Fig. 3. Specificity of binding between isolated phage peptides and the tobacco W2 fraction proteins. (A) Competitive binding interactions between isolated tobacco W2 fraction proteins and KN1, CMV-MP and specific phage-displayed 12mer peptides. KN1 and CMV-MP were coated onto 6 nm gold particles and then used to determine specific protein interactions with the W2 cell fraction. Immobilized W2 fraction proteins (100 ng) were first incubated with the indicated probes (equimolar to the gold probe) and then subsequently competed with KN1-gold or CMV-MP-gold (0.2 µg). Note that experiments depicted on the left represent controls performed under the same conditions as described above for the phage peptide probes. (B) Ability of KN1pep_synth, CMVpep3_synth and random pep_synth gold probes (0.2 µg) to bind immobilized W2 fraction proteins. (C) Competitive binding between KN1-gold, CMV-MP-gold or ph-empty-gold (all present at 0.2 µg) and a 5× or 50× molar excess of KN1pep_synth. Immobilized W2 fraction proteins were incubated with a mixture of competitor and gold probe. Interaction of protein-gold probes was visualized by silver enhancement. Data were compiled from three to four replicates for each experiment, and represent relative pixel densities (after subtraction of background as measured with BSA-gold); mean ± SEM.