Competing transfer pathways in direct and indirect dynamic nuclear polarization magic anglespinning nuclear magnetic resonance experiments on HIV-1 capsid assemblies: implications for sensitivity and resolution

Abstract. Dynamic nuclear polarization (DNP)-enhanced magic angle spinning (MAS) magnetic resonance (NMR) of biological systems is a rapidly growing field. Large signal enhancements make the technique particularly attractive for signal-limited cases, such as studies complex assemblies or at natural isotopic abundance. However, spectral resolution considerably reduced compared to ambient-temperature non-DNP spectra. Herein, we report systematic investigation into sensitivity and 1D 2D 13C-detected DNP MAS NMR experiments on HIV-1 CA capsid protein tubular assemblies. We show that magnitude sign enhancement well homogeneous line width are strongly dependent biradical concentration, dominant transfer pathway, buildup time. Our findings provide guidance optimal choice sample preparation experimental conditions in experiments.