Navigation Links
Alpha helix


In proteins, the α helix is a major structural motif in secondary structure. It was first postulated by Linus Pauling, Robert Corey , and Herman Branson in 1951 based on the known crystal structures of amino acids and peptides and Pauling's prediction of planar peptide bonds.

The amino acids in an α helix are arranged in a helical structure, about 5 wide. Each amino acid results in a 100 turn in the helix, and corresponds to a translation of 1.5 along the helical axis. The helix is tightly packed; there is almost no free space within the helix. All amino acid side-chains are arranged at the outside of the helix. The N-H group of amino acid (n) can establish a hydrogen bond with the C=O group of amino acid (n+4).

Short polypeptides usually are not able to adopt the alpha helical structure, since the entropic cost associated with the folding of the polypeptide chain is too high. Some amino acids (called helix breakers) like proline will disrupt the helical structure.

Ordinarily, a helix has a buildup of positive charge at the N-terminal end and negative charge at the C-terminal end which is a destabilizing influence. As a result, α helices are often capped at the N-terminal end by a negatively charged amino acid (like glutamic acid) in order to stabilise the helix dipole. Less common (and less effective) is C-terminal capping with a positively charged protein like lysine.

α helices have particular significance in DNA binding motifs, including helix-turn-helix motifs, leucine zipper motifs and zinc finger motifs. This is because of the structural coincidence of the α helix diameter of 12 being the same as the width of the major groove in B-form DNA.

α helices are one of the basic structural elements in proteins, together with beta sheets.

The peptide backbone of an α helix has 3.6 amino acids per turn.

See also: tertiary structure -- β sheet -- collagen helix

References


'"/>


(Date:3/24/2015)... ( http://www.researchandmarkets.com/research/kvdtcw/face_and_voice ) has announced the addition of the ... report to their offering. This report analyzes the worldwide ... following Segments: Face Biometrics, and Voice Biometrics. The report provides separate ... Japan , Europe , ... Africa , and Latin America . ...
(Date:3/23/2015)... SoundView Technology Group issues a new research update following the ... wallet. SoundView was one of the selected user groups to provide ... in multiple scenarios and outlets. Soundview shares ... both debit and credit card payments.  Soundview ... meets their plans in 2015, it would push our IV ...
(Date:3/23/2015)... Inc. (NASDAQ: NXTD ) ("NXT-ID" or the "Company"), a ... announces its biometric payment technology, the Wocket® smart wallet, will ... 30 th . The new 30 ... markets. Gino Pereira , ... ad campaign following the recent initial shipment of Wocket smart ...
Breaking Biology News(10 mins):Face and Voice Biometrics - Global Strategic Business Report 2015: Face Recognition Gains Prominence in Immigration Control 2Face and Voice Biometrics - Global Strategic Business Report 2015: Face Recognition Gains Prominence in Immigration Control 3Face and Voice Biometrics - Global Strategic Business Report 2015: Face Recognition Gains Prominence in Immigration Control 4Face and Voice Biometrics - Global Strategic Business Report 2015: Face Recognition Gains Prominence in Immigration Control 5Face and Voice Biometrics - Global Strategic Business Report 2015: Face Recognition Gains Prominence in Immigration Control 6Technology Research Note Update from SoundView; Real-World Usage and Feedback of Wocket Smart Wallet at CVS, Whole Foods and other Retailers 2Technology Research Note Update from SoundView; Real-World Usage and Feedback of Wocket Smart Wallet at CVS, Whole Foods and other Retailers 3Technology Research Note Update from SoundView; Real-World Usage and Feedback of Wocket Smart Wallet at CVS, Whole Foods and other Retailers 4NXT-ID's Wocket Smart Wallet to Launch New CNBC Regional TV Ad Campaign 2NXT-ID's Wocket Smart Wallet to Launch New CNBC Regional TV Ad Campaign 3
... The University of California, San Diego, with support ... Whitaker Foundation, has installed a supercomputer dedicated to ... The 210-node Dell PowerEdge Linux cluster capable of ... most powerful computer cluster on campus, will be ...
... of Mayo Clinic-led researchers is first to devise a ... therapeutic killer that hunts down and destroys cancer cells ... as an advanced electronic article of Nature Biotechnology. , ... commandeering cells, and then redirected the virus to attack ...
... attacks share a genetic profile that appears to be ... by researchers at Cincinnati Children's Hospital Medical Center. The ... treatments specifically tailored to children who suffer from the ... the Feb. 10 issue of the Journal of Allergy ...
Cached Biology News:Supercomputer Dedicated To Bioengineering, Computational Biology Installed 2Supercomputer Dedicated To Bioengineering, Computational Biology Installed 3Mayo Clinic Researchers Create 'Obedient Virus'; First Step To Use Measles Virus Against Cancer 2Asthma gene clusters identified 2Asthma gene clusters identified 3
Other biology definitionOther Tags