Improved Method for Simultaneous Isolation of Proteins and Nucleic Acids

Guanidinium thiocyanate-phenol-chloroform extraction (GTPC extraction) is widely used in molecular biology for isolating DNA, RNA, and proteins. Protein isolation by commercially available GTPC solutions is time consuming and the resulting pellets are only incompletely soluble. In this study ethanol-bromochloropropane-water was used for precipitation of proteins from the phenol-ethanol phase after GTPC extraction of RNA and DNA. The precipitated proteins can be readily dissolved in 4% SDS for subsequent analysis. This technique allows a fast (30min) and efficient (with a protein recovery of up to 95%) extraction of proteins for the study of transcriptional and posttranscriptional events from the same sample.