The present invention relates to a peptide having one or more stable, internally-constrained HBS α-helices, where the peptide mimics at least a portion of a class I C-peptide helix or at least a portion of a class I N-peptide helix of a viral (e.g., HIV-I) coiled-coil assembly. Methods of inhibiting viral infectivity of a subject by administering these peptides are also disclosed.