15th September, 1955.
Dear Dr. Fraenkel-Conrat,
During the course of our discussions in Brussels you mentioned that it might be possible for you to send me some Hg-TMV which had less tendency to gel, and in which the amount of Hg bound was known with greater precision.  This would be extremely valuable to us.  I have now got quite good photographs from the Hg-TMV you sent, but before embarking on a lengthy quantitative study of the diagrams it would be preferable to look at the better preparation.
Would it be possible to prepare polymerized A-protein with Hg on it?  This would be even more useful than the Hg-TMV as far as the investigation of the structure of the protein part is concerned.  The equator of the A-protein diagram is so completely different from that of normal TMV that knowledge of the TMV diagram cannot be used to determine the signs for A-protein.  Hg-A-protein would make it possible to bridge the gap.
Best wishes,
Yours sincerely,
Rosalind Franklin.