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.

Screenshot of peak fitting

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.
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, green = selected).
The Show all toggle 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.