| Popis: |
The dynamics of amyloid fibrils, including their formation and dissociation, could be of vital importance in life. We studied the kinetics of dissociation of the amyloid fibrils from wild-type hen lysozyme at 25°C in vitro as a function of pressure using Trp fluorescence as a probe. Upon 100-fold dilution of 8 mg ml(-1) fibril solution in 80 mM NaCl, pH 2.2, no immediate change occurred in Trp fluorescence, but at pressures of 50-450 MPa the fluorescence intensity decreased rapidly with time (k(obs) = 0.00193 min(-1) at 0.1 MPa, 0.0348 min(-1) at 400 MPa). This phenomenon is attributable to the pressure-accelerated dissociation of amyloid fibrils into monomeric hen lysozyme. From the pressure dependence of the rates, which reaches a plateau at ~450 MPa, we determined the activation volume ΔV(0‡) = -32.9 ± 1.7 ml mol(monomer)(-1) and the activation compressibility Δκ(‡) = -0.0075 ± 0.0006 ml mol(monomer)(-1) bar(-1) for the dissociation reaction. The negative ΔV(0‡) and Δκ(‡) values are consistent with the notion that the amyloid fibril from wild-type hen lysozyme is in a high-volume and high-compressibility state, and the transition state for dissociation is coupled with a partial hydration of the fibril. |
