The addition of an appropriate mixture of ethanol, water and sodium perchlorate to crude extracts of some biological material results in the selective precipitation of nucleic acids. Detergent extracts of tissue-cultured plant cells treated with this reagent yielded as much as 95-100% of the nucleic acid while a similar percentage of the total protein remained in solution.
Sodium perchlorate (NaC104 * HzO) in high concentration will remove from solution the detergent sodium dodecyl sulfate and protein complexed with it (1). RNA and DNA remain behind in solution although the yield of the latter is much reduced if present as very large molecules.
This method was found to be effective in the preparation of plant viral RNAs and in most cases significant increases in yield and speed of preparation of infectious RNAs have been achieved (2).
It was noted that even if all protein was not removed with the salted out detergent, that which remained in solution was not precipitated on addition of 2 volumes of ethanol to the solution. This paper describes a reduction of the procedure to one step whereby the final desired concentrations of both perchlorate and ethanol are achieved simultaneously.
It was also the intention to eliminate the stage where detergent was removed from solution since this appeared to be the source of loss of some DNAs.
METHODS AND MATERIALS
Soybean cells (Glycine max L. Merr.) of a strain originating from the laboratory of Dr. Gamborg were grown in suspension culture in the medium of Miller (3). Erlenmeyer flasks of 300 ml and containing about 125 ml of culture were incubated at 28" with gyrorotary shaking of 120 strokes/min in the dark. Three cultures were labeled either with [methyl-3H] thymidine, approximately 0.1 &i/ml and 56 Cilmmol (A), or D-3 [ 14C]phenylalanine universally labeled, approximately 0.025 &i/ml and 477 mCi/mmol (B), or with both isotopic reagents (C). Radioactive 64