Comparative Study of REDOR and CPPI Derived Order Parameters by (1)H-Detected MAS NMR and MD Simulations.
 

Comparative Study of REDOR and CPPI Derived Order Parameters by (1)H-Detected MAS NMR and MD Simulations.

Comparative Study of REDOR and CPPI Derived Order Parameters by (1)H-Detected MAS NMR and MD Simulations.

J Phys Chem B. 2017 Aug 25;:

Authors: Asami S, Reif B

Abstract
The measurement of dipolar couplings among directly bonded nuclei yields direct information on the amplitude of dynamic processes in the solid-state. For a reliable motional analysis using e.g. the model-free approach, a correct quantification of the absolute values of these order parameters is absolutely essential. In the absence of a reference value for the rigid limit, too low dipolar coupling values might be misinterpreted as motion. Therefore, a detailed understanding of the experimental effects that influence the quantification of order parameters is necessary. We compare here experimentally REDOR and CPPI derived order parameters assessed in 1H detected experiments, and discuss the influence of remote protons and rf inhomogeneity on the extracted dipolar coupling constant for MAS rotation frequencies in the range of 20-100 kHz. Experimental results are furthermore compared with the order parameter obtained from a molecular dynamics simulation. We find that fast magic-angle spinning up to 100 kHz can yield artifact free REDOR based 1H,15N order parameters for perdeuterated and 100 % amide back-exchanged proteins, and even in uniformly protonated samples. We believe, that awareness on systematic errors introduced by the measurement and in the analysis of order parameters will yield a better understanding of the dynamic properties of a protein derived from solid-state NMR observables.


PMID: 28841025 [PubMed - as supplied by publisher]



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