Technique Measures Muscle Contraction At Molec...( CHAMPAIGN Ill. - A measurement techn...)

CHAMPAIGN, Ill. - A measurement technique originally designed for studying interactions within molecules of DNA has been used to examine muscle movement at the molecular level, says a University of Illinois researcher who developed the procedure.

Called luminescence resonance energy transfer, the technique is shedding light on how the two major components of muscle -- proteins of myosin and actin -- interact to create movement.

"Myosin is a little molecular motor that converts chemical energy into mechanical motion," said Paul Selvin, a professor of physics at the U. of I. "To do this, there are tiny myosin heads that stick out and grab the actin. Muscle contraction occurs when the myosin heads rotate and pull on the actin filaments."

The details of how the myosin heads move are not well understood, however. "The leading model says the myosin heads act like little lever arms that pull on the actin in much the same way that an oar pulls on water," Selvin said. "Our measurements provide direct evidence in support of this lever-arm model."

Selvin and his colleagues -- professor Roger Cooke at the University of California at San Francisco, professor Ralph Yount and postdoctoral research associate Handong Li at Washington State University, and postdoctoral research associate Ming Xiao and graduate student Gregory Snyder at the U. of I. -- recently measured the molecular movement of probes precisely positioned on the myosin head.

"At the molecular level, the shape changes are so small -- 2 to 10 nanometers, or 10,000 times smaller than the width of a human hair -- you can't see them by eye or even with a regular microscope," Selvin said. "Instead, we label various parts of the myosin with different dyes and watch how the light emitted from the dyes changes as the protein moves."

Selvin's measurement technique is a new twist on a 40-year-old technique called fluorescence resonance energy transfer. Instead of using conventional dyes, however, Sel
'"/>

Contact: James E. Kloeppel, Physical Sciences Editor
kloeppel@uiuc.edu
217-244-1073
University of Illinois at Urbana-Champaign
4-Feb-1999