A new sensitive instrument that combines two molecular imaging technologies can provide scientists with detailed insight into dynamic molecular processes. Two physicists from the University of Illinois have combined their expertise in single-molecule biophysics – fluorescence microscopy and optical traps – to study the binding and unbinding of individual DNA segments to a larger strand. Their findings appeared in Nature Methods on Feb. 20, 2011 (doi: 10.1038/nmeth.1574). Physicists from the University of Illinois have developed an instrument that uses two molecular imaging techniques to capture individual DNA segments binding and unbinding to a larger strand. On their own, the two techniques cannot provide the sensitivity needed to image single DNA strands. Although fluorescence microscopy techniques enable researchers to observe proteins as they conform and move, they lack the spatial range to track movement over distances. Optical traps allow scientists to study a protein’s translocation, but not its conformation, making it difficult to know how many proteins or which types are involved. By combining the two methods, the researchers measured both the protein’s motion – sensitive to translocation as small as one DNA base pair – as well as its conformational changes as it acted. Their findings revealed details about the DNA’s mechanism that was not accessible using the two techniques separately. The work was supported by the National Science Foundation, National Institutes of Health and the Howard Hughes Medical Institute.