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Highlights: [•] DHA and 9-OH DHA both induce the heme group of BHb. [•] DHA and 9-OH DHA both can change the polarity of BHb. [•] DHA and 9-OH DHA both make BHb unfolding. [•] The interaction between BHb and DHA is stronger than 9-OH DHA. [Copyright &y& Elsevier]

Highlights: [•] PG intercalated into the DNA helix. [•] The binding of PG and ct-DNA are partial intercalation mode. [•] Van der Waals forces are mainly between PG and ct-DNA in the present of EB. [•] The interaction follows the static quenching mechanism. [Copyright &y& Elsevier]

Abstract: A porphyrin meso-tetrakis{[4-(1-pyridyl)propoxy]phenyl}porphyrin (TPyPP) and its Ni complex (TPyPP(Ni)) have been synthesized and characterized by 1H NMR, UV–vis spectra. The interaction of two porphyrins with calf thymus-DNA (CT-DNA) has been explored by UV–vis, fluorescence and circular dichroic spectroscopy and viscosity measurements. The results suggest that these porphyrins can bind to DNA by the same binding mode. TPyPP outside binds by self-stack with DNA both at low drug load r (=[porphyrin]/[DNA]) and high drug load. Though TPyPP(Ni) has center metal nickel, binding mode with DNA has little difference compared with TPyPP, dominating out-binding mode with different direction along DNA. The binding constants of the TPyPP and TPyPP(Ni) to DNA were 4.65 × 105 M−1 and 3.2 × 105 M−1, respectively. A colored precipitate was found after time in two porphyrin''s viscosity measurement. The reasonable interpretation is the porphyrins with alkyl connected N-position of pyridine can strongly interact with the anionic phosphates of DNA and lead to hydrophobic complex. [Copyright &y& Elsevier]