Maximum‐Likelihood Approach to Single‐Molecule Polarization Modulation Analysis

Mobile or not mobile? Polarization modulation has been used to probe single-molecule dynamic heterogeneity of dye molecules that are either surface-bound or incorporated in the biological system calmodulin–plasma membrane calcium ATPase. A maximum-likelihood approach was applied to determine modulation depth and phase shift of the fluorescence trajectories (see picture), which give a measure of the orientational mobility of the molecules.