Laser diffraction of single intact cardiac muscle cells at rest

The laser diffraction of single cardiac muscle cells shows distinctive diffraction orders and has the following characteristics. (1) When projected on a screen each diffraction order can be described as an irregular column of fine structures consisting of elliptical spots and short jagged stripes. (2) The fine structures associated with the left and right diffractions of the same diffraction order cannot be correlated according to the plane grating equation, and they do not interchange after the cell has been rotated by 180 degrees around its length. (3) For the same diffraction order, the average diffraction angle of the fine structures as a function of laser incident angle follows the plane grating equation. (4) The meridional diffraction angles of different orders are not related by the plane grating equation. (5) For the same diffraction order, the total intensities of the left and right diffractions are not equal. (6) The left or right intensity of a diffraction column shows a single broad peak as a function of laser incident angle. The incident angles corresponding to the left and right peaks are symmetrical to the axis of normal incidence and are interpreted as the Bragg angles of the Z-discs and the planes formed by the intersections of the A- and I-bands of individual myofibrils. The diffraction measurements are consistent with a model in which the myofibrils are randomly packed in the cell and each myofibril acts as a cylindrical diffractor of one-dimensional order.