Abstract
Perylene and 8-anilino-1-naphthalene sulphonic acid are hydrophobic probes which fluoresce brightly when bound to regions in the cell membrane. The distribution of fluorescent intensities per cell is measured using a rapid flow fluorimeter with a high power laser exciting light. The authors have modified this apparatus to measure also narrow angle light scattering from cells. The scattered light pulses can be used to open a gate to pass fluorescent pulses. This eliminates most of the noise in the system, permitting measurement of fluorescent intensities of faintly fluorescent cell populations. Cell size distributions can also be determined by the scattered light pulses.