in all amperometric measurements. The sensor construction is based on three layers: an inner layer to reject the interference effect of oxidizable molecules, an outer diffusion controlling layer, and in addition, an enzyme middle layer. The enzyme layer was immobilized by crosslinking PUO with bovine serum albumin (BSA) using glutaraldehyde (GA). An optimization study of the enzyme solution composition was carried out. With the optimized enzyme layer, the biosensor showed a very high sensitivity and fast response time of ca. 20 s. The sensor has a linear dynamic range from (0.5-300 muM) for putrescine that covers the expected biological levels of the analyte. Details on sensor fabrication and characterization are given in the present work.     

Amperometric microcells for alkaline phosphatase assay

To develop simple electrochemical immunoassays, a screen printed amperometric microcell with graphite working and Ag/AgCl reference electrodes was tested for the determination of alkaline phosphatase enzyme (ALP) and anti-humanIgG conjugated ALP (alpha-hIgG-ALP) activity in 5-10 microl samples. To ensure reproducible, steady state conditions, the working electrode surface was coated with mass-transport controlling hydrogel layer. The kinetic response curves of the hydrogel coated electrodes were linear. In addition, the hydrogel layer reduced the nonspecific adsorption of the alpha-hIgG-ALP conjugate on the working electrode surface. The measurements were made in the range of 2 divided by 4000 mU ml(-1) enzyme activities using ascorbic acid 2-phosphate (AAP) as the enzyme substrate. AAP is commercially available, non-toxic and has excellent stability. The sensitivity of the determinations was about 71% of the sensitivity which could be achieved using p-aminophenylphosphate (PAPP), a not easily accessible and unstable enzyme substrate. The experimentally determined kinetic parameters of the ALP enzyme catalyzed reactions were the same with the bare and hydrogel layer coated electrodes.     

Raman and resonance-Raman spectra of CsI/I−3

Raman and resonance-Raman spectra of the I^?₃ ion isolated within CsI crystals have been studied using 647 nm and 488 nm exciting radiation. Sample temperatures between 300 and 20 K have been used. Eleven overtones of the symmetric stretching mode (nν₁) have been observed in the resonance-Raman spectrum excited by the 488 nm Ar⁺ laser line. Bands centred at 153, 170, 264 and 304 cm^?1 have been assigned as ν₃, 2ν₂, ν₁+ν₃ and 2ν₃(Σ⁺) respectively. The remaining structure between the nν₁ lines has been assigned as due to combinations of these lines with the lattice vibrations of the CsI crystal.