DNA-binding and photocleavage studies of metallofluorescein–porphyrin complexes of zinc(II) and copper(II)

The DNA-binding behaviors of the fluorescein?Cporphyrinatozinc(II) complex Zn(Fl-PPTPP) (Fl-PPTPP?=?5-(4-fluoresceinpropyloxy)phenyl-10,15,20-triphenylporphyrin) and fluorescein?Cporphyrinatocopper(II) complex Cu(Fl-PPTPP) with calf thymus DNA (CT-DNA) were investigated by UV?CVis absorption titrations, fluorescence spectra, viscosity measurements, thermal denaturation and circular dichroism. The results suggest that both complexes interact with CT-DNA by intercalation. In addition, their photocleavage reactions with pBR322 supercoiled plasmid DNA were investigated. Both complexes exhibit significant DNA cleavage activity, and singlet oxygen may play an important role in these reactions.     

DNA interactions,photocleavage, and cytotoxicity of fluorescein–porphyrinatozinc complexes with different lengths of links

Three fluorescein–porphyrinatozinc complexes Zn(Fl-PPTPP) (1) (Fl-PPTPp?=?5-(4-fluoresceinpropyloxy)phenyl-10,15,20-triphenylporphyrin), Zn(Fl-HPTPP) (2) (Fl-HPTPp?=?5-(4-fluoresceinhexyloxy)phenyl-10,15,20-triphenylporphyrin) and Zn(Fl-DPTPP) (3) (Fl-DPTPp?=?5-(4-fluoresceindecoxy)phenyl-10,15,20-triphenylporphyrin) have been synthesized and characterized by elemental analysis, IR, UV/Vis, Electrospray mass spectra, and ¹H NMR. The DNA-binding behaviors of these complexes with calf-thymus DNA (CT-DNA) were investigated by UV–vis absorption titration, fluorescence spectra, viscosity measurements, thermal denaturation, and circular dichroism. The results suggest that 1, 2, and 3 interact with CT-DNA by intercalation, and the conformation of fluorescein–porphyrin hybrids is an important factor affecting the DNA-binding affinities. The DNA-binding affinities (K _b values) follow the order 1?>?2?>?3. In addition, their photocleavage reactions with pBR322 supercoiled plasmid DNA were investigated by gel electrophoresis. All complexes exhibit significant DNA cleavage activity. These complexes have cytotoxic activities against myeloma cell (Ag8.653) and gliomas cell (U251) lines. Complex 1 was the most potent antitumor agent among the three complexes.     

Sequence and linker dependent chiral dimerization of DNA–porphyrin conjugates

Circular dichroism (CD), UV–vis absorption, fluorescence, and resonance light scattering (RLS) spectroscopies were used to elucidate the role of the DNA sequence, linkers between DNA and porphyrin, and metal in the porphyrin coordination center on the self-assembly of DNA–porphyrin conjugates. A series of eight non-self-complementary DNA–porphyrin conjugates have been synthesized with zinc and free-base porphyrins covalently attached to the short ODNs (A₈ or T₈) via amide or phosphate linker. A small structural modification (e.g., amide linker replaced by the phosphate linker) showed a dramatic effect on the aggregation properties of DNA–porphyrin conjugates and greatly altered their spectroscopic properties. At low ionic strength, porphyrin aggregation was not observed for any conjugate. An increase in the ionic strength caused two out of eight conjugates to form chiral porphyrin dimers.     

Metal complexes and acid-base properties of Δ1 tetrahydrocannabinol

Despite very extensive efforts employing a wide variety of techniques and procedures, it has not been found possible to isolate solid metal ion complexes of Δ¹-tetrahydrocannabinol. Equilibria of Δ¹-tetrahydrocannabinol with protons and bivalent transition metal ions (Fe²⁺, Co²⁺, Cu²⁺), in t-butanol at 30·0° and ionic strength 0·015 M, have been investigated potentiometrically. The ligand behaves as a monovalent base. With respect to the variation of the metal ion with the same ligand, the stability increases in the order Fe < Co < Cu; this order is in accord with the Irving-Williams series.     

Organic–inorganic hybrids based on polyoxometalates and copper coordination complexes

Two new hybrids based on Keggin polyoxometalates have been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, TG analysis, and single-crystal X-ray diffraction. The crystal structure analyses reveal that complex 1 has an infinite 1D chain structure, constructed from [Cu(2,2′-bpy)(4,4′-bpy)(H₂O)] fragments and [H₂PMo₁₁VO₄₀]^2? building blocks. Complex 2 has a 2D molecular ladder structure, with a basic structural unit composed of one bis(µ-OH) dicopper(II) [Cu₂(OH)₂(H₂O)₂(4,4′-bpy)₃] fragment, one [HPMo₁₂O₄₀], and four water molecules. The [Cu₂(OH)₂(H₂O)₂(4,4′-bpy)₃] units connect alternately to form edge rails. The [HPMo₁₂O₄₀] clusters act as rungs of the ladder, linking pairs of Cu atoms from the two adjacent edge rails. The electrochemical behavior of the complexes in modified carbon paste electrodes and their electrocatalytic reduction of nitrite were investigated.     

Synthesis,characterization, crystal structure,and DNA binding of two copper(II)–hydrazone complexes

Two new Cu(II)–hydrazone complexes, [Cu(L)(Hbpe)ClO₄]·ClO₄·[Cu(L)Cl] (1) and [Cu(HL)₂]·1.5ClO₄·0.5OH (2) (where HL?=?(E)-N′-(1-(pyridine-2-yl)ethylidene)benzohydrazide and bpe = trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene), have been synthesized and characterized by physicochemical methods. The structures of the complexes have been established by single-crystal X-ray diffraction direct methods, which reveal that the metal ions have distorted square-pyramidal and square-planar geometries in 1, and a distorted octahedral geometry in 2. DNA binding of HL, 1, and 2, performed by UV–vis titration in tris-buffer medium, yielded binding constants, which are 9.5 × 10³, 1.88 × 10⁴, and 4.66 × 10⁴ M^?1, respectively. Viscosity measurements suggest a surface or groove-binding mode of interaction between CT-DNA with HL, 1, and 2.     

Synthesis,characterization and DNA-binding properties of mixed porphyrin–polypyridyl ruthenium(II) complexes

Two mixed porphyrin–polypyridyl Ru^II complexes [Ru(bpy)₂(MPyTPP)Cl]Cl (1) and [Ru(phen)₂(MPyTPP)Cl]Cl ( 2 ) (bpy=2,2-bipyridine; phen=1,10-phenanthroline; MPyTPP=5-monopyridyl-10,15,20–triphenylporphyrin) have been synthesized and characterized by elementary analysis, e.s.–m.s., cyclic voltammetry and u.v.–vis. spectroscopy. The DNA-binding properties of these complexes were investigated by electronic spectra, c.d. spectra and viscosity experiments. The results suggested that both complexes (1) and (2) bind to DNA in an outside binding mode. At the same time, theoretical calculations applying the ab initio and the density functional theory (DFT) methods were also performed, and the results showed that there is no good planarity on the main ligand MPyTPP of these complexes, and there are rather great distortion angles (dihedral angles ca. 72°) between the porphrin ring and each of the 10-, 15-, 20-phenyl groups. This may be the reason why the complexes bind to DNA in an outside mode, instead of an intercalative mode.     

Synthesis,DNA binding and cleavage studies of the copper(Ⅱ) complexes of PNA-cyclen conjugates

Two dinucleotide PNA-cyclen copper(II) complexes with α-PNA (P1) and classical PNA (P2) backbones were synthesized and characterized.The interactions between title complexes and DNA were investigated under physiological conditions.Fluorescence studies indicate that the binding ability of complex P1 to CT-DNA is as twice as that of P2.DNA melting experiments were also carried out and the results show that ΔTm caused by P1 is higher than that caused by P2.Agarose gel electrophoresis experiments demonstrate th...     

Metal complexes as ligands—VII: The chemistry of the monothiooxalate complexes

A synthesis of potassium monothiooxalate, K₂C₂SO₃, and its reactions with metal ions are reported. The spectroscopic properties of the complexes, M(C₂SO₃)_nⁿ⁻, for M  Ni(II), Cu(II), Zn(II) (n = 2); and M  Cr(III), Co(III), Fe(III) (n = 3) are indicative of (SO) chelated ligands while the Al(III) (n = 3) complex is an (OO) bonded chelate. The copper(II) complex undergoes an irreversible oxidation at 0.43 V. This oxidation is accompanied by reduction of the copper(II) and evolution of CO₂ and SCO.The inert cations which accompany the anionic monothiooxalate complexes are readily replaced by the coordinatively unsaturated (Ph₃P)₂M⁺, M  Ag(I), Cu(I) complex cations. The bridging of the monothiooxalate ligand in the resulting polynuclear complexes is of the type MOOC₂SOM′, M  Al(III), Fe(III), M′  Ag(I), Cu(I); M  Cr(III), M′  Cu(I) and MSOC₂O₂M′, M  Cr(III), Co(III), M′  Cu(I).     

Synthesis and reactivity of enediyne–nucleobase hybrids: effect of intramolecular π-stacking

Three distinct classes of nucleobase-containing enediynes 1–9 with varying nature of the linker have been synthesized to explore the effect of π-stacking interaction in accelerating the rate of Bergman cyclization (BC). Chemical reactivity study, both experimental and computations demonstrated the important role that aromatic π-stacking interactions between the appended nucleobases within an enediyne frame play in lowering the activation barrier of Bergman cyclization.     

Metal–base pairing in DNA

The use of DNA as a molecular wire in nanoscale electronic architectures would greatly benefit from its capability of sequence-specific self-assembly. Although single electrons and positive charges have been shown to be transmitted by natural DNA over a distance of several base pairs, the high ohmic resistance of unmodified oligonucleotides imposes a serious obstacle. Exchanging some or all of the Watson–Crick base pairs in DNA by metal complexes may solve this problem and evolve DNA-like materials with superior conductivity for future nano-electronic applications. The so-called metal–base pairs are formed from suitable transition metal ions and ligand-like nucleosides which are introduced into both of the two pairing strands by automated DNA synthesis. This review illustrates the basic concepts of metal–base pairing and highlights recent developments in the field.     

Water Soluble Nickel – metformin ternary complexes: Thermal,DNA binding and molecular docking studies

The Nickel (II) complexes [Ni(Cl)₂(metf)(o-phen)] (1), [Ni(Cl)₂(metf)(opda)] (2) , [Ni(Cl)₂(metf)(en)] (3) , [Ni(Cl)₂(metf)(2,2'-bipy)] (4) , (metf = metformin, o-phen = ortho-phenanthroline, opda = ortho-phenylenediamine, en = ethylenediamine, 2–2′ bipy = 2–2′ bipyridyl) were synthesized and characterized using LC–MS, elemental analysis, molar conductance measurements, TGA-DTA, IR spectroscopy, magnetic moment measurements and electronic spectroscopy. The central Ni²⁺ was found to be in octahedral geometry. The DNA interaction of these complexes have been studied by UV–visible absorption studies, fluorescence emission technique and viscosity measurement. The complexes showed absorption hyperchromism in UV–visible spectra with calf thymus DNA. The binding constants from UV–visible absorption studies were 7.42 × 10⁴, 0.74 × 10⁴, 3.19 × 10⁴, 5.9 × 10⁴ M⁻¹ for 1 , 2 , 3 and 4 , respectively and Stern-Volmer quenching constants from fluorescence studies were 0.16, 0.41, 0.23, 0.18, respectively. Viscosity measurements revealed that the binding of the complexes with DNA could be surface binding, mainly due to groove binding. The highest DNA cleavage activity of the complexes is recorded for complex 1 . The complexes were docked in to B-DNA sequence, 5′(D*AP*CP*CP*GP*AP*CP* GP*TP*CP*GP*GP*T)-3′ retrieved from protein data bank (PDB ID: 423D), using Discovery Studio 2.1 software. C Docker Intectraction energy of 1 , 2 , 3 and 4 complexes is 32.027, 31.427, 35.393 and 30.521 respectively. The highest docking score is seen for complex 3 .     

Metal–DNA Coordination-Driven Self-Assembly: A Conceptual Methodology to Expand the Repertoire of DNA Nanobiotechnology

The past several decades have witnessed a rapid revolution of DNA nanotechnology. DNA nanostructures are mainly synthesized with two approaches, by assembly of purely DNA-based nanostructures through complementary base pairing or grafting DNA onto nanoparticles (NPs). Despite the progress made, developing simple and universal methods for the synthesis of DNA nanoarchitectures with specific morphologies and functionalities is still a challenge. This article introduces the reader to a new biomimetic methodology that leads to the controlled synthesis of DNA nanoarchitectures based on metal–DNA coordination chemistry and, furthermore, demonstrates the broad biomedical applications of these functional materials. In particular, we highlight the coordination-driven 1) surface-functionalization of NPs with DNA molecules and 2) direct self-assembly of metal–DNA nanostructures. Finally, challenges and opportunities of this approach to develop nanobiotechnology are provided.     

Metal ion directed synthesis of 14–16 membered tetraimine macrocyclic complexes

A new series of 14–16 membered tetraazatetraimine macrocyclic complexes [ML1X2]-[ML3X2] [M=CoII, NiII and ZnII] and [CuL1]X2-[CuL3]X2 [X=Cl or NO3] have been synthesized by the template condensation of dibenzoylmethane with primary diamines in MeOH. The complexes were characterized by elemental analysis, i.r, 1H-n.m.r., e.p.r. and u.v-vis spectroscopy, as well as by conductivity and magnetic susceptibility measurements. The copper complexes exhibit square planar geometry, whereas an octahedral geometry is suggested for all other complexes.     

Sulfone–Metal Exchange and Alkylation of Sulfonylnitriles

The first general sulfone–metal exchange is described. Treating substituted 2-pyridylsulfonylacetonitriles with either BuLi or Bu₃MgLi generates metalated nitriles that efficiently intercept a variety of electrophiles to afford quaternary nitriles. The 2-pyridylsulfone is critical for the sulfone–metal exchange because chelation anchors the organometallic proximal to the electrophilic, tetrasubstituted sulfone to override complex-induced deprotonation. Alkylating commercial 2-pyridinesulfonylacetonitrile with mild bases, either K₂CO₃ or DBU, and subsequent sulfone–metal exchange and alkylation rapidly assembles quaternary nitriles by three alkylations, only one of which requires an organometallic reagent.     

Synthesis and Liquid Crystal Properties of Transition Metal Complexes of Mesotetra （4-n-myristyloxyphenyl） porphyrin

Transition metal complexes of meso-tetra (4-myristyloxyphenyl)porphyrin TMPPM′ [M′=Mn, Fe, Co, Ni, Cu, Zn ; TMPP=mesotetra (4-myristyloxyphenyl)porphyrin] have been synthesized and characterized by means of elemental analyses, UV-Vis spectra, infrared photoacoustic spectra, ^1H NMR spectra, molar conductance and differential scanning calorimetry(DSC). The ligand and the Zn complex show liquid crystalline behavior. According to the DSC thermogram of the Zn complex, it exhibits a lower phase transition temperature -7. 453℃ and a wide mesophase temperature span, 77℃.     

PVC-silica hybrids: effect of sol–gel conditions on the morphology of silica particles and thermal mechanical properties of the hybrids

Hybrid materials from poly(vinyl chloride) (PVC) and silica have been prepared using different conditions by the sol–gel technique. In situ generation of silica network in the PVC matrix was carried out by hydrolysis/condensation of tetraethoxysilane (TEOS) in the matrix. Morphology of the silica particles produced in hybrid films was studied by scattering electron microscopy. The shape of silica particle produced in the matrix was modified by carrying out the sol–gel process under steam on the hybrid films using TEOS. The films were subjected to strain conditions during this process, which produced lamellar shaped particles in the matrix. It was possible to produce platelet type of structure with different aspect ratio by changing the composition and the stress conditions on the films during the steaming process. Addition of a very small amount of γ-glycidoxypropyltrimethoxysilane as compatibilizer drastically reduced the silica particles size in the matrix to nano-level. Thermal–mechanical properties of some of these hybrids were studied and related to the composition, structure and inter-phase interaction between the silica and the matrix.     

Thermodynamic characterization of proflavine–DNA binding through microcalorimetric studies

The interaction of an important acridine dye, proflavine hydrochloride, with double stranded DNA was investigated using isothermal titration calorimetry and differential scanning calorimetry. The equilibrium constant for the binding reaction was calculated to be (1.60 ± 0.04) · 10⁵ · M⁻¹ at T = 298.15 K. The binding of proflavine hydrochloride to DNA was favored by both negative enthalpy and positive entropy contributions to the Gibbs energy. The equilibrium constant for the binding reaction decreased with increasing temperature. The standard molar enthalpy change became increasingly negative while the standard molar entropy change became less positive with rise in temperature. However, the standard molar Gibbs free energy change varied marginally suggesting the occurrence of enthalpy–entropy compensation phenomenon. The binding reaction was dominated by non-polyelectrolytic forces which remained virtually unchanged at all the salt concentrations studied. The binding also significantly increased the thermal stability of DNA against thermal denaturation.     

Synthesis and properties of covalently linked BF2–oxasmaragdyrin–porphyrin dyads and triad

Two covalently linked diphenyl ethyne bridged unsymmetrical dyads containing porphyrin and BF₂–oxasmaragdyrin and Zn(II)porphyrin and BF₂–oxasmaragdyrin units and one covalently linked triad containing Zn(II)porphyrin, porphyrin and BF₂–oxasmaragdyrin units were synthesized by coupling appropriate functionalized macrocycles under Pd(0) coupling reaction conditions. The dyads and triad were freely soluble in common organic solvents and confirmed by ES-MS spectra. 1D and 2D NMR techniques were used to characterize the dyads and triad. Absorption and electrochemical studies of dyads and triad showed the overlapping features of the constituted macrocycles indicating that the macrocycles retain their basic features in the dyads and triad. The BF₂–oxasmaragdyrin absorbs at lower energy and emits strongly in the visible region compared to porphyrin/Zn(II)porphyrin. Thus, BF₂–oxasmaragdyrin acts as energy acceptor and porphyrin/Zn(II) porphyrin act as energy donor in dyads and triad. The steady state and time-resolved fluorescence studies supported an efficient energy transfer from porphyrin/Zn(II)porphyrin to BF₂–oxasmaragdyrin unit in dyads and triad.