Regulation, biological systems

The 11,12-oxido and 14,15-oxido analogs of leukotriene A4 were synthesized to help answer the question of whether these compounds might be biosynthesized from arachidonate by the 12- and 15-lipoxygenation pathways and serve as physiologic regulators. Hydrolysis products of the 14,15-oxide were later found to be formed in biological systems. 

Enzymes act as catalysts in biological systems to effectively regulate the rate of reactions and determine which products are formed. Enzyme-catalyzed reactions are often described by the Michaelis-Mentin mechanism that is represented by the following steps ... 

Cell membranes are not simply passive containers for the cell s contents. Rather, they are highly organized, dynamic, and stractiirally complex biological systems that regulate the transfer of specific chemicals throngh the cell wall. 

S -nitrosothiols, several of which occur naturally, e.g., iS -nitrosocysteine and S-nitrosoglutathione, have an important role in NO transport and regulation in biological systems. Potential applications of RSNO compounds include their use as vasodilators in the treatment of angina and in the search for a cure for male impotence.11 The most convenient route to S-nitrosothiol formation is the nitrosation of thiols. 

The Role of Phosphonates in Living Systems, Hilderbrand, R.L., Ed., CRC Press, Boca Raton, FL, 1983 — Contributed chapters survey the role of naturally occurring organophosphorus compounds (containing a C-P bond) in biological systems and the use of a wide variety of organophosphorus compounds for the regulation of metabolism and the treatment of disease. 

For the last 50 years many scientists have drawn special attention to nitrones due to their successful application as building blocks in the synthesis of various natural and biologically active compounds, of stable nitroxyl radicals, and of other important products for special purposes such as spin traps for the study of radical processes including those that take place in biological systems, and they also found use as both, modifiers and regulators of molecular weight in radical polymerization. 

Biological systems are open to the exchange of matter with their environment. If species from the medium (either nutrients or pollutants) travel towards the membrane and a net increase in their concentration arises in the cell, then an uptake process is occurring. Apart from the obvious importance for the organism itself, there is an impact on the medium (e.g. regulating the fate of pollutants in the environment). 

Legal limitations placed upon the use of all newly launched nonbiodegradable chemicals in Japan require testing each product for accumulation in fish before it can be marketed. These regulations have stimulated corresponding studies about the bioaccumulation of pigments [16]. The distribution coefficient Pow between n-octanol and water may be used to indicate the tendency of a chemical to accumulate in biological systems [17]. 

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