Fig. 4: Raman spectroscopic analysis of sex-specific differences in urine pools.

Median resonance Raman spectra of female (orange, 1), male (blue, 2), and mixed (purple, 3) pools with the weighting vectors for LD1 (a) and LD2 (b) depicted as vertical lines, showing the extrema of the discriminant coefficient scaled PCA loadings. Specifically, the lines at approximately 850, 1050, and 1525 cm⁻¹ can be assigned to creatinine, while the lines at 1015, 1265, and 1611 cm⁻¹ and at 1355, 1435, and 1660 cm⁻¹ originate from urea and uric acid, respectively. With this linear classifier, the data can be perfectly discriminated (c). The test and training scores of LD1 and LD2 are depicted as small and large transparent dots, respectively.