title: Controlled and reversible binding of positively charged quantum dots to lambda DNA.
abstract: Biomacromolecules/Nanomaterials bioconjugate complexes have many applications in the interdisciplinary research fields. Accessible and easy synthesis methods of these complexes are the key roles for these applications. High quality water-soluble surface-charged quantum dots (QDs) were successfully prepared via surface modification by amphiphilic surfactants. The positively charged QDs can interact with deoxyribonucleic acid (DNA) molecules to form QDs/DNA bioconjugates via self-targeting electrostatic force. The stability of these QDs/DNA bioconjugates is influenced by ionic strength and concentration of negative or neutral surfactants in the solution. High ionic concentration or ca. 10(-3) mol/L surfactants can break the interaction between the QDs and DNA molecules (Lambda DNA/Hind III Marker segments) and controllably release DNA molecules from these bioconjugates. The conformation of DNA molecules has little change during the binding and releasing process. The condensation of lambda DNA molecules can be induced by positively charged QDs. High resolution transmission electron microscopy experiments have revealed the different stages of DNA condensation process, showing the fine structures of QDs/DNA bioconjugates at biomolecular scale. A long chain DNA molecule starts to self-enwind and condense to a porous globule when it is exposing to positively charged QDs but there is no direct interaction between QDs and DNA at early stages of condensation. After the DNA molecule becomes a compact globule, QDs stick onto its surface via electrostatic force. The coil conformation of the DNA molecules can be recovered from globule structure after DNA molecules are controllably released from bioconjugate complexes. These QDs/DNA bioconjugates have great potential applications for gene delivery and at the same time the fluorescence of QDs can be utilized to monitor the DNA releasing process.
authors.affiliation: College of Chemistry and Molecular Sciences, and State Key Laboratory of Virology, Wuhan University, Wuhan 430072, PR China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.forename: Ming-Xi
authors.initials: MX
authors.lastname: Zhang
authors.forename: Zhi-Ling
authors.initials: ZL
authors.lastname: Zhang
authors.forename: Hai-Yan
authors.initials: HY
authors.lastname: Xie
authors.forename: Zhi-Quan
authors.initials: ZQ
authors.lastname: Tian
authors.forename: Kwok-Yin
authors.initials: KY
authors.lastname: Wong
authors.forename: Dai-Wen
authors.initials: DW
authors.lastname: Pang
mesh_terms: D010582:Bacteriophage lambda / Q000378:metabolism*; D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D004587:Electrophoresis, Agar Gel; D046529:Microscopy, Electron, Transmission; D036103:Nanotechnology / Q000379:methods*; D045663:Quantum Dots; D055672:Static Electricity; D013501:Surface-Active Agents / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D002593:Cetrimonium Compounds; D013501:Surface-Active Agents; D014867:Water; D004247:DNA; D000077286:Cetrimonium