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



(Date:4/22/2014)... Scientists from the Florida campus of The Scripps ... plays a critical but previously unknown role in learning ... a novel role for a protein known as RGS7, ... eLife , a publisher supported by the Howard Hughes ... Trust. , "This is a critical building block that ...
(Date:4/22/2014)... Massachusetts Amherst and the Instituto Nacional de Pesquisas da ... discovered a new genus and species of electric knifefish ... Amazonia State of Brazil. , Professor Cristina Cox Fernandes ... Alves-Gomes of INPA, describe the new bluntnose knifefish in ... the Natural Sciences of Philadelphia . , Their ...
(Date:4/22/2014)... same crystal structure as a mineral first found in ... efficiency charts faster than almost anything researchers have seen ... way of using sunlight to generate electricity may be ... Department,s National Renewable Energy Laboratory (NREL) are analyzing the ... and broad spectrum of expertise to uncover the secrets ...
Breaking Biology News(10 mins):Scientists identify critical new protein complex involved in learning and memory 2New electric fish genus and species discovered in Brazil's Rio Negro 2NREL unlocking secrets of new solar material 2NREL unlocking secrets of new solar material 3NREL unlocking secrets of new solar material 4NREL unlocking secrets of new solar material 5NREL unlocking secrets of new solar material 6
... brain that controls insulin responses has been shown to ... evidence that the disease can be treated in its ... Rhode Island Hospital and Brown Medical School. , ... prevent several components of neurodegeneration and preserve learning and ...
... known that animals use song as a way of attracting ... unusual way of scaring off predators ?by singing to them. ... that wild gibbons in Thailand have developed a unique song ... survival, the gibbons appear to use the song not just ...
... 21 September, 2006 - Elsevier is delighted to ... the journal Vaccine: HPV Vaccines and Screening in ... provides a comprehensive and invaluable update for paediatricians, ... major donor institutions worldwide. , With the arrival ...
Cached Biology News:Insulin receptor stops progression of Alzheimer's disease 2Insulin receptor stops progression of Alzheimer's disease 3Singing for survival 2Singing for survival 3
Other biology definitionOther Tags