A ‘dark’ fluorescent protein could aid FRET experiments
Lynn M. Savage
Microscopy using Förster
resonance energy transfer is a potent method for imaging protein conformations and
interactions. However, the technique has two conflicting requirements: the necessary
spectral overlap between the donor molecule’s emission and the acceptor’s
absorption ranges and the need for an appropriate amount of separation between the
donor’s and acceptor’s emission wavelengths.
Researchers from European Neuroscience Institute
in Göttingen, Germany, from King’s College London and from Mount Vernon
Hospital in Northwood, UK, have devised a variant of yellow fluorescent protein
(YFP) that addresses this quandary by not fluorescing at all, yet proficiently working
as an acceptor when paired with GFP. They modified the amino acid residues that
normally stabilize the excited state of enhanced YFP, creating a “dark”
chromoprotein that retains its absorption properties and that acts as a quencher
for donor fluorescence. The group dubbed the protein REACh, for “resonance
energy-accepting chromoprotein.”
In the March 14 issue of
PNAS,
they report that the variant has an excitation maximum at 510 nm and a relative
fluorescence of 0.03 at 538 nm. Using a Ti:sapphire laser from Coherent Inc. of
Santa Clara, Calif., a confocal microscope made by Leica and a multichannel plate
photomultiplier from Hamamatsu Photonics KK in Hamamatsu City, Japan, they found
that the protein’s emission lifetime is ~320 ps, compared with 2.9 ns
for enhanced YFP, and that its Förster distance (when paired with GFP) is 5.9
nm, compared with 5.6 nm.
The lack of emission from the variant
means that spectral overlap can be optimized through the choice of donor, improving
FRET detection because more photons can be collected with less of the background
noise that is typically generated by acceptor emission. It also means that there
is a wider spectral band for additional fluorescing components, which should help
facilitate multiplexed imaging of protein interactions within cells.
The researchers acknowledge that the
small amount of residual fluorescence of their creation may not be negligible
for some applications. However, they foresee using the mutant YFP for fluorescence
lifetime measurement and for laser-scanning microscopy.
LATEST NEWS
- CLEO Heads to the East Coast
Apr 29, 2024
- Laser-Based Gas Analyzer Developed to Detect Air Pollution
Apr 29, 2024
- Qubits Could be Stored in Flash-Like Memory
Apr 29, 2024
- Exail Signs LLNL Contract, Partners with Eelume
Apr 26, 2024
- Menlo Moves U.S. HQ: Week in Brief: 4/26/2024
Apr 26, 2024
- Optofluidics Platform Keys Label-, Amplification-Free Rapid Diagnostic Tool
Apr 25, 2024
- DUV Lasers Made with Nonlinear Crystals Enhance Lithography Performance
Apr 25, 2024
- Teledyne e2v, Airy3D Collaborate on 3D Vision Solutions
Apr 24, 2024