Studying acto-myosin interactions

The ability to measure nanometre displacements and piconewton forces means mechanical and kinetic properties of single motor proteins can be measured. In order to study intermittently interacting motors like acto-myosin-II from muscle, a 

The optical tweezers stiffness is set to about 0.02 pN nm (adjusting the laser power), which is about 10000 times less stiff than an AFM cantilever. This is sufficient to hold the beads stably trapped but still about 10 100 times less stiff than the acto-myosin complex. This means that myosin can undergo its conformational change essentially unhindered by the tweezer. 

---