Characterization of In Vitro Amyloid Fibril Formation from Bovine Serum Albumin and Gamma Globulin Using Thioflavin T Flourescence and Polyacrylamide Gel Electrophoresis

Amyloid fibrils are insoluble protein aggregates that disrupt normal cell functions causing over 20 serious human diseases including Alzheimer\u27s disease, Parkinson\u27s disease, and diabetic amyloidosis. In an effort to study formation and degradation of amyloid fibrils, we studied the in vitro formation of amyloid fibrils using bovine serum albumin_and gamma globulin and the inhibitory effects of epigallocatechin gallate and gallic acid using fluorescence studies and polyacrylamide gel electrophoresis. Thioflavin T binds to amyloid fibrils and shows characteristic fluorescence. The fluorescence spectra of thioflavin T-bound gamma globulin amyloid fibrils showed the excitation maximum of 420 nm and the emission maximum of 482 nm. We studied the formation of gamma globulin amyloid fibrils at pH levels ranging from 2 to 7. The formation of gamma globulin amyloid fibrils was accelerated at low pH (pH 2-3.5) at 25oC without the addition of seed fibrils. The amyloid formation was directly dependent of protein concentration and the optimum protein concentration was 0.1 - 0.8 mg/ml without a lag phase. Centrifugation at 14,000 G for 10 minutes or filtration using 0.2 micrometer filters did not significantly remove amyloid fibrils as evidenced by polyacrylamide gel electrophoresis. We tested different concentrations of epigallocatechin gallate and gallic acid to determine the effect they would have on the formation of the fibrils. Gallic acid had no effect on the formation whereas epigallocatechin gallate accelerated the formation of the fibrils