Patent ID: 7214545

Claim:
A method for comparing the quantity of a biomolecule between a first sample and a second sample, said method comprising: (a) contacting said first sample with a first tag moiety comprising a complex between a first metal ion and a macrocyclic chelating agent, thereby forming a first adduct between said biomolecule and said first tag moiety; (b) contacting said second sample with a second tag moiety comprising a complex between a second metal ion and said macrocyclic chelating agent, thereby forming a second adduct between said biomolecule and said second tag moiety; wherein said first metal ion and said second metal ion are different; wherein said macrocyclic chelating has Formula (Ia): wherein each of L 1 , L 2 , L 3 and L 4 are linking groups independently selected from C 2-5 alkylene which is optionally substituted with one to three substituents selected from the group consisting of substituted and unsubstituted alkyl, substituted and unsubstituted heteroalkyl and substituted and unsubstituted aryl; each of R N1 , R N2 , R N3 and R N4 are independently selected from the group consisting of substituted and unsubstituted alkyl, substituted and unsubstituted heteroalkyl and substituted and unsubstituted aryl; wherein at least one of L 1 , L 2 , L 3 , L 4 , R N1 , R N2 , R N3 and R N4 has a functional group suitable for attachment to said biomolecule; and (c) contacting said first adduct and said second adduct with an affinity medium comprising a first binding moiety that binds said first tag moiety and said second tag moiety; and (d) eluting said first adduct and said second adduct from said affinity medium, thereby forming a solution comprising said first adduct and said second adduct; and (e) comparing the quantity of said first adduct to the quantity of said second adduct, thereby comparing the quantity of said biomolecule between said first sample and said second sample.