Cationic microemulsion hosting polynucleotides: effect of NaCl on host and guest

PolyAT chemical denaturation in w/o microemulsion

“…differences of the conformational behaviour of polyAT in water solution and in CTAB/n-hexane/n-pentanol/water microemulsions. [24][25][26][27] More significant for consideration are the parameters R H and R OH . Based on the stoicheiometry of the protonationdeprotonation equilibria, their value should be 0.5, independent of the salt concentration since the number of moles of titratable sites (N1 of adenine or N3H of thymine) is half the number of moles of monomer units of polyAT.…”

“…Indeed, several properties of DNA and DNA model molecules have been shown to be modified by solubilization in the aqueous core of water-in-oil (w/o) microemulsions. [21][22][23][24][25][26][27] For instance, high molecular weight DNA and plasmid DNA 21,22,28 and model polynucleotides, 25,26 in either cationic or anionic microemulsions, undergo a structural transition from B-to c-form under conditions that do not induce such phenomenon in solution. Microemulsion solubilization also appears to have a stabilising effect against thermal denaturation of the B-double helix of poly(dA-dT).poly(dA-dT) (polyAT), since no melting was observed in cationic microemulsions in the whole accessible temperature range (283 Ä 336 K), even under conditions where in solution it occurs well below 336 K. 25 In addition, it has also been reported that modulation of the characteristic parameters of the microemulsion, i.e.…”

“…Microemulsion solubilization also appears to have a stabilising effect against thermal denaturation of the B-double helix of poly(dA-dT).poly(dA-dT) (polyAT), since no melting was observed in cationic microemulsions in the whole accessible temperature range (283 Ä 336 K), even under conditions where in solution it occurs well below 336 K. 25 In addition, it has also been reported that modulation of the characteristic parameters of the microemulsion, i.e. W 0 ( ¼ [H 2 O]/[surfactant]) and P 0 ( ¼ [co-surfactant]/[surfactant]) can modify the conformational properties of polyAT [25][26][27] or DNA. 21,22 In spite of these striking effects of the compartmentation, to the best of our knowledge, no publication has appeared dealing with the effects of pH on the properties of polynucleotides solubilized in w/o microemulsions.…”

Natural or synthetic nucleic acids encapsulated in a closed cavity of amphiphiles

“…233,234 The cationic quaternary w/o microemulsion CTAB/hexane/ pentan-1-ol/water was employed in a series of studies on synthetic DNAs, namely high molecular weight poly(dA-dT)?poly(dA-dT) and poly(dG-dC)?poly(dG-dC) (polyAT and polyGC, respectively, in the following). [235][236][237][238][239][240][241][242][243] The aim of these investigations was to detect if and how the constraints imposed by the microemulsive medium (constricted volume, curvature and charge of the micellar wall, and reduced water activity and dielectric constant) could modify the chemical reactivity and conformational or thermal stability of the polynucleotides relative to aqueous solutions. It is, for instance, well known that solvent characteristics, in particular dielectric constant, are key factors in determining the conformational behaviour of nucleic acids in solution 10,11,244 and thus polymorphs of DNAs that are unusual in aqueous solutions could easily be observable in the water pool of microemulsions (Fig.…”

Different factors affecting polyAT conformation in microemulsions: effects of variable P0 and KCl concentration

“…The comprehension of the forces driving such compaction phenomena is obviously of basic importance and microemulsions have been proposed as suitable model media to investigate the relevance of different parameters in inducing DNA condensation in restricted compartments. [4][5][6] Along this line of research, it has been reported that the model polynucleotide poly(dA-dT)Ápoly(dA-dT) (polyAT) of high molecular weight (0.9-1.9 Â 10 6 Da) in the cationic quaternary microemulsion CTAB/n-pentanol/n-hexane/water (CTAB ¼ hexadecyltrimethylammonium bromide) easily undergoes structural modifications under the influence of variable NaCl concentrations. 4 It has been found that up to NaCl concentrations of 0.20 M the solubilized polynucleotide remains in the B double helix form, while increasing the salt concentration to 0.35 M and beyond (up to 1.0 M) polyAT undergoes progressive condensation eventually leading to total compaction in the c(À) form.…”