Label-free detection of protein interactions using deep UV fluorescence lifetime microscopy

We present a label-free detection of protein interaction between β-galactosidase from Escherichia coli (Ecβ-Gal) and monoclonal anti-Ecβ-Gal using deep UV laser-based fluorescence lifetime microscopy. The native fluorescence from intrinsic tryptophan emission was observed after one-photon excitation at 266 nm. Applying the time-correlated single-photon counting (TCSPC) method, we investigated the mean fluorescence lifetime and lifetime distributions from tryptophan residues in Ecβ-Gal protein, monoclonal anti-Ecβ-Gal, and corresponding complex. The results demonstrate that deep UV laser-based fluorescence lifetime microscopy is useful for sensitive identification of biological macromolecules interaction using intrinsic fluorescence.