An article was recently published that might help you with your RNA crystallization----"Crystallization of ribozymes & small RNA motifs by a sparse matrix approach" by Jennifer A. Doudna, Cheryl Grosshans, Anne Gooding, & Craig, E. Kundrot. PNAS (1993) 90, 7829-7833. Good Luck! Annie Hassell Glaxo Research Institute amh12478 at usav01.glaxo.com