Direct in-gel hybridization of DNA with digoxigenin-labeled probes

In-gel hybridization with digoxigenin (DIG)-labeled probes has been shown to detect complementary DNA sequences in dried agarose gels. Gels dried at room temperature or at 55 degrees C in an oven do not show detectable changes in the sensitivity of detection. However, gels dried under vacuum seem to lose the sensitivity by approx 8- to 10-fold. In-gel hybridization after blotting high molecular weight T7 DNA (40 kbp) onto nylon membranes has been demonstrated to transfer the DNA to the membrane inefficiently. In-gel hybridization of DIG-labeled probes with the complementary DNA sequences has been determined to detect as little as 0.05 ng of 40-kbp T7 DNA and single copies of the erythromycin resistance marker gene ermA. Nonradioactive in-gel hybridization provides better quantitation of nucleic acids than filter hybridization in Southern and Northern blot analysis.