UNIVERSITY of PENNSYLVANIA

PHILADELPHIA 4

The School of Medicine

DEPARTMENT OF MICROBIOLOGY

January 9, 1958.

Dr. Joshua Lederberg
Genetics Building

The University of Wisconsin
Madison 6, Wisconsin

Dear Josh:

We have done very little more with, the B/L, twp inhibitors
and have no plans tor a concentrated pursuafg¢of the problem. We
managed to get a partial isolation on paper chromatograms and Tom
Bird was planning to follow up on its characterization after he left
here. He is now in Youman's department at Northwestern and my last
contact with him indicated that his interests have shifted. About
90% of our information is contained in the published paper. We have
made no studies on reversal of the inhibition. The use of trypto-
phane would be particularly ticklish since this would support growth,
though it could be tested after penicillinase treatment.

Please feel free to follow any leads which you may find,
including isolation and characterization of the inhibitor. The prob-
lem is in public domain.

I note that you will be at Haverford on March 12th. Is

your schedule flexible enough to let me take you to lunch or dinner?
At any rate, I plan to attend your lecture and will see you then.

Sincerely,

—_—

JSG: jlh =< oseph S. Gots