| nonsense triplet | A trinucleotide (codon) in which a base change to a termination codon results in premature termination of the growing polypeptide chain and, consequently, incomplete protein molecules, a termination codon. (05 Mar 2000) |
|---|---|
| triplet | <microscopy> A combination of three simple lenses cemented together. Two positive lenses with a negative lens between them can produce a well-corrected system. (05 Aug 1998) |
| triplet state | A second excited state of a molecule (e.g., chlorophyll) produced by absorption of light to produce the singlet state, then loss of some energy (fluorescence) to arrive at the longer-lived triplet state The molecule may remain sufficiently long in the triplet state for a second activating light quantum to be effective in producing a "second triplet" state, obviously at still a higher level of excitation, hence reactivity. Alternatively, it may lose the triplet state energy directly and return to the ground state. (05 Mar 2000) |
| alactic oxygen debt | That part of the oxygen debt that is not lactacid oxygen debt; during recovery, stores of ATP and creatine phosphate must be replenished by oxidative metabolism, and a small amount of oxygen is also needed to restore the normal oxyhemoglobin levels throughout the circulating blood. (05 Mar 2000) |
| alveolar-arterial oxygen difference | The difference or gradient between the partial pressure of oxygen in the alveolar spaces and the arterial blood: P(A-a)02. Normally in young adults this value is less than 20 mm Hg. See: alveolar gas equation. (05 Mar 2000) |
| arteriovenous oxygen difference | <physiology> The difference in the oxygen content (in ml per 100 ml blood) between arterial and venous blood. (05 Mar 2000) |
| biochemical oxygen demand | The amount of oxygen aerobicorganisms need to carry out oxidative metabolism in watercontaining organic matter, such as sewage. (09 Oct 1997) |
| carbon-oxygen ligases | <enzyme> Enzymes that catalyze the joining of two molecules by the formation of a carbon-oxygen bond. Registry number: EC 6.1 (12 Dec 1998) |
| carbon-oxygen lyases | <enzyme> Enzymes that catalyze the cleavage of a carbon-oxygen bond by means other than hydrolysis or oxidation. Registry number: EC 4.2 (12 Dec 1998) |
| reactive oxygen species | Reactive intermediate oxygen species including both radicals and non-radicals. These substances are constantly formed in the human body and have been shown to kill bacteria and inactivate proteins, and have been implicated in a number of diseases. Scientific data exist that link the reactive oxygen species produced by inflammatory phagocytes to cancer development. (12 Dec 1998) |
| chemical oxygen demand | The amount of dissolved oxygen required to combine with chemicals in wastewater. A measure of the oxygen equivalent of that portion of organic matter that is susceptible to oxidation by a strong chemical oxidizing agent. (05 Dec 1998) |
| rubredoxin-oxygen oxidoreductase | <enzyme> Contains fad and a new type of haem; site of oxygen reduction to water by desulfovibrio gigas coupled with NADH oxidation Registry number: EC 1.9.3.- Synonym: rubredoxin oxidase (26 Jun 1999) |
| phosphorus-oxygen lyases | <enzyme> Enzymes that catalyze the cleavage of a phosphorus-oxygen bond by means other than hydrolysis or oxidation. Registry number: EC 4.6 (12 Dec 1998) |
| critical dissolved oxygen concentration | <biology> The minimum concentration of oxygen in the water needed for the growth of a culture which has been submerged, where oxygen is the limiting factor to the growth of the culture. (09 Oct 1997) |
| heavy oxygen | A stable oxygen isotope making up 0.20% of natural oxygen; used in mass spectrometry and in NMR studies of tissue. Synonym: heavy oxygen. (05 Mar 2000) |