UNIVERSITY INSTITUTE OF MICROBIOLOGY
@STER FARIMAGSGADE 2A - COPENHAGEN - DENMARK

August 5, 1960.

Dr.Joshua Lederberg

Department of Genetics

Stanford University Medical Center
Palo Alto - California

Dear Dr.Lederberg,

Forgive my answering your letter by return mail
which I rarely ever do, but since we are leaving to return
home in a few weeks I might never get to it otherwise.

My interest in the orientation of cells stemmed
from an attempt to find a non-destructive method for se-
parating ribosomes and it seemed that there might be a
sufficient induced dipole moment. It turns out that this
is probably not so, but in starting to work I made some
explorations with whole bacterial cells (E.coli).

Whole cells do indeed have a large inducible dipote
moment and will orient in A.C.fields up to several mega-
cydes. In my experience it was necessary to use well
‘washed cells suspended in water of low conductivity. Addi-
tion of small amounts of salt or even poor grade distilled
water wiped out the effect. As I remember it, a washed
TCA precipitated cells would orient, so the state of the
cells is not too important.

The effect can be most easily observed under a
microscope between @ parallel small wires. The cells com-
pletely orient at low fields and then form chains along
the lines of force (like iron rélings in a magnetic field).
In the strongly inhomogenbus fields near a sharp point the
cells will move quite rapidly and be effectively collected.

This observation led me to suggest the method to
the people at Camp Detrick and they may have explored it
further. I don't remember the names but if you are still
interested I might try to put you in touch with them on my
return.

I know of no respectable publications and did not
publish myself since I lost interest before getting Ll evi-

dence on the mechanism.
5.8.1960. 2.

The effect of very dilute salts suggests that
surface charges are involved but might also be interpreted
in terms of a low internal conductivity. This question
could probably be resolved by increasing the external con-
ductivity with a non-penetrating polyelectrolyte. Accord-
ing to the second picture the dipole moment would disappear
when the conductivity was matched and reappear again at
excess external conductivity, giving by the way), a measure of
the cells effective conductivity.

I also made a few measurements of the degree of
orientation by means of light scattered at hee, Measuring
the field strength for a given degree of orientationyit
looked as if there was a critical fFréquency cerresponding
to objects the size of ribosomes but this could have been
due to monkey~business in signal generator ete. From my
point of view it did not appear that it would pay to put
time in beyond a guidk exploration so I gave it up completely.

I hope this may be of some help to you and your
graduate student.

Sincerely ‘yours,

R ritten