Dr. H. Fraonkel-Conrat,
The Virus Laboratory,
University of California,

California, W.S.A.

BERKELEY 4,

21st February, 1956.

Dear Dr. Praenksl-Conrat,

myself, whiah we are sending to "Nature11.
seen a brief summary which I recently sent to Professor Stanley,
describing the same results.

I enclose two short malntscrlpts by Don Caspar and

You may also have

      As you will see, it is your Hg-TMV which has made 1%
possible to determine the location of the RNA in TWO 1 think
there can be little doubt that the RNA backbone ahaln(s?) lie on
8 radius close to 40 A.   It is not yet possible to decide whether
there is a aPngle RMk molecule fallawing the line of the main
protein helix or 35 molecules running alone; coaxial helices of
angle about 45%  If anything, the X-ray evidence favours the
former, though this is obviously aB awkward mode1 from other points
of view.

In my last letter to you X said that there were 46 protein

units in the 69 A period.   I aar now inclined to think that the num-
ber is 49 rather than 46, which makes the xtalacular weight situation
a little easier, thottgh still awkward if the particle weight is a8
high 83 50 mfllian.
earlier suggestions of 31 or 37.

In any case there Is no evidence left for the

The substance which would help more than any other in the

next stage OT the work - the determination of the chain direction
and molecular structure of the RNA - 18 your mercury-substituted
repolymerised p~atein. Unfortunately I was not sucoessful with what
you sent me.   I obtained only one specimen which did not aepolymerise
when orientated and that one was good enough only for qualitative
laeasrrerrents.
substance to spare I should be extremely gratef'ul for them. Xi you
do send me same, would you please specify exactly what buffer
solution should be used with It, as I thi* it miSht be best for me

If you ever have a few mor0 mllllgrarns of thls

-2-

Dr. H. F~aenkel-Conrat.

to re-suspend it and try to orientate It lmediatelg after
centrifhging.  Alternatively, wonld it be better for you to sand
it in ths form of a solution, for me to centrlfige?  (Wlginally
1 asked yon to sand everything In the Form of pellets because I
had no centrlfhgs available, but I have relcently aaquired a

centrifuge 1.

      Having determined the radius on which the Hg lies, and
the raagdtuda of its contribution to the sqnator in Hg-W,  I can
ROW ixse the canparison of TW and Hg-TW to give the phase of the
intensity maxima on the layer-lines of !I%€V.
the same thing far the repolymsrised protein by comparing It with
Hg-proteln I should be in a position, in theory at least, to
determine the phase and magnitude of the RNBL contribution on the
layer-lines iPom a comparison of the TW and protein data,  and
hence to aalculate a Fourier for the RNA. All this would be a
long job, but, I: think, well worth whlle.

IF I were 2ble to da

hSt wishes,

Yours sincerely,

Rosalind Yranklin.