Figure 1.

(a) Sample time series from a single-molecule fluorescent energy transfer (smFRET) experiment, which measures a ratio of intensities of two fluorescent labels E_FRET = I_A/(I_D + I_A) to detect conformational transitions between two states (see section 5). Analysis with a variational Bayesian HMM shows states with means and precisions that vary significantly from molecule to molecule. Moreover photobleaching of the fluorophores results in time series of variable (exponentially distributed) lengths. (b) Histogram of observables x_{n, t}, and inferred state means μ_{n, k} (red) along with empirical Bayes estimates of priors (dotted lines) for an ensemble of N = 336 time series from a single experiment.