Film formation
Protein solutions (5% w/v) and glycerol (2%, 3%, and
4% w/v) were mixed thoroughly in distilled water and the
pH of the solution was appropriately adjusted with 1 m
NaOH or 1 m HCl. Subsequently, the protein solutions
were heated in a water bath at 80 C for 30 min. The
heated and unheated protein solutions were cast on a
levelled Nafron sheet (Nichias Corp., Tokyo, Japan)
glued to the base of a plastic tissue culture dish