No abstract

Structural evolution from monomer to fibril of amyloid β peptide is related to pathogenic mechanism of Alzheimer disease, and its acceleration is a long-running problem in drug development. This study reveals that ultrasonic cavitation bubbles behave as catalysts for nucleation of the peptide: The nucleation reaction is highly dependent on frequency and pressure of acoustic wave, and we discover an optimum acoustical condition, at which the reaction-rate constant for nucleation is increased by three-orders-of magnitudes. A theoretical model is proposed for explaining highly frequency and pressure dependent nucleation reaction, where monomers are captured on the bubble surface during its growth and highly condensed by subsequent bubble collapse, so that they are transiently exposed to high temperatures. Thus, the dual effects of local condensation and local heating contribute to dramatically enhance the nucleation reaction. Our model consistently reproduces the frequency and pressure dependences, supporting its essential applicability.

Background: Katanin p60 is a protein that actively severs microtubules. Results: Mutations within the AAAϩ pore of katanin p60 and in the C-terminal regions of tubulins perturb efficient microtubule severing. Conclusion: Interactions between the conserved residues in the katanin p60 pore and the acidic tails of both tubulins may be important. Significance: Both tubulin molecules are essential for microtubule severing by katanin.