Structure and properties of rat thymus deoxyribonucleoprotein. Solubility properties and effects of precipitation

Abstract

1. Deoxyribonucleoprotein was prepared from rat thymus and was studied chiefly by the method of electric birefringence. The birefringence depends on the electrical and optical properties of the molecules and on their volume; the decay time of birefringence (after the removal of the electric field) depends on molecular length. 2. A comparison was made of the properties of deoxyribonucleoprotein redissolved after precipitation in 0·15m-sodium chloride with those of the original material, the main object being to find if structural changes have occurred in the former. As a preliminary, the dependence of the solubility of the deoxyribonucleoprotein on the concentration of added salt was investigated, and the birefringence properties were also studied after the addition of sodium chloride at low concentrations, after the alteration of pH and after dialysis. 3. It was found that precipitation of deoxyribonucleoprotein occurs in two fractions, beginning at about 0·4mm-sodium chloride. The solubility is minimal at about 0·15m-sodium chloride. 4. The electric birefringence and decay time of the deoxyribonucleoprotein decrease with increasing concentration of added sodium chloride, and the birefringence also decreases after dialysis. Prolonged dialysis leads to precipitation. 5. The properties of deoxyribonucleoprotein redissolved after precipitation with 0·15m-sodium chloride differ considerably from those of the original deoxyribonucleoprotein. This is attributed to some type of disorganization process occurring during precipitation. It is concluded that the organization of the original structure is very specific.