helix

(redirected from a-helix)
Also found in: Dictionary, Thesaurus, Encyclopedia.
Related to a-helix: alpha helix

helix

 [he´liks] (pl. he´lices, helixes) (Gr.)
1. a winding structure; see also coil and spiral.
2. the superior and posterior free margin of the pinna of the ear.
α-helix (alpha helix) the complex structural arrangement of parts of protein molecules in which a single polypeptide chain forms a right-handed helix.
double helix (Watson-Crick helix) the structure of deoxyribonucleic acid (DNA), consisting of two coiled chains, each of which contains information completely specifying the other chain.

he·lix

, pl.

hel·i·ces

(hē'liks, hel'i-sēz), [TA] Do not confuse this word with spiral.
1. The margin of the auricle; a folded rim of cartilage forming the upper part of the anterior, the superior, and the greater part of the posterior edges of the auricle.
2. A line in the shape of a coil (or a spring, or the threads on a bolt), each point being equidistant from a straight line that is the axis of the cylinder in which each point of the helix lies.
[L. fr. G. helix, a coil]

helix

(hē′lĭks)
n. pl. he·lixes or helices (hĕl′ĭ-sēz′, hē′lĭ-)
1. Mathematics A three-dimensional curve that lies on a cylinder or cone, so that its angle to a plane perpendicular to the axis is constant.
2. A spiral form or structure.
3. Anatomy The folded rim of skin and cartilage around most of the outer ear.
4. Architecture A volute on a Corinthian or Ionic capital.
v. he·lixed, he·lixing, he·lixes
v.tr.
To move or position (something) into the shape of a helix.
v.intr.
1. To have the shape of a helix.
2. To move along a helical course; spiral.
Anatomy The superior and posterior free margin of the pinna of the ear
Molecular biology A winding structural motif for nucleic acids and proteins

he·lix

, pl. helixes, pl. helices (hē'liks, -ĕz, hel'i-sēz)
1. [TA] The margin of the auricle; a folded rim of cartilage forming the upper part of the anterior, the superior, and the greater part of the posterior edges of the auricle.
2. A line in the shape of a coil (or a spring, or the threads on a bolt), each point being equidistant from a straight line that is the axis of the cylinder in which each point of the helix lies. usage note: Often mistakenly applied to a spiral.
[L. fr. G. helix, a coil]

helix

The folded margin of the outer ear. The form of the helix is determined by the underlying cartilage.

helix

(pl. helixes or helices) a form of spiral in which any point is at the same distance from the central axis. RNA molecules have a single helix, DNA is a double helix.
References in periodicals archive ?
Because a-helix 5 is a central helix, the forming of a salt bridge with [alpha]-helix 4 and an H-bond with [alpha]-helix 6 may increase the stabilization energy of domain I.
Oligomerization due to a-helix residues have been contributed to the toxin pore formation in insect larvae (Jimenez-Juarez et al., 2007).
In summary, substitution of the highly conserved H168 by Q or R in a-helix 5 of the Cry1Ac toxin resulted in changes in toxicity and stability which have helped to define better the role of this key amino acid residue in the properties and function of the Cry1Ac [delta]-endotoxin.
The role of a proline-induced broken-helix motif in a-helix 2 offBacillus thuringiensis d-endotoxins.
The role of a proline-induced broken-helix motif in a-helix 2 ofBacillus thuringiensis d-endotoxins.