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The Rosalind Franklin Papers

Letter from Alexander Rich to Rosalind Franklin pdf (137,384 Bytes) transcript of pdf
Letter from Alexander Rich to Rosalind Franklin
During her 1954 visit to the United States, Franklin made many new contacts among the virus researchers all over the country. Alexander Rich was working on studies of TMV protein that closely paralleled Franklin's and they were in frequent communication during 1955. Bothered by some measurements he had provided her for an article she was about to send to press, Franklin cabled Rich to double-check his results. He replied via telegram that he had made an error, and followed up with this letter, in which he analyzed her latest results in detail.
Number of Image Pages:
2 (137,384 Bytes)
1955-03-24 (March 24, 1955)
Rich, Alexander
National Institutes of Health (U.S.)
Franklin, Rosalind
Original Repository: Churchill Archives Centre. The Papers of Rosalind Franklin
This item is in the public domain. It may be used without permission.
Medical Subject Headings (MeSH):
Tobacco Mosaic Virus
Exhibit Category:
Envisioning Viruses: Birkbeck College, London, 1953-1958
Metadata Record Telegram from Alexander Rich to Rosalind Franklin (March 21, 1955) pdf (115,431 Bytes) transcript of pdf
Folder Number:
Unique Identifier:
Document Type:
Letters (correspondence)
Series: Work on Tobacco Mosaic Virus (TMV)
Folder: Correspondence Regarding Franklin's Research, 1953-1958
March 24, 1955
Dear Rosalind:
I am terribly sorry to have made a "butch" in measuring the birefringence of these films. Indeed, the birefringence is -.002 instead of + .002. This mistake is all the more interesting since the introduction of RNA into TMV changes it from negative to positive birefringence, while the RNA itself, paradoxically, has a negative birefringence. How can it be that introducing a negatively birefringent molecule into a protein shell, which itself is negatively birefringent, produces something which is positively birefringent? Here is a conundrum, indeed.
I found your manuscript quite interesting. I believe that your explanation is correct, namely, that the introduction of further water into these protein films does, in fact, pull apart the helix so that the repeat distance changes. I think that one can make an analogy between the photographs which you have obtained at different humidities with the Perutz photographs of hemoglobin. There, by changing the salt concentration, he was able to move the molecule in and out over different distances, and was thereby able to sample the transform of one molecule at different points due to the alteration of the latter function. Here, by changing the water in the nucleic acid free protein helix, one is able to make the helix expand and contract, thereby sampling the transform at different layer line spacings. The transform in this case is not the transform of the individual monomeric units, but rather something which is close to the transform of this monomeric unit rotated around the axis. It seems, from your description, that the protein is able to go from a state which has roughly 37 or so units in three turns repeating in 68 angstroms into something which has roughly two turns in 45 angstroms perhaps with 25 units or so in this repeat distance. In other words, small changes in the positioning of the helical coil changes the layer line spacings in this way. It is apparently just an accident that the photographs that I had have the same spacing as TMV, implying that the protein, at this hydration packed in a manner which is similar to the arrangement of the protein in the TMV. On introducing more water, this apparently no longer holds. At any rate, I am going to test this by seeing whether I can take one of these films which gave me the very bad pictures which you saw here, and finding whether increasing humidity in this film will produce the changes which you have described. I think that the demonstration of these changes makes the whole problem much more interesting, in that it produces the possibility of obtaining the complete transform for the cylindrically symmetric monomeric units throughout reciprocal space in a way similar to way similar to what was done with the hemoglobin.
Newmark has sent me more of the TMV material and I hope to make more films. However, the first batch that he sent me proved to be unpolymerized, and so I am unable to do anything at the moment. However, I hope to be able to do more work here in the short future.
My plans regarding the spring are still somewhat indefinite, and I'll let you know more about them later.
Sincerely yours,
Alexander Rich, M.D.
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