Long-range fluorescence quenching of ethidium ion by cationic porphyrins in the presence of DNA

Enhancement of DNA-mediated Energy Transfer from Ethidium to meso-Tetrakis(N-methylpyridinium-4-yl)porphyrin by Ca2+Ion

“…(3) originated from the sphere of action quenching mechanism, which involves defining a critical distance within which the excited energy of the fluorophore is totally deactivated by the quencher. 24 Calculated σ values with respect to Ca 2+ concentration are shown in Figure 2(b). In the absence of Ca 2+ , the critical distance was 9.5 base-pairs or 32.3 Å, slightly larger than the 25-30 Å reported by Pasternak et al 24 The difference may have been due to the differences in the experimental conditions, such as the nature and concentration of the buffer.…”

“…24 Calculated σ values with respect to Ca 2+ concentration are shown in Figure 2(b). In the absence of Ca 2+ , the critical distance was 9.5 base-pairs or 32.3 Å, slightly larger than the 25-30 Å reported by Pasternak et al 24 The difference may have been due to the differences in the experimental conditions, such as the nature and concentration of the buffer. The distance increased almost linearly with increasing Ca 2+ concentration up to 40 mM, above which the slope flattened.…”

“…The critical transfer radii of such transition range from 10 to 100 Å. 24,25 For example, the excitation energy of ethidium can transfer to meso-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP) along a DNA stem when both molecules are simultaneously intercalated between the DNA base-pairs. 26 RET between other acceptors and donors which were physically complexed with DNA has been also reported.…”

Synthesis and structure of a new ternary monocopper(II) complex containing mixed ligands of 2,2′‐diamino‐4,4′‐bithiazole and picrate:in vitroanticancer activity, molecular docking and reactivity towards DNA

“…However, EB, which is one of the most sensitive fluorescence probes, emits intense fluorescence in the presence of DNA due to its strong intercalation between the adjacent DNA base pairs [43] and this enhanced fluorescence could be quenched by the addition of another molecule [44] owing to the decreasing binding sites of DNA available for EB. [44,45] Thus, EB can be used to probe the interaction of complexes with DNA. If the complex can intercalate into DNA, it will lead to a decrease in the binding sites of DNA available for EB, and hence to a quenching of fluorescence intensity of the EB-DNA system.…”

Synthesis of Novel Diselenide‐Linked Porphyrin Dimers under Phase‐Transfer Catalysis Condition and Their Interactions with DNA

“…Fluorescence spectroscopy was also applied to study the interactions of these porphyrin dimers with DNA [26]. The fluorescence emission spectra of 4a -4c (l em,max ¼ 659, 656, and 655 nm, resp.)…”