AVS 50th International Symposium
    Nanometer Structures Wednesday Sessions
       Session NS-WeM

Paper NS-WeM7
Nanomechanics of Cytoskeletal Proteins

Wednesday, November 5, 2003, 10:20 am, Room 308

Session: Nanomechanics
Presenter: J.G. Forbes, NIAMS, NIH, DHHS
Authors: J.G. Forbes, NIAMS, NIH, DHHS
K. Wang, LMB, NIAMS, NIH, DHHS
Correspondent: Click to Email
Striated muscle is the primary source of biomechanical force in organisms from worms to man, and can be thought of as a composite material that is organized on several length scales. The motor protein in all muscles is myosin, which generates piconewtons force through its interaction with actin and the hydrolysis of ATP. The tiny force generated by a single myosin is amplified by aggregating large numbers of myosin heads into an ordered structure called the thick filaments. The thick and thin filaments are then assembled into the basic contractile machinery called the sarcomere that link serially from one end of the muscle cell to the other. Striated muscle shortens by the sliding of actin filaments as they are dragged towards the center of the myosin filaments. When muscle relaxes, its original length is restored elastically. An array of cytoskeletal proteins are required to regulate the size, assembly and function of the sarcomere, as well as transmit force and provide elasticity for restoring the structure. One such protein is the giant protein titin (3-4E6 g/mol), which spans half of the muscle sarcomere length. The passive elasticity of muscle at a physiological range of stretch arises primarily from the extension of titin. Nebulin serves as a ruler for the actin filaments and may alter their compliance and tensile strength. Other proteins such as dystrophin help transmit force out of the muscle and desmin forms intermediate filaments, which help to stabilize the sarcomere organization. We have studied the elastic properties of these motor and cytoskeletal proteins via force spectroscopy with the AFM. We have found that the elasticity of proteins can arise from mechanisms other than simple entropic elasticity. These mechanisms work at the nanoscale and may allow for their properties to be fine tuned to fit the need of muscle to work under a variety of conditions. These insights from biology may allow for the engineering of more effective elastic materials.