Macromolecule condensates, phase separation, and membraneless compartments have become an important area of cell biology research where new biophysical concepts are emerging. This article discusses the possibility that condensates assemble on multivalent surfaces such as DNA, microtubules, or lipid bilayers by multilayer adsorption. Langmuir isotherm theory conceptualized saturable surface binding and deeply influenced physical biochemistry. Brunauer-Emmett-Teller (BET) theory extended Langmuir’s ideas to multilayer adsorption. A BET-inspired biochemical model predicts that surface-binding proteins with a tendency to self-associate will form multilayered condensates on binding surfaces. These “bound condensates” are expected to assemble well below the saturation concentration for liquid–liquid phase separation, so they can compete subunits away from phase-separated droplets and are thermodynamically pinned to the binding surface. Tau binding to microtubules is an interesting test case. The nonsaturable binding isotherm is reminiscent of BET predictions, but assembly of Tau-rich domains at low concentrations requires a different model. Surface-bound condensates may find multiple biological uses, particularly in situations where it is important that condensate assembly is spatially constrained, such as gene regulation.

大分子冷凝物，相分离和无膜隔室已成为细胞生物学研究的重要领域，新的生物物理概念正在涌现。本文讨论了冷凝物通过多层吸附在多价表面（例如DNA，微管或脂质双层）上组装的可能性。Langmuir等温理论将饱和表面结合概念化并深刻影响了物理生物化学。Brunauer-Emmett-Teller（BET）理论将Langmuir的思想扩展到了多层吸附。受BET启发的生化模型预测，具有自缔合趋势的表面结合蛋白将在结合表面上形成多层冷凝物。这些“结合的冷凝物”在液相-液相分离中的组装浓度远低于饱和浓度，因此它们可以竞争亚单位，使其远离相分离的液滴，并热力学固定在结合表面上。Tau结合微管是一个有趣的测试案例。非饱和结合等温线使人联想到BET的预测，但低浓度下富含Tau的结构域的组装需要不同的模型。表面结合的冷凝物可能具有多种生物学用途，特别是在冷凝物组装受到空间限制（例如基因调控）的情况下尤其如此。