December 8, 1953

Dr. Theodore T. Puck
Department of Medicine
University of Colorado
Denver 7

Golorado

Dear Ted:

In response to your letter of November 24 Esther is preparing
to send you the following strains:

Group 1 ~~ Kl2, lysogenic and “1485, a lambda sensitive mutant
derived directly from it.

Group 2 — In order to furnish a more ccherent group of strains
the genetic ditferences among which may be more confidently expected
to be confined to their status in re. lambda, the following. These
are all prototroph cultures.

W211? lambda sensitive, Lp®
W2115 immne-1, Lp™
W2118 lysogenic, Lp*

W219 Ip,* , Lp,”
W2120 Lp, ® , Ip.” » immne-2
W2121 double immune, Ip,* ’ Lp,”

The detailed comparisons should, we think, be made with the
cultures of Group 2 for the reasons indicated. However, st kKl2
and W1485 have been very widely distributed and the latter is/doubt
some, but not all, of the strain designated ag "s". Some of our
colleagues have been unforgivably sloppy in preserving the strain
mumbers and therefore details as to the pedigrees of the cultures
that they have been using.

As co:erns this sumer, we will be delighted to give careful
and sympathetic consideration to any proposals that you will be
able to make. ‘“e are, however, in the mecntime considering some
alternative plans and you should not, therefore, consider that either
you or we have as yet made any binding commitments. Good luck with
the strains ve are sending.
Page 2 -- Letter to Theo. Puck December 8, 1953

As the result of a casual conversation with one of the bio-
chemists from Du Pont I have received from them a rather large
sample of a polyelectrolight rather similar to the one you refer-
red to in your Cold Spring Harbor mamscript. This one is a di-
gathyi derivative of methacrylic acid but otherwise quite similar
to your compound. If a preliminary experiment indicates that it
works in the same generel way as your material was described to do
I will send you a good part of our own sample and whatevercther
information would be relevant. You will recall that our interest
in this question was concerned with technical rather than funda-
mental aspects.

I do not know whether the reference that I gave you to
alkylating agents as mtagens (during our visit) was very useful.
Subsequently, a rather comprehensive review by Ross has appeared
in the first volume of Advances in Camcer Research, which will be,
I think, of somewhat greater pertinence. :

Yours sincerely,

Joshua Lederberg

/mg