Due to the small size of a nanoconfinement, the property of water contained inside is rather challenging to probe. Herein, we measured the amount of water molecules released during the folding of individual G-quadruplex and i-motif structures, from which water activities are estimated in the DNA nanocages prepared by 5 × 5 to 7 × 7 helix bundles (cross-sections, 9 × 9 to 15 × 15 nm). We found water activities decrease with reducing cage size. In the 9 × 9-nm cage, water activity was reduced beyond the reach of regular cosolutes such as polyethylene glycol (PEG). With this set of nanocages, we were able to retrieve the change in water molecules throughout the folding trajectory of G-quadruplex or i-motif. We found that water molecules absorbed from the unfolded to the transition states are much fewer than those lost from the transition to the folded states. The overall loss of water therefore drives the folding of G-quadruplex or i-motif in nanocages with reduced water activities.

由于纳米约束物的尺寸小，因此内部所含水的性质很难探测。在这里，我们测量了在单个G-四链体和i-基序结构折叠期间释放的水分子的量，据此，在5×5至7×7螺旋束制备的DNA纳米笼中，水的活性被估算出来（横截面， 9×9至15×15 nm）。我们发现水的活动随着网箱尺寸的减小而减少。在9×9 nm的笼子中，水活度降低，超出了常规溶质（如聚乙二醇（PEG））的范围。使用这组纳米笼，我们能够在G-四链体或i-基序的整个折叠轨迹中检索水分子的变化。我们发现，从展开状态过渡到过渡状态时吸收的水分子比从过渡状态过渡到折叠状态时丢失的水分子少得多。因此，水的总体损失驱使G-四链体或i-基序在纳米笼中折叠，水活度降低。