| 释义 |
▪ I. ˈsupercoil, n. Biochem.
[super- 5 c.]
A coiled coil; spec. a structure sometimes assumed by DNA in which the double helix itself is coiled or looped. Cf. superhelix.
1965Peacocke & Drysdale Molecular Basis Heredity iv. 168 In the fibre, these molecules take the form of ‘super-coils’ in which the axis of the DNA helix is itself coiled with a pitch of 120Å and a diameter of 100Å. 1976Nature 10 June 516/1 Supercoils could be introduced into progeny molecules either before sealing of the closed circular form, or subsequent to an initial closing of the molecule. 1980Sci. Amer. July 100/2 Because the forces that stabilize the double helix are strong the closed circular molecules resist such underwinding, and..they compensate by forming supercoils.
▪ II. ˈsupercoil, v. Biochem.
[f. prec. n.]
a. trans. To make (a molecule) into a supercoil.
b. intr. To become a supercoil.
1967Jrnl. Molecular Biol. XXV. 28 Only molecules in which both strands are intact can be supercoiled in either sense. 1971Nature 29 Oct. 591/2 Segrest and Cunningham start with the tropocollagen molecule, a three-strand rope formed by supercoiling two indentical helices termed α1 and α2. 1982Sci. Amer. July 87/1 When the ethidium is removed, the ring [of DNA] supercoils.
Hence ˈsupercoiled ppl. a., having the structure of a coiled helix; ˈsupercoiling vbl. n., the action or result of forming a supercoil; also attrib.
1967Jrnl. Molecular Biol. XXV. 23 It would be desirable to have independent evidence on the direction of supercoiling and to obtain an estimate of the number of supercoiling turns. Ibid. 27 The supercoiled form of polyoma DNA can be converted to the unsupercoiled form by one single-strand scission. 1980Sci. Amer. July 100/1 Affecting DNA's in a wide range of sizes and shapes (including some that are not organized into a double helix), supercoiling takes a variety of forms. 1980Proc. Nat. Acad. Sciences LXXVII. 2445/1 A massive tangle of catenated supercoiled molecules. |