Binding, electrochemical activation, and cleavage of DNA by cobalt(II) tetrakis-N-methylpyridyl porphyrin and its beta-pyrrole brominated derivative

Cobalt-mediated oxidative DNA damage and its prevention by polyphenol antioxidants

Although cobalt is a required nutrient, it is toxic due to its ability to generate reactive oxygen species (ROS) and damage DNA. ROS generation by Co²⁺ often has been compared to that of Fe²⁺ or Cu⁺, disregarding the reduction potential differences among these metal ions. In plasmid DNA damage studies, a maximum of 15% DNA damage is observed with Co²⁺/H₂O₂ treatment (up to 50 μM and 400 μM, respectively) significantly lower than the 90% damage observed for Fe²⁺/H₂O₂ or Cu⁺/H₂O₂ treatment. However, when ascorbate is added to the Co²⁺/H₂O₂ system, a synergistic effect results in 90% DNA damage. DNA damage by Fe²⁺/H₂O₂ can be prevented by polyphenol antioxidants, but polyphenols both prevent and promote DNA damage by Cu⁺/H₂O₂. When tested for cobalt-mediated DNA damage affects, eight of ten polyphenols (epicatechin gallate, epigallocatechin gallate, propyl gallate, gallic acid, methyl-3,4,5-trihydroxybenzoate, methyl-4,5-dihydroxybenzoate, protocatechuic acid, and epicatechin) prevent cobalt-mediated DNA damage with IC₅₀ values of 1.3 to 27 μM and two (epigallocatechin and vanillic acid) prevent little to no DNA damage. EPR studies demonstrate cobalt-mediated formation of ^•OH, O₂^•-, and ^•OOH, but not ¹O₂ in the presence of H₂O₂ and ascorbate. Epigallocatechin gallate and methyl-4,5-dihydroxybenzoate significantly reduce ROS generated by Co²⁺/H₂O₂/ascorbate, consistent with their prevention of cobalt-mediated DNA damage. Thus, while cobalt, iron, and copper are all d-block metal ions, cobalt ROS generation and its prevention is significantly different from that of iron and copper.

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.

Novel water-soluble Cu(ii) complexes based on acylhydrazone porphyrin ligands for DNA binding and in vitro anticancer activity as potential therapeutic targeting candidates

Three novel water-soluble Cu(ii) complexes featuring miscellaneous acylhydrazone tricationic porphyrin ligands (named Cu-Por1, Cu-Por2 and Cu-Por3) were successfully prepared and isolated.

DNA binding and in vitro anticarcinogenic activity of a series of newfashioned Cu(II)-complexes based on tricationic metalloporphyrin salicyloylhydrazone ligands

Four novel water-soluble Cu(II) derivatives based on the meso-10, 15, 20-Tris (N-methyl-X-pyridyl)-5-(4'-salicyloylhydrazone) metalloporphyrin ligands (X=4, M=Zn(1) Co(2); X=2, M=Zn(3), Co(4)), have been prepared and isolated. Various physicochemical techniques indicate that complex 2 interacts with calf thymus DNA stronger than the others through partial intercalation, suggesting that Co(II) has no axial ligands at porphyrin core plays a crucial role, interestingly, 2 exhibits higher DNA binding affinity compared to 4, which could be ascribed to the influences of peripheral electronic effect of porphyrin ring. Cytotoxicity studies manifest all conjugates possess superior cytotoxicity towards non-small cell lung cancer (A549) and liver hepatocellular carcinoma (HepG2) but weak toxicity for human normal breast cells (Hs 578Bst) boiled down to the tumor selectivity of porphyrin. In addition, the IC₅₀ value of 1 is lower than its analogues against HepG2 cells when cultivated 72h, thus the effects of representative complex 1 on cell morphological and cell cycle have been tailed.

Synthesis, crystal structure and biological activities of a Ag(I) complex based on the V-shaped ligand 1,3-bis(1-benzylbenzimidazol-2-yl)-2-thiapropane

A new silver(I) complex with 1,3-bis(1-benzylbenzimidazol-2-yl)-2-thiapropane (bbbt) and crotonate ligands, with composition [Ag(bbbt)(crotonate)]·CH3CH2OH, has been synthesized and characterized by physicochemical and spectroscopic methods. Single-crystal X-ray diffraction revealed that the coordination environment of the silver(I) center can be described as a distorted tetrahedral geometry, the Ag(I) atom being coordinated by two oxygen atoms from a crotonate anion and two nitrogen atoms from a bbbt ligand. Experimental studies of the DNA-binding properties indicated that the free ligand and the silver(I) complex bind to DNA by intercalation, and the order of the binding affinity is silver(I) complex>free bbbt ligand. The Ag(I) complex exhibits scavenger properties for hydroxyl radicals in in vitro studies.

Selective octabromination of tetraarylporphyrins based on meso-substituent identity: Structural and electrochemical studies

Synthesis and isolation of selectively brominated tetraarylporphyrin derivatives is reported. Treatment with bromine of meso-5,10,15,20-tetrakis(3,4,5-trimethoxyphenyl)porphyrin (1) or meso-5,10,15,20-tetrakis(3,5-di-[Formula: see text]-butyl-4-hydroxyphenyl)porphinatocopper(II) (2-Cu) yields products octabrominated at the 2,6-positions of meso-aryl substituents [5,10,15,20-tetrakis(2,6-dibromo-3,4,5-trimethoxyphenyl)porphyrin, [Formula: see text]Br81] or macrocyclic [Formula: see text]-positions. The latter of these ([Formula: see text]-brominated) was identified as the oxoporphyrinogen 2,3,7,8,12,13,17,18-octabromo-5,10,15,20- tetrakis(3,5-di-[Formula: see text]-butyl-4-oxo-cyclohexa-2,5-dienylidene)porphyrinogen 3 obtained due to the adventitious oxidation and demetalation of 2-Cu, which could be alkylated at its macrocyclic nitrogen atoms yielding N[Formula: see text],N[Formula: see text],N[Formula: see text],N[Formula: see text]-tetrakis(4-bromobenzyl)-2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(3,5-di-[Formula: see text]-butyl-4-oxo-cyclo hexa-2,5-dienylidene)porphyrinogen 4. The former compound [Formula: see text]Br81 was complexed with Zn(II) ([Formula: see text]Br81-Zn) or Cu(II) ([Formula: see text]Br81-Cu) and could also be subjected to further bromination yielding 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(2,6-dibromo-3,4,5-trimethoxyphenyl)porphyrin, Br[Formula: see text]1. The effect on the electrochemical properties of the 2,6-bromophenyl-substituted porphyrin compounds over the more highly brominated products was assessed.

Mono-, bi- and multi-nuclear silver complexes constructed from bis(benzimidazole)-2-oxapropane ligands and methacrylate: syntheses, crystal structures, DNA-binding properties and antioxidant activities

Three mono-, bi- and multi-nuclear Ag(i) complexes have been synthesized and characterized systematically. The complexes bind to DNA in a intercalate mode. Complex2has the potential ability to scavenge hydroxyl radicals inin vitrostudies.

An IDB-containing low molecular weight short peptide as an efficient DNA cleavage reagent

We present poly(aspartic acid) grafting bis-amine conjugates as artificial nucleases, which can effectively induce double-strand DNA cleavage.

Electrocatalytic miRNA detection using cobalt porphyrin-modified reduced graphene oxide

Metalated porphyrins have been described to bind nucleic acids. Additionally, cobalt porphyrins present catalytic properties towards oxygen reduction. In this work, a carboxylic acid-functionalized cobalt porphyrin was physisorbed on reduced graphene oxide, then immobilized on glassy carbon electrodes. The carboxylic groups were used to covalently graft amino-terminated oligonucleotide probes which are complementary to a short microRNA target. It was shown that the catalytic oxygen electroreduction on cobalt porphyrin increases upon hybridization of miRNA strand (“signal-on” response). Current changes are amplified compared to non-catalytic amperometric system. Apart from oxygen, no added reagent is necessary. A limit of detection in the sub-nanomolar range was reached. This approach has never been described in the literature.

DNA-binding studies and antioxidant activities of two-, three- and four-coordinate silver(i) complexes containing bis(2-benzimidazolyl)aniline derivatives

Three novel structure Ag(i) complexes have been synthesized and characterized. The three ligands and Ag(i) complexes bind to DNA in an intercalation mode. The Ag(i) complexes have stronger ability of antioxidation for hydroxyl radical and superoxide radical.

Metal-mediated DNA damage and cell death: mechanisms, detection methods, and cellular consequences

Metal ions cause various types of DNA damage by multiple mechanisms, and this damage is a primary cause of cell death and disease.

Synthesis, Crystal Structures and DNA-Binding Properties of a Six-Coordinate Ternary Iron (III) Complex Formed with Tris(2-[N-Ethyl]Benzimidazylmethyl)Amine and Salicylate

A ternary Fe(III) complex with a tripodal ligand tris(2-[ N-ethyl]benzimidazlylmethyl)amine (Etntb) and salicylate, with composition [Fe(Etntb)(salicylate)](NO3)·MeOH, has been synthesised. Its crystal structure shows that the central Fe(III) atom is six-coordinated and forms a distorted octahedral structure. The DNA-binding properties of the Fe(III) complex have been investigated by spectrophotometric methods and viscosity measurements, and the results suggest that the Fe(III) complex binds to DNA via an intercalation binding mode. Additionally, the Fe(III) complex scavenges hydroxyl radicals in in vitro studies.

Synthesis, circular dichroism, DNA cleavage and singlet oxygen photogeneration of 4-amidinophenyl porphyrins

5,10,15,20-tetrakis(4-amidinophenyl)porphyrin (Por 1), its Zn complex (Por 2) and its conjugate with a tetraphenylporphyrin to form a bisporphyrin (Por 3) were prepared. The monomeric Por 1 and Por 2 showed both intercalative and external binding with DNA whereas only external DNA binding was seen in the bisporphyrin, Por 3 by circular dichroism and UV-vis. The DNA photocleavage activities of these porphyrins followed the order: Por 1 ~ Por 2 > Por 3, which did not correlate with their measured 1O2 production rates. It suggests 4-amidinophenylporphyrins are promising new photodynamic therapeutic agents.

Synthesis of novel diselenide-linked porphyrin dimers under phase-transfer catalysis condition and their interactions with DNA

Novel diselenide-linked porphyrin dimers were synthesized under phase-transfer catalysis conditions. The targeted compounds were characterized by (1)H-NMR, high-resolution mass spectrometry, UV/VIS and fluorescence spectroscopies, redox-potential measurements, and elemental analysis. The interaction of the title compounds with DNA was studied using UV/VIS, fluorescence, and circular dichroism (CD) spectroscopies. The relative rates of singlet-oxygen production from the diselenide-linked porphyrin dimers upon photoirradiation were also measured.

Synthesis, DNA-Binding, Cleavage, and Cytotoxic Activity of New 1,7-Dioxa-4,10-diazacyclododecane Artificial Receptors Containing Bisguanidinoethyl or Diaminoethyl Double Side Arms

Novel 1,7-dioxa-4,10-diazacyclododecane artificial receptors with two pendant aminoethyl (3) or guanidinoethyl (4) side arms have been synthesized. Spectroscopy, including fluorescence and CD spectroscopy, of the interactions of 3, 4, and their copper(II) complexes with calf thymus DNA indicated that the DNA binding affinity of these compounds follows the order Cu(2+)-4>Cu(2+)-3>4>3, and the binding constants of Cu(2+)-3 are Cu(2+)-4 are 7.2x10(4) and 8.7x10(4) M(-1), respectively. Assessment by agarose gel electrophoresis of the plasmid pUC 19 DNA cleavage activity in the presence of the receptors showed that the complexes Cu(2+)-3 and Cu(2+)-4 exhibit powerful supercoiled DNA cleavage efficiency. Kinetic data of DNA cleavage promoted by Cu(2+)-3 and Cu(2+)-4 under physiological conditions fit to a saturation kinetic profile with kmax values of 0.865 and 0.596 h(-1), respectively, which give about 10(8)-fold rate acceleration over uncatalyzed supercoiled DNA. This acceleration is due to efficient cooperative catalysis of the copper(II) center and the functional (diamino or bisguanidinium) groups. In-vitro cytotoxic activities toward murine melanoma B16 cells and human leukemia HL-60 cells were also examined: Cu(2+)-4 shows the highest activity with IC(50) values of 1.62x10(-4) and 1.19x10(-5) M, respectively.