ABSTRACT
This chapter illustrates the major nuclear magnetic resonance methods that are suitable for water permeability studies in suspensions of intact subcellular organelles. Water permeability measurements in microscopic, osmotically enclosed systems date from the 1950s, but accurate measurements first became possible in the mid-1960s with the development of rapid mixing techniques using tritiated water. In suspensions of organelles, water transport is normally in the fast-exchange region, where external doping is inappropriate. The water permeability of the chromaffin granule membrane has been studied in detail using spin-lattice relaxation techniques. A second natural organelle that has been subjected to water permeability studies is the thylakoid membrane of chloroplasts. The water permeability of the thylakoid membrane has been investigated using T2 measurements, both in high resolution studies. The two-site methods have successfully been used to monitor the chemical exchange reactions in which water is transported across the membranes of isolated biological organelles.
