A.: Chemical characterization of cardiac myosin from normal dogs and from dogs with chronic congestive heart failure

The size and chemical nature of the myosin molecule have been studied extensively in enzyme preparations obtained from skeletal muscle (1-7), but a paucity of data is available on cardiac myosin. Furthermore, different values for the molecular weight of cardiac myosin have been reported. Olson (8) reported a value of 223,000 for the molecular weight of cardiac myosin whereas Ger-gely and Kohler (9) presented evidence that myosin from cardiac muscle has a molecular weight of 500,000, which is similar to that ob-tained during the most recent observations on skeletal muscle myosin (4-7). It has been suggested that the cardiac myosin molecule is altered in cardiac failure to form