Strategies for labeling proteins with PARACEST agents

Olga Vasalatiy, Piyu Zhao, Mark Woods, Andrei Marconescu, Aminta Castillo-Muzquiz, Philip Thorpe, Garry E. Kiefer, A. Dean Sherry

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Reactive surface lysine groups on the monoclonal antibody (3G4) and on human serum albumin (HSA) were labeled with two different PARACEST chelates. Between 7.4 and 10.1 chelates were added per 3G4 molecule and between 5.6 and 5.9 chelates per molecule of HSA, depending upon which conjugation chemistry was used. The immunoreactivity of 3G4 as measured by ELISA assays was highly dependent upon the number of attached chelates: 88% immunoreactivity with 7.4 chelates per antibody versus only 17% immunoreactivity with 10.1 chelates per antibody. Upon conjugation to 3G4, the bound water lifetime of Eu-1 increased only marginally, up from 53 μs for the non-conjugated chelate to 65-77 μs for conjugated chelates. Conjugation of a chelate Eu-2 to HSA via a single side-chain group also resulted in little or no change in bound water lifetime (73-75 μs for both the conjugated and non-conjugated forms). These data indicate that exchange of water molecules protons between the inner-sphere site on covalently attached PARACEST agent and bulk water is largely unaffected by the mode of attachment of the agent to the protein and likely its chemical surroundings on the surface of the protein.

Original languageEnglish (US)
Pages (from-to)1106-1114
Number of pages9
JournalBioorganic and Medicinal Chemistry
Issue number3
StatePublished - Feb 1 2011
Externally publishedYes


  • 3G4 Monoclonal antibody
  • Bifunctional PARACEST agents
  • Bound water lifetimes
  • Eu chelates
  • HSA

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Medicine
  • Molecular Biology
  • Pharmaceutical Science
  • Drug Discovery
  • Clinical Biochemistry
  • Organic Chemistry


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