Ueber die Darstellung von Traubenzucker

Ohne Zusammenfassung     

On the application of slip boundary condition on curved boundaries

Hydrodynamic simulations of sloshing phenomena often involve the application of slip boundary condition at the wetted surfaces. If these surfaces are curved, the ambiguous nature of the normal vector in the discretized problem can interfere with the application of such a boundary condition. Even the use of consistent normal vectors, preferred from the point of view of conservation, does not assure good approximation of the continuum slip condition in the discrete problem, and non‐physical recirculating flow fields may be observed. As a remedy, we consider the Navier slip condition, and more successfully, the so‐called BC‐free boundary condition. Copyright © 2004 John Wiley & Sons, Ltd.     

Fourier transform IR product study of the reaction of CFO radicals with O2 at 298 K

Experimental results are presented of a Fourier transform IR product study at 298 K of the reaction system CFO+O₂ at oxygen pressures between 3 and 250 mbar. Pulsed photolysis of oxalyl fluoride (CFO)₂ or formyl fluoride (CHFO) at 193 nm was used to produce CFO. As stable products we detected bis-fluoroformyl peroxide, carbonyl fluoride and carbon dioxide. The yields of the peroxide and of CF₂O were measured as a function of [O₂]/[precursor] and are discussed qualitatively.     

Synthesis and hybridization properties of oligonucleotides containing polyamines at the C-2 position of purines: a pre-synthetic approach for the incorporation of spermine into oligodeoxynucleotides containing 2-(4,9,13-triazatridecyl)-2'-deoxyguanosine

We have developed a synthesis of spermine-containing oligonucleotides (ODN-sper) which allows incorporation of multiple polyamine residues. This approach was based on the pertrifluoroacetylated 5'DMT-dGsper phosphoramidite synthon. Its coupling yield with resin-bound ODN decreased dramatically when close to the 3'-end. Optimization of the coupling conditions allowed 22-mer ODNs containing up to six spermine residues to be synthesized. Several ODNs of different sequences with 1-4 pendent spermines could be purified and their hybridization properties were evaluated. Duplex melting temperatures increased linearly with the number of polyamine residues (deltaTm/sper = 3.0 +/- 0.2 degrees C in 100mM NaCl). This compares very favorably with values reported for duplexes of similar initial stability containing other cation-substituted bases. Moreover, the stability increase was neither sequence nor position-dependent, and even contiguous spermine residues did not cross-talk. Extrapolation based on these findings leads to the conclusion that a duplex formed with a 22-mer oligonucleotide containing seven spermine residues would be as stable as genomic DNA, which highlights its potential for DNA strand invasion.     

Dimerizable cationic detergents with a low cmc condense plasmid DNA into nanometric particles and transfect cells in culture

The size of condensed DNA particles is a key determinant for in vivo diffusion and gene delivery to cells. Gene molecules can be individually compacted by cationic thiol detergents into nanometric particles that are stabilized by oxidative conversion of the detergent into a gemini lipid. To reach the other goal, gene delivery, a series of cationic thiol detergents with various chain lengths (C(12)-C(16)) and headgroups (ornithine or spermine) was prepared, using a versatile polymer-supported synthetic strategy. Critical micelle concentrations and thiol oxidation rates of the detergents were measured. The formation and stability of complexes formed with plasmid DNA, as well as the size, xi-potential, morphology, and transfection efficiency of the particles were investigated. Using the tetradecane/ornithine detergent, a solution of 5.5 Kpb plasmid DNA molecules was converted into a homogeneous population of 35 nm particles. The same detergent, once oxidized, exhibited a typical lipid phase internal structure and was capable of effective cell transfection. The particle size did not increase with time. Surprisingly, the gel electrophoretic mobility of the DNA complexes was found to be higher than that of plasmid DNA itself. Favorable in vivo diffusion and intracellular trafficking properties may thus be expected for these complexes.     

Carbon Dioxide as an Alternative C1 Synthetic Unit: Activation by Transition-Metal Complexes

The carbon dioxide molecule has been of limited importance as a synthetic unit in organic chemistry. When it is coordinated to transition metals, however, completely new possibilities arise; CO₂ can bond to metal complexes in a variety of ways and can enter into insertion and coupling reactions, or become catalytically attached to other substrates. The formation of C? C bonds between carbon dioxide and unsaturated hydrocarbons under conditions of homogeneous catalysis makes available new synthetic routes to industrially interesting organic compounds.