title: Anomalously Rapid Hydration Water Diffusion Dynamics Near DNA Surfaces.
abstract: The emerging Overhauser effect dynamic nuclear polarization (ODNP) technique measures the translational mobility of water within the vicinity (5-15 Å) of preselected sites. The work presented here expands the capabilities of the ODNP technique and illuminates an important, previously unseen, property of the translational diffusion dynamics of water at the surface of DNA duplexes. We attach nitroxide radicals (i.e., spin labels) to multiple phosphate backbone positions of DNA duplexes, allowing ODNP to measure the hydration dynamics at select positions along the DNA surface. With a novel approach to ODNP analysis, we isolate the contributions of water molecules at these sites that undergo free translational diffusion from water molecules that either loosely bind to or exchange protons with the DNA. The results reveal that a significant population of water in a localized volume adjacent to the DNA surface exhibits fast, bulk-like characteristics and moves unusually rapidly compared to water found in similar probe volumes near protein and membrane surfaces. Control studies show that the observation of these characteristics are upheld even when the DNA duplex is tethered to streptavidin or the mobility of the nitroxides is altered. This implies that, as compared to protein or lipid surfaces, it is an intrinsic feature of the DNA duplex surface that it interacts only weakly with a significant fraction of the surface hydration water network. The displacement of this translationally mobile water is energetically less costly than that of more strongly bound water by up to several kBT and thus can lower the activation barrier for interactions involving the DNA surface.
authors.affiliation: Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106, United States.|National Biomedical Center for Advanced ESR Technology, Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14850, United States.
authors.forename: John M
authors.initials: JM
authors.lastname: Franck
authors.affiliation: Department of Chemistry, University of Southern California , Los Angeles, California, 90089 United States.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Ding
authors.affiliation: Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106, United States.|Pacira Pharmaceuticals, Inc. , San Diego, California, 92121 United States.
authors.forename: Katherine
authors.initials: K
authors.lastname: Stone
authors.affiliation: Department of Chemistry, University of Southern California , Los Angeles, California, 90089 United States.
authors.forename: Peter Z
authors.initials: PZ
authors.lastname: Qin
authors.affiliation: Department of Chemistry and Biochemistry, University of California , Santa Barbara, California 93106, United States.
authors.forename: Songi
authors.initials: S
authors.lastname: Han
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000235:genetics; D004058:Diffusion; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D012399:Rotation; D013113:Spin Labels; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D013113:Spin Labels; D014867:Water; D004247:DNA