Figure 4.

UV-visible protein direct-absorption spectra of the BNC and various controls, acquired between the 200 to 310 nm spectral region, to determine protein presence, as well as amide and disulphide bond confirmation. (a) amine NH₂ 195 nm group on Ab n’ terminal, (b) amine NH₂ 195 nm group on functionalized AuNPPEG-NH₂, (c) amine NH₂ 195 nm group on final conjugate Ab n’ terminal (Ab functional), (d) peptide/amide bond 220 nm of final conjugate (functionalized AuNPPEG-NH₂ lost amine group to bond with carboxyl c’ terminus of Ab and form a peptide bond), (e) disulphide bond 250 to 280 nm (ligand exchange process was performed in the presence of air and, thus, caused ZnPcS₄ to form a dimer), and (f) anti-GCC Ab protein 280 nm 200 µg/mL (6.47 times higher absorbance than final BNC conjugate, thereby suggesting final concentration of Ab within the BNC molecule was 30.91 µg/mL).