Quantitative analysis of diffusion to capture in WGA-treated cells. (A) Line traces are plotted for γ-tubulin signal, Sstr3-GFP signal, and GBP signal along the length of cilia after an 8-min incubation with 55 nM GBP. Traces for individual cilia are plotted as thin dotted lines. Averaged traces are shown as solid lines (n ≥ 20). (B) Line traces are plotted as in A for incubations with 55 nM GBP for the indicated times. Sstr3-GFP and γ-tubulin plots correspond to the 8-min time point (n = 10–38). (C) Relationship between the square of the GBP-stained distance and time for GBP added at the indicated concentrations. Error bars indicate standard deviations (n = 10–38). The linear slope ± SEM (in micrometers squared/minute) was determined for each concentration by weighted least-squares fitting. (D) Overview of mathematical model for GBP entry into cilia and capture by Sstr3-GFP in the absence (left) and presence (right) of WGA. GBP added at concentration B₀ enters cilia with rate constant k and is captured by Sstr3-GFP present at concentration S₀. The position of the distal boundary of the GBP-stained segment is expressed as L(t) (with WGA) or $L∼(t)$ (no WGA), and the position- and time-dependent concentration of free GBP within cilia is expressed as B(x,t). (E) Comparison of observed GBP staining results with fitted curves derived from mathematical model using D_GBP = 7.3 µm²/s. (F) Relationship between time and (GBP distance stained)²/[GBP] (in micrometers squared/micromolar GBP) for GBP alone, Trx-GBP, and MBP-GBP. Data point symbols indicate the GBP concentration added. Error bars indicate standard deviations (n = 10–38). Lines show linear fits to measured data, with slopes indicated in micrometers squared/micromolar/minute.