Our objective is to propose an overview of the usefulness of skeletal myofibril as an experimental system for studying mechanochemical coupling of skeletal muscles and myosin ATPase activity. The myofibril is a true functional mini-muscle that is able to contract in the presence of ATP. It also contains the machinery necessary for the calcium sensitivity of the contraction. In the absence of calcium, myofibrillar ATPase activity is basal, no shortening

We obtained the temperature dependences of the adenosine triphosphatase (ATPase) activities (calcium-activated and relaxed) of myofibrils from a slow muscle, which we compared with those from a fast muscle. We chose rabbit soleus and psoas because their myosin heavy chains are almost pure: isoforms I and IIX, respectively. The Arrhenius plots of the ATPases are linear (4-35 degrees C) with energies of activation for soleus myofibrils 155 kJ mol(-1)

It has been suggested that the mechanical condition determines the rate-limiting step of the ATPase of the myosin heads in fibers: when fibers are isometrically contracting, the ADP release kinetics are rate-limiting, but as the strain is reduced and the fibers are allowed to shorten, the ADP release kinetics accelerate and P(i) release becomes rate-limiting. We have put this idea to the test with myofibrils as a model because with these both mechanical

The “tension surface” defined by Gibbs in treating the interface area is structurally specified by a “transition layer” made up by the outer Helmholtz plane and the one containing the surface active centres. In the “double mixed electrode layer” model, considered to be one step taken towards the microscopic-level understanding of the electrolyte interface phenomena, the electrochemical sensors operations, as well as the electric phenomena

The model “double mixed electric layer” presents an interpretation variant for the cyclic voltammogram and for the polarography mechanism, from the point of view of the interface charge transfer phenomena, mediated by the solution donor-acceptor “impurities”. We assign a concrete physical significance for the current steps and peaks, which are characteristic to the cyclic voltammograms. The paper accredits the idea of the free electron pairs

A mechanism for electronic conduction in electrolyte solutions is presented. The structure of the electrode-electrolyte interface and the molecules in the ion solvation layer are the important element in this mechanism. The electrolyte chooses between one structure with a minimum electrical resistance and another one with a high electrical resistance as a function of the scanning rate value of the potential. The minimum resistance in the electronic

Our study uses two alternative graphical methods for the spectrophotometric analysis of the pigment mixtures. The first one permits to taken data at multiple wavelengths in order to generate linear plots, from which the concentrations can be determined. It is used for the two and three component mixtures. The second one is a graphical technique for the solution of simultaneous equations. It is carried out on a triangular composition plot for a threecomponent

Carotenoids (Car) regulate energy flow in photosynthesis by a specific Car-chlorophyll (Chl) interaction in the singlet-excited states, leading to a reduction in Chl fluorescence. We studied quenching of Chl a-fluorescence in benzene by trans--carotene. Non-linear analysis of the quenching process enables to explain the possible molecular mechanism leading to the de-excitation of Chl a. The fluorescence intensity was measured at 670 nm for excitation