Densities, ρ, kinematic viscosities, ν, and refractive indices, n
D, were determined for poly(ethylene glycol)
200 and 400 + 1,3-dioxolane, + 1,4-dioxane, + oxolane (tetrahydrofuran, THF), and + oxane (tetrahydropyran, THP) binary mixtures over the entire range of composition at 303.15 K and at atmospheric pressure.
The excess molar volumes,
, deviations in viscosities, Δη, and deviations in molar refractions, ΔR,
calculated from experimental measurements, are always negative. The results were correlated with the
Redlich−Kister polynomial. The McAllister multibody interaction model was used to correlate the
kinematic viscosities of liquid mixtures with mole fractions. The viscosity dependence on temperature
was investigated between 297.15 and 309.15 K for some solutions in a restricted composition range.
We studied the binding of two anthracycline drugs, Doxorubicin and Sabarubicin, to a model telomeric sequence 5'-d[GGG(TTAGGG)(3)]-3' (21-mer), assuming the basket G-quadruplex (G4) conformation in Na(+)-rich aqueous solution. We used an approach that combines spectroscopic and microcalorimetric techniques to obtain information about ground and excited state properties of the most stable complexes. Both drugs bind to the 21-mer in basket conformation and complexes of 1:1 and 2:1 drug : 21-mer stoichiometry coexist in solution. Binding constants were determined from fluorescence and isothermal titration calorimetry experiments. For both drugs association is driven by enthalpy and disfavoured by entropy in the case of two sequential binding events to different sites. The drug fluorescence is completely quenched in the 1:1 complex, most likely by electron transfer from the guanine system to the anthraquinone moiety, while part of the emission survives in the 2:1 complex. Circular dichroism (CD) of the individual complexes is dominated by the G-quadruplex signal in the UV and by the anthracycline signal in the near-UV and Vis region. The experimental CD spectra combined with conformational calculations at MM level and quantum mechanical calculation of the rotational strength of the electronic transitions afforded information on the binding geometries.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.