Methods for the synthesis of 5,6,7,8-tetrahydro-1,8-naphthyridine fragments for alphaVbeta3 integrin antagonists

The preparation of 3-(5,6,7,8-tetrahydro-1,8-naphthyridin-2-yl)propan-1-amine 2a and 3-[(7R)-7-methyl-5,6,7,8-tetrahydro-1,8-naphthyridin-2-yl]propan-1-amine 2b, key intermediates in the synthesis of alpha(V)beta(3) antagonists, is described. The syntheses rely on the efficient double Sonogashira reactions of 2,5-dibromopyridine 3 with acetylenic alcohols 4a/4b and protected propargylamines 10a-e followed by Chichibabin cyclizations of 3,3'-pyridine-2,5-diyldipropan-1-amines 9a/9b.     

Enhanced photocatalytic degradation of nitrobenzene using MWCNT/β-ZnMoO4 composites under UV light emitting diodes (LEDs)

The β-ZnMoO₄/MWCNT nanocrystal composites were synthesized using hydrothermal method. The physicochemical properties such as structure, morphology and bandgap of synthesized photocatalysts were characterized using PXRD, UV-vis DRS, FTIR, FT-Raman, SEM and TEM analytical methods. PXRD pattern shows the peak shift in the case of synthesized ZnMoO₄/MWCNT which confirms the formation of nanocomposites. Moreover, the strong absorbance in UV region which was evidenced in UV-vis DRS spectra for all the case of synthesized ZnMoO₄ and ZnMoO₄/MWCNT composites. From the SEM and TEM images, the MWCNT was found to have adhered over the ZnMoO₄ nanocrystals. Compared to bare β-ZnMoO₄, β-ZnMoO₄/MWCNT nanocrystal composites exhibited significant higher photocatalytic activity under ultraviolet light emitting diodes (UVLEDs) irradiation for the degradation of nitrobenzene (NB; 2.606 × 10^?4 M). This may be due to the effective charge transfer in the composite and optimized electron hole pair recombination. The photocatalytic activity of the synthesized photocatalysts was also studied under visible LEDs and it is observed that the photocatalytic degradation of NB was 97%, 77%, 65% and 52% under the irradiation of UV, blue, green, and red LEDs respectively.     

Precipitation of metal-cupferron complexes from homogeneous solution-I: determination of copper

The cupferron complex of copper has been precipitated from homogeneous solution by the addition of phenylhydroxylamine and sodium nitrite to a cold, acidic solution containing copper(II) ions. The precipitate can be dried at 90 +/- 5 degrees and weighed without ignition to the oxide. Less than 3 mg of copper can be determined. A fairly high concentration of acetic acid is tolerable. Separation from large quantities of zinc, nickel and silver has been achieved.     

Synthesis and characterisation of trisarylphosphine selenides: Further insight into the effect of fluoroalkylation on the electronic properties of trisarylphosphines

Variations in the magnitude of the ¹J_SeP coupling constants for a range of phosphorus(V) selenides allow the efficiency of different spacer groups at insulating the phosphorus centre in triarylphosphines from highly electron-withdrawing perfluoroalkyl groups to be established.     

Comparison of the results for the analysis of individual chlorobiphenyl congeners in various interlaboratory exercises

A comparison is made between interlaboratory studies in which individual chlorobiphenyls (CBs) are measured in fish and sludge samples. The target coefficient of variation (CV(R)) between laboratories at CB levels of 0.01–1.0 mg/kg should be in the order of 20–30%. An improvement in the CV(R) is clearly shown in studies in which a learning program, paying attention to the optimization of gas Chromatographic operating conditions, is included. For standard solutions, where no interference problems of the matrix occur, excellent CV(R)s are obtained in the order of 6%. In fish oil CV(R)s of 10–30% and in sludge CV(R)s of 20–30% are reached.     

Clenbuterol plasma pharmacokinetics in cattle.

The pharmacokinetics of clenbuterol (Cb) were investigated to determine the extent to which analysis of plasma concentration can be used to discriminate between therapeutic and illicit growth promoting treatment of cattle. Analysis of plasma concentration enabled assessment of the extent of differences in pharmacokinetics between such dosing regimens. Cattle were treated with Cb using either a therapeutic (20 calves, 0.8 microgram Cb kg-1, twice daily in feed for 10 days), or growth promoting (30 calves, 10 micrograms Cb kg-1, twice daily by drench for 20 days) dosing regimens. Blood samples were collected by jugular venepuncture, and plasma Cb concentrations determined by direct enzyme immunoassay. To determine plasma pharmacokinetics, use of a two compartment model was applied to the data and revealed that steady state kinetics were reached after 3 and 5 days following initiation of therapeutic and growth promoting dosing regimens, respectively. Tolerance limit analysis of concentrations during the therapeutic regimen indicated that a plasma Cb concentration greater than 1.63 ng ml-1 would be indicative (p < 0.01) of a growth promoting dose.     

Correction and extension of ``Measurable quotients of unipotent translations on homogeneous spaces"

The statements of Main Theorem 1.1 and Theorem 2.1 of the author's paper [Trans. Amer. Math. Soc. 345 (1994), 577-594] should assume that is discrete and is connected. (Corollaries 1.3, 5.6, and 5.8 are affected similarly.) These restrictions can be removed if the conclusions of the results are weakened to allow for the possible existence of transitive, proper subgroups of . In this form, the results can be extended to the setting where is a product of real and -adic Lie groups.

     

Solid-state 2H NMR studies of the effects of cholesterol on the acyl chain dynamics of magnetically aligned phospholipid bilayers

We report the utilization of magnetically aligned phospholipid bilayers (bicelles) to study the effects of cholesterol in phospholipid bilayers for both chain perdeuterated DMPC and partially deuterated alpha-[2,2,3,4,4,6-d(6)]-cholesterol using (2)H solid-state NMR spectroscopy. The quadrupolar splittings at 40 degrees C were 25.5 and 37.7 kHz, respectively, for the 2,4-(2)H(eq) and 2,4-(2)H(ax) deuterons when the bilayer normal of the discs was aligned perpendicular to the static magnetic field. The quadrupolar splittings were doubled when Yb(3+) ions were added to flip the bicelles 90 degrees such that the bilayer normal was colinear with the magnetic field. The results suggest that cholesterol is incorporated into the bicelle discs. For chain perdeuterated DMPC-d(54), incorporated into DMPC-DHPC bicelle discs, the individual quadrupolar splittings of the methylene and methyl groups doubled on going from the perpendicular to the parallel alignment. Also, the presence of cholesterol increased the overall ordering of the acyl chains of the phospholipids. S(CD) (i) calculations were extracted directly from the (2)H quadrupolar splittings of the chain perdeuterated DMPC. The order parameter, S(CD) (i), calculations clearly indicated an overall degree of ordering of the acyl chains in the presence of cholesterol. We also noted a disordering effect at higher temperatures. This study demonstrates the ease with which (2)H order parameters can be calculated utilizing magnetically aligned phospholipid bilayers when compared with randomly dispersed membrane samples.     

New insight in the role of modifying ligands in the sol-gel processing of metal alkoxide precursors: A possibility to approach new classes of materials

This paper summarizes recent literature data and presents new experimental data on the mechanisms of chemical modification, hydrolysis and polycondensation of the alkoxides and demonstrates possibilities to approach new classes of materials, exploiting these mechanisms. Low reactivity of silicon alkoxides is improved by either basic catalysis exploiting an S_N2 mechanism or acidic catalysis facilitating a proton-assisted S_N1 mechanism as well as by modification with chelating ligands. Metal alkoxides are much stronger Lewis bases compared to silicon alkoxides and the acidity of water is strong enough to achieve their rapid hydrolysis via proton-assisted S_N1 pathway even in the absence of additional catalysts. Introduction of the modifying chelating ligands is leading generally to increased charge distribution in the precursor molecules. Modifying chelating ligands are also appreciably smaller than the alkoxide ligands they replace. The modification with chelating ligands is thus facilitating the kinetics of hydrolysis and polycondensation. The size and shape of the primary particles formed in sol-gel treatment of metal alkoxides are defined not by kinetic factors in their hydrolysis and polycondensation but by the interactions on the phase boundary, which is in its turn directed by the ligand properties. The products of the fast hydrolysis and condensation sequence consist of micelles templated by self-assembly of ligands (mainly oxo-species). This concept provides explanations for commonly observed material properties and allows for the development of new strategies for the preparation of materials. We discuss the formation of inverted micelles, obtained by the appropriate choice of solvents, which allows for the formation of hollow spheres. The modifying β-diketonate ligands act as the surfactant and form an interface between the hollow sphere and the solvent. Retention of ligands inside the gel particles is possible only if ligands possessing both chelating and bridging properties are applied. Application of such ligands, for example, diethanolamine, permits to prepare new transition metal oxide based microporous membranes.     

Electron paramagnetic resonance studies of magnetically aligned phospholipid bilayers utilizing a phospholipid spin label

X-band electron paramagnetic resonance (EPR) spectroscopy was used to study the structural and dynamic properties of magnetically aligned phospholipid bilayers utilizing a variety of phosphocholine spin labels (PCSL) as a function oftemperature. 1-Palmitoyl-2-[n-(4,4-dimethyloxazolidine-N-oxyl)stearoyl]-sn-glycero-3-phosphocholine (n-PCSL) in which a nitroxide group was attached to the different acyl chain positions of the phospholipid (n = 5, 7, 12, and 14) were used as an EPR spin probe to investigate magnetically aligned phospholipid bilayers from the plateau (near to the headgroup) region to the end of the acyl chain (center of the bilayers). The addition of certain types of paramagnetic lanthanide ions changes the overall magnetic susceptibility anisotropy tensor of the bicelles, such that the bicelles flip with their bilayer normal either parallel or perpendicular to the magnetic field. The present study reveals for the first time that, in the case of the n-PCSL, the bilayer normal is aligned parallel and perpendicular to the magnetic field in the presence of lanthanide ions having positive delta(chi) (e.g., Tm3+) and negative delta(chi) (e.g., Dy3+), respectively. The magnetic alignment of the bilayers and the corresponding segmental molecular order parameter, S(mol), were investigated as a function of the temperature. The S(mol) values decrease in the following order, 5-PCSL > 7-PCSL > 12-PCSL > 14-PCSL, for the magnetically aligned phospholipid bilayers. Also, the variable temperature study indicates that, by increasing the temperature, the order parameters S(mol) decreased for all the n-PCSLs. The results indicate that magnetically aligned phospholipid bilayers represent an excellent model membrane system for X-band EPR studies.