(A), CD spectra of 5 μM HTG21 oligomer in non-ionic buffer (10 mM Tris–HCl buffer, pH 7.4), ionic buffer [10 mM Tris–HCl buffer (pH 7.4) containing 110 mM KCl], dialysis buffer, control system (dialysis buffer with 40% PEG), Xenopus laevis egg extract, and cell-free system (dialysis buffer with cell extract). (B), The FRET melting curves of HTG21G-quadruplex in ionic buffer, dialysis buffer, cell-free system, X. laevis egg extract, and control system.