Watson here gave details about his X-ray studies of the structure of RNA (ribonucleic acid), the single-stranded companion
molecule to DNA which is an essential intermediary in protein synthesis. His warning that "it will be a nasty job to prove
existence of 20 specific cavities" in RNA (p.3) was a reference to George Gamow's idea that genes could provide a
direct, physical template for the twenty amino acids that form the polypeptide chains of which proteins are made up.
Item is handwritten.
Number of Image Pages:
4 (816,139 Bytes)
1954-12-11 (December 11, 1954)
Watson, James D.
Original Repository: Wellcome Library for the History and Understanding of Medicine. Francis Harry Compton Crick Papers
Your letter and MS came yesterday. The Plant Virus MS seems quite sensible and to the point. I argue that it should be written
largely to stimulate Plant Virus Research. As to where it should be published: Why not Advances in Virus Research -- a dreadful
affair but nevertheless it will be read by the people we want to convert. While at Woods Hole, Lauffer has asked me to write
a review on virus proteins and I turned him down. However I suspect the other still stands. Its [sic] unlikely that I can
work on the MS in the immediate future as I will soon be flying East -- I leave in a week and beforehand I should prepare
some seminars I'm to give at Harvard, etc. However I shall try to work on it while travelling from place to place.
About protein synthesis -- After initial enthusiasm about DNA we are back to being solid RNATIE CLUB members. Idea was the
following. Take DNA [ . . . ] H bonds and shift one chain down so that it forms [DRAWING] bonds between the ionpleneta[?]
chains. This brings back [DRAWING] of one base near back [DRAWING] of another base [not necessarily complement
[END PAGE ONE]
[BEGIN PAGE TWO]
We thus have a series of holes of 16 band types [more if neighbors count.] However in its disfavor are (1) CH3 can be replaced
by Br -- without serious effects -- this "smells bad" in antigenic work this usually stops cross reactions. (2) A.A.
backbone does not fit in easily 3) since RNA also makes proteins [is this our downfall] it seems miraculous that it can provide
a similar code without using 5 methyl group - th[ . . . ] if both RNA and DNA make protein they must do it by a similar trick
So back to RNA. At first site [sic] this looks just as discouraging as before. However I suspect the answer is staring us
in the face. Import fact about RNA picture is 10 A near meredinoral[?] reflexion. Must mean something periodic at this distance.
Two possible structures [I neglect multi stranded structures -- origin too difficult if non complementarity exists.]
A. [DRAWING] one stranded helix with pitch of = 11 A and contains about 8-10 residues 1 turn. In this model, bases must be
seriously tilted. Bases inside -- PO4 out
B. [DRAWING] one stranded helix with pitch = 4 A and with about 2 1/2 residues 1 turn in this model, bases form two wedges
[END PAGE TWO]
[BEGIN PAGE THREE]
The main point is that when we tilt the bases almost 11 to fibre axis we produce very suitable A.A. cavities. In fact we
can say that if we were to create a [sic] A.A. making beast we should arrange for a pitch of not greater than 11-12 A and
probably not less than 8 A [ if smaller will be very tricky to fit A.A. backbone [ . . . ] So I do not think the x-ray picture
is against us. However it will be a nasty job to prove existance [sic] of 20 specific equities.
I was in Berkeley over the Thanksgiving Holiday. Pleasant but without scientific stimulation. Only complaints about Stanley.
Schachmans [sic] break story does not convince me. If they exist, they must be less than 1 in 500.
Did John Platt write you about transfer twists. I will see him while I 'm in Chicago. He seems to have misread our
articles. I don't think his process really helps the situation
Also, were you invited to Brookhaven for a Mutation Meeting in June '55. I received an invitation which implied that
they hoped originally to ask you but that now that you were back in England, you were no longer available. I could not make
out whether they didn't have funds to ask you from England or whether you turned them down. I'm not anxious to speak
on DNA and the
[END PAGE THREE]
[BEGIN PAGE FOUR]
Mutation process, especially hesitant to write even an abstract on it. So I shall suggest they invite Seymour Benzer to talk
about his phage crossing over data. [I believe Sidney showed you the Benzer MS at Woods Hole.
I am leaving for Chicago on the 20th. Then to Cambridge Mass for 10 days and finally a few days in Washington before flying
back. No need to indicate my desire to return East.
If I learn anything of interest while in East, I'll write you