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Luminescence Resonance Energy Transfer to Study Conformational Changes in Membrane Proteins Expressed in Mammalian Cells
Published on: September 16, 2014
Time-resolved luminescence energy transfer immunobinding study using a ruthenium-ligand complex as a donor label
Christine M Augustin1, Bernhard Oswald, Otto S Wolfbeis
1Institute of Analytical Chemistry, University of Regensburg, Regensburg, D-93040, Germany.
Insights
A new immunosystem uses luminescent energy transfer between labeled antigen and antibody. This novel approach enhances detection sensitivity and offers a distinct advantage over existing methods for antigen-antibody complex analysis.
Area of Science:
- Biochemistry
- Immunology
- Analytical Chemistry
Background:
- Immunosystems are crucial for detecting antigen-antibody interactions.
- Existing methods often face limitations in sensitivity and detection speed.
- Novel labeling strategies are needed to improve immunosystem performance.
Purpose of the Study:
- To develop and characterize a novel immunosystem utilizing luminescence energy transfer (LET).
- To investigate the application of a ruthenium-ligand complex as a donor and a cyanine dye as an acceptor in an antigen-antibody system.
- To evaluate the impact of LET on signal detection and measurement parameters.
Main Methods:
- Labeling human serum albumin (HSA) with a luminescent ruthenium-ligand complex (D-455) as the donor.
- Labeling anti-HSA antibodies with a fluorescent squaraine-type cyanine dye (A-631) as the acceptor.
- Measuring changes in luminescence decay time and emission intensities upon antigen-antibody complex formation.
- Utilizing frequency-domain measurements in the low kilohertz range.
Main Results:
- Demonstrated successful energy transfer from the D-455 donor to the A-631 acceptor upon HSA/anti-HSA complex formation.
- Observed alterations in the luminescence decay time of D-455 and emission intensities of both dyes.
- The long decay time (around 500 ns) of the ruthenium donor enabled low kilohertz frequency-domain measurements.
- The system showed potential for gated measurements.
Conclusions:
- The novel immunosystem effectively employs luminescence energy transfer for antigen-antibody detection.
- The use of a long-decaying ruthenium donor and a high-quantum-yield cyanine acceptor offers advantages in signal processing and detection.
- This approach provides a sensitive and potentially faster method for analyzing antigen-antibody interactions compared to existing systems.
Abstract:
A novel immunosystem is described that exploits the effect of luminescence energy transfer from a luminescently labeled antigen to a fluorescent antibody. A luminescent ruthenium-ligand complex (D-455) with absorption/emission maxima at 456/639 nm, respectively, was employed as the donor label, and a squaraine-type cyanine label (636/655 nm), as the fluorescent acceptor label. Specifically, the system human serum albumin (HSA)/anti-HSA was studied. HSA was labeled with the donor dye D-455, and anti-HSA was labeled with the acceptor dye A-631. On formation of the antigen-antibody complex, energy transfer occurs. The radiationless energy transfer affects both the decay time of D-455 and the intensities of the emissions of both D-455 and A-631. The decay time of around 500 ns of D-455 allows frequency-domain measurements in the low kilohertz range and therefore can be based on the use of conventional optoelectronics. This also suggests gated measurements to be performed. The major difference from existing HSA immunosystems is the use of a slow decaying ruthenium-ligand complex as the donor and of a long-wave emitting cyanine acceptor dye having a high quantum yield and a decay kinetics that is governed by the rate of energy transfer from the slow decaying donor.
