Thermally induced aggregation of human transferrin receptor studied by light-scattering techniques.

The thermal stability of transferrin receptor isolated from human placenta in detergent-free solution has been investigated by static light-scattering and photon correlation spectroscopy. In detergent-free solution at 293.2 K, human transferrin receptor (hTfR) forms stable associates with a hydrodynamic radius of 16 nm. With increasing temperature the particles get more compact, above 340 K a phase transition takes, place and spontaneous aggregation of the receptor occurs. Under these conditions large clusters are formed that lead to fractal aggregates, coexisting with dendritic crystalline structures. The experimental findings are compatible with a model, which involves a reaction limited cluster-cluster aggregation mechanism in conjunction with a nucleation process. The molar enthalpy change associated with the phase transition was determined to be (1860 +/- 150) kJ/mol(-1) at a transition temperature of (341.3 +/- 0.2) K.