Fig. 3: FCS measurements on Alexa 488 coupled to an antibody.
From: Confocal-based fluorescence fluctuation spectroscopy with a SPAD array detector
a Average PCR for each pixel of the SPAD array detector. The percentages indicate the relative photon flux with respect to the central pixel. Pixel 1 is known as a hot pixel (see the SI for more details) and was not included in the analysis unless mentioned otherwise. b ACFs from I12 (cropped at 7.5 µs) and Isum3×3 and Isum5×5 (both cropped at 15 µs) in blue, orange, and green, respectively. c Diffusion time as a function of the square of the lateral PSF waist for the three configurations (same colour code as panel b). The error bars are standard deviations over four measurements. For I12 and Isum3×3, the error bars are too small to be visible. The data point represented by the black diamond shows, for comparison reasons, the results of Isum5x5 with all pixels included. The red triangle data point is derived from a chequerboard pattern cross-correlation analysis; see panel d. Line plot: linear fit of the three data points I12, Isum3×3, and Isum5×5. d Example of a chequerboard pattern cross-correlation. The data were cropped at τ = 2.5 µs. e Same ACFs as in b but showing the after-pulse component at short lag times. A power law factor A. τB with B = 1.103 and A as a fit parameter was included in the model to account for detector after-pulsing. The τD values in all panels were averaged over four FCS measurements of 200 s each
