January 25, 1971
Dear David:
I do have some E. coli B restriction enzyme on hand and would be glad to send you some. I don't know the best way to send it, however. It is kept at 0 degrees and is rather stable under these conditions. I will try adding glycerol and storing it in dry ice. If the enzyme survives, I shall send some to you this way.
With best regards,
Sincerely,
Daniel Nathans