Racing toward Fast and Effective 17O Isotopic Labeling and Nuclear Magnetic Resonance Spectroscopy of N-Formyl-MLF-OH and Associated Building Blocks

Solid-state H-1, C-13, and N-15 nuclear magnetic resonance (NMR) spectroscopy has been an essential analytical method in studying complex molecules and biomolecules for decades. While oxygen-17 (O-17) NMR is an ideal and robust candidate to study hydrogen bonding within secondary and tertiary protein structures for example, it continues to elude many. We discuss an improved multiple-turnover labeling procedure to develop a fast and cost-effective method to O-17 label fluoroenylmethyloxycarbonyl (Fmoc)-protected amino acid building blocks. This approach allows for inexpensive ($0.25 USD/mg) insertion of O-17 labels, an important barrier to overcome for future biomolecular studies. The O-17 NMR results of these building blocks and a site-specific strategy for labeled N-acetyl-MLF-OH and N-formyl-MLF-OH tripeptides are presented. We showcase growth in NMR development for maximizing sensitivity gains using emerging sensitivity enhancement techniques including population transfer, high-field dynamic nuclear polarization, and cross-polarization magic-angle spinning cryoprobes.

Automated summary

Solid-state H-1, C-13, and N-15 nuclear magnetic resonance (NMR) spectroscopy has been essential in studying complex molecules and biomolecules, while oxygen-17 (O-17) NMR is a challenging yet ideal method for studying hydrogen bonding. By improving labeling procedures, a cost-effective O-17 labeling method has been developed, overcoming a key barrier in biomolecular studies. Additionally, advancements in NMR development for sensitivity enhancement techniques are showcased for future research.