title: Depletion interactions and modulation of DNA-intercalators binding: Opposite behavior of the "neutral" polymer poly(ethylene-glycol).
abstract: In this work we have investigated the role of high molecular weight poly(ethylene-glycol) 8000 (PEG 8000) in modulating the interactions of the DNA molecule with two hydrophobic compounds: Ethidium Bromide (EtBr) and GelRed (GR). Both compounds are DNA intercalators and are used here to mimic the behavior of more complex DNA ligands such as chemotherapeutic drugs and proteins whose domains intercalate DNA. By means of single-molecule stretching experiments, we have been able to show that PEG 8000 strongly shifts the binding equilibrium between the intercalators and the DNA even at very low concentrations (1% in mass). Additionally, microcalorimetry experiments were performed to estimate the strength of the interaction between PEG and the DNA ligands. Our results suggest that PEG, depending on the system under study, may act as an "inert polymer" with no enthalpic contribution in some processes but, on the other hand, it may as well be an active (non-neutral) osmolyte in the context of modulating the activity of the reactants and products involved in DNA-ligand interactions.
authors.affiliation: Departamento de Física, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.
authors.forename: F A P
authors.initials: FA
authors.lastname: Crisafuli
authors.affiliation: Departamento de Química, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.
authors.forename: L H M
authors.initials: LH
authors.lastname: da Silva
authors.affiliation: Departamento de Química, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.
authors.forename: G M D
authors.initials: GM
authors.lastname: Ferreira
authors.affiliation: Departamento de Física, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.
authors.forename: E B
authors.initials: EB
authors.lastname: Ramos
authors.affiliation: Departamento de Física, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.
authors.forename: M S
authors.initials: MS
authors.lastname: Rocha
mesh_terms: D002151:Calorimetry; D004247:DNA / Q000737:chemistry*; D007364:Intercalating Agents / Q000737:chemistry*; D008024:Ligands; D011092:Polyethylene Glycols / Q000737:chemistry*
chemical_list: D007364:Intercalating Agents; D008024:Ligands; D011092:Polyethylene Glycols; D004247:DNA
keywords: depletion interactions; intercalation; microcalorimetry; optical tweezers; polyethylene-glycol (PEG)