Figure 4.

Circular dichroism (CD) characteristics of different quadruplexes and random library. (A) Parallel quadruplex shows positive peaks at 265 and 295 nm; (B) antiparallel quadruplex with glycosidic bond angles of the same orientation shows bimodal spectra as positive peaks at 265 nm and 295 nm of the same intensity; (C) antiparallel quadruplex with glycosidic bond angles of opposite orientation—the CD shows a negative peak at 265 nm and a positive peak at 295 nm; (D) random library shows a peak at 280 nm but no peaks at 265 nm and 295 nm, indicating the absence of a quadruplex. Figure adapted from McManus and Li [78].