Geometry optimization in ab initio SCF calculations: Part IV. Energy barriers and dipole moments obtained with floating orbital geometry optimization (FOGO)

The floating orbital geometry optimization (FOGO) described previously is applied to H₂O₂, NH₃, HNC, HNO, HNCO, and CH₃OH. In the FOGO method we apply two analytically calculated energy gradients in a variable metric method. Some orbitals are no longer fixed on the corresponding nuclei, but their position is optimized simultaneously with the nuclear coordinates. It is shown that relative energies (e.g. rotational barriers) are obtained with similar accuracy to basis sets including polarization functions. Further, it is confirmed that FOGO yields excellent dipole moments. The FOGO method involves a considerable time saving compared to conventional calculations with DZ + P basis sets.     

A Structural Basis of Light Energy and Electron Transfer in Biology (Nobel Lecture)

Aspects of intramolecular light energy and electron transfer are discussed for three protein cofactor complexes whose three-dimensional structures have been elucidated by X-ray crystallography: the light harvesting phycobilisomes of cyanobacteria, the reaction center of purple bacteria, and the blue multi-copper oxidases. A wealth of functional data is available for these systems which allows specific correlations to be made between structure and function and general conclusions to be drawn about light energy and electron transfer in biological materials.     

CdO auf Cadmiumanoden in Alkalihydroxidlösungen??

Anodic films formed potentiostatically in 1M NaOH on Cadmium electrodes were examined by means of electron diffraction under carefully controlled conditions. Glancing incidence electron diffraction indicates the presence of Cd(OH)₂ on the electrolyte side of the film and of CdO on the metal side. Transmission electron diffraction of thin isolated films indicates only Cd(OH)₂ in films formed below the Flade-potential of the CdO electrode, but CdO along with Cd(OH)₂ above the Flade-potential. In these films selected area diffraction reveals spots consisting exclusively of a very thin oxid layer.     

Atomic absorption inhibition titration of orthophosphate and polyphosphates

The atomic absorption inhibition titration of phosphates was studied for two types of burner. Dependence on gas Flow-rates was observed. The method with a pre-mix burner was employed to determine phosphate in surface and waste waters. The results are compared with those by the standard method. The proposed method was found to be rapid, simple and accurate.     

Determination of polar organic compounds by potentiometry at an anodically pretreated nickel oxide electrode

The open-circuit potential drop of an oxidatively pretreated nickel electrode in 0.1 M NaOH was used to develop a technique for the determination of alcohols, amino acids, carbohydrates, etc., in aqueous solution. The electrode pretreatment consisted of the formation of nickel hydrated oxides on the electrode surface with an oxidation state > 2. Both electrochemical and chemical pre-oxidation of the electrode surface were examined. The analytical signal was the enhancement of the potential drop corresponding to analyte concentration. The analytical signal was linearly related to the logarithm of the analyte concentration. The limits of determination ranged from 1 mM for low-molecular-weight to 0.02 mM for alkyl polyether alcohols. The flow-injection technique allows convenient pretreatment and direct observation of the analytical signal. Interferences from chloride and calcium can be readily eliminated by excluding them during electrode pretreatment. Potentiometric measurements were correlated with amperometric anodic responses at the nickel oxide electrode, allowing an unusual direct comparison of the two methods.     

Factors determining the performance of triple quadrupole, quadrupole ion trap and sector field mass spectrometers in electrospray ionization tandem mass spectrometry of oligonucleotides. 1. Comparison of performance characteristics

The performance of triple-stage quadrupole (TSQ), quadrupole ion trap (QIT), and double focusing sector field (DFSF) mass spectrometers for the generation of fragment ions to obtain sequence information about oligonucleotides was compared. Upon electrospray ionization (ESI), the charge-state distribution of candidate precursor ions not only varied significantly with the type of mass spectrometer, but also with the size and sequence of the investigated oligonucleotides. While concentration limits of detection for an octanucleotide were in the 100 pmol/L range on the QIT and in the 5-10 nmol/L range on the TSQ and DFSF instruments, those of a 24-mer were in the 2-13 nmol/L range on all three instruments. Reproducibility of mass determination, an important prerequisite for reliable identification of fragment ions, was highest on the TSQ with 0.0037% relative standard deviation over three days. Finally, the tandem mass spectra of a dimethoxytritylated pentanucleotide recorded on the three instruments were compared. Relatively simple spectra dominated by complete series of fragment ions of the (a-B) and w type were obtained on the QIT. Complete series of (a-B) and w ions were also observed on the TSQ. However, additional fragments belonging to the b, c, d, x and z series were found in the spectrum. In the spectrum recorded after in-source fragmentation in the DFSF, only fragments corresponding to the loss of a nucleobase and a complete series of w ions were observed. All three mass spectrometers were suitable for the generation of fragment ions, from which the complete nucleotide sequence of the pentanucleotide could be deduced.     

Prediction of partition coefficients in ternary liquid-liquid systems as a function of the phase system composition by factor analysis for

The measured partition data of 26 steroids for six different compositions of ternary liquid-liquid systems consisting of 2,2,4-trimethylpentane, ethanol and water are used in calculations of partition data for new phase system compositions. It was possible to reproduce the original data and to verify new experimental data by this calculation with high accuracy. Calculations were done in three ways. In the first, non-linear regression of the partition coefficients as a function of the phase system composition was examined. With this classical approach it is possible to calculate the values of the partition coefficients, solute by solute, with good accuracy. In the second approach, principal component factor analysis was used. The phase system-specific factors for further phase system compositions were calculated with a non-linear regression of these factors on the phase system composition. In combination with the solute-specific factors, the values of the partition coefficients for all solutes in any phase system composition could be predicted with excellent accuracy. In the third approach, target transformation factor analysis was applied. A relationship between the partition coefficient and the phase system composition was established on the basis of either the phase system composition itself or a simple function of it. This method also gave very accurate predictions of known and unknown partition coefficients.     

Use of γ-γ Coincidence Spectrometry in the Geochemical Study of Diamictites from South Africa

We used - coincidence spectrometry to investigate the possible presence of a meteoritical component in 27 samples of South African diamictites. Recently, several studies have suggested that some tillites/diamictites may represent impact breccias, but a petrographical study by our group found no evidence for the presence of impact-characteristic shocked minerals. The siderophile elements, such as Cr, Co, Ni, and, especially, the platinum group elements, have high abundances in meteorites, but low abundances in terrestrial crustal rocks. The Ir content of the diamictites was measured with the new iridium coincidence spectrometer (ICS) at the University of Vienna, with detection limits of around 0.02 ppb. No enrichments in the contents of Ir and other siderophile elements compared to average crustal concentrations were found; thus, no unequivocal evidence for an impact origin of these diamictites of the South African Dwyka Group can be documented.     

Loss of epithelial polarity is accompanied by differential association of proteins with intracellular membranes

Cellular membranes play an important role in the formation and maintenance of epithelial polarity, which is lost early during carcinogenesis. We set out to identify membrane proteins which are altered during loss of cell polarity in mammary epithelium. As a model system we used murine mammary epithelial cells expressing the conditional oncoprotein c-JunER, which induces a reversible loss of polarity upon beta-estradiol-driven activation [1]. When grown either in the absence or presence of hormone, these cells exhibit a polarized or unpolarized phenotype, respectively. Different membrane fractions of polarized or unpolarized cells were analyzed by two-dimensional electrophoresis (2-DE) and differentially expressed membrane proteins were identified. To distinguish between transmembrane orientation and peripheral attachment of these proteins, were performed extractions with carbonate at high pH or with Triton X-114. In addition, cytosolic proteins of both states were analyzed to investigate their differential association with distinct membrane fractions. We found ten protein spots preferentially or exclusively in polarized cells and 17 other proteins as being upregulated during loss of polarity. Some of the peripheral membrane proteins were identified by microsequencing. The resident Golgi protein nucleobindin and fructose-bisphosphate aldolase were preferentially associated with membranes of polarized cells, whereas alphaB crystallin was detected exclusively and in high amounts in unpolarized cells.     

Characterization of some physical and chromatographic properties of monolithic poly(styrene-co-divinylbenzene) columns

Monolithic capillary columns were prepared by copolymerization of styrene and divinylbenzene inside a 200 microm i.d. fused silica capillary using a mixture of tetrahydrofuran and decanol as porogen. Important chromatographic features of the synthesized columns were characterized and critically compared to the properties of columns packed with micropellicular, octadecylated poly(styrene-co-divinylbenzene) (PS-DVB-C18) particles. The permeability of a 60 mm long monolithic column was slightly higher than that of an equally dimensioned column packed with PS-DVB-C18 beads and was invariant up to at least 250 bar column inlet pressure, indicating the high-pressure stability of the monolithic columns. Interestingly, monolithic columns showed a 3.6 times better separation efficiency for oligonucleotides than granular columns. To study differences of the molecular diffusion processes between granular and monolithic columns, Van Deemter plots were measured. Due to the favorable pore structure of monolithic columns all kind of diffusional band broadening was reduced two to five times. Using inverse size-exclusion chromatography a total porosity of 70% was determined, which consisted of internodule porosity (20%) and internal porosity (50%). The observed fast mass transfer and the resulting high separation efficiency suggested that the surface of the monolithic stationary phase is rather rough and does not feature real pores accessible to macromolecular analytes such as polypeptides or oligonucleotides. The maximum analytical loading capacity of monolithic columns for oligonucleotides was found to be in the region of 500 fmol, which compared well to the loading capacity of the granular columns. Batch-to-batch reproducibility proved to be better with granular stationary phases compared to monolithic stationary phase, in which each column bed is the result of a unique column preparation process.