Fluorescent chelates for monitoring metal binding with macromolecules

M. Islam, M. Khanin, O. A. Sadik

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Metals and radionuclides are usually coupled with proteins together with suitable ligands for therapeutic, tumor-imaging, pharmaceuticals, and biocompatibility applications. Several ligands that can strongly coordinate a given nuclide in a specific valency are already known. However, the demand for bifunctionality has limited the applications of these ligands. We hereby report the molecular design of a receptor system based on the linkage of protein to monoazo ligands. By use of basic coordination chemistry, 4-(3-quinolinoazo) hydroxybenzoic acid (QABA) and derivatives were successfully conjugated to ovalbumin, bovine serum albumin, and alkaline phsophatase at a site that was distinct from the metal binding site. The presence of carboxylic acid linkage in the QABA served as a convenient bridge for protein conjugation and may allow the generic application of these ligands for bioconjugate synthesis while ensuring a high in vivo stability. The ligand-protein conjugates were characterized using UV-vis spectroscopy, Fourier transform infrared spectroscopy, thin layer charoatography, NMR, and surface-enhanced laser desorption ionization time-of-flight mass spectrometry. The conjugate was tested for the ability to recognize nonradioactive Ga3+ at a physiological pH, and a binding constant of 1 × 1020 was recorded. Also, the in vitro testing results indicated that the fluorescent conjugates exhibited significant selectivity for gallium compared to Pb2+, Hg2+, Zn2+, Cu2+, Fe3+, and Co2+ while no responses were obtained for alkaline and alkaline earth metals. These attributes could allow these conjugates to be used as a model for imaging sensors and for metal detection.

Original languageEnglish (US)
Pages (from-to)114-121
Number of pages8
Issue number1
StatePublished - Jan 2003
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Biomaterials
  • Polymers and Plastics
  • Materials Chemistry


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