The structural transition and compaction of human telomeric G-quadruplex induced by excluded volume effect under cation-deficient conditions

The structure polymorphism of human telomeric G-quadruplex (ht-quadruplex) is currently an important topic but remains controversy. Here, we present study of the ht-quadruplex under the cation-deficient but molecular crowding conditions by circular dichroism (CD), microchip electrophoresis (MCE) and UV-melting experiments. Our results show that with concentration increasing of poly(ethylene glycol) (PEG), the structural transition of ht-quadruplex occurs accompanied by structural compaction and enhanced stabilization, which may be caused by excluded volume effect. This work also demonstrates that ht-quadruplex can be well assembled without cations and the structure of ht-quadruplex is actually very complex in vivo.