一种与浓度无关的范式，使弱相互作用具有固有的可量化性
A concentration-independent paradigm rendering weak interactions inherently quantifiable
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中文总结 AI 辅助
该研究提出将实验控制从分子数转移到可及体积的新范式，利用DNA纳米腔实现空间限域，突破弱相互作用定量测量瓶颈，可量化毫摩尔级弱相互作用并筛选相关调节剂，为研究难及生化现象提供通用策略。
中文摘要 AI 辅助
大量具有毫摩尔亲和力的弱分子相互作用调控着细胞功能，但其定量表征在很大程度上超出了传统方法的适用范围。一个多世纪以来，生物化学一直沿用基于浓度的研究框架，其中摩尔浓度与单位体积内的分子数（N/V）成正比，实验通常（往往是隐含地）通过改变分子数N同时保持体积V固定来调控浓度。弱相互作用测量的瓶颈就源于这一范式：通过本体浓度读取弱结合需要超出实际限制的浓度，这是框架本身的约束而非仪器灵敏度的问题。本文表明，将实验控制从分子数N转移到可及体积V可克服这一瓶颈，并通过纳米级空间限域开辟此前难以企及的亲和力范围。控制V意味着控制生物化学家所称的“局部浓度”和“邻近效应”，将这些长期模糊的概念重塑为基于第一性原理的定量变量。该方法在DNA纳米腔中实现，结果显示仅几何排列就可 override 溶液相的结合层级。相同的空间控制量化了10 mM量级的蛋白质-肽相互作用，所用样品量为每孔飞摩尔级，每次滴定总量低于皮摩尔级。即便如此，标准酶标仪仍给出了近10³的信噪比，为检测更弱的相互作用留有空间。这种亲和力-几何读数还能实现蛋白质-蛋白质相互作用调节剂的合理筛选，通过重新权衡局部相遇而非自身紧密结合或形成稳定三元复合物，识别出能增强弱结合的化合物。总体而言，这种基于体积的范式及其实现为探测和调控此前难以企及的生化现象提供了通用策略。
英文摘要
A vast class of weak, millimolar-affinity molecular interactions governs cellular function, yet their quantitative characterization has remained largely beyond conventional methods. For over a century, biochemistry has worked within a concentration-based framework where molarity scales with molecular number per volume (N/V), and experiments have usually, often implicitly, changed concentration by moving N while holding V fixed. The weak-interaction measurement bottleneck arises from this paradigm: reading weak binding through bulk concentration requires concentrations beyond practical limits, a framework constraint rather than one of instrumental sensitivity. Here we show that shifting experimental control from N to accessible volume V overcomes this bottleneck and opens previously intractable affinity ranges through nanoscale spatial confinement. Controlling V means controlling what biochemists have called "local concentration" and "proximity effects," recasting these long-ambiguous notions as quantitative variables grounded in first principles. Implemented in DNA nanocavities, the approach showed that geometric arrangement alone can override solution-phase binding hierarchies. The same spatial control quantified a protein-peptide interaction of order 10 mM from femtomoles per well, totalling under a picomole per titration. Even so, a standard plate reader gave a signal-to-noise ratio near 10^3, leaving headroom for still weaker interactions. The affinity-and-geometry readout also enabled rational screening for protein-protein-interaction modulators, identifying compounds that enhance weak associations by reweighting local encounters rather than binding tightly on their own or forming a stable ternary complex. Together, this volume-based paradigm and its implementation provide a general strategy for probing and modulating previously inaccessible biochemical phenomena.
