70 research outputs found
Electrogenic, proton-coupled, intestinal dipeptide transport in herbivorous and carnivorous teleosts.
No full textElectrogenic, proton-coupled, intestinal dipeptide transport in herbivorous and carnivorous teleosts.
No full textIn both herbivorous tilapia (Oreochromis mossambicus) and carnivorous rockfish (Sebastes caurinus) intestinal and pyloric cecal brush-border membrane vesicles (BBMV), [14C]glycylsarcosine ([14C]Gly-Sar) uptake was stimulated by a transmembrane proton gradient. A transmembrane K(+)-diffusion potential (inside negative) stimulated [14C]Gly-Sar uptake above that observed with short-circuited vesicles, whereas an inwardly directed Na+ gradient in both fishes had no effect on peptide uptake. In tilapia, [14C]Gly-Sar influx occurred by the combination of 1) a high-affinity, saturable, proton gradient-dependent carrier system [Kt [concentration that equals one-half of maximum influx (Jmax)] = 0.56 +/- 0.08 mM; Jmax = 1,945.0 +/- 174.6 pmol.mg protein-1.10 s-1]; 2) a low-affinity, nonsaturable (within 1-10 mM), proton gradient-dependent carrier system (nonsaturable carrier-mediated transport component = 4,514.0 +/- 28.1 pmol.mg protein-1.10 s-1.mM-1); and 3) a diffusional component accounting for < 10% of total influx within the concentration range tested. Influx (10 s) of 1-10 mM [14C]Gly-Sar in tilapia intestine was significantly (P < 0.01) inhibited by 10 mM diethylpyrocarbonate, a specific inhibitor of proton-coupled peptide transport systems. [14C]Gly-Sar influx into tilapia BBMV showed cis-inhibition and trans-stimulation by Gly-Pro, suggesting that [14C]Gly-Sar and Gly-Pro shared the same mucosal peptide transporter in fish. These observations strongly suggest that intestinal transport of peptides in herbivorous and carnivorous fishes is proton gradient dependent, electrogenic, sodium independent, and qualitatively resembles the peptide transport paradigm proposed for mammals
H+/glycyl-L-proline cotransport in brush border membrane vesicles of eel (Anguilla anguilla) intestine
No full textA plasma membrane H+-glycyl-L-proline (Gly-L-Pro) cotransport mechanism has been identified in isolated eel intestinal brush-border membrane vesicles (BBMV) by both measuring radiolabeled Gly-L-Pro uptake and monitoring Gly-L-Pro-dependent H+ influx with the pH-sensitive dye acridine orange. The application of an inside negative membrane potential resulted in increasing Gly-L-Pro uptake, as well as the application of inwardly directed H+ gradient (although only when an inside negative membrane potential was present). Furthermore, vesicular H+ influx was found specifically associated with the presence of Gly-L-Pro in the extravesicular medium. The carrier-mediated nature of H+-Gly-L-Pro cotransport was assessed, and its concentration that yielded one-half maximal Gly-L-Pro influx was similar to 1.30 mM when measured by either radioactive or fluorescent tracers. Different dipeptides strongly inhibited Gly-L-Pro uptake by eel intestinal BBMV, as well as the cephalosporin antibiotic cephalexin, suggesting that dipeptide molecules and cephalosporin antibiotics may share a common transport system in eel intestinal BBMV
Importance of R-CH3⋯O tetrel bonding and vinyl⋯aryl stacking interactions in stabilizing the crystal packing of 2’,4’-dihydroxy-3’-methoxychalcone: Exploration of antileishmanial activity and molecular docking studies
No full textA detailed experimental and theoretical investigation of a chalcone derivative 2’,4’-dihydroxy-3’-methoxychalcone (DHMC) isolated from Argentinean type-Zuccagnia propolis has been performed. The isolated compound was characterized by 1H and 13C Nuclear Magnetic Resonance (NMR), infrared (IR) and Raman spectroscopies and its crystal structure was solved by single-crystal X-ray diffraction (XRD). The molecular geometry of the title compound was investigated theoretically and a very good agreement between experimental and computed geometrical parameters and vibrational frequencies have been observed. The substance crystallized in the orthorhombic Pbcn crystal system, with Z= 8 molecules per unit cell. The molecular geometry of the molecule is mainly stabilized by intramolecular O-H⋯O(keto) hydrogen bonds. The structure reveals that the crystal packing is mainly governed by O-H⋯O and C-H⋯O hydrogen bonds. The supramolecular assembly of the compound in solid state is also stabilized by σ-hole tetrel bonding interactions (O⋯C) involving the O-atom of the hydroxyl and the carbon atom of the methoxy group. Other interactions such as C-H⋯π and vinyl⋯π stacking interactions are also relevant in the stabilization of the solid structure of DHMC. The interaction energies of the different self-assembled dimers have been estimated using DFT calculations and various computational tools including MEP surfaces, QTAIM, NBO and NCI plot analysis. The antileishmanial activity of DHMC indicates that the compound was active against the main specie that cause tegumentary leishmaniosis in Argentina. The computational molecular docking simulation was used to predict the binding potential of the title chalcone derivative against six different leishmanial protein targets
Cell-free DNA Methylation and Transcriptomic Signature Prediction of Pregnancies with Adverse Outcomes
No full textAlthough analysis of maternal plasma cell-free content has been employed for screening of genetic abnormalities within a pregnancy, limited attention has been paid to its use for the detection of adverse pregnancy outcomes (APOs) based on placental function. Here we investigated cell-free DNA and RNA content of 102 maternal and 25 cord plasma samples. Employing a novel deconvolution methodology, we found that during the first trimester, placenta-specific DNA increased prior to the subsequent development of gestational diabetes with no change in patients with preeclampsia while decreasing with maternal obesity. Moreover, using cell-free RNA sequencing, APOs revealed 71 differentially expressed genes early in pregnancy. We noticed the upregulation of S100A8, MS4A3, and MMP8 that have been already associated with APOs but also the upregulation of BCL2L15 and the downregulation of ALPL that have never been associated with APOs. We constructed a classifier with a positive predictive ability (AUC) of 0.91 for APOs, 0.86 for preeclampsia alone and 0.64 for GDM. We conclude that placenta-specific cell-free nucleic acids during early gestation provide the possibility of predicting APOs prior to the emergence of characteristic clinical features
Cell-free DNA Methylation and Transcriptomic Signature Prediction of Pregnancies with Adverse Outcomes
No full textCooperative learning technique for teaching object oriented programming.
No full textM. Ed. University of KwaZulu-Natal, Durban 2013.IT teaching strategies are unable to keep abreast of the ever-changing programming paradigms, programming languages and versions of software suites that are often “technologically hardware dependant” and costly to implement. Faced with ever increasing class sizes, lecture workloads and
diminishing monetary resources coupled with reducing throughput rates in programming courses; IT educators are faced with challenges when teaching programming. The issue here maybe to move away from teacher centred learning to student centred learning. Pair Programming offers educators an
opportunity to further enhance student centred learning.
This study conducted an empirical study of “pair programming” in the teaching and learning of an introductory programming course in computer science with input from educators and learners. The purpose was to determine how a cooperative
learning model can be used as a pedagogic tool for effective teaching and learning in a programming course. The study attempted to determine the impact of collaborative pair programming on students and whether IT educators can use pair programming as a teaching strategy.
There was a pre-test for students to secure data and on how students attempted programming tasks. Thereafter pair-programming was implemented and a post-test was administered to determine the effectiveness of the intervention strategy.
The research findings indicated that the educators and learners had a positive attitude towards the use of pair programming to support teaching and learning
Crystal structure of bis(4-acetylanilinium) tetrachloridomercurate(II)
No full textThe structure of the title salt, (C8H10NO)2[HgCl4], is isotypic with that of the cuprate(II) and cobaltate(II) analogues. The asymmetric unit contains one 4-acetylanilinium cation and one half of a tetrachloridomercurate(II) anion (point group symmetry m). The Hg—Cl distances are in the range 2.4308 (7)–2.5244 (11) Å and the Cl—Hg—Cl angles in the range of 104.66 (2)–122.94 (4)°, indicating a considerable distortion of the tetrahedral anion. In the crystal, cations are linked by an intermolecular N—H...O hydrogen-bonding interaction, leading to a C(8) chain motif with the chains extending parallel to the b axis. There is also a π–π stacking interaction with a centroid-to-centroid distance of 3.735 (2) Å between neighbouring benzene rings along this direction. The anions lie between the chains and interact with the cations through intermolecular N—H...Cl hydrogen bonds, leading to the formation of a three-dimensional network structure
Weak noncovalent interactions in two positional isomers of acrylonitrile derivatives: inputs from PIXEL energy, Hirshfeld surface and QTAIM analyses
No full textA single crystal X-ray diffraction analysis was performed on two positional isomers (m-tolyl and p-tolyl) of acrylonitrile derivatives, namely, (Z)-3-(4-(pyridin-2-yl) phenyl)-2-(m-tolyl) acrylonitrile (1) and (Z)-3-(4-(pyridin-2-yl)phenyl)-2-(p-tolyl) acrylonitrile (2). Compound 1 crystallized in the monoclinic P21/n space group with two crystallographically independent molecules. Compound 2 also possesses two crystallographically independent molecules and crystallized in the triclinic P-1 space group. The Hirshfeld surface analysis revealed that, in both isomers, intermolecular H⋅⋅⋅H/C/N contacts contribute significantly to the crystal packing. More than 40% of the contribution arises from intermolecular C–H⋅⋅⋅C(π) contacts. In both compounds, the relative contribution of these contacts is comparable, indicating that the positional isomeric effects are marginal. The structures in which these isomers are arranged in the solid state are very similar, and the lattice energies are also comparable between the isomers. The Coulomb-London-Pauli-PIXEL (CLP-PIXEL) energy analysis identified the energetically significant dimers. The strength of the intra- and intermolecular interactions was evaluated using the quantum theory of atoms in molecules approach. The UV-Vis absorbance in three different solvents (chloroform, ethanol, and ethyl acetate) for isomers 1 and 2 are very similar. This result is in good agreement with the time-dependent density-functional theory (TD-DFT) calculations
X-ray studies of crystalline complexes involving amino acids and peptides. XLIV. Invariant features of supramolecular association and chiral effects in the complexes of arginine and lysine with tartaric acid
No full textThe tartaric acid complexes with arginine and lysine exhibit two stoichiometries depending upon the ionization state of the anion. The structures reported here are DL-argininium DL-hydrogen tartrate, bis(L-argininium) L-tartrate, bis(DL-lysinium) DL-tartrate monohydrate, L-lysinium D-hydrogen tartrate and L-lysinium L-hydrogen tartrate. During crystallization, L-lysine preferentially interacts with D-tartaric acid to form a complex when DL-tartaric acid is used in the experiment. The anions and the cations aggregate into separate alternating layers in four of the five complexes. In bis(L-argininium) L-tartrate, the amino acid layers are interconnected by individual tartrate ions which do not interact among themselves. The aggregation of argininium ions in the DL- and the L-arginine complexes is remarkably similar, which is in turn similar to those observed in other dicarboxylic acid complexes of arginine. Thus, argininium ions have a tendency to assume similar patterns of aggregation, which are largely unaffected by a change in the chemistry of partner molecules such as the introduction of hydroxyl groups or a change in chirality or stoichiometry. On the contrary, the lysinium ions exhibit fundamentally different aggregation patterns in the DL-DL complexes on the one hand and L-D and L-L complexes on the other. Interestingly, the pattern in the L-D complex is similar to that in the L-L complex. The lysinium ions in the DL-DL complex exhibit an aggregation pattern similar to those observed in the DL-lysine complexes involving other dicarboxylic acids. Thus, the effect of change in the chirality of a subset of the component complexes could be profound or marginal, in an unpredictable manner. The relevant crystal structures appear to indicate that the preference of L-lysine for D-tartaric acid is perhaps caused by chiral discrimination resulting from the amplification of a small energy difference
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