Search results for "ACIDS"
showing 10 items of 3520 documents
Coordination ability of pentapeptides with two dehydro-amino acid residues inserted into their sequences.
2004
The study on the binding ability of tested ligands have shown that insertion of two dehydro-amino acid residues into peptide sequences makes them more effective in metal ion binding than ligands with one dehydro-amino acid residue. The ligand with two Z(Delta)Phe residue form more stable complexes than his analogues with one Z(Delta)Phe residue. Interesting is this that position of Z(Delta)Phe residue in peptide chain have impact on Cu(II)-complexes formation.
ChemInform Abstract: Synthesis of Functionalized Indoles with an α-Stereogenic Ketone Moiety Through an Enantioselective Friedel-Crafts Alkylation wi…
2010
Chiral complexes of BINOL-based ligands with hafnium tert-butoxide catalyze the enantioselective Friedel-Crafts alkylation of indoles with (E)-1,4-diaryl-2-butene-1,4-diones at room temperature, with good yields and ee up to 94%. Hafnium(IV) was found to be a more effective Lewis acid than other frequently used metal ions such as titanium(IV) or zirconium(IV). Unlike the enantioselective Friedel-Crafts alkylation of indoles with α,β-unsaturated compounds where the stereogenic center is generated in the β-position to a carbonyl group, the Friedel-Crafts alkylation with 2-butene-1,4-diones described here generates an α-stereogenic center with respect to one of the carbonyl groups. This can be…
Synthesis of Functionalized Indoles with an α-Stereogenic Ketone Moiety Through an Enantioselective Friedel-Crafts Alkylation with (E)-1,4-Diaryl-2-b…
2009
Chiral complexes of BINOL-based ligands with hafnium tert-butoxide catalyze the enantioselective Friedel-Crafts alkylation of indoles with (E)-1,4-diaryl-2-butene-1,4-diones at room temperature, with good yields and ee up to 94%. Hafnium(IV) was found to be a more effective Lewis acid than other frequently used metal ions such as titanium(IV) or zirconium(IV). Unlike the enantioselective Friedel-Crafts alkylation of indoles with α,β-unsaturated compounds where the stereogenic center is generated in the β-position to a carbonyl group, the Friedel-Crafts alkylation with 2-butene-1,4-diones described here generates an α-stereogenic center with respect to one of the carbonyl groups. This can be…
Chemical and acidic composition of Longissimus dorsi muscle of Comisana lambs fed with Trifolium subterraneum and Lolium multiflorum
2010
Aim of this study was to evaluate the effects of grazing on Trifolium subterraneum and Lolium multiflorum, as pure or associated crops, on the chemical composition and on the fatty acid profile of the intramuscular lipids of the meat of lambs. Forty Comisana male lambs, on average weighing 13.75±1.90 kg, were divided into four homogenous groups of ten and called, in relation to the diet: group T those grazing on T. subterraneum; Group L on L. multiflorum; Group TL on adjacent monocultures of T. subterraneum and L. multiflorum (66.6 and 33.3% of surface, respectively); Group LT on adjacent monocultures of T. subterraneum and L. multiflorum (33.3 and 66.6% of surface, respectively). Every 10 …
EFFECTS OF CYCLOPROPENOID FATTY ACIDS (BAOBAB SEED OIL) ON THE FATTY ACID PROFILE OF LIPIDS FROM DIFFERENT TISSUES IN THE RAT
1996
Rats were fed for 8 weeks a diet containing either Baobab seed oil (FBO) rich in cyclopropenoid fatty acids (CPFA) or heated oil (HBO) devoid of CPFA. In FBO rats, compared to controls (CO), the monounsaturated fatty acid content of adipose tissue lipids, liver triacylglycerols, liver and adrenal cholesteryl esters and liver, kidney, adrenal phospholipids were highly decreased to the benefit of saturated fatty acid content. In cholesteryl esters and phospholipids, the arachidonic acid (20:4 n-6) content was markedly decreased, especially in adrenals. In adrenal cholesteryl esters, adrenic acid (22:4 n-6) content was decreased more than its precursor. The effects of HBO on the tissue lipid f…
Lauroyl peroxide as thermal initiator of lauryl methacrylate monolithic columns for CEC
2008
The preparation of lauryl methacrylate (LMA)-based monolithic columns for CEC using lauroyl peroxide (LPO) as thermal initiator of polymerization has been investigated. The influence of initiator amount and composition of porogenic solvent on the physical and electrochromatographic properties of the resulting LMA-based monoliths was evaluated. A comparison with LMA-based columns thermally polymerized with AIBN was performed. At a given porogenic solvent composition, LMA stationary phases initiated with LPO showed higher permeabilities and better efficiency values than those prepared using AIBN as initiator. The optimum polymerization mixture found for LPO initiator provided a minimum plate …
New high-performance liquid chromatography-based methodology for monitoring the conformational transitions of self-associating hydrophobic peptides, …
1988
A new high-performance size-exclusion chromatographic strategy is reported for the analysis of the hydrophobic self-associating peptide gramicidin A, incorporated into artificial phospholipid vesicles (liposomes). The method is based on the direct injection of a few microlitres of the gramicidin A-containing liposome suspension into the column, which is eluted with a non-polar solvent, such as tetrahydrofuran. The type and amount of information which can be derived from this methodology have been evaluated. Using this chromatographic approach, a correlation has been unambiguously shown to exist between the organization of the peptide in the vesicles and a number of variables involved in the…
Effect of phosphatydylcholine on spectral properties and photostability of 3,3′-diethyloxadicarbocyanine iodide (DODCI) — a potent anti-tumor photose…
1998
Abstract The potential anti-tumor photosensitizer 3,3′-diethyloxadicarbocyanine iodide (DODCI) has been immobilized in dimyristoyl phosphatidylcholine (DMPC) vesicles. Binding of the dicarbocyanine to the lipid vesicles induces several changes in the electronic absorption, emission and excitation spectra of the dye. The monomeric dye molecules exist in at least two forms when immobilized in the DMPC liposomes and the non-luminescing H-aggregates of the dye show efficient excitation energy transfer to the DODCI monomers. Entrapment of the dye in the liposomes generally decreases the photostability of DODCI. While emission from singlet oxygen (1O2) has not been recorded, indirect results sugg…
Linked Benzylamido-Cyclopentadienyl Ligands: Synthesis and Characterization of Alkyl Titanium Complexes
1997
Titanium complexes of the general type Ti(η5:η1-C5H4Si-Me2NCH2C6H3X2-2,5)Cl2 (XH, F), containing a linked benzylamido-cyclopentadienyl ligand, were prepared by reaction of Ti(η5-C5H4SiMe2Cl)Cl3 with lithium amide Li(NHCH2C6H3X2-2,5). A single-crystal X-ray structural analysis of Ti(η5: η1-C5H4SiME2NCH2C6H3F2-2,5)Cl2 revealed a conformation in the solid state in which the aryl ring is turned away from the metal center. Ti(η5:η1-C5H4SiMe2NCH2C6H5)Cl2 can be alkylated with a variety of reagents to form extremely sensitive complexes of the type Ti(η5-C5H4SiMe,2NCH2C6H5)R2 (RMe, CH2 C6H5, CH2SiME3, CH2CMe2C6H5). Reaction of Li2[C5Me4SiMe2NCH2C6H5] with TiCl3(THF)3 gave Ti(η5: η1-C5Me4SiMe2NCH2C6…
Synthesis of glycosylated β3-homo-threonine conjugates for mucin-like glycopeptide antigen analogues
2010
Glycopeptides from the mucin family decorated with tumour-associated carbohydrate antigens (TACA) have proven to be important target structures for the development of molecularly defined anti-cancer vaccines. The strategic incorporation of β-amino acid building blocks into such mucin-type sequences offers the potential to create pseudo-glycopeptide antigens with improved bioavailability for tumour immunotherapy. Towards this end, TN and TF antigen conjugates O-glycosidically linked to Fmoc-β3-homo-threonine were prepared in good yield via Arndt–Eistert homologation of the corresponding glycosyl α-amino acid derivative. By incorporation of TN-Fmoc-β3hThr conjugate into the 20 amino acid tand…