Dear 4d,

The one culture of Y-53 that I have on hand will be sampled and sent
to you today. I have frequently had trouble scoring the threonine require-
ment in the presence of leucine. Possibly leucine 1g contaminated 4% pro~
vides sons sort of threonine preocursérs.

April 22 4s fine for the dissertation. We will probably ride
up from New York that morning, go can you set on a time that won t be too
early. -lso, can you give ne a line on the active participants?

No word from Boivin of any kind since list suiner's meetings. It is hard
to believe there is not something wrong somewhere. No further work on
transfcrmation pending strains, etc.

Have kxwiackect extracted an enz;me preparution frou lactose K~12 & derive.
which splits lactose (in absence of phosphate) to monosacchkride components
(i.e. to material reducing Cuacetate in acetic acid) The enzyme is resistant
to asetone precipitation, and comes out with i —j + ammonium sulfate. There
haa been some variation in the anount of activity in different autolysates,
but I think this was due to pH drift. Accding to literature, the enzyme in vitro
is fairly rapidly denatured at pH 5. The work uheud would seen to bes
L) to define presence or absence of enzyme in the several mutants,

2) tq make a definite chemical characterization of the products, and
3) to determine us far as possible whethhr a singie reaction is invoived,
The activity of the wutolysates, and response to dilution, is already
auch as to suggest there is only one enzyme, and Monod working on the same
probles sarites thut it cannot be extructed frou Leo-j{mitants or from Lae¢
not adapted to lactose,
(w340 )

Found a temperature stant last week. at 45° it has thé same phenotype as
Wel02 , t.0. Lac~,Hed~,Glue but Gaifgivconie/. However, it fervents all these

ars at 36°. If celle are grown on lactose at 36°, washed, and incubated at
45°, they rapidiy ferment lactose at this temperature, suggesting that in the
temperature mutant it is not a question of a temperature-sensitive enzyne
but a temperature effect on the formation of the enzyme. Am looking for others
withg perhzps, mutations at other loci. No data yet on allelism of 108 with 340.

Wild type (Lac¢) coli will not attack neolactose (2,3 epilactcse, or altrose~
b-fl-galactoside. However, 16 readily papillates and yield neolactose/ mitants.
These mutants still attack lactose so it is not q question of qualitatively
shifting the lactose specificity but of "generalizing" it. It whll be interesting
to see whether there are any finer effects on the lactase-iactose affinity
constants sequential. to this alteratiog/

As you can see, this work on gene~enzyme yelationship in coli is not bwing
held up by lack of any biological material, but by the rate at which I can
analyse it. For purely technical reasons, I think coli is more suitable
than Neurospora for the study. However, for all of our work, genes in
coli don't have the sare respectability as those of Neurospora. When we
see each other, I'd like to talk over with you prospects of trying to ex-
tend or duplicate this work on carbohydrases to Neurospora(or possibly to
yeast). Are you or Davendoing anything along these lines now? Anyhow,
both Esther and I fsel almost a little nostalgic for that beautiful mold,
and in any case I want to be sure that any students we have coming out of
here know how to handle it.

The stud-nt situation is a difficult one. I thought to have had a very
BO prospect lined up (ganey Harting) but she decided instead to work with
Cori. There is an #1100 fellowship vacant, but I'd rather turn it back in
to ‘ARF than apply it thi the typical .... that forms 95% of the apolications
to gamk graduate school. I expect that you must be looking yourself to °
augment your personnel. Well that's something else to talk sbcut next week or
so. Till then,