Formation and stability of G-quadruplexes self-assembled from guanine-rich strands.

Electrospray ionization mass spectrometry (ESI-MS) was utilized to investigate the formation and stability of G-quadruplexes. For the 15 6-nt oligonucleotides tested, ESI-MS indicated that formation of a parallel tetramer quadruplex requires at least four continuous guanines in the 6-nt sequence. In addition, the G-rich strands prefer to employ "self-association" in the formation of the G-quadruplex rather than hybridized integration, and the thermodynamic-stability order of these three G-quadruplexes is Q(2)>Q(1)>Q(3).