Femtosecond Lasers Open a New Window for Protein Imaging

Compact ultrafast fiber lasers enable two-photon excitation of tryptophan for label-free fluorescence lifetime imaging.

In the latest editorial in BioPhotonics, we explore the excitation of tryptophan, an important amino acid which serves as reporter of cellular and molecular health.

One existing method for detecting the fluorescence of tryptophan is fluorescence lifetime imaging microscopy (FLIM). However, detecting the fluorescence of tryptophan poses a challenge since the excitation, as well as emission, is buried deep in the UV, making standard microscopes ineffective. One possible solution is the use of femtosecond laser pulses in the 540- to 550-nm wavelength range which enable direct and efficient excitation of tryptophan, helping uncover vital structural details for the purposes of medical diagnostics.