A molecule is a structure formed of atoms of various elements. It is the smallest concentration of same or different atoms that all chemical characteristics retain.

See also Free Radicals, Osmole, Enzyme Linked lmmuno Sorbent Assay, Gas Chromatography and Gel Chromatography.

Radiation can ionize matter caused by the high energy which displaces electrons during interactions with atoms. In the electromagnetic spectrum higher frequency ultraviolet radiation begins to have enough energy to ionize matter.
Examples of ionizing radiation include alpha particles, beta particles, gamma rays, x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of producing ions by direct or secondary processes in passage through tissues.
Damage of living tissue results from the transfer of energy to atoms and molecules in the cellular structure. Ionized cells have to repair themselves to remain alive. Generally, healthy cells have a higher capability to repair themselves than cancer cells.

Biological effects of ionizing radiation exposure:
Ionizing radiation are used in a wide range of facilities, including health care, research institutions, nuclear reactors and their support facilities, and other manufacturing settings. These radiation sources can pose a serious hazard to affected people and environment if not properly controlled.

See also Radiation Safety, Controlled Area, Radiotoxicity and As Low As Reasonably Achievable.

An assay is an analytic test to detect the presence, measure the concentration, and determine the biological activity of molecule, ions, or cells. Assays are based on measurable parameters that enable the evaluation of differences between samples and controls. Sensitivity, the ability to detect small amounts of a substance, and specificity, the ability to detect only the analyte, are essential features of an assay.

See also Bioassay, Biochemical, Biohazards, Biokinetic Model and Bioaccumulation Factor.

(ELISA) An enzyme linked immuno sorbent assay, also called ELISA, or enzyme immunoassay (EIA) is a diagnostic tool to measure the concentration of a particular molecule.

See also Radioimmunoassay.

Free radicals are highly reactive molecules or ions containing unpaired electrons. Free radicals are likely to take part in chemical reactions.