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Published Papers
| The π Helix - A Hydrogen Bonded Configuration of the Polypeptide Chain. October 30, 1952. |
Page 01
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Authors: Barbara Low, R.B. Baybutt
Page 01
| Title: |
The π Helix - A Hydrogen Bonded Configuration of the Polypeptide Chain [1 of 2] |
| Creator: |
Low, Barbara |
| Contributor: |
Baybutt, R.B. |
| Publisher: |
|
| Date: |
1952-10-30 |
| Subject: |
Chemical bonds
Chemical structure
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| Description: |
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| Type: |
Text |
| Format: |
text/plain |
| Language: |
en |
| Identifier: |
03-low-pg01.jpg |
| Source: |
Master scanned with Epson GT-10000+ flatbed scanner at 600 dpi. |
| Rights: |
http://osulibrary.orst.edu/specialcollections/coll/pauling/dna/copyright.html |
| Full Text: |
THE π HELIX - A HYDROGEN BONDED CONFIGURATION
OF THE POLMPTIrE CHAIN
Sir:
In a recent letter, Dr. Iii. L. I uggis sl proposed C, new
helical polypeptide chain configuration as a possible alterna-
tive to the Pauling-Corey a helix . In the Huggins structure,
the amide group is not planar and, as Pauling and Corey3 have
observed, the strain energy is great in comparison with the a
helix. There is, however, a helical configuration for the poly-
peptide chain not hitherto described which satisfies all the
major Pauling, Corey and Branson4 restrictions and which can be
formed using the Corey-Donohue5 polypeptide chain dimensions.
The configuration is obtained when the polypeptide chain is
coiled into a "helical form in such a gray that each amide group
is hydrogen bonded to the fourth amide group beyond it along the
chain. In this sense, it is intermediate between the a and y
helices in which the amide groups are hydrogen bonded to the
third and fifth amide groups beyond them respectively. We have
named it, therefore, the π helix.6 There are approximately 4.4
amino acid residues per turn, with a unit residue translation
along the helical axis of approximately 1.14 A, giving a pitch
of about 5 A. The structure involves some slight distortion
(less than 5°) in the in,ra-chain a carbon bond angle. Angular
distortions of the 'tetrahedral; carbon bond angle of this order
are not unknown? and changes of less that's 5' should introduce
only a small amount of strain energy.
There is a cylindrical hole doer: the cent_o of the
and it has been critized on this basis. The hole is less wide
than that down: the center of the y helix, and it is, therefore,
not large enough to accommodate a water molecule. Thus, there
is no way of bridging; the long intra-chain van den Waal's dis-
tances across the cavity. Since the original Paining-Corey re-
strictions were enunciated, a further stereochemical limitation
has been postulated by these workers9, which is considered adequate
to exclude the y helix completely. The restrictions are concerned
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