Fast Folding Dynamics of an Intermediate State in RNase H Measured by Single-Molecule FRET.

We have studied the folding kinetics of the core intermediate (I) state of RNase H by using a combination of single-molecule FRET (smFRET) and hidden Markov model analysis. To measure fast dynamics in thermal equilibrium as a function of the concentration of the denaturant GdmCl, a special FRET labeled variant, RNase H 60-113, which is sensitive to folding of the protein core, was immobilized on PEGylated surfaces. Conformational transitions between the unfolded (U) state and the I state could be described by a two-state model within our experimental time resolution, with millisecond mean residence times.

Intracellular thermometry by using fluorescent gold nanoclusters.

The "gold standard" for nanothermometry: The application of ultrasmall, near-IR-emitting fluorescent gold nanoclusters (AuNCs) for temperature sensing has been explored. AuNC-based fluorescent nanothermometry features excellent thermal sensitivity and simultaneous temperature sensing and imaging in HeLa cells.

Microwave-assisted rapid synthesis of luminescent gold nanoclusters for sensing Hg2+ in living cells using fluorescence imaging.

A microwave-assisted strategy for synthesizing dihydrolipoic acid (DHLA) capped fluorescent gold nanoclusters (AuNCs) has been developed. Irradiation with microwaves during synthesis enhanced the fluorescence quantum yield (QY) of AuNCs by about five-fold and shortened the reaction time from hours to several minutes. The as-synthesized DHLA-AuNCs possessed bright near-infrared fluorescence (QY: 2.

Effect of protein adsorption on the fluorescence of ultrasmall gold nanoclusters.

The interaction of proteins with ultrasmall gold nanoclusters (Au NCs) is investigated. Upon protein association, the fluorescence of Au NCs is significantly enhanced and, concomitantly, their luminescence lifetime is prolonged. The results stress the importance of investigating the behavior of fluorescent metal NCs in complex biological environment for advancing their bio-nanotechnology applications.

One-pot synthesis of near-infrared fluorescent gold clusters for cellular fluorescence lifetime imaging.

A facile strategy to synthesize water-soluble fluorescent gold nanoclusters (Au NCs) stabilized with the bidentate ligand dihydrolipoic acid (DHLA) is reported. The DHLA-capped Au NCs are characterized by UV-vis absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The Au NCs possess many attractive features including ultrasmall size, bright near-infrared luminescence, high colloidal stability, and good biocompatibility, making them promising imaging agents for biomedical and cellular imaging applications.