DNP-Supported Solid-State NMR Spectroscopy of Proteins Inside Mammalian Cells

Elucidating at atomic level how proteins interact and are chemically modified in cells represents a leading frontier in structural biology. We have developed a tailored solid-state NMR spectroscopic approach that allows studying protein structure inside human cells at atomic level under high-sensitivity dynamic nuclear polarization (DNP) conditions. We demonstrate the method using ubiquitin (Ub), which is critically involved in cellular functioning. Our results pave the way for structural studies of larger proteins or protein complexes inside human cells, which have remained elusive to in-cell solution-state NMR spectroscopy due to molecular size limitations.