This is the 2D companion to the 3D chromatin-fiber render: the same coarse-grained nucleosome-sliding model, but visualised as a kymograph — a position-vs-time raster, the standard tool real single-molecule chromatin studies use to read sliding dynamics off a microscope movie. The instantaneous track at the top shows the fiber right now; the scrolling map below plots that same 1D position axis against time flowing downward, so every nucleosome traces a streak instead of a moving dot — a genuinely 2D field (position × time), not a flattened side view of a 3D scene.
Footprint: F = 147 bp (fixed octamer contact)
Linker(i): D_i = x_(i+1) − x_i − F (free bp between neighbors)
Motor step: Δx = ± s per accepted ATP cycle, s = 7 bp (coarse-grained)
Spacing mode mimics ISWI/CHD1: each remodeler measures the linker DNA on both sides of a nucleosome and steps it toward the longer side, Δ = −sign(D_left − D_right)·s, converging the array to evenly spaced nucleosomes. In the kymograph this shows up as streaks that bend until they become parallel, evenly-spaced diagonal (then vertical) lines.
Clear promoter mode mimics SWI/SNF/RSC at active promoters: the remodeler nearest the marked transcription-start-site window is stepped away from it every ATP cycle, opening a nucleosome-depleted region (NDR). In the kymograph the promoter band (shaded) empties out as the nearest streaks visibly bend away from it. Accessibility A = 1 − (bp of the promoter window covered by a footprint) / (window width).
A step is only accepted if it does not push a histone core into a neighboring nucleosome's footprint — remodelers cannot pass through each other, so repositioning propagates one collision at a time, visible in the kymograph as streaks that stall until the neighbor ahead of them has already moved.