Eickbush T H, Moudrianakis E N
Biophys J. 1977 Jun;18(3):275-88. doi: 10.1016/S0006-3495(77)85613-0.
Addition of the intercalating dye quinacrine to a low ionic strength solution of DNA in quantities sufficient to saturate the high affinity sites in the DNA will result in the accumulation of the DNA at the solution interface. This entrapment of DNA at the air-water interface has been assayed by the adsorption of DNA to untreated carbon-coated electron microscope grids touched to the solution surface. Other intercalating dyes can also bring about this entrapment, if they possess a side arm large enough to occupy one of the DNA grooves when the dye is intercalated into the DNA. The extension and unwinding of the DNA helix brought about by the intercalating chromophore of the dye molecules are not requirements for the entrapment process. Spermidine, a simple polyamine that will bind to the DNA minor groove but that has no intercalating chromophore, was found to bring about this entrapment. Even simple mono- and divalent cations in the absence of the above ligands were found to promote a low level of surface entrapment. A model for the entrapment of DNA at the air-water interface is proposed in which one (or both) of the hydrophobic grooves of the DNA becomes a surface-active agent as a consequence of the association of various ligands and charge neutralization.
向低离子强度的DNA溶液中加入足以饱和DNA高亲和力位点的嵌入染料喹吖因，会导致DNA在溶液界面处聚集。DNA在空气-水界面的这种截留现象已通过将未处理的碳涂层电子显微镜网格接触溶液表面来吸附DNA进行测定。如果其他嵌入染料具有足够大的侧链，当染料嵌入DNA时能够占据其中一个DNA凹槽，那么它们也能导致这种截留现象。染料分子的嵌入发色团引起的DNA螺旋的伸展和解旋并非截留过程的必要条件。亚精胺是一种简单的多胺，它会与DNA小沟结合，但没有嵌入发色团，却也能导致这种截留现象。甚至在没有上述配体的情况下，简单的单价和二价阳离子也被发现能促进低水平的表面截留。本文提出了一个DNA在空气-水界面截留的模型，其中由于各种配体的缔合和电荷中和，DNA的一个（或两个）疏水凹槽成为表面活性剂。
