Search results for "phenylalanine"
showing 10 items of 193 documents
Immunological detection of phenylalanine hydroxylase protein in Drosophila melanogaster.
1992
A monoclonal antibody raised against monkey liver phenylalanine hydroxylase (PAH) has been used to detect this protein in Drosophila melanogaster. A cross-reacting material (CRM) band of apparent molecular mass 50-52 kDa, equivalent to that deduced for the Drosophila melanogaster PAH protein based on the pah gene cDNA sequence, has been detected. This CRM was analysed throughout development and showed an equivalent pattern to that reported for PAH activity in this insect, with maxima at pupariation and at pharate adult formation. Distribution of this CRM in larval tissues, the haemolymph and the adult body is mainly restricted to the larval fat body and the adult head. Demonstration of this…
Azide and chloride binding to carboxypeptidase A in the presence of L-phenylalanine
1990
The interaction of chloride with native and cobalt (Co)-substituted carboxypeptidase-A (CPD) has been investigated by 35Cl nuclear magnetic resonance (NMR) spectroscopy in the presence and absence of L-Phe. The affinity constants of azide and chloride toward the Co(II)CPD·L-Phe complex have been measured by electronic spectroscopy. The correlation times determining T1 and T2 for the 35Cl nuclei are related to movements inside the cavity. In the presence of L-Phe, the anions bind to the metal with a relatively high affinity at pH values below 6. Anion binding to the Co enzyme can be analyzed in terms of the three protonation state model for the enzyme (EH2 α EH α E). In the presence of L-Phe…
METABOLIC PROMOTERS AFFECT YIELD AND FRUIT QUALITY OF 'SANFILIPPARA' AND 'TRABIA' LOQUAT
2015
Preliminary field trials with foliar applications of phenylalanine, methionine, oxylipins and sugars have shown improvements of external color, sugar content and uniformity of maturation in grapes, pome fruits, tomatoes and melons. In this study, we hypothesized that similar improvements could be obtained both in fruit of âTrabiaâ and âSanfilipparaâ loquat (Eriobotrya japonica Lindl.) with applications of a commercial formulate called Sunred (Biolchim, Bologna, Italy) and containing various concentrations of the above metabolic promoters. The study was conducted on 12 âSanfilipparaâ and 12 âTrabiaâ adult loquat trees grown in an orchard near Palermo, Italy. Half of the trees…
The Structural Diversity of Benzofuran Resorcinarene Leads to Enhanced Fluorescence
2014
An unexpected and previously unknown resorcinarene mono-crown with a fused benzofuran moiety in its macrocyclic core was obtained as a byproduct from a bridging reaction of tetramethoxy resorcinarene with tetraethylene glycol ditosylate. The formation of the fused benzofuran moiety in the resorcinarene macrocycle resulted in a unique rigid and puckered boat conformation, as shown by XRD studies in the solid state. Modification of the macrocycle was also observed to affect the photophysical properties in solution by enhancing the fluorescence brightness compared with a conventional resorcinarene macrocycle. The fluorescent properties enabled unique detection of structural features, that is, …
Micellar liquid chromatographic separation of amino acids using pre- and post-column o -phthalaldehyde/ N -acetylcysteine derivatization
2000
Abstract The isocratic analysis of primary proteic amino acids using a C18 column, micellar mobile phases of sodium dodecyl sulphate (SDS) and 1-propanol at varying pH, and pre- and post-column formation of the o-phthalaldehyde (OPA)/N-acetyl- l -cysteine (NAC) isoindoles, is examined. An interpretive optimization strategy was applied to find the best separation conditions. For this purpose, empirical polynomial models were used to describe the elution behavior of the isoindoles and free amino acids, using as separation factors the concentrations of surfactant and modifier (two-factor problem), or these two factors and the pH of the mobile phase (three-factor problem). The separation of the…
(p-Sulfomethyl)phenylalanine as a mimic of O-sulfatyl-tyrosine in synthetic partial sequences of P-Selectin glycoprotein ligand 1 (PSGL-1)
2007
Abstract Fmoc- l -( p -sulfomethyl)phenylalanine, a bioisosteric mimic of acid-sensitive O -sulfatyl tyrosine, was synthesized from l -tyrosine according to a novel route. Partial sequences of the recognition site of P-Selectin glycoprotein ligand 1 (PSGL-1), which contain (sulfomethyl)phenylalanine were synthesized on solid-phase. By fragment condensation, a sialyl Lewis x peptide conjugate containing a (sulfomethyl)phenylalanine mimic of O -sulfatyl tyrosine was prepared without destruction of the acid-sensitive fucoside bond within the saccharide side chain. Compounds of this type are of interest as sufficiently acid-stable potential inhibitors of P-Selectin in inflammatory processes.
Influence of the pH on the behavior of an imprinted polymeric stationary phase--supporting evidence for a binding site model.
2001
The equilibrium isotherms of the two enantiomers of phenylalanine anilide (PA) were measured by conventional frontal analysis at three different pH on a thermally-treated imprinted stationary phase selective for the L enantiomer. The first of these pH (buffer pH=3.0, pH(app)=4.0) is well below the apparent pKa (6.4) of the two solutes, the second (buffer pH=5.8, pH(app)=7.0) slightly below this pKa, and the third (buffer pH=7.0, pH(app)=8.3) well above it. The experimental data were fitted to several isotherm models. The best estimates of the parameters of these models are reported and discussed. The corresponding isotherms are compared with the experimental ones. The contributions of the e…
Chiral recognition of protected amino acids by means of fluorescent binary complex pyrene/heptakis-(6-amino)-(6-deoxy)-β-cyclodextrin
2006
The ability of the binary complex pyrene (Py)/heptakis-(6-amino)-(6-deoxy)-β-cyclodextrin (am-β-CD) to act as a chiral selector was tested at two pH values (8.0 and 9.0). Phenylalanine (Phe), methionine (Met) and histidine (His) were used as chiral model molecules. The stability of ternary complexes Py/am-β-CD/amino acid was determined by means of spectrofluorimetric measurements. The data collected showed an increase in stability going from the binary to ternary complex and above all the possibility to use the binary complex as a chiral selector. Finally, data collected at two pH values showed that the binary complex is a better chiral selector when charged rather than in its neutral form.
Determination of optical purity of phosphonic acid analogues of aromatic amino acids by capillary electrophoresis with alpha-cyclodextrin.
2000
A simple and efficient method for the determination of enantiomeric purity of structurally diverse phosphonic and phosphinic acid analogues of phenylalanine and phenylglycine using capillary electrophoresis is presented. These preliminary studies indicated that the enantiomer separation is strongly dependent on the structure of the aminophosphonic acid.
Developmental and biochemical studies on the phenylalanine hydroxylation system in Drosophila melanogaster
1992
Abstract The enzyme phenylalanine hydroxylase, the substrate phenylalanine, the product of the reaction tyrosine, and the probable in vivo cofactors (6R)- l -erytro-5,6,7,8-tetrahydrobiopterin (H4Bip) and 5,6,7,8-tetrahydropterin (H4Ptr), have been measured during development in Drosophila. The developmental profile of phenylalanine hydroxylase activity shows two peaks. The larger occurs at the time of pupation, coiciding with an important accumulation of tyrosine in the insect. The minor peak appears at the time of adult emergence. The developmental profile of H4Bip shows also two peaks, coinciding with those of maximal phenylalanine hydroxylase activity. However, H4Ptr is only detectable …