fig2

Figure 2. Volcano plots for filtering age-dependent features. Volcano plots illustrated the perturbed features between elders and youngers in (A) positive mode and (B) negative ion mode; In addition, the volcano plots show the comparison of OM and YM in (C) positive and (D) negative ion modes, and the comparison of OF and YF in (E) positive and (F) negative ion modes. The dark blue spot represents the features displayed with larger magnitude fold changes (x-axis, |log2(elder/younger)| ≥ 1.0) and statistical significance difference (y-axis, -log P-value ≥ 1.33). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.) OM: Old males; YM: young males; OF: old females; YF: young females.