Extended Data Fig. 7. Testing if DNA templates fold into G-quadruplex structures.

Template DNAs were 5’-end labelled with ³²P, incubated at 30 °C in buffer containing 100 mM of the indicated salt, and then subjected to electrophoresis in a polyacrylamide gel containing 100 mM of the same salt in both the gel and the running buffer. Gels were run in a warm room at 30 °C, the same temperature as the DNA replication reactions. In LiCl, oligonucleotides ran largely according to their length; there are small differences due to base composition (that is, the 72-nt dT72 has an electrophoretic mobility similar to that of the 90-nt 15xTEL and 15xTEL-noGQ oligos). In KCl and NaCl, two of the oligos – 9xTEL and 15xTEL – showed anomalously fast mobility due to G-quadruplex formation. M, DNA length standards purchased from IDT and then 5’-end labelled. For gel source data, see Supplementary Fig. 1.