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
Conformational basis of energy transformations in membrane systems. 3. Configurational changes in the mitochondrial inner membrane induced by changes in functional states.
Abstract The cristae of the inner membrane of mitochondria have been shown to exist in three configurational states: nonenergized, energized, and energized-twisted. Electron transfer and hydrolysis of ATP are the two enzymic means of generating the energized state. The transition from the energized to the energized-twisted configurational state of the cristae is induced by inorganic phosphate in sucrose-containing media and by salts in sufficiently high concentrations in media that do not contain sucrose. The electron microscopic identification of the three configurational states is simplified by the diagnostic characteristics of the respective membranes. The configurational states are assumed to be gross expressions of the conformations of the repeating units in the nonenergized, energized, and energized-twisted states. The energized-twisted state is discharged by ADP (leading to oxidative phosphorylation), by divalent metal ions (leading to translocation), by monovalent salts (leading to energized swelling), and by uncouplers. Reagents which inhibit electron transfer or those which inhibit hydrolysis of ATP prevent the generation of the energized state by substrates and by ATP, respectively. The speed of configurational change in the cristae appears to be consistent with the thesis that the primary event in mitochondrial energy transformations is Conformational change of the repeating units. It is proposed that there are no high energy intermediate compounds; also, that the readily demonstrable energized states of the inner membrane are the functional equivalents of the elusive high-energy intermediates.
Enhancement of surface properties on Low Density Polyethylene packaging films using various fluorination routes
Nowadays, packaging market deployment requires an important attention. Influence of treatment with molecular (F2) or atomic (Fradical dot) fluorine on properties of Low Density Polyethylene (LDPE) films was investigated. The films were treated using direct fluorination conditions with F2 or a specific reagent XeF2, which releases atomic fluorine Fradical dot. Changes of LDPE chemical composition were investigated by FTIR and solid state NMR. Surface morphology was studied by several microscopy techniques (SEM and AFM). Finally to further characterize film properties after treatments, surface energy measurements and electron paramagnetic resonance (EPR) analyses were also carried out. An upper fluorinated layer, which contains mainly high amount of single bondCF2single bond, was formed during the direct fluorination conditions (F2). For the process performed with XeF2, specific groups single bondCHFsingle bond were detected not only on the polymer surface but also in the bulk. The final CHF/CF2 ratio depended on the fluorination route. Treatment with Fradical dot (originated from XeF2 decomposition) resulted in single bondCHFsingle bond groups in bulk prevailing formation whereas F2 formed mainly single bondCF2single bond groups. Regardless to the reactive species, radicals (dangling bonds) appeared during the fluorination and reacted with oxygen during the exposition to air after the treatment. Such a process resulted in oxygenated polar groups formation and consequently in the surface energy increase.