A chlorite mineral surface actively drives the deposition of DNA molecules in stretched conformations

摘要

Muscovite mica is commonly used to immobilize DNA molecules onto a flat surface. This method, however, requires either the use of divalent cations in the buffer solution or the chemical modification of the surface. Here we show that DNA molecules have different binding affinities and assume different conformations when adsorbed to different layered minerals. In particular, the effect of biotite, muscovite, talc, brucite and chlorite upon DNA binding is investigated. Using atomic force microscopy it is possible to quantify the amount of DNA deposited onto a flat surface and it is experimentally confirmed that biotite, talc and brucite have a much higher affinity than muscovite (7-, 20- and 25- fold more volume of DNA deposited, respectively). The deposition of DNA onto chlorite presents areas (brucite-like) with high DNA coverage and areas (mica-like) where DNA molecules are absent. We regularly observed isolated DNA molecules that became stretched across these regions of low affinity. The stretching is not induced by the deposition procedure but is driven by the surface potential gradient between brucite-like and mica-like regions in chlorite. The active stretching of DNA on chlorite is a clear indication of the technological potential carried by these materials when used as substrates for biomolecules.