Fluorescence polarization study of human erythrocyte membranes with 1-phenyl-3-(2-naphthyl)-2-pyrazoline as orientational probe.

The emission and polarization spectra of 1-phenyl-3-(2-naphthyl)-2-pyrazoline (PNP) in various environments were studied. Compared to the widely used orientational membrane probe 1,6-diphenylhexatriene (DPH), PNP is five times less photolabile and since its fluorescence emission maximum is at longer wavelengths (lambda max approximately 445 nm), it is more suitable for use with intact erythrocytes. The limiting fluorescence anisotropy of PNP is 0.385. In erythrocyte ghosts, the steady-state emission anisotropy of PNP is a decreasing formation of wavelength and its temperature dependence parallels that of DPH, dropping from 0.298 at 2 degrees C to 0.185 at 38 degrees C when averaged between 420 and 470 nm.