Thermodynamic investigation of a new water-soluble porphyrin with calf thymus DNA

Abstract

KEYWORDSThe equilibrium binding of a new water-soluble tetra-cationic porphyrin, 5-(1-(4-carboxybutyl) pyridinium-4-yl)10,15,20-tris(1-methylpyridinium-4-yl) porphyrin (5-CBPyP) with calf thymus DNA in comparison with meso-tetrakis(4-N-methyl pyridinium)porphyrin (TMPyP) has been studied in 7.5 mM phosphate buffer, pH=7.2 and at various temperatures by UV-Vis absorption, fluorescence spectroscopies and viscosity measurement. The thermodynamic parameters were calculated by van't Hoff equation at various temperatures. The values of -137.13±1.22 kJ/mol and -337.21±4.75 J/mol.K for 5-CBPyP and -159.12±1.22 kJ/mol and -406.11±4.45 J/mol.K for TMPyP, were estimated for enthalpy and entropy changes of interaction, respectively. The data indicate that the process is exothermic and enthalpy driven suggesting that electrostatic forces play a considerable role in the interaction process. The results of spectroscopic techniques and viscosity measurement represent the intercalation mode of binding for both porphyrins and higher binding affinity of TMPyP respect to 5-CBPyP.

The G-triplex DNA could function as a new variety of DNA peroxidase

“…S10, ESI †), indicating a nonintercalative binding mode between hemin and DNA. 26 Interestingly, the G-T mutations in T2 and T3 decreased their interactions with hemin, and this decrease was consistent with that reported in previous studies. The significant changes in the emission spectra of hemin complexed with T1 indicated an evident change in the local environment of the G-triplex-bound hemin, while much smaller changes in the local environment of T2-bound hemin or T3-bound hemin could be deduced from the study.…”

Photoinduced Electron Transfer between Anionic Corrole and DNA

“…The Q-band absorptions are more intense compared to porphyrins. Titration of ct-DNA into a solution of Ga­(tpfc)­(SO 3 Na) 2 induces a 12.4% hypochromism, suggesting that Ga­(tpfc)­(SO 3 Na) 2 binds with ct-DNA via an outside binding mode, which may be due to the interactions between the anionic corrole and the negative phosphodiester groups of DNA, resulting in the lower intercalation tendency. ,, The hypochromism should be not attributed to the change of the solvent polarity after the addition of ct-DNA because no appreciable bathochromic shift was observed. , Furthermore, the critical concentration for aggregation of Ga­(tpfc)­(SO 3 Na) 2 is about 25 μM . The much lower concentration of Ga­(tpfc)­(SO 3 Na) 2 in our experiment should not induce the observed hypochromism as shown in Figure .…”

“…The much lower concentration of Ga­(tpfc)­(SO 3 Na) 2 in our experiment should not induce the observed hypochromism as shown in Figure . The intrinsic binding constant ( K b ) of Ga­(tpfc)­(SO 3 Na) 2 to ct-DNA can be obtained according to eq , where ε f and ε b are the extinction coefficients of Ga­(tpfc)­(SO 3 Na) 2 at the Soret-band absorption maximum of the free and bound species, respectively. ε a is the apparent extinction coefficient of Ga­(tpfc)­(SO 3 Na) 2 in the presence of ct-DNA, which is obtained by calculating ratio of observed absorbance of the mixed solution to the total corrole concentration.…”

“…31 The much lower concentration of Ga(tpfc)(SO 3 Na) 2 in our experiment should not induce the observed hypochromism as shown in Figure 2. The intrinsic binding constant (K b ) of Ga(tpfc)-(SO 3 Na) 2 to ct-DNA can be obtained according to eq 1 31,38…”

Synthesis and physico-chemical properties of a H-cardanol triazole zinc porphyrin conjugate

“…4. 32 To probe the hypothesis for the formation of the intermolecular ensemble shown in Fig. 5, we conducted solvatochromic studies on HTZPC 5 ( Fig.…”