Southern and Northern blot fixing by microwave oven

Abstract

Southern and Northern blot techniques are powerful procedures\nfor studying gene structure and function. These methods involve\nthe separation of nucleic acids according to size on an agarose or\npolyacrylamide gel and subsequent transfer of the nucleic acid to\nsuitable nitrocellulose or nylon-based membranes. DNA or RNA\nmolecules bound to the membrane are then fixed and hybridized\nwith a radioactive probe, specific for the gene under study. The\nfixing step is particularly important for quantitatively reproducible\nresults, especially if membranes are to be rehybridized\nseveral times. The traditional fixing procedure involved baking\nthe membrane for 2 h at 80°C (1). More recently, it has been\nshown that efficient cross-linking of nucleic acids to the\nmembrane could be obtained by 30 s to 3 min exposure of UV\nirradiation (2). Earlier studies described the use of a microwave\noven to fix bacterial colonies to nylon membranes (3) or to fix\nDNA within paraffin tissue blocks (4). We demonstrate here that\na 2 min treatment of Southern or Northern blots in a microwave\noven efficiently fixes nucleic acids to nylon membranes which\ncan withstand repeated reuse in hybridization reactions.