Zur Kenntnis sterischer Einflüsse auf Ringschlußreaktionen

Ohne Zusammenfassung     

Harmonisation of coupled calibration curves to reduce correlated effects in the analysis of natural gas by gas chromatography

Quantitative analysis of natural gas depends on the calibration of a gas chromatograph with certified gas mixtures and the determination of a response relationship for each species by regression analysis. The uncertainty in this calibration is dominated by variations in the amount of the sample used for each analysis that are strongly correlated for all species measured in the same run. The "harmonisation" method described here minimises the influence of these correlations on the calculated calibration curves and leads to a reduction in the root-mean-square residual deviations from the fitted curve of a factor between 2 and 5. Consequently, it removes the requirement for each run in the calibration procedure to be carried out under the same external conditions, and opens the possibility that new data, measured under different environmental or instrumental conditions, can be appended to an existing calibration database.     

Nano-hydroxyapatite preparation from biogenic raw materials

Hydroxyapatite (HAp) was successfully produced from recycled eggshell, seashell and phosphoric acid. The phases obtained depended on the ratio of calcined eggshell/ seashell to phosphoric acid, the calcination temperature and the mechanochemical activation method (ball milling or attrition milling). The HAp structures were characterized by X-ray diffraction, scanning electron microsopy and infrared spectroscopy. Attrition milling was more effective than ball milling, yielding nanosize, homogenous and pure Hap.      

Horseradish Peroxidase as a Catalyst for Atom Transfer Radical Polymerization

The hemoprotein horseradish peroxidase (HRP) catalyzes the polymerization of N‐isopropylacrylamide with an alkyl bromide initiator under conditions of activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) in the absence of any peroxide. This is a novel activity of HRP, which we propose to name ATRPase activity. Bromine‐terminated polymers with polydispersity indices (PDIs) as low as 1.44 are obtained. The polymerization follows first order kinetics, but the evolution of molecular weight and the PDI upon increasing conversion deviate from the results expected for an ATRP mechanism. Conversion, and PDI depend on the pH and on the concentration of the reducing agent, sodium ascorbate. HRP is stable during the polymerization and does not unfold or form conjugates.

     

Synthesis of New Pyrroline Nitroxides with Ethynyl Functional Group

3-Substituted and 3,4-disubstituted pyrroline nitroxides containing an ethynyl group or two ethynyl groups were achieved by the reaction of a paramagnetic aldehydes with dimethyl (1-diazo-2-oxopropyl)phosphonate (Bestmann–Ohira reagent). The new compounds containing an ethynyl group were found to be useful building blocks in Sonogashira coupling, cyclization, and cycloaddition reactions producing potentially “azido-specific” cross-linking spin labels, paramagnetic ligands, and polyradical scaffolds.     

Surface Modification of Gold Nanoprisms and Their Self-Assembly with Nanospheres

Controlled surface modification of gold particles is of central importance for the preparation of functional nano-objects, which can be used both in fundamental research and in advanced photonic or nanomedicine applications. In this study, the surface modification of gold nanoprisms using different thiols, namely cysteamine, (16-mercaptohexadecyl)trimethylammonium bromide (MTAB), and α-methoxy-ω-mercapto polyethylene glycol (mPEG-SH (5000 Da)) is investigated. The aim is to prepare binary surface-modified thiol/PEG patchy gold nanoprisms, where the tips/edges and the face regions of the particles are covered by different thiol moieties. By investigating the time evolution of the prisms’ extinction spectra at different capping ligand concentration levels, the conditions to prepare such “patchy” particles are identified. While significantly faster adsorption kinetics are observed for MTAB compared to cysteamine, both molecule types can be used to prepare binary surface-modified thiol/PEG particles. Prisms modified with only MTAB or PEG and subsequently assembled with negatively charged spheres show that MTAB forms hetero-aggregates with the spheres, while PEG prevents particle attachment. For thiol (cysteamine or MTAB)/PEG binary surface-modified prisms, it is found that the efficiency of sphere attachment at the tip/side region during self-assembly is rather low, most likely due to the presence of PEG.     

trans-Resveratrol and trans-Piceid Content of Hungarian Wines

Plant polyphenols are naturally occurring secondary plant metabolites, synthesized in response to environmental stress factors. As anti-oxidants and free-radical scavengers they serve as essential components of the human diet. Among polyphenols well studied representatives are the trans-resveratrol and trans-piceid molecules, the latter being the glycoside of trans-resveratrol. trans-Resveratrol is known to have anti-inflammatory, anti-tumor, cardio- and vasoprotective effects which help in the prevention of chronic cardiovascular and tumorous diseases.

In the present study, 42 Hungarian wines were analyzed using LC-DAD detection. The wines were from Villány and Eger wine regions representing three wineries from 2003 to 2007 vintage years. The trans-resveratrol amount in the processed wines ranged from 0.75 to 10.4 mg mL⁻¹ and for trans-piceid from 0.1 to 3.7 mg mL⁻¹.