Activation

Definition
noun
(general) The state or the process of being active and/or effective
(biochemistry) The process of making a molecule reactive, active, or effective in carrying out its function; also referred to as bioactivation
(immunology) The transition of an immune cell, as in immunologic activation
(radiobiology) That which occurs when a particle interacts with an atomic nucleus, shifting the nucleus into an unstable state, and causing it to become radioactive
Supplement
In general, the term activation refers to the state or the process of making something active and/or effective. In biochemistry, it is often associated with a molecule becoming more reactive, active, or excited for the next reaction. For instance, in the translation step of protein biosynthesis, activation is an initial step in which the correct amino acid is covalently bonded to the correct tRNA. This is an essential step for translation to proceed. Activation (or bioactivation) may also mean the process or state of becoming more effective in carrying out a particular function. For instance, the activation of an enzyme would make the latter perform its specific biological function. Another example is when an inactive prodrug is converted into an active metabolite.
In radiobiology, activation (also referred to as radioactivation) occurs when a particle interacts with an atomic nucleus, shifting the nucleus into an unstable state, and causing it to become radioactive. in fusion research, where deuterium-tritium is a common fuel mixture, the neutron released when (D – T) combine to form (4He – n) can activate the reactor structure. In this case the 4He is inert, the neutron sticks to another nucleus, and the neutron – nucleus reaction creates an activation product.
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