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"The DNA Story."

"The DNA Story." 1973.
Created by VSM Productions. Produced by Ronald Fouracre and Peter Shaw. Distributed by John Wiley & Sons, London, New York.

Pauling Discovers the Alpha-Helix. (2:40)

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Transcript

Linus Pauling: One day, when I was Eastman Professor at Oxford in the spring of 1948, I caught a cold. It was before the vitamin C days! I caught a cold and after a day or two in bed of reading science fiction and detective stories, I got tired of that, and thought, why don't I discover the alpha helix? Something like that - why don't I try to find how polypeptide chains are folded in a way compatible with all the knowledge we have of structural chemistry and such that they can form hydrogen bonds to hold the parts of the molecule together?

I took a piece of paper, much like this piece, and drew on it a representation of an extended polypeptide chain, with the distances approximately right and the angles right. Except, one angle did not have the right value. I still have that original piece of paper, by the way. This is the bond angle of the alpha carbon that didn't have the right value. I folded the paper - actually, it took several trials - I folded it along several parallel lines through the successive alpha carbons.

Finally, I found a way by folding the paper to make this bond have an angle of 110 degrees. I finally found a way of folding such that when I fit it together, there was an N-H-C-O bond formed by each N-H group, and each C=O group. The hydrogen bond held the structure together and had just the right dimensions. I found that this structure, which turned out to be the structure of hair and horn and fingernail, and also present in myoglobin and hemoglobin and other globular proteins, a structure called the alpha-helix, had 3.6 residues per turn of the helix. A helical structure where there are 3.6 residues per turn.

Clip

Creator: Linus Pauling
Clip ID: 1973v.3-alpha

Full Work

Creator: VSM Productions, Ronald Fouracre, Peter Shaw
Associated: Linus Pauling, Francis Crick, James D. Watson, Maurice Wilkins

Date: 1973
Genre: video
ID: 1973v.3
Copyright: More Information

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