KD and kON as a function of (A) polymer backbone length (DP) displayed in red and (B) ethylene oxide (EO) side chain length displayed in blue. KD values were determined with a constant [FAP] typically between 1-10 nM in PBS+ using a λex = 636 nm and λem = 664 nm. For each kon [MG-PEO] = 4, 2, and 1 uM and [dL5**] = 50 nM in PBS+ with λex = 636/20 nm and λem = 700/20 nm. Brightness (solid circle) and diffusion time (hollow circle) from FCS as a function of (C) polymer backbone DP and (D) EO side chain length. For Figures 3A and 3C, all polymers had EO side chain lengths of ∼8.5 (Table 1, Entries 1-4), whereas polymers in Figures 3B and 3D had similar backbone DPs ≈ 150-170 (Table 1, Entries 2, 5-6).