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| - Light Scattering Study of Heat-Induced Aggregation and Gelation ofOvalbumin
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| - The effect of ionic strength on the interaction of ovalbumin, a globular egg white protein,in aqueous solution was investigated using static and dynamic light scattering. Strong repulsiveinteractions are observed at low ionic strength (3 mM). Aggregation of the proteins was induced by heatingat low (3 mM) and high (100 mM) ionic strength as a function of the concentration. The size of theaggregates increases with increasing protein concentration and diverges close to the critical concentrationfor gelation, which is about 60 g/L at low ionic strength and 12 g/L at high ionic strength. Static anddynamic light scattering showed that at low ionic strength linear chains are formed with little branchinguntil close to the gel point, while at high ionic strength denser branched aggregates are formed with afractal dimension close to that found for other globular protein aggregates. The observations wereconfirmed by cryo-transmission electron microscopy. Heated systems at low ionic strength remainedtransparent and were studied in situ using static and dynamic light scattering. The relaxation of theconcentration fluctuations occurs by cooperative diffusion, except when the gel point is approached anda slow secondary relaxation process is observed. The slow mode is attributed to the self-diffusion of theaggregates and restructuring of the system. The terminal relaxation time of the concentration fluctuationsdiverges in the neighborhood of the gel point because a fraction of the concentration fluctuations isprogressively frozen in.
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