Hi Jens, You can try the free DS Visualizer: http://accelrys.com/products/discovery-studio/visualization-download.php It comes with a free molecular builder for proteins, dna/rna and ligands. Please note that if you do need to make anything more interesting (energy calculations, minimizations, md, etc) will then need a license. I hope this helps. Francisco Full Disclaimer: I do work for Accelrys. From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of jens j birktoft Sent: Wednesday, May 23, 2012 9:32 AM To: [log in to unmask] Subject: [ccp4bb] DNA/RNA modeling Hi everybody, Does anyone know of a (non-commercial) software that are suitable for modeling DNA/RNA structures. Coot is great, however I am looking something that allows more flexibility Thanks -- Jens J. Birktoft e-mail: [log in to unmask]<mailto:[log in to unmask]> slow-mail: 350 Central Park West, Suite 9F, New York, NY 10025 Phone: 212-749-5057