SUNY at Albany
June 19-23, 2001
Ions: the Underwear of DNA
A few years ago, in a meeting in Madrid, Paul Siegler was wondering about naked DNA. However DNA is never naked, it is always accompanied by ions. Recent high resolution work on DNA structures has uncovered that hydrated Mg ions interact preferentially with guanine on the major groove of DNA. In crystal structures the sites of interaction are further stabilized by phosphates in neighboring oligonucleotides in the crystal. Ca ions show a similar behavior, but are less precisely positioned. When guanine is either the terminal base or occupies an extra helical position, Mg ions may interact directly with the N7 atom of guanine. In the case of transition metals (Ni, Co, Zn, etc.), such sites are always occupied by ions even at very low ionic concentrations. Thus, when protein /DNA interactions are considered, DNA is not naked but carries its underwear: ions which should also be taken into account.
Juan A. Subirana
Departament d?Enginyeria Química, ETSEIB, Universitat Politecnica de Catalunya, Diagonal 647, E-08028 Barcelona, Spain email: email@example.com