*4.5. Charge State and Kappa Value Calculation of Linkers*

The charge state of linkers was characterized by three parameters [47,48]. The net charge per residue value (NCPR) is defined as |f+ − f−|, where f+ and f− are the fractions of positively- and negatively-charged residues within the linker region, respectively. The total fraction of charged residues (FCR) is defined as (f+) + (f−). The linear distribution of opposite charges is described by the kappa (κ) parameter [48], which is the mean-square deviation of local charge asymmetry from the overall sequence charge asymmetry weighted on the maximal asymmetry allowed for a given amino-acid composition. Kappa can range from 0 (when opposite charges are evenly distributed) to 1 (when opposite charges are segregated into two clusters). Kappa has a basic influence on IDP/IDR conformation, as there appears to be an inverse correlation between the kappa value and the radius of gyration of the polypeptide chain.
