N-1 Substituted ethyl 4-pyrazolecarboxylates: Synthesis and spectroscopic investigations

The synthesis of various N-1 substituted ethyl 4-pyrazolecarboxylates via reaction of ethyl 2-formyl-3-oxo-propionate (= ethoxycarbonylmalondialdehyde) with appropriately substituted hydrazines is described. Moreover, detailed nmr-spectroscopic investigations with the title compounds are presented.     

Coulometric determination of NAD+ and NADH in normal and cancer cells using LDH, RVC and a polymer mediator

An electrochemical method for the measurement of NAD(+) and NADH in normal and cancer tissues using flow injection analysis (FIA) is reported. Reticulated vitreous carbon (RVC) electrodes with entrapped l-lactate dehydrogenase (LDH) and a new redox polymer containing covalently bound toluidine blue O (TBO) were employed for this purpose. Both NAD(+) and NADH were estimated coulometrically based on their reaction with LDH. The latter was immobilized on controlled pore glass (CPG) by cross-linking with glutaraldehyde and packed within the RVC. The concentrations of NAD(+) and NADH in the tissues, estimated using different electron mediators such as ferricyanide (FCN), meldola blue (MB) and TBO have also been compared. The effects of flow rate, pH, applied potential (versus Ag/AgCl reference) and adsorption of the mediators have also been investigated. Based on the measurements of NAD(+) and NADH in normal and cancer tissues it has been concluded that the NADH concentration is lower, while the NAD(+) concentration is higher in cancer tissues. Amongst the electron mediators TBO was found to be a more stable mediator for such measurements.     

Gas phase photoisomerization of urocanic acid – a theoretical study

The photochemistry of urocanic acid is investigated theoretically by means of time-dependent density functional theory. The topology of the potential energy surface along the isomerization pathway and close to the Franck–Condon region is investigated and consequences for the photoisomerization reactions are outlined. A recently published supersonic jet spectroscopy study is reinterpreted in the light of these and earlier theoretical results to give a clear picture of the gas phase photochemistry. It is found that the photochemistry of the two isomers is fundamentally different, in contrast to the situation in solution.     

Evaluation of partition measurements in liquid-liquid segmented flow

The different configurations possible for an FIA extraction system for partition measurements have been tested and the corresponding evaluation formulae based on determinations at different phase flow ratios, verified. Increased flexibility results from the possibility of using samples dissolved in either aqueous or organic phase. Choosing the best configuration in every case makes it possible to extend the range of measurable conditional partition constants without excessive losses in precision.     

Double photoionisation spectra of small molecules and a new empirical rule for double ionisation energies

Complete double photoelectron spectra are presented for 18 small molecules where the location of charges in the cations and dications is relatively clearly defined. The data demonstrate the importance of a coulombic repulsion contribution to the double ionisation energies. Examination of data for a wide range of molecules leads to a new empirical rule to calculate double ionisation energies from the molecules’ single ionisation energies and maximum dimensions. Where single and double ionisation energies are known the rule allows the deduction of plausible intercharge distances.     

The Isolation,Structure, and Synthesis of Davana Ether,an Odoriferous Compound of the Oil of Artemisia pallens Wall.

Several stereoisomers of 2,6,10-trimethyl-2:5, 7:10-diepoxy-dodeca-3,5,11-triene ( 3 ) have been isolated from the oil of Artemisia pallens. The synthesis of the isomeric mixture is described.     

Evaluation of a dialysis probe for continuous sampling in fermentors and in complex media

A dialysis probe is described for continuous sampling from complex solutions, such as fermentation broth, milk or waste water, to yield samples suitable for liquid chromatography, flow injection analysis, enzyme calorimetry, etc. The analyte is transferred to a flow stream separated from the sample by a dialysis membrane that is protected from fouling by a strong tangential flow of the sample solution. This flow is accomplished by placing a magnetic stirring bar close to the membrane surface. The device is constructed of materials permitting the probe to be steam-sterilized when mounted inside a fermentor.     

ROTATIONAL DIFFUSION OF RHODAMINE 6G IN HUMAN BLOOD SERUM

Abstract —The time-dependent rotational relaxation of Rhodamine 6G in fresh and dried human blood serum was investigated using picosecond phasefluorometry. Measurements were also carried out in aqueous solutions of amino acids, glucose, urea, and bovine serum albumin to evaluate our model for the interactions. It is shown that the distribution of Rhodamine 6G between the aqueous and the protein phase of the blood serum strongly depends on protein concentration and temperature.