To deconvolute more complex spectra, we initially applied a full spectral library containing all seven di-Ub isomers. The deconvolution results demonstrate the high specificity of the proposed multiple linear regression analysis. Even in the case of weakly resolved isomers, such as K6-and K11-, the deconvolution procedure successfully identifies the isomers present in the mixture on a qualitative level (Figure ). These results suggest that for multicomponent mixtures, deconvolution using an entire spectral library is possible; however, for the purposes of quantitation, using the full spectral library can be challenging due to the necessity of calibration curves. As shown in Figure , at least five points are necessary to generate a calibration curve, with two points corresponding to pure di-Ub isomers and three representing binary mixtures with different ratios of single components.