Nature Commun. 5, 5123 (2014)

Credit: NATURE PUBLISHING GROUP

The tracking of single molecules, most often achieved through chemically attached fluorophores, is essential to the study of subcellular dynamics and soft polymeric materials. Many techniques exist to accurately localize and track single molecules, yet the tracking of their shape and size as they diffuse in their environment has for the most part remained experimentally inaccessible. Now, Satoshi Habuchi and colleagues describe a method that tracks the cumulative area occupied by a diffusing molecule. The method is able to provide information about molecular size and frequency of conformational changes in addition to translational diffusion. By measuring the diffusion coefficients in two dimensions and the conformational dynamics of double-stranded DNA molecules of various lengths and topologies, the researchers show that the cumulative-area technique is more accurate at determining single-molecule diffusion coefficients than conventional fluorescent-based single-molecule tracking methods. The researchers state that with further development their approach could achieve three-dimensional area tracking, and that it could be combined with super-resolution microscopy and multicolour imaging for better tracking of single molecules in complex soft-matter and biological systems.