Nucleic Acids Res. 2015 Sep 3;43(15):7590-9. doi:10.1093/nar/gkv604

Harris CJ, Molnar A, Müller SY, Baulcombe DC

FDF-PAGE: a powerful technique revealing previously undetected small RNAs sequestered by complementary transcripts.

Denature with formaldehyde before loading or small RNA duplexes persist in Urea-PAGE.