Charged Pair Current Networks in Bioenergetics

A model of mitochondrial energy coupling has been proposed based on the principles of paired charge separation and vectorial paired charge flow. The unique role of the electron transfer chain and ionophores in mediating charge separation is emphasized.The present model evolved in three stages. The study of configurational transitions in isolated mitochondria led to the concept of a conformationally strained energized state (1) generated by an exergonic center and discharged by an endergonic center (the conformational model). The study of energized proton ejection in turn led to the concept of the energized state as a charge-separated state (2, 3) with the protein acting as an electromechanochemical transducer (the electromechanochemical model). Finally, the study of respiratory control in liposomal vesicles of cytochrome oxidase (4) led to the recognition of the primary role of moving charges in energy coupling. From the conformational model, the principle of direct coupling between exergonic and endergonic centers was deduced. From the electromechanochemical model was derived the principle that energy coupling requires the charge-separated state in both exergonic and endergonic centers. Thus, the two earlier models prepared the ground for the development of the moving charge model (5, 6). THE PAIR MOVING CHARGE MODELExergonic and Endergonic Centers. Coupling invariably involves two reaction centers vectorially aligned with respect to the membrane (see Fig. 1)-one in which an exergonic reaction (the driving reaction) takes place and the other in which endergonic reaction (the driven reaction) takes place. The two centers are separated by a linkage system to be defined later which facilitates the coupling of the two respective chemical reactions. We are assuming complete separation in space of the exergonic and endergonic centers and no mixing of any of the reactants or products.The exergonic and endergonic reactions proceed in a vectorial fashion (see Fig. 2) so that the initial reactants are on one side of the membrane and the final products are on the other side of the membrane (7)(8)(9).The Essentiality of the Charge-Separated State for Energy Coupling. Chemical energy may be defined as the energy intrinsic to the system of paired electrons and protons in atoms and molecules. The utilization of chemical energy requires, as a first preliminary, the tearing out of charges beyond orbital constraints. We are thus postulating that the charge-separated state of the reactants in a chemical reaction is a prerequisite for energy coupling.Consider the energy of an electron and a proton in a H atom (the valency state) and the energy of the separated electron and proton at a critical distance at which orbital interactions no longer apply. We are assuming that this separation is achieved by the appropriate conditions (paired charge separation) and with the necessary catalysts, e.g., an electron transfer chain or an ionophore, to satisfy the requirements for reversibility. According to Kemeny (10), the valency stat...

Section: The Pair Moving Charge Modelmentioning

confidence: 99%

“…The separated charges may be considered to be in the ground state of a potential well, i.e., at minimal energy (10). Thus, the problem of thermalization inherent in excited states is nonexistent.…”

Section: The Pair Moving Charge Modelmentioning

confidence: 99%

Paired Moving Charges in Mitochondrial Energy Coupling

Green

Reible²

1974

“…The weight which is now up can be transferred to a neighboring pulley, move down and pull up another weight. This corresponds to a cation in the coupling system, transferring free energy from the electron to phosphate in antiport coupling (19,20).…”

Section: Conservative Mechanismsmentioning

confidence: 99%

Energy Transfer Mechanisms in Mitochondria

Kemény

1974

Self Cite

The problem of free energy transfer and transduction in mitochondria is reviewed from the point of view of conservative and dissipative mechanisms. Excited states are inherently dissipative and are not considered viable possibilities. If the free energy is already a local minimum and present in the form of potential energy, conservative transfer is possible within a properly designed medium. The design features are compatible with what is known about mitochondria. Conservation of free energyThe function of bioenergetic machines, as of all machines, is the transduction of free energy. The purpose of this paper is to assess some of the mechanisms suggested for energy transduction in mitochondria. One may generally classify these mechanisms as conservative or dissipative. The dissipative mechanisms are those that either do not have design features that would allow conservation of free energy or, if they do, it is unreasonable to assume that the mitochondrion should possess these features. Conservative mechanisms are those that do possess features of design capable to conserve free energy and it is reasonable to assume, on the basis of what is known about mitochondria, that these features may be operative.The transport of free energy in a system simply means that upon arrival at some destination, some work can be performed on another system at the cost of lowering the free energy of the first system. (If we unite these two systems into a single system this process is considered to be transduction.) If the free energy cannot be lowered before arrival, because locally it already is a minimum, i.e., there is local thermodynamic equilibrium, then no loss is possible. If upon arrival the work performance is possible only if all the locally available free energy is utilized and other than that no process is possible, then the transduction preserves the free energy. So the point is that during transport and transduction the system as a whole is in local thermodynamic equilibrium and is already at a local minimum of free energy. Dissipative and conservative mechanisms are shown in Fig. 1. Dissipative mechanismsThe dissipative theories can be classified according to the element that supposedly carries the free energy to be conserved. The elements can be electrons, phonons, conformons, and polarons.McClare (1) proposed a mechanism in which resonant electronic excitation energy is transferred between two sites. This mechanism was originally proposed by Kallmann and London (2) for molecules in a gas phase. It is very unlikely that the structures necessary to support resonant electronic 3669 structures exist in mitochondria and that the excitation energy should not become thermalized within a short time (3). Shohet and Reible (4) proposed a phonon mechanism of free energy transfer between an emitter and an absorber. The phonon is emitted, transmitted through a medium, and finally absorbed. It is difficult to see how a phonon can be focused so that it goes to the absorber with certainty. It is virtually impossible to imag...

“…In the charge pair model presently under development (1)(2)(3)(4)(5) the pairing of opposite charges is the fundamental principle by which the operation of mitochondria and of other bioenergetic systems is rationalized. This pairing has so far been treated as a postulate.…”

Section: Introductionmentioning

confidence: 99%

“…For dielectric constants 10 or less pairing is absolute, for 20 there is some tendency towards pairing, and at 78 it is nonexistent. Pairing, partner exchange or charge substitution, inhibition, and antiport uncoupling can be rationalized within this framework.In the charge pair model presently under development (1)(2)(3)(4)(5) the pairing of opposite charges is the fundamental principle by which the operation of mitochondria and of other bioenergetic systems is rationalized. This pairing has so far been treated as a postulate.…”

mentioning

confidence: 99%

Physical basis of charge pairing in mitochondria.

Kemény¹,

Singer²

1975

The postulate of charge pairing in the mitochondrial inner membrane is justified by applying a formula due to Fuoss to calculate the probability density for the distance between a positive and a negative charge. For dielectric constants 10 or less pairing is absolute, for 20 there is some tendency towards pairing, and at 78 it is nonexistent. Pairing, partner exchange or charge substitution, inhibition, and antiport uncoupling can be rationalized within this framework.In the charge pair model presently under development (1)(2)(3)(4)(5) the pairing of opposite charges is the fundamental principle by which the operation of mitochondria and of other bioenergetic systems is rationalized. This pairing has so far been treated as a postulate. Due to its fundamental significance it needs to be justified and its limitations must be explored.The distribution of all charges in and near the mitochondrial inner membrane is a problem of discouraging complexity unless some simplifying principle is recognized. The experimental techniques available in the field tend to focuson the electrons in the electron transfer chain. This point of view does not seem to lead to a successful theory. It was necessary to recognize that energy passes between two charges (6, 7), and that these charges are of-opposite sign (1). One of them can be the electron. Classification of charge separationsThere are two fields which have historically dealt with the distribution of charges from the point of view of our present interests. One is physical chemistry, as exemplified by the theory of catalysis (8), which deals with charge separations of the order of 1 A. The other one is the theory of electrolytes (9), which is valid for distances between charges larger than a few Angstroms, so that specifically quantum mechanical effects can be ignored. The medium here is characterized by a dielectric constant, which of course also means charge separation, but on a scale usually much smaller than 1 A. The charge separations of primary bioenergetic interest fall into the range of competence of the theory of electrolytes.The separation of ions in electrolytic solutions was investigated by Fuoss (9, 10). If one positions a negative ion at the center of coordinates, the probability density G(r) of finding the nearest positive ion between distances r and r + dr is G(r) = 47rr2p exp -47rp f x2e~/xdx}, In an electrolytic solution charges of both signs are free to move in three-dimensional space. The only restrictions arise from the mutual electrostatic interaction of the ions themselves and their distance of nearest approach a in Eq. [1]. This means that there is a competition between the energetic effect of the attractive Coulomb interaction favoring the nearest possible approach of opposite charges and the entropy effect favoring separations of the order of p -" due to the larger configurational volume available at larger separations. Low values of the dielectric constant make the Coulomb interaction dominant and charges tend to pair. High values of the dielec...