  Biosensors based on the principle of surface plasmon resonance (SPR)
detection were used to measure biomolecular interactions in sarcomeres and
changes of the dielectric constant of tubulin samples with varying
concentration. At SPR, photons of laser light efficiently excite surface
plasmons propagating along a metal (gold) film. This resonance manifests itself
as a sharp minimum in the reflection of the incident laser light and occurs at
a characteristic angle. The dependence of the SPR angle on the dielectric
permittivity of the sample medium adjacent to the gold film allows the
monitoring of molecular interactions at the surface. We present results of
measurements of cross-bridge attachment/detachment within intact mouse heart
muscle sarcomeres and measurements on bovine tubulin molecules pertinent to
cytoskeletal signal transduction models.
