Peptide phage library amplification and selection. Phage work was performed as previously described [22]. The procedure for selection of cell-internalized phage was adapted from Gao et al [23]. Briefly, 4 × 1010 cfu of peptide phage library was added into 4 × 106 N2A
GW 0742 in 100 mm tissue culture dishes and incubated at 37 °C for 3 h. Cell screening of phage was stopped by immersion of dishes in ice for 10 min. The cells were stringently washed with Dulbecco’s phosphate buffered saline (DPBS), glycine buffer (50 mM glycine, 0.5 M NaCl,
pH 2.5) and PBS (pH 7.2), sequentially. Cells were lysed with 1 ml of 0.1 M triethylamine (TEA) and neutralized with 0.5 ml of 1 M Tris–HCl (pH 7.4). One milliliter of the cell lysate was used to amplify internalized peptide-phage as described above and used in the next round of selection. DNAs of 10 phage colonies from the fourth round of selection were prepared using the Wizard Plus SV Miniprep DNA Purification System (Promega) for sequence analysis.
