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PubMed2003

A liftoff technique for molecular nanopatterning.

For quantum-dot cellular automata molecular electronic devices, one of the fundamental tasks is to arrange the molecules on a surface in a controlled manner. In this report, we discuss a molecular lift off technique to form nanopatterns toward the development of molecular circuits. In our molecular lift off technique, we use electron beam lithography to form nano-trenches on a polymethylmethacrylate (PMMA) film on a SiO2 wafer. This wafer is soaked in a Creutz-Taube ion [(NH3)5Ru(pyrazine)Ru(NH3)5](o-toluenesulfonate)5 (CT5) aqueous solution. After residual PMMA removal, atomic force microscopy is used to investigate the resulting surface. Thirty-five nanometer CT5 lines are demonstrated on a SiO2 surface. Compared with other molecular nanopatterning techniques, ours is both economical and capable of high-resolution.

Adsorption↗

PubMed2001

Discriminative stimulus properties of indorenate, a 5-HT1A, 5-HT1B and 5-HT2C agonist: a study in rats.

Indorenate (INDO), initially described as an antihypertensive agent, also has some effects on behaviour, with anxiolytic and anorectic actions being reported. The aim of the present experiment was to examine the activity of INDO at the behavioural level at various serotonin (5-hydroxytryptamine, 5-HT) receptor sites by comparing its stimulus properties with those of other 5-HT receptor agonists and by examining its interactions with some 5-HT antagonists. Rats were trained to discriminate between 10.0 mg/kg INDO (administered intraperitoneally (90 min before the start of the session) from saline. A Fixed Ratio 10 (FR10) schedule of reinforcement was in effect in each drug condition. During generalization test sessions, the discrimination index (DI, responses to drug lever/responses to drug + saline lever) was calculated from the responses emitted before the first reinforcer of the session. DI was a function of the dose of INDO employed. Generalization to the discriminative stimulus properties of INDO was observed with the 5-HT1A receptor agonist 8-OH-DPAT (1.0 mg/kg produced 90% generalization) and the 5-HT(1B/2C) receptor agonist 1-(3-trifluoromethylphenyl) piperazine (TFMPP) (3.0 mg/kg produced up to 75% generalization). Yohimbine (5.6 mg/kg), buspirone (1.0 mg/kg), 6-chloro-2-(1-piperaziny)pyrazine (1.0 mg/kg) and m-chlorophenylpiperazine (mCPP) (1.0 mg/kg) induced a DI of 70%, 50% and 48% and 55%, respectively. In generalization tests, ritanserin (0.01-1.0 mg/kg) induced saline-like responding. NAN-190 (3.0 mg/kg), a 5-HT1A receptor antagonist, was able to reduce the DI of INDO to 50%. Although the 5-HT(2C/2A) receptor antagonists cinanserin (10.0 mg/kg) and metergoline (0.3 mg/kg) were able to reduce the stimulus properties of INDO to 60% and 30%, respectively, only ritanserin (1.0 mg/kg) reduced the stimulus properties of INDO to 25% with a clear dose-response relationship. The results suggest that INDO acts as an agonist at 5-HT1A receptor sites, but its activity at 5-HT(1B/2C) receptor sites also contributes to its discriminative function.

5-Methoxytryptamine↗

PubMed1993

Localization of superoxide anion in the red tide alga Chattonella antiqua.

To investigate the localization of superoxide anion generated in the red tide alga Chattonella antiqua, we added to the incubation medium 3,7-dihydro-6-[4-(2-(N'-(5-fluoresceinyl)thioureido) ethoxy)phenyl]-2-methylimidazo(1,2-a)pyrazin-3-one (FCLA), which is a Cypridina luciferin analogue and a specific fluorescent probe for detecting O2- and 1O2. The live phytoplankter was observed with the laser scanning microscope. At high magnification (x 6400) it was found that the plankter has many large and small verruciform protrusions on the cell surface. When the cell was irradiated with an argon laser (488 nm), a very intense fluorescence was noted at each protrusion. This fluorescence was completely inhibited by the addition of superoxide dismutase to the incubation medium, thus suggesting O2- generation at each verruciform protrusion on the cell surface.

Animals↗

PubMed2006

Di-imine copper(II) complexes as redox mediator and modulator in 2-deoxy-D-ribose oxidative damage.

Redox properties of copper complexes are important for their catalytic functions in vitro and in biological systems, and can contribute to their reactivity toward selected targets. In order to evaluate the influence of different ligands on the reactivity of copper ions, comparative studies were carried out with some copper(II) complexes containing a tridentate imine, or a tetradentate di-Schiff base ligand with a mixed pyridine, pyrazine, or imidazole donor set, acting as catalysts in the oxidation of 2-deoxy-D-ribose. Addition of the reducing agent glutathione (gamma-glutamylcysteinylglycine; GSH), which can also act as a good ligand for copper(I), mediated the oxidation of the substrate. For some of these compounds, a reductive activation followed by competition for the metal ion was verified, with formation of copper(I)-glutathione complex monitored by fluorescence measurements. For others, however, the reduction of the metal by the glutathione seems to not occur. In the presence of hydrogen peroxide, the oxidative damage is significantly enhanced for all the complexes tested. Redox potential measurements by cyclic voltammetry corroborated partially these results, indicating that the most reactive complexes are those with more positive redox potential. Evidence for site-specific attack to 2-deoxy-D-ribose was also observed, consistent with the intermediary formation of a copper-hydroxyl species, [LCu(II)(*OH)], rather than 'free' hydroxyl radical.

Copper↗

PubMed2000

Chemiluminescence because of the production of reactive oxygen species in the lungs of newborn piglets during resuscitation periods after asphyxiation load.

Reactive oxygen species are regarded as a possible cause of many diseases. However, there are few reports offering in vivo and in situ proof of the direct involvement of reactive oxygen species in the pathogenesis of disease. In the present study, the luciferin derivative 2-methyl-6-[4-methoxyphenyl]-3,7-dihydroimidazo [1,2-alpha] pyrazin-3-one (MCLA) was used to investigate the amount of reactive oxygen species produced during resuscitation after asphyxiation load in newborn piglets. The animals were first asphyxiated by stopping respiration for 4 min, and then resuscitated using 100% oxygen. When physiologic saline solution was administered, lung surface chemiluminescence had a mean value of 2, whereas with MCLA, a maximum luminescence of 580 was seen, demonstrating the possibility of measuring reactive oxygen species in vivo and in situ using MCLA. In a group in which resuscitation after acute asphyxiation was performed with 21% oxygen, the relative maximum lung surface chemiluminescence was 59.5+/-39, whereas that for a group in which resuscitation was performed using 100% oxygen had a significantly higher value of 186.1+/-72.5. Consequently, ventilation and especially resuscitation by 100% oxygen may represent a potential danger.

Animals↗

PubMed2002

Amitriptyline has a dual effect on the conductive properties of the epithelial Na channel.

This study was undertaken with the aim of testing the action of amitriptyline on the epithelial Na channel (ENaC), which belongs to the same family (Deg/ENaC) as ASICs (acid-sensing ion channels) and many other putative members in the brain. We assumed that, having a common protein structure, characterization of the amitriptyline-ENaC interaction could help to elucidate the analgesic mechanism of this tricyclic antidepressant. Na-channel characteristics were derived from the analysis of blocker-induced lorentzian noise produced by amiloride. The effect of amitriptyline, present in the mucosal bathing solution, on the transepithelial short-circuit current (I(sc)) and conductance (G(t)), and on the blocker-induced noise of apical Na channels, was studied on isolated ventral skin of the frog Rana ridibunda. Amitriptyline exerted a dual effect on the macroscopic short-circuit current and conductance of the epithelia, increasing these two parameters in the concentration range 0.1-50 microM, while at higher concentrations (100-1000 microM) it showed an inhibitory action. The decrease in the association rate (k(01)) of amiloride to the apical Na channels from 15.6+/-4.2 microM(-1) s(-1) in control Cl-Ringer to 7.4+/-1.7 microM(-1) s(-1) at 200 microM amitriptyline in a concentration-dependent manner suggests a competitive binding of amitriptyline to the pyrazine ring binding site for amiloride.

Algorithms↗

PubMed1995

Possible involvement of dihydrofructosazine in the DNA breaking activity of D-glucosamine.

Dehydrochlorination of D-glucosamine (2-amino-2-deoxy-D-glucose) hydrochloride with an anion exchange resin made its DNA breaking activity in plasmid pBR322 much higher, especially in the presence of Cu2+. The sample of anion exchanger-treated D-glucosamine hydrochloride, i.e., HCL-free D-glucosamine sample, showed an absorption maximum at 274 nm on the UV absorption spectrum in water as seen in the case of fructosazine [2,5-bis(D-arabino-tetrahydroxybutyl)pyrazine] one of the dimers of D-glucosamine. On a positive-ion fast atom bombardment (FAB) mass spectrum, the sample showed an ion peak at m/z 323 as a base peak, corresponding to dihydrofructosazine [2,5-bis(D-arabino-tetrahydroxybutyl) dihydropyrazine], which was a precursor of fructosazine, as well as those of D-glucosamine itself (m/z 180) and fructosazine (m/z 321). The DNA strand breaking activity of HCL-free D-glucosamine sample was directly proportional to the peak intensity of m/z 323 ion, while the DNA breaking activity of fructosazine was much weaker than that of HCL-free D-glucosamine sample. 2,5-Dihydro-3,6-dimethylprazine and 2,3-dihydro-5,6-dimethylpyrazine having a dihydropyrazine skeleton the same as dihydrofructosazine showed the same extent of DNA strand breaking activity as did the HCL-free D-glucosamine sample. These results indicated that dihydrofructosazine produced during the dehydrochlorination is closely involved in the DNA breaking activity of HCL-free D-glucosamine sample.

DNA Damage↗

PubMed1995

Amino acids and peptides. XL. Synthesis of Ac-Tyr-Val-Ala-Asp-MCA using newly developed acetylating reagent.

2-Acetoxy-3-benzyl-5-methyl-6-isobutylpyrazine was prepared by cyclization of H-Phe-Leu-CH2Cl, followed by acetylation with acetic anhydride. This pyrazine derivative can react with amino groups of amino acids or peptides to produce acetyl amino acids or acetyl peptides without acetylation of hydroxy group of Tyr, Ser and Thr. Using this acetylating reagent, Ac-Tyr-Val-Ala-Asp-MCA, which is a specific substrate of the interleukin-I (IL-I) processing enzyme, was prepared.

Alkylating Agents↗

PubMed2001

[Formations and reactions of aromatic furazan compounds].

A reaction from various kinds of nitroquinoline with hydroxylamine in potassium hydroxide alkalinity produced a novel product, furazanoquinoline, besides the known amino derivatives. The products obtained were furazano [3,4-f] quinoline (5) from 5-nitroquinoline (1) and 6-nitroquinoline (6), and furazano [3,4-h] quinoline (10) from 7-nitroquinoline (8) and 8-nitroquinoline (11). The reaction mechanism was believed to be as shown in Figs. 2 and 3. The photoreaction of benzofuroxan (19) in acetonitrile containing a little water, under a high pressure mercury lamp, produced 1H-azepine-2,7-dione (20), while under irradiation using a low pressure lamp, 6H-furazano [4,5-c] carbazole-3-oxide (21) and compound 20 were obtained. Then the photoproduct 20 produced photodimer 22 by irradiation in acetonitrile: water (9:1, v/v) using a high or low pressure mercury lamp, while photolysis with alkali proceeded as in the photoreaction of N-alkylimide to give 7-hydroxy-1H-azepine-2-one (23). When pyrido [2,3-c] furoxan (24) was irradiated in acetonitrile containing a little water with a low pressure mercury lamp, 3-nitro-2-pyridone (25) was obtained. When compound 24 was irradiated in the presence of morpholine with a low pressure mercury lamp in an argon atmosphere, 6-morpholinopyridine 2,3-dioxime (26) was produced. Quinoxaline 1,4-dioxide derivatives (31, 33), phenazine 5,10-dioxide derivatives (36, 37) and pyrido [2,3-b] pyrazine derivatives (38, 39) were synthesized from the corresponding furoxan catalyzed by silica gel or molecular sieves, and their antibacterial properties were evaluated. The results of antibacterial screening tests in vitro, revealed strong activity against Bacteroides fragilis.

Bacteroides fragilis↗

PubMed2002

Volatile compounds of headspace gas in the Japanese fish sauce ishiru.

Volatile compounds from the headspace gas of ten brands of the Japanese fish sauce ishiru were analyzed by GC-MS with a thermal-desorption cold-trap system. Many volatile peaks were detected and 51 compounds were identified. The major volatile compounds in ishiru included aldehydes (such as 2-methylpropanal, 2-methylbutanal, 3-methylbutanal, and benzaldehyde), nitrogen-containing compounds (such as pyrazine derivatives and trimethylamine), sulfur-containing compounds (such as dimethyl disulfide), and ketones (such as 2-butanone and 3-methyl-2-butanone). On the other hand, volatile fatty acids were nearly absent in the headspace gas of ishiru.

Chromatography, Gas↗

PubMed1995

[Effect of coenzyme Q10 on endotoxin induced hepatocyte injury modulation of endotoxin-activated polymorphonuclear neutrophils].

The effect of coenzyme Q10 (CoQ10) on hepatocyte injury during endotoxin (ET) shock in rats was studied with special reference to the role of polymorphonuclear neutrophils (PMN). ET shock was induced by intravenous administration of 5 mg/kg ET, and CoQ10 was given at 20 mg/kg once or 3 times orally or intravenously. We examined plasma glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), and glutamate dehydrogenase (GLDH) levels, superoxide production by PMN, the phagocytic activity of PMN, the cytotoxicity of PMN to liver cells, and histological changes in the liver. The CoQ10-treated rats showed lower levels of GOT, GPT, and GLDH than rats treated with ET only. When compared to the group given ET only superoxide production by PMN induced by 2-methyl-6-phenyl-3,7-dihydroimidazol [1,2-alpha]pyrazin-3-one (MCLA) was significantly inhibited in the group given CoQ10 intravenously and 3 times orally, but there was no significant difference in the group given CoQ10 once orally. However, the level of superoxide production by PMN stimulated by phorbol myristate acetate (PMA) was lower in all CoQ10-treated rats than in those given ET only. There was no difference in either peripheral PMN counts or PMN phagocytes between the CoQ10-treated group and the group given ET only. Histologically, the hepatocyte injury in all groups that received CoQ10 was milder than that in the ET-only group. No hepatocyte cytotoxicity by PMN was observed in any group that received CoQ10. These results suggest that both intravenous and oral administration of CoQ10 can modulate the endotoxin-activated PMN, and is useful for preventing hepatocyte injury during ET shock.

Animals↗

PubMed1986

Browning reaction systems as sources of mutagens and antimutagens.

Heated food systems contain hundreds of chemical compounds, some being mutagenic and others being antimutagenic. Studies have indicated that foods exposed to drying, frying, roasting, baking, and broiling conditions possess net mutagenic activity as assessed by the Ames/Salmonella/microsome mutagenicity test and the chromosome aberration assay with Chinese hamster ovary (CHO) cells. With the above-mentioned heat treatment of food, nonenzymic browning reactions are generally proceeding at rapid rates and are involved in the development of mutagens. Caramelization and Maillard reactions are two important pathways in the nonenzymic browning of food and are responsible for the formation of volatile aromatic compounds, intermediate nonvolatile compounds, and brown pigments called melanoidins. Heated sugar-amino acid mixtures possessed mutagenic activities which have been assessed by short-term bioassays. Purified Maillard and caramelization reaction products such as reductones, dicarbonyls, pyrazines, and furan derivatives have exhibited mutagenicity and clastogenicity. The water-insoluble fraction (WIF) of instant coffee and a model-system melanoidin (MSM) have been shown to inhibit the mutagenicity of known carcinogens--aflatoxin B1 (AFB1), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and benzo(a)pyrene (BP)--in aqueous dispersion. WIF and MSM were found to be effective binding agents for the carcinogens.

Food Analysis↗

PubMed2005

Inhibition of neovascularization by environmental agents.

The formation of new blood vessels, neovascularization, occurs by two unique processes: vasculogenesis, the de novo assembly of blood vessels from angioblast precursors, and angiogenesis, the formation of new capillary sprouts from preexisting vessels. There are many potential targets by which environmental pollutants may inhibit neovascularization and thus there are many possible phenotypic outcomes. Two examples of environmental pollutants that have been demonstrated to inhibit neovascularization include 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a prototypical halogenated aromatic hydrocarbon, and constituents found in environmental tobacco smoke. Studies have shown that TCDD disrupts neoangiogenesis by inhibiting the expression of angiogenic stimuli as well as by reducing the responsiveness of endothelial cells to those stimuli. Additionally, studies have shown that constituents of environmental tobacco smoke, including pyradine and pyrazine derivatives, can potently inhibit the angiogenic process of branching as well as the vasculogenic process involved in capillary plexus formation. Further, the inhibition of neovascularization by either TCDD or environmental tobacco smoke constituents is associated with reduced endothelial cell proliferation and altered expression of extracellular matrix proteins. Future research that identifies the specific angiogenic signaling pathways that are disrupted by these pollutants will improve our ability to assess their risk to human health. Finally, it is likely that many other environmental pollutants impact neovascularization; however, very few have been studied in sufficient detail. Thus, additional research also is needed to identify those environmental agents that mediate their toxicity by disrupting neovascularization.

Animals↗

PubMedDate not supplied

Feasibility of using fluoresceinyl Cypridina luciferin analog in a novel chemiluminescence method for real-time photodynamic therapy dosimetry.

Singlet oxygen ((1)O(2)) is the most important cytotoxic agent in photodynamic therapy (PDT). The feasibility of using a chemiluminescence (CL) probe, 3,7-dihydro-6-[4-(2-(N'-(5-fluoresceinyl)thioureido)ethoxy)phenyl]-2-methylimidazo{1,2-a}pyrazin-3-one sodium salt (fluoresceinyl Cypridina luciferin analog, FCLA), to monitor (1)O(2) production during PDT is evaluated in vitro. Lymphoma cells were treated with various protocols of PDT. The results show that the FCLA-CL production during PDT is linearly related to the corresponding cytotoxicity, regardless of the treatment protocol. With minimum cytotoxicity and interference to the PDT treatment outcome, the FCLA-CL system is an effective means to quantify PDT (1)O(2) production and may provide an alternative real-time dosimeter.

Cell Survival↗

PubMed2003

Electrochemical and phosphorescent properties of new mixed-ligand Ir(II) complexes coordinated with both terpyridine and various bipyridine derivatives.

Seven useful mixed-ligand complexes in the form of [Ir(terpy)(L)Cl]2+ were prepared and their spectroscopic and electrochemical properties were investigated. The ligands used were terpy = 2,2':6',2''-terpyridine, L = 2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridine, 4,4'-diphenyl-2,2'-bipyridine, 1,10-phenanthroline, 5-phenyl-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline, 2,3-bis(2-pyridyl)pyrazine. Synthetic methods were developed by a sequential ligand-replacement which occurred in the reaction vessel using a microwave oven. All complexes showed that LUMOs are based on the pi-system contribution of the terpyridine ligand for [Ir(terpy)(bpy)Cl]2+, [Ir(terpy)(dmbpy)Cl]2+, [Ir(terpy)(dpbpy)Cl]2+, [Ir(terpy)(phen)Cl]2+, [Ir(terpy)(dpphen)Cl]2+ and [Ir(terpy)(phphen)Cl]2+. On the other hand, the LUMO in the [Ir(terpy)(bppz)Cl]2+ complex is localized on the pi-system of the bppz ligand, whereas the HOMOs in the iridium complexes are localized on the terpyridine ligand. It was found that Ir(terpy)(L)Cl emits in a fluid solution at room temperature. The ancillary ligands, such as terpy and bpy, have been explored to extend the lifetime of the triplet 3(pi-pi') excited states of Ir(III) terpyridine complexes. Ir(III) terpyridine units with an electron donor (dmbpy) or electron acceptor substituents (terpy, dpbpy, phphen, dpphen and bppz) are found to decrease the energy of the 3LC states for use as photosensitizer molecular components in supramolecular devices. The spectroscopic and electrochemical details are also reported herein.

Journal Article↗

PubMed2004

ppt level detection of samarium(III) with a coated graphite sensor based on an antibiotic.

N-[2-[4-[[[(Cyclohexylamino)carbonyl]amino]sulfonyl]phenyl]ethyl]-5-methyl pyrazine carboxamide (glipizid) was explored as an electro-active material for preparing a polymeric membrane-based sensor selective to samarium ions. The membrane incorporated 30% poly(vinyl chloride) (PVC), 53% benzyl acetate (BA), 11% glipizid and 6% sodium tetraphenyl borate. When coated on the surface of a graphite electrode, it exhibits Nernstian responses in the concentration range of 1.0 x 10(-5) to 1.0 x 10(-10) M, with a detection limit of 8.0 x 10(-11)M samarium. The electrode shows high selectivity towards samarium over several cations (alkali, alkaline earth, transition and heavy metal ions), and specially lanthanide ions. The proposed sensor has a very short response time (< 15 s), and can be used in a wide pH range for at least ten weeks. It was used as an indicator electrode in potentiometric titration of Sm(III) ions with an EDTA solution, and for determination of samarium in binary and ternary mixtures.

Anti-Bacterial Agents↗

PubMed2004

Electrochemical and luminescent properties of new mononuclear ruthenium(II) and binuclear iridium(III)-ruthenium(II) terpyridine complexes.

Hexafluorophosphate salts of mononuclear complexes [Ru(II)Cl(L)(terpy)]+ (L = dmbpy (1); dpbpy (2), sambpy (3), and dpp (7), and binuclear complexes [Ru(II)2Cl2(dpp)(terpy)2]2+ (8) and [Ir(III)Ru(II)Cl2(dpp)(terpy)2]3+ (9) were prepared and characterized. Abbreviations of the ligands are bpy = 2,2'-bipyridine, dmbpy = 4,4'-dimethyl-2,2'-bipyridine, dpbpy = 4,4'-diphenyl-2,2'-bipyridine, dpp = 2,3-bis(2-pyridyl)pyrazine, sambpy = 4,4'-bis((S)-(+)-alpha-1-phenylethylamido)-2,2'-bipyridine, and terpy = 2,2':6',2''-terpyridine. The absorption spectra of 8 and 9 are dominated by ligand-centered bands in the UV region and by metal-to-ligand charge-transfer bands in the visible region. The details of their spectroscopic and electrochemical properties were investigated. In both binuclear complexes, it has been found that the HOMO is based on the Ru metal, and LUMO is dpp-based. [Ir(III)Ru(II)Cl2(dpp)(terpy)2]3+, indicating intense emission at room temperature, and a lifetime of 154 ns. The long lifetime of this bimetallic chromophore makes it a useful component in the design of supramolecular complexes.

Journal Article↗

PubMed2005

Novel antitumor agents: marine sponge alkaloids, their synthetic analogs and derivatives.

Present review describes research on novel natural antitumor agents isolated from marine sponges. More than 90 novel cytotoxic antitumor compounds and their synthetic analogs have shown confirmed activity in vitro tumor cell lines bioassay and are of current interest to NCI for further in vivo evaluation. A great problem, to use directly the reservoir of marine organisms for therapy is the very low availability and the isolation of only very small amounts of the biologically active substances from the natural materials. Thus, the synthetic chemistry is required to develop high yield synthetic methods, which are able to produce sufficient marine alkaloids for a broad biological screening. This review will present some of the aspects of the medicinal chemistry developed recently to introduce such modifications. The structures, origins, synthesis and biological activity of a selection of N-heterocyclic marine sponge alkaloids are reviewed. The emphasis is on compounds poised as potential anticancer drugs: pyrroles, pyrazines, imidazole, and other structural families. With computer program PASS some additional biological activities are also predicted, which point toward new possible applications of these compounds. This review emphasizes the role of marine sponge alkaloids as an important source of leads for drug discovery.

Alkaloids↗