fictober 15, 1963

Dr. H. P. Baumgartner
President, Liana of Waikiki
1218 Walmanu Street
Honolulu J4, Hawaii

Dear Or. Baumgartner:

i anu very much obliged to you for your helpful letter of September 19.

We had eventually discovered the Neumann publication and had unsuccessfully
searched the literature for any further developments fram his method. |

am very pleased to have heard fron you about your contribution on the use
of coumarin derivatives.

We have considered the coumarins as possible bases for fluorescent detec-
tors, particularly since analogous compounds have been used for the
determination of Begalactosidase. We have found, however, a major advan-
tage In fluors whose absorption peak is well into the visible, since
interference from non-specific fluoreacense of background material fs
greatly reduced and can be a serious problem when ultraviolet excitation
is used.

We have also been attentive to the other problem that you mention, which

is a very rea! one when accurate kinetics are to be determined: the use

of a bl-functional fluor. We have been getting around this by using the
monophosphate of the monomethyl ether of fluorescein as the starting
materfal. The results with these reagents leave very little to be desired
with respect to sensitivity and ease of fitting into an Instrumental system,
with the sole exception of thelr spontaneous hydrolysis. We are scanning

a number of other derivatives related to fluorescein to determine the best
answer to this problem.

As far as | know you are the first author since Neumann to refer to
fluorescein phosphate; nor have | been able to find any further record in
the literature of Neumann's own activity. From the standpolnt of the
general problem of the effectiveness of scientific canmunication, | would
be most interested to hear whether you have any information on this score.

Sincerely yours,

Joshua Lederberg
Professor of Genetics