| 释义 |
levan Chem.|ˈliːvæn|
[f. lævo-, levo- + -an, after dextran.]
A lævulosan (fructan); esp. any fructan of the kind produced by certain bacteria, in which the linking of adjacent fructose units is between the second carbon atom of one unit and the sixth of the next.
1902R. G. Smith in Proc. Linn. Soc. New South Wales XXVI. 603 From a review of the lævo-rotatory gummy substances that are hydrolysed to levulose, it appears that this bacterial gum has not hitherto been described. I therefore propose for it the name levan, which was suggested by the polariscopic nature of the gum and derived glucose, and also from the fact that another bacterial gum, which is derived from dextrose, and which yields dextrose on hydrolysis, is known as dextran. 1948W. Pigman Chem. Carbohydrates xv. 604 Fructosans or levans are found widely distributed throughout the plant kingdom..and generally serve as reserve polysaccharides in place of, or in addition to, starch. 1953Whistler & Smart Polysaccharide Chem. xi. 276 d-Fructose polymers occurring in plants..are designated as fructans while those elaborated by microorganisms are called levans... Actually the levans are structurally similar to some of the plant polyfructoses. 1965T. Akazawa in Bonner & Varner Plant Biochem. xii. 287 Although the size of these substances is small, 3–30 hexose residues per molecule, their structure is basically the same as that of the high molecular bacterial levan produced by several microorganisms... The name grass levan has therefore been given to this group of plant compounds. A further interesting point is..that fructosans of inulin type, β-(2→1), and of levan type, β-(2→6), are the main constituents of stem and ear tissues, respectively, of cereal plants. |