DMS

DMS stands for dimethyl sulfate. Basically DMS is footprinting or fingerprinting if you like, of the RNA structure. It is a chemical check of which bases are paired as they should be and which are not. Rhiju describes it as doing following. DMS reacts only with unpaired A and C nucleotides. And as Brourd added it 1.5 - 3 days to complete.

Here is a<a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2701642/"> science paper</a>, the abstract do a good job of explaining what DMS is.