Sequence-Selective Binding of Phenazinium Dyes Phenosafranin and Safranin O to Guanine−Cytosine Deoxyribopolynucleotides: Spectroscopic and Thermodynamic Studies

Abstract

The sequence selectivity of the DNA binding of the phenazinium dyes phenosafranin and safranin O have been investigated with four sequence-specific deoxyribopolynucleotides from spectroscopic and calorimetric studies. The alternating guanine-cytosine sequence selectivity of the dyes has been revealed from binding affinity values, circular dichroism, thermal melting, competition dialysis, and calorimetric results. The binding affinities of both the dyes to the polynucleotides were of the order of 10(5) M(-1), but the values were higher for the guanine-cytosine polynucleotides over adenine-thymine ones. Phenosafranin had a higher binding affinity compared to safranin O. Isothermal titration calorimetric studies revealed that the binding reactions were exothermic and favored by negative enthalpy and predominantly large positive entropy contributions in all cases except poly(dA)·poly(dT) where the profile was anomalous. Although charged, nonpolyelectrolytic contribution was revealed to be dominant to the free energy of binding. The negative heat capacity values obtained from the temperature dependence of enthalpy changes, which were higher for phenosafranin compared to safranin O, suggested significant hydrophobic contribution to the binding process. In aggregate, the data presents evidence for the alternating guanine-cytosine base pair selectivity of these phenazinium dyes and a stronger binding of phenosafranin over safranin O.

Thermodynamic investigations of ligand–protein interactions: Binding of the phenazinium dyes phenosafranin and safranin O with human serum albumin

“…The lower binding of SO over PSF to HSA may be correlated to lower extent of interaction compared to PSF due to steric bulk induced by two extra methyl groups. Lower affinity of SO to DNA has also been reported [24][25][26]. The number of binding sites for the two dyes on HSA was around 1.0 for 1:1 binding supporting the results from Job's plot analyses (not shown).…”

“…Both PSF and SO are used as bio-probes for determination of hyaluronic acid, inhibition of human ribonucleotide reductase, detection of double stranded DNA, molecular adhesive for protein immobilization, analysing membrane organization and heterogeneity, and in several other applications [17][18][19][20][21][22][23]. Both dyes bind strongly to DNA by intercalation exhibiting remarkable base sequence specificity making them potential candidates as DNA targeted therapeutic agents [24][25][26]. However, their interaction with proteins has not been investigated in details and only few reports are available on this aspect [27][28][29].…”

Calorimetric and thermal analysis studies on the binding of phenothiazinium dye thionine with DNA polynucleotides

“…Herrera and Chaires [19] have reported a pre-melting conformational transition in poly(dA).poly(dT) coupled to daunomycin binding. Similarly, the binding of several small molecule intercalators to poly(dA).poly(dT) [21][22][23][24] has been shown to be different from their binding to poly(dA-dT).poly(dA-dT) and this was hypothesized due to the release of bound water from the polynucleotide [19,21,25,26].…”

Effect of different concentration of TiO2 nanoparticles in phenosafranin dye-based organic photovoltaic device

“…An attempt has been made to analyze the role of NP on the electrical and optical properties. Also like our previous work [2,10], we have tried to work out the effect of NPs on the theoretical model [11] for a better realization.…”