Fine fiber
Microfibers or actin fibers are one of the fibers in the cell that constitute the cytoskeleton that maintains the shape of the cell, changes its shape, or is responsible for the transport of substances within the cell. Actin, a protein, is an aggregate that can be formed by polymerizing on a fiber membrane. A polymer called a fiber membrane actin is a main constituent. Thus, microfibers are often called actin fibers, but since they are not fiber structures composed solely of actin, care must be taken when referring to actin fibers. The actin that constitutes the fine fiber is β-actin, which is different from α-actin contained in the stem. The outer diameter is about 6 nm. It has a double screw structure, so it can twist precisely once to 13.5 molecules of actin molecule, 35nm. Microfibers can be observed by electron microscopy, as well as by molecules called paloyidine, which has the property of binding to actin. Actin binds phalloidin with fluorescent dye such as rhodamine to stain actin fiber and can be observed under fluorescence microscope.