Faglia, F. et. al., Adv. Sci., 2025, e10909, https://doi.org/10.1002/advs.202510909
Single-chain nanoparticles (SCNPs) are formed by the collapse of individual polymer chains, forming internalized compartments, reminiscent of pockets in enzymes. Using a synergistic combination of unconventional paramagnetic NMR, hyperpolarized water-based dissolution dynamic nuclear polarization (d-DNP), and NMR-guided molecular dynamics simulations, intramolecular structures and solvent accessibility are mapped at atomistic resolution. These findings uncover distinct nanoscopic compartments formed via back-folding of PEG side chains toward the SCNP backbone. At the same time, this method’s prowess is evidenced through a high-resolution description of the local conformations found within hierarchically structured SCNPs. © 2025 The Author(s). Advanced Science published by Wiley‐VCH GmbH. Open access.