Supramolecular Polymorphism of (G4C2)n Repeats Associated with ALS and FTD

Guanine-rich DNA sequences self-assemble into highly stable fourfold structures known as DNA-quadruplexes (or G-quadruplexes). G-quadruplexes have furthermore the tendency to associate into one-dimensional supramolecular aggregates termed G-wires. We studied the formation of G-wires in solutions of the sequences d(G4C2)n with n = 1, 2, and 4. The d(G4C2)n repeats, which are associated with some fatal neurological disorders, especially amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), represent a challenging research topic due to their extensive structural polymorphism. We used dynamic light scattering (DLS) to measure translational diffusion coefficients and consequently resolve the length of the larger aggregates formed in solution. We found that all three sequences assemble into longer structures than previously reported. The d(G4C2) formed extremely long G-wires with lengths beyond 80 nm. The d(G4C2)2 formed a relatively short stacked dimeric quadruplex, while d(G4C2)4 formed multimers corresponding to seven stacked intramolecular quadruplexes. Profound differences between the multimerization properties of the investigated sequences were also confirmed by the AFM imaging of surface films. We propose that π-π stacking of the basic G-quadruplex units plays a vital role in the multimerization mechanism, which might be relevant for transformation from the regular medium-length to disease-related long d(G4C2)n repeats.

Studying the excited electronic states of guanine rich DNA quadruplexes by quantum mechanical methods: main achievements and perspectives

Calculations are providing more and more useful insights into the interaction between light and DNA quadruplexes.

DNA quadruplexes as molecular scaffolds for controlled assembly of fluorogens with aggregation-induced emission

Tetrapod DNA quadruplexes were designed for assembly and precise modulation of light emission of an oligonucleotide-grafted fluorogen with aggregation-induced emission.