We have investigated the influence of the polarization direction of excitation light on DNA sizing results obtained by a flow cytometric technique. We found strong fluorescence anisotropy of the fluorescent signal from λ DNA stained with the bis-intercalating dye TOTO-1. Small fragments of DNA are less sensitive to polarization than larger pieces. This effect is more pronounced at faster flow speeds. These observations show a noticeable orientation of the DNA molecules introduced by the shear forces in the flow system. The data are consistent with an angle between the transition moment of fluorescence of TOTO-1, and the long axis of DNA is approximately 62°.
© 1999 Optical Society of America
(160.1190) Materials : Anisotropic optical materials
(260.2510) Physical optics : Fluorescence
(260.5430) Physical optics : Polarization
(280.2490) Remote sensing and sensors : Flow diagnostics
Alexandra Agronskaia, Juleon M. Schins, Bart G. de Grooth, and Jan Greve, "Polarization Effects in Flow Cytometric DNA Sizing," Appl. Opt. 38, 714-719 (1999)