Transferrin-terbium complexes as luminescent pH sensing devices.
Three kinds of protein-metal complexes were developed as pH sensing devices in the aqueous solutions. Biological transferrin and lactoferrin proteins formed stable Tb3+ complexes, which exhibited long-lived and green luminescence signals. They showed pH-dependent luminescence changes around neutral pH, coupled with their Tb3+ complexation/decomplexation. Since fluorescein-labeled transferrin-Fe3+ complex exhibited fluorescence changes at lower pH, these three protein complexes covered wide pH-responsive ranges. The immobilized biotinylated transferrin-Tb3+ complexes on the micrometer-scaled bead also operated as a pH-responsive luminescent indicator. Since the transferrin ligand had rapid Tb3+ complexation/decomplexation process, its Tb3+ complex exhibited pH-responsive luminescence signals even in the presence of Fe3+ cation. A new series of tunable luminescent pH sensing devices were developed by combination of biological protein and luminescent lanthanide center.
Department of Chemistry, Graduate School of Science, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan.
Yumiko
Y
Kataoka
Satoshi
S
Shinoda
Hiroshi
H
Tsukube