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PubMed2001

Chemiluminescent flow-through sensor for 1,10-phenanthroline based on the combination of molecular imprinting and chemiluminescence.

A functional polymer for the catalysis of the chemiluminescent reaction and molecular recognition ability of 1,10-phenanthroline was prepared based on the molecular imprinting method. The structural and catalytic roles of transition metal ion interactions were applied in the material design. A ternary complex, 4-vinylpyridine-Cu(II)-1,10-phenanthroline (2:1:1), was synthesized and used as a functional monomer. The ligand 1,10-phenanthroline in the ternary complex was the template used to form the molecularly imprinted polymer. Another monomer, styrene, and the cross-linking reagent divinylbenzene were copolymerized with the ternary complex. The polymer containing the ternary complex is an efficient catalyst for the decomposition of hydrogen peroxide. During the hydrogen peroxide decomposition, superoxide radical ion is formed, which reacts with 1,10-phenanthroline and gives a chemiluminescent emission. The 1,10-phenanthroline was destroyed during the chemiluminescent reaction, leaving a cavity and copper binding sites for another 1,10-phenanthroline molecule. The prepared polymer particles were packed into a glass tube and developed as a molecular recognition chemiluminescent flow-through sensor for 1,10-phenanthroline. The sensitivity and selectivity of the sensor were tested.

Journal Article↗
PubMed1999

Induction of drug metabolizing enzymes by 1,7-phenanthroline and oltipraz in mice is unrelated to Ah-responsiveness.

The protective effect of several classes of compounds against the toxic and neoplastic effects of xenobiotics has been attributed to the induction of noncytochrome P450 (P450) drug metabolizing enzymes. Glutathione S-transferases (GST), NAD(P)H: quinone oxidoreductase (QOR), and UDP-glucuronosyltransferases (UGT) play a prominent role in detoxification and can be induced by oltipraz and other N-heterocyclic compounds in rats. In contrast to the induction of these enzymes by aryl hydrocarbon (Ah)-receptor agonists, induction by oltipraz and 1,7-phenanthroline is not accompanied by CYP1A induction. This study investigated the induction of drug metabolizing enzymes following administration of oltipraz and 1,7-phenanthroline in four mouse strains (C57B6A-J, Frings x C57B6J, Frings, CF-1) exhibiting varying degrees of responsiveness to an Ah-receptor agonist. The relative Ah responsiveness was determined in all strains by the induction of hepatic Cypla after three daily doses of 3-methylcholanthrene (20 mg/kg). After treatment with 1,7-phenanthroline and oltipraz (150 mg/kg i.g.) daily for 3 days, all strains showed similar induction of GST and QOR activities for each inducer. Both compounds were equally effective in elevating GST activity, but 1,7-phenanthroline was more effective than oltipraz in elevating QOR activity. In addition to GST and QOR changes, 1,7-phenanthroline significantly elevated UGT (1-naphthol) activity in the Frings strain. Neither compound produced significant changes in Cypla parameters. The independence of 1,7-phenanthroline and oltipraz induction of GST and QOR from Cypla-responsiveness is in line with the concept that N-heterocycle-containing inducers act by mechanisms other than an Ah-receptor-dependent pathway in which the P450 response has been masked or prevented.

Animals↗
PubMed2004

DNA binding and cleavage properties of certain tetrammine ruthenium(II) complexes of modified 1,10-phenanthrolines--effect of hydrogen-bonding on DNA-binding affinity.

A series of ruthenium(II) mixed ligand complexes of the type [Ru(NH(3))(4)(L)](2+), where L=imidazo[4,5-f][1,10]phenanthroline (ip), 2-phenylimidazo[4,5-f][1,10]phenanthroline (pip), 2-(2-hydroxyphenyl)imidazo[4,5-f][1,10]phenanthroline (hpip), 4,7-diphenyl-1,10-phenanthroline (dip), naphtha[2,3-a]dipyrido[3,2-h:2',3'-f]phenazine-5,18-dione (qdppz), 5,18-dihydroxynaphtho[2,3-a]dipyrido[3,2-H:2',3'-f]phenazine (hqdppz), have been isolated and characterized. The interaction of these complexes with calf thymus DNA (CT DNA) has been explored by using absorption, emission, and circular dichroic spectral methods, thermal denaturation studies and viscometry. All these studies suggest the involvement of the modified phenanthroline 'face' rather than the ammonia 'face' of the complexes in DNA binding. An intercalative mode of DNA binding, which involves the insertion of the modified phenanthroline ligands in between the base pairs, is suggested. The results from absorption spectral titration and circular dichroism (CD), thermal denaturation and viscosity experiments indicate that the qdppz and hqdppz complexes (K(b) approximately 10(6) and Delta T(m)=11-13 degrees C) bind more avidly than the ip, pip and hpip complexes (K(b) approximately 10(5), Delta T(m)=6-8 degrees C). Intramolecular hydrogen bonding in the hpip and hqdppz complexes increases the surface area of the intercalating diimines and enhances the DNA binding affinity substantially. The ammonia co-ligands of the complexes are possibly involved in hydrogen bonding with the intrastrand nucleobases to favour intercalation of the extended aromatic ligands. Circular dichroism spectral studies reveal that all the complexes effect certain structural changes on DNA duplex; [Ru(NH(3))(4)(ip)](2+) induces a B to A transition while [Ru(NH(3))(4)(qdppz)](2+) a B to Psi conformational change on CT DNA. Cleavage efficiency of the complexes were determined using pBR322 supercoiled plasmid DNA. All the complexes, except hqdppz complex, promote the cleavage of supercoiled plasmid (form I) to relaxed circular form (form II).

Animals↗
PubMed2004

DNA binding and biological activity of some platinum(II) intercalating compounds containing methyl-substituted 1,10-phenanthrolines.

This study documents the first detailed investigation into the relationship between molecular structure and biological activity of platinum(II) complexes containing methylated derivatives of 1,10-phenanthroline (phen). A series of square planar platinum(II) compounds incorporating methylated derivatives of phen, 4-methyl-1,10-phenanthroline (4-Mephen), 5-methyl-1,10-phenanthroline (5-Mephen), 4,7-dimethyl-1,10-phenanthroline (4,7-Me2phen), 5,6-dimethyl-1,10-phenanthroline (5,6-Me2phen) and 3,4,7,8-tetramethyl-1,10-phenanthroline (3,4,7,8-Me4phen) were synthesised and the relationship between their structure and biological activity investigated. The biological activity of these compounds was quantified using the in vitro cytotoxicity assay against the L1210 Murine leukaemia cell line. Large variation in cytotoxicities with different methylation was observed. The 5- and 5,6-methylated derivatives of phen displayed a greater biological activity, with IC50 values of 2.8 +/- 0.8 microM and 1.5 +/- 0.3 microM respectively, compared with the phen compound, with an IC50 value of 9.7 +/- 0.3 microM, while all the others were inactive with IC50 values over 50 microM. Binding constants were determined using circular dichroism spectroscopy (CD) and induced circular dichroism (ICD). ICD was used to highlight any differences in the spectra. Viscometry studies and linear dichroism (LD) experiments indicate that the platinum(II) complexes intercalate although for [Pt(en)(4-Mephen)]Cl2 and [Pt(en)(4,7-Me2phen)]Cl2 this mode of binding appears to be concentration dependent. The binding of the platinum(II) complexes to the oligonucleotide d(GTCGAC)2 was studied using two-dimensional 1H NMR spectroscopy. The addition of each metal complex to the hexamer d(GTCGAC)2 produced upfield shifts of the metal complex resonances, characteristic of intercalation. Through the observation of NOE cross-peaks, two-dimensional NMR studies provided insight into the site and groove preferences of these compounds when binding to DNA.

Animals↗
PubMed1995

Inhibition of human immunodeficiency virus type 1 integrase by a hydrophobic cation: the phenanthroline-cuprous complex.

The human immunodeficiency virus type 1 integrase (HIV-1 integrase) is required for integration of a double-stranded DNA copy of the viral RNA genome into a host chromosome and for HIV replication. We have examined the effects of 2:1 1,10-phenanthroline-cuprous complexes on purified HIV-1 integrase. Although the uncomplexed phenanthrolines are not active below 100 microM, four of the cuprous complexes (neocuproine, 4-phenyl neocuproine, 2,3,4,7,8,9-hexamethyl phenanthroline, and 2,3,4,7,8-pentamethyl phenanthroline) have a 50% inhibitory concentration (IC50) for integration ranging between 1 and 10 microM. Disintegration is also inhibited by these phenanthroline-cuprous complexes at slightly higher concentrations (between 10 and 40 microM). Dialysis experiments showed that the inhibition is reversible and kinetic analyses revealed that the mode of inhibition by these cuprous complexes appears to be noncompetitive with respect to the substrate DNA. Consistent with these findings, binding assays demonstrate that, although these complexes can inhibit binding to DNA at high concentrations, they do not inhibit binding of integrase to the DNA substrate at their IC50 values. Because these complexes do not bind to B-DNA below 50 microM, inhibition via binding to a specific region on the enzyme was examined. Using deletion mutants of integrase, it was determined that neither the amino-terminal (zinc finger) nor the carboxy-terminal (DNA-binding) integrase domain is required for inhibition by the phenanthroline-cuprous complexes. Therefore, inhibition via binding to the enzyme catalytic core or to the interface between the enzyme and a noncanonical DNA structure generated during the enzymatic reaction is the probable mechanism. These results suggest the utility of neocuproine-cuprous complexes in developing inhibitors of HIV-1 integrase as well as probes for drug-binding sites and enzymatic reaction mechanism.

Base Sequence↗
PubMed1996

Inhibition by 1,10-phenanthroline of the breakdown of peptides by rumen bacteria and protozoa.

The rate of peptide breakdown in the rumen frequently exceeds the rate at which the amino acids released can be used for microbial growth. The final step in this often wasteful process involves the cleavage of dipeptides. The main rumen bacterial species with high dipeptidase activity, Prevotella ruminicola, Fibrobacter succinogenes, Lachnospira multipara and Megasphaera elsdenii, had activities which were inhibited > 95% by 1,10-phenanthroline, a chelator of divalent metal ions and metalloprotease inhibitor. Dipeptidase activity in digesta taken from the rumen of sheep decreased by 33% in the presence of 1,10-phenanthroline, while mixed bacteria from the same samples were inhibited by 80% and the activity of mixed protozoa decreased by only 15%. Thus a substantial amount of dipeptide breakdown appears to be due to ciliate protozoa in the mixed population. Extensive washing of the protozoa increased the sensitivity of protozoal dipeptidase activity to 1,10-phenanthroline, suggesting that protozoa too have a metallo-dipeptidase activity but that it is normally protected from inhibition by 1,10-phenanthroline. Breakdown of the pentapeptide, Ala5, was also inhibited 27% by 1,10-phenanthroline in the mixed population, and when Trypticase, a pancreatic casein hydrolysate containing a mixture of oligopeptides, dipeptides and amino acids, was incubated with rumen fluid, the production of ammonia and free amino groups was inhibited 71% by 1,10-phenanthroline. It was concluded that metal ion chelation inhibits oligopeptidase and dipeptidase activities of rumen micro-organisms and may be a means of controlling ammonia production from peptides in the rumen.

Ammonia↗
PubMed1988

The binding of 1,10-phenanthroline to specifically active-site cobalt(II)-substituted horse-liver alcohol dehydrogenase. A probe for the open-enzyme conformation.

We have studied the binding of 1,10-phenanthroline to specifically active-site cobalt(II)-substituted horse-liver alcohol dehydrogenase [Co(II)-LADH]. The dissociation constant is a factor of 6500 smaller than in the native enzyme. Spectral evidence is given which shows that 1,10-phenanthroline does not remove the catalytic Co(II) ion and that binding of 1,10-phenanthroline renders the catalytic metal ion pentacoordinate. The maximum limiting rate constant for the association of 1,10-phenanthroline to Co(II)-LADH is about 60 s-1. This is about a third of the value (169 s-1) determined for native horse-liver alcohol dehydrogenase, Zn(II)LADH [Frolich et al. (1978) Arch. Biochem. Biophys. 189, 471-480]. For cadmium(II)-substituted horse-liver alcohol dehydrogenase, [Cd(II)LADH] the maximum limiting rate constant for association of 1,10-phenanthroline increased to 590 s-1. These findings demonstrate that the rate-limiting step is strongly dependent on the chemical nature of the catalytic metal ion and its immediate environment. 1,10-Phenanthroline is shown to bind to the Co(II)-LADH.NAD+ complex in the open conformation. The maximum limiting rate constant remains unchanged in the presence of NAD+. The data have been used to derive a kinetic scheme for the formation of ternary complexes including NAD+ that involves a slow intermediary step.

Alcohol Dehydrogenase↗
PubMed1988

Conformational stability of ferrocytochrome c. Electrostatic aspects of the oxidation by tris(1,10-phenanthroline)cobalt(III) at low ionic strength.

At ionic strengths below 0.1 M the oxidation of horse ferrocytochrome c by tris(1,10-phenanthroline)cobalt (III) and tris(2,2'-bipyridine)cobalt(III) proceeds by a pathway which is independent of the transition metal complex concentration. Formation of an activated form of the protein appears to be rate limiting. The rate of oxidation decreases as the ionic strength increases. This dependence of the reaction rate on inert electrolyte concentration indicates that electrostatic association of anions under physiological ionic strength confers stability to the protein. The activated form of the protein, which reacts at least 10(4) times as fast as the predominant form, is thought to be a conformation of the reduced protein with an open heme crevice. Binding of the open form of ferrocytochrome c with the redox-inactive cationic transition metal complexes hexamminecobalt(III) and tris(1,10-phenanthroline)chromium(III) inhibits the oxidation by tris(1,10-phenanthroline)cobalt(III). Reactions of tris(1,10-phenanthroline)cobalt(III) with 4-carboxy-2,5-dinitrophenyllysine 13 and 72 ferrocytochromes c show no dependence on ionic strength. NMR studies at pH 7 demonstrate that ferricytochrome c is partly (15%) in the open conformation at low ionic strength. Furthermore, the interaction of redox-inert tris (1,10-phenanthroline)chromium(III) with ferricytochrome c under conditions identical to those of the kinetic studies demonstrates that the transition metal complex binds only to the open form of the protein. Titration with increasing amounts of tris(1,10-phenanthroline) chromium(III) shows changes in the NMR spectrum that are inconsistent with a single binding site.

Algorithms↗
PubMed1988

[Artificial nucleases: specific cleavage of the double helix of DNA by oligonucleotides linked to copper-phenanthroline complex].

A homopyrimidine oligonucleotide d(TTTCCTCCTCT) was covalently linked to 1,10-phenanthroline via a 5'-thiophosphate group. In the presence of copper ions and a reducing agent the copper-phenanthroline complex induced cleavage reactions in duplex DNA. The oligonucleotide binds to the major groove of DNA at a homopurine.homopyrimidine sequence, forming a local triple helix. It is oriented parallel to the homopurine strand. Watson-Crick A.T and G.C base pairs are recognized via Hoogsteen-type hydrogen bonding by thymine and protonated cytosine, respectively. The cleavage patterns on opposite strands of duplex DNA at the homopurine.homopyrimidine sequence are asymmetric. They are shifted toward the 3'-side indicating that cleavage takes place from the minor groove even though the oligonucleotide is bound to the major groove. It is therefore suggested that the phenanthroline ring attached to the oligonucleotide intercalates into DNA at the junction between the triple and the double helix and that the copper complex forms in the minor groove where radical reactions leading to strand cleavage occur. The homopyrimidine oligodeoxynucleotide d(TTTCCTCCTCT) tethered to phenanthroline binds to a single site on SV 40 DNA. It cleaves circular and linear SV 40 DNA at this single binding site. Cleavage requires both copper ions and a reducing agent. The unsubstituted oligonucleotide competes with the oligonucleotide-phenanthroline conjugate and prevents site-specific cleavage. These results demonstrate that oligonucleotide-phenanthroline conjugates can be used to induce sequence-specific cleavage of duplex DNA. Such artificial endonucleases could be used, among other things, to map genes on long DNA fragments, to induce site-specific mutations or to block gene expression at the transcriptional level.

Base Composition↗
PubMed1994

Lethal interaction between hydrogen peroxide and o-phenanthroline in Escherichia coli.

The iron chelator o-phenanthroline enhances the lethal effect of H2O2 about four hundred times in Escherichia coli when both substances are added simultaneously to the culture medium. If o-phenanthroline is added for increasing periods of time prior to the addition of H2O2, there is a shift from this lethal interaction to protection by the chelator about seven hundred times. It is known that the Fe(2+)-o-phenanthroline(I) and Fe(2+)-o-phenanthroline(II) complexes are formed quickly whereas the final and more stable Fe(2+)-o-phenanthroline(III) complex is formed slowly. Moreover, the mono and bis complexes react with H2O2 to produce OH., whereas the tris complex is stable towards H2O2. Therefore, the lethal effect could be explained by the kinetics of reaction of o-phenanthroline with intracellular Fe2+, i.e., the mono and bis complexes are more reactive than intracellular Fe2+.

2,2'-Dipyridyl↗
PubMed2005

A spectroscopic and computational study on the effects of methyl and phenyl substituted phenanthroline ligands on the electronic structure of Re(I) tricarbonyl complexes containing 2,6-dimethylphenylisocyanide.

[Re(CO)3(CNx)(L)]+, where CNx = 2,6-dimethylphenylisocyanide, forms complexes with L = 1,10-phenanthroline (1), 4-methyl-1,10-phenanthroline (2), 4,7-dimethyl-1,10-phenanthroline (3), 3,4,7,8-tetramethyl-1,10-phenanthroline (4), 2,9-dimethyl-1,10-phenanthroline (5) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (6). The metal-ligand-to-ligand charge transfer transition (MLLCT) absorption bands follow the series: (27800 cm(-1)) > 1, 2, 4 and 5(27500 cm(-1)) > 6 (26600 cm(-1)). Density functional theory (DFT) geometry optimizations reveal elongated Re-N (L) distances of 2.28 and 2.27 A for 5 and 6, respectively, compared to 2.23 A for 1-4. The reversible reduction potentials (E(1/2(red))) of 1-4 are linearly dependent on the B3LYP calculated LUMO energies. Time-dependent (TD) DFT and conductor-like polarizable continuum model (CPCM) calculated singlet excited states deviate by 700 cm(-1) or less from the experimental absorption maxima and aid in the spectral assignments. The (3)MLLCT emitting state energies are within 900 cm(-1) of the experimental 77 K emission energies for 1-6. The 77 K emission energies, E(1/2(red)), and the room temperature emission quantum yields (phi(LUMO)(em)) decrease in the order 1 >2 >3 >4 whereas E(LUMO) and the room temperature emission energies follow the opposite trend. The emission lifetimes (tau(em)) decrease in the order 3 > 4 >2 >1 >5 with 3 having the highest emission lifetime values of 26.9 micros at room temperature and 384 micros at 77 K and complex 5 having the lowest emission lifetimes of 4.6 micros at room temperature and 61 micros and 77 K.

Journal Article↗
PubMed1998

Palladium(II) complexes with N,N'-dialkyl-1,10-phenanthroline-2,9-dimathanamine: synthesis, characterization and cytotoxic activity.

Five new tetradentate ligands and their corresponding palladium complexes, [Pd(L)]Cl2 (L = N,N'-dimethyl-1,10-phenanthroline-2,9-dimathanamine, N,N'-diethyl-1,10-phenanthroline-2,9-dimathanamine, N,N'-dipropyl-1,10-phenanthroline-2,9-dimathanamine, N,N'-ditert-butyl-1,10-phenanthroline-2,9-dimathanamine, N,N'-dicyclohexyl-1,10-phenanthroline-2,9-dimathanamine) have been synthesized. The ligands and their complexes have been characterized by elemental analysis, IR, and 1H NMR. The complexes have been assayed for antitumor activity in vitro against the mouse leukemia L1210 and the mouse liver carcinoma Bel7402 cell lines. The results showed that the activities of these complexes are significantly dependent on the nature of the alkyl groups on the coordinated amine moieties, and three of these palladium complexes showed lower ID50 values against the two cell lines than cisplatin.

Animals↗
PubMed1997

Effects of 1,10-phenanthroline and hydrogen peroxide in Escherichia coli: lethal interaction.

It has been observed that when Escherichia coli cells are treated simultaneously with phenanthroline and H2O2, there is a lethal interaction. In order to analyze the mechanism of this lethal interaction, wild-type and xthA mutant cells of E. coli were treated with 2.5 mM H2O2 and 1 mM phenanthroline. This treatment was preceded by treatments with different metal chelators (dipyridyl for Fe2+, desferal for Fe3+ and neocuproine for Cu2+) or conducted simultaneously to other treatments with chelators and radical scavengers (thiourea, ethanol and sodium benzoate). The lethal interaction was observed in both the E. coli wild-type strain and xthA mutant strain, which is deficient in the exonuclease III repair enzyme. Nevertheless, the mutant strain was much more sensitive than the wild-type one. Dipyridyl pretreatment protected the cells against the lethal interaction, while desferal pretreament was unable to do so. This suggests that the lethal interaction requires Fe2+ and not Fe3+ ions. Ethanol and sodium benzoate were incapable of protecting bacterial cells against the lethal interaction. Even a 20-min pretreatment with benzoate did not confer protection. On the other hand, thiourea protected the cells completely. Based on our results, we propose that the lethal interaction may be caused not only by the reaction kinetics of phenanthroline and Fe, but also by the ability of phenanthroline to intercalate in DNA. After forming the mono and bis complexes, phenanthroline would serve as a shuttle and take the Fe2+ ions to the DNA. So, the Fenton reaction would take its course with the consequent generation of OH. radicals near DNA. This proximity to the DNA would protect the OH. radicals against the scavengers' action, thus optimizing the Fenton reaction.

2,2'-Dipyridyl↗
PubMed2002

Phenanthroline complexes bearing fused dipyrrolylquinoxaline anion recognition sites: efficient fluoride anion receptors.

Novel anion recognition host molecules, tris-1,10-phenanthroline cobalt(III) and bis-2,2'-bipyridine mono-1,10-phenanthroline ruthenium(II) complexes bearing fused dipyrrolylquinoxaline moieties have been synthesized. As determined by UV-vis spectroscopic and electrochemical studies, these metal complexes bind fluoride with high affinity in polar media both in absolute terms and relative to the metal-free phenanthroline dipyrrolylquinozaline precursor from which they are derived (fluoride is bound to the tris-1,10-phenanthroline cobalt(III) dipyrrolylquinoxaline system with a 1:1 binding constant of 54 000 M-1 in DMSO). The large observed binding constants are ascribed to two factors, (i) the presence of a phenanthroline-coordinated cationic charge that decreases the electron density on the pyrrole NH protons and (ii) pure electrostatic effects.

Anions↗
PubMed1992

Kinetics of the course of inactivation of aminoacylase by 1,10-phenanthroline.

The kinetic theory of the substrate reaction during modification of enzyme activity previously described [Tsou (1988) Adv. Enzymol. Relat. Areas Mol. Biol. 61, 381-436] has been applied to a study on the kinetics of the course of inactivation of aminoacylase by 1,10-phenanthroline. Upon dilution of the enzyme that had been incubated with 1,10-phenanthroline into the reaction mixture, the activity of the inhibited enzyme gradually increased, indicating dissociation of a reversible enzyme--1,10-phenanthroline complex. The kinetics of the substrate reaction with different concentrations of the substrate chloroacetyl-L-alanine and the inactivator suggest a complexing mechanism for inactivation by, and substrate competition with, 1,10-phenanthroline at the active site. The inactivation kinetics are single phasic, showing that the initial formation of an enzyme-Zn(2+)-1,10-phenanthroline complex is a relatively rapid reaction, followed by a slow inactivation step that probably involves a conformational change of the enzyme. The presence of Zn2+ apparently stabilizes an active-site conformation required for enzyme activity.

Amidohydrolases↗
PubMed1994

The zinc chelator 1,10-phenanthroline enhances the stimulatory effects of protein kinase C activators and staurosporine, but not sphingosine and H2O2, on phospholipase D activity in NIH 3T3 fibroblasts.

Protein kinase C (PKC), an enzyme which is believed to mediate the stimulatory effects of the PKC activator phorbol 12-myristate 13-acetate (PMA) on phospholipase D (PLD) activity, has a zinc-dependent structure required for phorbol ester binding. Accordingly, zinc or zinc chelators would be expected to promote or inhibit, respectively, the stimulatory effects of PMA on PLD-mediated phospholipid hydrolysis. Instead, treatment of [14C]choline- and [14C]ethanolamine-labelled NIH 3T3 fibroblasts with the high-affinity zinc chelator 1,10-phenanthroline (0.2-1 mM) for 20-30 min was found to enhance the stimulatory effects of PMA on PLD-mediated hydrolysis of phosphatidylcholine and phosphatidylethanolamine. In [14C]palmitic acid-labelled fibroblasts, in the presence of ethanol, phenanthroline also enhanced the stimulatory effect of PMA on the synthesis of phosphatidylethanol, a marker of PLD activity. Addition of zinc (250 microM) to phenanthroline-treated fibroblasts reversed the stimulatory effects of the chelator. The potentiating effects of phenanthroline were also partially reversed by cadmium, whereas iron, lead, copper, magnesium and calcium were without effects. Of the other activators of PLD tested, phenanthroline also enhanced the stimulatory effects of platelet-derived growth factor and staurosporine, but not that of sphingosine and H2O2, on the hydrolysis of both phospholipids. These results suggest that regulation of PLD by PKC activators and staurosporine involves a common intermediate step, which is inhibited by a chelatable cellular pool of zinc.

3T3 Cells↗
PubMed1989

Sequence-specific recognition and cleavage of duplex DNA via triple-helix formation by oligonucleotides covalently linked to a phenanthroline-copper chelate.

Homopyrimidine oligodeoxynucleotides recognize the major groove of the DNA double helix at homopurine.homopyrimidine sequences by forming local triple helices. Phenanthroline was covalently attached to the 5' end of an 11-mer homopyrimidine oligonucleotide of sequence d(TTTCCTCCTCT). Simian virus 40 DNA, which contains a single target site for this oligonucleotide, was used as a substrate for the phenanthroline-oligonucleotide conjugate. In the presence of copper ions and a reducing agent, a single specific double-strand cleavage site was observed at 20 degrees C by agarose gel electrophoresis. The efficiency of double-strand cleavage was greater than 70% at 20 degrees C and pH 7.4. Secondary cleavage sites were observed when binding of the oligonucleotide to mismatched sequences was allowed to take place at low temperature. The exact location of the cleavage sites was determined by polyacrylamide gel electrophoresis of denatured fragments by using both simian virus 40 DNA and a synthetic DNA fragment containing the target sequence. The asymmetric distribution of the cleavage sites on the two strands revealed that the cleavage reaction took place in the minor groove even though the phenanthroline linker was located in the major groove. Linkers of different lengths were used to tether phenanthroline to the oligonucleotide and their relative efficacies of DNA cleavage were compared. Based on these comparative studies and on model building, it is proposed that the phenanthroline ring carried by the oligonucleotide intercalates from the major groove and that copper chelation locks the complex in place from within the minor groove where the cleavage reaction occurs.

Base Sequence↗
PubMed1993

Sequence-specific scission of DNA by the chemical nuclease activity of 1,10-phenanthroline-copper(I) targeted by RNA.

RNAs modified with the chemical nuclease 1,10-phenanthroline-copper(I) can achieve the sequence-specific scission of single- and double-stranded DNA targets. The RNAs are prepared in vitro by using 5-(3-aminoallyl)-UTP as the sole source of UTP and can be readily modified with 1,10-phenanthroline by using N-succinimidyl 3-(2-pyridyl-dithio)propionate (SPDP) to cross-link the ligand to the aminoallyl moiety. Single-stranded DNAs are efficiently cleaved at multiple sites because 1,10-phenanthroline is incorporated at several uridines in the sequence. Sequence-specific double-stranded scission of duplex DNA can also be accomplished with 1,10-phenanthroline-derivatized RNA within R loops. These triple-stranded structures form in 70% formamide and involve the displacement of one strand of DNA by the RNA of identical sequence. R loop-directed scission is the first method for DNA scission applicable to any sequence. A unique application of R loop-targeted nucleolytic scission, which relies on its ability to cut DNA at any sequence, is the determination of the distance between two marker DNA sequences within a target. In this case, 1,10-phenanthroline-linked RNAs are prepared from the two distinct sequences and used to cut the DNA fragment after R-loop formation. The size of the fragment liberated by these methods is a direct measure in base pairs of the distance between the two DNA sequences. For example, the distance separating two chicken delta crystallin (delta 1 and delta 2) genes has been confirmed as 24 kilobases by this method.

Animals↗