Browsing by Author "Tsong, TY"

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Catalytic wheel as Brownian motor and its core engine
(2005-01-01)
Tsong, TY
;
Chang, CH
;
交大名義發表
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National Chiao Tung University
Catalytic wheel, Brownian motor, and biological energy transduction
(2005-02-01)
Tsong, TY
;
Chang, CH
;
物理研究所
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Institute of Physics
An enzyme turns over, or recycles during each catalytic process. It is a catalytic wheel, analogous to a motor, or an engine. The fuel, or the driving force for the wheel, is the free energy of the substrate (S) to product (P) conversion (DeltaG(R)), or a free energy output of a coupled chemical reaction. When DeltaG(R) of the S --> P reaction is negative the reaction is spontaneous and the down-hill wheel motion requires no external input of energy. When DeltaG(R) is positive the wheel must turn uphill against a workload, a reaction that produces energy must be coupled to the wheel. The synthesis of ATP from ADP and P-i in a cell is an uphill reaction and the energy required for the synthesis is derived from the dissipation of a proton gradient, or an electric potential. This article focuses on mechanisms of action of the uphill catalytic wheels. It is shown that the coupling of an external energy source to an uphill catalytic wheel can be done, with nearly 100% efficiency, by mechanisms of the Brownian Motor. Theory of electroconformational coupling (TEC) is used to construct a Brownian motor, and electric activation of an ion pump, Na, K-ATPase is used to demonstrate its basic principles. A TEC Motor has three essential elements: 1) the ability of the protein to interact with an electric field, 2) existence of at least two conformations of protein that oscillate or fluctuate on interaction with the applied field, and 3) a built-in asymmetry in the molecular interactions with substrate and product. It is shown that the TEC Motor is a generic model and applicable to other types of biological energy transducers.
Enzyme as catalytic wheel powered by a Markovian engine: conformational coupling and barrier surfing models
(2005-05-01)
Tsong, TY
;
Chang, CH
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物理研究所
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Institute of Physics
We examine a typical Michaelis-Menten Enzyme (MME) and redress it to form a transducer of free energy, and electric, acoustic, or other types of energy. This amendment and extension is necessary in lieu of recent experiments in which enzymes are shown to perform pump, motor, and locomotion functions resembling their macroscopic counterparts. Classical textbook depicts enzyme, or an MME, as biocatalyst which can enhance the rate of a chemical reaction by lowering the activation barrier but cannot shift the thermodynamic equilibrium of the biochemical reaction. An energy transducer, on the other hand, must also be able to harvest, store, or divert energy and in doing so alter the chemical equilibrium, change the energy form, fuel an energy consuming process, or perform all these functions stepwise in one catalytic turnover. The catalytic wheel presented in this communication is both a catalyst and an energy transducer and can perform all these tasks with ease. A Conformational Coupling Model for the rotary motors and a Barrier Surfing Model for the track-guided stepping motors and transporters, are presented and compared. It is shown that the core engine of the catalytic wheel, or a Brownian motor, is a Markovian engine. It remains to be seen if this core engine is the basic mechanism for a wide variety of bio-molecular energy transducers, as well as certain other dynamic systems, for example, the Parrondo's Games. (c) 2004 Elsevier B.V. All rights reserved.
Rotary motor powered by stochastic uncorrelated dipoles
(2005-11-01)
Chang, CH
;
Tsong, TY
;
物理研究所
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Institute of Physics
It is demonstrated that the stochastic back-and-forth vibrations of uncorrelated dipoles may lead to rotation of their ambient dipoles. This peculiar phenomenon is clarified by considering spatial and temporal symmetry breakings. The former asymmetry is the result of the multiple biased Hamiltonian vector fields, which is a ratchet effect, and the latter, of the time sequence specified by a metastable state. Since this driving mechanism is simpler than that of F(0)F(1)ATPase, it could benefit the design of nanometer scale rotary devices.