19F NMR of erythrocytes: 'split peak' phenomenon, membrane potential and membrane transport

Abstract

The general phenomenon of the transmembr ane 19F NMR chemical shift difference that arises with a number of fluorinated solutes when they are added to erythrocyte suspensions, erythrocyte ghosts and lipid vesicles has been explored. Chapter 1 gives a general introductio n to NMR phenomena, erythrocyte membrane electrochem ical potential, and erythrocyt e-membrane transport of anions and monocarboxy lates. A discussion of NMR-based methods for measuring membrane transport in included. General materials and methods that are used throughout the thesis are given in Chapter 2. Chapter 3 introduces the phenomenon of transmembrane chemical-shift difference of 19F and 31P NMR resonances from solutes added to erythrocyte suspensions. In Chapter 4, there is a detailed discussion of the principal physical basis for the 'split peak' phenomenon . This phenomeno n was used to determine the electrochem ical equilibrium distribution of difluoropho sphate, a fluorinated analogue of orthophosph ate, in erythrocyte suspensions. Chapter 5 describes the measurement of erythrocyte membrane potential from estimates of the equilibrium distribution of difluorophosphate. Chapter 6 deals with the study of rapid exchange of difluorophosphate across erythrocyte membranes, by using a novel approach that only measures the magnetisation exchange between the transmembrane solute-populations, and not between the population components of the 31F split doublet. This was achieved by simultaneously perturbing the doublet components of the solute of cis compartment . In Chapter 7, the various pathways involved in the transport of trifluoroacet ate across the human erythrocyte membrane are discussed. Chapter 8 has a description of 9Be and 19P NMR studies of the multiple equilibrium between beryllofluoride complexes in aqueous media, and their uptake by human erythrocytes . A general discussion of the work presented, and the future directions of research, are given in Chapter 9.