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  • 11
    Electronic Resource
    Electronic Resource
    The global terrestrial carbon cycle (1993)
    Springer
    Water, air & soil pollution 70 (1993), S. 19-37 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract There is great uncertainty with regard to the future role of the terrestrial biosphere in the global carbon cycle. The uncertainty arises from both an inadequate understanding of current pools and fluxes as well as the potential effects of rising atmospheric concentrations of CO2 on natural ecosystems. Despite these limitations, a number of studies have estimated current and future patterns of terrestrial carbon storage. Future estimates focus on the effects of a climate change associated with a doubled atmospheric concentration of CO2. Available models for examining the dynamics of terrestrial carbon storage and the potential role of forest management and landuse practices on carbon conservation and sequestration are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01104986
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  • 12
    Electronic Resource
    Electronic Resource
    Conformational changes in human red cell membrane proteins induced by sugar binding (1991)
    Springer
    The journal of membrane biology 123 (1991), S. 191-207 
    Details
    ISSN: 1432-1424
    Keywords: red cell ; glucose transport protein ; band 3 ; anion exchange protein ; maltose ; disaccharides ; amion transport inhibitors ; DBDS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary We have previously shown that the human red cell glucose transport protein and the anion exchange protein, band 3, are in close enough contact that information can be transmitted from the glucose transport protein to band 3. The present experiments were designed to show whether information could be transferred in the reverse direction, using changes in tryptophan fluorescence to report on the conformation of the glucose transport protein. To see whether tryptophan fluorescence changes could be attributed to the glucose transport protein, we based our experiments on procedures used by Helgerson and Carruthers [Helgerson, A.L., Carruthers, A., (1987)J. Biol. Chem. 262:5464–5475] to displace cytochalasin B (CB), the specificd-glucose transport inhibitor, from its binding site on the inside face of the glucose transport protein, and we showed that these procedures modified tryptophan fluorescence. Addition of 75mm maltose, a nontransportable disaccharide which also displaces CB, caused a timedependent biphasic enhancement of tryptophan fluorescence in fresh red cells, which was modulated by the specific anion exchange inhibitor, DBDS (4,4′-dibenzamido-2,2′-stilbene disulfonate). In a study of nine additional disaccharides, we found that both biphasic kinetics and DBDS effects depended upon specific disaccharide conformation, indicating that these two effects could be attributed to a site sensitive to sugar conformation. Long term (800 sec) experiments revealed that maltose binding (±DBDS) caused a sustained damped anharmonic oscillation extending over the entire 800 sec observation period. Mathematical analysis of the temperature dependence of these oscillations showed that 2 μm DBDS increased the damping term activation energy, 9.5±2.8 kcal mol−1 deg−1, by a factor of four to 39.7±5.1 kcal mol−1 deg−1, providing strong support for the view that signalling between the glucose transport protein and band 3 goes in both directions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870403
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  • 13
    Electronic Resource
    Electronic Resource
    Initial steps of αand β-d-glucose binding to intact red cell membrane (1993)
    Springer
    The journal of membrane biology 132 (1993), S. 167-178 
    Details
    ISSN: 1432-1424
    Keywords: red cell ; glucose transport protein ; GLUT1 ; kinetics ; rapid reactions ; tryptophan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The kinetics of the initial phases of d-glucose binding to the glucose transport protein (GLUT1) of the human red cell can be followed by stopped-flow measurements of the time course of tryptophan (trp) fluorescence enhancement. A number of control experiments have shown that the trp fluorescence kinetics are the result of conformational changes in GLUT1. One shows that nontransportable l-glucose has no kinetic response, in contrast to d-glucose kinetics. Other controls show that d-glucose binding is inhibited by cytochalasin B and by extracellular d-maltose. A typical time course for a transportable sugar, such as d-glucose, consists of a zero-time displacement, too fast for us to measure, followed by three rapid reactions whose exponential time courses have rate constants of0.5–100 sec+−1 at 20°C. It is suggested that the zero-time displacement represents the initial bimolecular ligand/GLUT1 association. Exponential 1 appears to be located at, or near, the external membrane face where it is involved in discriminating among the sugars. Exponential 3 is apparently controlled by events at the cytosolic face. Trp kinetics distinguish the K d of the epimer, d-galactose, from the K dfor d-glucose, with results in agreement with determinations by other methods. Trp kinetics distinguish between the binding of the α- and β-d-glucose anomers. The exponential 1 activation energy of the β-anomer, 13.6 ± 1.4 kcal mol+−1, is less than that of α-d-glucose, 18.4 ± 0.8 kcal mol+−1, and the two Arrhenius lines cross at ≈23.5°C. The temperature dependence of the kinetic response following α-d-glucose binding illustrates the interplay among the exponentials and the increasing dominance of exponential 2 as the temperature increases from 22.3 to 36.6°C. The existence of these interrelations means that previously acceptable approximations in simplified reaction schemes for sugar transport will now have to be justified on a point-to-point basis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239006
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  • 14
    Electronic Resource
    Electronic Resource
    Interaction between red cell membrane band 3 and cytosolic carbonic anhydrase (1993)
    Springer
    The journal of membrane biology 134 (1993), S. 169-179 
    Details
    ISSN: 1432-1424
    Keywords: Red cell ; Carbonic anhydrase ; Band 3 ; Anion exchange protein ; Dansylsulfonamide ; Anion transport inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We have previously proposed that a membrane transport complex, centered on the human red cell anion transport protein, band 3, links the transport of anions, cations and glucose. Since band 3 is specialized for HCO 3 − /Cl− exchange, we thought there might also be a linkage with carbonic anhydrase (CA) which hydrates CO2 to HCO 3 − . CA is a cytosolic enzyme which is not present in the red cell membrane. The rate of reaction of CA with the fluorescent inhibitor, dansylsulfonamide (DNSA) can be measured by stopped-flow spectrofluorimetry and used to characterize the normal CA configuration. If a perturbation applied to a membrane protein alters DNSA/CA binding kinetics, we conclude that the perturbation has changed the CA configuration by either direct or allosteric means. Our experiments show that covalent reaction of the specific stilbene anion exchange inhibitor, DIDS, with the red cell membrane, significantly alters DNSA/CA binding kinetics. Another specific anion exchange inhibitor, benzene sulfonate (BSate), which has been shown to bind to the DIDS site causes a larger change in DNSA/CA binding kinetics; DIDS reverses the BSate effect. These experiments show that there is a linkage between band 3 and CA, consistent with CA interaction with the cytosolic pole of band 3. This work was supported in part by a grant-in-aid from the American Heart Association, by the Squibb Institute for Medical Research and by The Council for Tobacco Research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234498
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  • 15
    Electronic Resource
    Electronic Resource
    Numerical solution for the dilation of a fluid-saturated porous elastic sphere due to a point source of fluid at the centre of the sphere (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 17 (1993), S. 699-714 
    Details
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Mathematical modelling of the ascent of free fluid through relatively strong rock, deep in the Earth's mantle, presents a challenge in geomechanics. Here the medium is considered as fluid-saturated, porous, elastic and bounded, and the fluid enters at a point source. An explicit finite difference method is developed for the numerical solution to the problem of the dilatation of a fluid-saturated porous elastic sphere due to a point fluid source of constant strength at the centre of the sphere. A cubic spline interpolant is used to evaluate a definite integral which occurs in the boundary condition for the pore fluid pressure at the surface of the sphere. The numerical solutions for the dilatation and pore fluid pressure are compared with analytical solutions and the absolute and relative errors of the numerical solutions are calculated. When the fluid source is switched on, the pore fluid pressure starts to decrease, reaches a minimum value and then steadily increases. The initial time rate of decrease of the pore fluid pressure is independent of the radial distance from the source. It decreases as the radius of the sphere increases and vanishes for a point fluid source in an infinite porous elastic medium.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nag.1610171003
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