Controlled release processes enzymes

The vesicles were separated by centrifugation at 30,000 x g from the enzyme solution. Precipitated PC vesicles underwent a washing process once and were resuspended with the phosphate buffer solution (PBS) and adjusted to 25 ml. Stimuli which have the potential to induce the controlled release of enzyme from PC vesicles in suspension were examined in terms of the releasing pattern. Original vesicles suspensions were stimulated by mixing with an equal volume of a stimulus solution in glass vials with... 

Initially, the sol gel compositions were optimized using Congo red dye as the dopant because of its optical properties. This facilitates monitoring of the release process by optical spectroscopy. Next, the gels were evaluated for their stabilization and release of subtilisin. These sol gel matrices bring about controlled release of the encapsulated enzyme molecules as a response to a change in the water content of the medium (Figure 2.20).15... 

The production of serotonin requires the absorption of the amino acid tryptophan from your food. Transport of this amino acid is influenced by the level of other amino acids in your blood that level, in turn, is also influenced by what you eat. Within the neurons of your brain, tryptophan is converted to 5-hydroxy-tryptophan by tryptophan hydroxylase, an enzyme that is usually not saturated with substrate. Therefore, if you eat less tryptophan, your brain generally produces less serotonin. Conversely, providing additional tryptophan in the diet may lead to increased production of serotonin within neurons. It is worth noting, however, that simply producing more of any neurotransmitter does not guarantee that the neuron will actually release it. If too much serotonin is produced, then the excess is simply discarded. Studies have shown that only extreme depletion or supplementation of this amino acid in the diet can influence serotonin-controlled brain processes such as mood and sleep. 

Factors analogous to those affecting gut absorption also can affect drug distribution and excretion. Any transporters or metabolizing enzymes can be taxed to capacity—which clearly would make the kinetic process nonlinear (see Linear versus Nonlinear Pharmacokinetics ). In order to have linear pharmacokinetics, all components (distribution, metabolism, filtration, active secretion, and active reabsorption) must be reasonably approximated by first-order kinetics for the valid design of controlled release delivery systems. 

Living systems rely on kinetic stability for their existence. They are all thermodynamically unstable that is, they would burn up to form carbon dioxide and water if the system reaches thermodynamic equilibrium. In other words, life processes depend upon the ability to restrict these thermodynamic tendencies by controlled kinetics to produce energy as needed. A key feature of living systems is thus the use of catalysts for the controlled release of that energy. Examples of such catalysts are enzymes that control the synthesis and degradation of biologically important molecules. 

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