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Title: Studies in solution adsorption at biological surfaces
Author: McKay, Robert B.
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1963
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The adsorption of non-ionic and ionic solutes from aqueous solution at selected biological surfaces has been investigated by direct and indirect methods. In preliminary experiments, electron complex formation which might operate in the adsorption, has boon investigated; also the "method of continuous variations" with refractive index se the independent variable has been shown to be satisfactory for determine intermolecular-complex formation in binary mixtures of solutes dissolved in hydrogen-bonding and non-bonding solvents. Part I of this thesis is concerned with the adsorption of non ionic solutes on protein substrates. The refractive index method. has been used with dilute aqueous solutions of a variety of simple mono-saccharides and disaccharides many in D- and L-configurations on the one hand, and several proteins, and various model compounds, on the other. The results show that: all pentoses, and also meso-inositol and mannitol appear to react with each protein tested; no disaccharide reacts; hexosos may or may not react, according to the particular, Stereo-isomer used and the nature of the protein. It is suggested that a molecular sieve process is in operation, such that only carbohydrate molecules below a limiting size can penetrate the dissolved protein aggregates and thus forma hydrogen-bend complex. Hexese molecules are near the critical size for entry and whether they combine or not is determined by steric factors. It is also suggested that L-sorbose exists in water, and combites with other solutes, as an aggregate of eight molecules. (v) Part II is concerned with the adsorption of ionic solutes on actual biological cello. The mechanism of adsorption of cationic dyes on dead yeast cells is first investigated. The adsorption is extremely rapid and although it varies with temperature and the concentration of the yeast suspension used, the shapes of the isotherms for each dye are the same under all the conditions used. Formalin-fixed cello have been shown to be a standard substrate in that their adsorption properties appear to be reproducible and remain unaltered over long periods. Adsorption of cationic dye micelles appears to occur in the case of all the dyes with symmetrically charged cations. It is suggested that this micellar adsorption may be important in the mechanism of the Gram stain reaction. Rhodamine B, which is an unsymmetrical dye, appears to be adsorbed as a monolayer of dye cations stacked edge on, and inter-linked by hydrogen bonds; on protein fibres and on graphite however, which were included for comparison, this dye appears to be adsorbed flat-wise. It is therefore suggested that the protein of the yeast cello is not the site of adsorption, but that some other ionic substances, perhaps nucleic acids, are the adsorption sites. This suggestion is supported by results of tests which show the similarity of the adsorption isotherm of Rhodamine B on WA and on yeast. There is a linear relationship between the size of the dye molecule and simple functions of the degree of aggregation at the surface. In fact for three such chemically different materials as chromatographic alumina, graphite and yeast, there appears to be an identical linear relationship. (7i) relationship between the logarithm of the degree of aggregation and the logarithm of the dye cationic weight. The mechanism of the adsorption of the anionic dyes Methyl Blue and Aniline Blue on sections of the testis of the mouse is also investigated. Those dyes, though anionic, have the anomalous ability to stain strongly the basiphil (i.e. cation attracting) chromatin of the spermatogenetic cells, Extraction of the basiphil nucleic acid constituents from the chromatin causes loss of this property, whereas destruction of acidophilia in the protein constituents does not, It has been concluded that the dyes interact with the nucleic) acids. Further, they appear to react with both DNA and RNA in the chromatin, although they show no affinity for the cytoplasm of the exocrine cells in sections of pancreas, which is rich in RNA. The mechanism of the reaction has not been fully elucidated, although the dyes do not behave as basic dyes towards the nucleic acids, and the interaction is non-ionic. It is suggested that interaction involves donation of electrons by the dye molecules to electron-deficient rites in the nucleic acids.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available