Work

Peptide and Protein Dynamics and Low-Temperature/DNP Magic Angle Spinning NMR

Year: 2017

Type: article

Abstract: In DNP MAS NMR experiments at ∼80–110 K, the structurally important − 13 CH 3 and − 15 NH 3 + signals in MAS spectra of biological samples disappear due to the interference of the molecular motions with the 1 H decoupling. Here we investigate the effect of these dynamic processes on the NMR line shapes and signal intensities in several typical systems: (1) microcrystalline APG, (2) membrane protein bR, (3) amyloid fibrils PI3-SH3, (4) monomeric alanine-CD 3, and (5) the protonated and deuterated dipeptide N-Ac-VL over 78–300 K. In APG, the three-site hopping of the Ala-C β peak disappears completely at 112 K, concomitant with the attenuation of CP signals from other 13 C’s and 15 N’s. Similarly, the 15 N signal from Ala-NH 3 + disappears at ∼173 K, concurrent with the attenuation in CP experiments of other 15 N’s as well as 13 C’s. In bR and PI3-SH3, the methyl groups are attenuated at ∼95 K, while all other 13 C’s remain unaffected. However, both systems exhibit substantial losses of intensity at ∼243 K. Finally, with spectra of Ala and N-Ac-VL, we show that it is possible to extract site specific dynamic data from the temperature dependence of the intensity losses. Furthermore, 2 H labeling can assist with recovering the spectral intensity. Thus, our study provides insight into the dynamic behavior of biological systems over a wide range of temperatures, and serves as a guide to optimizing the sensitivity and resolution of structural data in low temperature DNP MAS NMR spectra.

Source: The Journal of Physical Chemistry B

DOI: 10.1021/acs.jpcb.7b02066