Deoxyribonucleic Acid (DNA), the most crucial molecule in the body, is one of the largest of the macromolecules in the body, weighing over 2 billion daltons. DNA molecules are enormously long chains of atoms wound around proteins. If it were to be unwound, the DNA molecule in a single cell would be more than 2 meters in length. Each protein is comprised of amino acids packed into structures called chromosomes within the cell nucleus. The human cell contains 46 chromosomes. DNA is the hereditary molecule in all cellular life forms, including many viruses. The DNA molecule is frequently referred to as the "master molecule" because it contains all of the genetic information necessary for the functioning of the living organism.

The DNA molecule is called the genome, which is a collection of genes. A gene is a section or stretch of DNA. In humans, the genes are situated in the 46 chromosomes. Humans have upwards of 100,000 genes. Genes express themselves in what are termed "gene products," which are proteins comprised of amino acids. Encoded within the DNA molecule are all of the physical, biological, and most of the behavioral characteristics of an individual. For further details on the DNA molecule see Watson, 1969; Alberts et al., 1983: Sarma and Sarma, 1998. The nature and importance of the DNA molecule has been briefly presented because DNA is a target molecule of major importance in atherosclerosis, cancer, radiation sickness, and numerous chronic degenerative diseases.

In ionization, one or more electrons are dislodged from an orbital of the atom by violent collisions, as in the event of an electrical discharge. DNA is the most important primary target of the dislodged electrons. About half of the radiation damage in the cell is believed due to the energy targeted to the DNA molecule (Kapland and Moses, 1964; Myers et al., 1980). Two possible actions may take place, one of which is known as "direct action." This direct action takes place when the electron originating from the DNA molecule or from a neighboring molecule directly strikes and disrupts the DNA molecule. The initial ionization takes place with extreme rapidity, in about one-trillionth of a second.

In the case of X-rays, an estimated two-thirds of radiation damage is due to "indirect action." This occurs when the liberated electron does not strike the DNA molecule directly, but instead hits a water molecule, which is the most abundant molecule in the cell. The resulting ionization of the water molecule produces a free radical. The free radical reacts very strongly with other molecules as it attempts to restore a stable configuration of orbital electrons.

A free radical my drift about in the cell upwards of ten million times longer than the time required for initial ionization. This time lag suggests that other substances, such as nutrients could be introduced to neutralize free radicals, before they do much damage (Faden et al., 1994).

Neutrons can be extremely damaging since they act quite differently from some other types of radiation. A fast neutron will bypass orbiting electrons and may crash directly into an atomic nucleus, knocking out large particles such as alpha particles, protons, or fragments of the nucleus. The most common collisions are with carbon or oxygen nuclei. The particles thus created will then ionize carbon or oxygen nuclei. On the other hand, a slow neutron will not have sufficient energy to knock out large particles when it strikes the nucleus, resulting in the neutron and the nucleus of the atom bouncing off each other like two billiard balls. Eventually, the neutron will slow down, and the nucleus will gain energy. The most common collision is with a hydrogen nucleus, a proton that can excite or ionize electrons in nearby atoms.

DNA damage and ionized radiation are discussed here because patients suffering from coronary heart disease, cerebral vascular occlusive disease and other forms of atherosclerosis are frequently exposed to excessive amounts of diagnostic radiation, thus contributing to free radical production and the disease process.

Source:Free Radicals Test

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