Letter from H. Fraenkel-Conrat to Rosalind Franklin
Heinz Fraenkel-Conrat was one of many virus researchers that Franklin visited during her 1954 trip to the United States. Like
many others, he was able to send her samples of the materials he was using. The TMV with heavy atoms, such as mercury, added
would help Franklin calculate the structure of TMV more accurately. In this letter he provided details of the various heavy-atom
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1955-10-20 (October 20, 1955)
University of California, Berkeley
Original Repository: Churchill Archives Centre. The Papers of Rosalind Franklin
Thank you for your letter of September 15. I have been busy preparing and analyzing samples which might be of interest to
you. I believe that sample # 230X represents a better mercury derivative (denaturation having been more successfully prevented
in the course of preparation) than the earlier preparation. It contains 0.99 percent Hg (1/20000).
I have also attempted introduction of limited amounts of iodine on the tyrosine groups. Preparation 228IIB is iodinated 230X.
The mercury blocks the -SH group and all the iodine (about one per 18,000) is on one (or several) phenolic groups. Preparation
228IIC is TMV into which 2 iodine atoms were introduced (per 18,000),-- one on the -SH group and one on tyrosine.
Your other request was mercuri-TKV protein. We have prepared small samples at various times, but have not yet investigated
to what extent this material aggregates to rods of what length, and at what pH. Also we always have so many uses for good
protein fractions that we never have much to spare. I will send you about 15 mg as a pellet (235A) obtained from protein
+ methylmercuric nitrate after adjustment to pH 5.5. The same limitation in regard to amounts holds for the reconstituted
virus which you expressed an interest in when writing to Dr. Williams. We are making so many small samples (1-3mg) in combining
different preparations of nucleic acid, different strain proteins and nucleic acids, etc. that we have not had enough materials
for a "preparative" experiment, followed by centrifugal separation of bigger rods from smaller stuff. If you definitely
believe that this material would be of interest to you, please let me know how much you need, and I will try and prepare it