FCS Analysis-We performed FCS analysis using an MF20 single-molecule fluorescence detection system (Olympus). This system is designed to analyze 384-well glass bottom plates (Olympus) using an onboard 543 nm He-Ne excitation laser. The laser was attenuated to 100 microwatts using density filters and was focused through a water-immersion objective lens at the center of each well, 100 m above the glass bottom (the confocal volume was ϳ1 fl). Fluorescence emitted from a sample was collected via the same objective lens and filtered through an HQ590/60 emission filter (Chroma Technology). The recorded signal intensity was analyzed using a one-component or two-component analytic model. The total sample volumes for FCS analysis were adjusted to 30 -50 l. During FCS analysis, the samples were sealed to prevent evaporation. The measurement time was 10 ϫ 15 s for each **data** point unless otherwise stated.