Title
Drastic acceleration of fibrillation of insulin by transient cavitation bubble
Author
Kichitaro Nakajima, Daisuke Nishioka, Masahiko Hirao, Masatomo So, Yuji Goto, Hirotsugu Ogi
Year
2017
Journal
Ultrasonics Sonochemistry
Abstract
Amyloid-fibril formation of proteins can be accelerated by ultrasonic irradiation to the peptide solutions. Although this phenomenon contributes to understanding pathogenic behavior of amyloidosis, its physical mechanism has not been clarified, because several factors (cavitation, temperature increase, stirring effect, and so on) related to ultrasonic irradiation can participate in the fibrillation reaction. Here, we independently study contributions of the possible factors, using insulin, which is extremely stable and then suitable for the mechanism clarification. We find that the optimized ultrasonic irradiation can drastically accelerate the fibrillation reaction; the time for completing the reaction is shortened compared with the high-speed (1200 rpm) stirring agitation by a factor of 430. The fibrillation reaction proceeds only when the subharmonic-mode intensity exceeds a threshold, indicating generation of the transient cavitation bubbles. Our results reveal that not the temperature increase but the transient cavitation bubbles work as the dominant accelerator of the fibrillation reaction.
Instrument
FP-6200
Keywords
Fluorescence, Aggregation, Thermal stability, Kinetics, Materials