N Linear regression. Even if linear regression is a simplistic model due to its strong assumptions, it gives the possibility to evaluate the contribution of each single variable to classification. The outcome variable we considered is the reactivity value, which ranges from 1 to 65536. The distribution of these values shows that the outcome can be easily binarized: in fact, as previously mentioned, the reactivity of the positive peptides ranges between 10000 and 65536, while this value ranges from 1 to 1000 in the negative peptide case. For this reason, we also tested this classifier by considering the binary classes 0-negative and 1-positive as continuous values.