Metal-Nucleic acid

Metal-Nucleic AcidRNA (& DNA) structures

Where can metal ions interact in these nucleic acid polymers?Typical modes of metal ion binding1. phosphates2. bases3. intercalationBinding to either the phosphate groups or by intercalation is typically non-specific; i.e., it does not depend on a particular base sequenceBinding to the bases will depend on the type of bases that are present

Nucleosides are composed of a ribose or deoxyribose sugar, and a heterocyclic base

Nucleosides (RNA)

Deoxynucleosides (DNA)Pyrimidines - cytocine and uric acidPurines - adenine and guanine

NucleosidesBase + SugarNucleotides (and deoxynucleotides) are nucleosides that contain one or more phosphate groups

NucleotidesBase + Sugar + Phosphate

Metal-adenine complexes

Co(II)-adenine[Co(adenine)2(H2O)4]2+Metal-adenine complexes

Cu(II)-adenineIn each case N9 plays the major role in metal ion bindingHowever, in nucleosides and nucleotides this position is blocked by a glycosidic bond to ribose[Cu2(Ad)4Cl2]Cl2Metal-methyladenine complexes

Cu(II)-9-methyladenine[Cu(9-MeAd)2(H2O)4]Cl2

Metal-methyladenine complexesPt(II)-9-methyladenineBlocking N9 leads to metal ion coordination at the next best site - N7Mo(II)-9-ethyladenine

Mo also coordinates to N7 (as well as N6) and forms the typical bridged complex to an adjacent Mo

Metal-nucleoside complex

Cu(II)-(glygly)cytidineBinding Cu to a dipeptide model compound allows only a single ligand position to interact at the N3 position of a pyrimidine nucleosidePreferred Bidentate Coordination Sites

RNA (& DNA) structures

Where can metal ions interact in these nucleic acid polymers?DNA Duplex StructuresDNA is typically found in a double stranded helixHowever, there are three different types of helices

Of these, the B form of DNA is the most common helix

This B-helix has a wide or major groove and a narrow or minor grooveIntercalation can occur in either of these grooves, but binding to the major groove is preferred