Figure 1.

a) Low-magnification TEM images of fd-phage bundles (Ca²⁺-phage) induced by addition of CaCl₂ solution (0.2 M) to phage solution. b) High-magnification TEM images of the Ca²⁺-(fd)phage bundles. c) EDS analysis of the formed Ca²⁺-(fd)phage bundles, which shows the presence of Ca and P. d) ζ potential of fd phage in aqueous solution under different concentrations of Ca²⁺, which shows a rapid decrease of ζ potential with increasing concentration of Ca²⁺.