Figure 1. Representative MALDI-TOF mass spectra of purified poliovirus Sabin reference strains and ClinPro Tools statistical analysis.
(a,b) Spectra of human poliovirus type 1, 2, 3 purified particles, shown in the m/z range of (a) 2 to 20 KDa (low molecular weight) and (b) 17 to 90 KDa (high molecular weight). Molecular weight values of poliovirus significant peaks are indicated on peak tops. (c,d) Analysis of discriminating peaks within the three poliovirus serotypes by using ClinPro Tools software (“Poliovirus type 1”, blue; “Poliovirus type 2”, red; “Poliovirus type 3”, green): “2D Peak distribution view” with the details at low (c) and high (d) molecular weight of the two best separating peaks; “PCA-3D dot plots window” of the spectra showing in 3 separate clusters the spectra of the 3 different poliovirus serotypes in the low (c) and high (d) molecular weight range; “Spectra view” in the low (c) and high (d) molecular weight range of the average spectra of the replicates of each poliovirus serotype. The red rectangles highlight the three discriminating peaks revealed in the mass range 2–20 KDa (7,522; 7,579; 7,635 m/z), and the four discriminating peaks in the mass range 17–90 KDa (30,197; 33,257; 33,554; 38,601 m/z). The blue rectangles are not discriminating peaks according to the applied Supervised Neural Network (SNN) statistical method.