Critique of a Structure for Deoxyribose Nucleic Acid

The April 25, 1953 issue of Nature magazine had within its pages an extraordinary article by J. D. Watson and F. H. C. Crick entitled “A Structure for Deoxyribose Nucleic Acid”. The significance of this paper resides in its proposal of a structure of DNA previously unknown. Watson and Crick began their article with a literature review about a model of DNA earlier introduced by Pauling and Corey. They briefly talk about the problems they associate with this model before continuing on to discuss their hypothesis on the subject.

Beginning their discussion on their newly proposed structure of DNA, Watson and Crick say “this structure has two helical chains each coiled round the same axis”. This should sound familiar to modern day scientist because it is what we call the “alpha helix” model of DNA today. Watson and Crick then say they made the “usual chemical assumptions”, when starting to construct their new model of DNA. These assumptions included the facts of DNA that were generally accepted during their time, namely that DNA consisted of phosphate diester groups joining beta-D-deoxyribofuranose residues with 3’,5’ linkages. Unfortunately, this is where their discussion starts to wavier. In the midst of their extensive analysis of DNA structure, they make a comment about the sugar in DNA, “It is probably impossible to build this structure with a Ribose sugar in place of Deoxyribose, as the extra oxygen atom would make to close a van der Waals contact”. This particular statement is confusing to me seeing as one of the key differences in RNA and DNA is the replacement of the Deoxyribose sugar with a Ribose sugar.

Considering that Watson and Crick’s proposed structure of DNA was based mainly on already gathered experimental data, their proposal is rather impressive. They based their structure of DNA on just the compatibility of the experimental data and stereochemical arguments they had at hand and did a remarkable job. The structure they presented was...