title: Label-free detection of single protein molecules using deep UV fluorescence lifetime microscopy.
abstract: We present the detection of single beta-galactosidase molecules from Escherichia coli (Ecbeta Gal) using deep UV laser-based fluorescence lifetime microscopy. The native fluorescence from intrinsic tryptophan emission has been observed after one-photon excitation at 266 nm. Applying the time-resolved single-photon counting method, we investigated the fluorescence lifetime distribution and the bursts of autofluorescence photons from tryptophan residues in Ecbeta Gal protein as well as fluorescence correlation spectroscopy of Ecbeta Gal. The results demonstrate that deep UV laser-based fluorescence lifetime microscopy is useful for identification of biological macromolecules at the single-molecule level using intrinsic fluorescence.
authors.affiliation: Physikalisch-Chemisches Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
authors.forename: Stefan
authors.initials: S
authors.lastname: Seeger
mesh_terms: D004926:Escherichia coli / Q000201:enzymology; D005453:Fluorescence; D007834:Lasers; D008856:Microscopy, Fluorescence / Q000295:instrumentation / Q000379:methods*; D017785:Photons; D011506:Proteins / Q000032:analysis* / Q000737:chemistry; D013997:Time Factors; D014364:Tryptophan / Q000737:chemistry*; D014466:Ultraviolet Rays; D001616:beta-Galactosidase / Q000032:analysis* / Q000737:chemistry
chemical_list: D011506:Proteins; D014364:Tryptophan; D001616:beta-Galactosidase