Huang QJ, Kim R, Song K, Grigorieff N, Munro JB, Schiffer CA, Somasundaran M. Virion-associated influenza hemagglutinin clusters upon sialic acid binding visualized by cryoelectron tomography. Proc Natl Acad Sci U S A. 2025 Apr 22; 122(16):e2426427122.