Sarcomere length determination using laser diffraction. Effect of beam and fiber diameter.

An experimental and theoretical analysis is presented involving the effect of variation in fiber and beam diameter upon the determination of average sarcomere length in isolated single muscle fibers using laser light diffraction. The muscle diffraction phenomenon is simplified by first considering diffraction order position and intensity to be the result of grating and Bragg diffraction. It is the product of the intensity profiles, which results from these types of diffraction, that produces the diffracted order. These simplifying assumptions are then extended to the case of the real muscle. Based on these considerations and the theory that we recently presented, conditions are set forth under which grating information (i.e., sarcomere length) can be maximally expressed to yield accurate average sarcomere length values.