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.

Links

Publisher Full Text

Authors

Korolev N, Berezhnoy NV, Eom KD, Tam JP, Nordenskiöld L

Institution

School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551. korolev@ntu.edu.sg

Source

Nucleic acids research 40:6 2012 Mar pg 2808-21

MeSH

Calorimetry
Chemical Precipitation
DNA
Ligands
Light
Particle Size
Polylysine
Potassium Chloride
Scattering, Radiation
Static Electricity

Pub Type(s)

Corrected and Republished Article
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

22563605