Factors limiting single-peak quantitative NMR precision

Identify the factors that limit the precision of single-peak 2D Q-BEST NMR measurements to approximately 15–20%.

Background

The paper introduces 2D Q-BEST NMR for quantifying protein concentrations and conformational-state populations from three 1H–15N correlation spectra. In validation experiments with ubiquitin, corrected peak intensities achieved a precision of approximately 15–20% for individual cross-peaks. Although averaging across well-resolved resonances can improve practical precision, the authors note that the sources of the remaining limitation in single-peak measurements have not yet been fully determined. Resolving these factors could guide improvements in pulse-sequence design, signal processing, and peak-volume measurement.