Uptake of magnetic nanoparticles into cells for cell tracking

A challenge for future applications in nanotechnology is the functional integration of nano-sized materials into cellular structures. Here we investigated superparamagnetic Fe₃O₄ iron oxide nanoparticles coated with a lipid bilayer for uptake into cells and for targeting subcellular compartments. It was found that magnetic nanoparticles (MNPs) are effectively taken up into cells and make cells acquire magnetic activity. Biotin-conjugated MNPs were further functionalized by binding of the fluorescent tag streptavidin–fluorescein isothiocyanate (FITC) and, following uptake into cells, shown to confer magnetic activity and fluorescence labeling. Such FITC-MNPs were localized in the lysosomal compartment of cells which suggests a receptor-mediated uptake mechanism.     

On the mechanism of the copper-mediated C-S bond formation in the intramolecular disproportionation of imine disulfides

The mechanism of the copper-mediated disproportionation of aromatic imine disulfides to benzothiazoles in the gas phase is investigated by experimental and theoretical methods. Application of infrared multiphoton dissociation and hydrogen/deuterium exchange experiments combined with density functional theory (DFT) calculations of the relevant molecular structures and the associated infrared spectra allows the identification of the observed ionic intermediates. The theoretical investigation of the possible reaction pathways supported by collision-induced dissociation experiments provides a consistent mechanistic picture of the reaction catalyzed by a single copper(I) ion. Activation of the substrate proceeds via homolytic sulfur-sulfur bond cleavage, yielding metal complexes in the formal +3 oxidation state; carbon-sulfur coupling and hydrogen-atom transfer complete the transformation to the products. Exploratory studies demonstrate that in the gas phase, the disproportionation of the imine disulfide can also be mediated by other metal ions via different either homo- or heterolytic mechanisms without involving high-valent intermediates.     

A coupled theory of electromagnetism and gravitation

A coupling electromagnetism with a previously developed scalar theory of gravitation is presented. The principle features of this coupling are: (1) a slight alteration to the Maxwell equations, (2) the motion of a charged particle satisfies an equation with the Lorentz force-appearing on the right side in place of zero, and (3) the energy density of the electromagnetic field appears in the gravitational field equation in a manner similar to the mass term in the Klein-Gordonequation. The field of a static, spherically symmetric charged particle is computed. The electromagnetic field gives rise to l/r ² terms in the gravitational potential.     

Austauschreaktionen an komplexgebundenen liganden von elementen der IV. Hauptgruppe : III. Darstellung von halogen-, pseudohalogen- und hydridokomplexen des typs π-C5H5Fe(CO)2SiX3

The complexes CpFe(CO)₂SiBr₃, CpFe(CO)₂SiI₃, CpFe(CO)₂SiBr₂(OMe), and CpFe(CO)₂SiI(NH-cyclo-C₆H₁₁)₂ are prepared by the reaction of CpFe(CO)₂SiR₃ (R = OMe, NH-cyclo-C₆H₁₁) with HBr, HI and CH₃I. Treating CpFe(CO)₂SiCl₃ with a large excess of NaN₃, KOCN or KSCN yields the first tri-pseudohalogensilyl—transition-metal-complexes. The compounds are characterized by IR and mass spectra. A new method of preparation of the already known complex CpFe(CO)₂SiH₃ is described starting from CpFe(CO)₂SiCl₃ and LiAlH₄.     

Comparison of the photoelectrochemical oxidation of methanol on rutile TiO2 (001) and (100) single crystal faces studied by intensity modulated photocurrent spectroscopy

The photooxidation of methanol as a model substance for pollutants on rutile TiO(2) (001) and (100) surfaces was investigated using intensity modulated photocurrent spectroscopy (IMPS). The results are analyzed in view of the influence of the surface structure, the methanol concentration and the electrode potential on the rate constants of charge transfer and recombination. The obtained results have been explained with a model combining the theory of IMPS for a bulk semiconductor surface and the nature of the surface-bound intermediates (alternatively mobile or immobile OH˙ radicals). The results indicate that water photooxidation proceeds via mobile OH˙ radicals on both surfaces, while methanol addition gives rise to the involvement of immobile OH˙ radicals on the (100) surface. Detailed analysis in view of the surface structures suggests that the latter observation is due to efficient electron transfer from bridging OH˙ radicals on the (100) surface to methanol, while coupling of two of these radicals occurs in the absence of methanol, making them appear as mobile OH˙ radicals. In the case of the (001) surface, the coupling reaction dominates even in the presence of methanol due to the smaller distance between the bridging OH˙ radicals, leading to more efficient water oxidation, but less efficient methanol photooxidation on this surface.     

Trinuclear rhodium hydride complexes

Three novel trinuclear rhodium hydride complexes of the type {[Rh(PP*)H](3)(μ(2)-H)(3)(μ(3)-H)}[BF(4)](2) containing diphosphines Tangphos, t-Bu-BisP* and Me-DuPHOS have been synthesised. The new compounds are very stable. Their structures have been characterized by X-ray analysis in the solid state and by NMR-spectroscopic investigations in solution.     

über die Reaktionen von CH3OCl,CF3OCl,CF3OF und CF3OH mit dem supersauren System HF/MF5 (M = As,Sb) Darstellung und Charakterisierung von CH3OCl(H)+MF6− und CF3OCl(H)+MF6−

On the Reactions of CH₃OCl, CF₃OCl, CF₃OF, and CF₃OH with the Superacid System HF/MF₅ (M = As, Sb). Preparation and Characterization of CH₃OCl(H)⁺MF₆^? and CF₃OCl(H)⁺MF₆^? The preparation of the chlorine oxoniumsalts CH₃OCl(H)⁺MF₆^? and CF₃OCl(H)⁺MF₆^? by protonation of CH₃OCl and CF₃OCl in the superacid solution of HF/MF₅ (M = As, Sb) is described. However CF₃OF and CF₃OH have not been protonated under the same conditions. In the case of CF₃OH the formation of F₂CO · MF₅ is observed. The novel compounds are characterized by nmr- and vibrational spectroscopy.     

The chemistry of the azanonaborane cluster RNH2---B8H11NHR

The preparation and properties of the R¹R²NH---B₈H₁₁NHR cluster are described. The cluster is stable to aqueous solutions and can be made water-soluble by the introduction of a few hydrophilic groups. This makes the cluster a good candidate as the boron moiety in compounds for boron neutron capture therapy. The chemistry of the cluster preparation, the stability of the cluster, and conditions for reactions of the organic moieties are reviewed. Pyridine derivatives of the cluster show electronic interaction between the cluster and the pyridine.     

From an Icosahedron to a Plane: Flattening Dodecaiodo‐dodecaborate by Successive Stripping of Iodine

It has been shown by electrospray ionization–ion‐trap mass spectrometry that B₁₂I₁₂^2? converts to an intact B₁₂ cluster as a result of successive stripping of single iodine radicals or ions. Herein, the structure and stability of all intermediate B₁₂I_n^? species (n=11 to 1) determined by means of first‐principles calculations are reported. The initial predominant loss of an iodine radical occurs most probably via the triplet state of B₁₂I₁₂^2?, and the reaction path for loss of an iodide ion from the singlet state crosses that from the triplet state. Experimentally, the boron clusters resulting from B₁₂I₁₂^2? through loss of either iodide or iodine occur at the same excitation energy in the ion trap. It is shown that the icosahedral B₁₂ unit commonly observed in dodecaborate compounds is destabilized while losing iodine. The boron framework opens to nonicosahedral structures with five to seven iodine atoms left. The temperature of the ions has a considerable influence on the relative stability near the opening of the clusters. The most stable structures with five to seven iodine atoms are neither planar nor icosahedral.