Tetraalkylammonium bromides in methanol: Small angle neutron scattering and vapor pressure measurements

Vapor pressure measurements and small angle scattering (SANS) experiments are reported and discussed for bispiperidinium (BP) bromide and n-tetrapentylammonium bromide solutions in methanol at 25°C. The BP⁺ ion which may be considered as a tetraalkylammonium (TAA) ion with pairwise connected alkyl chains, is used for the study of the effects due to flexible TAA alkyl chains. SANS intensities are calibrated with the help of the precise osmotic coefficients from the vapor pressure measurements.     

Synthesis,Structure, and Properties of the High‐Pressure Modification of CePdSn – a 5 K Antiferromagnet

The high‐pressure (HP) modification of CePdSn was synthesized under multianvil high‐pressure (10.5 GPa) high‐temperature (1100 °C) conditions from the normal‐pressure (NP) modification. The structures of both modifications were studied by X‐ray powder and single crystal diffraction: TiNiSi type, Pnma, a = 754.1(2), b = 470.6(1), c = 798.4(3) pm, wR2 = 0.0333, 945 F² values, 20 variables for NP‐CePdSn and ZrNiAl type, , a = 760.03(5), c = 416.06(3) pm, wR2 = 0.0443, 248 F² values, 13 variables for HP‐CePdSn. The structural chemistry of both modifications is goverened by platinum centered trigonal prisms. The platinum and tin atoms in NP‐CePdSn and HP‐CePdSn build up a three‐dimensional [PdSn] network in which the cerium atoms fill channels. Susceptibility measurements on HP‐CePdSn reveal an experimental magnetic moment of 2.55(1) μ_B/Ce atom in the paramagnetic region. At 5 K a paramagnetic‐to‐antiferromagnetic transition is evident from magnetization and specific heat measurements.     

Stereoselective syntheses of piperidinones and their modification by organometallic coupling reactions

Dehydropiperidinones stereoselectively obtained from N-arabinosyl imines were iodinated at the enaminone structure. Knochel iodine-magnesium exchange afforded Grignard compounds of these piperidinone derivatives which reacted, either directly or after transmetalation to zinc or copper intermediates, with alkyl-, aryl- or acylhalides to give correspondingly substituted piperidinones. Stereoselective conjugate allyl cuprate addition to a thus obtained 5-allyl dehydropiperidinone and ring-closing metathesis of the product gave a hydroquinolinone containing three stereogenic centers.     

Determination of telmisartan in human blood plasma: Part I: Immunoassay development

Telmisartan is an angiotensin II receptor antagonist and a known drug against high blood pressure. In this report, the development of a new and rapid analytical technique, an enzyme-linked immunosorbent assay (ELISA) for the determination of telmisartan in human blood plasma is described. The immunoassay is based on a conversion of 4-(N-methylhydrazino)-7-nitro-2,1,3-benzooxadiazole (MNBDH) to 4-(N-methylamino)-7-nitro-2,1,3-benzooxadiazole (MNBDA), which is detected by fluorescence spectroscopy. The limit of detection was 0.1 ng/mL, the limit of quantification was 0.3 ng/mL and the working range extended from 0.3 ng/mL to 300 ng/mL.     

Synthesis and structural model of an alpha(2,6)-sialyl-t glycosylated MUC1 eicosapeptide under physiological conditions

To study the effect of O-glycosylation on the conformational propensities of a peptide backbone, a 20-residue peptide (GSTAPPAHGVTSAPDTRPAP) representing the full length tandem repeat sequence of the human mucin MUC1 and its analogue glycosylated with the (2,6)-sialyl-T antigen on Thr11, were prepared and investigated by NMR and molecular modeling. The peptides contain both the GVTSAP sequence, which is an effective substrate for GalNAc transferases, and the PDTRP fragment, a known epitope recognized by several anti-MUC1 monoclonal antibodies. It has been shown that glycosylation of threonine in the GVTSAP sequence is a prerequisite for subsequent glycosylation of the serine at GVTSAP. Furthermore, carbohydrates serve as additional epitopes for MUC1 antibodies. Investigation of the solution structure of the sialyl-T glycoeicosapeptide in a H(2)O/D(2)O mixture (9:1) under physiological conditions (25 degrees C and pH 6.5) revealed that the attachment of the saccharide side-chain affects the conformational equilibrium of the peptide backbone near the glycosylated Thr11 residue. For the GVTSA region, an extended, rod-like secondary structure was found by restrained molecular dynamics simulation. The APDTR region formed a turn structure which is more flexibly organized. Taken together, the joined sequence GVTSAPDTR represents the largest structural model of MUC1 derived glycopeptides analyzed so far.     

Atomistic Simulation Study of Cu0.327Ni0.673 Alloys: from Solid Solution to Phase Segregation

We present a combined Monte‐Carlo/molecular dynamics study of a Cu_0.327Ni_0.673 alloy system. On the basis of nearest‐neighbor coordination number analyses atomic clustering and phase segregation is explored. Along this line, free energy profiles are calculated and separated into entropic and energetic contributions. The competition of both terms was found in accordance to the experimental phase diagrams (phase separation of the solid solution below about 600 Kelvin). Two independent simulation runs were performed. At 1000 Kelvin the observed configurations correspond to solid solutions exhibiting a weak tendency to cluster atoms of identical species. At room temperature the energetic favoring of atomic separation is clearly dominant and leads to the formation of Ni‐rich and Cu‐rich domains. The latter are separated by interfacial regions whose width ranges from 0.5 to 1 nanometers.     

Vorkommen und quantitative Bestimmung der Milchs?ure im Wein

Ohne Zusammenfassung