Thesis Highlights - Chi-cheng Fu
1) Bio-applications of Single Fluorescent Nanodiamonds (FNDs). This novel material can generate more stable (without blinking and photobleaching) and brighter fluorescence than other traditional dyes. Our group firstly demonstrated single FNDs are excellent cellular biomarkers and can be tracked in a living cell with high temporal and special resolution for over a course of 20 min. This setup showed enormous potential applications to reveal underlying mechanisms hidden behind heterogeneous biological phenomena (work published in PNAS, 2007, 104, 727, first author, cited over 70 times and Nat. Nanotech. 2008, 3, 284). To widen biological applications, further enhancement of its fluorescence intensity was achieved by depositing them on nanocrystalline Ag films which can also be modulated by the binding of biomolecules as a potential bio-sensor with single-particle sensitivity (work published in Phys. Chem. Chem. Phys, 2009, 11, 1058).
2) Nano- wrinkles and petals enhanced fluorescence. A simple two-step (metal deposition and subsequent heating) approach to fabricate controllable biaxial and uniaxial nanowrinkles and nanopetals based on shape memory polymer (pre-stressed polystyrene) sheets is presented. Wavelengths of wrinkles can be tuned from 300nm to 800nm by controlling the thickness of deposited metal. We demonstrate utility of these nano structures with ready integration into microchannels and effectiveness in surface enhanced sensing. (work published in Adv. Mater. 2009, 21, 1, first author and pre-submit to Nat. Method ).
3) Characterization of Single DNA Molecules Confined in Nanoslits. We characterized the basic polymer physics of single DNA molecules confined in nanoslits with height of 20 nm to 110 nm, close to persistence length of polymers. The highly anisotropic shapes with length independent mean asphericity led to the finding that the conformation and chain relaxation of confined DNA molecules exhibit quasi-two-dimensional behavior. The preferred one-dimensional behaviors of DNA molecules close to sidewalls or cylindrical posts were also characterized (work published in Phys. Rev. E, 2007, 76, 011806, second author and Macromolecules 2009, 42, 1770).
4) Fis-Protein Induces Rod-Like DNA Bending. Fis protein can bend DNA chain with length much shorter than its persistence length. We applied single-molecule fluorescence resonance energy transfer method to probe these conformational changes. A broad distribution of bending angles correlates well with the molecular dynamics simulation. The flexibility of DNA upon Fis binding is attributed to the breakages of hydrogen bonds between base pairs. DNA kinks at specific sites, instead of continuous bending. The loosening of DNA structures might have biological implications for the functions of Fis-proteins as transcription cofactors (submit to J. Phys. Chem. B, first author).
