Dimethyl sulfoxide (DMSO) is a stabilizing co-solvent for G-quadruplex DNA

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biophysics

Background:

• Guanine-rich oligodeoxyribonucleotides can form four-stranded G-quadruplex structures.
• The stability of these structures is crucial for their biological function and experimental manipulation.
• Co-solvents like dimethyl sulfoxide (DMSO) and urea are often used in nucleic acid studies but can affect DNA stability.

Purpose of the Study:

• To investigate the effect of dimethyl sulfoxide (DMSO) on the stability of various G-quadruplex DNA structures.
• To examine the combined effects of DMSO and urea on G-quadruplex stability.
• To understand the interactions between co-solvents, DNA, and stabilizing cations.

Main Methods:

• Thermal denaturation monitored by UV absorption to determine the melting temperature (Tm) of G-quadruplexes.
• Experiments were conducted with different concentrations of DMSO and urea, individually and in mixtures.
• Studies included various G-quadruplex forming sequences (HTel, G3T, TBA, Oxy-1.5, TG4T) in the presence of stabilizing cations (Na+, K+, NH4+).

Main Results:

• Increasing DMSO concentrations progressively increased the Tm of all studied G-quadruplexes, indicating enhanced stability.
• Urea destabilized the G-quadruplex structures, as evidenced by a decrease in Tm with increasing urea concentration.
• In the presence of urea, increasing DMSO concentrations counteracted urea's destabilizing effect, increasing the Tm of G-quadruplexes.

Conclusions:

• DMSO acts as a stabilizing agent for G-quadruplex DNA structures.
• DMSO and urea exhibit opposing effects on G-quadruplex stability, with DMSO mitigating urea's destabilization.
• These findings underscore the critical role of co-solvents and co-solutes in modulating the stability of guanine-rich DNA structures, particularly in experimental settings involving DMSO.