Because an image voxel has (x, y, and z) dimensions of 80 × 80 × 250 nm, we considered two possibilities in our calculation of the area that a punctum might encompass on the plasma membrane (its plasma membrane area). For one, we assumed all punctum voxels present their xy face to the plasma membrane. In this case, the plasma membrane area of each voxel was 80 × 80 nm. For the other, we assumed that the xz or yz face was on the plasma membrane, producing a plasma membrane area of 80 × 250 nm.
