Time Resolved Fluorescence

Time-resolved fluorescence (TRF) detection differs from fluorescence intensity (FI) in the timing of the excitation / emission (measurement) process. In case of standard FI the excitation and emission processes are within in a time frame of nanoseconds: here the light emitted by the sample is measured right after the excitation. Every fluophore has a fluorescence lifetime and the decay curve of the excitation wavelength energy will contribute differently to the background activity of the emission wavelength being measured. To alleviate this problem background fluorescence needs to be minimized and this can be accomplished by the use of long-lifetime fluorophores, namely lanthanides such as Europium, Terbium and Samarium. Lanthanides have an unusual property of emitting light over long periods of time after excitation - up to milliseconds rather than nanoseconds in standard FI. This leads to much lower background activity and better results. Lanthanides are excited either by a high power xenon flash lamp or by a pulsed laser source. The main use of TRF is found in high-throughput screening applications, clinical diogagnostics (DELFIA®), drug discovery and cell based assays.

BMG LABTECH's microplate readers have a unique Decay Curve Monitoring feature, a special assay development tool for time-resolved fluorescence, TR-FRET and AlphaScreen® assays. This technology is an indispensable tool for troubleshooting an assay or for fine-tuning parameters for optimal performance.

BMG LABTECH has published numerous application notes (AN) on using time-resolved fluorescence detection mode with various BMG LABTECH microplate readers including:

• Assessing Microbial Metabolism Using A Simple "Mix & Measure" Oxygen Consumption Assay (AN 207)
• A DELFIA® time-resolved fluorescence cell-mediated cytotoxicity assay performed on the PHERAstar (AN 192)

The following BMG LABTECH microplate readers can be configured to perform time-resolved fluorescence measurements: