Although genetics deals with rather superficial
characteristics, such as eye colour and skin colour,
it does not follow that only such characteristics
come under chromosomal control. Because of the
difficulty of crossing individuals from different
species, genetical evidence is largely derived from
studies of superficial character variations within
particular species, and cannot, therefore, be
expected to throw much light on the more fundamental
aspects of cell function. However, in any biochemical
interpretation of genetical control of even
superficial cellular characteristics, one could
not avoid associating the part played by the genes
in controlling these with the control of the wider
aspects of cell function. Moreover, the number of
characteristics now known to come under genetical
control is so large that it seems evident that the
only reason why genetical control of fundamental
aspects of cell function has not been demonstrated
is that genetical studies suffer from the inherent
limitations already mentioned.Since the publication of the Stedmans' hypothesis,
Dr Stedman and Mr H. Cruft, working in this laboratory,
have found that the main histones for which species
and cell specificity had been demonstrated, actually
consist of two components, distinguishable by
different mobilities during electrophoresis.
Generally, each main histone has been found to
consist of a major component, and a minor component
possessing a slower mobility, and these have been
designated the 'main component' and the 'slow
component' respectively. An account of this work
has yet to be published.It seemed possible that this discovery might
obscure the significance of the Stedmans' demonstration
of species and cell specificity since this had been
based on analyses of unfractionated main histones.
For example, it could be argued that the differences
in amino acid composition observed were due to the
presence of different proportions of the two
component histones in the different kinds of cell
nuclei studied. Thus it became necessary to fractionate
several of the main histones into two electrophoretically
homogeneous components and to carry out analyses of
the pure components with a view to confirming the
evidence of cell and species specificity presented
in the Stedmans' (1951) publication. In view of the
fact that the scope of the Stedmans' analyses was
rather limited, the only amino acids estimated
quantitatively being arginine and tyrosine, it was
also considered necessary to use a method of analysis
covering a lamer number of amino acids. This
thesis is an account of the development of such a method
and its application to the analysis of histones.The work falls naturally into several sections.
MacPherson (1946) published details of a method of
analysis of the three basic amino acids involving
the separation of the basic fraction from whole
protein hydrolysates as a preliminary step. The
recoveries hes quoted were so good that it was
decided to examine this method to see if it could
be satisfactorily applied to the analysis of histones.
The first section of this work is thus an account
of experiments which were carried out using
MacPherson's technique in a slightly modified form.
It was concluded, as a result of these experiments,
that MacPherson's electrodialysis technique was
unsuitable for the author's purposes.The subsequent section deals with the development
of a method of analysis which is similar to
IVacPherson's method in that the basic fraction is
separated from the whole hydrolysate preliminary to
the estimation of the basic amino acids. But it
differs from this method in the important respect
that an ion exchange resin, Amberlite IRC -50, is
used for the separation of the basic fraction.
MacPherson's actual analytical methods have been
retained with minor modifications.In Section III there is an account of the
application of the method to the analysis of histones.
1 Since the main purpose of the work is the confirmation
of the phenomena of the species specificity and cel
specificity " i of histones for e lectro p izoretícall y
homogeneous histone components, results for the
analyses of the main component histones from different
types of cells from two different species are
presented. In addition, results of a number of
analyses of unfractionated main histones, slow
component histones, and the protamines salmine
and clupeine, have bees. given.Since the scope of the analytical method . developed is still rather limited, some work has
been carried out with a view to extending it to
include the acidic amino acids. The final section
has therefore been devoted to describing a few
experiments which were designed to separate the
acidic amino acids from composite amino acid
solutions using the anion exchanger, Amberlite
IR-4B
