17O MAS NMR Correlation Spectroscopy at High Magnetic Fields

• Published in: Journal of the American Chemical Society Vol. 139; no. 49; pp. 17953 - 17963
• Main Authors: Keeler, Eric G, Michaelis, Vladimir K, Colvin, Michael T, Hung, Ivan, Gor’kov, Peter L, Cross, Timothy A, Gan, Zhehong, Griffin, Robert G
• Format: Journal Article
• Language: English
• Published: American Chemical Society 13.12.2017
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.7b08989

The structure of two protected amino acids, FMOC-l-leucine and FMOC-l-valine, and a dipeptide, N-acetyl-l-valyl-l-leucine (N-Ac-VL), were studied via one- and two-dimensional solid-state nuclear magnetic resonance (NMR) spectroscopy. Utilizing 17O magic-angle spinning (MAS) NMR at multiple magnetic fields (17.6–35.2 T/750–1500 MHz for 1H) the 17O quadrupolar and chemical shift parameters were determined for the two oxygen sites of each FMOC-protected amino acids and the three distinct oxygen environments of the dipeptide. The one- and two-dimensional, 17O, 15N–17O, 13C–17O, and 1H–17O double-resonance correlation experiments performed on the uniformly 13C,15N and 70% 17O-labeled dipeptide prove the attainability of 17O as a probe for structure studies of biological systems. 15N–17O and 13C–17O distances were measured via one-dimensional REAPDOR and ZF-TEDOR experimental buildup curves and determined to be within 15% of previously reported distances, thus demonstrating the use of 17O NMR to quantitate interatomic distances in a fully labeled dipeptide. Through-space hydrogen bonding of N-Ac-VL was investigated by a two-dimensional 1H-detected 17O R3-R-INEPT experiment, furthering the importance of 17O for studies of structure in biomolecular solids.