Multi-parameter photon-by-photon hidden Markov modeling.

Harris, Paul David; Narducci, Alessandra; Gebhardt, Christian; Cordes, Thorben; Weiss, Shimon; Lerner, Eitan · Nat Commun · 2022

basic_science · Level V

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Abstract

Single molecule Förster resonance energy transfer (smFRET) is a unique biophysical approach for studying conformational dynamics in biomacromolecules. Photon-by-photon hidden Markov modeling (H<sup>2</sup>MM) is an analysis tool that can quantify FRET dynamics of single biomolecules, even if they occur on the sub-millisecond timescale. However, dye photophysical transitions intertwined with FRET dynamics may cause artifacts. Here, we introduce multi-parameter H<sup>2</sup>MM (mpH<sup>2</sup>MM), which assists in identifying FRET dynamics based on simultaneous observation of multiple experimentally-derived parameters. We show the importance of using mpH<sup>2</sup>MM to decouple FRET dynamics caused by conformational changes from photophysical transitions in confocal-based smFRET measurements of a DNA hairpin, the maltose binding protein, MalE, and the type-III secretion system effector, YopO, from Yersinia species, all exhibiting conformational dynamics ranging from the sub-second to microsecond timescales. Overall, we show that using mpH<sup>2</sup>MM facilitates the identification and quantification of biomolecular sub-populations and their origin.

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