Molecular Characteristics of Canine Cardiac Myosin.

• Contraction of the heart is dependent upon the proteins myosin and actin. Studies of these contractile proteins have therefore been of interest in the understanding of the normal contractile process, and attempts have been made to relate the diminished cardiac contraction observed in congestive heart failure to alterations in the myosin molecule. Cardiac myosin has been prepared generally by modification of the basic Szent-Gyorgyi technique used for isolation of skeletal muscle myosin. It is now clear from chemical and immunological evidence that solutions of skeletal muscle myosin prepared by such techniques are not homogenous.~° Recently, Marshall (personal communication) has shown that conventionally prepared solutions of chicken skeletal "myosin" can be separated into three components. He presents cogent evidence for the belief that the two minor components are impurities and that the major component represents myosin freed from such impurities.