Piotr Lukasiak^2,3, Maciej Antczak³, Tomasz Ratajczak³, Marta Szachniuk^2,3, Ryszard W. Adamiak¹, Mariusz Popenda¹, Jacek Blazewicz^2,3

1. Laboratory of Structural Chemistry of Nucleic Acids , Institute of Bioorganic Chemistry, Polish Academy of Sciences, 61-704 Poznan, Poland
2. Laboratory of Bioinformatics, Institute of Bioorganic Chemistry, Polish Academy of Sciences, 61-704 Poznan, Poland
3. Institute of Computing Science, Poznan University of Technology, 60-965 Poznan, Poland

The authors would like to thank prof Eric Westhof for discussion and suggestions.

National Science Center Poland grant MAESTRO 2012/05/B/ST6/03026 (to R.W.A) and grant 2012/06/A/ST6/00384 (to M.K)