Peak Tracking

Peak tracking analyses track how peak positions (and linewidths) change from plane to plane. It is the common core for measurements where peaks move: fit a titration binding isotherm, or measure a coupling/RDC (see Couplings and RDCs). Use peaktrack2d directly when you just want the per-plane positions and linewidths without a physical model.

using NMRAnalysis

# A series of 2D spectra in which peaks move
peaktrack2d(["11", "12", "13"])

• inputfilenames: a single pseudo-3D dataset, or a vector of 2D spectra (one per plane). Bruker experiment numbers work too, individually or as a list/range (e.g. peaktrack2d(1:3)), resolved relative to the working directory.

Each peak holds an independent position, linewidth and amplitude in every plane, and each plane is fitted separately. This keeps the fit well-conditioned and decoupled: adjusting one plane does not disturb the others.

Adding and positioning peaks

• (A) — add a peak. Adding walks through the planes so you mark the peak in each one: press A with the cursor on the peak in the current plane, then for each subsequent plane (stepping forwards and wrapping back to the start) press:

  • a to mark the peak's position in that plane and advance,
  • space to copy the current position into all remaining planes and finish,
  • esc to cancel.

  When at least one peak has already been fitted, new peaks are pre-seeded with the average displacement pattern of the fitted peaks, so they inherit the common motion.

• (T) — add and track. Drops a peak and follows the intensity maximum across the planes automatically (anchored at the current plane, propagated outwards). Best for well-resolved peaks; not available for RDC experiments.

• (L) — add along a line. Press l with the cursor at one end of the path a peak follows across the planes. The line then follows the cursor: either keep l held, drag to the other end and release, or release it straight away, move to the other end, and click or press l again. The status line says which you are doing. The peak is placed in each plane at the most intense point along that line, and the fit then refines it within the radius. esc cancels the line. Suited to fast-exchange titrations; not available for RDC experiments.

• Drag a peak's handle to correct its position in the current plane. The handle enlarges when hovered. Dragging re-estimates that plane's amplitude.

• (D) deletes and (R) renames the selected peak, as elsewhere.

Visualisation

• Each peak's trajectory across the planes is drawn as a coloured polyline (red = needs fitting, blue = fitted, orange = fit unfinished, green = selected).
• The (S)how all toggle (also bound to s) overlays every plane's contours faintly, for context when a peak moves a long way.

Output

Save to folder writes results.csv with each peak's per-plane positions (x[1], x[2], …), linewidths and amplitudes, and any model-derived parameters. Load peak list... restores them, including the fitting radii. The default summary plot shows the combined chemical-shift perturbation Δδ against residue number, one series per plane.