title: Spectrophotometric method for the determination of a bifunctional DTPA ligand in DTPA-monoclonal antibody conjugates.
abstract: A simple spectrophotometric method was developed to quantitate micromolar concentrations of a bifunctional DTPA ligand in DTPA monoclonal antibody (mAb) conjugates. Titration of a brightly colored 1:2 yttrium (III) complex of arsenazo III with the ligand 1B4M-DTPA obeyed Beer's law over the concentration range 0-2.0 microM 1B4M-DTPA at 652 nm. From a calibration plot of absorbance versus 1B4M molarity, concentrations of 1B4M-DTPA conjugated to mAb were determined. Mole ratios of 1B4M-DTPA to mAb agreed satisfactorily with the ratios obtained by a radioanalytical technique using carbon-14-labeled 1B4M-DTPA and a binding assay using 111In. The spectrophotometric method was applied successfully to the preparation of 1B4M-DTPA mAb anti-TAC, a mAb conjugate used in clinical trials of 90Y radioimmunotherapy.
authors.affiliation: Chemistry Section, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: C G
authors.initials: CG
authors.lastname: Pippin
authors.forename: T A
authors.initials: TA
authors.lastname: Parker
authors.forename: T J
authors.initials: TJ
authors.lastname: McMurry
authors.forename: M W
authors.initials: MW
authors.lastname: Brechbiel
mesh_terms: D000911:Antibodies, Monoclonal / Q000032:analysis*; D007202:Indicators and Reagents; D008024:Ligands; D004369:Pentetic Acid / Q000032:analysis*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000911:Antibodies, Monoclonal; D007202:Indicators and Reagents; D008024:Ligands; D004369:Pentetic Acid