An ellipticine derivative (oxazolopyridocarbazolium) 3' linked to tetrathymidylate stacks intramolecularly with the nearest thymine at low concentration and head-to-tail intermolecularly at high concentration.
The solution conformation of a tetrathymidylate linked through an ester bond to an ellipticine derivative oxazolopyridocarbazolium (OPC) at the 3' position was investigated using one- and two-dimensional nmr experiments. Since the total electric charge of the OPC ring may influence self-association, we first determined the pKa of the oxazole cyclic acidic function. Nuclear Overhauser effect spectroscopy experiments showed that, at low concentration, the OPC stacks intramolecularly with the nearest thymine at the 3' end. At highest concentration, however, the OPC rings are self-associated. The stacking constant was calculated using 1H chemical shift dilution experiment. The conformational model suggested by P-nmr was tested by molecular mechanics computations.
Bazile
D
D
Laboratoire de Biochimie Enzymologie, INSERM U 140, CNRS URA, Institut G, Roussy, France.
Guittet
E
E
Piriou
J M
JM
Lebret
M
M
Paoletti
J
J
D000470:Alkaloids; D002227:Carbazoles; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003855:Deoxyribose; D004611:Ellipticines; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D015394:Molecular Structure; D009841:Oligonucleotides; D013941:Thymine
D000470:Alkaloids; D002227:Carbazoles; D004611:Ellipticines; D009841:Oligonucleotides; C061416:oxazolopyridocarbazole; C064966:tetrathymidylic acid; D003855:Deoxyribose; D013941:Thymine