RNA and DNA don’t like to crystallize by themselves. They are more likely to crystallize when bound to some kind of nucleic acid binding protein like a polymerase, helicase, or something like that. A crystal would just have one or two chemical species in it. Just a protein, a protein-nucleic acid complex, or maybe you somehow manage to crystallize RNA or DNA.

crystallography requires milligrams of sample usually to find the conditions that work.

I am going with the same answer response of @Adron.

Good luck in your research @Dr.Ibrahim