Thank you for your letter, the graphs, and the preprint. Before commenting on the results with P1, one word about the preprint.
It seems to me the conclusion about nonrandom messenger formation would be stronger if it could be shown that changes in conditions
during infection do not affect the results. This can be done with T4 mutant am122, which in E. coli B makes no DNA, no phage
proteins, and continues to make early enzymes. Here, the 15' messenger may resemble the 5' messenger. Write or call
if you want the pair of phages (T4 and T4am122).
Re the beautiful data with P1 and P1d1: we would like, in addition to the experiment with nonfractionated RNA, to see also
the values for the negative fractions in the earlier experiment, in order to understand how much significance the peaks on
fractions 1 and 3 have (compared with the maximum of fraction 2).
Now for the other experiments:
1. We are sending more P1 and P1d1 (end of the week), as well as a pair of strains, 2.0S0 and 2.0S0(P1), which are i+z-y+.
Also, 2.0S0 R, a lac+ revertant from 2.0S0, in case you wish to compare pick up of lac messenger in the same experimental
setup. [2.0S0(P1)- R lac+ is easily isolated on EMB lactose agar, if needed.] The system: (P1 + 2.0S0) should provide messenger
of the P1 vegetative variety if infection is done at multiplicity of 1 and at 37 degrees. CaC12, 2.5 x 10^(-3) M, is needed
for adsorption. (Annealing to P1d1 in comparison with P1 might give size of deletion in P1d1.) 2.0S0(P1) as well as [2.0S0(P1)
+ P1] should provide the messenger for immunity.
2. The uninduced E. coli B should make messenger i+. Any label picked up by P1d1 here should give an upper estimate of i+
3. You may not have been aware that the phage P1d1 60 i- that you have used carries i-z+y(del) (reason: it is the highest
yielder of transducing phage). Of course, one would like to know the size of the messenger picked up by z+ DNA and compare
it with the size of that picked up by z+y+ DNA, in order to find out if "one operon -- one messenger" holds. There
seem to be 2 approaches:
a) If you can separate the RNA from DNA after the pickup, you may measure in a sucrose gradient the size of the messengers
picked up by P1d1 z+y+. This is the most direct way. (Reannealing the messenger with different DNA's (different deletions)
may also give the answer).
b) If (a) is not feasible, then one may try to get an answer by cross-annealing messengers z+y(del) and z+y+ with the two
corresponding P1d1 DNA's in all combinations. (There is always the uncertainty of the effects of nonhomologous regions
attached to RNA or DNA on the efficiency of pick-up). At any rate, we will also send you, a bacterium lac(del)(P1d1 z+y(del)),
as a source of messenger, and (later) a phage which is P1d1 z+y+ as an alternate source of DNA.
4. Homology. There is good evidence of poor pairing between the lac region of E. coli and that of Shigella. The enzymes
differ in many respects and at many genetic sites. It would be nice to compare the pickup of coli messenger by the DNA of
P1d1 Sh with that by P1d1 coli; quantitation will probably be difficult, but one possible result is -- no pickup at all.
We shall soon send you also this phage, P1d1Sh, in good amount.
5. What are the chances of doing kinetic analysis with the pickup system? Does DNA have to be always in excess, or can one
try to saturate it with excess messenger, then see how much RNA is picked up by how much DNA, and calculate the relative size
of lac and P1-lac)?
These are some of the thoughts we got in the "excited state" produced by your results. Let us know the answers.
Naomi would like to come to Urbana for several days and see the whole procedure in action. Please let us know if and when
it would be convenient. She could bring bacterial stocks and more phage.