title: Atomic force microscopy analysis of intermediates in cobalt hexammine-induced DNA condensation.
abstract: The packaging pathway of cobalt hexammine-induced DNA condensation on the surface of mica was examined by varying the concentration of Co(NH3)6(3+) in a dilute DNA solution and visualizing the condensates by atomic force microscopy (AFM). Images reveal that cobalt hexammine-induced DNA condensation on mica involves well-defined structures. At 30 microM Co(NH3)6(3+), prolate ellipsoid condensates composed of relatively shorter rods with linkages between them are formed. At 80 microM Co(NH3)6(3+), the condensed features include toroids with average diameter of approximately 240 nm as well as U-shaped and rod-like condensates with nodular appearances. The results imply that the condensates, whether toroids, U-shaped or rod-like structures have similar intermediate state which includes relatively shorter rod-like segments. The average size of the condensed toroids after incubated at room temperature for 5 h (approximately 240 nm) is much larger than that incubated for 0.5 h (approximately 100 nm). The results indicate that the condensation of DNA by Co(NH3)6(3+) is a kinetic-controlled process.
authors.affiliation: Center for Molecular Sciences, Institute of Chemistry, The Chinese Academy of Sciences, Beijing, PR China.
authors.forename: D
authors.initials: D
authors.lastname: Liu
authors.forename: C
authors.initials: C
authors.lastname: Wang
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.forename: Z
authors.initials: Z
authors.lastname: Lin
authors.forename: Z
authors.initials: Z
authors.lastname: Tan
authors.forename: C
authors.initials: C
authors.lastname: Bai
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates; D000818:Animals; D002417:Cattle; D003035:Cobalt / Q000494:pharmacology*; D004247:DNA / Q000737:chemistry* / Q000187:drug effects* / Q000648:ultrastructure; D066298:In Vitro Techniques; D018625:Microscopy, Atomic Force; D009690:Nucleic Acid Conformation / Q000187:drug effects; D012996:Solutions
chemical_list: D000538:Aluminum Silicates; D012996:Solutions; C032300:hexaamminecobalt(II); D003035:Cobalt; D004247:DNA; C011934:mica