Zur Bestimmung der Phosphors?ure

Ohne Zusammenfassung     

Binding affinity studies of 1,2,3-triazole copper(II) complexes to human serum albumin

Abstract

Two copper(II) complexes with tetradentate 1,4-disubstituted-1,2,3-triazole ligands, [CuL(MeCN)](ClO₄)₂ (1) and [CuL′](ClO₄)₂ (2), have been prepared and characterized by different techniques, including X-ray structure determination, spectroscopic, and electrochemical measurements, as reported elsewhere. Herein, we report the interactions of these complexes, and corresponding free ligands, with human serum albumin (HSA) verifying their relative thermodynamic stability and differences in binding to this protein. Interactions with HSA were verified by CD measurements monitored at 564?nm, up to stoichiometric ratio 2:1 [Complex]:[protein], according to competitive equilibria involving the insertion of copper at the selective N-terminal metal binding site in HSA, and additionally at a secondary nonselective site. Further interactions of these complexes with L-tryptophan residues, and probable supplementary site(s) for the binding, were followed by fluorescence measurements. Analogous experiments with the free L and L′ indicated much weaker interactions. Protein oxidation damage was observed for both complexes, monitored by carbonyl groups formation in the presence of H₂O₂, probably with the participation of reactive oxygen species. Density functional theory calculations exhibit metal-ligand binding interaction energies similar to [Cu(HSA-N_terminal)]⁺, and reinforced the experimental results, showing clearly that such triazole ligands are competitive toward copper(II) in biological medium.     

High-performance liquid chromatographic analysis of 5-ethylpyrimidines and 5-methylpyrimidines in plasma

A high-performance liquid chromatographic (HPLC) method employing a C18 reversed-phase column, a mobile phase of sodium acetate and methanol, and an ultraviolet detector was developed for the analysis of 5-ethylpyrimidines and 5-methylpyrimidines in plasma. Samples were prepared for HPLC by sequential cation-exchange and anion-exchange column chromatography. Linear standard curves were obtained for samples containing 0.05-50 micrograms/ml 5-ethyl-2'-deoxyuridine and 5-ethyluracil, 0.05-10 micrograms ml 5-(1-hydroxyethyl)uracil, and 0.1-50 micrograms/ml thymidine, thymine and 5-hydroxymethyluracil. Applicability of the method to determination of the kinetics of 5-ethyl-2'-deoxyuridine elimination by the isolated perfused rat liver was demonstrated; clearance of the drug was 1.29 ml/min.     

Structural and electronic evolution of the As(OH)3 molecule in high temperature aqueous solutions: an x-ray absorption investigation

The geometrical and electronic structure of the arsenious acid molecule As(OH)(3) in aqueous solutions has been investigated by x-ray absorption spectroscopy (XAS) within extended x-ray absorption spectroscopy (EXAFS) and x-ray absorption near edge structure (XANES), using realistic first-principle calculations in the latter case. This investigation was performed on aqueous solutions of arsenious acid from ambient to supercritical conditions (P = 250 and 600 bars, T 相似文献   

Heat transfer modelling in a polymer sample located in a microwave field

This work presents the modelling of heat transfer in a polymer sample submitted to a microwave field in the quartz column of a dilatometer surrounded by vacuum to avoid convection. The temperature rise is studied in transient state by the finite element method. It is assumed that a uniform and constant heat production is maintained in the entire volume of the sample. It is shown that it is possible to design the set composed of the sample and of the column to achieve a nearly uniform temperature in the whole volume of the sample while its temperature is raised from 20 to 250°C at a heating rate of 5 deg·min^?1.     

Influence of the thickness and polarization charges on the electro-optical behaviour of twisted smectic C* cells

This paper reports on the influence of both polarization charges and thickness on the light transmitted by twisted smectic C* (TSC) liquid crystal (LC) cells. A uniaxial model, based on the de Vries eigenmodes usually used for twisted structures like cholesteric LCs, is used to calculate the transmission variation of the TSC cells as a function of applied voltage or thickness for various values of spontaneous polarization. The results obtained are in quantitative agreement with experimental results found in the literature and emphasize the importance of polarization charges on the behaviour of TSC cells. The TSC light transmission exhibits a profile resembling the so-called V-shaped switching.     

Loss of single-molecule-magnet behavior of a Mn12-based compound assembled in a monolayer

Magnetic circular dichroism magnetization measurements on a monolayer of single molecule magnets have been performed and the results are presented. At the measurement temperature (2 K) the hysteresis cycle shows no opening, contrary to what is seen in the bulk with SQUID magnetometry. This result could surprisingly imply that XMCD is unsuited for such measurements given the fact that it excites the core electrons at the origin of the magnetism. This result could also mean that the blocking temperature is greatly decreased or that these molecules loose their hallmark when deposited as adsorbed films, precluding therefore their much sought-after use in magnetic memories.     

Efficient Syntheses of Methyl 2-Amino-2-Deoxy-3,4,6-Tri-O-Benzyl-α-D-Glucopyranoside and its 2-tert-Butoxycarbonylamino- and 2-Methylamino Derivatives from N-Acetyl-D-Glucosamine

ABSTRACT

The synthesis of the title compounds started with N-acetylglucosamine which was converted into the corresponding methyl glycoside and O-protected with benzyl groups. Subsequent N-protection as its N-BOC-N-acetyl derivative and sequential removal of the N-acetyl group and of the BOC group led in good yield to the target compounds in multigram amounts.