Deuteron photodisintegration with the Bonn OBE potentials

The various OBE approximations to the recent Bonn potential are studied in deuteron photodisintegration below -threshold. Consistent static meson-exchange currents, isobar currents, and the relativistic spin-orbit current are included. Concerning the OBEPT also the leading retardation corrections in the currents are taken into account. Comparison with experimental data is carried out in detail.Supported by Deutsche Forschungsgemeinschaft (SFB 201)     

Synthesis and 12-helical secondary structure of beta-peptides containing (2R,3R)-aminoproline

[structure: see text] (2R,3R)-Aminoproline, a pyrrolidine-based beta-amino acid, was synthesized and incorporated into hexa-beta-peptide 4. This residue confers water solubility when the ring nitrogen is protonated and allows for 12-helix formation in aqueous solution. Circular dichroism spectra display the 12-helical signature, and 12-helical structure was confirmed by 2D NMR analysis.     

Vibrational spectroscopic characterization of fluoroquinolones

Quinolones are important gyrase inhibitors. Even though they are used as active agents in many antibiotics, the detailed mechanism of action on a molecular level is so far not known. It is of greatest interest to shed light on this drug-target interaction to provide useful information in the fight against growing resistances and obtain new insights for the development of new powerful drugs. To reach this goal, on a first step it is essential to understand the structural characteristics of the drugs and the effects that are caused by the environment in detail. In this work we report on Raman spectroscopical investigations of a variety of gyrase inhibitors (nalidixic acid, oxolinic acid, cinoxacin, flumequine, norfloxacin, ciprofloxacin, lomefloxacin, ofloxacin, enoxacin, sarafloxacin and moxifloxacin) by means of micro-Raman spectroscopy excited with various excitation wavelengths, both in the off-resonance region (532, 633, 830 and 1064 nm) and in the resonance region (resonance Raman spectroscopy at 244, 257 and 275 nm). Furthermore DFT calculations were performed to assign the vibrational modes, as well as for an identification of intramolecular hydrogen bonding motifs. The effect of small changes in the drug environment was studied by adding successively small amounts of water until physiological low concentrations of the drugs in aqueous solution were obtained. At these low concentrations resonance Raman spectroscopy proved to be a useful and sensitive technique. Supplementary information was obtained from IR and UV/vis spectroscopy.     

Preparative continuous separation of biological particles by means of free-flow magnetophoresis in a free-flow electrophoresis chamber.

For sorting, cells or cellular components can specifically be labeled by antibody-coated magnetic beads. We have developed a device for continuous magnetic sorting based on the flow-chamber of a free-flow electrophoresis system. Magnetically labeled particles are injected into a given continuously flowing chamber buffer and pass an inhomogeneous magnetic field, configurated perpendicular to the flow direction. According to its magnetic moment, the magnetic material is deviated into the direction of the magnetic forces, while nonmagnetic material passes the field without interaction. The magnetic forces can be changed with the electrical current of the solenoids producing the magnetic field. As in the free-flow electrophoresis system, the particle fractions are collected in different vials. On-line control of the experiments can be performed by an optical scanning system. Experiments with model particles achieved a sorting purity of more than 99% at a rate of up to 5 X 10(8) particles per hour. In experiments with blood cells, a high enrichment of either B-or-T-lymphocytes was obtained. In contrast to free-flow electrophoresis, there is no limitation, in principle, regarding the type of chamber buffer to be used. This allows an optimal adaptation of the buffer conditions to the requirements of vital sorting. The preliminary results so far confirm this conclusion.     

Model-independent analysis of the differential cross section for the reaction n+d→π0+t at medium energies

Experimental values of the differential cross section for the reactionn+d→π ⁰+t at large angles (θ?50°) in the neutron energy range 460–560 MeV and the known values of the coupling constants \(G_{nn\pi ^O }^2 \) andG _tdn ² are used to predictdσ/dΩ at smaller angles. The method is based on the use of general analytic properties of the differential cross section in the cosgq-plane.     

Determination of 2-mercaptobenzothiazole, tolyltriazole and benzotriazole in coolant formulations by liquid chromatography

An analytical method based on high-performance liquid chromatography is suitable for the determination of corrosion inhibitors in coolant solutions based on ethylene glycol. An isocratic system of methanol/aqueous sodium acetate buffer is used with a Microbondapak C18 column. Recovery is 99+%, with a sensitivity of 0.05% w/w. No sample pretreatment is necessary. Analysis time is 15 min.     

Friction and nanowear of polystyrene against hydrophobic and hydrophilic substrates

The ambition of this study is to analyze the role of interfacial interactions in friction and nanowear of polystyrene, by comparing friction against hydrophobic wafers (methyl‐terminated) and hydrophilic wafers (hydroxyl‐terminated) as a function of sliding velocity and normal force. Friction experiments are performed with a translation tribometer and nanowear investigation is achieved by using atomic force microscopy (AFM) analysis of the wafer surfaces after friction. Experimental results show that the friction coefficients measured on hydrophilic surfaces are always larger than those obtained with hydrophobic surfaces, indicating a relationship between friction and interfacial interactions. Elsewhere, AFM analysis shows that polystyrene transfer appears for a higher normal force in the case of hydrophobic substrates compared to hydrophilic one. However, the corresponding tangential (or friction) force necessary to detect transfer is quite similar for both types of substrates, indicating that the initial wear of polystyrene occurs for a similar threshold interfacial shear. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2449–2454, 2006     

Rapid access to cis 3-substituted prolines

The O-triflate of 2-cyano-3-oxopyrrolidine was obtained and used in a palladium coupling reaction. The resulting Δ²-pyrrolidine derivatives allowed diastereocontrol at C2 and C3 after catalytic hydrogenation and led to chiral 3-substituted prolines as conformationally constrained amino acids.