Effects of a flow field on amyloid fibrillogenesis in a β-lactoglobulin solution

Abstract

The effects of a flow field on the amyloid fibrillogenesis of β-lactoglobulin (βLG) were investigated using a flow birefringence method and AFM imaging experiments. A 4wt% βLG aqueous solution was incubated at pH 2 and 80°C. A flow field was then applied by stirring at 250 and 474rpm. An incubation without stirring was used as a control sample. Flow birefringence measurements were taken at room temperature from the incubated sample solutions in which an elongational flow field was used. The birefringence pattern obtained indicated that the fibrils formed by the incubation were rigid rod-like molecules. Birefringence relaxation experiments revealed at least two relaxation processes, suggesting a double peaked distribution function for fibrils length. The length distribution of fibrils expected from the birefringence experiments was confirmed by the AFM images of amyloid fibrils. The order of the expected length of the resultant fibrils in both longer and shorter length distributions was those stirred at 250rpm≅474rpm>0rpm. The effects of the flow field applied during the incubation on amyloid fibrillogenesis was discussed on the basis of the rate process consideration. The present results demonstrated that the flow field should be considered as an important factor that regulates the fibrillogenesis of globular proteins.