Diffusional Effects
Mostrando 13-24 de 24 artigos, teses e dissertações.
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13. Cellular constraints to diffusion: The effect of antidiuretic hormone on water flows in isolated mammalian collecting tubules
These experiments were intended to evaluate the effects of antidiuretic hormone (ADH) on dissipative water transport in cortical collecting tubules isolated from rabbit kidney. In the absence of ADH, the osmotic (Pf, cm sec-1) and diffusional (PDW cm sec-1) water permeability coefficients were, respectively, 6±6 and 4.7±1.3 (SD). When ADH was added to the
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14. Plasmid stability in immobilized and free recombinant Escherichia coli JM105(pKK223-200): importance of oxygen diffusion, growth rate, and plasmid copy number.
Stability of the plasmid pKK223-200 in Escherichia coli JM105 was studied for both free and immobilized cells during continuous culture. The relationship between plasmid copy number, xylanase activity, which was coded for by the plasmid, and growth rate and culture conditions involved complex interactions which determined the plasmid stability. Generally, th
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15. DNA axial rotation and the merge of oppositely supercoiled DNA domains in Escherichia coli: Effects of DNA bends
We have examined the issue whether axial rotation of an intracellular DNA segment several thousand base pairs in length is associated with a large friction barrier against the merge of oppositely supercoiled DNA domains. The induction of a site-specific recombinase was used to form intracellular DNA rings bearing different numbers of transcription units, and
National Academy of Sciences.
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16. Influence of nuclear spin on chemical reactions: Magnetic isotope and magnetic field effects (A Review)
The course of chemical reactions involving radical pairs may depend on occurrence and orientation of nuclear spins in the pairs. The influence of nuclear spins is maximized when the radical pairs are confined to a space that serves as a cage that allows a certain degree of independent diffusional and rotational motion of the partners of the pair but that als
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17. Local translational diffusion rates of membranous Na+,K(+)-ATPase measured by saturation transfer ESR spectroscopy.
Diffusion-controlled Heisenberg spin exchange between spin-labeled Na+,K(+)-ATPase [ATP phosphohydrolase (Na+/K(+)-transporting), EC 3.6.1.37] proteins has been studied by saturation transfer ESR spectroscopy in reconstituted membranes. Na+,K(+)-ATPase from the salt gland of Squalus acanthias was solubilized in a polyoxyethylene ether detergent, octa(ethylen
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18. Administration of atrial natriuretic factor inhibits sodium-coupled transport in proximal tubules.
The newly discovered peptides extracted from cardiac atria, atrial natriuretic factors (ANFs), when administered parenterally cause renal hemodynamic changes and natriuresis. The nephron sites and cellular mechanism accounting for profound increase in Na+ excretion in response to ANFs are not yet clarified. In the present study we investigated whether synthe
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19. Characterization of Water Channels in Wheat Root Membrane Vesicles.
The functional significance of water channels in wheat (Triticum aestivum L.) root membranes was assessed using light scattering to measure vesicle shrinking in response to osmotic gradients rapidly imposed in a stopped flow apparatus. Vesicles were obtained from both a plasma membrane fraction and a plasma membrane-depleted endomembrane fraction including t
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20. Trehalose-Mediated Inhibition of the Plasma Membrane H+-ATPase from Kluyveromyces lactis: Dependence on Viscosity and Temperature
The effect of increasing trehalose concentrations on the kinetics of the plasma membrane H+-ATPase from Kluyveromyces lactis was studied at different temperatures. At 20°C, increasing concentrations of trehalose (0.2 to 0.8 M) decreased Vmax and increased S0.5 (substrate concentration when initial velocity equals 0.5 Vmax), mainly at high trehalose concentr
American Society for Microbiology.
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21. Enzymatic Activity versus Structural Dynamics: The Case of Acetylcholinesterase Tetramer
The function of many proteins, such as enzymes, is modulated by structural fluctuations. This is especially the case in gated diffusion-controlled reactions (where the rates of the initial diffusional encounter and of structural fluctuations determine the overall rate of the reaction) and in oligomeric proteins (where function often requires a coordinated mo
The Biophysical Society.
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22. Anion transport processes in the mammalian superficial proximal straight tubule.
The experiments reported in this paper were designed to evaluate some of the characteristics of anion transport processes during fluid absorption from superficial proximal straight tubules isolated from rabbit kidney. We measured net chemical C1- flux during fluid absorption from tubules perfused and bathed with Krebs-Ringer buffers containing 113.6 mM C1-,
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23. Hydrodynamic effects and receptor interactions of platelets and their aggregates in linear shear flow.
We have modeled platelet aggregation in a linear shear flow by accounting for two body collision hydrodynamics, platelet activation and receptor biology. Considering platelets and their aggregates as unequal-sized spheres with DLVO interactions (psi(platelet) = -15 mV, Hamaker constant = 10(-19) J), detailed hydrodynamics provided the flow field around the c
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24. Kinetics of H+ ion binding by the P+QA-state of bacterial photosynthetic reaction centers: rate limitation within the protein.
The kinetics of flash-induced H+ ion binding by isolated reaction centers (RCs) of Rhodobacter sphaeroides, strain R-26, were measured, using pH indicators and conductimetry, in the presence of terbutryn to block electron transfer between the primary and secondary quinones (QA and QB), and in the absence of exogenous electron donors to the oxidized primary d