In this paper, we reveal that microtubules (MTs), reconstructed from tubulin in vitro in the presence of guanosine-5'-triphosphate (GTP), have a ring or spiral shape on a motor protein-fixed surface, and these MTs show biased motion in the counterclockwise direction. By cross-linking these MTs during the sliding motion, we obtained large ring-shaped MT assemblies, 1 approximately 12.6 microm in diameter. The ratio of the rings rotating in the counterclockwise direction to those rotating in the clockwise direction was approximately 3/1. Under optimized conditions, the ratio was as high as 14/1. Thus, we successfully obtained aggregated MTs with a large hierarchic structure that shows a preferential motion, through a dynamic process in vitro.

We extract non-denatured lignocellulosic biomass by combined wet-type ultrafine bead milling and enzymatic saccharification at pH 5.0 and 50 °C.

Biopolymers such as DNA, F-actins, and microtubules, which are highly charged, rodlike polyelectrolytes, are assembled into architectures with defined morphology and size by electrostatic interaction with multivalent cations (or polycations) in vivo and in vitro. The physical origin to determine their morphology and size is not clearly understood yet. Our results show that the actin bundle formation consists of two stages: the thickness of actin bundles is determined nearly at the initial stage, while the length of actin bundles is determined later on. It is also found that the thickness of actin bundles decreases with the increase of polycation-mediated attraction between F-actins. From these results, we propose the anisotropic nucleation-growth mechanism, in which the thickness of actin bundles is determined by critical nucleus size, whereas the length of actin bundles is determined by the concentration of free actins relative to nucleus concentration. Observing that polycations are concentrated in some sites of actin bundles, which are thought to be nucleation sites to initiate the formation of actin bundles, supports this model. This anisotropic nucleation-growth mechanism of actin bundles can be broadly applied to the self-assembly of rodlike polyelectrolytes.

A series of syndiotatic P5CPn polymethylenes was prepared with 4-(trans-4-pentylcyclohexyl)phenoxy moieties linked to each backbone carbon atom via an alkyloxycarbonyl spacer and with even numbers of alkyl carbons n ranging from 2 to 14, and their thermotropic behaviors were investigated. The P5CPn, except P5CP2, formed smectic phases in which the rod-like polymethylene backbones were arranged in rectangular lattices, and the sidechain mesogens were aggregated into layers parallel to the shorter sides of the rectangular lattices. The packing of the mesogens changed with decreasing temperature from smectic C-like to smectic I-like (SmI-like) for n = 4−8 and from smectic Alike to SmI-like for n = 10−14. In the SmI-like phases, each mesogen along the main-chain axis was connected to every sixth backbone carbon atom, revealing a correlation between the packing of the mesogens and the main-chain conformation of a 3/2 helix. Conversely, P5CP2 formed a smectic phase with the main chains arranged in rows and with the mesogens barely aggregated into layers due to the short spacers.