MEDICAL RESEARCH COUNCIL

Telegrams :

' NATINMED, MILL, LONDON.'

NATIONAL INSTITUTE FOR MEDICAL RESEARCH,

Telephone : MILL HILL 3666. THE RIDGEWAY, MILL HILL,

LONDON, N.W.7.

PRIVY COUNCIL

16th October, 1951.

Dr. 3. Spiegelman,
Department of Bacteriology,
University of Illinois,
362 Noyes Laboratory of Chemistry,
Urbana, Ill.

Dear Spiegelman,

bhy thanks for your letter of' the 1st uctober.

Since writing

to you I have, of course,  seen the recent issue of the €'roc. Hat.
had. Sei. containing your last article.
the information you gave, which is very interesting.
sometime to know if you have any scheme for visualizing how your
discrete particles, which are apparently inherited through the cytoplasm,
actually function in promoting enzyme synthesis.

ivlany thanks also for all

I should like

As far as our own work goes,

ou have presumably seen my last paper

on penicillinase amtation,since 9 sent you a reprint.
followed that up by investigating the absorption of penicillin sulphur
on to the cells, using the same pretreatment technique as for adaptation
experiments, by means of S%labelled penicillin.   ?;e have found that
there is a pretty close correlation between the amount of penicillin
sulphur specifically fixed on the cells and the effect of penicillin in
stimulating subsequent production of penicillinase in a penicillin-free
medium, following pretreatnent at Oo plus thorough washing of cells,
In this particular case at least, there seems to be fairly good evidence
that some sort of specif'ic interaction between penicillin and a specific
penicillin receptor within the cells is first necessary in order for the
cells to adapt to penicillinase formation.  It is interesting that the
amounts of peilicillin sulphur i'irmly fixed on the cells are exceedingly
ye$.3- maximal adaptation effect being achieved af'ter the fixation of dd t':
S per cell.

Do you yet know whether you will be coming to the Biochemical Congress

vie have since

4

in Paris next year?

rii th best wishes,

Yours sincerely,