jz6b02088_si_liveslides.zip (7.51 MB)
Water Rearrangements upon Disorder-to-Order Amyloid Transition
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posted on 2016-10-12, 15:34 authored by Shruti Arya, Avinash
K. Singh, Tuhin Khan, Mily Bhattacharya, Anindya Datta, Samrat MukhopadhyayWater plays a critical role in governing
the intricate balance
between chain-chain and chain-solvent interactions during protein
folding, misfolding, and aggregation. Previous studies have indicated
the presence of different types of water in folded (globular) proteins.
In this work, using femtosecond and picosecond time-resolved fluorescence
measurements, we have characterized the solvation dynamics from ultrafast
to ultraslow time scale both in the monomeric state and in the amyloid
state of an intrinsically disordered protein, namely κ-casein.
Monomeric κ-casein adopts a compact disordered state under physiological
conditions and is capable of spontaneously aggregating into highly
ordered β-rich amyloid fibrils. Our results indicate that the
mobility of “biological water” (type I) gets restrained
as a result of conformational sequestration during amyloid formation.
Additionally, a significant decrease in the bulk water component with
a concomitant increase in the ultraslow component revealed the ordering
of trapped interstitial water (type II) upon disorder-to-order amyloid
transition. Our results provide an experimental underpinning of significant
water rearrangements associated with both chain desolvation and water
confinement upon amyloid formation.