title: Fluorescent chelates for monitoring metal binding with macromolecules.
abstract: 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 phosphatase 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 chromatography, NMR, and surface-enhanced laser desorption ionization time-of-flight mass spectrometry. The conjugate was tested for the ability to recognize nonradioactive Ga(3+) at a physiological pH, and a binding constant of 1 x 10(20) was recorded. Also, the in vitro testing results indicated that the fluorescent conjugates exhibited significant selectivity for gallium compared to Pb(2+), Hg(2+), Zn(2+), Cu(2+), Fe(3+), and Co(2+) 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.
authors.affiliation: Department of Chemistry, State University of New York at Binghamton, PO Box 6016, Binghamton, New York 13902-6016, USA.
authors.forename: M
authors.initials: M
authors.lastname: Islam
authors.forename: M
authors.initials: M
authors.lastname: Khanin
authors.forename: O A
authors.initials: OA
authors.lastname: Sadik
mesh_terms: D002138:Calibration; D002614:Chelating Agents; D005456:Fluorescent Dyes; D009682:Magnetic Resonance Spectroscopy; D008670:Metals / Q000737:chemistry* / Q000493:pharmacokinetics; D010047:Ovalbumin / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry* / Q000493:pharmacokinetics; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D002614:Chelating Agents; D005456:Fluorescent Dyes; D008670:Metals; D011506:Proteins; D010047:Ovalbumin