Figure 3

PCA results of six samples. Positive ion mode: (a) PC1 (69%) loadings of amino acid fragments (red) and water clusters (green) labelled in Fig. 2, (b) PC1 (69%) scores of six samples. Negative ion mode: (c) PC1 (76%) loadings of water clusters (blue) labelled in Fig. S1, (d) PC1 (76%) scores of six samples.