The present work considers the methods for prediction of the electrostatic term of free energy of denaturation and emphasizes the calculation of electrostatic interactions in denatured state. Very often electrostatic interactions in denatured state are neglected (the null approximation, NA) or modeled on the basis of only one possible spatial distribution of protein charges, which makes these models applicable to a limited number of cases. Here we present a more general framework for the modeling of the denatured state. It is based on the assumption that the titratable groups of an unfolded protein can adopt a quasi-random distribution, restricted by the protein sequence. In order to build an adequate model for calculation of electrostatic interactions in denatured state properties of unfolded polypeptide chains of different sizes, with variety of side chains, and with various charge compositions were analyzed by statistical methods. The calculated free energy of denaturation as a function of pH reproduces the experimental data better than the other models, including the commonly used NA. It is demonstrated that the seemingly good agreement with experimental data obtained in some cases by NA originates from the compensatory effect between the pair-wise electrostatic interactions and the desolvation energy of the individual sites. It is also worth noting that the ionization properties of denatured proteins are influenced by the protein sequence.