In our previous study, we demonstrated that the inhibitory activity of 3HP-β-LG on HPV PsV entry into the target cell is closely correlated with the number of the positively charged lysine and arginine residues in 3HP-β-LG, as modified, i.e., the net negative charges on 3HP-β-LG (Lu et al., 2013) , suggesting that the negatively charged residues on 3HP-β-LG play an important role in 3HP-β-LG-mediated inhibition of HPV infection.