Direct measurement of the dielectric polarization properties of DNA.

TitleDirect measurement of the dielectric polarization properties of DNA.
Publication TypeJournal Article
Year of Publication2014
AuthorsCuervo, Ana, Dans Pablo D., Carrascosa José L., Orozco Modesto, Gomila Gabriel, and Fumagalli Laura
JournalProc Natl Acad Sci U S A
Date Published2014 Sep 2
KeywordsAtomic Force, Bacteriophage T7, Capsid, Cations, Chemical, Dielectric Spectroscopy, DNA, DNA-Binding Proteins, Electrochemical Techniques, Ligands, Microscopy, Models, Nuclear Proteins, Viral

The electric polarizability of DNA, represented by the dielectric constant, is a key intrinsic property that modulates DNA interaction with effector proteins. Surprisingly, it has so far remained unknown owing to the lack of experimental tools able to access it. Here, we experimentally resolved it by detecting the ultraweak polarization forces of DNA inside single T7 bacteriophages particles using electrostatic force microscopy. In contrast to the common assumption of low-polarizable behavior like proteins (εr \~{} 2-4), we found that the DNA dielectric constant is \~{} 8, considerably higher than the value of \~{} 3 found for capsid proteins. State-of-the-art molecular dynamic simulations confirm the experimental findings, which result in sensibly decreased DNA interaction free energy than normally predicted by Poisson-Boltzmann methods. Our findings reveal a property at the basis of DNA structure and functions that is needed for realistic theoretical descriptions, and illustrate the synergetic power of scanning probe microscopy and theoretical computation techniques.