Hints of a Helix, circa 1947

Nearly four decades after biochemist Phoebus Levene first postulated his "tetranucleotide hypothesis" in 1910, most scientists still believed that DNA was made up of equal numbers of the four nucleotide bases in a repeating tetrameric structure, with each subunit containing all four bases.

Then in 1947, John Masson Gulland, together with Dennis Oswald Jordan and their colleagues at University College, Nottingham, perfected a method of extracting DNA from calf thymus glands. Importantly, their protocol avoided the use of acid or alkali, which kept the solution at a constant neutral pH, allowing them to isolate pure, fibrous, nondegraded DNA (labeled 'desoxyribose nucleic acid' in Gulland's handwriting on the vial at right). When they added strong acids or bases to the sample, however, electrometric titrations showed that hydrogen bonds rather than covalent bonds linked the amino and hydroxyl groups of the nucleotide bases.

These results, along with Erwin Chargaff's 1950 discovery that DNA contains equal amounts of adenine and thymine and equal amounts of cytosine and guanine, paved the way for James Watson and Francis Crick's discovery that the molecule is, in fact, a double helix. As Watson put it in The Double Helix (1970): "A rereading of J.M. Gulland's and D.O. Jordan's papers... made me finally realize the strength of their conclusion that a large fraction, if not all, of the bases formed hydrogen bonds to other bases."

Gulland died in a railway accident in northern England on October 26, 1947. "His death means a sad and irreparable loss to us all," Chagraff wrote in the Annual Reviews of Biochemistry in 1948 (17:201–26).

For anyone wanting to learn more about Gulland, Keith Manchester wrote an article for TiBS:
"Did a tragic accident delay the discovery of the double helical structure of DNA?"
Trends in Biochemical Sciences, Volume 20, Issue 3, March 1995, Pages 126-128

This was reprinted, together with a photograph of the railway accident in which Gulland was killed, in:
Witkowski, J. A. (ed.) "The Inside Story: From DNA to RNA to Protein" Cold Spring Harbor Laboratory Press. 2005.

These comments are absolutely correct but unfortunately historical reality has been submerged in the glory and beauty and politics of the double helix. While not to diminish the work of Watson and Crick or Franklin and Wilkins, these researchers, Gulland and Jordan and Erwin Chargaff did supply the evidence for the chemical and biophysical foundations for the double helix. Chargaff, in particular, while not completely innocent, got caught in skepticism and personality attack, leading to the loss of his own objectivity from which he never recovered.