STUDY OF NUCLEATION-RELATED PHENOMENA IN LYSOZYME SOLUTIONS - APPLICATION TO GEL GROWTH

Two populations of aggregates are generally indentified in supersatura ted solutions of biological macromolecules: small aggregates of a size which is less than 5 nm and large aggregates, the largest of which ar e at least one order of magnitude bigger. In order to understand the r ole played by the microporous network of a gel in the growth and behav iour of these different species in the prenucleation period, an in sit u observation of nucleation has been carried out using either free sol utions or solutions trapped in agarose gels. In a previous study, free solutions were investigated by small-angle neutron scattering (SANS) to identify the small aggregates. Optical observations, made under the same conditions, revealed the formation of an amorphous precipitate w hich disappeared at the end of the experiment. The sedimentation of th is phase, which occurs in free solution but never occurs in gelled sol ution, depletes the solution bulk and this could explain why the nucle ation density is higher in agarose gel than in free solution. The case of silica gel, the behaviour of which is completely different with re spect to nucleation, will be discussed.