Counting Proteins and Nucleic Acids with Single-molecule Microscopy

Single-molecule localization microscopy (SMLM) has the potential to revolutionize proteomic and genomic analyses by providing information on the number and stoichiometry of proteins or nucleic acids aggregating at spatial scales below the diffraction limit of light. Here, we present our progress in developing a molecular counting technique for SMLM data built upon the exponentially distributed blinking statistics of photoswitchable fluorophores. The approach was motivated by a desire to quantify the single-cell variability in plasmid copy number, but can be applied to a wide range of applications. We will present our work benchmarking the method on fluorescently labeled, surface mounted DNA origami grids and our progress in counting plasmids. The accuracy of our results illustrates SMLM's utility for optical -omics analysis.