Proton-Selective 17O−H Distance Measurements in Fast Magic-Angle-Spinning Solid-State NMR Spectroscopy for the Determination of Hydrogen Bond Lengths

Abstract

We present a proton-selective method to determine 17O-1H distances in organic, biological, and biomimetic materials by fast magic-angle-spinning solid-state NMR spectroscopy. This method allows the determination of internuclear distances between specific (17O, 1H) spin pairs selectively. It enables the estimation of medium-range 17O...1H distances across hydrogen bonds in the presence of short-range 17O-1H contacts sharing the same 17O site. The method employs the newly developed symmetry-based radiofrequency pulse sequence SR%@mt;sys@%4%@sx@%1%@be@%2%@sxx@%%@mx@% applied to the protons to achieve heteronuclear dipolar recoupling, while simultaneously decoupling the homonuclear proton dipolar interactions. Fast MAS (50 kHz) and high static magnetic fields (18.8 T) achieve the required proton spectral resolution.