Mechanical force-activated

Mechanical force-activated drug delivery systems... 

Mechanical Force-Activated Drug Delivery Systems... 

Effective mechanical power The energy spent in overcoming external mechanical forces on the body, in W, normally ignored for most activity. 

In 1936, de Boer formulated his theory of a stressed bond which, despite its simplicity, still constitutes the basis for most models of chemical reactivity under stress [92], In order to fracture an unstressed bond which, in the absence of any vibration, is approximated by the Morse potential of Fig. 18, an energy D must be supplied. If, however, the bond is under tension due to a constant force feitt pulling on either end, the bond rupture activation energy will be decreased by an amount equivalent to the work performed by the mechanical force over the stretching distance from the equilibrium position. The bond potential energy in the presence of stress is given by ... 

The mechanical behavior of the contractile apparatus of smooth muscle is also very similar to that of striated muscle. So that to the extent that the force-velocity curves reflect the interaction of mechanical force and the rate of enzymatic catalysis, the steps of the chemomechanical transduction cycles in the two muscles are apparently modulated in similar ways. Also relationships between the active isometric force and muscle length are very similar (except as noted above for shorter lengths). 

Quantum mechanics is essential for studying enzymatic processes [1-3]. Depending on the specific problem of interest, there are different requirements on the level of theory used and the scale of treatment involved. This ranges from the simplest cluster representation of the active site, modeled by the most accurate quantum chemical methods, to a hybrid description of the biomacromolecular catalyst by quantum mechanics and molecular mechanics (QM/MM) [1], to the full treatment of the entire enzyme-solvent system by a fully quantum-mechanical force field [4-8], In addition, the time-evolution of the macromolecular system can be modeled purely by classical mechanics in molecular dynamicssimulations, whereas the explicit incorporation... 

Mechanical forces such as shear and surface tension affect enzyme activity by disturbing the shape of the enzyme molecule. Since the shape of the active site of the enzyme is specifically engineered to correspond to the shape of the substrate, even small changes in structure may drastically affect enzyme activity. Consequently, fluid flow rates, stirrer speeds, and foaming must be carefully controlled in order to ensure that an enzyme s productivity is maintained. 

As indicated by the previous research, the electrode process between collector and sulphide mineral on its surface is closely related to the surface activity of the mineral, which is greatly influenced by grinding in flotation process. It is very important to investigate the influence of mechanical force on the mineral electrode process so as to reveal the surface process of the sulphide minerals. 

Mechanical forces can disturb the elaborate structure of the enzyme molecules to such a degree that de-activation can occur. The forces associated with flowing fluids, liquid films and interfaces can all cause de-activation. The rate of denaturation is a function both of intensity and of exposure time to the flow regime. Some enzymes show an ability to recover from such treatment. It should be noted that other enzymes are sensitive to shear stress and not to shear rate. This characteristic mechanical fragility of enzymes may impose limits on the fluid forces which can be tolerated in enzyme reactors. This applies when stirring is used to increase mass transfer rates of substrate, or in membrane filtration systems where increasing flux through a membrane can be accompanied by increased fluid shear at the surface of the membrane and within membrane pores. Another mechanical force, surface... 

Reducing the course material in size in a colloid mill or by means of ultrasonic waves generally does not lead to a higher distribution ratio, i.e. to smaller particles. As it is smaller particles tend to form larger ones under the influence of mechanical forces and due to the attraction between the particles. These problems are solved to a large extent when a surface active substance and possibly a solvent are added during the reduction process. 

All the quantities on the right hand side of the equation may be calculated using molecular mechanics force fields. However, it should be remembered that in many cases the binding of a drug to its target should be weak, because in most cases it has to be able to leave the target after it has activated that site. 

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