The effect of altering time domains and window functions in two-dimensional proton COSY spectra of biological specimens

Abstract

The time constraints imposed by the limited viability of biopsy and cell samples require careful selection of both acquisition and processing parameters for two-dimensional NMR spectroscopy. The consequences of truncating 2D NMR data sets in the t 1 dimension are discussed in terms of the inherent loss of resolution versus the time constraints imposed by the degrading sample. The choice of window functions during processing is shown to have dramatic effects on the resolution, sensitivity, and appearance of 2D spectra of biological specimens containing lipid. For magnitude-mode COSY spectra, sine-bell window functions in both domains generally give the best combination of resolution, lineshape, and signal-to-noise. However, components with short spin-spin relaxation values (including lipid and oligopeptides) are better visualized by applying Lorentz-Gauss window functions or by shortening the time domain. This is demonstrated with an example of a 2D data set of cultured malignant melanoma cells processed under various conditions. Each cell line and tissue type (and the molecules of interest) must be considered independently when acquiring, analyzing, and presenting 2D NMR spectra.