Search results for "LAL"
showing 10 items of 1001 documents
Syntheses, crystal structures and magnetic properties of a series of μ-phenoxo-μ1,1-carboxylato-μ1,3-carboxylato trinickel(II) compounds.
2014
The work in this report describes the syntheses, characterization, crystal structures and magnetic properties of eight linear trinickel(ii) compounds of the composition [Ni(II)3(L(sal-pyr))2(propionate)4] (), [Ni(II)3(L(sal-pyr))2(benzoate)4]·CH3CN (), [Ni(II)3(L(sal-pip))2(acetate)4]·2CH3CN (), [Ni(II)3(L(sal-pip))2(propionate)4] (), [Ni(II)3(L(sal-pip))2(benzoate)4]·CH2Cl2 (), [Ni(II)3(L(sal-mor))2(propionate)4] (), [Ni(II)3(L(sal-mor))2(benzoate)4]·3CH2Cl2 () and [Ni(II)3(L(sal-mor))2(o-Cl-benzoate)4]·2CH3CN·2H2O (), where HL(sal-pyr), HL(sal-pip) and HL(sal-mor) are the 1 : 1 condensation products of salicylaldehyde and 1-(2-aminoethyl)-pyrrolidine, 1-(2-aminoethyl)-piperidine and 4-(2-…
Characterization of some triphenyltin(IV) complexes of 5-(arylazo)salicylaldehyde ligands using IR, 1H, 13C, 119Sn NMR and 119Sn Mössbauer spectrosco…
1994
Abstract Coordination complexes of 5-(arylazo)salicylaldehyde with triphenyltin chloride have been prepared and subjected to IR, multinuclear NMR (1H, 13C, 119Sn) and 119Sn Mossbauer spectroscopy. 5-(Arylazo)salicylaldehyde forms two types of complexes viz. triorganotin adducts and phenoxides. In the adducts, the protonated ligand coordinates through the aldehydic oxygen atom while in phenoxides, the coordination occurs via the phenolic oxygen atom and the oxygen atom of the aldehydic group. The spectroscopic data suggest that both types of complexes adopt a cis-trigonal bipyramidal geometry around tin.
Phenylalanine hydroxylase from the sponge Geodia cydonium: implication for allorecognition and evolution of aromatic amino acid HYDROXYLASESfn1fn1The…
1998
Abstract The prophenoloxidase activating system is a defense system, frequently reported both in protostomes and in deuterostomes. The final product of the phenoloxidase activity is melanin which is ubiquitously present throughout the metazoan kingdom. The melanin synthesis pathway starts with the amino acid [aa] phenylalanine which is converted to tyrosine by the phenylalanine hydroxylase [PAH]. We show that after allo-transplantation in the marine sponge Geodiacydonium PAH is upregulated in the grafts. Enzyme determination studies revealed that PAH activity increases by three-fold two d after transplantation and reaches its maximum after 3 d (by 3.7-fold). This finding was supported by de…
Pyrrolide-imine benzyl complexes of zirconium and hafnium: synthesis, structures, and efficient ethylene polymerization catalysis
2004
Abstract A series of pyrrolyl-imines HL1–6 was prepared by the condensation of pyrrole-2-carboxyaldehyde with different amines. The reaction of 2 equiv of pyrrolyl-imine with tetrabenzyl complexes of hafnium and zirconium M(CH2Ph)4 (M=Hf or Zr) gave dibenzyl complexes (L3–6)2M(CH2Ph)2, which were characterized by NMR spectroscopy and crystal structure analysis. NMR spectra of the complexes with secondary alkyl substituents at the imine nitrogen (isopropyl: 3a, 4-tert-butylcyclohexyl: 4a and 4b) suggest that rapid racemization between Δ and Λ configurations occurs in solution on the NMR time scale. The complexes with pyrrolide-imine ligands with a tertiary alkyl group such as tert-butyl (5a …
Enantiomeric separation of amino acids by capillary electrophoresis with α-cyclodextrin
1998
A simple method for separation of underivatized aromatic amino acid enantiomers is presented. The influence of α-cyclodextrin concentration, applied voltage and background buffer pH on the separation were investigated to achieve the best conditions of separation.
The influence of α-aminophosphonic acids on the activity of aminopeptidase from barley seeds—an approach to determine the enzyme specificity
2015
Inhibitory potencies of 24 α-aminophosphonic acids against barley seeds (Hordeum vulgare L.) metallo-aminopeptidase have been determined to evaluate structural requirements of this enzyme. The enzyme was sensitive mostly to the influence of phosphonic acid analogues of phenylalanine and its homologues, thus showing narrow specificity if compared with porcine aminopeptidases M1 and M17 and with Plasmodium aminopeptidase M17.
Conformational studies of hexapeptides containing two dehydroamino acid residues in positions 3 and 5 in peptide chain
2008
Abstract Synthesis and structural studies of hexapeptides containing two dehydroamino acid residues in positions 3 and 5 in a peptide chain were performed. All the investigated peptides adopted bent conformations, stabilized by intramolecular hydrogen bonding, and could exist as two different conformers in solution. Only in the case of the peptide containing ΔAla residues, expected 3 10 -helical conformation was found.
Conformation of dehydropentapeptides containing four achiral amino acid residues - controlling the role of L-valine.
2014
Structural studies of pentapeptides containing an achiral block, built from two dehydroamino acid residues (ΔZPhe and ΔAla) and two glycines, as well as one chiral L-Val residue were performed using NMR spectroscopy. The key role of the L-Val residue in the generation of the secondary structure of peptides is discussed. The obtained results suggest that the strongest influence on the conformation of peptides arises from a valine residue inserted at the C-terminal position. The most ordered conformation was found for peptide Boc-Gly-ΔAla-Gly-ΔZPhe-Val-OMe (3), which adopts a right-handed helical conformation.
Serine/Threonine Phosphatase Inhibitors Decrease Adrenergic Arylalkylamine N -Acetyltransferase Induction in the Rat Pineal Gland
2001
Adrenergic regulation of the pineal enzyme serotonin N-acetyltransferase [arylalkylamine N-acetyltransferase (AA-NAT); EC 2.3.1.87] accounts for the circadian rhythm in melatonin formation. In the present study, the role of protein phosphatases in the adrenergic regulation of rat pineal AA-NAT was investigated using specific inhibitors. In cultured pineals, the serine/threonine phosphatase type 1 and type 2A inhibitors okadaic acid and calyculin A significantly decreased adrenergically or cAMP-induced AA-NAT activity, whereas the serine/threonine phosphatase type 2B inhibitor cypermethrin and tyrosine phosphatase inhibitor dephostatin were ineffective. Reverse transcriptase-polymerase chain…
Transport of amino acids and their phosphonic acid analogues through supported liquid membranes containing macrocyclic carriers. Experimental paramet…
1991
Abstract Amino acid hydrochlorides are well transported through 1-decanol membranes containing Kryptofix 5 or 222 and supported in a porous polyacrylonitrile hollow fiber matrix. Factors which influence the transport of phenylalanine hydrochloride were studied in some detail using this sheet- as well as hollow fibre-supported liquid membranes. These studies show that the choice of the membrane phase, the kind of polymeric support and the mode of membrane preparation are of great importance for the efficiency of the process. The most vital step in the membrane preparation appears to be its activation by soaking in a solution of phenylalanine hydrochloride in a water-ethanol or water-propanol…