Cellulose microcrystals prepared by treating natural cellulose (cellulose I) with acid are slender rods or whiskers of a few nanometers width and are known to have properties such as high strength, high elastic modulus, and low thermal expansion. It has also long been known that cellulose, an antimagnetic material, has magnetic anisotropy and various studies have been reported on the response of microcrystals of cellulose I to a strong magnetic field. On the other hand, there have been no studies on the magnetic field response of cellulose II, the crystalline form of regenerated cellulose fibers such as rayon. Therefore, this article summarizes the magnetic field orientation behavior of cellulose I microcrystals and introduces our recent efforts on the enzymatic synthesis of cellulose II microcrystals and their three-dimensional orientation using a magnetic field. ...and more
Cellulose is a natural polysaccharide, and is functionally classified as a structural polysaccharide. Its superior strength is attributed to the fact that it is composed of multiple molecular chains, and it has a structure known as cellulose I crystal that exhibits a high crystalline modulus. The fact that such an agglomeration of polymers can be synthesized by enzymatic proteins suggests that cellulose biosynthesis is a mechanism designed to synthesize the strongest possible structure by controlling the polymer chains at ambient temperature and pressure in aqueous solvents. In comparison with the typical formation process for general-purpose polymers, which involves high temperature, high pressure, and harsh solvents, the enzyme cellulose synthase possesses an extremely sophisticated “green” mechanism for controlling polymer structure. In this paper, I will describe efforts to reconstitute the cellulose-synthesizing activity of cellulose synthase, the mechanism of which we have been seeking to elucidate for more than 10 years. ...and more
