title: Conformational Changes Followed by Complete Unzipping of DNA Double Helix by Charge-Tuned Gold Nanoparticles.
abstract: The complete unzipping of DNA double helix by small size gold nanoparticles having weakly positive surface charge has been monitored using ensemble and single molecule fluorescence resonance energy transfer (smFRET) techniques. We believe, as the gold nanoparticles have positive charge on the surface, the DNA and nanoparticles were pulled together to form two single strands. The positively charged ligands on the nanoparticles attached to the DNA, and the hydrophobic ligands of the nanoparticles became tangled with each other, pulling the nanoparticles into clusters. At the same time, the nanoparticles pulled the DNA apart. The conformational changes followed by unzipping have been investigated for long DNA (calf thymus DNA) as well as for short DNA (∼40 base pair) using ensemble methods like circular dichroism (CD) spectroscopy, fluorescence intercalation assay, viscometric method, and single molecule FRET imaging. This observation not only reveals a new aspect in the field of nano-bio interface but also provides additional information about DNA dynamics.
authors.affiliation: Chemical Sciences Division, Saha Institute of Nuclear Physics , Kolkata, India.
authors.forename: Subhas C
authors.initials: SC
authors.lastname: Bera
authors.affiliation: Chemical Sciences Division, Saha Institute of Nuclear Physics , Kolkata, India.
authors.forename: Kasturi
authors.initials: K
authors.lastname: Sanyal
authors.affiliation: Chemical Sciences Division, Saha Institute of Nuclear Physics , Kolkata, India.
authors.forename: Dulal
authors.initials: D
authors.lastname: Senapati
authors.affiliation: Chemical Sciences Division, Saha Institute of Nuclear Physics , Kolkata, India.
authors.forename: Padmaja P
authors.initials: PP
authors.lastname: Mishra
mesh_terms: D000818:Animals; D020029:Base Pairing; D002417:Cattle; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D006046:Gold / Q000737:chemistry*; D007364:Intercalating Agents / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D014783:Viscosity
chemical_list: D007364:Intercalating Agents; D006046:Gold; D004247:DNA; C427203:calf thymus DNA