A rapid microfluidic mixer for high-viscosity fluids to track ultrafast early folding kinetics of G-quadruplex under molecular crowding conditions.

Tracking the folding kinetics of macromolecules under molecular crowding conditions represents a tremendous challenge due to the high viscosity of the solution. In this paper, we report a unique T-type microfluidic mixer with seven consecutive ω-shaped baffles for fast mixing of high-viscosity fluids. Numerical simulations and experimental characterizations proved that the micromixer could achieve a mixing time of 579.4 μs for solutions with viscosities about 33.6 times that of pure water. Over a 1000-fold improvement in mixing dead time was accomplished in comparison to those reported previously. We further used this highly efficient micromixer to track the early folding kinetics of human telomere G-quadruplex under molecular crowding conditions. Results indicated an exponential process in the initial folding phase of G-quadruplex, and the G-quadruplex formed a more compact structure under higher degrees of molecular crowding conditions.