A gelatin gel sheet was UV-irradiated to raise the gel melting temperature T_m. Three second of T_m increased proportionally to irradiation time t_UV. The sheet of which T_m was larger than the culture temperature 37°C was used as a cell culture scaffold. Human fibroblast cells WI-38 adhered to the sheet and dug deeply into it regardless of t_UV, while cancer cells WI-38-VA-13 formed spheroids and did not adhere to the sheet individually at high UV dose. The cell selectivity of the scaffold could be used for biological and medical studies.

We study thermo-structural behavior of anionic lipid 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) dispersed systems. Continuous chain-melting transition of DMPG induces anomalous intermediate phase between gel and fluid phases. We found that the intermediate phase can be divided into two domains; anisotropic phase with high orientational order and isotropic viscous phase. Anisotropic phase would be identified to perforated lamellae or bicelle formed by rupturing the perforated vesicles under shear. Isotropic viscous phase, on the other hand, might be identified to densely packed perforated vesicle dispersions formed by rearranging extended bilayer membranes.

Fibrinogen is converted to fibrin monomer and forms a three-dimensional gel network in a step wise manner by the enzymatic action of thrombin (thrombin-induced fibrin gelation). On the other hand, when a fibrinogen solution is incubated at low temperatures (e.g. below 4°C), it is converted to a gel without thrombin. The fibrinogen gel induced by lowering temperature is called “cryogel” and is closely related to some diseases. However, the mechanism of fibrinogen cryogelation has not been understood yet. In this study, the effects of urea and NaCl on fibrinogen cryogelation and thrombin-induced fibrin gelation have been studied turbidimetrically. The addition of urea retarded both gelation, and the extent of retardation increased with increasing the concentration of urea. The effects of urea on fibrinogen cryogelation were much larger than those on thrombin-induced fibrin gelation, and fibrinogen cryogelation was completely inhibited by the addition of 150 mM urea. The addition of NaCl retarded fibrinogen cryogelation with increasing the concentration of NaCl. By contrast, the effects of NaCl on thrombin-induced fibrin gelation were only limited. Based on the experimental results, the contributions of hydrogen and ionic bonds to each gelation are discussed.

The molecular motions in two aqueous maltotriose solutions with different weight fractions (85% and 50%) were investigated by the dielectric relaxation and differential scanning calorimetry. The 85% solution shows two relaxation modes with the different frequency and temperature dependences in the dielectric relaxation curves. The lower frequency mode is due to the hydrated maltotriose. This mode strongly depends on temperature, indicating the structural relaxation of the solution. The higher frequency mode shows an Arrehnius type of temperature dependence ascribed to the hydrated water molecules. The 50% maltotriose solution has another relaxation mode of ice Ih crystal in addition to these relaxation modes. The temperature dependences of both solutions were compared to interpret the molecular motions on the basis of the phase behaviors.

We investigated the mechanisms of amyloid-like aggregation and gel formation in hen egg-white lysozyme (HEWL) in a mixed solvent comprising 90% v/v ethanol in water using dynamic light scattering (DLS) and circular dichroism CD. The mechanism of HEWL in ethanol aqueous solution is interpreted into three stages as: (I) denaturation of HEWL; (II) elongation of amyloid fibrils composed of β-sheet-rich HEWL by lateral aggregation; and (III) gel formation due to the creation of junctions in amyloid fibrils. The transformation of sol to gel can be confirmed by: (1) the oscillation behavior and the rapid increase in the intensity of scattered light; (2) the power-law behavior of the correlation function of scattered light g⁽²⁾(t); (3) the appearance of a long-time tail in the distribution function of the decay time G(τ); and (4) the beginning of the reduction in initial amplitude in g⁽²⁾(t). The gelation rate was strongly dependent on the protein concentration. The estimated rod length of the amyloid fibrils increased significantly over time. Scanning electron microscopy (SEM) performed on the formation of fibrils in the HEWL gels revealed that the structure was highly heterogeneous, with areas characterized by dense fiber networks interspersed with loose network areas.