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Optical Imaging
Published in George C. Kagadis, Nancy L. Ford, Dimitrios N. Karnabatidis, George K. Loudos, Handbook of Small Animal Imaging, 2018
Unlike fluorophores, which have a peak emission, the emission spectrum for Cerenkov luminescence is proportional to 1/λ2 and is therefore heavily weighted in the ultraviolet and blue, where the mean free path for photons is short. In order to modulate Cerenkov luminescence to more penetrating longer wavelengths, several groups have investigated the interaction of Cerenkov radioisotopes with quantum dots (Dothager et al. 2010; Liu et al. 2010b; Boschi and Spinelli 2012; Carpenter et al. 2012), fluorophores (Lewis et al. 2010; Axelsson et al. 2011), and photoactivatable probes for imaging and therapy (Ran et al. 2011; Kotagiri et al. 2013). While some investigators have reported noise in the CCD sensor due to direct hits by 511 keV γ-rays, the Spinelli group demonstrated little or no signal from a mouse covered with black paper (Boschi et al. 2011). Although Cerenkov luminescence endoscopy (CLE) is more invasive than CLI and CLT, a custom-made fiber-bundle-based endoscope has been described for use in rodents (Carpenter et al. 2014) with the advantage of increased sensitivity.
Bridging the gap: Super-resolution microscopy of epithelial cell junctions
Published in Tissue Barriers, 2018
Emily I. Bartle, Tejeshwar C. Rao, Tara M. Urner, Alexa L. Mattheyses
SMLM depends on the photophysical properties of the fluorescent label. STORM and direct STORM (dSTORM) utilize photoswitchable probes typically consisting of chemical dyes conjugated to antibodies in special imaging buffer, which provide multiple localizations per fluorophore. For example, Alexa 647 has optimal photophysical properties including a high photon yield and low duty cycle.43 Alternatively, irreversibly activatable fluorophores provide a single off-on cycle. The typical photoactivatable probes used in PALM are genetically encoded, offer a 1:1 labeling stoichiometry, and can provide density information with each localization representing a single protein.44 SMLM can accommodate multiplexed imaging with multiple probes, live cell imaging,45-48 and 3D imaging with ∼50 nm axial resolution.49 SMLM has proven to be a powerful tool in studying nanoscale structures and organization in cells and tissues, and its capabilities continue to evolve.