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A green fluorescent protein readout follows the corresponding periodically regulated expression, so an individual cell has repeated peaks in fluorescence. Biological translation, fluorophore maturation, and protein degradation introduce a delay and smooth the peaks. For a simple mature fluorescent reporter with periodic production $s(t)$, $\dot{G}=s(t)-\gamma G$ gives $G(t)=G(0)e^{-\gamma t}+{\int }_0^t{e}^{-\gamma (t-u)}s(u)du$. A long lifetime therefore makes the modulation weak about an accumulated background. Intrinsic gene-expression noise makes successive peak heights and periods irregular; averaging cells with unrelated oscillation phases can hide the single-cell oscillations.

Under the simplest interpretation, each spot contains two equally bright, independently bleaching green fluorescent protein emitters. Losing one halves the fluorescence and losing the other removes it. A stable protein dimer carrying one active label per subunit is consistent with this result. The conclusion is two active emitters in the observed spot; it does not by itself rule out unresolved coincident proteins, incomplete fluorescent maturation or blinking. Permanent membrane binding makes loss by dissociation less plausible, but lateral motion out of the observation region would still need experimental control.^[ref]

Let their independent photobleaching times be $T_A,T_B\sim \mathrm{Exp}(k_b)$. Then $t_1=\min (T_A,T_B)$ has rate $2k_b$, while the memoryless remaining lifetime $t_2-t_1$ has rate $k_b$ and mean $1/k_b$, matching the stated single-emitter calibration. The two-emitter photobleaching completion time is the maximum, not one single exponential and not a sum of two equal-rate exponential variables. Its cumulative distribution function isDifferentiating gives its probability density function:with zero density for $t<0$. It integrates to one, and its mean is $1/(2k_b)+1/k_b=3/(2k_b)$. This uses two active fluorophores at the start of observation, constant illumination and independent irreversible bleaching with the calibrated rate.