Curry and Hersh (1962) have reported that ribosomal protein may be isolated by treatment of a ribosome suspension with 2M-LiCl. We have applied this technique to rabbit reticulocyte ribosomes and found that it afford6 a method for the quantitative recovery of undegraded ribosomal RNA as well as the protein. The method can be extended in several ways and also permits a simplification of the standard method of isolation of s-RNA.

Experimental: Reticulocyte ribosomes were suspended in. 05M-KCl,. OClM-tris, pH 7.5,. OC15M-MgC12 (" TKM buffer") at a concentration of from 2-20 mg./ml. and an equal volume of 4M-LiCl added. The solution was kept at 4 0 C for 16 hours. It was found in agreement with Curry and Hersh (1962) that ribosomal protein was quantitatively solubilised (the contamination with RNA, estimated by the orcinol method, was less than 1.5%, the limit of the sensitivity of the assay). An investigation of reticulocyte ribosomal protein prepared in this manner will be reported (Mathias and Williamson, in preparation).