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. Author manuscript; available in PMC: 2011 Dec 1.
Published in final edited form as: Cytometry A. 2010 Sep 7;77(12):1113–1125. doi: 10.1002/cyto.a.20964

Figure 4.

Figure 4

Time-resolved luminescence (TRL) detection eliminates short-lifetime fluorescence background signals. Europium beads (200 nm diameter) were deposited on a quartz coverslip and immersed in a 10 μM solution of AlexaFluor™ 350. The specimen was excited with 365 nm light and emission was viewed through a long-pass (>420 nm) filter. (a) In continuous wave, epifluorescence detection mode, the beads cannot be resolved from the fluorescent background. (b) In TRL mode, a short gate delay (Δt = 2 μs) between excitation and detection eliminates background and allows clear visualization of single beads (see Materials and Methods and Table 1 for complete image acquisition parameters). Scale bars, 10 μm.