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Title: The amino acid composition of basic proteins of the cell nucleus
Author: Purves, D.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1953
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Abstract:
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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.660814  DOI: Not available
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