(A) Effect of temperature (25–100 °C) on the CD spectra of 90-bp duplex DNA containing the PDGF-A Pu41-mer. At 100 °C, the 90-bp duplex DNA still generates a strong G-quadruplex CD signal. (B) Nondenatured gel analysis of 60-mer G-rich single-stranded DNA containing the PDGF-A Pu41-mer (lane 1) and 60-bp double-stranded DNA, also containing the PDGF-A Pu41-mer (lanes 2 and 3). In lanes 1 and 2, the G-rich strand was 5′-end-radiolabeled with 32P, and the C-rich strand was 5′-end-radiolabeled with 32P in lane 3. (C) DMS footprinting of G-rich strands of 60-bp duplex DNA band 1 (lanes 1 and 2) and band 2 (lanes 3 and 4). Lane 5 shows the CT sequencing on the G-rich strand of the 60-bp duplex DNA. Open circles indicate the guanines that are fully protected, partially open circles indicate the guanines that are partially protected, and arrowheads indicate the guanines that are cleaved [56].