(n.) A shark of the genus Sphyrna or Zygaena, having the eyes set on projections from the sides of the head, which gives it a hammer shape. The Sphyrna zygaena is found in the North Atlantic. Called also hammer fish, and balance fish.
(n.) A fresh-water fish; the stone-roller.
(n.) An African fruit bat (Hypsignathus monstrosus); -- so called from its large blunt nozzle.
Example Sentences:
(1) Six additional divalent ions were tested for their ability to support hammerhead cleavage.
(2) However, a segment of approximately one-third of the PLMVd sequence has the elements required to form in the RNAs of both polarities the hammerhead structures proposed to act in the in vitro self-cleavage of avocado sunblotch viroid (ASBVd) and some satellite RNAs.
(3) When injected into the nucleus of frog oocytes, the ribozyme tRNA gene (ribtDNA) produces 'hammerhead' ribozymes which cleave the 5' sequences of U7snRNA, its target substrate, with high efficiency in vitro.
(4) All combinations of mutant substrate and mutant ribozyme were less active than the corresponding single mutations, suggesting that the hammerhead contains few, if any, replaceable tertiary interactions as are found in tRNA.
(5) Nine different hammerhead RNA self-cleaving domains consistent with the consensus secondary structure proposed by Keese and Symons (1987) were prepared and tested for cleavage.
(6) To investigate the binding properties of Mg2+ to the hammerhead ribozyme, cleavage rates and CD spectra for substrates containing inosine or guanosine at the cleavage site were measured.
(7) The hammerhead domains consist of a 34 nucleotide ribozyme bound to a complementary 13 nucleotide non-cleavable DNA substrate.
(8) Also, inversion of configuration at phosphorus is confirmed for a two-stranded hammerhead.
(9) Based on comparisons with self-cleaving plant viral satellite RNAs, hammerhead-shaped active structures, each containing one self-cleavage site, were proposed for the plus and minus ASBV RNAs and the newt RNA, but the stability of these hammerheads has been questioned.
(10) Here, we show that the purified full-length dimeric plus RNA, when incubated under our standard self-cleavage conditions, also self-cleaved by a double-hammerhead structure.
(11) The hammerhead ribozyme, as engineered by J. Haseloff and W. L. Gerlach [(1988) Nature (London) 334, 585-591], is an RNA molecule containing two regions of conserved nucleotides, a double helix, called helix II, which connects the two conserved regions, and flanking arms of variable sequence, which hybridize the ribozyme to its specific target.
(12) Insertion, deletion and base substitution mutations were carried out on a 58 base RNA containing the sequence of the single-hammerhead structure of the plus RNA of the virusoid of lucerne transient streak virus, and the effects on self-cleavage assessed.
(13) Analysis of the cleavage products of several of these hammerhead analogues confirms the involvement in the reaction of the 2'-OH adjacent to the cleavage site in the substrate, and demonstrates that some 2'-OH groups in the catalytic region strongly affect activity.
(14) The oligoribonucleotides were used as substrates in the study of the mechanism of cleavage of an RNA hammerhead domain having the phosphorothioate group at the cleavage site.
(15) These catalytic RNAs, or ribozymes, form a stem-loop secondary structure called a 'hammerhead' in which the catalytic (ribozyme) and substrate sequences are brought close together.
(16) Two sequence variants contained nucleotide changes in the double hammerhead-like self-cleaving structure identified in ASBV RNA.
(17) We have designed a hammerhead-type RNA system which consists of three RNA fragments for normal and modified complexes which contain a non-cleavable substrate with 2'-O-methylcytidine and a guanosine-to-inosine replaced enzyme.
(18) Although related to the hammerhead structure, sequences flanking the plus strand termini showed differences from the consensus and may be folded into a different structure containing a pseudo-knot.
(19) We have constructed and characterised in vitro a number of hammerhead ribozymes designed to cleave individual RNAs encoded by these genes.
(20) Substitutions of DNA for RNA in the various stems of a hammerhead ribozyme have been analyzed in vitro for kinetic efficiency.