X-ray spectra and core hole energy curves of some diatomic molecules

Soft X-ray emission spectra of the molecules CO, N₂, NO and O₂ are examined for the purpose of deriving information on their core hole energy curves. Molecular force constant and equilibrium bond lengths are determined for the core hole species C*O and N₂*, and a qualitative analysis is made for CO*, N*O, NO* and O₂*. The results show that differences of equilibrium geometries between the core hole states and the ground states are very well reproduced (better than 1 pm) by SCF calculations within the Hartree-Fock formalism. Inclusion of anharmonicity in the Franck-Condon analysis gives a small but significant effect on the best fitted value for the core hole state bond lengths (about 0.5 pm). Oxygen is binding energies determined from the X-ray spectra are shown to agree with ESCA data, in most cases within a few tenths of an eV. Calculated ΔSCF transition energies reproduce the experimental data within a few eV.     

Heat output as a bio-marker of the dimethyl sulfoxide-induced decrease in rat hepatoma cell metabolism in vitro

Dimethyl sulfoxide (DMSO) is widely and routinely used as a vehicle in various investigations, especially within the pharmaceutical industry. It has been used for the evaluation of the effects of hydrophobic xenobiotics on cells, as well as for the cryopreservation of biological material. Isothermal microcalorimetry is a powerful tool for monitoring heat production, which is a function of general cellular metabolic activity. Employing this microcalorimetric technique, a low concentration of DMSO routinely used for the addition of hydrophobic substances to, e.g., cell cultures, was shown to decrease heat production (per unit DNA) by the rat hepatoma cell lines FAO, Morris 7800C1 and H4IIE by 32–38%. However, such low concentrations of DMSO did not influence the cell cycle or the degree of apoptosis in these cell populations. Caution is thus advisable when utilizing DMSO as a vehicle in cell culture experiments.     

Inspection and duplication

In a cyclic industrial process a certain component fails during a cycle with probabilityp. In order to increase the reliability of the process, the component is duplicated in parallel with one or two redundant components of the same kind. The components fail independently of each other. To further increase the reliability, the system can be inspected aftern cycles, given that it has not failed during the previousn?1 cycles. Upon inspection failed components are repaired. In order to choose the inspection intervaln, the conditional probability that the system fails during cycle non, given that it has not failed during the previousn?1 cycles, is calculated.     

Determination of fat content and fatty acid composition in meat and meat products after supercritical fluid extraction

Two different relatively simple, commercially available supercritical fluid extractors (SFE), Leco and Foss-Tecator, were tested for the determination of total fat content in meat and meat products. The fatty acid composition in meat and meat products was also determined after the Foss-Tecator extraction in an aliquot of the extract. Total fat was determined by weighing after the different extraction procedures and the fatty acid composition by gas chromatography after hydrolysis and methylation of the extract. The results for total fat content agreed well with results from a standard method of Schmid, Bondzynski, and Ratzlaff, which uses conventional solvent extraction. Fatty acid composition was compared with the Bligh and Dyer extraction, and showed good agreement. The average relative difference between SFE and Bligh and Dyer of all fatty acids in the sample was <3% for acids exceeding 0.5% of total fatty acid amount. The advantages of SFE over traditional methods are a much lower consumption of hazardous organic solvents and shorter extraction times. To obtain quantitative recoveries by SFE, ethanol was added to the extraction cells before extraction.     

Aggregation numbers of SDS micelles formed on EHEC. A steady state fluorescence quenching study

The present investigation proves that in the interaction between an uncharged polymer and a negatively charged amphiphilic ion (surfactant) clusters are actually formed and it provides data for the cluster concentration and the cluster size and their variation with composition. The polymer bound cluster size increases after a certain critical surfactant concentration and passes through a maximum. This maximum cluster size decreases with decreasing polymer concentration and attains a limiting value at infinite dilution. For the highest polymer concentration the cluster size is close to the size of normal surfactant micelles. The cluster concentration was determined by a fluorescence quenching technique and the amount surfactant adsorbed to the polymer by dialysis equilibrium measurements. Combining these independent sets of data permits the cluster aggregation number to be unambiguously determined. Solubilization experiments indicate the possibility to regulate the amount solubilized by varying the polymer concentration. The molecular properties of the system are sensitively monitored by the variation in two vibronic peaks in the pyrene fluorescence emission spectrum which defines a hydrophobic index. Very good agreement is found between all three experimental methods. Finally, the model suggested is analyzed in terms of coil size and cluster-cluster distance. Depending upon the degree of adsorption saturation and the density of polymer segments in solution the interaction may switch from being intramolecular to becoming intermolecular.     

Oligosaccharide sequences in Quillaja saponins by electrospray ionization ion trap multiple-stage mass spectrometry

Ten different samples with 13 previously identified saponin structures from Quillaja saponaria Molina were investigated by electrospray ionization ion trap multiple-stage mass spectrometry (ESI-ITMS(n)) in positive and negative ion modes. Both positive and negative ion mode MS(1)-MS(4) spectra were analyzed, showing that structural information on the two oligosaccharide parts in the saponin can be obtained from positive ion mode spectra whereas negative ion mode spectra mainly gave information on one of the oligosaccharide parts. Analysis of MS(1)-MS(4) spectra identified useful key fragment ions important for the structural elucidation of Quillaja saponins. A flowchart involving a stepwise procedure based on key fragments from MS(1)-MS(3) spectra was constructed for the identification of structural elements in the saponin. Peak intensity ratios in MS(3) spectra were found to be correlated with structural features of the investigated saponins and are therefore of value for the identification of terminal monosaccharide residues.     

Studies on dodecyl betainate in combination with its degradation products or with phosphatidyl choline-phase behavior and hemolytic activity

Surface active betaine esters contain a hydrolysable bond and give naturally occurring products (fatty alcohol and the amino acid betaine) on degradation. They are therefore interesting candidates for use as cationic surfactants in pharmaceutical applications. In this work the phase behavior of two systems of relevance for the utilization of dodecyl betainate as a pharmaceutical excipient is studied, namely dodecyl betainate/dodecanol/betaine hydrochloride/D2O and dodecyl betainate/phosphatidyl choline (PC)/ethanol/D2O. The techniques used for phase characterisation were 2H NMR measured on the solvent, small angle X-ray spectroscopy and optical microscopy. Dilute dodecyl betainate/PC dispersions were characterized using laser diffraction. It is shown that introduction of relatively small amounts of the hydrolysis products of dodecyl betainate, i.e., dodecanol and betaine (used in the form of betaine hydrochloride), has a strong effect on the phase behavior of the binary dodecyl betainate/D2O system. The degradation products change the average curvature of the surfactant film so that, instead of a hexagonal phase at concentrations above the micellar phase, a probably defective, lamellar phase seems to form. The dodecyl betainate/PC/ethanol/D2O system shows a large region of a highly swelling lamellar phase. Dispersions of dodecyl betainate/PC/ethanol in water can be prepared with low energy input; i.e., the preconcentrate can be regarded as a self-dispersing solution. Introduction of dodecyl betainate and its degradation products does not impair the ability of PC to form vesicles. Experiments for evaluating the toxicity of surface active betaine esters to erythrocytes were also performed. There are indications that the hemolytic activity of dodecyl betainate is lower than that of the stable surfactant tetradecyltrimethylammonium chloride, which has similar critical micelle concentration. A combination of dodecyl betainate and PC gives very low hemolytic activity.