Search results for "stereo"
showing 10 items of 6147 documents
Acceptor Specificity of Amylosucrase from Deinococcus radiopugnans and Its Application for Synthesis of Rutin Derivatives
2016
The transglycosylation activity of amylosucrase (ASase) has received significant attention owing to its use of an inexpensive donor, sucrose, and broad acceptor specificity, including glycone and aglycone compounds. The transglycosylation reaction of recombinant ASase from Deinococcus radiopugnans (DRpAS) was investigated using various phenolic compounds, and quercetin-3-O-rutinoside (rutin) was found to be the most suitable acceptor molecule used by DRpAS. Two amino acid residues in DRpAS variants (DRpAS Q299K and DRpAS Q299R), assumed to be involved in acceptor binding, were constructed by site-directed mutagenesis. Intriguingly, DRpAS Q299K and DRpAS Q299R produced 10-fold and 4-fold hig…
Phosphinotripeptidic Inhibitors of Leucylaminopeptidases
2021
Phosphinate pseudopeptide are analogs of peptides containing phosphinate moiety in a place of the amide bond. Due to this, the organophosphorus fragment resembles the tetrahedral transition state of the amide bond hydrolysis. Additionally, it is also capable of coordinating metal ions, for example, zinc or magnesium ions. These two properties of phosphinate pseudopeptides make them an ideal candidate for metal-related protease inhibitors. This research investigates the influence of additional residue in the P2 position on the inhibitory properties of phosphinopeptides. The synthetic strategy is proposed, based on retrosynthetic analysis. The N-C-P bond formation in the desired compounds is …
Cranial suture biomechanics inMetoposaurus krasiejowensis(Temnospondyli, Stereospondyli) from the upper Triassic of Poland
2019
Cranial sutures connect adjacent bones of the skull and play an important role in the absorption of stresses that may occur during different activities. The Late Triassic temnospondyl amphibian Metoposaurus krasiejowensis has been extensively studied over the years in terms of skull biomechanics, but without a detailed description of the function of cranial sutures. In the present study, 34 thin sections of cranial sutures were examined in order to determine their histovariability and interpret their biomechanical role in the skull. The histological model was compared with three-dimensional-finite element analysis (FEA) simulations of the skull under bilateral and lateral biting as well as …
A secondary mode of action of the herbicide lenacil: Modification of K+ permeability of Acer pseudoplatanus cells
1984
Abstract The action of lenacil on plasmalemma permeability to K+, transmembrane electric potential difference (PD) calculated from the tetraphenylphosphonium distribution, proton extrusion and intracellular pH of Acer pseudoplatanus cells calculated from the 5,5-dimethyloxazolidine,4-dione distribution, was studied and compared with the action of fusicoccin (FC) and diethylstilbestrol (DES). The three compounds temporarily stimulated the rate of 86Rb+ uptake with a half-maximum effect at 5.0 μM for 3-cyclohexyl-6, 7-dihdro-1H-cyclopentapyrimidine-2,4(3H,5H)-dione (lenacil). Lenacil and FC had no action on transmembrane electric potential difference, whereas DES decreased it. Lenacil inhibit…
Acetogenins from Annonaceae family. Their potential biological applications
2019
The aim of this contribution has been to continue with the knowledge about newly isolated acetogenins from Annonaceae family for the last fifteen years. This review will report classification, extraction, isolation, elucidation of the structure, biological activities and mechanism of action of such interesting natural products. In fact, out of the 532 compounds reviewed, 115 previously non-described annonaceous acetogenins have been added to the list of isolated compounds from 2005 to May 2019.
Effect of the cytochrome P-450 inactivator 1-aminobenzotriazole on the metabolism of chlortoluron and isoproturon in wheat
1987
Abstract Roots of young wheat plants ( Triticum aestivum cv Clement) were treated with [ 14 C]chlortoluron or [ 14 C]isoproturon alone or mixed with 1-aminobenzotriazole (ABT), a mechanism-based inactivator of cytochrome P -450 monooxygenases. Radioactivity extracted from shoots slightly decreased during periods of metabolism, this decrease being reduced by ABT in the case of isoproturon. ABT strongly inhibited the metabolism of both herbicides. Accumulation of metabolites was generally depressed in the presence of ABT; however, levels of the free N -monodemethylated derivatives were little or not affected. It is concluded that ABT is a synergist of chlortoluron and isoproturon in wheat bec…
Isolation and identification of 4,6,8-trimethyl-7,9-undecadien-5-ol, a female-specific compound, in tergal gland secretion ofCryptocercus punctulatus…
1991
International audience; The secretion of the tergal glands of Cryptocercus punctulatus consists of a complex mixture of 27 compounds. Of this mixture, only one compound (compound B) is specific for females. By dissecting 200 tergal glands, 50 µg of pure compound B was collected by preparative GC; it was identified as (Z, E-4,6,8-trimethyl-7,9-undecadien-5-oI. Its functions as well as its absolute configuration still have to be determined.
Artemisia arborescens essential oil composition, enantiomeric distribution and antimicrobial activity from different wild populations from the Medite…
2016
International audience; Aerial parts of Artemisiaarborescens were collected from different sites of the Mediterranean area (southwestern Algeria and southern Italy) and the chemical composition of their essential oil (EO) extracted by hydrodistillation was studied by both gas chromatography (GC) equipped with an enantioselective capillary column and GC/mass spectrometry (GC/MS). The EOs obtained were tested against several Listeriamonocytogenes strains. Using GC and GC/MS, 41 compounds were identified, accounting for 96.0-98.8% of the total EO. All EOs showed a similar terpene profile, which was rich in chamazulene, -thujone, and camphor. However, the concentration of such compounds varied …
Kinetic studies on protoporphyrinogen oxidase inhibition by diphenyl ether herbicides
1991
Diphenyl ethers (DPEs) and related herbicides are powerful inhibitors of protoporphyrinogen oxidase, an enzyme involved in the biosynthesis of haems and chlorophylls. The inhibition kinetics of protoporphyrinogen oxidase of various origins by four DPEs, (methyl)-5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid (acifluorfen and its methyl ester, acifluorfen-methyl), methyl-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-chlorobenzoate (LS 820340) and methyl-5-[2-chloro-5-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid (RH 5348), were studied. The inhibitions of the enzymes from maize (Zea mays) mitochondrial and etiochloroplastic membranes and mouse liver mitochondrial membranes were com…
Characterization of (3H) acifluorfen binding to purified pea etioplasts, and evidence that protoporphyrinogen oxidase specifically binds acifluorfen
1992
It is now generally accepted that protoporphyrinogen oxidase is the target-enzyme for diphenylether-type herbicides. Recent studies [Camadro, J-M., Matringe, M., Scalla, R. & Labbe, P. (1991) Biochem. J. 277, 17–21] have revealed that in maize, diphenyl ethers competitively inhibit protoporphyrinogen oxidase with respect to its substrate, protoporphyrinogen IX. In this study, we show that, in purified pea etioplast, [3H]acifluorfen specifically binds to a single class of high-affinity binding sites with an apparent dissociation constant of 6.2 ± 1.3 nM and a maximum density of 29 ± 5 nmol/g protein. [3H]Acifluorfen binding reaches equilibrium in about 1 min at 30°C. Half dissociation occurs…