Figure 7.

Illustrative diagram demonstrating the influence of different concentrations of Mg²⁺ and DNA on the processes of preparation, freezing-thawing and lyophilization of Td. (A) The balance between concentrations of Mg²⁺ and DNA strands when preparing Td. There is an appropriate range of Mg²⁺ concentrations for the successful assembly of Td. A higher concentration of Mg²⁺ (>10 mM) results in an apparent aggregation of the DNA, while a lower concentration of Mg²⁺ (<2 mM) leads to an insufficient assembly of Td. Similarly, if the concentration of DNA reaches the upper limit (20 μM), pronounced aggregation also makes the assembly fail. Therefore, successful self-assembly of the Td can only be achieved by maintaining the balance of the two ingredients. (B) Freeze-thawing has no influence on the structure of the formed Td (1), but lyophilization increases the risks of Td aggregation, which would be largely attenuated by reducing the concentration of Mg²⁺ in the initial prepared buffer (2).