Extraction methods often are chosen to maximize the data that may be obtained such as the simultaneous isolation of messenger RNA (mRNA)1 and proteins from a limited amount of tissue. Such methods reduce time, costs, and sampling error. More critically, they facilitate more meaningful interpretation and correlation of data. Although several methods for simultaneous RNA–protein extraction are used ,  and , it remains difficult to establish whether divergent results are due to sample preparation and handling or underlying biology. We compared two such established methods routinely used interchangeably for simultaneous extraction of RNA and proteins, Trizol LS reagent (Invitrogen Life Technologies, Carlsbad, CA, USA) and guanidinium isothiocyanate (GITC) media , ,  P. Chomczynski and N. Sacchi, Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction, Anal. Biochem. 162 (1987), pp. 156–159. Abstract | View Record in Scopus | Cited By in Scopus (40696) and , against a third “protein-only” method using two-dimensional (2D) electrophoresis buffer to determine whether similar protein profiles are obtained. Comparisons between Trizol LS and GITC-based RNA extractions have been reported previously ; however, a complete lack of information exists regarding the proteins extracted simultaneously using these methods. Both the Trizol LS and GITC methods are modified versions of the procedure first described by Chomczynski and Sacchi in 1987 , and although they use very similar organic solvents and salts, intriguingly different profiles of proteins with very different ranges of molecular sizes are obtained (Fig. 1). Trizol LS preferentially extracts low-molecular weight species, whereas GITC extracts high-molecular weight proteins. These results highlight the importance of using the same analysis protocol for valid comparison and interpretation of results from a sample population. Importantly, the protocols are useful for preferential extraction of low- and high-molecular size proteins, respectively.
Analytical Biochemistry Vol. 359, Issue 2, p. 274-276