Supramolecular Nanotube Hydrogels: Remarkable Resistance Effect of Confined Proteins to Denaturants

Nanotube networks self-assembling from asymmetric bolaamphiphile, N-(beta-D-glucopyranosyl)- N'-(2-glycylglycylglycineamideethyl)-octadecanediamide 1, acted as hydrogelators. The obtained nanotube hydrogel was able to separately fix a green fluorescent protein (GFP) and a myoglobin (Mb) into not only independent nanospaces consisting of three-dimensional meshworks formed in between nanotubes but also a one-dimensional hollow cylinder of the nanotube itself. Especially, the fixed GFP and Mb into the nanotube hollow cylinder with 9 nm inner diameter showed strong resistance to denaturants such as guanidinium chloride and urea at high concentrations. The oxygen binding ability of the Fixed Mb into the nanotube hollow cylinder was remarkably Superior to those of the fixed Mb into the nanotube meshworks and the free Mb in bulk. The nanotube hydrogel also showed slow release behavior depending oil pH conditions. Such a unique fixation property of the nanotube hydrogel has never been seen for preceded supramolecular and polymer hydrogels having three-dimensional meshworks formed in between nanofibers. Hence, the nanotube hydrogel can function as a novel soft material applicable to biological and medical fields.