Molecular characterization of DNA double strand breaks with tip-enhanced Raman scattering

Abstract

DNA double strand breaks (DSBs) are deadly lesions that can lead to genetic defects and cell apoptosis. Techniques that directly detect DNA DSBs include scanning electron microscopy, atomic force microscopy (AFM), and fluorescence based approaches. While these techniques can be used to identify DSBs they provide no information on the molecular events occurring at the break. Tip-enhanced Raman scattering (TERS) can provide molecular information from DNA at the nanoscale and in combination with AFM provides a new way to visualize and characterize the molecular structure of DSBs. DSBs result from cleavage at the 3'- and 5'-bonds of deoxyribose upon exposure to UVC radiation based on the observation of P-O-H and methyl/methylene deformation modes enhanced in the TERS spectra. It is hypothesized that strand fragments are hydrogen-terminated at the lesion, indicating the action of free radicals during photon exposure. Individual DNA double strand breaks (DSBs) were first detected and located by atomic force microscopy, and the molecular structure of this damage was characterized with tip-enhanced Raman scattering (see picture) using a top-down configuration and a reflective substrate. The first experimental evidence is reported confirming that individual DSBs result from cleavage at the 3′- and 5′-bonds of deoxyribose upon exposure to ultraviolet C radiation. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.