Pauling and Corey (1952)

December 1952: The understanding of the function and composition of nucleic acid has grown immensely since the turn of the century. However, understanding of the structure of this molecule has so far eluded even the most diligent researcher. In this paper, Linus Pauling descends from Olympus, grabs hold of his thunderbolt (an x-ray crystallographic thunderbolt that is, produced by Astbury as Hephaestus), and puts forward the first structure that fits the various parameters compiled over seventy-some odd years of investigations into this molecular cipher.
What assumptions are made in this prediction? Does the data support the structure? Is the alpha helix a suitable model for understanding the data?


9 Responses to “Pauling and Corey (1952)”

  1. Hunter Burgin Says:

    I find it very interesting to read up on the background information regarding important papers such as this. I read an article online regarding Pauling’s desire to be the “first to publish a roughly correct structure of DNA” rather than being the one to publish the definitively correct structure[1]. Articles such as this really give you an insight into the researcher’s head and their desire for fame/prominence within their respective field rather than actually contributing correct information.
    Anyways, on to my question: It’s fairly clear that Pauling and Corey relied heavily on X-ray crystallography to properly define the structure of nucleic acids. However when reading the paper I was unsure of what exactly they were trying to convey in figure 7. What exactly are they trying to explain with this graph?


  2. Porter Marsh Says:

    The paper says on page 6 that it has been found through trial that the pyrimidine and purine bases cannot fit in such a way that the sugar and phosphate can bind. I was wondering what they were referencing when they allude to some trials. There is no reference on either of the two preceding or following pages so what were they talking about? What data lead them to the conclusion that the bases couldn’t form the center of the helices?

  3. Tony tones Says:

    I’m very upset at the direction the paper is going. Why was no mention of a resoning behind the acidity know about DNA given? Where would a proton disassociate readily? Also why wasn’t columbic repulsion considered? How can the core be that negative and be held together?

    Also note page 93 wasn’t the n the package. It’s easily found online though.

    • profhurst Says:

      Tony, can you please re-post this comment. It is a very incomplete. I don’t follow your logic and the errors make it appear as if it was sent from your phone.

  4. Antony Says:

    I’m very upset at the direction the paper is going. Why was no mention of a resoning behind the acidity know about DNA given? Where would a proton disassociate readily? Also why wasn’t columbic repulsion considered? How can the core be that negative and be held together?

    Also note page 93 wasn’t the in the package. It’s easily found online though.

  5. Antony Says:

    It was well known at the time of the publication that DNA was relatively acidic. The structure proposed makes no justice to this observation. There in no proton that would account for the acidity. Or do you suggest any of those hydrogen as labile?

    Another skepticism Pauling and Corey should have had by proposing that phosphate was in the center was the fact that the negative charge concentrated could not be possible without coulombic repulsion coming into play. Wouldn’t the structure fall apart or what would hold it together?

    Notes: 1) Page 93 is not in package but easily found online. 2) I fail at WordPress. I get error messages when I hit submit and am not sure I submitted anything until I personally see my message. Can any repeats be deleted/ignored?

  6. Adam Settimo Says:

    I have to agree with Anthony above on the question of what makes this an acid. More to the point the paper proposes that tight phosphate packing in the middle and purine and pyrimidine bases rotating radially outward.

    Wouldn’t this give the overall structure a more basic character, since no interacting molecule could overcome the sterics to enter the center of the triple helix to remove hydrogens from in there (assuming thats where they would be)?

    One last thing, on the end of page 89 and the beginning of 90, are they proposing bridging hydrogen atoms?

  7. Kevin Greenwood Says:

    A triple helix with nucleotides facing out? I suppose when Pauling won the first of two Nobel Prizes the next year it must have taken the edge off of being so incorrect.

    It wasn’t all bad though. In this model, with all the bases pointed out and generally stacked above each other but slightly askew, pi stacking interactions occur between the nitrogenous bases, stabilizing the molecule. This is also seen in the current model of DNA. Granted, the data they were working with wasn’t great, Astbury’s photos were pretty blurry.

    Even so, it was (or really should have been) a big red flag that there was not enough room in the core of the triple helix. It was Corey that did the calculations that showed there wasn’t enough room to fit all the phosphates in the center, and a colleague pointed out that there wasn’t even enough room for sodium ions. Was it hubris that kept Pauling so devoted to this model? In figure 1 the sketch shows three phosphate groups attached with O-O bonds, which are not incredibly strong. The bond lengths given for these linkages are 2.3 Angstroms at the shortest, just under 1 full angstrom longer than the O-O bond length in hydrogen peroxide. This alone would significantly weaken the secondary structure of DNA. With such glaring mistakes, and without begging (more) to look at Wilkins’ data, why publish this?

  8. Daniel Begay Says:

    Going back to figuring out which molecules were being used near the core of the axis of the triple helix structure, they were looking for a group or molecule that would be well packed together, to make the structure stable. They said they figure out ‘by trial’ that the phosphate group to be the most reasonable answer. What exactly was the approach for their trials? What tools were used to figure this out? X-ray crystallography? The purine-pyrimidine was immediately thrown out because of its variety. in theory, what variations would cause for the possibility of instability? They also don’t go into detail about their reasoning for throwing out the idea of the sugar residues.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: