title: Detection of a phase transition in red cell membranes using positronium as a probe.
abstract: Positron lifetimes in human red cell ghost membranes have been measured as a function of temperature from 3 degrees C to 25 degrees C. A marked sudden change in the ortho-positronium annihilation rate was found at 16-18 degrees C during the heating cycle and at 18-20 degrees C in the cooling cycle. Such sudden change of microenvironment in the membranes sensed by ortho-positronium is attributed to the sudden change of water diffusion rate through the membranes which is a consequence of the sudden change in free volume, or fluidities in the lipid layers.
mesh_terms: D004601:Elementary Particles; D004910:Erythrocyte Membrane / Q000648:ultrastructure*; D004912:Erythrocytes / Q000648:ultrastructure*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D013057:Spectrum Analysis; D013696:Temperature; D014783:Viscosity