Systems-based models of international relations also underlies the vision of the international sphere held by the liberal institutionalist school of thought, which places more emphasis on systems generated by rules and interaction governance, particularly economic governance. Applications
Systems modeling is generally a basic principle in engineering and in social sciences. The system is the representation of the entities under concern. Hence inclusion to or exclusion from system context is dependent on the intention of the modeler. No model of a system will include all features of the real system of concern, and no model of a system must include all entities belonging to a real system of concern. Information and computer science
In computer science and information science, system is a hardware system, software system, or combination, which has components as its structure and observable inter-process communications as its behavior. Again, an example will illustrate: There are systems of counting, as with Roman numerals, and various systems for filing papers, or catalogues, and various library systems, of which the Dewey Decimal Classification is an example. This still fits with the definition of components which are connected together (in this case to facilitate the flow of information). System can also refer to a framework, aka platform, be it software or hardware, designed to allow software programs to run.
Cofactor for nitric oxide synthase
Nitric oxide synthase (NOS) catalyses the conversion of a guanidino nitrogen of L-arginine (L-Arg) to nitric oxide (NO). Among other things, nitric oxide is involved in vasodilation, which improves systematic blood flow. The role of BH4 in this enzymatic process is so critical that some research points to a deficiency of BH4 – and thus, of nitric oxide – as being a core cause of the neurovascular dysfunction that is the hallmark of circulation-related diseases such as diabetes. Cofactor for ether lipid oxidase
Ether lipid oxidase (alkylglycerol monooxygenase, AGMO) catalyses the conversion of 1-alkyl-sn-glycerol to 1-hydroxyalkyl-sn-glycerol. History
Tetrahydrobiopterin was discovered to play a role as an enzymatic cofactor. The first enzyme found to use tetrahydrobiopterin is phenylalanine hydroxylase (PAH). Biosynthesis and recycling
Tetrahydrobiopterin is biosynthesized from guanosine triphosphate (GTP) by three chemical reactions mediated by the enzymes GTP cyclohydrolase I (GTPCH), 6-pyruvoyltetrahydropterin synthase (PTPS), and sepiapterin reductase (SR).BH4 can be oxidized by one or two electron reactions, to generate BH4 or BH3 radical and BH2, respectively. Research shows that ascorbic acid (also known as ascorbate or vitamin C) can reduce BH3 radical into BH4, preventing the BH3 radical from reacting with other free radicals (superoxide and peroxynitrite specifically). Without this recycling process, uncoupling of the endothelial nitric oxide synthase (eNOS) enzyme and reduced bioavailability of the vasodilator nitric oxide occur, creating a form of endothelial dysfunction. Ascorbic acid is oxidized to dehydroascorbic acid during this process, although it can be recycled back to ascorbic acid.