1. A method of producing a protein that contains erythropoietin and one polyethylene glycol residue, comprising the following steps: a) applying a solution containing a mixture of free erythropoietin and erythropoietin and polyethylene glycol conjugates containing one or more polyethylene glycol residues per erythropoietin molecule onto a column containing SP chromatographic material Sephacryl S 500 HR balanced by a solution with an electrical conductivity of about 21 mS / cm, b) flushing the column with a solution with an electrical conductivity of about 21 mS / cm and thus removing freedoms polyethylene glycol and proteins containing two or more polyethylene glycol residues, c) washing the column with a solution with linearly increasing electrical conductivity to a final value of about 62.5 mS / cm and, thus, separate release from the column of a protein containing erythropoietin and one polyethylene glycol residue, and erythropoietin, with a protein containing erythropoietin and one polyethylene glycol residue being released first. The method according to claim 1, characterized in that the solution with an electrical conductivity of about 21 mS / cm is a solution with a pH value of 2.5-3.5.3. The method according to claim 1, characterized in that the solution with an electrical conductivity of about 21 mS / cm is a phosphate buffer solution with a pH value of 2.5-3.5.4. The method according to claim 1, characterized in that the electrical conductivity of the solution containing a mixture of erythropoietin and conjugates of erythropoietin and polyethylene glycol containing one or more residues of polyethylene glycol per erythropoietin molecule is not adjusted to a value of about 21 mS / cm. The method according to claim 1, characterized in that the solution with a linearly increasing electric1. Способ получения белка, который содержит эритропоэтин и один остаток полиэтиленгликоля, включающий следующие стадии:a) нанесение раствора, содержащего смесь свободного эрит
