Localization of Cl-35 Nuclei in Biological Solids using Rotational-Echo Double-Resonance Experiments (Reprinted from Solid State Nuclear Magnetic Resonance, vol 84, pg 242-248, 2017)

Chloride ions play important roles in many chemical and biological processes. This paper investigates the possibility of localizing Cl-35 nuclei using solid-state NMR. It demonstrates that distances shorter than 3.8 angstrom, between C-13 atoms and Cl-35 atoms in 10% uniformly labeled C-13 L-tyrosine center dot HCl and natural abundance Glycine center dot HCl can be measured using rotational-echo (adiabatic passage) double-resonance (RE(AP)DOR). Furthermore the effect of quadrupolar interaction on the REDOR/REAPDOR experiment is quantified. The dephasing curve is plotted in a three dimensional chart as a function of the dephasing time and of the strength of quadrupolar interaction felt by each orientation. During spinning each orientation feels a quadrupolar interaction that varies in time, and therefore at each moment in time we reorder the crystallite orientations as a function of their contribution to the dephasing curve. In this way the effect of quadrupolar interaction on the dipolar dephasing curve can be fitted with a polynomial function. The numerical investigation performed allows us to generate REDOR/REAPDOR curves which are then used to simulate the experimental data. (C) 2017 Elsevier Inc. All rights reserved.