Aim:To perform a site-specific conjugation of Fab’ fragments of a mouse mono-clonal antibody(MoAb)B43(of IgG_1 subtype)to a bifunctional chelator 6-[p-(bromoacetamido)benzyl]-1,4,8,11-tetraazacyclotetradecane-N,N′,N″,N′″-tetraacetic acid(BAT)via the thiol groups in the hinge distal to the antigen-binding site of the Fab~1.Methods:B43 was cleaved using a simple 2-step method.First,stable F(ab~1)_2 was produced by pepsin treatment.Fab~1 with tree thiol in thehinge region was then obtained by cysteine reduction of F(ab~1)_2.Second,a site-specific conjugation of Fab~1 to thiol-specific BAT was performed in a one-stepreaction.Results:The Fab~1 fragment had approximately 1.8 free thiol groups permolecule after cysteine reduction.The conjugation efficiency and the chemicalyield were approximately 1.28 moles chelator/Fab′ and 74% of the initial concentra-tion of Fab′,respectively.The F(ab′)_2,Fab′ and Fab′-BAT all maintained reason-able antigen-binding properties.~(67)Cu labeling of the conjugate under standardconditions did not impair the immunoreactivity of Fab′-BAT.Conclusion:This isa simple and efficient method for producing immunoreactive conjugates of Fab′-BAT,which can be used to make radiometal-labeled conjugates for further diag-nostic and therapeutic applications. Aim: To perform a site-specific conjugation of Fab ’fragments of a mouse mono-clonal antibody (MoAb) B43 (of IgG_1 subtype) to a bifunctional chelator 6- [p- (bromoacetamido) benzyl] -1,4,8, 11-tetraazacyclotetradecane-N, N ’, N “, N’” - tetraacetic acid (BAT) via the thiol groups in the hinge distal to the antigen-binding site of the Fab ~ 1. Methods: B43 was cleaved using a simple 2 -step method.First, stable F (ab ~ 1) _2 was produced by pepsin treatment. Fab ~ 1 with tree thiol in the home region was then obtained by cysteine ​​reduction of F (ab ~ 1) _2.Second, a site-specific conjugation of Fab ~ 1 to thiol-specific BAT was performed in a one-step reaction. Results: The Fab ~ 1 fragment had approximately 1.8 free thiol groups permolecule after cysteine ​​reduction. The conjugation efficiency and the chemical field were approximately 1.28 moles chelator / Fab ’ and 74% of the initial concentration of Fab ’, respectively. The F (ab’) _2, Fab ’and Fab’-BAT all maintained reasonably able antigen-binding properties. ling of the conjugate under standard conditions did not impair the immunoreactivity of Fab’-BAT.Conclusion: This isa simple and efficient method for producing immunoreactive conjugates of Fab’-BAT, which can be used to make radiometal-labeled conjugates for further diag-nostic and therapeutic applications.