Apparatus, methods and compositions for biotechnical separations

Abstract

RNA, preferably messenger RNA, is purified by use of selective precipitation, preferably by addition of compaction agents. Also included is a scalable method for the liquid-phase separation of DNA from RNA and RNA may also be recovered by fractional precipitation. Specific classes of compounds e.g. phase transfer catalysts (PTCs), most preferably selected polyamines of U.S. Pat. No. 6,617,108 polyamines which are quaternary compounds are unexpectedly potent in causing selective precipitation of DNA away from RNA, at low concentrations and in the presence of relatively elevated ionic strength selective removal of DNA can also remove both RNA and DNA, leaving behind a mixture which is advantageous for the further purification of, e.g., proteins. The invention include mini-preps, preferably of RNA or of plasmid and chromosomal DNA to obtain sequenceable and restriction digestible DNA in high yields in multiple simultaneous procedures and/or enhanced stripping of the compaction agent by a stripping method comprising high salt addition and pH shift, and combinations of these techniques. Isolation of RNA from bacterial lysates can employ selective precipitation by compaction agents.