December 4, 1964

Dr. fames D. Watson
Biological Laboratories
Harverd University
Cambridge 38, Mass*

Leon Heppel recently spent some time at Rockefeller with Zindsr.
Upon his return, Zinder gave him a elant of your ribonuclease-
-minus mutant (127?).  Both Leon and I would very much like to
do some experiments with this organism. However, bec8use we did
not obtain the mutant directly from you,  we would firot like to
be sure that our general plans in no way conflict with your own.
If you have any objections to our use of the organism, wuld you
please let us know.

In general, Leon is interested in using the mutant to extenk his
recent studies on enzymes that appear to be active on the surface
of the cell.
-minus mutant MRE-600, which was kindly sent to him by LJade in
England.

In this connection he is also using the ribonuclease-

For my part, I am interested in looking at the activity of the
soluble RNA-specific phosphodie~terase,  in cells that lack the

diesterase nor polynucleotide phosphorylase activity is increased.

"ribosomal" ribonuclease.

Xe already know that in MRE-600 neither

I am enclosing a few pertinent reprints.

With kindest regards,

Sincerely yours,

Maxine Singer

MS : peg
Enclosures