Reports

Characterization of cod myosin aggregates using static and dynamic light scattering

Published:

01/05/2007

Authors:

Tom Brenner, Ragnar Jóhannsson, Taco Nicolai

Supported by:

Matís, Rannís, AVS

Characterization of cod myosin aggregates using static and dynamic light scattering

Myosin was isolated from cod by different methods that yielded clusters of pure myosin. These clusters contained between 8 and 20 myosin molecules, and were stable in cold conditions (T <20 ° C) and in dilute solutions (C <5g / L) with 0.5M KCl at pH 6.0 to 8.0. At higher protein levels, it gelled or fell out. The low concentration cluster was examined by absorbance measurements and light distribution. The clustering stopped after a long heating time in most cases, but under certain circumstances it continued and led to the precipitation of the protein. Cooling led to further clustering, which appears to be reversible due to reheating. The structure of the clusters was determined after cooling and dilution. Self-contained clusters were analyzed, with a refractive index of 2.2. The size of the clusters increased with increasing temperature (30-70 ° C), increasing protein concentration (0.4-3 g / L) and decreasing pH (8.0-6.0). The construction of the clusters, however, was independent of formation conditions.

Myosin was extracted from Atlantic Cod (Gadus Morhua) using different methods resulting in small aggregates of pure myosin. These aggregates consisted of between 8 and 20 myosin molecules and were relatively stable at low temperatures (T <20 ° C) in dilute (C <5g / L) solutions containing 0.5M KCl in the pH range 6.0-8.0. At higher concentrations precipitation or gelation was observed. Heat induced aggregation at low concentrations was studied using turbidimetry and light scattering. In most cases the aggregation stagnated at longer heating times, but in some cases the aggregation continued until it led to precipitation of large flocs. Cooling led to further growth of the aggregates, which was, however, reversed upon heating. The structure of the aggregates was determined after cooling and dilution using static and dynamic light scattering. Self-similar aggregates were observed, characterized by a fractal dimension of 2.2. The size of the aggregates formed after extensive heating increased with increasing temperature (30-70 ° C), decreasing pH (8.0-6.0) and increasing protein concentration (0.4-3g / L), but the structure of large aggregates was independent of the conditions.

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