(a) PC2 vs. PC5 score plot. (b) PC2 vs. PC5 original loading plots labeled in terms of m/z ratio. PCA of positive ion mode mass spectra: (c) PC2 vs. PC3 score plot. (d) PC2 vs. PC3 original loading plots labeled in terms of m/z ratio. Immature oocytes (green circles, n = 31), 24-hour in vitro matured oocytes (red diamonds, n = 25), 44-hour in vitro matured oocytes (blue triangles, n = 40).