Electron Transfer Across Liquid Membranes

Anderson, Stephen (1976) Electron Transfer Across Liquid Membranes. PhD thesis, University of Glasgow.

Abstract

The creation of chemically well-defined electron-transfer membranes was the overall objective of the research undertaken. Each membrane would form an intermediate phase between a primary aqueous reductant and a reducible aqueous substrate and would mediate electron transfer between the aqueous phases without allowing them to come into physical contact. Such membranes could be of a solid or liquid nature. Preliminary research, however, showed that liquid membranes, composed of an inert solvent in which redox active carrier molecules were dissolved, had the greatest potential for development. The existence of carrier transport in biological membranes is now well established and, indeed, the final membrane systems, evolved in these studies, employed the naturally occurring quinone vitamin K1 as the electron (and proton) carrier. A hydrocarbon, normally hexane, was used as the inert membrane solvent. A series of investigative studies were carried out to determine which aqueous reductants and oxidants could be used in these redox systems. Control experiments were conducted to ensure that those compounds, found to react with vitamin K, were totally membrane insoluble. In addition, similar control experiments were undertaken to verify that the carrier was completely immiscible in water. Only if both the carrier and the aqueous reagents were immiscible in the adjacent phase could reaction be considered as occurring solely by carrier mediation. Once suitable redox membrane systems were established, the kinetics of electron transfer could then be investigated. The kinetics of reduction of a number of common oxidation-reduction indicators were first studied. Subsequently the heme protein, cytochrome c, was used as the substrate. The electron-transfer membranes developed here operate by a carrier mechanism which is conceptually similar to those postulated for biological processes. In consequence the experiments conducted, using the membrane systems developed during the course of this research, can be regarded as modelling these natural processes. Certain biological reductants and reducible substrates, that are components of the mitochondrial respiratory chain, were incorporated into the synthetic redox membrane systems and the degree to which these membranes acted as viable models for biological systems has been assessed. The validity of these systems as biological models would be further enhanced if the membranes could be reduced to the thickness of biological membranes. Although redox reactions across a membrane of bilayer dimensions has not been attempted, electron transfer across a thin 'lens' membrane has been demonstrated. Even though the redox systems developed used a naturally occurring carrier, a number of non-biological uses for such systems has been demonstrated. These systems provide new sensitive methods for the preparation and characterisation of solutions of reduced or oxygen-sensitive compounds, without the added complication of chemical contamination (other than protons required to ensure electro neutrality).

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Physical chemistry
• Date of Award: 1976
• Depositing User: Enlighten Team
• Unique ID: glathesis:1976-78741
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 30 Jan 2020 14:57
• Last Modified: 30 Jan 2020 14:57
• URI: https://theses.gla.ac.uk/id/eprint/78741