A Sarcomere-Mimetic Gel: Gelation of Astral-Shaped Actin Filaments with Their Plus End Connected on Photopolymer Beads by Myosin Filaments

Abstract

ABSTRACTWe have developed a method of a stepwise construction of a gel consisting of (i) astral-shaped actin filaments with their plus end connected on photo-responsive polymer beads and (ii) bipolar myosin filaments as linkers in order to mimic sarcomeric structure, the basic unit of a muscle. In the method, firstly, 4 μm diam. beads were prepared from an acrylate polymer containing azobenzene moiety by a good-solvent evaporation technique. Next, gelsolin, which servers and remains bound to the plus end of an actin filament, was adsorbed and then immobilized on the bead surface by exposure to light from blue light-emitting diodes, and then fluorescent actin filaments were mixed with the beads. Formation of star-like, astral actin filaments on the beads were observed in fluorescent microscopy. Finally, the beads with actin filaments were mixed with myosin mini filaments with ca. 1 μm in length. Dozens of the beads were observed to be assembled into a gel form in optical microscopy. After adding adenosine triphosphate to the gel solution, the gel was slowly contract up to 60% comparing with its original volume, suggesting that linker myosin filaments moved on the actin filaments toward the plus end on the beads.