Radiolabeling of phosphatidylserine-binding peptides with prosthetic groups N-[6-(4-[¹⁸F]fluorobenzylidene)aminooxyhexyl]maleimide ([¹⁸F]FBAM) and N-succinimidyl-4-[¹⁸F]fluorobenzoate ([¹⁸F]SFB)

The widely used (¹⁸)F-prosthetic group N-succinimidyl-4-[(¹⁸)F]fluorobenzoate ([(¹⁸)F]SFB) and the recently developed N-[6-(4-[(¹⁸)F]fluorobenzylidene)aminooxyhexyl]maleimide ([(¹⁸)F]FBAM) were investigated for radiolabeling of two representative phosphatidylserine-binding peptides. The prosthetic groups were compared with respect to required reactions conditions for optimum labeling, radiolabeling yield and chemoselectivity. The N-terminus labeled product produced by reaction of [(¹⁸)F]SFB with binding peptide LIKKPF was produced in 18% radiochemical yield while no N-terminus labeled product could be isolated following [(¹⁸)F]SFB reaction with PDGLSR. When the peptides were modified by addition of a cysteine residue at the N-terminus they provided almost quantitative radiochemical yields with [(¹⁸)F]FBAM. Results indicate that for the peptides in this study, [(¹⁸)F]FBAM is a more useful prosthetic group compared to [(¹⁸)F]SFB due to its excellent chemoselectivity and high radiochemical yield.