Joint statistical analysis of multichannel time series from single quantum dot-(Cy5)_n constructs

One of the major challenges in single-molecule studies is how to extract reliable information from the inevitably noisy data. Here, we demonstrate the unique capabilities of multichannel joint statistical analysis of multispectral time series using Foster resonance energy transfer (FRET) in single quantum dot (QD)-organic dye hybrids as a model system. The multispectral photon-by-photon registration allows model-free determination of intensity change points of the donor and acceptor channels independently. The subsequent joint analysis of these change points gives high-confidence assignments of acceptor photobleaching events despite the interference from background noise and from intermittent blinking of the QD donors and acceptors themselves. Finally, the excited-state lifetimes of donors and acceptors are calculated using the joint maximum likelihood estimation (MLE) method on the donor and acceptor decay profiles, guided by a four-state kinetics model.