Controlled release of doxorubicin release from drug-carrying phages. A. The sequence amino-acid sequence (single-letter code) of the g8p coat protein of fUSE5-ZZ-(p8)DFK phages (top) and native fUSE5 (bottom). The mutated residues are marked by black arrows. B. Drawing (not to scale) of a single fUSE5-ZZ-(p8)DFK phage; In the phage scheme on the right, small turquoise spheres represent major coat protein g8p monomers. Purple spheres and sticks represent the 5 copies of minor coat protein g3p, which is fused to a three-color helix representing the IgG binding ZZ domain. The Y shaped structure represents complexed IgG. An engineered g8p monomer is shown on the left. The helix represents a partial structure of a single major coat protein p8, conjugated through an amino terminal aspartate (D) of the sequence DFK carboxyl side chains a molecule of doxorubicin (red). C. A Photograph of the cathepsin-B release experiment tubes, on the right, doxorubicin carrying fUSE5-ZZ-(p8)DFK phages that was incubated with cathepsin-B, followed by PEG/NaCl precipitation, a reddish soluble D-DOX (verified by HPLC and MS in Fig. 5) is seen as well as a reddish pellet representing the drug conjugated through the internal glutamate residue. On the left is a tube containing fUSE5-ZZ phages that was incubated with cathepsin-B, followed by PEG/NaCl precipitation, the transparent colorless solution indicate no drug release.