Ein Kongruenzsatz für Eiflächen

In this note we will show that two ovaloids with the same second fundamental form and the same mean curvature are congruent. The proof will be based on the index theorem of Poincaré.     

5-Cyanoimino-4-oxomethylene-4,5-dihydroimidazole and 5-cyanoamino-4-imidazolecarboxylic acid intermediates in nitrosative guanosine deamination: evidence from 18O-labeling experiments

The nitrosative deaminations (37 degrees C, NaNO2, NaAc buffer, pH 3.7) of guanosine 1r in (18O)water (97.6%) and of [6-18O]-1r in normal water were studied. [6-(18)O]-1r was prepared from 2-amino-6-chloropurine riboside using adenosine deaminase. The reaction products xanthosine 3r and oxanosine 4r were separated by HPLC and characterized by LC/MS analysis and 13C NMR spectroscopy. The 18O-isotopic shifts on the 13C NMR signals were measured and allowed the identification of all isotopomers formed. The results show that oxanosine is formed via 5-cyanoimino-4-oxomethylene-4,5-dihydroimidazole, 5, and its 1,4-addition product 5-cyanoamino-4-imidazolecarboxylic acid, 6. This hydration of 5 to 6 leads to aromatization and greatly dominates over water addition to the cyanoimino group of 5 to form 5-guanidinyliden-4-oxomethylene-4,5-dihydroimidazole, 7. 5-Guanidinyl-4-imidazolecarboxylic acid, 8, the product of water addition to 6, is not involved.     

Improved resolution power of electrophoretic fractionation of DNA using a voltage gradient "up and down" application

The improved resolution power of electrophoretic fractionation of DNA in a wide range of molecular masses is demonstrated using an "up and down" application of voltage gradient gel electrophoresis (VGGE). This application also allows separation of different DNA fragments which are poorly fractionated in conventional electrophoresis.     

An advanced double column-switching technique (LC-LC) for liquid chromatography/electrospray ionisation tandem mass spectrometry for fully automated analysis of caspofungin

Caspofungin (MK-0991; L-743,872) is the first representative of a new important class of antifungal agents, the glucan synthesis inhibitors. To the authors' best knowledge, to date only one high-performance liquid chromatography (HPLC) method has been published for the determination of caspofungin in serum. Severe difficulties with sorption were described. We developed a new method which addresses these difficulties using an advanced column-switching technique for fully automated analysis of caspofungin in serum without any pre-treatment. Extraction was performed automatically inline, using a diol column, followed by chromatography on a CN column. Detection was performed by electrospray ionisation tandem mass spectrometry (ESI-MS/MS) with isolation and fragmentation in the positive ion mode. Total analysis time was 30 min. Detection of caspofungin was achieved by retention time, isolation and fragmentation of the double positively charged caspofungin ion. This LC/MS assay was validated for between-run accuracy (max. 110%) and precision (max. CV 16.1%). The lower limit of quantification was 0.2 microg/mL. The analytical method with fully automated inline extraction of caspofungin described here removes the need for difficult and time-consuming sample pre-treatment. Sorption of caspofungin is not of importance. Additional advantages of the new method are that only a small quantity of serum (5 microL) is needed and that the method is very specific.     

Vibronic coupling in the ground and excited states of the naphthalene cation

The hole-vibrational coupling in naphthalene is studied using high-resolution gas-phase photoelectron spectroscopy and density functional theory calculations (DFT), and a remarkable increase of the coupling with low-frequency vibrations is observed in the excited states.     

Mononuclear precursor for MOCVD of HfO2 thin films

We report the precursor characteristics of a novel mononuclear mixed alkoxide compound [Hf(O(i)Pr)2(tbaoac)2] and its application towards MOCVD of HfO2 thin films in a production tool CVD reactor.     

Mesoionic bora-tetraazapentalenes--fully reversible two step redox systems

Bora-tetraazapentalenes have been synthesised and characterized; the radical anion shows an unusual thermodynamic stability (semiquinone formation constants K(SEM) of ca. 10(14)).