You wish to purify mature eukaryotic mRNA molecules (but no other RNA molecules) from a cellular lysate that contains a mixture of every type of eukaryotic RNA molecule. You decide to "go fishing" (happy, ichthyologists?) for mRNA. Describe the molecular bait that you would use to "catch" mature mRNA molecules only. In other words, describe a molecule that that will bind well (interact strongly) with mature mRNA but no other RNA molecules.