Native purification, RNAs

Two other powerful methods for native RNA purification, one based on size-exclusion chromatography and the other using affinity purification, have been published in the past. The former employs separation of the different species in a transcription reaction (NTPs, small abortive transcripts, the transcribed RNA, and the plasmid DNA) based on size rather than charge (Kim et al., 2007 Lukavsky and Puglisi, 2004 McKenna et al., 2007). 

A direct method for testing RNA-protein interaction in vitro is by affinity-precipitation or -chromatography. Two molecules interact if specific purification of one of them leads to co-purification of the other molecule. This approach is often referred to as the pulldown method . Different experimental designs can be used One possibility is to let the RNA-protein complex form in solution under native conditions, and then purify the complex by binding a high affinity tag, present in either the RNA or the protein to beads. The physical separation may be accomplished by low speed centrifugation (batch approach) or by column chromatography (column... 

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