January 30, 1940
Dear Doan,
I have read with the greatest interest your letter regarding projected work with the dye protein and I will be glad to cooperate in any way possible.  It would be quite exciting to follow the events Dr. Sabin has pictured by means of your new micro-movie technique.
I am little worried as to whether it would be possible to detect antibodies on a tissue-culture scale, but if the precipitin reaction should prove too insensitive perhaps complement fixation would do it.
I still have about 50 cc. of the egg album in dye solution left, at a concentration of 2 mg. per cc. and I could spare one-half or two-thirds of it if the initial tests you take should encourage you to go on.  I suppose you would want an alum-precipitated suspension of the type Dr. Sabin used. We still have small quantities of anti-dye serum, too.
Unfortunately the streptococcus dye protein has proved to be a very poor antigen, so that I am afraid it would not be easy to pick up antibodies with it.  I have never tried to agglutinate streptococci in the weak dye antisera, however, and will try this to see if any effect can be noted.
I should be very glad to you and and Dr. Houghton at any time, but it would seem a pity for you to take the long trip just to discuss details which could perhaps be settled by mail as questions arose.
You will find our mark on the dye described in Dr. Sabin's references 44-46 - I'm sorry to say there are no reprints left.
The dye solution contains merthiolate 1:10000 - would that affect tissue cultures adversely? It might be possible to get rid of the merthiolate, but I suspect that once it is added it sticks to the protein.
Looking forward to hearing from you again, and with kindest regards,
Sincerely,
Michael Heidelberger