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dc.contributor.authorMin, Wei
dc.contributor.authorLu, Sijia
dc.contributor.authorChong, Shasha
dc.contributor.authorRoy, Rahul
dc.contributor.authorHoltom, Gary
dc.contributor.authorXie, Xiaoliang Sunney
dc.date.accessioned2010-02-23T18:40:56Z
dash.embargo.terms2010-04-23
dc.date.issued2009
dc.identifier.citationMin, Wei, Sijia Lu, Shasha Chong, Rahul Roy, Gary R. Holtom, and Xiaoliang Sunney Xie. 2009. Imaging chromophores with undetectable fluorescence by stimulated emission microscopy. Nature: 461(7267): 1105-1109.en_US
dc.identifier.issn0028-0836en_US
dc.identifier.urihttp://nrs.harvard.edu/urn-3:HUL.InstRepos:3693471
dc.description.abstractFluorescence, that is, spontaneous emission, is generally more sensitive than absorption measurement, and is widely used in optical imaging. However, many chromophores, such as haemoglobin and cytochromes, absorb but have undetectable fluorescence because the spontaneous emission is dominated by their fast non-radiative decay. Yet the detection of their absorption is difficult under a microscope. Here we use stimulated emission, which competes effectively with the nonradiative decay, to make the chromophores detectable, and report a new contrast mechanism for optical microscopy. In a pump-probe experiment, on photoexcitation by a pump pulse, the sample is stimulated down to the ground state by a time-delayed probe pulse, the intensity of which is concurrently increased. We extract the miniscule intensity increase with shot-noise-limited sensitivity by using a lock-in amplifier and intensity modulation of the pump beam at a high megahertz frequency. The signal is generated only at the laser foci owing to the nonlinear dependence on the input intensities, providing intrinsic three-dimensional optical sectioning capability. In contrast, conventional one-beam absorption measurement exhibits low sensitivity, lack of three-dimensional sectioning capability, and complication by linear scattering of heterogeneous samples. We demonstrate a variety of applications of stimulated emission microscopy, such as visualizing chromoproteins, non-fluorescent variants of the green fluorescent protein, monitoring lacZ gene expression with a chromogenic reporter, mapping transdermal drug distributions without histological sectioning, and label-free microvascular imaging based on endogenous contrast of haemoglobin. For all these applications, sensitivity is orders of magnitude higher than for spontaneous emission or absorption contrast, permitting nonfluorescent reporters for molecular imaging.en_US
dc.description.sponsorshipChemistry and Chemical Biologyen_US
dc.language.isoen_USen_US
dc.publisherNature Publishing Groupen_US
dc.relation.isversionofdoi:10.1038/nature08438en_US
dc.relation.hasversionhttp://bernstein.harvard.edu/papers/Nature%2010.22.09.pdfen_US
dash.licenseLAA
dc.titleImaging Chromophores With Undetectable Fluorescence by Stimulated Emission Microscopyen_US
dc.typeJournal Articleen_US
dc.description.versionAccepted Manuscripten_US
dc.relation.journalNatureen_US
dash.depositing.authorXie, Xiaoliang Sunney
dc.date.available2010-04-23T07:31:11Z
dc.identifier.doi10.1038/nature08438*
dash.contributor.affiliatedHoltom, Gary
dash.contributor.affiliatedMin, Wei
dash.contributor.affiliatedLu, Sijia
dash.contributor.affiliatedRoy, Rahul
dash.contributor.affiliatedChong, Shasha
dash.contributor.affiliatedXie, Xiaoliang


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