Principles of fluorescence polarization measurements.

Fluorescence polarization measurements using high-speed single-cell flow cytometry have found increasing use in cellular biology. In most flow systems, the detection axis generally is aligned orthogonally to the direction of flow and the excitation axis, and asymmetric apertures along the excitation and emission axes by cylindrical lenses and/or nonplanar transition between optical indices complicate the numerical correction of systematic depolarization effects. In addition, recent studies on fluorescence emission of structured particles have shown remarkable anisotropies of polarized fluorescence emission dependent on the direction of the detection axis.