Solid-phase synthesis, characterization and DNA binding properties of the first chloro(polypyridyl)ruthenium conjugated peptide complex

De novo design, synthesis and spectroscopic characterization of chiral benzimidazole-derived amino acid Zn(II) complexes: Development of tryptophan-derived specific hydrolytic DNA artificial nuclease agent

Novel ternary dizinc(II) complexes 1-3, derived from 1,2-bis(1H-benzimidazol-2-yl)ethane-1,2-diol and l-form of amino acids (viz., tryptophan, leucine and valine) were synthesized and characterized by spectroscopic (IR, (1)H NMR, UV-vis, ESI-MS) and other analytical methods. To evaluate the biological preference of chiral drugs for inherently chiral target DNA, interaction of 1-3 with calf thymus DNA in Tris-HCl buffer was studied by various biophysical techniques which reveal that all these complexes bind to CT DNA non-covalently via electrostatic interaction. The higher K(b) value of L-tryptophan complex 1 suggested greater DNA binding propensity. Further, to evaluate the mode of action at the molecular level, interaction studies of complexes 1 and 2 with nucleotides (5'-GMP and 5'-TMP) were carried out by UV-vis titrations, (1)H and (31)P NMR which implicates the preferential selectivity of these complexes to N3 of thymine rather than N7 of guanine. Furthermore, complex 1 exhibits efficient DNA cleavage with supercoiled pBR322. The complex 1 cleaves DNA efficiently involving hydrolytic cleavage pathway. Such chiral synthetic hydrolytic nucleases with asymmetric centers are gaining considerable attention owing to their importance in biotechnology and drug design, in particular to cleave DNA with sequence selectivity different from that of the natural enzymes.

DNA binding, oxidative DNA cleavage, cytotoxicity, and apoptosis-inducing activity of copper(II) complexes with 1,4-tpbd (N,N,N',N'-tetrakis(2-yridylmethyl)benzene-1,4-diamine) ligand

Three new binuclear copper(II) complexes have been synthesized and structurally characterized by X-ray crystallography, [Cu(2)(1,4-tpbd)(dafo)(2)(MeOH)(2)](ClO(4))(4)·2.5H(2)O (1), [Cu(2)(1,4-tpbd) (DMSO)(2)(ClO(4))(2)](OH)(2)·6H(2)O (2) and [Cu(2)(1,4-tpbd)(OAC)(2)(ClO(4))(2)]·5H(2)O (3) (1,4-tpbd=N,N,N',N'-tetrakis(2-pyridylmethyl)benzene-1,4-diamine). Complex 1 to 3 shows similar binuclear structure and each Cu atom adopts five-coordinated square-pyramidal geometry. The interactions of the three complexes with CT-DNA (Calf-thymus DNA) have been investigated by UV absorption, fluorescence spectroscopy, circular dichroism spectroscopy and viscosity. Furthermore, the three complexes display oxidative cleavage of supercoiled DNA in the presence of external agents. Complex 3 shows higher DNA affinity and nuclease activity may be attributed to its cis structural configuration and labile acetate and perchlorate anions. The cleavage mechanisms between the complexes and plasmid DNA are likely to involve singlet oxygen or singlet oxygen-like entity as reactive oxygen species. In addition, in vitro cytotoxicity studies on the Hela cell line show that the IC(50) values of complexes 1-3 are 14.75, 13.67 and 16.58 μM, respectively. The apoptosis-inducing activity was also assessed by AO/EB (Acridine Orange/Ethidium bromide) staining assay, indicating they have the potential to act as effective metal-based anticancer drugs.

Oligopyridine-ruthenium(II)-amino acid conjugates: synthesis, characterization, DNA binding properties and interactions with the oligonucleotide duplex d(5'-CGCGCG-3')2

Diastereomeric oligopyridine-ruthenium(II)-amino acid conjugated complexes of the general formulas Lambda- and Delta-[Ru(bpy)(2)(4,4'(CO(2)Y)(2)-bpy)](2+), where Y = L-AlaCONH(2), L-LysCONH(2), L-HisCONH(2), L-TyrCONH(2)), were synthesized and characterized. Their binding properties with ct-DNA and the oligonucleotide duplex d(5'CGCGCG-3')(2), by means of circular dichroism (CD), NMR spectroscopy and DNA thermal denaturation (T(m)) curves were studied. CD and T(m) data indicate that all diastereomeric complexes bind to the DNA major groove, Delta-diastereomers in a similar manner, while Lambda-diastereomers in dependence of the nature of the amino acid. NMR studies of d(5'CGCGCG-3')(2), and the complexes Delta-1, Delta-2, Lambda-1 and Lambda-2 indicate that Delta-1 and Delta-2 were bound having the ancillary bpy ligands towards the DNA groove, while the corresponding Lambda-1 and Lambda-2 were orientated in a similar way, facing the ligand 4,4'(CO(2)Y)(2)bpy towards the DNA major groove. Photoinduced DNA cleavage was observed in all cases studied, which take place through singlet oxygen production. Delta-4 and Lambda-4 show the lower photoinduced cleavage yield, probably because the singlet oxygen ((1)O(2)) oxidizes not only the DNA phosporodiesteric bonds but the tyrosine's phenolic OH bond as well.

Ruthenium(II) polypyridyl complexes: potential precursors, metalloligands, and topo II inhibitors

Neutral and cationic mononuclear complexes containing both group 15 and polypyridyl ligands [Ru(kappa3-tptz)(PPh3)Cl2] [1; tptz=2,4,6-tris(2-pyridyl)-1,3,5-triazine], [Ru(kappa3-tptz)(kappa2-dppm)Cl]BF4 [2; dppm=bis(diphenylphosphino)methane], [Ru(kappa3-tptz)(PPh3)(pa)]Cl (3; pa=phenylalanine), [Ru(kappa3-tptz)(PPh3)(dtc)]Cl (4; dtc=diethyldithiocarbamate), [Ru(kappa3-tptz)(PPh3)(SCN)2] (5) and [Ru(kappa3-tptz)(PPh3)(N3)2] (6) have been synthesized. Complex 1 has been used as a metalloligand in the synthesis of homo- and heterodinuclear complexes [Cl2(PPh3)Ru(micro-tptz)Ru(eta6-C6H6)Cl]BF4 (7), [Cl2(PPh3)Ru(mu-tptz)Ru(eta6-C10H14)Cl]PF6 (8), and [Cl2(PPh3)Ru(micro-tptz)Rh(eta5-C5Me5)Cl]BF4 (9). Complexes 7-9 present examples of homo- and heterodinuclear complexes in which a typical organometallic moiety [(eta6-C6H6)RuCl]+, [(eta6-C10H14)RuCl]+, or [(eta5-C5Me5)RhCl]+ is bonded to a ruthenium(II) polypyridine moiety. The complexes have been fully characterized by elemental analyses, fast-atom-bombardment mass spectroscopy, NMR (1H and 31P), and electronic spectral studies. Molecular structures of 1-3, 8, and 9 have been determined by single-crystal X-ray diffraction analyses. Complex 1 functions as a good precursor in the synthesis of other ruthenium(II) complexes and as a metalloligand. All of the complexes under study exhibit inhibitory effects on the Topoisomerase II-DNA activity of filarial parasite Setaria cervi and beta-hematin/hemozoin formation in the presence of Plasmodium yoelii lysate.

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.

Effects of Protonation on the Spectroscopic Properties of Tetrapyridoacridine (TPAC) Mono- and Dinuclear Ru(II) Complexes in Their Ground and 3MLCT Excited States

The spectroscopic behavior of mono- and dinuclear Ru(II) complexes (P, T, PP and TT, Figure 1) that contain the extended planar ligand tetrapyrido[3,2-a:2',3'-c:3' ',2' '-h:2' '',3' ''-j]acridine (TPAC) and either 1,10-phenanthroline (phen) or 1,4,5,8-tetraazaphenanthrene (tap) as ancillary ligands is examined in water and as a function of the pH. These four complexes luminesce in aqueous solution. The analyses of the data in absorption lead to the pKa values in the ground state, and the data in emission show that the excited 3MLCT states are much more basic than the ground state. When the complex contains tap ligands (T and TT), a decrease in pH transforms the luminescent excited basic form into another luminescent excited protonated species, which emits more bathochromically. In contrast, with phen ancillary ligands (P and PP), the protonated excited state does not luminesce. The rate constant of first protonation of the 3MLCT state is diffusion controlled, except for the dinuclear PP complex, whose protonation takes place on the nitrogen of the acridine motif. For P, in which the protonation process is the fastest, it would take place on the nitrogen atoms of the nonchelated phen moiety of the TPAC ligand. These results allow also us to gain information on the localization of the excited electron in the 1MLCT state populated upon absorption as well as in the relaxed 3MLCT emissive state. Moreover as these complexes are interesting for their study with DNA, it can be concluded from these data that a portion of the excited species in interaction with DNA will be protonated.

Synthesis, Characterization, and DNA-Binding Studies of Nitro(oligopyridine)ruthenium(II) Complexes

The complexes of general formulas [RuII(terpy)(4-CO2H-4'-Mebpy)(X)]n+ (X = NO (n = 3) and NO2 (n = 1); 1, 2) and [RuII(terpy)(4-COGHK-4'-Mebpy)(X)] (X = NO (n = 3) and NO2 (n = 1); 3, 4) were synthesized and characterized. The complex [RuII(terpy)(4-CO2-4'-Mebpy)(NO2)]_7.5H2O has also been characterized by X-ray crystallographic studies. It crystallizes in the triclinic system: a = 9.4982(1) A, b = 13.1330(1) A, c = 14.2498(2) A; alpha = 110.5870(6) x bc, beta = 98.4048(5) x bc, gamma = 106.4353(5), P1, Z = 2. The crystal structure reveals an extended hydrogen-bonding network. Two water molecules form strong hydrogen bonds with the nitro and the carboxylic oxygen atoms of two separate units of the complex, resulting in a dimeric unit. The dimers are bridged by a (H2O)15 cluster, consisting of two cyclo-(H2O)6 species, while an exo-H2O(8) connects them. Two more exo-H2O molecules are joined together and connect the cyclo-(H2O)6 units with the H2O(1) of the dimeric unit. It was found that complexes 1 and 3 can be transformed into their nitro derivatives in aqueous media at neutral pH. Photorelease of NO in dry MeCN solutions was observed for complexes 1 and 3. Also, complex 2 partially releases (NO2)- in MeCN upon visible light irradiation. Complex 2 interacts with short fragments (70-300 bp) of calf thymus DNA shortening slightly the apparent polynucleotide length, while the conjugation of the peptide GHK to it (2) affects its DNA-binding mode. The peptide moiety of complex 4 was found to interact with the DNA helix in a synergistic way with the whole complex. Preliminary results of photocleavage of DNA by complex 2 are also reported.

Oxidative DNA Cleavage Promoted by Multinuclear Copper Complexes: Activity Dependence on the Complex Structure

Polynuclear copper complexes with two or three Cu(BPA) (BPA, bis(2-pyridylmethyl)amine) motifs, [Cu2(mTPXA)Cl4]3 H2O (1), [Cu2(pTPXA)Cl4]3 H2O (2), [Cu3(HPTAB)Cl5]Cl3 H2O (3) (mTPXA = N,N,N',N'-tetra-(2-pyridylmethyl)-m-xylylene diamine; pTPXA = N,N, N',N'-tetra-(2-pyridylmethyl)-p-xylylenediamine; HPTAB = N,N,N',N',N'',N''-hexakis(2-pyridylmethyl)-1,3,5-tris-(aminomethyl)benzene) have been synthesized and characterized. The crystal structures of compounds 2 and 3 showed each Cu(BPA) motif had a 4+1 square-pyramidal coordination environment with one chloride occupying the apical position and three N atoms from the same BPA moiety together with another Cl atom forming the basal plane. Fluorescence and circular dichroism (CD) spectroscopy studies indicated that the DNA binding followed an order of 3>2>1 in the compounds. These complexes cleave plasmid pUC19 DNA by using an oxidative mechanism with mercaptopropionic acid (MPA) as the reductant under aerobic conditions. Dinuclear Cu2+ complexes 1 and 2 showed much higher cleavage efficiency than their mononuclear analogue [Cu(bpa)Cl2] at the same [Cu2+] concentration, suggesting a synergistic effect of the Cu2+ centers. Moreover, the meta-dicopper centers in complex 1 facilitated the formation of linear DNA. Interestingly, the additional copper center to the meta-dicopper motif in complex 3 decreased the cleavage efficacy of meta-dicopper motif in complex 1, although it is able to cleave DNA to the linear form at higher [Cu2+] concentrations. Therefore, the higher DNA binding ability of complex 3 did not lead to higher cleavage efficiency. These findings have been correlated to the DNA binding mode and the ability of the Cu2+ complexes to activate oxygen (O2). This work is a good example of the rational design of multinuclear Cu2+ artificial nuclease and the activity of which can be manipulated by the geometry and the number of metal centers.

A new family of ruthenium(II) polypyridine complexes bearing 5-aryltetrazolate ligands as systems for electrochemiluminescent devices

A new family of mono- and dinuclear ruthenium polypyridyl complexes containing 5-aryltetrazolate ligands such as the deprotonated form of 4-(1H-tetrazol-5-yl)benzonitrile (4-TBNH) and bis(1H-tetrazol-5-yl)benzene (BTBH(2)) have been synthesized and thoroughly characterized. The reactivity of the mononuclear species toward different electrophiles such as H(+) and CH(3)(+) has been investigated, and the effects of the resulting regioselective electrophilic attacks on the electronic and structural properties of the tetrazolate ligand have been studied by NMR ((1)H, (13)C) spectroscopy and X-ray crystal structures. Absorption and emission spectroscopy, together with an electrochemical and UV-vis-NIR spectroelectrochemical investigation of the uncoordinated ligand and complexes, has been performed, highlighting a rather good luminescence efficiency and a poor bridge-mediated electronic communication between the metal centers of the dinuclear complexes. The electrogenerated chemiluminescence (ECL) of the dinuclear species has been explored, and for one of these, an exceptionally high ECL efficiency has been observed, comparable to that of [Ru(bpy)(3)](2+), which is considered a standard in ECL studies.