Synthesis, optical characterization, and electrochemical properties of isomeric tetraphenylbenzodifurans containing electron acceptor groups

Isomeric tetraphenylbenzodifuran systems, benzo[1,2-b:5,4]difuran and benzo[1,2-b:4,5]difuran, containing electron acceptor groups (CF(3), CN, and NO(2)) have been synthesized and studied. Their electronic absorption, fluorescence, two-photon absorption cross sections, and electrochemical properties were investigated. The absorption and emission maxima are red-shifted for the linear-conjugated systems in comparison with the corresponding isomer. Dual fluorescence was observed and the existence of a twisted intramolecular charge transfer state was confirmed by low-temperature emission experiments. Wide HOMO-LUMO energy gaps were obtained ranging from 2.53 to 3.28 eV. HOMO levels were found in the energy range of -6.03 to -6.63 eV while LUMO are within -2.55 to -3.52 eV.     

A new application of solvatochromic pyridinium-N-phenolate betaine dyes: examining the electrophilicity of lanthanide shift reagents

The well-known solvent polarity indicators, pyridinium-N-phenolate betaine dyes, appeared to be promising reactants for comparing the electrophilicity of NMR chemical shift reagents such as lanthanide(III) complexes with dipivaloylmethane [tris(2,2,6,6-tetramethylheptan-3,5-dione)]. These dyes are suitable for the UV-vis spectroscopic study of weak specific Lewis acid/base interactions in solution.     

Construction of N-glycan microarrays by using modular synthesis and on-chip nanoscale enzymatic glycosylation

An effective chemoenzymatic strategy is reported that has allowed the construction, for the first time, of a focused microarray of synthetic N-glycans. Based on modular approaches, a variety of N-glycan core structures have been chemically synthesized and covalently immobilized on a glass surface. The printed structures were then enzymatically diversified by the action of three different glycosyltransferases in nanodroplets placed on top of individual spots of the microarray by a printing robot. Conversion was followed by lectin binding specific for the terminal sugars. This enzymatic extension of surface-bound ligands in nanodroplets reduces the amount of precious glycosyltransferases needed by seven orders of magnitude relative to reactions carried out in the solution phase. Moreover, only those ligands that have been shown to be substrates to a specific glycosyltransferase can be individually chosen for elongation on the array. The methodology described here, combining focused modular synthesis and nanoscale on-chip enzymatic elongation, could open the way for the much needed rapid construction of large synthetic glycan arrays.     

Fucosyltransferases as synthetic tools: glycan array based substrate selection and core fucosylation of synthetic N-glycans

Two recombinant fucosyltransferases were employed as synthetic tools in the chemoenzymatic synthesis of core fucosylated N-glycan structures. Enzyme substrates were rapidly identified by incubating a microarray of synthetic N-glycans with the transferases and detecting the presence of core fucose with four lectins and one antibody. Selected substrates were then enzymatically fucosylated in solution on a preparative scale and characterized by NMR and MS. With this approach the chemoenzymatic synthesis of a series of α1,3-, α1,6-, and difucosylated structures was accomplished in very short time and with high yields, which otherwise would have required extensive additional synthetic effort and a complete redesign of existing synthetic routes. In addition, valuable information was gathered regarding the specificities of the lectins employed in this study.     

Über die Diophantische Gleichungax 4+bx 2 y 2+cy 4=ez 2

Ohne ZusammenfassungEingereicht zur Erlangung des Grades eines Dr. phil. habil. an der Philosophischen Fakultat der Universität Leipzig.     

Untersuchung von Blut und Urin in der Leuk?mie

Ohne Zusammenfassung