title: Polyplexes of poly(methylaminophosphazene): energetics of DNA melting.
abstract: The interaction of DNA with a synthetic biocompatible and biodegradable cationic polymer, poly(methylaminophosphazene) hydrochloride (PMAP·HCl), was investigated by high-sensitivity differential scanning calorimetry under conditions of strong and weak electrostatic interactions of the macroions. Thermodynamic parameters of the DNA double-helix melting were determined as a function of pH and the PMAP·HCl/DNA weight ratio. PMAP·HCL was shown to reveal two functions with respect to DNA: the polyelectrolyte function and the donor-acceptor one. The first function stabilizes the helical conformation of DNA, and the second one destabilizes it. The stabilizing effect of PMAP·HCl is of entropic origin, related to a displacement of mobile counterions from the DNA's nearest surroundings by the poly(methylaminophosphazene) charged groups. The donor-acceptor function of poly(methylaminophosphazene) dominates when its electrostatic interaction with DNA is either saturated (in the complex coacervate phase at high poly(methylaminophosphazene) concentrations) or completely suppressed (in a salt medium when the polycation carries a small charge). Under these conditions, poly(methylaminophosphazene) destabilizes DNA. It preferentially binds to the DNA coil form likely via the formation of multiple labile hydrogen bonds with the donor-acceptor groups of DNA.
authors.affiliation: A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov St. 28, 119991 Moscow, Russian Federation. burova@ineos.ac.ru
authors.forename: Tatiana V
authors.initials: TV
authors.lastname: Burova
authors.forename: Natalia V
authors.initials: NV
authors.lastname: Grinberg
authors.forename: Dzidra R
authors.initials: DR
authors.lastname: Tur
authors.forename: Vladimir S
authors.initials: VS
authors.lastname: Papkov
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Dubovik
authors.forename: Valerij Y
authors.initials: VY
authors.lastname: Grinberg
authors.forename: Alexei R
authors.initials: AR
authors.lastname: Khokhlov
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000494:pharmacology*; D002152:Calorimetry, Differential Scanning; D004247:DNA / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009690:Nucleic Acid Conformation / Q000187:drug effects; D009691:Nucleic Acid Denaturation / Q000187:drug effects; D009943:Organophosphorus Compounds / Q000494:pharmacology*; D009994:Osmolar Concentration; D011108:Polymers / Q000494:pharmacology*; D013816:Thermodynamics
chemical_list: D001672:Biocompatible Materials; D009943:Organophosphorus Compounds; D011108:Polymers; C561357:poly(methylaminophosphazene) hydrochloride; D004247:DNA