July 11, 1945

Dr, VaaR. Potter
Wrd le bmor ial Labor at my
University of lisomsin
Madison, '3isoom in

Dear Van:

Thankr for YrnZr letter Of JPlp 6.

I how

follaned jrOW adVbe and 11111

now aontposing a letter ard suggeatsd pro3eat ror Dr. Sohc~pl's oonsideration whhh I
hope to get off in she next day or so.  In my letter to Dr, Sahrapn I rtate my Inten-
thns of keeping In re18tiVoly olose oontaot with your group for adviae and  oounrel
part1oularI.y in matters pertalaing to tku3 relations between the results obtained and
the oamer problem.

ph.ofar aa tb aanaer problem is oonaerned  I have in miad to taokle the

follow in^ quertion rhioh lee- to me to be one of the crritioal point8 at  lrauet
Under what mnd it ions oan am of these selfduplioat ing Unit8 erstarblish itself within
the normal eneymatio gopulat ion ?  As you have clearly flsd iaated In your publioationr
it 8ew most probable that aomptitive interaotions play an inportaat role in determi-
ning the trend in enzpatlo oonstitution withln ths oell, I belle- that this queatbn
in its more pneral form 18 aeasnable to more or less dlreot analysis with the available
teohnlquer and material.
the kinetics of the oontpetition betwen two enxynree being fonned simultansouslg in the
8mo aell, Yith ths aid of this kind of data we should be able to provide, 8 reasonably
pregise desurfption of the conditions der whioh (in aertain instames) a partlaular

enzyme Is auooesafZzl in establirhing itself within the oell and pcrhaps of even greater
iaportanoe how to differentially prevent it faom a0 doing.

At the p.rY least I oan hope to delineate wlth relative 018rlty

     In this oonneotion it seems of mofe than passing interest to ermine a aeries
of oaroimgens for theb effeitt not only on siBp@ enlrpe formation but on the dynamios
of the aompet ition between two enxynos which are bein: induoed and followed 8 hrultaneously.
There are in general two ways to favor the formation of a prtiaulsr enzyme: (a) to
ohannel energy and greaursor int its dlreot ion (with substrate or by some other means 18
(b) to differentlafly auppresa the syathetlo aotivitiea of those eaoyae8 with which it
is In aorngetition.  Conaeivably the examination of the efreot of oaroinopns on the
formstion of adaptive ewps oould help us to deolde ahioh a9 ths aborr meohanisms are
involved 8 aarolnogenlo oompouad suooeeds in altering the enzymatic oonsitution 0f
a oell. In an$ oase I think the juestlon is laportant enough to warrant the attempt,

1 would very rnuoh like to talk these experlt~ents over with you in partloular

as concerns the ooangopnds to be seleoted.
Physiologioal Revlem on ensyme variation and its oontrol and would like to include a
SeJtion on your oontributioaai in oonneotion with the aawer quest lon 88 8 problem in
the aontrol of emymatio oonstitutlon. I should also like to talk this over wlth you.

I have hen asked to =It@ a review for

July 11, 1945

It so happens that I matt shortly go up to the Llnirersitg of Mimesot8

am¶ I would lib to drop off in Madlaon on my wag baok if ad when yon would be argard.
1 am also ratfier aruloua to am Br. lveysr about the morphogenesis paper,
8 very kind letter iroa hh expsesshg intereat 8nd the dfmire fc# another diaoussioxle
Wop nie a fine on #hen you will be rvonad azrl I will amango my trip aacordlngly,
By ths way, I would greatly appsleoiate it if you muld inelude the Sawre1 referenoes
rou mentioned in yner lart 1cPttWe

I recreivW

You will reaelre under separate oover a reprint of the energetioa arttale

fiam the, Je Rgaloal Chm.
thousht you mi3ht like  to have it partimlarly sinoe other papers whieh are aoming out
later 858 based on the aa~lysira ooontaind in it.

It probably will not be of too nnrchare to you but  I

Give my reqardo to %e. Fusoh and Zfller. Their recrent paper in Canoer

Reoearah look8 even more exalting in print than tho verbal report  I rsaeintd ahen I
was up your WcnJre

Sinoerely ymrr,

s. sgiegelpan