Formaldehyde is able to form crosslinks between proteins and proteins, and proteins and nucleic acids (DNA and RNA). This makes it useful for things like capturing nucleic-acid binding proteins where they’re bound in order to figure out where they’re bound (methods such as CHIP-seq), stabilizing complexes for structural studies (e.g. cryo-EM, crystallography), or fixing tissues (freezing things in place so you can stain them and stuff). But how does formaldehyde actually do it? Like, what’s the mechanism? It doesn’t look like it should be able to do much of anything…