NEW YORK UNIVERSITY
COLLEGE OF MEDICINE
(UNIVERSITY AND BELLEVUE HOSPITAL MEDICAL COLLEGE)
477 FIRST AVENUE, NEW YORK 16, N. Y.

DEPARTMENT OF MEDICINE TELEPHONE ASHLAND 4-1800

YVetober 20, 1947

Dr. Joshua +ederberg

Devt. of Genetics

College of Agriculture

The University of Wisconsin
Madison 6, Wisconsin

Dear Lederberg:

It was nice to hear about your present fine appointment. I think
it is a real achievement, and cne you well deserve. I have heard of and
seen referer.ces to the work you did sith Tatum, but being unfamiliar
with the field am ignorant of the details. I would apvreciate your
sending any reprints you may have.

Regarding your specific question about the yeast, it is true that
during August I, and a fourth year medical student repeated and confirmed
the work of Fox and Ward, but the work stopped after only 4-5 weeks when
a shipment of radioisotopes arrived (for my major project). However,

I think we will start again in about a month, and will try to establish
the optimal conditions for producing these precipitins and meke also

an effort to study the quantitative aspects of the precipitin system.
One difficulty which we encountered and have been unable to circumyewt
is the fact that the yeast extrects ere various shades of brown and the
crecipitates that form when they «re mixed with the approvriete entigen
are colored. Since we heve been using UV absorption (on the Beckman
spectrophotometer) to quantitatively measure srecipitetes, and getting
absorption srectre to get information on the constituents of rpts. the
presence of color has been a real handican--and the ebsorption spectra
so far obtained have been utterly uninformative. Perha=s you know

what causes the color end what we can do to remove it. I haven't gone
to the literature, but 1 can tell you that so far everything which has
absorbed color has also absorbed the "antibody"(e.g. charcoal, febtter-
cel, etc.).

m

As you so well know the implications of such a system are truly
far-reeching and 1 am anxious to return to the proklem. However, my
major concern is, and will continve to be, studies in protein metab-
olism, varticularly es related to immuno - chemistry end we have
just completed our first big goal which was to find a methed for
preparing a protein (entiger:) labelled with a redioective tracer in
such a way as not to impsir the protein's immunologic srecificity.
The use of this method promises to be highly interesting.

Incidentally, rej, arding the use of my name in your review--it
seems to me thet even without confirmetion Fex and Ward's work might
be mentioned. If you feel tetter about including confirmetory work,
I think it alright to mertion me. However, since the work wes done
in collaboration with Levin, and, in a sense, «lso with A. &. Keston

(of the Chemistry Dept. at N.Y.U.) with whom 1 am collaborating in

the rest of my work, I think it proper to use ell nemes or, vreferebly,
none et all. If you mst use our nemes + suzpose you might sey comething
to the effect: ".... substentially confirmed by Eisen, Levin and
Keston(priv. comm. )."

Let me know how your work goes end if you vlan on doing anything
with yeast antibodies, 4+ would ampreciate learning cebout medie, etc.
that you decide to use. We are quite ignorant ebout growing, extrect-
ing, fungi end yeest end in the little work we hsve so far done, we
have used only 15-20% molasses as the medium (see Fox end Ward),

With best wishes,

Sincerely yours,

Nor rer

HNE:GEE Herman Eisen