O. Bornet et al., SELECTIVELY C-13-ENRICHED DNA - C-13 AND H-1 ASSIGNMENTS OF A TRIPLE-HELIX BY 2-DIMENSIONAL RELAYED HMQC EXPERIMENTS, Journal of biomolecular NMR, 4(4), 1994, pp. 575-580
We present NMR studies of an intramolecular triple helix, the three st
rands of which have been linked by a hexaethylene glycol chain. To ove
rcome the generally encountered difficulties of assignment in the homo
pyrimidine strands, the carbon C1' of the pyrimidines were selectively
C-13-enriched. Assignments of the aromatic and sugar protons were obt
ained from NOESY-HMQC and TOCSY-HMQC spectra. We show that the recogni
tion of a DNA duplex by a third strand via tripler formation is easily
carried out in solution by observing the changes of the (1)H1'-(13)C1
' connectivities as a function of pH. Furthermore, the conformation of
the sugars has been found to be C2'-endo, on the basis of the couplin
g constant values directly measured in an HSQC spectrum.