May 8, 1951
Dear Arthur:
We are getting set to try our hand at following your procedure for the preparation of Zwischenferment.  When you sent me some of your preparation some months ago, you indicated that you would be glad to send us the starting material for the enzyme preparation.  I wonder what you had in mind.  If it was the Anheuser-Busch yeast, wouldn't it be possible for us to get it directly without troubling you?  In reading through the procedure I notice that aged calcium phosphate gel is used at one point.  I wonder whether you have enough of it to spare.  We would like to avoid having to wait a couple of months or more for the aging of the gel.  We would be glad to send you some of our gel, in return, when it is aged.
I wonder, too, if you could send us the details of the method you use for preparing C2 and calcium phosphate gels.
Finally, I would appreciate learning your opinion of the TPN which Sigma is currently preparing.  Do you know if it's pure enough to use in your assay method for ATP?
I am sorry to impose on you so greatly.  I certainly will be indebted to you for the assistance you are able to give us.
With best regards,
Sincerely yours,
Alex B. Novikoff