Semi-quantitative dot blot analyses of m2-phage binding to gp120. Equal amounts of 5 different phages were applied to nitrocellulose filters (two fold serial dilutions) and reacted with rabbit anti-M13 polyclonal sera, or gp120 CDC451 followed by HIVIg or CG10 mAb as indicated. As is illustrated in the top filter, the amount of phages at each dilution for each of the five different phages is similar and the ECL signal drops as the phages are diluted (see densitometric quantification in the histogram on the right and Methods). The binding of gp120 and detection with CG10 is enhanced for phage 2A6 (obtained in standard biopanning) and markedly improved for m2-phage (obtained in stringent biopanning) compared to phage m1, as is detected in the filters and their subsequent densitometric scans (histograms on the right) which were performed for both HIVIg and CG10 at dilution 1:4. Peptide sequences: m1 – C-DRRDLPQWAKRE-C; 2A6 – C-DRRDLPQWAIRE-C; m2- C-DRRDLPDWAIRA-C; scrambled – C-DLWRIRADRAPD-C; fth-1 – no insert.