PuRDUE UNIVERSITY (aor BIOPHYSICAL LABORATORY LAFAYETTE, INDIANA July 29, 1956 Dear Joshua, I would like to back out of the arrangement we made for running P32 transfer experiments at Madison, for several reasons. I talked to Cy Levinthal about his emulsion technique and he succeeded in convincing me that you have to marry the technique and devote at least a few weeks to mastering it. Geofery Brown from London who has been using emulsions concurred. Algo I now tnink that the data I am particularly interested in, for correlating P32 and genetic transfer, would be more readily obtained from angexneriment in which the mating cells are biénded at various times and the labeled Hfr parent gatack destroyed by lysing with phage. The P32 transferred to F- cells can then be counted directly . And it may well be that this problem will soon be solved by Jacob and Fuerst via their P32 decay experiments. And finally I don't think I would be of much use to you. Walter Plaut is willing to handle the P32 end of the experiment and you of course will take care of the micro- manipulation, So I should be dispensable. I think your experiment is an important one and I hope you succeed. The main obstacle probably will be the emu&sion technique and it may be that either Cy or Charlie Thomas will be willing to work with you on it. They sounded interested, The information on where to get the proper P32 is as follows. First request a permit from the U.S.A.E.C. to order it from England and then order carrier- free P32 highest specific activity. A 20 millicurie shipment should be sufficient to start. The address is the Atomic Energy Establishment, Harwell, England. The cost is about $30 including shipping charges. lew ¢ >. =e vy veratd ~fo jor Few (>) bee yal Jowrd "5 I bwe Regards to Esther and Connie, wee td “ye _ TT Ne ( a lee s Joo bux ol rhe phy t v) ou