Deuteron Solid‐State NMR Relaxation Measurements Reveal Two Distinct Conformational Exchange Processes in the Disordered N‐Terminal Domain of Amyloid‐β Fibrils. Issue 13 (14th June 2019)

• Record Type: Journal Article
• Authors: Vugmeyster, Liliya; Au, Dan Fai; Ostrovsky, Dmitry; Fu, Riqiang
• Is Part Of: Chemphyschem. Volume 20:Issue 13(2019)
• Page Start: 1680
• Page End: 1689
• Publication Date: 2019-06-14
• Subjects: amyloid fibrils -- CPMG relaxation -- quadrupolar interactions -- rotating frame relaxation -- solid-state NMR; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201900363
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: We employed deuterium solid‐state NMR techniques under static conditions to discern the details of the μs–ms timescale motions in the flexible N‐terminal subdomain of Aβ1–40 amyloid fibrils, which spans residues 1–16. In particular, we utilized a rotating frame ( R 1ρ ) and the newly developed time domain quadrupolar Carr‐Purcell‐Meiboom‐Gill (QCPMG) relaxation measurements at the selectively deuterated side chains of A2, H6, and G9. The two experiments are complementary in terms of probing somewhat different timescales of motions, governed by the tensor parameters and the sampling window of the magnetization decay curves. The results indicated two mobile "free" states of the N‐terminal domain undergoing global diffusive motions, with isotropic diffusion coefficients of 0.7−1 ⋅ 10 8 and 0.3−3 ⋅ 10 6 ad 2 s −1 . The free states are also involved in the conformational exchange with a single bound state, in which the diffusive motions are quenched, likely due to transient interactions with the structured hydrophobic core. The conformational exchange rate constants are 2−3 ⋅ 10 5 s −1 and 2−3 ⋅ 10 4 s −1 for the fast and slow diffusion free states, respectively. Abstract : Covering different timescales : We employed deuterium solid‐state NMR techniques under static conditions to discern the details of the μs‐ms timescale motions in the flexible N‐terminal subdomain of Aβ1–40 amyloid fibrils using quadrupolar CPMG and rotating frame relaxation. The two experiments are complementary in terms of probing somewhat different timescales of motions. The results indicated two mobile "free" states of the N‐terminal domain undergoing global diffusive motions and conformational exchange with a single bound state.