DNA-binding geometry dependent energy transfer from 4′,6-diamidino-2-phenylindole to cationic porphyrins

A multi-spectroscopic and molecular docking approach for DNA/protein binding study and cell viability assay of first-time reported pendent azide bearing Cu(II)-quercetin and dicyanamide bearing Zn(II)-quercetin complexes

In the current study, one new quercetin-based Zn(II) complex [Zn(Qr)(CNNCN)(H2O)2] (Complex 1) which is developed by condensation of quercetin with ZnCl2 in the presence of NaN(CN)2 and Cu(II) complex [Cu(Qr)N3(CH3OH)(H2O)] (complex 2) which is developed by the condensation reaction of quercetin and CuCl2 in presence of NaN3, are thoroughly examined in relation to their use in biomedicine. The results of several spectroscopic studied confirm the structure of both the complexes and the Density Functional Theory (DFT) study helps to optimize the structure of complex 1 and 2. After completion of the identification process, DNA and Human Serum Albumin (HSA) binding efficacy of both the investigated complexes are performed by implementing a long range of biophysical studies and a thorough analysis of the results unveils that complex 1 has better interaction efficacy with the macromolecules than complex 2. The binding efficacy of complex 1 is comparatively higher towards both macromolecules because of its pure groove binding mode during interaction with DNA and the presence of an extra H-bond during connection with HSA. The experimental host-guest binding results is fully validated by molecular docking study. Interestingly complex 1 shows better antioxidant properties than complex 2, as well as quercetin, and it has strong anticancer property with minimal damage to normal cells, which is proved by the MTT assay study. Better DNA and HSA binding efficacy of 1 may be the reason for the better anticancer property of complex 1.

Interactions of porphyrins with DNA: A review focusing recent advances in chemical modifications on porphyrins as artificial nucleases

The advance of porphyrins as artificial nucleases along the years have developed a class of compounds having potential therapeutic applications. Being an extrovert of chemistry, a variety of chemical modifications have been done on porphyrin macrocycle in order to improve the spectroscopic properties and to adapt as artificial receptors that can recognize molecules. The last twenty years has witnessed broad research in the arena of porphyrin- DNA interactions and their evolution from simple to more complex entities. In this review, we summarize the recent advances in the porphyrin-based structural modifications, with a specific emphasis on various effects of porphyrin on DNA cleavage potency. We particularly detailed the nuclease activity of cationic and anionic porphyrins, porphyrin dimers and conjugates as well as heme proteins till the third generation porphyrins as artificial nucleases.

Quenching of Luminol Fluorescence at Nano-Bio Interface: Towards the Development of an Efficient Energy Transfer System

Surface modified colloidal gold (Au) and silver (Ag) nanoparticles (NPs) were used as efficient quenchers of luminol (LH₂) fluorescence either in homogeneous aqueous medium or its noncovalent assembly with bovine serum albumin (BSA). The mechanism as well as the extent of fluorescence quenching was found to be strongly dependent on the nature of the nanoparticles. While simple static type fluorescence quenching mechanism was perceived with AuNP, a more complex protocol involving quenching sphere model was envisaged for AgNP quenching. Nevertheless, the magnitude of Stern-Volmer (SV) quenching constant (K_SV ~ 10⁸-10¹⁰ M^-1) was calculated to be ca. 10⁴ times more for surface quoted NPs in comparison with BSA-NP bioconjugates system. On the other hand, a highly efficient (E ≈ 95%) energy transfer (ET) process was predicted for LH₂ captured in the hydrophobic assembly with BSA in presence of AgNP as an acceptor. The ET efficiency is critically dependent on the concentration of BSA and nicely correlated with the extent of NP surface coverage. However, fluorescence quenching on AuNP surface is relatively less responsive towards protein concentration, primarily due to the difference in surface activity as well as the mode of interaction of the protein with NPs. Graphical Abstract Energy transfer from excited luminol to metal nanoparticles is strongly modulated in presence of serum albumins.

Comparison of the Binding Geometry of Free-Base and Hexacoordinated Cationic Porphyrins to A- and B-Form DNA

Although the transition from B-DNA to the A-form is essential for many biological concerns, the properties of this transition have not been resolved. The B to A equilibrium can be analyzed conveniently because of the significant changes in circular dichroism (CD) and absorption spectrum. CD and linear dichroism (LD) methods were used to examine the binding of water-soluble meso-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP) and its derivatives, Co-TMPyP, with B- and A-calf thymus DNA. B- to A-transitions occurred when the physiological buffer was replaced with a water-ethanol mixture (∼80 v/v %), and the fluorescence emission spectra of TMPyP bound to DNA showed a different pattern under ethanol-water conditions and water alone. The featureless broad emission bands of TMPyP were split into two peaks near at 658 and 715 nm in the presence of DNA under an aqueous solution. In the case of an ethanol-water system, however, the emission bands are split in two peaks near at 648 and 708 nm and 656 and 715 nm with and without DNA, respectively. This may be due to a change in the solution polarity. On the basis of the CD and LD data, TMPyP interacts with B-DNA via intercalation at a low ratio under a low ionic strength, 1 mM sodium phosphate. On the other hand, the interaction with A-DNA (80 v/v % ethanol-water system) occurs in a nonintercalating manner. This difference might be because the structural conformations, such as the groove of A-DNA, are not as deep as in B-DNA and the bases are much more tilted. In the case of Co-TMPyP, porphyrin binds preferably via an outside self-stacking mode with B- and A-DNA.

In vitromembrane damage induced by half-fin anchovy hydrolysates/glucose Maillard reaction products and the effects on oxidative statusin vivo

Through induced H₂O₂generationin vitro, HAHp(9.0)-G MRPs increased the antioxidant status in normal mice after short-term intake.

Caffeine and sulfadiazine interact differently with human serum albumin: A combined fluorescence and molecular docking study

The interaction and binding behavior of the well-known drug sulfadiazine (SDZ) and psychoactive stimulant caffeine (CAF) with human serum albumin (HSA) was monitored by in vitro fluorescence titration and molecular docking calculations under physiological condition. The quenching of protein fluorescence on addition of CAF is due to the formation of protein-drug complex in the ground state; whereas in case of SDZ, the experimental results were explained on the basis of sphere of action model. Although both these compounds bind preferentially in Sudlow's site 1 of the protein, the association constant is approximately two fold higher in case of SDZ (∼4.0×10(4)M(-1)) in comparison with CAF (∼9.3×10(2)M(-1)) and correlates well with physico-chemical properties like pKa and lipophilicity of the drugs. Temperature dependent fluorescence study reveals that both SDZ and CAF bind spontaneously with HSA. However, the binding of SDZ with the protein is mainly governed by the hydrophobic forces in contrast with that of CAF; where, the interaction is best explained in terms of electrostatic mechanism. Molecular docking calculation predicts the binding of these drugs in different location of sub-domain IIA in the protein structure.

Real-time detection of DNA cleavage induced by [M(2,2'-bipyridine)2(NO3)](NO3) (M=Cu(II), Zn(II) and Cd(II)) complexes using linear dichroism technique

The catalytic effect of [M(2,2'-bipyridine)2(NO3)](NO3) (M(bpy)2, M=Cu(II), Zn(II) and Cd(II)) on the super-coiled and double stranded DNA (scDNA and dsDNA) was examined by electrophoresis and a real-time detection linear dichroism (LD) technique. Although the Cu(bpy)2 complex effectively cleaved both types of DNA, the other two complexes were inactive. This was explained by the electrochemical properties of the metal complexes. The Cu(bpy)2 complex exhibited a redox potential at -0.222V with a peak to peak separation of 0.201V, whereas the other two metal complexes did not undergo any redox reaction. Both electrophoresis and LD measurements revealed the superoxide radical, ·O2(-), to be responsible for DNA cleavage. A kinetic study using the LD technique showed that the cleavage of dsDNA consisted of two first order reactions. The fast reaction is believed to reflect the cleavage of one strand, whereas the slow reaction involves the cleavage of the complementary strand at or near the first cleaved site.

{2-[1-(3-Methoxycarbonylmethyl-1H-indol-2-yl)-1-methyl-ethyl]-1H-indol-3-yl}-acetic acid methyl ester (MIAM): its anti-cancer efficacy and intercalation mechanism identified via multi-model systems

{2-[1-(3-Methoxycarbonylmethyl-1H-indol-2-yl)-1-methyl-ethyl]-1H-indol-3-yl}-acetic acid methyl ester (MIAM) was provided as a DNA-intercalator. For the comprehensive evaluation of this new intercalator, an assay system consisting of cell, S180 mouse, healthy mouse, spectrum, non-spectrum, and gel electrophoresis models was constructed. On the cell (S180, K562, MCF-7, HeLa and HepG2) models, MIAM selectively inhibited the viability of HeLa. On the S180 mouse model, 0.89, 8.9, 89 and 890 μmol kg(-1) of MIAM dose-dependently inhibited the tumor growth. Even at a dose of 890 μmol kg(-1), MIAM did not damage the treated S180 mice. The safety of MIAM was supported by a high spleen index and an obvious increase of body weight of the treated S180 mice. On the healthy mouse model the LD(50) value of MIAM is higher than 890 μmol kg(-1). The ultraviolet (UV), fluorescence, circular dichroism (CD), relative viscosity, melting curve, and gel electrophoresis assays of DNA with or without MIAM consistently supported an intercalation mechanism for MIAM.