We can reflect on our first order or base level experiences.

我们能反思基层的体验。

耶鲁公开课 - 死亡课程节选

That's because you have to satisfy this base pair matching in order to have hydrogen bonding in each of the struts of the ladder in order to form a stable structure.

NA双链要满足互补配对原则,以使碱基对之间,形成氢键,从而形成稳定的双链结构

耶鲁公开课 - 生物医学工程探索课程节选