Extended Data Figure 4. Localization of Brd4 clusters in reconstructed 3D-iLLS images.

a-d, Axial profiles of individual Brd4 clusters. Thick lines show non-linear least-squares fits to equations of the form $B+\frac{A}{2}(1\pm \cos (k(z-z_0)+\theta ))e^{-\frac{(z-z_0{)}^2}{2{{\sigma }_z}^2}}$ for Cam0 and Cam1, respectively. Global fitting is performed, with shared k,θ and σ_z parameters. We obtain two separate localization measurements of the parameter z₀ that indicates the center position of the cluster, estimated independently from Cam0 and Cam1. e, Oscillation wave-vector k is 0.02375±0.00059 nm⁻¹ (mean±SD), indicating a relative error σ_k/k of ≈2.5%. f, The center position z₀ shows a systematic offset between the two cameras of dz₀=25nm and an r.m.s localization error σ_dz0=10 nm. These systematic and random errors relative to the oscillation period (2π/k=265nm) are ≈9% and ≈4% respectively.