Cooperative protein-ligand antioxidant activation: Sulforaphane binding to human serum immunoglobulin Genhances neuroprotection in spinal cord neurons via structural and functional modifications.

Oxidative stress plays a central role in the progression of neurodegenerative damage, including spinal cord injury (SCI), where excessive reactive oxygen species (ROS) production leads to neuronal dysfunction and cell death. Although small-molecule antioxidants such as sulforaphane exhibit neuroprotective potential, their clinical efficacy is often limited by instability and poor bioavailability. In this study, we explore a cooperative protein-ligand strategy using human serum immunoglobulin G (HIgG) as a dynamic scaffold for sulforaphane binding and antioxidant modulation. An integrated experimental and computational approach combining multispectroscopy, molecular docking, molecular dynamics (MD) simulations, and in vitro neuronal assays was employed to characterize binding mechanism and antioxidant activity. Spectroscopic analyses confirmed spontaneous and moderately binding of sulforaphane to HIgG, primarily driven by hydrogen bonding and van der Waals interactions within the Fab region. MD simulations and CD data revealed that sulforaphane binding induces subtle but significant local conformational rearrangements in HIgG, enhancing solvent accessibility and flexibility of aromatic and redox-active residues. Functionally, in vitro experiments using spinal cord neurons under H₂O₂-induced oxidative stress demonstrated that the HIgG-sulforaphane complex provides significantly greater cytoprotection and ROS suppression than either component alone. In conclusion, these findings reveal a cooperative antioxidant mechanism in which HIgG-sulforaphane complex contribute to improved neuroprotective activity. This work highlights protein-ligand cooperativity as a promising strategy for designing next-generation antioxidant systems.