Effect of the\nProtein Chain\nConformation on the Collapse into Nanoparticles

Protein single-chain nanoparticles can outperform synthetic\nnanoparticles\nin biomedical applications due to enhanced biocompatibility. Compared\nto synthetic (co)polymers, the chemical complexity of proteins challenges\nchain conformation control. Here, we investigate the impact of the\nprecursor chain conformation of bovine serum albumin (BSA) on the\nnanoparticle structure after intramolecular cross-linking. We explore\nthe urea concentration (denaturant), pH, salt, cross-linker length,\nand concentration. Small-angle neutron scattering and dynamic light\nscattering experiments reveal a shrinking chain conformation upon\ncross-linking. However, the ability to collapse depends on solvent\nconditions: more expanded chains collapse more, whereas proteins that\nare already compact barely change in size upon cross-linking. Static\nlight scattering measurements demonstrate that binding is primarily\nintramolecular. The use of a shorter cross-linker does not lead to\ncollapse of extended chains. Overall, BSA exhibits a similar behavior\nto that of polymer nanoparticles, which then allows to harness the\nprecursor conformation for morphological control.