Figure 4 | Scientific Reports

Figure 4

From: Systematic Evaluation of Non-Uniform Sampling Parameters in the Targeted Analysis of Urine Metabolites by 1H,1H 2D NMR Spectroscopy

Figure 4

Influence of the spectral type on the recovery of the relative intensity of a selected cross signal in each spike-in sample and the blank employing urine I, exemplarily shown for tyrosine (a), glutamine (b), and lactic acid (c). US 1H,1H-COSY45 spectrum (n = 1) indicated by blue bars. NUS 1H,1H-COSY45 spectra simulated from the US spectrum displayed with 75%, 50%, and 25% of the US data points depicted by green, orange, and grey bars, respectively. Each NUS spectrum was constructed with a sinusoidal Poisson-gap sampling scheme taking six seed values per NUS level and reconstructed with the compressed sensing approach employing the iterative re-weighted least squares method. On the x-axis, the spike-in concentration given in micromolar is shown. The intensity ratio of the total cross peak integral scaled to the internal standard TSP of the metabolite signal (mean +SD) obtained with US or NUS relative to US is plotted on the y-axis.

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