Jingli Yuan

Synthesis of a new tetradentate β-diketonate-europium chelate and its application for time-resolved fluorimetry of albumin

A new tetradentate beta-diketone chelator, 1,10-bis(8-chlorosulfo-dibenzothiophene-2-yl)-4,4,5,5,6,6,7,7, -octafluorodecane-1,3,8,10-tetraone (BCOT), was synthesized. This compound forms a stable chelate with europium (III) and can be used as a fluorescence label for time-resolved fluorescence spectrometry. BCOT can be covalently bound to a protein under relatively mild conditions and, when complexed with europium(III), both in 0.1 M Tris-HCl solution and 1.0 x 10(-5) M tri-n-octyl phosphine oxide (TOPO)-0.05% sodium n-dodecyl sulfate (SDS)-0.1 M NaHCO3 solution, forms a strongly fluorescent chelate having lifetimes of 225 microseconds and 240 microseconds, respectively. As a model reaction, bovine serum albumin (BSA) was labeled with BCOT in a carbonate buffer solution. Fluorescence properties of the labeled BSA solution were studied. A time-resolved fluorescence determination of the BSA(BCOT)40-Eu3+ solution was carried out. Detection limits of 9.3 x 10(-14) M (TOPO-SDS-NaHCO3 solution) and 6.7 x 10(-13) M (Tris-HCl solution) for BSA were obtained by the method.

Dual-label time-resolved fluoroimmunoassay of psychopharmaceuticals and stimulants in serum

A new method to measure two different drugs simultaneously by time-resolved fluoroimmunoassay (TR-FIA) has been developed. In the TR-FIA reported here, psychopharmaceuticals [chlorpromazine (CPZ) and desipramine (DSP)] and methamphetamine (MA) contained in serum are assayed by a combined use of a new europium (Eu) chelate and a samarium (Sm) chelate, as labels. The drug concentrations were determined by the competition between a labeled antigen with Eu(3+) or biotin and a sample antigen. A microtiter plate coated with a mixture of rabbit IgGs (anti-MA and anti-CPZ or anti-MA and anti-DSP) was used. In the assay of MA and CPZ, Eu(3+) labeled MA-bovine serum albumin conjugate (MA-BSA) and biotinylated CPZ-BSA were added to the well with their non-labeled standard solutions or samples. MA was assayed by measuring the fluorescence intensity of Eu(3+) at 615 nm. After incubation of the Sm(3+) labeled streptavidin, CPZ was assayed by measuring the fluorescence of Sm(3+) at 643 nm. In the assay of MA and DSP, Eu(3+) labeled DSP-BSA and biotinylated MA-BSA were used. In our dual-assay, the minimum detection limits of these drugs were 1ng/ml for MA, 10 ng/ml for CZP and 10 ng/ml for DSP. Since the simultaneous detection of different drugs by TR-FIA is time and sample saving, the method can be employed in rapid and sensitive screening tests.

Fluorescent Lanthanide Labels with Time-Resolved Fluorometry in DNA Analysis

Some lanthanide (Eu3+, Tb3+, Sm3+, and Dy3+) complexes are known to be luminescent. Compared with organic fluorescent compounds, the fluorescence of lanthanide chelates has several special different properties; (1) The lifetime of the lanthanide chelates is very long; that of europium(III) and terbium(III) chelates usually ranges from several hundred microseconds to more than one millisecond, and that of samarium(III) and dysprosium (III), 10 to 100 microseconds. (2) Stokes shifts are very large: the chelates are excited by UV light (310–350 nm) and emit fluorescence in the visible region. (3) The emission profiles are sharp, having a full width at half maximum (FWHM) of only ~10 nm.