Note on a Rosalind Franklin note

In the caption to figure 4d of my Physics Today article about Rosalind Franklin (March 2003, page 42 ), I had interpreted Franklin’s writing “i.e. chains are in pairs, one upside-down wrt the other” as meaning that she had “determined that the backbone chains of A-form DNA are antiparallel.” It was recently pointed out to me that the statement could mislead readers into believing that those chains were definitely within one molecule, as opposed to possibly being in adjacent molecules. However, if Franklin had definitely realized that the two chains of the A form were within one molecule, she probably would have had a more obvious eureka moment.

I stand corrected as a result of a mutual acquaintance recently informing me that the expert, Franklin’s Birkbeck colleague Aaron Klug, thought my interpretation unjustified. However, the error does not affect my overall conclusion that Franklin was close to solving DNA structure by herself—a conclusion reached independently by both Klug and Crick.