Programme of Research, 1954

I,.   X-ray diffraction studies of viruses

  Since the classical studies of Eernal and Fankuchen on the X-ray diffract ii n of
tobacco mosaid virus ("NV), muck progress has been made in the techniques of intergreting
comslicated diffracfmon patterns, and the ideas of micro-biologists concerning the structure
of the simpler viruses have d-veloped considerably.

which cnn be obtained in a well-orientated form.

associated wit`n varying amounts of water has already been start&.

remains unchanged.

It therefore seems that the time has

come to undertake a new investigation, by X-i.ay diffract:on, of those viruses such as TMV

A suitable X-ray camera for this purpose h:s been constructed, and work on TIN specimens

water is added to dry T$V, the greater part of the high-angle diffraction pattern

There are, however, important changes in tit part of toe diagram

corresponding to spacings of about 20 g.  It is hopd that a quantitative study of these
differences will give some idea of the location, in the virus particle, of that part of the
water most closely associate4 with it, and will thus define the boundaries of some of the
structural components of tie virus,

  itiith the aid of a special low-angle camera (which has been designed and made in this
laboratory) measurements will be made of the positions and int .nsities of equatorial reflections.
These are related to the i&m-particle distances, and their positions can therefore be varied

                   In this way it ehould be possible tl  masure a large
number of equatorial reflections, and to measure their structure-amLlitudes and signs in a
manner similar to tnat used by Perutz in his studies of haemoglobin.   A Pousier transform
would then give a circularly averaged projection of t`le x-d density, ard thus shoL-ld allow a
decision to be mad as to whether or not the ribonucleic acid lies at the core of the rod-
like particle (as bas been suggested by several authors).

heavy core - that is, that the RNA lies near the centre.
on TEV of varying water content suggest that the particle contain a structural component

points, it should be possible to procee5 to a more general interpretation of the X-ray
diagram as a whole.
of the type of diagrm-2.e pmduced by molecules of helical symmetry.

by varying the water content.

Preliminary qualitative observations iaaicate that the rod-like particles do have a

Similarly, pxeliminary observations

having at least one dimension of about 20 8.

Following a more precise study of these two

This diagramme show several hundred reflections, and is characteristic

  A furWer aid to the interpretation of the X-ray diffraction diagraannes may also be
provided by the possibility of staining the virus particles with phospho-tungstic acid.

free fragments which are always found associated with preparations of TPlV.

Later we hope to be able to study other rod- shape@ viruses, and, also, the smaller RNA-

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PROPOSED X-RAY DIFFFiACTION S'NDY OF SOLUTIONS OF POLY-ELECTRO-

-LYTES.

The high charge density of synthetic polyelectrolytes

causes etrong electrostatic interactions in solutions of these

substances, and brings into Prominence many of the phenomena
which are observed,to a lesser degree, in solutions of proteins
and other naturally occurring large molecules,
it is believed that long-chain polyelectrolyte molecules form
spontaneously a partially ordered system even in relatively
dilute solution - an effect similar to that observed by Bernal
and others for tobacco mosaic virus.

In partiwlar,

  The behaviour of polyacrylic acld in solution has been
extensively studied by Kachalsky and his co-workerg,  and it
is now proposed to study derivatives of this substance by
means of X-ray diffraction,
acrylic acid and the sodium salt of poly+ -bromo-acrylic acid
will be prepared in Prof. Kachalskyts laboratory for this work.
We shall thus be provided with eoluh,ons of polyacrylic deriva-
tives containing either a heavy cation p~ a heavy anion, and it
will therefore be possible to study separately, by X-ray dif-
fraction, both the ordering of the actions and the ordering of
the anions in solution,

Both the caesium salt of poly-

  For this ptlrpose it is proposed to use a Gulnier-tae
X-ray camera (with bent quartz monochromator) specially designed
for use with liquids.
liquid can be examined either in the static state or in flow,

The camera design is such that the

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and at any accurately controlled temperature between 0' and

10OoC.

with hydrogen to eliminate scat'iering of X-rays by air.

The body of the camera can be evacuated or filled

It is hoped that a study of the structure of solutions

of synthetic polyelectrolytes will lead to a better under-
standing of the behaviour of the more complicated, biologically
inportant, polymer solutions,