BRITISH EMPIRE CANCER CAMPAIGN
RESEARCH UNIT IN RADIOBIOLOGY


             Director :
          Dr. L. H. GRAY
      B.E.C.C. Nuffield Research Fellow

MOUNT VERNON HOSPITAL

AND THE RADIUM INSTITUTE

NORTHWOOD, MIDDLESEX

Telephone : Northwood 3281

25th February 1957

Miss R. Franklin,
B irk beck Co lle ge C ry st allo graphy Labo rat o ry ,
21 Torrington Square,
London, W.C .l.

Dear Miss Franklin,

    Thank you for your letter of February 22nd, from which
1 understand that you observe a deterioration in the crystal
structure after a single exposure delirrering not more than
100 r. to the crystal. It surprises me very much that you should
observe any change at all after so small a dose - in fact such an
observation would be of great radiobiological interest. Changes
are usually first observed for doses which are  several orders of
magnitude greater.
for example, estimated that a marked loss of crystallinity in wet
collagen fibres resulted from exposure of fibres to  the order of a
million roentgens, and dry fibres were appreciably more resistant.
A virus is, of course, entirely different chemically but it is a basic
fact that a dose of 1 r only produces between 1 and 2 ionisations  in
each cubic micron of material of unit density, from which you will be
able to make your own estimate of the number of defects which a dose
of 100 r would be able to produce in your virus molecule. Kay be your
methods arecapable of picking up very minute changes in crystal
structure.

Perron and Wright (Nature, Lond. 166 (1950) 863)

You would almost certainly produce less change by irradiating
                               In any
                                I think you

                         If it is permissable

the virus dry, but presumably this is of no interest to you.
case the factor of difference might not be a large one.
are on the right lines in trying the effect of irradiating in an
atmosphere of nitrogen and at low temperature.
to treat your virus with a low concentration of the amino acid cysteine
before irradiation in nitrogen, you might find this a little more
effective than simply placing the virus in an atmosphere of nitrogen.

I suppose it is not possible that the virus is being influenced

by ozone or oxidesof nitrogen formed in the air in its immediate
vicinity during long exposures.

I think these are the only thoughts which occur to me at the

present time. I should, however, be interested to discuss further

/over

-2-

Contd.

-

with you any phenomena which you establish as a result of
exposure of the virus to doses in the neighbourhood of 100 r.

4

Yours sincerely,

_._' ,

LHG~AC

Dr. L. H. Gray.