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Flat-field fluorescence microscopy

Toward quantitative fluorescence imaging with homogeneous illumination (epi/HILO/TIRF)

Multifunctional fiber-based high-resolution imaging

Collaboration with Amezcua-Correa's lab in CREOL (coming soon).

Single-molecule pull-down assay on endogenous proteins

Traditional biochemical assays usually require large amount of samples. However, SiMPull enables to (i) directly count immunoprecipitated proteins from crude cell lysates with single-molecule sensitivity, and (ii) determine an stoichiometry of macromolecular complexes using photobleaching analysis. We are studying important biomarkers of neurodegenerative diseases using human brain samples from Parkinson's and Altzheimer's diseases patients.

Prior to CREOL

Fluorescence Nanoscopy   
[See also Nobel Prize in Chemistry 2014]

With a conventional objective lens and visible light, the maximum resolution of optical microscopy is fundamentally limited by diffraction, about 200 nm. Stimulated emission depletion (STED) microscopy is one of the most powerful approaches that overcome the diffraction barrier. In STED microscopy, an excitation beam is overlapped with a doughnut-shaped depletion beam where the STED light turns off fluorescence of molecules in the periphery region via stimulated emission depletion; as a result, it produces sub-diffraction sized focal spot. As the intensity of STED light increases, the effective spot size can shrink down below 10 nm. To overcome current fluorescence nanoscopy, we aim to develop 1) high-speed 3D nanoscope with low photo-damage, and 2) wide field-of view nanoscope with high throughput imaging for biomedical applications.

Fluorescent Probes

Nitrogen-vacancy (NV) center: NV center is a defect made of nitrogen and adjacent vacancy in diamond. It has several unique optical properties: 1) its ground state is triplet; 2) it neither shows photo-blinking nor photo-bleaching; 3) it is possible to readout spin state using fluorescence intensity. These advantages have allowed NV center to be used in quantum computation, nanoscale magnetometry and bioimaging.

Spinach RNA mimic of green fluorescent protein (GFP): RNA plays essential roles in biology; it transmits genetic information from DNA to proteins and also controls gene expression in various ways. Particularly, its location and copy number strongly affect the development of organisms. However, visualizing RNA in living cells has been challenging due to the lack of genetically modifiable fluorophores like GFP. We use RNA aptamer system (called Spinach) that can specifically bind to a small (non-fluorescent) molecule, eliciting bright fluorescence, in order to study gene expression of mRNA and non-coding RNA in bacteria and mammalian cells.

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