During her 1954 visit to the United States, Franklin visited many virus researchers who would subsequently collaborate with
her on projects involving virus structures. Barry Commoner sent her samples of a protein he called B8, to compare with the
x-ray diffraction studies of TMV protein. They subsequently published several articles together. In this letter, Franklin
reported on her first diffraction photos of B8, and suggested that a different preparation of the sample might give better
pictures. She included a description of how she was able to concentrate the B8 solution in the absence of an ultra-centrifuge.
The centrifuge was one of several items for which she repeatedly sought ARC funding.
Number of Image Pages:
2 (119,858 Bytes)
1955-03-04 (March 4, 1955)
[Washington University. Henry Shaw School of Botany]
Original Repository: Churchill Archives Centre. The Papers of Rosalind Franklin
Reproduced from the Franklin Collection at the Churchill Archives Centre with the permission of the copyright holder.
My first photograph of your B8 gives a rather intriguing result. The fibre-axis repeat which correspond, in TMV, to the pitch
of the helix, has increased from 23A to 27A. Rich and Dunitz found, for Newmark's protein X, that the pitch has decreased
by about 5% with respect to TMV. They worked with dry oriented material (and are now proposing to look at gels). In TMV,
the pitch is the same for the dry material and the gel. So that my result seems to suggest that, although the protein alone
has the property of polymerising into a helical TMV-like structure, the RNA core is necessary to keep it properly fixed in
position. In the absence of the core, it can apparently undergo a change similar to the stretching of a spring. This is,
of course, consistent with your observation that B8 is slightly less rigid than TMV.
You mentioned that you have a further 10 m.g. of this preparation which you could send me if necessary. Is it possible to
obtain B8 as a spontaneously and homogenously birefringent solution? If it is, and if you were able to concentrate a second
batch into this form before sending, it would be very much worth while. There not being an ultracentrifuge anywhere in this
college, I concentrated the solution you sent me simply by allowing it to evaporate slowly through the dialysis bag. This
produced a gel which could be seen, in the microscope, to be a 2-phase system containing fibrous regions of rather low birefringence,
suspended in a non-birefringent solution. My X-ray photograph is of this fibrous gel. Orientation of such a material is
never very good. I have tried the obvious things, such as changing the pH and adding small quantities of salt, but failed
to obtain a homogenous birefringent solution.
As this 'fibrous gel' state often occurs in TMV also, I am hopeful that correct treatment might produce a homogenous
concentrate from B8. If this is so, there is no reason why I should not get photographs from B8 as good as those from TMV.
Moreover, the opening and closing of the structure by adding and removing water gives interesting possibilities from the point
of view of X-ray studies. My present photograph shows little detail other than the strong meridional (or near-meridional)
maxima, and it is unlikely that I can get much more out of it unless the orientation can be greatly improved.
In preparing a dry specimen (which I have not yet photographed) I observed that the birefringence changes from positive to
negative on drying. Rich reports that the birefringence of protein X is positive. Isn't this difference rather surprising?
I shall let you know of any further progress. Meanwhile I should very much like to have your comments on what has happened
so far, and on the possibility of obtaining a homogenous strongly by birefringent concentrate.