FIGURE 6 |.

Results from an infrared fluorescent protein study (iRFP). Left, top: An iRFP with an emission maximum of 682 nm expressed a fluorescence lifetime value of 0.95 ± 0.08 ns. Right, top: An iRFP with an emission maximum of 713 nm expressed a fluorescence lifetime value of 0.65 ± 0.07 ns. Bottom, left: Dot-plot illustrating fluorescence vs. side-scatter for both the iRFP populations. Conventional fluorescence-activated cell sorting applies population gating to sort and enrich populations of interest. Significant overlap would inhibit users from achieving high sort yields. Authors from Yang et al. [62] applied time-resolved sorting to achieve maximum sort yields. Time-resolved data is processed by a fast Fourier transform and is transposed to frequency spectrums. Direct current and modulating frequencies are identified to calculate the phase value on a per-event basis. The subtle differences with respect to phase values between the two iRFPs illustrate two distinctive populations that permit sorting. Figure adapted with permission from The Optical Society ® [62].