1,583 research outputs found
Double-inhibitor and uncoupler-inhibitor titrations. 2. Analysis with a nonlinear model of chemiosmotic energy coupling.
No full textThe results of double-inhibitor and uncoupler-inhibitor titrations have been simulated and analyzed with a nonlinear model of delocalized protonic coupling obtained by linking two proton pump models of the kind studied by Pietrobon and Caplan [Pietrobon, D., & Caplan, S. R. (1985) Biochemistry 24, 5764-5776] through their common intermediate delta mu H. It is shown that the results predicted by a delocalized chemiosmotic model are highly dependent on the kind of relationships existing between rate of ATP synthesis, Jp, and delta mu H and rate of electron transfer, Je, and delta mu H. With nonlinear flow-force relationships all the results reported so far are not necessarily inconsistent with the delocalized chemiosmotic model provided that the relationships between rates and delta mu H satisfy the following requirements: Jp/delta mu H increases and/or Je/delta mu H decreases as (delta mu H) increases
S.R. Lewis letter to Z. Eastman, March 5, 1874
No full textBrief letter from S.R. Lewis to Z. Eastman, marking the announcement of an abolitionists' reunion to be held in Chicago in June of 1875. Lewis requests that Eastman, given his close acquaintance with Benjamin Lundy, prepare a public statement of remembrance on Lundy and his contributions to the anti-slavery movement. Benjamin Lundy (1789-1839) was a prominent Quaker abolitionist best known for his development of abolitionist periodicals. His Genius of Universal Emancipation was first published in 1821 from his home in Mt. Pleasant, Ohio, and enjoyed a wide circulation across the antebellum United States. In the 1820s, the young William Lloyd Garrison came to work for The Genius. Benjamin Lundy traveled widely seeking subscriptions to The Genius, giving talks about the anti-slavery movement, and observing and documenting the conditions of enslaved people across the Americas. He was also involved in the establishment of freed slave colonies in Mexico
Double-inhibitor and uncoupler-inhibitor titrations. 1. Analysis with a linear model of chemiosmotic energy coupling.
No full textThe results of double-inhibitor and uncoupler-inhibitor titrations have been simulated and analyzed with a linear model of delocalized protonic coupling using linear nonequilibrium thermodynamics. A detailed analysis of the changes of the intermediate delta muH induced by different combinations of inhibitors of the proton pumps has been performed. It is shown that with linear flow-force relationships the published experimental results of uncoupler-inhibitor titrations are not necessarily inconsistent with, and those of double-inhibitor titrations are inconsistent with, a delocalized chemiosmotic model of energy coupling in the presence of a negligible leak. Also shown and discussed are how the results are affected by a nonnegligible leak and to what extent the shape of the titration curves can be used to discriminate between localized and delocalized mechanisms of energy coupling
Use of nonequilibrium thermodynamics in the analysis of transport: general flow-force relationships and the linear domain.
No full textFlow-force relationships for a six-state proton pump model: intrinsic uncoupling, kinetic equivalence of input and output forces, and domain of approximate linearity.
No full textGeneral flow-force relations have been determined, by the Hill diagram method, for a six-state proton pump model with and without intrinsic uncoupling (molecular slipping). A computer-aided analysis of the resulting sigmoidal flow-force curves has been performed by using a set of physically meaningful rate constants. It is shown that gating effects and apparent irreversibility can arise from sigmoidicity. The regions of approximate linearity in the vicinity of inflection points, which may be far from equilibrium, have been examined with a view to characterization in terms of linear phenomenological equations, with due regard to the problems of kinetic equivalence of the forces and symmetry. The determination of thermodynamic parameters such as the degree of coupling, the phenomenological stoichiometry, and the efficiency in these regions is discussed, and their meaning is analyzed in relation to the parameters characterizing the Onsager domain close to equilibrium. The application of the phenomenological equations of near-equilibrium nonequilibrium thermodynamics to such regions is at best a simplification to be treated with great caution. A knowledge of the distance from equilibrium of the flow-controlling ranges of the forces (i.e., the ranges of approximate linearity) turns out to be crucial for the interpretation of thermodynamic parameters determined by manipulating one of the forces while the other remains constant, as well as for the interpretation of measurements of force ratios at static head. The latter approaches can give good estimates of the magnitude of the mechanistic stoichiometry and of the constant force if the pumps are highly coupled and are operating not far from equilibrium. The force-flow relationships are shown to be modified by intrinsic uncoupling, reflecting the regulatory influence of the forces on the extent and nature of the slip. Thus reaction slip increases, for example, as the force against which the proton pump operates increases. The possible physiological significance of regulated intrinsic uncoupling is discussed
Modelling and optimization of a permanent-magnet machine in a flywheel
No full textThis thesis describes the derivation of an analytical model for the design and optimization of a permanent-magnet machine for use in an energy storage flywheel. A prototype of this flywheel is to be used as the peak-power unit in a hybrid electric city bus. The thesis starts by showing the feasibility of using a flywheel energy storage system for this application, as opposed to other energy storage technologies. It then continues by describing a prototype flywheel system and the required electrical machine: a radial-flux external-rotor permanent-magnet synchronous machine without slots in the stator iron and with a shielding cylinder. An analytical model for the machine is derived, based on 2D electromagnetic field calculations, including the reaction field of the eddy currents in the shielding cylinder. Torque and losses are calculated by means of the Theorem of Poynting and the Lorentz force. Such a machine was built and the analytical model has been validated by experimental measurements. Lastly, the thesis suggests and implements a machine optimization algorithm.Information Technology and System
Further comments on the logic of the application of uncoupler- inhibitor titrations for the elucidation of the mechanisms of energy coupling.
No full textFollowing the appearance of two papers in this journal commenting on the logic of the application of uncoupler-inhibitor titrations as a means of discriminating between 'delocalized' and 'localized' chemiosmotic mechanisms [(1984) FEBS Lett. 176,79-82; (1985) FEBS Lett. 186, 8-10], and in contrast with the arguments presented there and elsewhere, we show that in a linear model the increase in delta mu H which accompanies partial inhibition of the ATPases always leads to a relatively higher decrease of the rate of ATP synthesis by a given concentration of uncoupler in the presence of an ATPase inhibitor than in its absence. This is due to the fact that the same titre of uncoupler leads to a higher dissipative H+ flow in the presence of inhibitor, since the driving force delta mu H is higher
Design metrics for evaluating the propulsive efficiency of future ships
No full textThere is an increasing need for the ship design process to take account of environmental issues such as the emission of greenhouse gases and the likely extension of a carbon dioxide charging mechanism to international shipping. These issues, together with the need for economic viability, provide further incentives to improve the efficiency of propulsion of ships. The main components of powering are firstly reviewed. Individual components and other power saving devices are identified which should contribute to improvements in the overall efficiency of propulsion. Suitable design metrics and procedures, taking into account economic and environmental factors, are recommended for the design of future ships
Description of S.R. Krom's system and machinery for dry crushing and concentrating ores.
No full textCover title.Mode of access: Internet.MAIN; TN500.K7 1876: Introduction signed by author, S.R. Krom
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