Conformational basis of energy transduction in mitochondria
The conformational mechanism of energy transduction which we proposed in 1967 was based on an intuitive evaluation of the significance of large amplitude configurational changes which parallel energized processes in mitochondria [l-3] . By now a considerable body of information has been accumulated about the details of the configurational transitions in the mitochondrion [4-61. Moreover, the theory of structured systems with the capability for conservation of energy by a conformational mechanism is now being developed systematically [7]. This interplay of experiment and theory has made it possible to formulate the conformational hypothesis more explicitly and precisely. The tripartite repeating unit of the cristal membrane is the molecular unit of mitochondrial energy transduction. While in theory each repeating unit is a complete operational unit, in practice we are dealing with two dimensional arrays of repeating units within a membrane continuum and with the cooperative effects intrinsic to such arrays. Each repeating unit contains three basic systems which collectively effectuate the conformational transduction of energy. These systems are (a) the primary energizing system (one of the complexes of the electron transfer chain), (b) the conformational frame system, and (c) the discharge-directing system (the ATPase complex is one such system). The electron transfer process within each complex of the chain leads to a conformational transition [8-lo]. But since the electron transfer system is enclosed within a rigid frame (the conformational frame system [ 7]), the conformational expansion of
Factors affecting the binding of antimycin A to complex 3 of the mitochondrial respiratory chain.
Abstract The nature of the binding of antimycin A to Complex III of the mitochondrial respiratory chain was investigated according to two procedures. In the first procedure, tritium-labeled antimycin A was extracted from its binding to Complex III either by acetone or by concentrated solutions of taurocholate. Seventy per cent of the complex-bound antimycin A was extracted by either reagent. The acetone-extracted antimycin A was found to be fully inhibitory to the reduced coenzyme Q-cytochrome c reductase activity of Complex III. Moreover, even though most of the antimycin A was extracted from Complex III by taurocholate, its inhibitory effect on the cleavage of the complex was retained. The second procedure utilized enzymically active Complex III as a reagent to detect antimycin A that failed to be bound to, or was released from, an enzymically inactive Complex III. The binding of antimycin A to intact Complex III was found to be essentially irreversible, little or no transfer of antimycin A from antimycin-treated complex to untreated complex being observed. High levels of detergent (3 to 5% taurocholate) in the reaction mixture permitted some transfer of the antimycin A. Conditions that normally caused cleavage of Complex III (i.e. bile salts plus ammonium sulfate, or 1.0 m guanidine), or digestion with trypsin, destroyed the capacity of the complex to bind antimycin A. Reagents that cleaved Complex III despite the treatment of the complex with antimycin A (i.e. 3.0 m guanidine, 0.2 m guanidine plus freezing, or taurocholate plus mersalyl) also caused a release of antimycin A from the complex. Noninhibitory derivatives of antimycin A (i.e. the O-methyl ether of antimycin or deformylantimycin A) offered little or no competition to antimycin A in its binding to Complex III.
Comparison of different antenna configurations for probing of layered media
The paper presents the results of a comparative analysis of the different configurations of antenna systems (bistatic, monostatic, differential) in terms of the simplicity and accuracy of determining the thickness of the subsurface layers of stratified environment. To this end, corresponding diffraction problems are solved by the finite-difference time-domain forward solver for each measurement setup. The analysis has shown the advantages and prospects of using differential system with vertically spaced antennas in solving of practical problems of the layered medium GPR probing.