Oxytricha nova quadruplex

S. Haider, G.N. Parkinson and S. Neidle, Crystal structure of the potassium form of an Oxytricha nova G-quadruplex, J. Mol. Biol., 2002, 320, 189-200. 

Structural model of the complex of the 3,6,9-trisubstituted acridine ligand (3) with the intramolecular basket quadruplex structure of the human telomeric sequence, (a) End-stacking with the terminal G-tetradpermits the substituent at the 9-position to interact with the flexible TTA loop structure in a specific manner, (b) X-ray structure of the complex of a di-substituted aninoalkylamido acridine (4) with the dimeric hairpin quadruplex structure derived from the Oxytricha nova sequence d(GGGGTTTTGGGG)2. The drug end-stacks and interacts extensively with the thymine loop ((a) Adapted from ref 25 and (b) from RCSB Protein Data Bank co-ordinates ILIH (ref 49)). 

Subsequently, two X-ray structures have been reported one of a drug-bound dimeric anti-parallel G-quadruplex containing the Oxytricha nova sequence d(GGGGTTTTGGGG) in which a di-substituted aminoalkylamido acridine drug (4, see Figure 2) end-stacks with a terminal G-tetrad and interacts with one of the loops." In the other structure a daunomycin (14) trimer stacks on... 

Two G-quadruplex structures have been reported. The G-quadruplex from Oxytricha nova has been reported using thaUium as the monovalent binding metal, containing five Tl(i) ions. The ohgonucleotide d(G4T3G4) forms a bimolecular... 

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