Scientists exploring the physics of hearing have found an underlying molecular cause for one form of deafness. The team, led by Gerard Wong, Professor of Materials Science and Engineering, of Physics, and of Bioengineering at the University of Illinois at Urbana-Champaign, report their findings in the February 2007 issue of the journal Physical Review Letters.

Filamentous actin (F-actin) is a rod-like protein that provides structural framework in living cells. F-actin is organized into bundles by actin binding proteins, such as espin, a linker protein found in sensory cells, including hair cells in the cochlea of the inner ear. Within the cochlea, sound waves stimulate the hair cells and trigger nerve impulses that are transmitted to the brain.

Using small-angle x-ray scattering experiments at SSRL's Beam Line 4-2 and at APS, Wong's team solved the structure of various espin-actin bundles. The team learned that mutations in espin can cause actin in the bundles to 'melt' into a liquid crystal (the kind of molecular organization in a liquid crystal laptop screen), thereby making these bundles of protein filaments within the cochlear hair cells much floppier, impairing the passage of vibrations and resulting in deafness.

To learn more about this research see the full scientific highlight at:
http://www-ssrl.slac.stanford.edu/research/highlights_archive/actin-espin.html

Kirstin R. Purdy, James R. Bartles, and Gerard C. L. Wong; "Structural Polymorphism of the Actin-Espin System: A Prototypical System of Filaments and Linkers in Stereocilia", Phys. Rev. Lett. 98, 058105 (2007)