A technique for studying cardiac myosin dynamics using optical tweezers

A primary protein involved in human muscle contraction is myosin, which exists in $\alpha $- and $\beta $- isoforms. Myosin exerts forces on actin filaments when ATP is present, driving muscle contraction. A significant decrease in the population of cardiac $\alpha $-myosin has been linked to heart failure. It is proposed that slow $\beta $-myosin in a failing heart could, through introduction of a drug, be made to mimic the action of $\alpha $-myosin, thereby improving cardiac muscle performance. In working towards testing this hypothesis, the focus of this work is to develop a technique to measure forces exerted by myosin on actin using optical tweezers. An actin-myosin arrangement is constructed between two optically trapped polystyrene microspheres. The displacement of a microsphere is monitored when ATP is introduced, and the force responsible is measured. With this achieved, we can then modify the actin-myosin arrangement, for example with varying amounts of $\alpha $- and $\beta $- myosin and test the effects on forces exerted. In this work, assemblies of actin and myosin molecules and preliminary force measurements are discussed.