title: Nanoparticle induced conformational change in DNA and chirality of silver nanoclusters.
abstract: Nano-clusters formed on macromolecular templates carry the symmetry information of the template. Templates with broken symmetry thus lead to formation of asymmetric clusters. In response, such clusters induce a compensatory stress on the embedded template. Silver nanoparticles grown on a covalently closed negatively supercoiled plasmid DNA (pUC19) exhibit chiral behavior and as a reciprocal response, one observes alteration in DNA conformation. The inference was drawn using gel mobility-shift studies in which a silver nanoparticle (but not ions) induces a mobility shift implying a drift from supercoiled to relaxed state of the plasmid. Supporting evidences for such structural alterations were obtained from circular dichroism (CD) and Fourier transform infrared spectroscopy (FT-IR). Silver ion and silver nanoparticles induce differential FT-IR signals reflected in the fingerprint regions 1720, 1666, 1611, 1529 cm(-1) that respectively corresponds to binding in GT, ATGC, C, and AC (A, T, G, and C representing the four nucleotides). Existence of CD signal in the silver plasmon region (350-550 nm) suggests formation of a chiral clustering of nanoparticles. The reciprocal effect on the covalently closed circular (CCC) pUC19 DNA, namely the transition to a relaxed state, can be regarded as a mimicry of the topological enzyme acting on such CCC DNA.
authors.affiliation: Department of Biochemistry, University of Calcutta, 35 Ballygunge Circular Road, Kolkata 700019, India.
authors.forename: Sarita
authors.initials: S
authors.lastname: Roy
authors.forename: Soumen
authors.initials: S
authors.lastname: Basak
authors.forename: Anjan Kr
authors.initials: AK
authors.lastname: Dasgupta
mesh_terms: D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D004587:Electrophoresis, Agar Gel; D053768:Metal Nanoparticles; D009690:Nucleic Acid Conformation; D012834:Silver / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013237:Stereoisomerism
chemical_list: D012834:Silver; D004247:DNA