title: A universal description for the experimental behavior of salt-(in)dependent oligocation-induced DNA condensation.
abstract: We report a systematic study of the condensation of plasmid DNA by oligocations with variation of the charge, Z, from +3 to +31. The oligocations include a series of synthetic linear ε-oligo(L-lysines), (denoted εKn, n = 3–10, 31; n is the number of lysines with the ligand charge Z = n+1) and branched α-substituted homologues of εK10: εYK10, εLK10 (Z = +11); εRK10, εYRK10 and εLYRK10 (Z = +21). Data were obtained by light scattering, UV absorption monitored precipitation assay and isothermal titration calorimetry in a wide range concentrations of DNA and monovalent salt (KCl, CKCl). The dependence of EC50 (ligand concentration at the midpoint of DNA condensation) on C(KCl) shows the existence of a salt-independent regime at low C(KCl) and a salt-dependent regime with a steep rise of EC50 with increase of C(KCl). Increase of the ligand charge shifts the transition from the salt-independent to salt-dependent regime to higher C(KCl). A novel and simple relationship describing the EC50 dependence on DNA concentration, charge of the ligand and the salt-dependent dissociation constant of the ligand–DNA complex is derived. For the ε-oligolysines εK6–εK10, the experimental dependencies of EC50 on C(KCl) and Z are well-described by an equation with a common set of parameters. Implications from our findings for understanding DNA condensation in chromatin are discussed.
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551. korolev@ntu.edu.sg
authors.forename: Nikolay
authors.initials: N
authors.lastname: Korolev
authors.forename: Nikolay V
authors.initials: NV
authors.lastname: Berezhnoy
authors.forename: Khee Dong
authors.initials: KD
authors.lastname: Eom
authors.forename: James P
authors.initials: JP
authors.lastname: Tam
authors.forename: Lars
authors.initials: L
authors.lastname: Nordenskiöld
mesh_terms: D002151:Calorimetry; D011232:Chemical Precipitation; D004247:DNA / Q000737:chemistry*; D008024:Ligands; D008027:Light; D010316:Particle Size; D011107:Polylysine / Q000737:chemistry*; D011189:Potassium Chloride / Q000737:chemistry; D012542:Scattering, Radiation; D055672:Static Electricity
chemical_list: D008024:Ligands; D011107:Polylysine; D011189:Potassium Chloride; D004247:DNA