Aggregation dynamics of laminin-1 in a physiological solution: A time-resolved static light scattering study

The aggregation of laminin-1 in a physiological solution was observed using time-resolved static light scattering. In a solution containing 150 mM of NaCl and 1 mM of CaCl2, with a pH of 7.2 buffered by 50 mM Tris, and maintained at 25 °C, the weight-averaged mass (molecular weight) Mw, and radius of gyration Rg, of the aggregate were measured at 10 s intervals. The aggregation kinetics changed from reaction-limited cluster aggregation (RLCA) to diffusion-limited cluster aggregation (DLCA) over time. The fractal dimension estimated in the DLCA regime was 1.71 from the Mw∼Rgdf relationship, which is consistent with the df of 1.75 obtained from an Rg∼t1/df plot. Direct calculation of df using the scattering intensity and scattering vector revealed that df gradually increased over time in the DLCA regime, suggesting that spontaneous restructuring of the aggregate had occurred. This restructuring would have been caused by hydrophobic contact in the aggregate. The form factor of the aggregate was well fitted by a linear random coil model and not by a simple spherical model.