1. Quantification of Fluorophore Copy Number from Intrinsic Fluctuations during Fluorescence Photobleaching 
Chitra R. Nayak, Andrew D. Rutenberg 
Biophysical Journal 
Volume 101, Issue 9, Pages (November 2011)
DOI: /j.bpj
Copyright © 2011 Biophysical Society Terms and Conditions

2. Figure 1
(Thin blue lines) Twenty-five independent stochastic photobleaching curves from n0 = 500 initial fluorophores with lifetime τ = 1, from exact numerical simulations. The number of unbleached fluorophores n are plotted versus time t. (Solid line) Deterministic average, n0 exp(−t/τ). The time-dependent magnitude and the nonzero autocorrelations of the photobleach fluctuations are apparent. (Inset) Distribution of the best-fit lifetimes τ (106 samples over 1000 bins) for naive least-squares fits to the stochastic curves, showing significant variation.
Biophysical Journal  , DOI: ( /j.bpj )
Copyright © 2011 Biophysical Society Terms and Conditions

3. Figure 2
Scaled variance of the fluorescence intensity σ2I/(νI0) versus unbleached fraction 1 − p, where p = exp(−t/τ). (Dashed black line) Parabolic average, from Eq. 4. (Thin red curves) Result of exact stochastic simulations of photobleaching n0 = 100 initial fluorophores. Each curve is the average of the measured variance over M = 100 samples.
Biophysical Journal  , DOI: ( /j.bpj )
Copyright © 2011 Biophysical Society Terms and Conditions

4. Figure 3
Scaled variance of single-cell estimates of ν, σ2ν /ν2 versus the number of initial fluorophores n0. The analytic variance for division-fluctuation with p = 1/2, σν1/22/ν2 from Eq. 11, is shown (green line) together with numerical confirmation from 106 independent samples shown (red circles). The analytic variance for the integrated photobleaching, σ2ν /ν2 from Eq. 12, is shown (black line) together with numerical confirmation from 106 independent samples shown (red diamonds). The relative error in ν from M samples is then σν/(νM). For every n0 > 1, the error is considerably less when the integrated photobleaching fluctuations are used.
Biophysical Journal  , DOI: ( /j.bpj )
Copyright © 2011 Biophysical Society Terms and Conditions

5. Figure 4
Ratio of the estimated to the actual value of ν, νest/ν, versus the number of cells M in a finite ensemble. (Solid red line) Predicted systematic error from Eq. 14. (Green points) Average results of 106 simulations of M cells each starting with n0 = 100 fluorophores. Qualitatively identical results are found for larger n0. The statistical errors shown are the measured standard deviations of the single-cell values of νest/ν. For M > 1, the systematic errors due to a finite number of cells M can be corrected with a multiplicative factor of 1/(1−1/M), from Eq. 14 (black dots and error bars).
Biophysical Journal  , DOI: ( /j.bpj )
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6. Figure 5
(a–c) Simulated field of view with region of interest (red circle, encompassing 452 pixels) surrounding one bacterium, at t = 0, t/τ = ln(2), and t/τ = ln(6). Each bacterium has n0 = 100 fluorophores initially, with ν = 753 (appropriate for EGFP with Δt/τ = 0.1, see text) and Gaussian variance per pixel of σ2G = 4; (d) single-cell variances σ2I/I0 for five cells versus 1 − p, where p = exp(−t/τ) is the fraction of unbleached fluorophores; (e) each trace (red) is the average of M = 100 single-cell variances, divided by the background-subtracted initial intensity I0; (f) the same as panel e but with ν=72 (for R6G, see text); (g) estimated ν-values for ensembles of M cells from Eq. 6 using traces like those from panels e and f—the average and standard deviations are shown for ν = 753, 144, and 72 (solid red circle, open blue circle, and solid blue circle, respectively); and (h) same as panel g but corrected for the finite number of cells using Eq. 14. Only for very small ν (solid blue circles) are biases due to uncorrected shot-noise evident.
Biophysical Journal  , DOI: ( /j.bpj )
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