alpha helix

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 [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.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

α he·lix

the helical form (commonly right-handed) present in many proteins, deduced by Pauling and Corey from x-ray diffraction studies of proteins such as α-keratin; the helix is stabilized by hydrogen bonds between, differet eupeptide bonds, for example, R1R2C = O and HN(R3)R4' groups, symbolized by the center dot in R1R2C = O · HN(R3)R4. In a true α helix, there are 3.6 amino acid residues per turn of the helix and an increase of 1.5 Ǻ per residue.
Farlex Partner Medical Dictionary © Farlex 2012

alpha helix

A secondary structure of proteins, characterized by a single, spiral chain of amino acids stabilized by hydrogen bonds.

al′pha-hel′i·cal (-hĕl′ĭ-kəl, -hē′lĭ-) adj.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

alpha helix

A specific form of folding of the polypeptide backbone in fibrous and globular proteins; right-handed corkscrew arrangement of a polypeptide chain is maintained by intrachain hydrogen bonding. The alpha helix is a major structural protein motif deduced by Pauling and Corey, and it occurs as bundles in keratin, myosin, fibrin and the epidermis.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

alpha helix

A coiled configuration of a POLYPEPTIDE chain found in many proteins. This is one of the commonest forms of secondary structure in proteins.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

alpha helix

a twisted polypeptide chain which forms a helical structure in many proteins, with 3.6 amino-acid residues per turn of the helix. Successive turns of the helix are linked by weak hydrogen bonds and the structure is much more stable than an untwisted polypeptide chain. Long-chain alpha-helix construction is characteristic of structural ‘fibrous’ proteins, found in hair, claws, fingernails, feathers, wool and horn. Proteins that are intracellular are usually of the ‘globular’ type with short segments of alpha helixes.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005


Linus C., U.S. chemist and Nobel laureate, 1901-1994.
Pauling theory - a theory of narcosis pertaining to nonhydrogen-bonding agents. Synonym(s): hydrate microcrystal theory of anesthesia
Pauling-Corey helix - the helical form present in many proteins. Synonym(s): α helix
Medical Eponyms © Farlex 2012
References in periodicals archive ?
Caption: Figure 7: (a) shows that the full-length sequence of NcGRA9 contains an N-terminal signal peptide (red), an alpha helix with amphipathic characteristics (blue), a hydrophobic alpha helix (yellow), and a PEST motif at the C-terminus of the protein (light blue).
Alpha helix is the most frequently observed element of secondary structure from -5 to -3 and from +1 to +5 positions (about 35-45%).
Those regions are abbreviated according to the flanking "major" secondary structure elements ("H" is alpha helix and "B" is beta strand).
The algorithm predicted the formation of an alpha helix on the carboxyterminal region with high probability (>0.8), although no known functional domain was identified.
My new awakening led me to Alaska again for a solo springtime trek, 75 miles over the Resurrection Pass from a town called Hope on the Turnagain Arm of the Cook Inlet (near Anchorage) to Seward, the home port of the R/V Alpha Helix, near Prince William Sound.
The highest top1 value is 0.74, which is achieved when binary classifiers in the remote-3DI method with 'Alpha helix propensity derived from designed sequences' and SVM c=100 as multi-class classifier are used.
Dietz and Rief found that by using an AFM to pull on just one small coil, called an alpha helix, at the edge of this barrel, they can make the protein highly unstable.
In an alpha helix, amino acids coil into a spiral, with 3.6 amino acids making up each turn of the helix.
The grubby sculpin protein has a tight spiral structure known as an alpha helix. The researchers substituted a few negatively charged amino acids for neutral ones in the antifreeze protein so that it would bind to the positively charged ions on the surface of calcite.
This newly identified spiral is more compressed and its loops wider than those in an alpha helix, the twist in a typical protein, notes Fred E.
A computer program designed to predict the structure of proteins based on their amino acid sequence concluded that this stretch should twist like a telephone cord into what's called an alpha helix. But in June 1990, when Zhang made the peptide and then analyzed its twist with an instrument called a spectropolarimeter, he realized that it looked nothing like a telephone cord.
The most common secondary structures are the alpha helix and the ribbon-like beta-pleated sheet (see top diagram, p.346).