Molecular chaperone-like activity for protein refolding was investigated using nanogels of self-assembly of cholesterol-bearing pullulan. Nanogels e¡ectively prevented protein aggregation (i.e. carbonic anhydrase and citrate synthase) during protein refolding from GdmCl denaturation. Enzyme activity recovered in high yields upon dissociation of the gel structure in which the proteins were trapped, by the addition of cyclodextrins. The nanogels assisted protein refolding in a manner similar to the mechanism of molecular chaperones, namely by catching and releasing proteins. The nanogels acted as a host for the trapping of refolded intermediate proteins. Cyclodextrin is an e¡ector molecule that controls the binding ability of these host nanogels to proteins. The present nanogel system was also e¡ective at the renaturation of inclusion body of a recombinant protein of the serine protease family.

This study revealed that there was a high correlation between the voxel values of CBCT and the CT numbers of MSCT. Although this was an in vitro study with assumed ideal conditions for measuring voxel values, there was a clear possibility for estimating CT numbers and BMD using the voxel values from the CBCT images, but the relationship was not entirely linear and should be examined further.

Novel photoresponsive nanogels were prepared by the self-assembly of spiropyrane-bearing pullulan (SpP). The solution properties of the nanogels could be controlled by photostimulation via isomerization between hydrophobic spiropyrane and hydrophilic merocyanine. The molecular chaperone-like activity of the nanogels in protein refolding was investigated. The activity of citrate synthase significantly increased when the amphiphilicity of SpP nanogels was switched by photostimulation.

A cholesteryl-bearing poly(l-lysine) (CHPLL) was synthesized by the condensation reaction of cholesteryl N-(6-isocyanatehexyl) carbamate with poly(l-lysine) (PLL). Sonicated samples of CHPLLs, which were substituted by 0.8, 3.4, and 5.4 cholesteryl groups per 100 lysine units, gave a single peak after sufficient ultrasonication by high-performance liquid column chromatography. The particle sizes (RG) and aggregation numbers (N), which were determined by static light scattering, increased with an increase in the DS of cholesterol in CHPLL (R G = 16−22 nm, N = 1.3−4.2). These CHPLLs form an α-helical structure at a lower pH compared to the parent PLL by circular dichroism spectroscopy. The partial modification of PLL by hydrophobic cholesteryl groups leads to the formation of hydrogel nanoparticles by their self-association, and this induces the α-helical structure of PLL. This α-helicity can be controlled by the degree of substitution of cholesteryl groups. The helical content of CHPLL decreased upon the addition of β-cyclodextrins, which were complexed with cholesteryl groups and reached a value similar to that of unmodified PLL. The secondary structure of CHPLL was controlled by host−guest interaction with cyclodextrin.