An oligomeric protein has a molecular weight of 357000. A 690 mg sample was treated with an excess of 1-fluoro-2,4-dinitrobenzene (Sanger\'s reagent) until the reaction was complete. Next the peptide bonds were hydrolyzed by heating with concentrated HCl. The product of the complete hydrolysis contained 1.3 mg of the compound shown below, and no other 2,4-dinitrophenyl derivatives of the ?-amino groups of other amino acids could be found. How may popypeptides are in this protein?