Thermally Induced Transitions of d(G 4 T 4 G 3 ) Quadruplexes Can Be Described as Kinetically Driven Processes.

DNA sequences that are rich in guanines and can form four-stranded structures are called G-quadruplexes. Due to the growing evidence that they may play an important role in several key biological processes, the G-quadruplexes have captured the interest of several researchers. G-quadruplexes may form in the presence of different metal cations as polymorphic structures formed in kinetically governed processes. Here we investigate a complex polymorphism of d(G 4 T 4 G 3 ) quadruplexes at different K + concentrations. We show that population size of different d(G 4 T 4 G 3 ) quadruplex conformations can be manipulated by cooling rate and/or K + concentration. We use a kinetic model to describe data obtained from DSC, CD and UV spectroscopy and PAGE experiments. Our model is able to describe the observed thermally induced conformational transitions of d(G 4 T 4 G 3 ) quadruplexes at different K + concentrations.