Complex pretransitional solution dynamics and LC behaviour of d(G4C2) and d(G4C2)4 DNA sequences

Beyond the well-known double-helix structure, guanine-rich DNA sequences can form higher-order structures, known as DNA quadruplexes. These structures play an important role in gene regulation and are associated with certain neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Although the LC phases of double-stranded DNA have been extensively studied, the self-assembly and LC behaviour of DNA quadruplexes remain largely unexplored. In this study, we investigated the DNA sequences d(G4C2) and d(G4C2)4, which exhibit supramolecular assembly. The focus of our study was to examine the effect of DNA concentration on the dynamics of DNA quadruplexes in the pretransitional I → LC region and to assess their ability to form LC phases at higher concentrations – conditions that better represent physiological environments. Measurements were performed using dynamic light scattering (DLS) and polarisation optical microscopy (POM). DLS was employed to study the dynamics of DNA quadruplexes in the pretransitional region, while POM was used to identify mesophases at higher concentrations. Our results indicate that the d(G4C2) and d(G4C2)4 sequences behave like typical polyelectrolytes and exhibit the potential to form LC phases.