Franklin's relations with both Watson and Crick improved greatly once she moved from King's College to Birkbeck College,
and she was in regular contact with both as she worked on the structure of TMV. In this letter, Watson sent Franklin news
of recent TMV work at Berkeley, and Don Caspar's calculations of the TMV protein density. Caspar would go to work with
Franklin later that year.
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1955-02-28 (February 28, 1955)
Watson, James D.
California Institute of Technology. Kerckhoff Laboratories of Biology
Original Repository: Churchill Archives Centre. The Papers of Rosalind Franklin
I have recently returned from Berkeley and the Virus Laboratory. While I was there, I saw some very pretty Electron Micrographs
taken by Roger Hart, a student of Robley Williams. They definitely establish that the RNA forms a central core of diameter
30 angstroms and 50 angstroms. What they do is look at TMV particles which have been partially degraded by treatment with
dodecyl sulfate for several minutes at 85 degrees. After treatment many particles look like [diagram] or [diagram], while
if a ribonuclease treatment follows the heat-detergent, the protruding fibers disappear and the degraded rods look like [diagram]
or [diagram]. To complete the story they have micrographs of X-protein (polymerized) which occassionally [sic] show end on
sections of the following appearance [diagram].
At the same time Don Caspar has been calculating Fouriers from his Gieger [sic] Counter Data. He suspects the obvious sign
combination is not correct but that a plus, minus, minus plus assignment is more reasonable. It produces a high density shell
at 22 angstroms which he
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interprets as the location of the phosphorus atoms, as well as a region of high density at 42 angstroms. When his data are
more complete (we hope within 2 weeks) he shall send them to you. If true its quite exciting as the arrangement of the RNA
within the virus must be remarkably different than that found after extraction.