Structure and function of "metalloantibiotics"

Conformational changes in DNA upon ligand binding monitored by circular dichroism

Circular dichroism (CD) spectroscopy is an optical technique that measures the difference in the absorption of left and right circularly polarized light. This technique has been widely employed in the studies of nucleic acids structures and the use of it to monitor conformational polymorphism of DNA has grown tremendously in the past few decades. DNA may undergo conformational changes to B-form, A-form, Z-form, quadruplexes, triplexes and other structures as a result of the binding process to different compounds. Here we review the recent CD spectroscopic studies of the induction of DNA conformational changes by different ligands, which includes metal derivative complex of aureolic family drugs, actinomycin D, neomycin, cisplatin, and polyamine. It is clear that CD spectroscopy is extremely sensitive and relatively inexpensive, as compared with other techniques. These studies show that CD spectroscopy is a powerful technique to monitor DNA conformational changes resulting from drug binding and also shows its potential to be a drug-screening platform in the future.

Bis{N-ethyl-2-[3-(hydroxyimino-κN)butan-2-ylidene]hydrazinecarbothioamide-κ2N2,S}nickel(II) dichloride

In the title complex, [Ni(C₇H₁₄N₄OS)₂]Cl₂, the Ni^II ion is six-coordinated in a distorted octa­hedral geometry by four N atoms from the two imine and two oxime groups, and two S atoms from the thione groups. Two chloride ions complete the asymmetric unit. In the crystal, mol­ecules are linked through N—H⋯Cl and O—H⋯Cl hydrogen bonds into an infinite chain propagating along [101].

Bis{2-[3-(hydroxyimino-κN)butan-2-ylidene]-N-methylhydrazinecarbothioamide-κ2N2,S}nickel(II) dichloride

The asymmetric unit of the title compound, [Ni(C₆H₁₂N₄OS)₂]Cl₂, contains two independent Ni^II complex cations and four chloride anions. Each Ni^II ion is six-coordinated in a distorted octa­hedral geometry by four N atoms from the two imine and two oxime groups and two S atoms from the thione group. In the crystal, the cations and anions are linked through N—H⋯Cl and O—H⋯Cl hydrogen bonds into infinite chains propagating along [10]. Weak inter­molecular C—H⋯O and C—H⋯Cl hydrogen bonds are also observed.

(E)-2-[(E)-3-(Hydroxyimino)butan-2-ylidene]-N-methylhydrazinecarbothioamide

In the title compound, C₆H₁₂N₄OS, an intra­molecular N—H⋯N hydrogen-bond is present giving rise to an S(5) ring motif. In the crystal, double-stranded chains propagating along [10] are formed via pairs of O—H⋯S and N—H⋯S hydrogen bonds. The chains are further stabilized by C—H⋯S interactions.

Mass spectrometic study of speciation in aluminium-fluoroquinolone solutions

Fluoroquinolones (FQLs) are synthetic antibacterial agents containing a 4-oxo-1,4-dihydroquinoline skeleton. When concomintantly administered with other drugs which may contain metal ions, particularly Al(3+) (antacids, phosphate binders, vaccines etc) they may form metal-drug complexes. Pharmacokinetic studies showed that aluminium-quinolone interactions lead to reduced bio- availability and altered activity of the drug with possible development of the toxic effects of aluminum ion. Reliable speciation in Al(3+) - quinolone systems at micromolar concentration level is needed to better understand pharmaco- and toxicokinetics of the FQLs in the presence of Al. In this work, the speciation in solutions containing Al(3+) and FQL family members (fleroxacin, moxifloxacin and ciprofloxacin) was studied by electrospray mass spectrometry (ESI-MS), ESI-MS/MS, and laser desorption ionization (LDI) MS. The dominating species identified in all the three Al(3+)-FQL solutions, at ca 30-50 µmol L(-1) total Al concentration and 2:1 to 1:3 metal-to-ligand ratio in the pH range 3.0- 6.0, were the ions related to the complexes AlL(2+), AlL(2)(+) and AlL(3)(0) (L = ligand in the monodeprotonated form). Mixed protonated and hydroxo complexes were also formed at lower and higher pH values respectively and, as expected, dimeric and polymeric species were not observed in ESI spectra. LDI measurements confirmed the existence of the mononuclear complexes found by ESI, and indicated the formation of polymeric species. The ion [2Al(3+) +5(-)](+) was identified with all three FQLs. This ionic species most probably arises from Al(2)L(2) by clustering with free ligand anions. Comparison of literature potentiometric data with mass spectral data indicated good agreement between speciation schemes. The obtained results suggest the presence of strong interaction between FQLs and Al(3+) which may be important in affecting absorption of these drugs in the gastrointestinal tract.

The effects of Bleomycin A5 on infantile maxillofacial haemangioma

Objective

To examine the effects of bleomycin A5 on infantile maxillofacial haemangiomas.

Methods

Bleomycin A5 was given by multiple intralesinoal injections and the dosage was given according to the age of the patient and size of the lesion. Parts of patients were accompanied by prednisone treatment(2-5 mg/kg, po, QOD.

Results

All the haemangiomas involuted completely after treated with bloemycin A5 with better recovery of skin color and less scar forming in small haemangiomas.

Conclusion

Infantile haemangioma could be effectively treated with bleomycin A5 without serious side effects.

Antibacterial dimeric copper(II) complexes with chromone-derived compounds

A new series of six chromone-derived compounds and their Cu(II) complexes have been synthesized and characterized by their physical, spectral and analytical data. The ligands and their Cu(II) complexes were screened for their in vitro antibacterial activity against four Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexneri) and two Gram-positive (Bacillus subtilis, Staphylococcus aureus) bacterial strains by agar-well diffusion method. The ligands were found to exhibit either no or low-to-moderate activities against one or more bacterial species whereas, the Cu(II) complexes exhibited moderate-to-high activity. The ligands which were inactive before complexation became active upon complexation with the Cu(II) metal ion and less active became more active.

Peptide antibiotic sensing and detoxification modules of Bacillus subtilis

Peptide antibiotics are produced by a wide range of microorganisms. Most of them target the cell envelope, often by inhibiting cell wall synthesis. One of the resistance mechanisms against antimicrobial peptides is a detoxification module consisting of a two-component system and an ABC transporter. Upon the detection of such a compound, the two-component system induces the expression of the ABC transporter, which in turn removes the antibiotic from its site of action, mediating the resistance of the cell. Three such peptide antibiotic-sensing and detoxification modules are present in Bacillus subtilis. Here we show that each of these modules responds to a number of peptides and confers resistance against them. BceRS-BceAB (BceRS-AB) responds to bacitracin, plectasin, mersacidin, and actagardine. YxdJK-LM is induced by a cationic antimicrobial peptide, LL-37. The PsdRS-AB (formerly YvcPQ-RS) system responds primarily to lipid II-binding lantibiotics such as nisin and gallidermin. We characterized the psdRS-AB operon and defined the regulatory sequences within the P(psdA) promoter. Mutation analysis demonstrated that P(psdA) expression is fully PsdR dependent. The features of both the P(bceA) and P(psdA) promoters make them promising candidates as novel whole-cell biosensors that can easily be adjusted for high-throughput screening.

Synthesis of metallocarbonyl substituted 1,2,3-triazole complexes via copper(I)-catalyzed azide–alkyne cycloaddition

(η5-C5H5)M(CO)x(η1-N-maleimidato) (M = Fe, x = 2; M = W, x = 3) complexes react with propargylamine and propargyl alcohol giving products from the Michael addition to the η1-N-maleimidato ligand. Metallocarbonyl compounds bearing a terminal alkyne group were reacted with organic azides affording corresponding 1,2,3-triazoles in high yields. One of these metallocarbonyl 1,2,3-triazoles (M = Fe, x = 2) was characterized by X-ray diffraction.

Ligational behavior of thiosemicarbazone, semicarbazone and thiocarbohydrazone ligands towards VO(IV), Ce(III), Th(IV) and UO2(VI) ions: synthesis, structural characterization and biological studies

Mono- and binuclear VO(IV), Ce(III), Th(IV) and UO(2)(VI) complexes of thiosemicarbazone, semicarbazone and thiocarbohydrazone ligands derived from 4,6-diacetylresorcinol were synthesized. The structures of these complexes were elucidated by elemental analyses, IR, UV-vis, ESR, (1)H NMR and mass spectra as well as conductivity and magnetic susceptibility measurements and thermal analyses. The thiosemicarbazone (H(4)L(1)) and the semicarbazone (H(4)L(2)) ligands behave as dibasic pentadentate ligands in case of VO(IV) and UO(2)(VI) complexes, tribasic pentadentate in case of Ce(III) complexes and monobasic pentadentate in case of Th(IV) complexes. However, the thiocarbohydrazone ligand (H(3)L(3)) acts as a monobasic tridentate ligand in all complexes except the VO(IV) complex in which it acts as a dibasic tridentate ligand. The antibacterial and antifungal activities were also tested against Rhizobium bacteria and Fusarium-Oxysporium fungus. The metal complexes of H(4)L(1) ligand showed a higher antibacterial effect than the free ligand while the other ligands (H(4)L(2) and H(3)L(3)) showed a higher effect than their metal complexes. The antifungal effect of all metal complexes is lower than the free ligands.

Cytotoxicity of the traditional chinese medicine (TCM) plumbagin in its copper chemistry

The anticancer traditional Chinese medicine (TCM), plumbagin (PLN), was isolated from Plumbago Zeylanica. Reaction of plumbagin with Cu(II) salt, afforded [Cu(PLN)(2)].2H(2)O (1). With 2,2'-bipyridine (bipy) as a co-ligand, PLN reacts with Cu(II) to give [Cu(PLN)(bipy)(H(2)O)](2)(NO(3))(2).4H(2)O (2). 1 and 2 were characterized by elemental analysis, IR, ESI-MS spectra. Their crystal structures were determined by single crystal X-ray diffraction methods. The in vitro cytotoxicity of PLN, 1 and 2 against seven human tumour cell lines was assayed. The metal-based compounds exhibit enhanced cytotoxicity vs. that of free PLN, suggesting that these compounds display synergy in the combination of metal ions with PLN. The binding properties of PLN, 1 and 2 to DNA were investigated through UV-vis, fluorescence, CD spectra, and gel mobility shift assay, which indicated that 1 and 2 were non-covalent binding and mainly intercalated the neighboring base pairs of DNA. PLN, 1 and 2 exhibit inhibition activity to topoisomerase I (TOPO I), but 1 and 2 were more effective than PLN.

Synthesis, cytotoxic activity, and DNA binding properties of copper (II) complexes with hesperetin, naringenin, and apigenin

Complexes of copper (II) with hesperetin, naringenin, and apigenin of general composition [CuL(2)(H(2)O)(2)] nH(2)O (1-3) have been synthesized and characterized by elemental analysis, UV-Vis, FT-IR, ESI-MS, and TG-DTG thermal analysis. The free ligands and the metal complexes have been tested in vitro against human cancer cell lines hepatocellular carcinoma (HepG-2), gastric carcinomas (SGC-7901), and cervical carcinoma (HeLa). Complexes 1 and 3 were found to exhibit growth inhibition of SGC-7901 and HepG2 cell lines with respect to the free ligands; the inhibitory rate of complex 1 is 43.2% and 43.8%, while complex 3 is 46% and 36%, respectively. The interactions of complex 1 and its ligand Hsp with calf thymus DNA were investigated by UV-Vis, fluorescence, and CD spectra. Both complex 1 and Hsp were found to bind DNA in intercalation modes, and the binding affinity of complex 1 was stronger than that of free ligand.

The impact of spermine competition on the efficacy of DNA-binding Fe(II), Co(II), and Cu(II) complexes of dimeric chromomycin A(3)

Chromomycin (Chro) forms a 2:1 drug/metal complex through the chelation with Fe(II), Co(II), or Cu(II) ion. The effects of spermine on the interaction of Fe(II), Co(II), and Cu(II) complexes of dimeric Chro with DNA were studied. Circular dichroism (CD) measurements revealed that spermine strongly competed for the Fe(II) and Cu(II) cations in dimeric Chro-DNA complexes, and disrupted the structures of these complexes. However, the DNA-Co(II)(Chro)(2) complex showed extreme resistance to spermine-mediated competition for the Co(II) cation. According to surface plasmon resonance (SPR) experiments, a 6mM concentration of spermine completely abolished the DNA-binding activity of Fe(II)(Chro)(2) and Cu(II)(Chro)(2) and interfered with the associative binding of Co(II)(Chro)(2) complexes to DNA duplexes, but only slightly affected dissociation. In DNA integrity assays, lower concentrations of spermine (1 and 2mM) promoted DNA strand cleavage by Cu(II)(Chro)(2), whereas various concentrations of spermine protected plasmid DNA from damage caused by either Co(II)(Chro)(2) or Fe(II)(Chro)(2). Additionally, DNA condensation was observed in the reactions of DNA, spermine, and Fe(II)(Chro)(2). Despite the fact that Cu(II)(Chro)(2) and Fe(II)(Chro)(2) demonstrated lower DNA-binding activity than Co(II)(Chro)(2) in the absence of spermine, while Cu(II)(Chro)(2) and Fe(II)(Chro)(2) exhibited greater cytoxicity against HepG2 cells than Co(II)(Chro)(2), possibly due to competition of spermine for Fe(II) or Cu(II) in the dimeric Chro complex in the nucleus of the cancer cells. Our results should have significant relevance to future developments in metalloantibiotics for cancer therapy.

Metalloantibiotics: synthesis, characterization and antimicrobial evaluation of bismuth-fluoroquinolone complexes against Helicobacter pylori

Novel organometallic compounds have been prepared by complexing the fluoroquinolones, norfloxacin, ofloxacin, ciprofloxacin, sparfloxacin, lomefloxacin, pefloxacin and gatifloxacin, with bismuth. The complexes were characterized by UV, IR, atomic absorption spectroscopy, elemental analysis, differential scanning calorimetry, thermogravimetric analysis and mass spectrometry. Their antibacterial potential against Helicobacter pylori and other microorganisms was investigated. These compounds were found to possess strong activity against Helicobacter pylori with a minimum inhibitory concentration of 0.5 mg L-1. They also exhibited moderate activity against Escherichia coli, Staphylococcus aureus, Bacillus pumilus and Staphylococcus epidermidis. These bismuth-fluoroquinolone complexes have the potential to be developed as drugs against H. pylori related ailments.

Use of suppression subtractive hybridization to identify genetic differences between differentially virulent genotypes of Paenibacillus larvae, the etiological agent of American Foulbrood of honeybees

Paenibacillus larvae is the causative agent of American Foulbrood of honeybees, a fatal brood disease not only killing infected larvae but also lethal to infected colonies. Recently four different genotypes of P. larvae (enterobacterial repetitive intergenic consensus I-IV) have been described and it was shown that these genotypes also differ in phenotype, especially in virulence. To unravel the genetic differences between these four genotypes, suppression subtractive hybridization was used. From 106 analysed clones, 92 represented genotype-specific sequences, whereas 14 sequences turned out to be specific only for the particular strain used as tester in the subtraction. Nearly half of the sequences (46%) could only be annotated based on poorly characterized sequences. The remaining sequences corresponded to categories related to metabolism, especially secondary metabolite biosynthesis, transport and catabolism, to information storage and processing, and to cellular processes. In particular, we could show that the P. larvae genome contains genes and/or giant gene clusters coding for antibiotics, and we identified the first P. larvae toxin, a member of the family of adenosine diphosphate-ribosyltransferases.

Effects of polyamines on the DNA-reactive properties of dimeric mithramycin complexed with cobalt(II): implications for anticancer therapy

Few studies have examined the effects of polyamines on the action of DNA-binding anticancer drugs. Here, a Co(II)-mediated dimeric mithramycin (Mith) complex, (Mith)(2)-Co(II), was shown to be resistant to polyamine competition toward the divalent metal ion when compared to the Fe(II)-mediated drug complexes. Surface plasmon resonance experiments demonstrated that polyamines interfered with the binding capacity and association rates of (Mith)(2)-Co(II) binding to DNA duplexes, while the dissociation rates were not affected. Although (Mith)(2)-Co(II) exhibited the highest oxidative activity under physiological conditions (pH 7.3 and 37 degrees C), polyamines (spermine in particular) inhibited the DNA cleavage activity of the (Mith)(2)-Co(II) in a concentration-dependent manner. Depletion of intracellular polyamines by methylglyoxal bis(guanylhydrazone) (MGBG) enhanced the sensitivity of A549 lung cancer cells to (Mith)(2)-Co(II), most likely due to the decreased intracellular effect of polyamines on the action of (Mith)(2)-Co(II). Our study suggests a novel method for enhancing the anticancer activity of DNA-binding metalloantibiotics through polyamine depletion.

Fate and transport of antibiotic residues and antibiotic resistance genes following land application of manure waste

Antibiotics are used in animal livestock production for therapeutic treatment of disease and at subtherapeutic levels for growth promotion and improvement of feed efficiency. It is estimated that approximately 75% of antibiotics are not absorbed by animals and are excreted in waste. Antibiotic resistance selection occurs among gastrointestinal bacteria, which are also excreted in manure and stored in waste holding systems. Land application of animal waste is a common disposal method used in the United States and is a means for environmental entry of both antibiotics and genetic resistance determinants. Concerns for bacterial resistance gene selection and dissemination of resistance genes have prompted interest about the concentrations and biological activity of drug residues and break-down metabolites, and their fate and transport. Fecal bacteria can survive for weeks to months in the environment, depending on species and temperature, however, genetic elements can persist regardless of cell viability. Phylogenetic analyses indicate antibiotic resistance genes have evolved, although some genes have been maintained in bacteria before the modern antibiotic era. Quantitative measurements of drug residues and levels of resistance genes are needed, in addition to understanding the environmental mechanisms of genetic selection, gene acquisition, and the spatiotemporal dynamics of these resistance genes and their bacterial hosts. This review article discusses an accumulation of findings that address aspects of the fate, transport, and persistence of antibiotics and antibiotic resistance genes in natural environments, with emphasis on mechanisms pertaining to soil environments following land application of animal waste effluent.

Influence of type and neutralisation capacity of antacids on dissolution rate of ciprofloxacin and moxifloxacin from tablets

Dissolution rate of two fluoroquinolone antibiotics (ciprofloxacin and moxifloxacin) was analysed in presence/absence of three antacid formulations. Disintegration time and neutralisation capacity of antacid tablets were also checked. Variation in disintegration time indicated the importance of this parameter, and allowed evaluation of the influence of postponed antacid-fluoroquinolone contact. The results obtained in this study showed decreased dissolution rate of fluoroquinolone antibiotics from tablets in simultaneous presence of antacids, regardless of their type and neutralisation capacity.

Antimicrobial activities of pomegranate rind extracts: enhancement by addition of metal salts and vitamin C

BACKGROUND

Punica granatum L. or pomegranates, have been reported to have antimicrobial activity against a range of Gram positive and negative bacteria. Pomegranate formulations containing ferrous salts have enhanced although short-term, antibacteriophage activities which are rapidly diminished owing to instability of the ferrous combination. The aim of this study was to determine the antimicrobial activities of combinations of pomegranate rind extracts (PRE) with a range of metals salts with the added stabiliser vitamin C.

METHODS

PRE solutions, prepared by blending rind sections with distilled water prior to sterilisation by autoclaving or filtration, were screened with a disc diffusion assay using penicillin G as a control. Suspension assays were used to determine the antimicrobial activities of PRE alone and in combination with salts of the following metals; Fe (II), Cu (II), Mn (II) or Zn (II), and vitamin C, against a panel of microbes following exposure for 30 mins. The test organisms included Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Proteus mirabilis.

RESULTS

The screening assay demonstrated that PRE exhibited activity against the Gram positive organisms at 24 h with no observable effect on any of the Gram negative bacteria. However, after 12 h, zones of inhibition were only observed for Ps. aeruginosa. In contrast, using the suspension assay, addition of Cu (II) salts to PRE solutions extended the activities resulting in no detectable growth being observed for the PRE/Cu (II) combination against E. coli, Ps. aeruginosa and P. mirabilis. Minimal antimicrobial activity was observed following incubation with Fe (II), Mn (II) or Zn (II) salts alone or in combination with PRE against any of the organisms in the test panel. The addition of vitamin C markedly enhanced the activities of both PRE/Fe (II) and PRE/Cu (II) combinations against S. aureus.

CONCLUSION

This is the first report demonstrating the enhanced efficacy of PRE/metal salt combinations in the presence of the stabilising agent vitamin C, to which all isolates were sensitive with the exception of B. subtilis. This study has validated the exploration of PRE along with additives such as metal salts and vitamin C as novel antimicrobial combinations.

In-vitroantibacterial and cytotoxic activity of cobalt (ii), copper (ii), nickel (ii) and zinc (ii) complexes of the antibiotic drug cephalothin (Keflin)

Keflin (kefl) interacts with Co(II), Cu(II), Ni(II) and Zn(II) metal ions leading to complexes of the type M(kefl)2Cl2 and M(kefl)Cl2, which have been characterized by physicochemical and spectroscopic methods. Magnetic moment, IR, electronic spectral and elemental analyses data suggest that keflin behaves tridentately forming octahedral or trigonal bipyramidal complexes with the metal ions mentioned above. The new compounds have been screened in-vitro for antibacterial and cytotoxic activity against Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhi, Shigella dysentriae, Bacillus cereus, Corynebacterium diphtheriae, Staphylococcus aureus and Streptococcus pyogenes bacterial strains. Compounds, 4 and 8 showed promising activity (90%) against seven, compound 6 showed significant activity (52%) against four and, compounds 1 and 5 showed activity (40%) against three test bacterial strains at concentration of 10 microM.

Antibacterial cobalt (II), copper (II), nickel (II) and zinc (II) complexes of mercaptothiadiazole—derived furanyl, thienyl, pyrrolyl, salicylyl and pyridinyl Schiff bases

A series of Co (II), Cu (II), Ni (II) and Zn (II) complexes of mercaptothiadiazole-derived furanyl, thienyl, pyrrorlyl, salicylyl and pyridinyl Schiff bases were synthesized, characterized and screened for their in vitro antibacterial activity against four Gram-negative, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi and Shigella fexneri, and two Gram-positive; Bacillus subtilis and Staphylococcus aureous bacterial strains. The results of these studies show the metal complexes to be more antibacterial as compared to the prepared un-complexed Schiff bases.

In vitroantibacterial, antifungal & cytotoxic activity of some isonicotinoylhydrazide Schiff's bases and their cobalt (II), copper (II), nickel (II) and zinc (II) complexes

Isonicotinoylhydrazide Schiff's bases formed by the reaction of substituted and unsubstituted furyl-2-carboxaldehyde and thiophene-2-carboxaldehyde with isoniazid and, their Co (II), Cu (II), Ni (II) and Zn (II) complexes have been synthesized, characterized and screened for their in vitro antibacterial activity against Mycobacterium tuberculosis, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhi, Shigella dysenteriae, Bacillus cereus, Corynebacterium diphtheriae, Staphylococcus aureus and Streptococcus pyogenes bacterial strains and for in vitro antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glabrata. The results of these studies show the metal complexes to be more antibacterial and antifungal against one or more bacterial/fungal strains as compared to the uncomplexed compounds. The brine shrimp bioassay indicated Schiff's bases, L3 and L6 and, their Cu (II) and Ni (II) metal complexes to be cytotoxic against Artemia salina, while all other compounds were inactive (LD50 > 1000).

Effect of the anticoagulant ethylenediamine tetra-acetic acid (EDTA) on the estimation of pharmacokinetic parameters: A case study with tigecycline and ciprofloxacin

Tigecycline and ciprofloxacin were employed as the model compounds to study the effect of the anticoagulant ethylenediamine tetra-acetic acid (EDTA), which is used during plasma sample preparations, on the determination of pharmacokinetic parameters. The pharmacokinetic parameters were determined in rats following intravenous infusion with blood samples collected in serum separators, with either EDTA- or heparin-coated tubes. The blood-to-plasma (B:P) partition ratio and plasma protein binding were determined in vitro in rat or human blood collected in either EDTA- or heparin-coated tubes. Drug concentrations were quantified by liquid chromatography coupled with tandem mass spectrometry detection (LC-MS/MS) analysis. In tigecycline-treated rats drug concentrations were twofold lower in EDTA plasma, leading to a twofold lower area under plasma concentration-time curve (AUC) and twofold higher plasma clearance values as compared with those obtained from heparin plasma. No differences were noted in the pharmacokinetic parameters obtained from heparin-treated plasma versus serum. The B:P partition ratio and unbound fraction for tigecycline were significantly higher in EDTA-treated blood. When normalized to the B:P partition ratios, the tigecycline blood clearance values were identical between samples collected in EDTA- or heparin-coated tubes. Similar but smaller differences were observed for ciprofloxacin. It was concluded that EDTA might compete with tigecycline and ciprofloxacin for chelating metal ions and thus affect drug partition between blood and plasma compartments, leading to inaccurate measurement of pharmacokinetic parameters in plasma.

Mithramycin A inhibits DNA methyltransferase and metastasis potential of lung cancer cells

Abnormal CpG island hypermethylation of multiple tumor-suppressor genes (TSGs) can lead to the initiation and progression of human cancer. The cytosine of the CpG island on the promoter region is methylated by 5'-cytosine-methyltransferases (DNMTs). Pharmacologic inhibitors of CpG island methylation provide a rational approach to reactivate the TSGs in tumor cells and to restore the critical cellular pathways in cancer cells. Mithramycin A (MMA) is known to be a GC- and CG-rich DNA-binding agent. We sought to determine whether MMA could inhibit CpG island methylation and DNMT expression in lung cancer cells. We found that MMA reduced the CpG island methylation of antimetastasis TSGs, including SLIT2 and TIMP-3 genes, and was associated with the prevention of metastasis. When highly metastatic CL1-5 lung cancer cells were treated with low doses (10 nmol/l) of MMA for 14 days, they reexpressed mRNA levels for these genes. MMA also inhibited the invasion phenotypes of CL1-5 cells as indicated by its inhibition of cancer cell migration using wound-healing and transwell assays. Molecular docking of MMA onto the DNMT1 catalytic domain revealed that MMA might interact with the catalytic pocket of DNMT1. Western blots showed that DNMT1 protein levels were depleted after MMA. These data support the idea that MMA has demethylation and antimetastasis effects on lung cancer cells. This mechanism might be mediated by the interaction of MMA and DNMT1, leading to the depletion of the DNMT1 protein and the reversal of the metastasis phenotype in lung cancer cells.

Inhibition of carbonic anhydrase isozymes I, II and IX with benzenesulfonamides containing an organometallic moiety

A novel series of benzenesulfonamides that contain ferrocenyl or ruthenocenyl moieties were synthesized and investigated for their ability to inhibit the enzymatic activity of physiologically relevant carbonic anhydrase (CA) isozymes: hCA I, II and tumour-associated IX (h=human). This manuscript describes the regioselective synthesis of both the 1,4- and 1,5-disubstituted-1,2,3-triazole benzenesulfonamides from ethynylmetallocene substrates. This is the first report describing the covalent attachment of organometallic moieties to the arylsulfonamide (ArSO(2)NH(2)) CA recognition pharmacophore. At hCA I these metallocene derivatives were either nanomolar or low micromolar inhibitors, while against hCA II and IX inhibition in the range of 9.7-80nM and 10.3-85nM, respectively, was observed. The ruthenocenyl derivatives gave superior CA inhibition compared to the ferrocenyl compounds across all three CA isozymes. These compounds constitute a new organometallic class of CA inhibitors with promising biological activity.

Elucidating Connectivity and Metal-Binding Structures of Unlabeled Paramagnetic Complexes by 13C and 1H Solid-State NMR under Fast Magic Angle Spinning

Characterizing paramagnetic complexes in solids is an essential step toward understanding their molecular functions. However, methodologies to characterize chemical and electronic structures of paramagnetic systems at the molecular level have been notably limited, particularly for noncrystalline solids. We present an approach to obtain connectivities of chemical groups and metal-binding structures for unlabeled paramagnetic complexes by 13C and 1H high-resolution solid-state NMR (SSNMR) using very fast magic angle spinning (VFMAS, spinning speed >or=20 kHz). It is experimentally shown for unlabeled Cu(II)(Ala-Thr) that 2D 13C/1H correlation SSNMR under VFMAS provides the connectivity of chemical groups and assignments for the characterization of unlabeled paramagnetic systems in solids. We demonstrate that on the basis of the assignments provided by the VFMAS approach multiple 13C-metal distances can be simultaneously elucidated by a combination of measurements of 13C anisotropic hyperfine shifts and 13C T1 relaxation due to hyperfine interactions for this peptide-Cu(II) complex. It is also shown that an analysis of 1H anisotropic hyperfine shifts allows for the determination of electron-spin states in Fe(III)-chloroprotoporphyin-IX in solid states.

Experimental electron density study of a complex between copper(II) and the antibacterial quinolone family member ciprofloxacin

An experimental charge density study of a 1 : 1 complex of Cu-cfx (cfx = ciprofloxacin), 1 [Cu(cfx)(H(2)O)(3)]SO4.2H(2)O, has been performed using single-crystal X-ray diffraction data collected at 100 K using conventional Mo Kalpha radiation. Metal-ligand (ML) bonds and hydrogen bonds (HBs) have been analysed using topological analysis of the electron density with the atoms in molecules (AIM) approach. The copper atom binds to two oxygen atoms in one end of the zwitterionic form of the cfx molecule, in addition to forming bonds with three water molecules, forming a square pyramidal coordination geometry. AIM decomposition of the experimental electron density establishes that the copper atom binds more strongly to the cfx molecule than to the water molecules, suggesting that the latter can be detached leaving behind a reactive, water-free Cu-cfx complex available for interaction with e.g. a macromolecular site. AIM analysis of the extensive hydrogen bond pattern reveals that the positively charged N-end of the zwitterionic cfx forms a relatively strong N-H-O hydrogen bond implying that this region of cfx may play an important role in the docking process in the active site. Visualisation and statistics of selected density derived properties on the molecular surface of the isolated cfx molecule vs its metal complexed counterpart points out regions of potential reactivity. The effect of the fluorine atom is to expand the negative region of the electrostatic potential, while the nitrogen end is heavily electropositive and willingly donates to--for molecular docking purposes--relatively strong hydrogen bonding. The Cu atom is highlighted as a potentially highly reactive site which is likely to interact strongly with any given negative ligand.

Metalloantibiotics: synthesis, characterization and in-vitro antibacterial studies on cobalt (II), copper (II), nickel (II) and zinc (II) complexes with cloxacillin

The synthesis and characterization of cloxacillin (clox) complexes with divalent metal ions [Co (II), Cu (II), Ni (II) and Zn (II)] is described. The nature of bonding of the chelated cloxacillin and the structures of the metal complexes have been elucidated on the basis of their physical and spectroscopic data. In all the complexes, the cloxacillin acts as a uninegatively charged bidentate ligand with coordination involving the carboxylate-O and endocyclic-N of the beta-lactam ring. The new compounds have been screened for in-vitro antibacterial activity against Escherichia coli (a), Klebsiella pneumonae (b), Proteus mirabilis (c), Pseudomonas aeruginosa (d), Salmonella typhi (e), Shigella dysentriae (f), Bacillus cereus (g), Corynebacterium diphtheriae (h), Staphylococcus aureus (j) and Streptococcus pyogenes (k) bacterial strains. The brine shrimp bioassay was also carried out to study their in-vitro cytotoxic properties. All compounds, respectively, showed a promising activity (90%) against five bacterial species at 10 microg/ml concentration and a significant activity (52%) against the same test bacteria at 25 microg/ml concentration.

Metal complexes of retinoid derivatives with antiproliferative activity: synthesis, characterization and DNA interaction studies

9-cis-Retinal thiosemicarbazone and its Co(III), Ni(II) and Cu(II) complexes are synthesized and characterized. Central Co(III) atom is in an octahedral environment while Ni(II) and Cu(II) atoms are in a square planar environment. DNA binding constants and spectroscopic data show an intercalative behavior for the nickel complex; an external binding mode is envisaged for the ligand and its copper complex. No DNA interaction can be hypothesized for the cobalt complex. The free ligand and its Ni(II) and Cu(II) complexes have a good lipophilic degree for an efficient uptake by the cells. The metal complexes exhibit a proliferation inhibition action against cell line U937 at micromolar concentration. Cu(II) complex also induces apoptosis, while Ni(II) complex has a strong interaction with CT-DNA.

X-Ray crystallographic, NMR and antimicrobial activity studies of magnesium complexes of fluoroquinolones - racemic ofloxacin and its S-form, levofloxacin

The magnesium complexes of racemic ofloxacin (oflo) and its pure S-form levofloxacin (S-oflo) have been studied by X-ray crystallography and NMR spectroscopy. Two compounds, [Mg(R-oflo)(S-oflo)(H(2)O)(2)].2H(2)O (1) and [Mg(S-oflo)(2)(H(2)O)(2)].2H(2)O (2), respectively, have been prepared by hydrothermal reactions and their crystal structures have been determined. In both structures the anionic fluoroquinolone ligands are coordinated through the keto and carboxylate oxygens forming 1:2 Mg:oflo complexes. The two structures are practically identical except for the orientation of one of the oxazine methyl groups at the chiral center of 2 which was found in equatorial position, the other oxazine methyl groups in 1 and 2 being axial. This difference affects the stacking pattern of quinolone molecules in the cell. (1)H NMR chemical shift data and Mn(II) paramagnetic line broadening measurements on the free ofloxacin suggest that the coordination of the ligands in solution involves the keto and carboxylate oxygens. However, it is not possible to decide whether the complexes in aqueous solution have 1:1 or 1:2 stoichiometry. The methylated piperazine nitrogen does not interact with the metal ion. Magnesium-quinolone interaction is discussed in relation to the biological activity of quinolones. The antimicrobial activity of the complexes against various microorganisms was tested and it was established that their activity is similar to that of free quinolone drugs.

Can metals defend plants against biotic stress?

Farmers have used metal compounds in phytosanitary treatments for more than a century; however, it has recently been suggested that plants absorb high concentrations of metals from the substrate as a self-defense mechanism against pathogens and herbivores. This metal defense hypothesis is among the most attractive proposals for the 'reason to be' of metal hyperaccumulator species. On a molecular basis, metal defense against biotic stress seems to imply common and/or complementary pathways of signal perception, signal transduction and metabolism. This does not imply a broad band of co-resistance to different stress types but reflects a continuous cross talk during the coevolution of plants, pathogens and herbivores competing in an environment where efficient metal ion acquisition and ion homeostasis are essential for survival.