Search results for "Biophysic"
showing 10 items of 3565 documents
SAXS Study on Myoglobin Embedded in Amorphous Saccharide Matrices
2011
We report on Small Angle X-ray Scattering (SAXS) measurements performed on samples of carboxy-myoglobin and met-myoglobin embedded in low hydrated matrices of four different saccharides (trehalose, sucrose, maltose and lactose). Results confirm the already reported occurrence of inhomogeneities, which are not peculiar of trehalose samples, but appear also in maltose and lactose, and in some cases also sucrose, being dependent on the sample hydration and on the presence of sodium dithionite. This behaviour confirms our previous interpretation about the nature of the inhomogeneities, and prompt it as a possible general behaviour for highly concentrated sugar matrices.
Is ABA involved in tolerance responses to salinity by affecting cytoplasm ion homeostasis in rice cell lines?
2012
Abstract The ability of plant cells to maintain cytoplasm ion homeostasis under saline stress is among the main mechanisms involved in salt tolerance. To cope with excess Na + , cells extrude it from the cytoplasm, which requires expenditure of metabolic energy, provided by H + gradients generated by membrane-bound H + -pumps. ABA is well-known to be involved in physiological processes elicited or enhanced by stresses causing cell dehydration. In this work we studied the possible implication of this plant hormone in the control of salt-induced cellular mechanisms conducting to Na + extrusion from the cytoplasm. We used rice ( Oryza sativa L.) cell lines selected for their different toleranc…
Flow cytometric kinetic assay of the activity of Na+/H+ antiporter in mammalian cells.
2004
Background The Na+/H+ exchanger (NHE) of mammalian cells is an integral membrane protein that extrudes H+ ion in exchange for extracellular Na+ and plays a crucial role in the regulation of intracellular pH (pHi). Thus, when pHi is lowered, NHE extrudes protons at a rate depending of pHi that can be expressed as pH units/s. Methods To abolish the activity of other cellular pH-restoring systems, cells were incubated in bicarbonate-free Dulbecco's modified Eagle's medium buffered with HEPES. Flow cytometry was used to determine pHi with 2′,7′-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein acetoxymethyl ester or 5-(and-6)-carboxy SNARF-1 acetoxymethyl ester acetate, and the appropriate fluo…
Kinetic Properties of Cl−Uptake Mediated by Na+-Dependent K+-2Cl−Cotransport in Immature Rat Neocortical Neurons
2007
GABA, the main inhibitory neurotransmitter in the adult nervous system, evokes depolarizing membrane responses in immature neurons, which are crucial for the generation of early network activity. Although it is well accepted that depolarizing GABA actions are caused by an elevated intracellular Cl−concentration ([Cl−]i), the mechanisms of Cl−accumulation in immature neurons are still a matter of debate. Using patch-clamp, microfluorimetric, immunohistochemical, and molecular biological approaches, we studied the mechanism of Cl−uptake in Cajal-Retzius (CR) cells of immature [postnatal day 0 (P0) to P3] rat neocortex. Gramicidin-perforated patch-clamp and 6-methoxy-N-ethylquinolinium-microfl…
Host–guest complexes of conformationally flexible C-hexyl-2-bromoresorcinarene and aromatic N-oxides: solid-state, solution and computational studies
2018
Host–guest complexes of C-hexyl-2-bromoresorcinarene (BrC6) with twelve potential aromatic N-oxide guests were studied using single crystal X-ray diffraction analysis and 1H NMR spectroscopy. In the solid state, of the nine obtained X-ray crystal structures, eight were consistent with the formation of BrC6-N-oxide endo complexes. The lone exception was from the association between 4-phenylpyridine N-oxide and BrC6, in that case the host forms a self-inclusion complex. BrC6, as opposed to more rigid previously studied C-ethyl-2-bromoresorcinarene and C-propyl-2-bromoresorcinarene, undergoes remarkable cavity conformational changes to host different N-oxide guests through C–H···π(host) intera…
Bis(pyridylvinyl)diaminobenzenes: synthesis, acidochromism and solvatochromism of the fluorescence
2005
Abstract C2-symmetrical 1,4-distyrylbenzenes with 4-dimethylaminobenzene or pyridine as terminal rings, and propyloxy or dipropylamino groups in the central 2,5-positions were prepared. Solvatochromism of the absorption is small, but more pronounced in the fluorescence spectra. Some compounds exhibit huge Stokes shifts. Acid strongly alters the fluorescence: red shifts and decreasing quantum yields is the general result, but depending on the position and character of the basic sites, a strong recovery of fluorescence efficiency combined with large hypsochromic shifts may result in highly acidic solutions.
Current trends in solid-phase-based extraction techniques for the determination of pesticides in food and environment
2006
Solid-phase extraction (SPE) procedures for pesticide residues in food and environment are reviewed and discussed. The use of these procedures, which include several approaches such as: matrix solid-phase dispersion (MSPD), solid-phase micro-extraction (SPME) and stir-bar sorptive extraction (SBSE), represents an opportunity to reduce analysis time, solvent consumption, and overall cost. SPE techniques differ from solvent extraction depending on the interactions between a sorbent and the pesticide. This interaction may be specific for a particular pesticide, as in the interaction with an immunosorbent, or non-specific, as in the way a number of different pesticides are adsorbed on apolar or…
Cloning and characterization of the promoter of Hugl-2, the human homologue of Drosophila lethal giant larvae (lgl) polarity gene.
2007
The human lgl gene, Hugl-2 (llgl2, Lgl2), codes for a cytoskeletal protein involved in regulating cell polarity. Here, we report the identification and functional characterization of the promoter region ( approximately 1.2kb) of the Hugl-2 gene. Luciferase expression assays show a high basal Hugl-2 promoter activity in different cell lines and primary human hepatocytes. Truncations of the promoter identified a GC-rich region important for this activity. Alignment of human and mouse genomic sequences demonstrate that this is an evolutionary conserved region fcontaining putative binding sites for several transcription factors including Elk-1 and Sp-1. Mithramycin A reduces Hugl-2 expression i…
Interaction of UO2(2+) with ATP in aqueous ionic media.
2005
Interaction of dioxouranium(VI) (uranyl) ion with ATP was studied by ligand/proton and metal/hydroxide displacement technique, at very low ionic strength and at I=0.15 mol L(-1), in aqueous Me4NCl and NaCl solutions, at t=25 degrees C. Measurements were carried out in the pH range 3-8.5, before the formation of precipitate. Computer analysis allowed us to find the quite stable species UO2(ATP)H2(0), UO2(ATP)H-, UO2(ATP)2-, UO2(ATP)2(6-), UO2(ATP)2H2(4-) and UO2(ATP)(OH)3- whose formation constants are (at I=0 mol L(-1)) logbeta(112)=18.21, logbeta(111)=14.70, logbeta(110)=9.14, logbeta(120)=12.84, logbeta(122)=24.82, and logbeta(11-1)=2.09, respectively. Different values were obtained in th…
Polynucleotide differentiation using hybrid solid-state nanopore functionalizing with α-hemolysin
2019
We report results from full atomistic molecular dynamics simulations on the properties of biomimetic nanopores. This latter result was obtained through the direct insertion of an α-hemolysin protein inside a hydrophobic solid-state nanopore. Upon translocation of different DNA strands, we demonstrate here that the theoretical system presents the same discrimination properties as the experimental one obtained previously. This opens an interesting way to promote the stability of a specific protein inside a solid nanopore to develop further biomimetic applications for DNA or protein sequencing.