November 14, 1950
Dear Dave:
As you must know, I was very much interested in the information in your letter.  It begins to look as if the structure of Co A is being clarified rapidly.
I am very disappointed that the preparation we sent you had DPN splitting activity of 900 units/ml.; I am sure it started out at 2700 units/ml. If the phosphatase contaminant in this preparation did not go down in activity--and it probably did not--then it approaches a significant nuisance level.  In our work with TPN splitting, we were careful not to prolong the reaction beyond the time necessary to split TPN.  Or the phosphate liberation was always negligible.
In paper chromatography of adenine nucleotides, ADP can be separated from the mononucleotide (as reported in a recent J. Am. Chem. Soc. by Carter and Cohn), but I cannot tell you what the relative behavior is of the "ADP" of TPN origin.
I would be very happy to have you come down whenever it is convenient. As a formality, it may be desirable for Doctor Lipmann to write a letter to the Director, but I am certain this will involve no difficulty at all.
With best regards to you and Doctor Lipmann from all of us,
Sincerely yours,
Arthur Kornberg