Abstract
A quasi-elastic light-scattering (QELS) microscope spectrometer was used to study the dynamic properties of the membrane/cytoskeleton of individual human red blood cells (RBCs). QELS is a spectroscopic technique that measures intensity fluctuations of laser light scattered from a sample. The intensity fluctuations were analyzed using power spectra and the intensity autocorrelation function, g(2)(tau), which was approximated with a single exponential. The value of the correlation time, Tcorr, was used for comparing results. Motion of the RBC membrane/cytoskeleton was previously identified as the source of the QELS signal from the RBC (R. B. Tishler and F. D. Carlson, 1987. Biophys. J. 51:993-997), and additional data supporting that conclusion are presented. Similar results were obtained from anucleate mammalian RBCs that have structures similar to that of the human RBC, but not for morphologically distinct, nucleated RBCs. The effect of altering the physical properties of the cytoplasm and the membrane/cytoskeleton was also studied. Osmotically increasing the cytoplasmic viscosity led to significant increases in Tcorr. Increasing the membrane cholesterol content and increasing the intracellular calcium content both led to decreased deformability of the human RBC. In both cases, the modified cells with decreased deformability showed an increase in Tcorr, demonstrating that QELS could measure biochemically induced changes of the membrane/cytoskeleton. Physiological changes were measured in studies of age-separated RBC populations which showed that Tcorr was increased in the older, less deformable cells.