Stimulated conformational movements

Theoretical models available in the literature consider the electron loss, the counter-ion diffusion, or the nucleation process as the rate-limiting steps they follow traditional electrochemical models and avoid any structural treatment of the electrode. Our approach relies on the electro-chemically stimulated conformational relaxation control of the process. Although these conformational movements179 are present at any moment of the oxidation process (as proved by the experimental determination of the volume change or the continuous movements of artificial muscles), in order to be able to quantify them, we need to isolate them from either the electrons transfers, the counter-ion diffusion, or the solvent interchange we need electrochemical experiments in which the kinetics are under conformational relaxation control. Once the electrochemistry of these structural effects is quantified, we can again include the other components of the electrochemical reaction to obtain a complete description of electrochemical oxidation. 

This analytical dilemma and the non-conformity of test results obtained for complex, heterogeneous measurands stimulated a movement towards standardization implemented by various international organizations such as the IFCC (Table 6). All these efforts tried to follow metrologically established rules according to the International Vocabulary of Basic and General Terms in Metrology (VIM) [38] and ISO-CEN standards (Table 7)... 

Both the theoretical model and this basic molecular actuator include electric pulses, ions and water interchanges between the polymer and the solution, chemical reactions, stimulation of the conformational movements along polymeric chains, and changes in the inter- and intramolecular interactions. Those processes occurring in soft and wet materials mimic, at the molecular level, the consecutive events involved in the actuation of a natural anisotropic muscle. 

Stimulation of the conformational relaxation movements of the polymeric chains (by repulsion between the nascent positive charges), with the generation of free volume. Local nuclei or general and simultaneous relaxation occur, depending on the initial compaction of the polymer film. 

Any factor that affects the size or shape of a molecule, the hindered movement of a fluorophore within a molecule, or the energy transfer within the molecule will affect the measured depolarization of its fluorescence emission. Therefore, the conformation of humic fractions in solution can be studied as a function of pH, ionic strength, temperature, and other factors by depolarization measurements. The principle of the method is that excitation of fluorescent samples with polarized light stimulates... 

Tropomyosin is an elongated protein that lies along the thin filament and prevents the association of myosin with actin in the resting state. Troponin is a complex of three polypeptide chains TnC, Tnl and TnT. Ca2+ ions released into the sarcoplasm from the sarcoplasmic reticulum in response to a nerve stimulation bind to TnC and cause a conformational change in the protein. This movement is transmitted by an allosteric mechanism through Tnl and TnT to tropomyosin, causing the latter to move out of the way and allowing the actin and myosin to associate. 

As already pointed out in the case of rotaxanes, mechanical movements can also be induced in catenanes by chemical, electrochemical, and photochemical stimulation. Catenanes 164+ and 174+ (Fig. 19) are examples of systems in which the conformational motion can be controlled electrochemically [82, 83], They are made of a symmetric electron acceptor, tetracationic cyclophane, and a desymmetrized ring comprising two different electron donor units, namely a tetrathiafulvalene (TTF) and a dimethoxybenzene (DOB) (I64 1) or a dimethoxynaphthalene (DON) (174+) unit. Because the TTF moiety is a better electron donor than the dioxyarene units, as witnessed by the potentials values for their oxidation, the thermodynamically stable conformation of these catenanes is that in which the symmetric cyclophane encircles the TTF unit of the desymmetrized macrocycle (Fig. 19a, state 0). 

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