March 29, 1949
Dear Arthur:
Please accept my best, if delayed, thanks for the sample of TPN which arrived safely in due course.  I am also glad to have the details of the counter current purification, it looks pretty good.  We are about to make a batch of the 1st acetone precipitate and will try counter current on it.  There is a machine in Chemistry.
We got a copy of Rosenthal's acetoacetic acid method.  Unfortunately, oxalacetic reacts as much as acetoacetic and, for determination of the latter in the presence of the former, the method may require a special study.  However, it will be quite useful for acetoacetic in the absence of interfering substances and I am glad to have it.
There has not been much progress recently in the citrate synthesis.  We found E. coli extracts very active in forming citrate from acetate + ATP + OAA.  There seemed to be a funny catalytic regeneration of ATP which disappeared after rough fractionation with AmSO4 and prolonged dialysis.  In view of this, I am not sure that earlier experiments with extracts indicating synthesis from the product of the phosphoroclastic reaction can be interpreted in that way.  I guess we shall have to isolate (or try to isolate) the "active" acetate formed both by the phosphoroclastic reaction and by acetate + ATP.  Of course we should like to get evidence for the assumed formation of citryl phosphate.  We sent a note to J.B.C. with the results on pigeon liver.
I was very pleased that you found good activity in pig liver for the NMN + ATP --> DPN reaction and I am sure you will be able to demonstrate the participation of pyro-P without too much trouble.
I know exactly how you feel about sitting at a desk all day.  I am in the same boat working on the article for Sumner & Myrback's book.  You should not be too unhappy about it, however, since that gives you a chance to write up your papers.
We shall be seeing each other soon and I look forward to it.  Meanwhile my best to everybody in the lab with our fondest regards to the Kornberg family.
Yours,
Severo Ochoa