i) Although in its free form nitric oxide is a relatively unstable and potentially
toxic gas, in biological system it is involved in blood pressure regulation and
blood clotting, neurotransmission, and the immune response against tumor
cells.
ii) The 1998 Nobel Prize in Medicine was awarded to the scientists (R. F.
Furchgott, L. J. Ignarro, and F. Murad) who discovered that NO is an important
signaling molecule (chemical messenger).
- Radical are capable of randomly damaging all components of the body because
they are highly reactive.
- Radical are believed to be important in the “aging process” in the sense that
radicals are involved in the development of the chronic diseases that are life
limiting.
- Radical are important in the development of cancers and in the development of
atherosclerosis (動脈粥樣硬化).
- Superoxide (O 2 −) is a naturally occurring radical and is associated with both the
immune response against pathogens and at the same time the development of
certain diseases.
1) An enzyme called superoxide dismutase regulates the level of superoxide in the
body.
- Radicals in cigarette smoke have been implicated in inactivation of an antiprotease
in the lungs which leads to the development of emphysema (氣腫).
- Radical reactions are important in many industrial processes.
- Polymerization: polyethylene (PE), Teflon (polytetrafluoroethylene, PTFE),
polystyrene (PS), and etc.
- Radical reactions are central to the “cracking” process by which gasoline and
other fuels are made from petroleum.
- Combustion process involves radical reactions.
