Temperature-induced beta-aggregation of fibronectin in aqueous solution.

Fibronectin structural reorganization induced by temperature has been investigated by Fourier-transform infrared (FT-IR) spectroscopy and light-scattering experiments. At 20 degrees C, from resolution enhanced by FT-IR spectra, 43% of beta sheet, 31% of turn and 26% of unordered structures were estimated. Static and quasi-elastic light-scattering results do not change significantly between 20 and 34 degrees C. Just below 50 degrees C, a decrease of 1/3 of beta sheet structures contents is observed, concomitantly with a corresponding increase of turn. The contribution of disordered structures is found to be temperature-independent. Above 50 degrees C, our data reveals the formation of intermolecular hydrogen bonding leading to the formation of intermolecular beta sheet structures. The IR band absorption at 1618 cm(-1) increases strongly as a function of temperature. The scattered intensity increases and becomes strongly q(2)-dependent. The dynamic structure factor is not a single exponential decay and becomes strongly dependent on the scattering angle. These results demonstrate that aggregation occurs in fibronectin solution. When temperature decreases, this aggregation is found irreversible. Fibronectin aggregation is driven by the formation of intermolecular hydrogen bonds responsible for intermolecular beta sheet structures.