Abstract
In this work, the gelation kinetics and fractal character of lysozyme gel matrices developed in tetramethylurea (TMU)-water media were investigated. Gelation times were determined from the temporal crossover point between the storage, G ′ , and loss, G ″ , moduli, as a function of the binary solvent composition and of protein concentration. The inverse dependence of the upper limit of the linear viscoelastic region ( γ 0 ) on protein concentration indicate that the lysozyme gels belong to the “strong link” kind, a gel category where interparticle links are stronger than intraparticle ones. Lysozyme gel fractal dimensions ( D f ) were determined from the analysis of rheological data according to a scaling theory by Shih et al. [Phys. Rev. A 42 (1990) 4772–4779] and were found to be compatible with a diffusion-limited cluster-aggregation kinetics (DLCA) for lysozyme gels formed at the TMU mass fraction in the binary organic–aqueous solvent, w TMU = 0.9 , and with a reaction-limited cluster aggregation kinetics (RLCA) for w TMU in the 0.6 ⩽ w TMU ⩽ 0.8 range.
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