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Phenyl-Ring Dynamics in Amyloid Fibrils and Proteins: The Microscopic-Order-Macroscopic-Disorder Perspective.

ABSTRACT: We have developed the microscopic-order-macroscopic-disorder (MOMD) approach for studying internal mobility in polycrystalline proteins with 2H lineshape analysis. The motion itself is expressed by a diffusion tensor, R, the local spatial restraints by a potential, u, and the "local geometry" by the relative orientation of the model-related and nuclear magnetic resonance-related tensors. Here, we apply MOMD to phenyl-ring dynamics in several ??40-amyloid-fibrils, and the villin headpiece subdomain (HP36). Because the available data are limited in extent and sensitivity, we adjust u and R in the relevant parameter ranges, fixing the "local geometry" in accordance with standard stereochemistry. This yields a physically well-defined and consistent picture of phenyl-ring dynamics, enabling comparison between different systems. In the temperature range of 278-308 K, u has a strength of (1.7-1.8) kT and a rhombicity of (2.4-2.6) kT, and R has components of 5.0 × 102 ? R? ? 2.0 × 103 s-1 and 6.3 × 105 ? R? ? 2.0 × 106 s-1. At 278 K, fibril hydration increases the axiality of both u and R; HP36 hydration has a similar effect at 295 K, reducing R? considerably. The D23N mutation slows down the motion of the probe; A?40 polymorphism affects both this motion and the related local potential. The present study identifies the impact of various factors on phenyl-ring mobility in amyloid fibrils and globular proteins; the difference between the two protein forms is considerable. The distinctive impact of hydration on phenyl-ring motion and previously studied methyl-group motion is also examined. The 2H lineshapes considered here were analyzed previously with various multi-simple-mode (MSM) models, where several simple motional modes are combined. The MOMD and MSM interpretations differ in essence.

SUBMITTER: Meirovitch E

PROVIDER: S-EPMC6174686 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Phenyl-Ring Dynamics in Amyloid Fibrils and Proteins: The Microscopic-Order-Macroscopic-Disorder Perspective.

Meirovitch Eva E Liang Zhichun Z Freed Jack H JH

The journal of physical chemistry. B 20180910 37

We have developed the microscopic-order-macroscopic-disorder (MOMD) approach for studying internal mobility in polycrystalline proteins with <sup>2</sup>H lineshape analysis. The motion itself is expressed by a diffusion tensor, R, the local spatial restraints by a potential, u, and the "local geometry" by the relative orientation of the model-related and nuclear magnetic resonance-related tensors. Here, we apply MOMD to phenyl-ring dynamics in several Αβ<sub>40</sub>-amyloid-fibrils, and the vi ...[more]

PMID: 30141954

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Dataset Information

Phenyl-Ring Dynamics in Amyloid Fibrils and Proteins: The Microscopic-Order-Macroscopic-Disorder Perspective.

Publications

Phenyl-Ring Dynamics in Amyloid Fibrils and Proteins: The Microscopic-Order-Macroscopic-Disorder Perspective.

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