Quasi-simultaneous imaging/pulling analysis of single polyprotein molecules by atomic force microscopy.

Most of studies in protein nanomechanics have used the atomic force microscope (AFM) in its force-measuring mode on immobilized protein repeats (polyproteins) as single-molecule markers. Here, we add imaging capabilities to a standard, state-of-the-art AFM "puller" and integrate the most powerful programs of analysis available for both AFM modes. This unique instrument allows high-resolution, quasi-simultaneous imaging/force spectroscopy in aqueous solution. We demonstrate its capabilities using polyproteins of a model system (titin I27 domain). This tool should greatly facilitate the development of a much needed universal functionalization system for AFM, one that should allow better sample control and an improved efficiency of protein immobilization.