Our research interest is using physical methods to answer fundamental biological questions at single molecule level, for example, what is the exact mechanism for a helicase to unwind duplex DNA; how polymerase works in the process of RNA transcription and DNA replication; how helicase and polymerase cooperate with each other during DNA metabolism. Currently, we are working on G-quadruplex DNA: How G-quadruplex folds and unfolds at single molecule level, the way G-quadruplex unfolds by various helicases, and the effects of G-quadruplex on the DNA, RNA polymerases. Basically, we use single fluorescence resonance energy transfer. Bulk assay including stopped-flow, fluorescence anisotropy and dynamic light scattering methods are also employed.