Non-ideal behavior of binary aqueous mixtures of some urea derivatives and their capacity to induce lysozyme gelation.

The urea derivatives, namely, ethylurea (EU), 1,3 dimethylurea (1,3-DMU) and 1,1 diethylurea (1,1-DEU), in the limiting regions of their solubilities in water, and tetramethylurea (TMU) at w≥0.65 were investigated in relation to their capacity of inducing hen egg white lysozyme (HEWL) physical (non-covalent) gelation. Protein transparent gels were generated out of TMU/HO and 1,1-DEU/HO, respectively, whereas an intensively turbid gel resulted from sol-gel transition taking place in EU/HO.