New Fluorophores Boost Precision smFRET

Scientists from St. Jude Children’s Research Hospital have developed a way to enhance the accuracy of single-molecule fluorescence resonance energy transfer (smFRET), a technique that measures nanoscale distances by analyzing the interactions between fluorophores. The key innovation lies in mitigating the detrimental effects of triplet dark states, which occur when excited electrons in fluorophores undergo a spin flip, rendering them non-fluorescent for extended periods.

Traditionally, smFRET measurements have been plagued by the accumulation of triplet dark states, leading to dimmed fluorescence signals and reduced spatiotemporal resolution. This limitation has hindered the technique's ability to capture the rapid conformational dynamics of biomolecules with high precision.

The team developed "self-healing" fluorophores that significantly reduce the lifetime of triplet dark states. By incorporating a triplet state quencher directly into the fluorophore structure, they have achieved up to a 1000-fold reduction in triplet state occupation.

"The enhanced brightness and photostability of self-healing fluorophores make it possible to improve the spatiotemporal resolution of smFRET imaging dramatically," said Avik Pati, co-author of the paper published in Nature Methods. "We can now robustly quantify nanometer-scale conformational dynamics within single biomolecules at sub-milliseconds and at physiological oxygen concentrations."

This advancement addresses a long-standing challenge in the field of fluorescence imaging, where triplet state accumulations have varied for different fluorophores and illumination intensities, leading to inconsistent experimental readouts and reduced data quality.

By employing self-healing fluorophores as both donors and acceptors in smFRET experiments, the researchers demonstrated improved data reliability and prevented loss in imaging quality even at high laser intensities. This breakthrough paves the way for more accurate distance measurements and a deeper understanding of biological processes at the molecular level.