Analysis of Single-molecule Mechanical Recordings: Application to Acto-myosin Interactions

Several laboratories have now developed methods to make single-molecule mechanical recordings from interacting pairs of biological molecules. The mechanical work done (product of force and distance) by a single biomolecular interaction is usually of the same order as thermal energy. Recordings made from non-processive, intermittently interacting, molecular motors such as acto-myosin therefore contain a large background of thermal noise. We have applied Page's test to analyse mechanical interactions between muscle myosin II's and F-actin recorded using an optical tweezers based single-molecule mechanical transducer. We compare Page's test with other variance-based methods and find it to be a robust method for analysing both simulated and real data sets. We discuss some of the problems associated with automatic detection of transient mechanical events in noisy data signals, and show that if the start and end points of individual events are known accurately then the events may be synchronised and combined to give more detailed information about different mechanical states.