The preparation of animal nucleic acid

Abstract

The proposed method depends on the following properties of nucleic acid: (1) that it is separated from its protein combination by treatment with sodium hydroxide, (2) that it is soluble in dilute acetic acid and, (3) that it is precipitated by hydrochloric acid, or in the case of dilute solutions, by hydrochloric acid in the presence of magnesium sulphate.

Fresh, trimmed glandular tissue, finely hashed, is mixed well with twice its weight of tap water and 100 c.c. of 50 per cent. sodium hydroxide is then added for each kilogram of tissue. The material is then heated until all except the connective tissue is dissolved (40° C.-70° C.). Neutralize hot and at once with strong acetic acid; the reaction should finally be distinctly acid to litmus. Bring to a boil and filter hot on large folder filters.

When the filtrate has cooled an aliquot of 200 C.C. is taken and concentrated hydrochloric acid diluted with an equal volume of water is added from a burette until precipitation is complete, carefully avoiding an excess. If the nucleic acid does not flock out after the solution has been quiescent for several minutes, the same process should be repeated upon another aliquot after first adding 5 per cent. of magnesium sulphate (MgSO₄.7H₂O). Magnesium sulphate renders nucleic acid more insoluble. A proportionate quantity is then added to the bulk of the solution. The nucleic acid, which forms large flocks and slowly settles, is washed successively with 60, 80, and twice with 95 per cent. alcohol by decantation, filtered on hardened filter paper, washed again with 95 per cent. alcohol and finally with ether and then rapidly dried at about 70° C.

The yields from different glandular tissues vary from 0.8 per cent. to 1.5 per cent.