| colour radical | The part of a visibly coloured molecule responsible for light absorption over a range of wavelengths thus giving rise to the colour. By extension the term may be applied to UV or IR absorbing parts of molecules. Do not confuse with chromatophores. (18 Nov 1997) |
|---|---|
| hydroxyl radical | <chemical> Hydroxyl. The univalent radical oh. This radical is characteristic of hydroxides, oxygen acids, alcohols, glycols, phenols, and hemiacetals. Chemical name: Hydroxyl (12 Dec 1998) |
| oxygen radical | <chemistry> Any oxygen species that carries an unpaired electron (except free oxygen). Examples are the hydroxyl radical and the superoxide anion. These radicals are very powerful oxidizing agents and cause structural damage to proteins and nucleic acids. They mediate the damaging effects of ionising radiation. (18 Nov 1997) |
| extended radical mastectomy | Excision of the entire breast including the nipple, areola, and overlying skin, as well as the pectoral muscles and the lymphatic-bearing tissues of the axilla and chest wall and internal mammary chain of lymph nodes. (05 Mar 2000) |
| bacteria-free stage of bacterial endocarditis | Endocarditis described prior to the antibiotic era and presumably due to spontaneous healing of the bacterial vegetations. (05 Mar 2000) |
| carbon dioxide-free water | Purified water that has been boiled vigorously for 5 minutes or more. (05 Mar 2000) |
| germ-free animal | An animal which has no microorganisms whatsoever living in or on it. An animal which was born and raised in an isolated environment with no microorganisms in it, such as within a germ-free isolator. (09 Oct 1997) |
| germ-free isolator | A chamber which has absolutely no microorganisms whatsoever living in it, where a germ-free animal can be born and raised. An artificial barrier surrounding a living facility for germ-free animals, which keeps out all microorganisms. (09 Oct 1997) |
| germ-free life | Animals not contaminated by or associated with any foreign organisms. (12 Dec 1998) |
| carrier-free | A substance in which a radioactive or other tagged atom is found in every molecule; the highest possible specific activity. (05 Mar 2000) |
| gibbs free energy | The total amount of energy which is either used up or released during a chemical reaction. Gibbs free energy (delta G) = (delta H) - t (delta s): where (delta H) is the change in enthalpy, calculated by adding up the amount of energy released or used up to break or form chemical bonds during the reaction, t is the temperature at which the reaction took place, and (delta S) is the change in entropy, or amount of disorder, that occurs in the molecules involved during the reaction. (09 Oct 1997) |
| mean free path | <radiobiology> Average distance a particle travels between occurrences of the given event, for example, between collisions. For collisions, the mean free path is roughly equal to unity divided by the product of the collision cross-section times the particle density. (09 Oct 1997) |
| cell-free extract | <cell culture> A liquid that is a mixture of the contents of a particular type of cell, sometimes the organelles are also filtered out of the liquid. (26 Mar 1998) |
| cell-free protein synthesis | <technique> An in vitro method to make proteins, using amino acids, the mRNA corresponding to the protein to be made, and a cell-free extract (the contents of a cell after removal of the cell wall and/or outer cell membranes) for other needed components and enzymes. (26 Mar 1998) |
| cell-free system | <cell culture, molecular biology> Any system in which a normal cellular reaction is reconstituted in the absence of cells for example in vitro translation systems that will synthesise protein from mRNA using a lysate of rabbit reticulocytes or wheat germ. A fractionated cell extract that maintains a biological function. A subcellular fraction isolated by ultracentrifugation or other separation techniques must first be isolated so that a process can be studied free from all of the complex side reactions that occur in a cell. The cell-free system is therefore widely used in cell biology. (12 Dec 1998) |