Perfluoro-tert-butyl-homoserine as a sensitive 19F NMR reporter for peptide-membrane interactions in solution.

Fluorine ((19)F) NMR is a valuable tool for studying dynamic biological processes. However, increasing the sensitivity of fluorinated reporter molecules is a key to reducing acquisition times and accessing transient biological interactions. Here, we evaluate the utility a novel amino acid, L-O-(perfluoro-t-butyl)-homoserine (pFtBSer), that can easily be synthesized and incorporated into peptides and provides greatly enhanced sensitivity over currently used (19)F biomolecular NMR probes. Incorporation of pFtBSer into the potent antimicrobial peptide MSI-78 results in a sharp (19)F NMR singlet that can be readily detected at concentrations of 5 µm and lower. We demonstrate that pFtBSer incorporation into MSI-78 provides a sensitive tool to study binding through (19)F NMR chemical shift and nuclear relaxation changes. These results establish future potential for pFtBSer to be incorporated into various proteins where NMR signal sensitivity is paramount, such as in-cell investigations.