| double displacement mechanism | A special multisubstrate reaction in which, for a two-substrate, two-product (i.e., bi-bi) system, an enzyme reacts with one substrate to form a product and a modified enzyme, the latter then reacting with a second substrate to form a second, final product, and regenerating the original enzyme. An example of such a mechanism is found in the aminotransferases. More complex ping-pong mechanisms exist for enzymes having more than two substrates. Synonym: double displacement mechanism. (05 Mar 2000) |
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| double-ender | A locomotive with pilot at each end. Source: Websters Dictionary (01 Mar 1998) |
| double-entendre | A word or expression admitting of a double interpretation, one of which is often obscure or indelicate. Origin: F. Double double + entendre to mean. This is a barbarous compound of French words. The true French equivalent is double entente. Source: Websters Dictionary (01 Mar 1998) |
| double first | <engineering> A degree of the first class both in classics and mathematics. One who gains at examinations the highest honor both in the classics and the mathematics. Source: Websters Dictionary (01 Mar 1998) |
| double flap amputation | <orthopaedics, surgery> Amputation in which a flap is cut from the soft parts on either side of the limb. (05 Mar 2000) |
| double fracture | A fracture in two parts of the same bone. Synonym: double fracture. (05 Mar 2000) |
| double helix | <molecular biology> Conformation or shape that two linear strands of DNA assume when bonded together and become twisted into a helix. (10 Nov 1998) |
| double hemiplegia | Paralysis of corresponding parts on both sides of the body. Synonym: double hemiplegia. Origin: G. Di-, two, + plege, a stroke (05 Mar 2000) |
| double immunodiffusion | See: gel diffusion precipitin tests in two dimensions. (05 Mar 2000) |
| double inlet atrioventricular connections | Connections in which both atrial chambers connect to the same ventricle. (05 Mar 2000) |
| double intussusception | <gastroenterology, surgery> A second intussusception that involves the bowel above the first; the first intussusception is followed by contraction of the bowel wall around it, and the solid mass so formed is enveloped by the proximal portion of the bowel and is thus the cause of the second intussusception. (05 Mar 2000) |
| double layer | <physiology> The zone adjacent to a charged particle in which the potential falls effectively to zero. An excess or deficiency of electrons on the surface (charge, not to be confused with the transmembrane potential) leads to an equivalent excess of ions of the opposite charge in the surrounding fluid. For most cells, that have negative charges, there will be an excess of cations immediately adjacent to the plasma membrane and at physiological ionic strength the double layer is likely to be around 2-3 nm thick. (10 Oct 1997) |
| double lip | Congenital or acquired excess tissue on the inner mucosal aspect of the lip; may be a manifestation of Ascher's syndrome. (05 Mar 2000) |
| double loop hernia | The presence of two loops of intestine in a hernial sac. Synonym: double loop hernia. (05 Mar 2000) |
| double-masked experiment | A double-blind study conducted so neither the subject nor the observer know the identity of the control or variable. (05 Mar 2000) |