Synthesis and in vitro microbial evaluation of La(III), Ce(III), Sm(III) and Y(III) metal complexes of vitamin B6 drug

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Al-Azab, Fathi M.; Al-Maydama, Hussein M. A.; Amin, Ragab R.; Jamil, Yasmin M. S.

2014-06-01

Metal complexes of pyridoxine mono hydrochloride (vitamin B6) are prepared using La(III), Ce(III), Sm(III) and Y(III). The resulting complexes are investigated. Some physical properties, conductivity, analytical data and the composition of the four pyridoxine complexes are discussed. The elemental analysis shows that the formed complexes of La(III), Ce(III), Sm(III) and Y(III) with pyridoxine are of 1:2 (metal:PN) molar ratio. All the synthesized complexes are brown in color and possess high melting points. These complexes are partially soluble in hot methanol, dimethylsulfoxide and dimethylformamide and insoluble in water and some other organic solvents. Elemental analysis data, spectroscopic (IR, UV-vis. and florescence), effective magnetic moment in Bohr magnetons and the proton NMR suggest the structures. However, definite particle size is determined by invoking the X-ray powder diffraction and scanning electron microscopy data. The results obtained suggested that pyridoxine reacted with metal ions as a bidentate ligand through its phenolate oxygen and the oxygen of the adjacent group at the 4‧-position. The molar conductance measurements proved that the pyridoxine complexes are electrolytic in nature. The kinetic and thermodynamic parameters such as: Ea, ΔH*, ΔS* and ΔG* were estimated from the DTG curves. The antibacterial evaluation of the pyridoxine and their complexes were also performed against some gram positive, negative bacteria as well as fungi.

Genetics Home Reference: mitochondrial complex III deficiency

MedlinePlus

... DNA packaged in chromosomes within the cell nucleus (nuclear DNA). It is not clear why the severity ... deficiency Genetic Testing Registry: Mitochondrial complex III deficiency, nuclear type 2 Genetic Testing Registry: Mitochondrial complex III ...

Immune evasion by pathogens of bovine respiratory disease complex.

PubMed

Srikumaran, Subramaniam; Kelling, Clayton L; Ambagala, Aruna

2007-12-01

Bovine respiratory tract disease is a multi-factorial disease complex involving several viruses and bacteria. Viruses that play prominent roles in causing the bovine respiratory disease complex include bovine herpesvirus-1, bovine respiratory syncytial virus, bovine viral diarrhea virus and parinfluenza-3 virus. Bacteria that play prominent roles in this disease complex are Mannheimia haemolytica and Mycoplasma bovis. Other bacteria that infect the bovine respiratory tract of cattle are Histophilus (Haemophilus) somni and Pasteurella multocida. Frequently, severe respiratory tract disease in cattle is associated with concurrent infections of these pathogens. Like other pathogens, the viral and bacterial pathogens of this disease complex have co-evolved with their hosts over millions of years. As much as the hosts have diversified and fine-tuned the components of their immune system, the pathogens have also evolved diverse and sophisticated strategies to evade the host immune responses. These pathogens have developed intricate mechanisms to thwart both the innate and adaptive arms of the immune responses of their hosts. This review presents an overview of the strategies by which the pathogens suppress host immune responses, as well as the strategies by which the pathogens modify themselves or their locations in the host to evade host immune responses. These immune evasion strategies likely contribute to the failure of currently-available vaccines to provide complete protection to cattle against these pathogens.

Sparkle/AM1 Parameters for the Modeling of Samarium(III) and Promethium(III) Complexes.

PubMed

Freire, Ricardo O; da Costa, Nivan B; Rocha, Gerd B; Simas, Alfredo M

2006-01-01

The Sparkle/AM1 model is extended to samarium(III) and promethium(III) complexes. A set of 15 structures of high crystallographic quality (R factor < 0.05 Å), with ligands chosen to be representative of all samarium complexes in the Cambridge Crystallographic Database 2004, CSD, with nitrogen or oxygen directly bonded to the samarium ion, was used as a training set. In the validation procedure, we used a set of 42 other complexes, also of high crystallographic quality. The results show that this parametrization for the Sm(III) ion is similar in accuracy to the previous parametrizations for Eu(III), Gd(III), and Tb(III). On the other hand, promethium is an artificial radioactive element with no stable isotope. So far, there are no promethium complex crystallographic structures in CSD. To circumvent this, we confirmed our previous result that RHF/STO-3G/ECP, with the MWB effective core potential (ECP), appears to be the most efficient ab initio model chemistry in terms of coordination polyhedron crystallographic geometry predictions from isolated lanthanide complex ion calculations. We thus generated a set of 15 RHF/STO-3G/ECP promethium complex structures with ligands chosen to be representative of complexes available in the CSD for all other trivalent lanthanide cations, with nitrogen or oxygen directly bonded to the lanthanide ion. For the 42 samarium(III) complexes and 15 promethium(III) complexes considered, the Sparkle/AM1 unsigned mean error, for all interatomic distances between the Ln(III) ion and the ligand atoms of the first sphere of coordination, is 0.07 and 0.06 Å, respectively, a level of accuracy comparable to present day ab initio/ECP geometries, while being hundreds of times faster.

Exome sequencing identifies NFS1 deficiency in a novel Fe-S cluster disease, infantile mitochondrial complex II/III deficiency.

PubMed

Farhan, Sali M K; Wang, Jian; Robinson, John F; Lahiry, Piya; Siu, Victoria M; Prasad, Chitra; Kronick, Jonathan B; Ramsay, David A; Rupar, C Anthony; Hegele, Robert A

2014-01-01

Iron-sulfur (Fe-S) clusters are a class of highly conserved and ubiquitous prosthetic groups with unique chemical properties that allow the proteins that contain them, Fe-S proteins, to assist in various key biochemical pathways. Mutations in Fe-S proteins often disrupt Fe-S cluster assembly leading to a spectrum of severe disorders such as Friedreich's ataxia or iron-sulfur cluster assembly enzyme (ISCU) myopathy. Herein, we describe infantile mitochondrial complex II/III deficiency, a novel autosomal recessive mitochondrial disease characterized by lactic acidemia, hypotonia, respiratory chain complex II and III deficiency, multisystem organ failure and abnormal mitochondria. Through autozygosity mapping, exome sequencing, in silico analyses, population studies and functional tests, we identified c.215G>A, p.Arg72Gln in NFS1 as the likely causative mutation. We describe the first disease in man likely caused by deficiency in NFS1, a cysteine desulfurase that is implicated in respiratory chain function and iron maintenance by initiating Fe-S cluster biosynthesis. Our results further demonstrate the importance of sufficient NFS1 expression in human physiology.

Sparkle model for the calculation of lanthanide complexes: AM1 parameters for Eu(III), Gd(III), and Tb(III).

PubMed

Freire, Ricardo O; Rocha, Gerd B; Simas, Alfredo M

2005-05-02

Our previously defined Sparkle model (Inorg. Chem. 2004, 43, 2346) has been reparameterized for Eu(III) as well as newly parameterized for Gd(III) and Tb(III). The parameterizations have been carried out in a much more extensive manner, aimed at producing a new, more accurate model called Sparkle/AM1, mainly for the vast majority of all Eu(III), Gd(III), and Tb(III) complexes, which possess oxygen or nitrogen as coordinating atoms. All such complexes, which comprise 80% of all geometries present in the Cambridge Structural Database for each of the three ions, were classified into seven groups. These were regarded as a "basis" of chemical ambiance around a lanthanide, which could span the various types of ligand environments the lanthanide ion could be subjected to in any arbitrary complex where the lanthanide ion is coordinated to nitrogen or oxygen atoms. From these seven groups, 15 complexes were selected, which were defined as the parameterization set and then were used with a numerical multidimensional nonlinear optimization to find the best parameter set for reproducing chemical properties. The new parameterizations yielded an unsigned mean error for all interatomic distances between the Eu(III) ion and the ligand atoms of the first sphere of coordination (for the 96 complexes considered in the present paper) of 0.09 A, an improvement over the value of 0.28 A for the previous model and the value of 0.68 A for the first model (Chem. Phys. Lett. 1994, 227, 349). Similar accuracies have been achieved for Gd(III) (0.07 A, 70 complexes) and Tb(III) (0.07 A, 42 complexes). Qualitative improvements have been obtained as well; nitrates now coordinate correctly as bidentate ligands. The results, therefore, indicate that Eu(III), Gd(III), and Tb(III) Sparkle/AM1 calculations possess geometry prediction accuracies for lanthanide complexes with oxygen or nitrogen atoms in the coordination polyhedron that are competitive with present day ab initio/effective core potential

Organometallic neptunium(III) complexes

NASA Astrophysics Data System (ADS)

Dutkiewicz, Michał S.; Farnaby, Joy H.; Apostolidis, Christos; Colineau, Eric; Walter, Olaf; Magnani, Nicola; Gardiner, Michael G.; Love, Jason B.; Kaltsoyannis, Nikolas; Caciuffo, Roberto; Arnold, Polly L.

2016-08-01

Studies of transuranic organometallic complexes provide a particularly valuable insight into covalent contributions to the metal-ligand bonding, in which the subtle differences between the transuranium actinide ions and their lighter lanthanide counterparts are of fundamental importance for the effective remediation of nuclear waste. Unlike the organometallic chemistry of uranium, which has focused strongly on UIII and has seen some spectacular advances, that of the transuranics is significantly technically more challenging and has remained dormant. In the case of neptunium, it is limited mainly to NpIV. Here we report the synthesis of three new NpIII organometallic compounds and the characterization of their molecular and electronic structures. These studies suggest that NpIII complexes could act as single-molecule magnets, and that the lower oxidation state of NpII is chemically accessible. In comparison with lanthanide analogues, significant d- and f-electron contributions to key NpIII orbitals are observed, which shows that fundamental neptunium organometallic chemistry can provide new insights into the behaviour of f-elements.

Myoglobin and the regulation of mitochondrial respiratory chain complex IV.

PubMed

Yamada, Tatsuya; Takakura, Hisashi; Jue, Thomas; Hashimoto, Takeshi; Ishizawa, Rie; Furuichi, Yasuro; Kato, Yukio; Iwanaka, Nobumasa; Masuda, Kazumi

2016-01-15

Mitochondrial respiration is regulated by multiple elaborate mechanisms. It has been shown that muscle specific O2 binding protein, Myoglobin (Mb), is localized in mitochondria and interacts with respiratory chain complex IV, suggesting that Mb could be a factor that regulates mitochondrial respiration. Here, we demonstrate that muscle mitochondrial respiration is improved by Mb overexpression via up-regulation of complex IV activity in cultured myoblasts; in contrast, suppression of Mb expression induces a decrease in complex IV activity and mitochondrial respiration compared with the overexpression model. The present data are the first to show the biological significance of mitochondrial Mb as a potential modulator of mitochondrial respiratory capacity. Mitochondria are important organelles for metabolism, and their respiratory capacity is a primary factor in the regulation of energy expenditure. Deficiencies of cytochrome c oxidase complex IV, which reduces O2 in mitochondria, are linked to several diseases, such as mitochondrial myopathy. Moreover, mitochondrial respiration in skeletal muscle tissue tends to be susceptible to complex IV activity. Recently, we showed that the muscle-specific protein myoglobin (Mb) interacts with complex IV. The precise roles of mitochondrial Mb remain unclear. Here, we demonstrate that Mb facilitates mitochondrial respiratory capacity in skeletal muscles. Although mitochondrial DNA copy numbers were not altered in Mb-overexpressing myotubes, O2 consumption was greater in these myotubes than that in mock cells (Mock vs. Mb-Flag::GFP: state 4, 1.00 ± 0.09 vs. 1.77 ± 0.34; state 3, 1.00 ± 0.29; Mock: 1.60 ± 0.53; complex 2-3-4: 1.00 ± 0.30 vs. 1.50 ± 0.44; complex IV: 1.00 ± 0.14 vs. 1.87 ± 0.27). This improvement in respiratory capacity could be because of the activation of enzymatic activity of respiratory complexes. Moreover, mitochondrial respiration was up-regulated in myoblasts transiently

Complexity measures of the central respiratory networks during wakefulness and sleep

NASA Astrophysics Data System (ADS)

Dragomir, Andrei; Akay, Yasemin; Curran, Aidan K.; Akay, Metin

2008-06-01

Since sleep is known to influence respiratory activity we studied whether the sleep state would affect the complexity value of the respiratory network output. Specifically, we tested the hypothesis that the complexity values of the diaphragm EMG (EMGdia) activity would be lower during REM compared to NREM. Furthermore, since REM is primarily generated by a homogeneous population of neurons in the medulla, the possibility that REM-related respiratory output would be less complex than that of the awake state was also considered. Additionally, in order to examine the influence of neuron vulnerabilities within the rostral ventral medulla (RVM) on the complexity of the respiratory network output, we inhibited respiratory neurons in the RVM by microdialysis of GABAA receptor agonist muscimol. Diaphragm EMG, nuchal EMG, EEG, EOG as well as other physiological signals (tracheal pressure, blood pressure and respiratory volume) were recorded from five unanesthetized chronically instrumented intact piglets (3-10 days old). Complexity of the diaphragm EMG (EMGdia) signal during wakefulness, NREM and REM was evaluated using the approximate entropy method (ApEn). ApEn values of the EMGdia during NREM and REM sleep were found significantly (p < 0.05 and p < 0.001, respectively) lower than those of awake EMGdia after muscimol inhibition. In the absence of muscimol, only the differences between REM and wakefulness ApEn values were found to be significantly different.

NMR and TRLFS studies of Ln(iii) and An(iii) C5-BPP complexes.

PubMed

Adam, Christian; Beele, Björn B; Geist, Andreas; Müllich, Udo; Kaden, Peter; Panak, Petra J

2015-02-01

C5-BPP is a highly efficient N-donor ligand for the separation of trivalent actinides, An(iii), from trivalent lanthanides, Ln(iii). The molecular origin of the selectivity of C5-BPP and many other N-donor ligands of the BTP-type is still not entirely understood. We present here the first NMR studies on C5-BPP Ln(iii) and An(iii) complexes. C5-BPP is synthesized with 10% 15 N labeling and characterized by NMR and LIFDI-MS methods. 15 N NMR spectroscopy gives a detailed insight into the bonding of C5-BPP with lanthanides and Am(iii) as a representative for trivalent actinide cations, revealing significant differences in 15 N chemical shift for coordinating nitrogen atoms compared to Ln(iii) complexes. The temperature dependence of NMR chemical shifts observed for the Am(iii) complex indicates a weak paramagnetism. This as well as the observed large chemical shift for coordinating nitrogen atoms show that metal-ligand bonding in Am(C5-BPP) 3 has a larger share of covalence than in lanthanide complexes, confirming earlier studies. The Am(C5-BPP) 3 NMR sample is furthermore spiked with Cm(iii) and characterized by time-resolved laser fluorescence spectroscopy (TRLFS), yielding important information on the speciation of trace amounts of minor complex species.

Chemicals or mutations that target mitochondrial translation can rescue the respiratory deficiency of yeast bcs1 mutants.

PubMed

Panozzo, C; Laleve, A; Tribouillard-Tanvier, D; Ostojić, J; Sellem, C H; Friocourt, G; Bourand-Plantefol, A; Burg, A; Delahodde, A; Blondel, M; Dujardin, G

2017-12-01

Bcs1p is a chaperone that is required for the incorporation of the Rieske subunit within complex III of the mitochondrial respiratory chain. Mutations in the human gene BCS1L (BCS1-like) are the most frequent nuclear mutations resulting in complex III-related pathologies. In yeast, the mimicking of some pathogenic mutations causes a respiratory deficiency. We have screened chemical libraries and found that two antibiotics, pentamidine and clarithromycin, can compensate two bcs1 point mutations in yeast, one of which is the equivalent of a mutation found in a human patient. As both antibiotics target the large mtrRNA of the mitoribosome, we focused our analysis on mitochondrial translation. We found that the absence of non-essential translation factors Rrf1 or Mif3, which act at the recycling/initiation steps, also compensates for the respiratory deficiency of yeast bcs1 mutations. At compensating concentrations, both antibiotics, as well as the absence of Rrf1, cause an imbalanced synthesis of respiratory subunits which impairs the assembly of the respiratory complexes and especially that of complex IV. Finally, we show that pentamidine also decreases the assembly of complex I in nematode mitochondria. It is well known that complexes III and IV exist within the mitochondrial inner membrane as supramolecular complexes III 2 /IV in yeast or I/III 2 /IV in higher eukaryotes. Therefore, we propose that the changes in mitochondrial translation caused by the drugs or by the absence of translation factors, can compensate for bcs1 mutations by modifying the equilibrium between illegitimate, and thus inactive, and active supercomplexes. Copyright © 2017. Published by Elsevier B.V.

Crystal structure of mitochondrial respiratory membrane protein complex II.

PubMed

Sun, Fei; Huo, Xia; Zhai, Yujia; Wang, Aojin; Xu, Jianxing; Su, Dan; Bartlam, Mark; Rao, Zihe

2005-07-01

The mitochondrial respiratory Complex II or succinate:ubiquinone oxidoreductase (SQR) is an integral membrane protein complex in both the tricarboxylic acid cycle and aerobic respiration. Here we report the first crystal structure of Complex II from porcine heart at 2.4 A resolution and its complex structure with inhibitors 3-nitropropionate and 2-thenoyltrifluoroacetone (TTFA) at 3.5 A resolution. Complex II is comprised of two hydrophilic proteins, flavoprotein (Fp) and iron-sulfur protein (Ip), and two transmembrane proteins (CybL and CybS), as well as prosthetic groups required for electron transfer from succinate to ubiquinone. The structure correlates the protein environments around prosthetic groups with their unique midpoint redox potentials. Two ubiquinone binding sites are discussed and elucidated by TTFA binding. The Complex II structure provides a bona fide model for study of the mitochondrial respiratory system and human mitochondrial diseases related to mutations in this complex.

Structure of the alternative complex III in a supercomplex with cytochrome oxidase.

PubMed

Sun, Chang; Benlekbir, Samir; Venkatakrishnan, Padmaja; Wang, Yuhang; Hong, Sangjin; Hosler, Jonathan; Tajkhorshid, Emad; Rubinstein, John L; Gennis, Robert B

2018-05-01

Alternative complex III (ACIII) is a key component of the respiratory and/or photosynthetic electron transport chains of many bacteria 1-3 . Like complex III (also known as the bc 1 complex), ACIII catalyses the oxidation of membrane-bound quinol and the reduction of cytochrome c or an equivalent electron carrier. However, the two complexes have no structural similarity 4-7 . Although ACIII has eluded structural characterization, several of its subunits are known to be homologous to members of the complex iron-sulfur molybdoenzyme (CISM) superfamily 8 , including the proton pump polysulfide reductase 9,10 . We isolated the ACIII from Flavobacterium johnsoniae with native lipids using styrene maleic acid copolymer 11-14 , both as an independent enzyme and as a functional 1:1 supercomplex with an aa 3 -type cytochrome c oxidase (cyt aa 3 ). We determined the structure of ACIII to 3.4 Å resolution by cryo-electron microscopy and constructed an atomic model for its six subunits. The structure, which contains a [3Fe-4S] cluster, a [4Fe-4S] cluster and six haem c units, shows that ACIII uses known elements from other electron transport complexes arranged in a previously unknown manner. Modelling of the cyt aa 3 component of the supercomplex revealed that it is structurally modified to facilitate association with ACIII, illustrating the importance of the supercomplex in this electron transport chain. The structure also resolves two of the subunits of ACIII that are anchored to the lipid bilayer with N-terminal triacylated cysteine residues, an important post-translational modification found in numerous prokaryotic membrane proteins that has not previously been observed structurally in a lipid bilayer.

Reactions of a Chromium(III)-Superoxo Complex and Nitric Oxide That Lead to the Formation of Chromium(IV)-Oxo and Chromium(III)-Nitrito Complexes

PubMed Central

Yokoyama, Atsutoshi; Cho, Kyung-Bin

2013-01-01

The reaction of an end-on Cr(III)-superoxo complex bearing a 14-membered tetraazamacrocyclic TMC ligand, [CrIII(14-TMC)(O2)(Cl)]+, with nitric oxide (NO) resulted in the generation of a stable Cr(IV)-oxo species, [CrIV(14-TMC)(O)(Cl)]+, via the formation of a Cr(III)-peroxynitrite intermediate and homolytic O-O bond cleavage of the peroxynitrite ligand. Evidence for the latter comes from EPR spectroscopy, computational chemistry, and the observation of phenol nitration chemistry. The Cr(IV)-oxo complex does not react with nitrogen dioxide (NO2), but reacts with NO to afford a Cr(III)-nitrito complex, [CrIII(14-TMC)(NO2)(Cl)]+. The Cr(IV)-oxo and Cr(III)-nitrito complexes were also characterized spectroscopically and/or structurally. PMID:24066924

Photofunctional triplet excited states of cyclometalated Ir(III) complexes: beyond electroluminescence.

PubMed

You, Youngmin; Nam, Wonwoo

2012-11-07

The development of cyclometalated Ir(III) complexes has enabled important breakthroughs in electroluminescence because such complexes permit the efficient population of triplet excited states that give rise to luminescent transitions. The triplet states of Ir(III) complexes are advantageous over those of other transition metal complexes in that their electronic transitions and charge-transfer characteristics are tunable over wide ranges. These favorable properties suggest that Ir(III) complexes have significant potential in a variety of photofunctions other than electroluminescence. In this critical review, we describe recent photonic applications of novel Ir(III) complexes. Ir(III) complexes have been shown to affect the exciton statistics in the active layers of organic photovoltaic cells, thereby improving the photon-to-current conversion efficiencies. Nonlinear optical applications that take advantage of the strong charge-transfer properties of triplet transitions are also discussed. The tunability of the electrochemical potentials facilitates the development of efficient photocatalysis in the context of water photolysis or organic syntheses. The photoredox reactivities of Ir(III) complexes have been employed in studies of charge migration along DNA chains. The photoinduced cytotoxicity of Ir(III) complexes on live cells suggests that the complexes may be useful in photodynamic therapy. Potential biological applications of the complexes include phosphorescence labeling and sensing. Intriguing platforms based on cyclometalated Ir(III) complexes potentially provide novel protein tagging and ratiometric detection. We envision that future research into the photofunctionality of Ir(III) complexes will provide important breakthroughs in a variety of photonic applications.

Investigation of complexes tannic acid and myricetin with Fe(III)

NASA Astrophysics Data System (ADS)

Sungur, Şana; Uzar, Atike

2008-01-01

The pH dependence of the complexes was determined by both potentiometric and spectrophotometric studies. Stability constants and stoichiometries of the formed complexes were determined using slope ratio method. Fe(III) was formed complexes with tannic acid of various stoichiometries, which in the 1:1 molar ratio at pH < 3, in the 2:1 molar ratio at pH 3-7 and in the 4:1 molar ratio at pH > 7. Fe(III) was formed complexes with myricetin in the 1:2 molar ratio at pH 4 and 5 and in the 1:1 molar ratio at pH 6. Stability constant values were found to be 10 5 to 10 17 and 10 5 to 10 9 for Fe(III)-tannic acid complexes and Fe(III)-myricetin complexes. Both tannic acid and myricetin were possessed minimum affinities to Cu(II) and Zn(II). They had less affinity for Al(III) than for Fe(III).

Hydrogen-impurity complexes in III V semiconductors

NASA Astrophysics Data System (ADS)

Ulrici, W.

2004-12-01

This review summarizes the presently available knowledge concerning hydrogen-impurity complexes in III-V compounds. The impurities form shallow acceptors on group III sites (Be, Zn, Cd) and on group V sites (C, Si, Ge) as well as shallow donors on group V sites (S, Se, Te) and on group III sites (Si, Sn). These complexes are mainly revealed by their hydrogen stretching modes. Therefore, nearly all information about their structure and dynamic properties is derived from vibrational spectroscopy. The complexes of shallow impurities with hydrogen have been most extensively investigated in GaAs, GaP and InP. This holds also for Mg-H in GaN. The complexes exhibit a different microscopic structure, which is discussed in detail. The isoelectronic impurity nitrogen, complexed with one hydrogen atom, is investigated in detail in GaAs and GaP. Those complexes can exist in different charge states. The experimental results such as vibrational frequencies, the microscopic structure and the activation energy for reorientation for many of these complexes are in very good agreement with results of ab initio calculations. Different types of oxygen-hydrogen complexes in GaAs and GaP are described, with one hydrogen atom or two hydrogen atoms bonded to oxygen. Three of these complexes in GaAs were found to be electrically active.

Effect of hexavalent chromium on electron leakage of respiratory chain in mitochondria isolated from rat liver.

PubMed

Xie, Ying; Zhong, Caigao; Zeng, Ming; Guan, Lan; Luo, Lei

2013-01-01

In the present study, we explored reactive axygen species (ROS) production in mitochondria, the mechanism of hexavalent chromium (Cr(VI)) hepatotoxicity, and the role of protection by GSH. Intact mitochondria were isolated from rat liver tissues and mitochondrial basal respiratory rates of NADH and FADH2 respiratory chains were determined. Mitochondria were treated with Cr(VI), GSH and several complex inhibitors. Mitochondria energized by glutamate/malate were separately or jointly treated with Rotenone (Rot), diphenyleneiodonium (DPI) and antimycinA (Ant), while mitochondria energized by succinate were separately or jointly treated with Rot, DPI ' thenoyltrifluoroacetone (TTFA) and Ant. Cr(VI) concentration-dependently induced ROS production in the NADH and FADH2 respiratory chain in liver mitochondria. Basal respiratory rate of the mitochondrial FADH2 respiratory chain was significantly higher than that of NADH respiratory chain. Hepatic mitochondrial electron leakage induced by Cr(VI) from NADH respiratory chain were mainly from ubiquinone binding sites of complex I and complex III. Treatment with 50µM Cr(VI) enhances forward movement of electrons through FADH2 respiratory chain and leaking through the ubiquinone binding site of complex III. Moreover, the protective effect of GSH on liver mitochondria electron leakage is through removing excess H2O2 and reducing total ROS. Copyright © 2013 S. Karger AG, Basel.

The Assembly Pathway of Mitochondrial Respiratory Chain Complex I.

PubMed

Guerrero-Castillo, Sergio; Baertling, Fabian; Kownatzki, Daniel; Wessels, Hans J; Arnold, Susanne; Brandt, Ulrich; Nijtmans, Leo

2017-01-10

Mitochondrial complex I is the largest integral membrane enzyme of the respiratory chain and consists of 44 different subunits encoded in the mitochondrial and nuclear genome. Its biosynthesis is a highly complicated and multifaceted process involving at least 14 additional assembly factors. How these subunits assemble into a functional complex I and where the assembly factors come into play is largely unknown. Here, we applied a dynamic complexome profiling approach to elucidate the assembly of human mitochondrial complex I and its further incorporation into respiratory chain supercomplexes. We delineate the stepwise incorporation of all but one subunit into a series of distinct assembly intermediates and their association with known and putative assembly factors, which had not been implicated in this process before. The resulting detailed and comprehensive model of complex I assembly is fully consistent with recent structural data and the remarkable modular architecture of this multiprotein complex. Copyright © 2017 Elsevier Inc. All rights reserved.

Structure and magnetism of a Mn(III)-Mn(II)-Mn(II)-Mn(III) chain complex.

PubMed

Uhrecký, Róbert; Moncoľ, Ján; Koman, Marian; Titiš, Ján; Boča, Roman

2013-07-14

A novel tetranuclear manganese(II/III) complex with anions of pyridine-2,6-dicarboxylic acid (dipicolinic acid) has been synthesised and magneto-structurally characterised. The crystal structure of [Mn(II)2Mn(III)2(dipic)6(H2O)4]·2CH3OH·4H2O has been determined by single-crystal X-ray diffraction. The tetranuclear complex molecule [Mn(II)2Mn(III)2(dipic)6(H2O)4] is centrosymmetric and two manganese(II) and two manganese(III) atoms are bridged by four dipicolinate ligands. The complex molecules and uncoordinated water and methanol molecules are connected through hydrogen bonds and they form a 3D supramolecular hydrogen-bonding network.

Roles of Neuroglobin Binding to Mitochondrial Complex III Subunit Cytochrome c1 in Oxygen-Glucose Deprivation-Induced Neurotoxicity in Primary Neurons.

PubMed

Yu, Zhanyang; Zhang, Yu; Liu, Ning; Yuan, Jing; Lin, Li; Zhuge, Qichuan; Xiao, Jian; Wang, Xiaoying

2016-07-01

Neuroglobin (Ngb) is a tissue globin specifically expressed in brain neurons. Recent studies by our laboratory and others have demonstrated that Ngb is protective against stroke and related neurological disorders, but the mechanisms remain poorly understood. We previously identified cytochrome c1 (Cyc1) as an Ngb-interacting molecule by yeast two-hybrid screening. Cyc1 is a subunit of mitochondria complex III, which is a component of mitochondrial respiratory chain and a major source of reactive oxygen species (ROS) production under both physiological and pathological conditions. In this study, we for the first time defined Ngb-Cyc1 binding, and investigated its roles in oxygen-glucose deprivation (OGD)/reoxygenation-induced neurotoxicity and ROS production in primary neurons. Immunocytochemistry and co-immunoprecipitation validated Ngb-Cyc1 binding, which was significantly increased by OGD and Ngb overexpression. We found 4 h OGD with/without 4 h reoxygenation significantly increased complex III activity, but this activity elevation was significantly attenuated in three groups of neurons: Ngb overexpression, specific complex III inhibitor stigmatellin, or stigmatellin plus Ngb overexpression, whereas there was no significant differences between these three groups, suggesting Ngb-Cyc1 binding may function in suppressing OGD-mediated complex III activity elevation. Importantly, these three groups of neurons also showed significant decreases in OGD-induced superoxide anion generation and neurotoxicity. These results suggest that Ngb can bind to mitochondrial complex III subunit Cyc1, leading to suppression of OGD-mediated complex III activity and subsequent ROS production elevation, and eventually reduction of OGD-induced neurotoxicity. This molecular signaling cascade may be at least part of the mechanisms of Ngb neuroprotection against OGD-induced neurotoxicity.

Acetate-Bridged Platinum(III) Complexes Derived from Cisplatin

PubMed Central

Wilson, Justin J.

2012-01-01

Oxidation of the acetate-bridged half-lantern platinum(II) complex, cis-[PtII(NH3)2(µ-OAc)2PtII(NH3)2](NO3)2, [1](NO3)2, with iodobenzene dichloride or bromine generates the halide-capped platinum(III) species, cis-[XPtIII(NH3)2(µ-OAc)2PtIII(NH3)2X](NO3)2, where X is Cl in [2](NO3)2, or Br in [3](NO3)2, respectively. These three complexes, characterized structurally by X-ray crystallography, feature short (≈ 2.6 Å) Pt–Pt separations, consistent with formation of a formal metal-metal bond upon oxidation. Elongated axial Pt–X distances occur, reflecting the strong trans influence of the metal-metal bond. The three structures are compared to those of other known dinuclear platinum complexes. A combination of 1H, 13C, 14N, and 195Pt NMR spectroscopy was used to characterize [1]2+–[3]2+ in solution. All resonances shift downfield upon oxidation of [1]2+ to [2]2+ and [3]2+. For the platinum(III) complexes, the 14N and 195Pt resonances exhibit decreased linewidths by comparison to those of [1]2+. Density functional theory (DFT) calculations suggest that the decrease in 14N linewidth arises from a diminished electric field gradient (EFG) at the 14N nuclei in the higher valent compounds. The oxidation of [1](NO3)2 with the alternative oxidizing agent, bis(trifluoroacetoxy) iodobenzene, affords the novel tetranuclear complex, cis-[(O2CCF3)PtIII(NH3)2(µ-OAc)2PtIII(NH3)(µ-NH2)]2(NO3)4, [4](NO3)4, also characterized structurally by X-ray crystallography. In solution, this complex exists as a mixture of species, the identities of which are proposed. PMID:22946515

Complexation and molecular modeling studies of europium(III)-gallic acid-amino acid complexes.

PubMed

Taha, Mohamed; Khan, Imran; Coutinho, João A P

2016-04-01

With many metal-based drugs extensively used today in the treatment of cancer, attention has focused on the development of new coordination compounds with antitumor activity with europium(III) complexes recently introduced as novel anticancer drugs. The aim of this work is to design new Eu(III) complexes with gallic acid, an antioxida'nt phenolic compound. Gallic acid was chosen because it shows anticancer activity without harming health cells. As antioxidant, it helps to protect human cells against oxidative damage that implicated in DNA damage, cancer, and accelerated cell aging. In this work, the formation of binary and ternary complexes of Eu(III) with gallic acid, primary ligand, and amino acids alanine, leucine, isoleucine, and tryptophan was studied by glass electrode potentiometry in aqueous solution containing 0.1M NaNO3 at (298.2 ± 0.1) K. Their overall stability constants were evaluated and the concentration distributions of the complex species in solution were calculated. The protonation constants of gallic acid and amino acids were also determined at our experimental conditions and compared with those predicted by using conductor-like screening model for realistic solvation (COSMO-RS) model. The geometries of Eu(III)-gallic acid complexes were characterized by the density functional theory (DFT). The spectroscopic UV-visible and photoluminescence measurements are carried out to confirm the formation of Eu(III)-gallic acid complexes in aqueous solutions. Copyright © 2016 Elsevier Inc. All rights reserved.

Investigations into the synthesis and fluorescence properties of Eu(III), Tb(III), Sm(III) and Gd(III) complexes of a novel bis- β-diketone-type ligand

NASA Astrophysics Data System (ADS)

Luo, Yi-Ming; Chen, Zhe; Tang, Rui-Ren; Xiao, Lin-Xiang; Peng, Hong-Jian

2008-02-01

A novel bis- β-diketon ligand, 1,1'-(2,6-bispyridyl)bis-3-phenyl-1,3-propane-dione (L), was designed and synthesized and its complexes with Eu(III), Tb(III), Sm(III) and Gd(III) ions were successfully prepared. The ligand and the corresponding metal complexes were characterized by elemental analysis, and infrared, mass and proton nuclear magnetic resonance spectroscopy. Analysis of the IR spectra suggested that each of the lanthanide metal ions coordinated to the ligand via the carbonyl oxygen atoms and the nitrogen atom of the pyridine ring. The fluorescence properties of these complexes in solid state were investigated and it was discovered that all of the lanthanide ions could be sensitized by the ligand (L) to some extent. In particular, the Tb(III) complex was an excellent green-emitter and would be a potential candidate material for applications in organic light-emitting devices (OLEDs) and medical diagnosis.

A well-defined terminal vanadium(III) oxo complex.

PubMed

King, Amanda E; Nippe, Michael; Atanasov, Mihail; Chantarojsiri, Teera; Wray, Curtis A; Bill, Eckhard; Neese, Frank; Long, Jeffrey R; Chang, Christopher J

2014-11-03

The ubiquity of vanadium oxo complexes in the V+ and IV+ oxidation states has contributed to a comprehensive understanding of their electronic structure and reactivity. However, despite being predicted to be stable by ligand-field theory, the isolation and characterization of a well-defined terminal mononuclear vanadium(III) oxo complex has remained elusive. We present the synthesis and characterization of a unique terminal mononuclear vanadium(III) oxo species supported by the pentadentate polypyridyl ligand 2,6-bis[1,1-bis(2-pyridyl)ethyl]pyridine (PY5Me2). Exposure of [V(II)(NCCH3)(PY5Me2)](2+) (1) to either dioxygen or selected O-atom-transfer reagents yields [V(IV)(O)(PY5Me2)](2+) (2). The metal-centered one-electron reduction of this vanadium(IV) oxo complex furnishes a stable, diamagnetic [V(III)(O)(PY5Me2)](+) (3) species. The vanadium(III) oxo species is unreactive toward H- and O-atom transfer but readily reacts with protons to form a putative vanadium hydroxo complex. Computational results predict that further one-electron reduction of the vanadium(III) oxo species will result in ligand-based reduction, even though pyridine is generally considered to be a poor π-accepting ligand. These results have implications for future efforts toward low-valent vanadyl chemistry, particularly with regard to the isolation and study of formal vanadium(II) oxo species.

Antagonizing STAT3 dimerization with a rhodium(III) complex.

PubMed

Ma, Dik-Lung; Liu, Li-Juan; Leung, Ka-Ho; Chen, Yen-Ting; Zhong, Hai-Jing; Chan, Daniel Shiu-Hin; Wang, Hui-Min David; Leung, Chung-Hang

2014-08-25

Kinetically inert metal complexes have arisen as promising alternatives to existing platinum and ruthenium chemotherapeutics. Reported herein, to our knowledge, is the first example of a substitutionally inert, Group 9 organometallic compound as a direct inhibitor of signal transducer and activator of transcription 3 (STAT3) dimerization. From a series of cyclometalated rhodium(III) and iridium(III) complexes, a rhodium(III) complex emerged as a potent inhibitor of STAT3 that targeted the SH2 domain and inhibited STAT3 phosphorylation and dimerization. Significantly, the complex exhibited potent anti-tumor activities in an in vivo mouse xenograft model of melanoma. This study demonstrates that rhodium complexes may be developed as effective STAT3 inhibitors with potent anti-tumor activity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analysis of gold(I/III)-complexes by HPLC-ICP-MS demonstrates gold(III) stability in surface waters.

PubMed

Ta, Christine; Reith, Frank; Brugger, Joël; Pring, Allan; Lenehan, Claire E

2014-05-20

Understanding the form in which gold is transported in surface- and groundwaters underpins our understanding of gold dispersion and (bio)geochemical cycling. Yet, to date, there are no direct techniques capable of identifying the oxidation state and complexation of gold in natural waters. We present a reversed phase ion-pairing HPLC-ICP-MS method for the separation and determination of aqueous gold(III)-chloro-hydroxyl, gold(III)-bromo-hydroxyl, gold(I)-thiosulfate, and gold(I)-cyanide complexes. Detection limits for the gold species range from 0.05 to 0.30 μg L(-1). The [Au(CN)2](-) gold cyanide complex was detected in five of six waters from tailings and adjacent monitoring bores of working gold mines. Contrary to thermodynamic predictions, evidence was obtained for the existence of Au(III)-complexes in circumneutral, hypersaline waters of a natural lake overlying a gold deposit in Western Australia. This first direct evidence for the existence and stability of Au(III)-complexes in natural surface waters suggests that Au(III)-complexes may be important for the transport and biogeochemical cycling of gold in surface environments. Overall, these results show that near-μg L(-1) enrichments of Au in environmental waters result from metastable ligands (e.g., CN(-)) as well as kinetically controlled redox processes leading to the stability of highly soluble Au(III)-complexes.

Oxidative Formation and Removal of Complexed Mn(III) by Pseudomonas Species

PubMed Central

Wright, Mitchell H.; Geszvain, Kati; Oldham, Véronique E.; Luther, George W.; Tebo, Bradley M.

2018-01-01

The observation of significant concentrations of soluble Mn(III) complexes in oxic, suboxic, and some anoxic waters has triggered a re-evaluation of the previous Mn paradigm which focused on the cycling between soluble Mn(II) and insoluble Mn(III,IV) species as operationally defined by filtration. Though Mn(II) oxidation in aquatic environments is primarily bacterially-mediated, little is known about the effect of Mn(III)-binding ligands on Mn(II) oxidation nor on the formation and removal of Mn(III). Pseudomonas putida GB-1 is one of the most extensively investigated of all Mn(II) oxidizing bacteria, encoding genes for three Mn oxidases (McoA, MnxG, and MopA). P. putida GB-1 and associated Mn oxidase mutants were tested alongside environmental isolates Pseudomonas hunanensis GSL-007 and Pseudomonas sp. GSL-010 for their ability to both directly oxidize weakly and strongly bound Mn(III), and to form these complexes through the oxidation of Mn(II). Using Mn(III)-citrate (weak complex) and Mn(III)-DFOB (strong complex), it was observed that P. putida GB-1, P. hunanensis GSL-007 and Pseudomonas sp. GSL-010 and mutants expressing only MnxG and McoA were able to directly oxidize both species at varying levels; however, no oxidation was detected in cultures of a P. putida mutant expressing only MopA. During cultivation in the presence of Mn(II) and citrate or DFOB, P. putida GB-1, P. hunanensis GSL-007 and Pseudomonas sp. GSL-010 formed Mn(III) complexes transiently as an intermediate before forming Mn(III/IV) oxides with the overall rates and extents of Mn(III,IV) oxide formation being greater for Mn(III)-citrate than for Mn(III)-DFOB. These data highlight the role of bacteria in the oxidative portion of the Mn cycle and suggest that the oxidation of strong Mn(III) complexes can occur through enzymatic mechanisms involving multicopper oxidases. The results support the observations from field studies and further emphasize the complexity of the geochemical cycling of

Oxidative Formation and Removal of Complexed Mn(III) by Pseudomonas Species.

PubMed

Wright, Mitchell H; Geszvain, Kati; Oldham, Véronique E; Luther, George W; Tebo, Bradley M

2018-01-01

The observation of significant concentrations of soluble Mn(III) complexes in oxic, suboxic, and some anoxic waters has triggered a re-evaluation of the previous Mn paradigm which focused on the cycling between soluble Mn(II) and insoluble Mn(III,IV) species as operationally defined by filtration. Though Mn(II) oxidation in aquatic environments is primarily bacterially-mediated, little is known about the effect of Mn(III)-binding ligands on Mn(II) oxidation nor on the formation and removal of Mn(III). Pseudomonas putida GB-1 is one of the most extensively investigated of all Mn(II) oxidizing bacteria, encoding genes for three Mn oxidases (McoA, MnxG, and MopA). P. putida GB-1 and associated Mn oxidase mutants were tested alongside environmental isolates Pseudomonas hunanensis GSL-007 and Pseudomonas sp. GSL-010 for their ability to both directly oxidize weakly and strongly bound Mn(III), and to form these complexes through the oxidation of Mn(II). Using Mn(III)-citrate (weak complex) and Mn(III)-DFOB (strong complex), it was observed that P. putida GB-1, P. hunanensis GSL-007 and Pseudomonas sp. GSL-010 and mutants expressing only MnxG and McoA were able to directly oxidize both species at varying levels; however, no oxidation was detected in cultures of a P. putida mutant expressing only MopA. During cultivation in the presence of Mn(II) and citrate or DFOB, P. putida GB-1, P. hunanensis GSL-007 and Pseudomonas sp. GSL-010 formed Mn(III) complexes transiently as an intermediate before forming Mn(III/IV) oxides with the overall rates and extents of Mn(III,IV) oxide formation being greater for Mn(III)-citrate than for Mn(III)-DFOB. These data highlight the role of bacteria in the oxidative portion of the Mn cycle and suggest that the oxidation of strong Mn(III) complexes can occur through enzymatic mechanisms involving multicopper oxidases. The results support the observations from field studies and further emphasize the complexity of the geochemical cycling of

Mitochondrial respiratory chain complexes as sources and targets of thiol-based redox-regulation.

PubMed

Dröse, Stefan; Brandt, Ulrich; Wittig, Ilka

2014-08-01

The respiratory chain of the inner mitochondrial membrane is a unique assembly of protein complexes that transfers the electrons of reducing equivalents extracted from foodstuff to molecular oxygen to generate a proton-motive force as the primary energy source for cellular ATP-synthesis. Recent evidence indicates that redox reactions are also involved in regulating mitochondrial function via redox-modification of specific cysteine-thiol groups in subunits of respiratory chain complexes. Vice versa the generation of reactive oxygen species (ROS) by respiratory chain complexes may have an impact on the mitochondrial redox balance through reversible and irreversible thiol-modification of specific target proteins involved in redox signaling, but also pathophysiological processes. Recent evidence indicates that thiol-based redox regulation of the respiratory chain activity and especially S-nitrosylation of complex I could be a strategy to prevent elevated ROS production, oxidative damage and tissue necrosis during ischemia-reperfusion injury. This review focuses on the thiol-based redox processes involving the respiratory chain as a source as well as a target, including a general overview on mitochondria as highly compartmentalized redox organelles and on methods to investigate the redox state of mitochondrial proteins. This article is part of a Special Issue entitled: Thiol-Based Redox Processes. Copyright © 2014 Elsevier B.V. All rights reserved.

Molecular structure and biological studies on Cr(III), Mn(II) and Fe(III) complexes of heterocyclic carbohydrazone ligand.

PubMed

Abu El-Reash, G M; El-Gammal, O A; Radwan, A H

2014-01-01

The chelating behavior of the ligand (H2APC) based on carbohydrazone core modified with pyridine end towards Cr(III), Mn(II) and Fe(III) ions have been examined. The (1)H NMR and IR data for H2APC revealed the presence of two stereoisomers syn and anti in both solid state and in solution in addition to the tautomeric versatility based on the flexible nature of the hydrazone linkage leading to varied coordination modes. The spectroscopic data confirmed that the ligand behaves as a monobasic tridentate in Cr(III) and Fe(III) complexes and as neutral tetradentate in Mn(II) complex. The electronic spectra as well as the magnetic measurements confirmed the octahedral geometry for all complexes. The bond length and angles were evaluated by DFT method using material studio program for all complexes. The thermal behavior and the kinetic parameters of degradation were determined using Coats-Redfern and Horowitz-Metzger methods. The antioxidant (DDPH and ABTS methods), anti-hemolytic and cytotoxic activities of the compounds have been screened. Cr(III) complex and H2APC showed the highest antioxidant activity using ABTS and DPPH methods. With respect to in vitro Ehrlich ascites assay, H2APC exhibited the potent activity followed by Fe(III) and Cr(III)complexes. Copyright © 2013 Elsevier B.V. All rights reserved.

Respiratory Complex I in Bos taurus and Paracoccus denitrificans Pumps Four Protons across the Membrane for Every NADH Oxidized.

PubMed

Jones, Andrew J Y; Blaza, James N; Varghese, Febin; Hirst, Judy

2017-03-24

Respiratory complex I couples electron transfer between NADH and ubiquinone to proton translocation across an energy-transducing membrane to support the proton-motive force that drives ATP synthesis. The proton-pumping stoichiometry of complex I ( i.e. the number of protons pumped for each two electrons transferred) underpins all mechanistic proposals. However, it remains controversial and has not been determined for any of the bacterial enzymes that are exploited as model systems for the mammalian enzyme. Here, we describe a simple method for determining the proton-pumping stoichiometry of complex I in inverted membrane vesicles under steady-state ADP-phosphorylating conditions. Our method exploits the rate of ATP synthesis, driven by oxidation of NADH or succinate with different sections of the respiratory chain engaged in catalysis as a proxy for the rate of proton translocation and determines the stoichiometry of complex I by reference to the known stoichiometries of complexes III and IV. Using vesicles prepared from mammalian mitochondria (from Bos taurus ) and from the bacterium Paracoccus denitrificans , we show that four protons are pumped for every two electrons transferred in both cases. By confirming the four-proton stoichiometry for mammalian complex I and, for the first time, demonstrating the same value for a bacterial complex, we establish the utility of P. denitrificans complex I as a model system for the mammalian enzyme. P. denitrificans is the first system described in which mutagenesis in any complex I core subunit may be combined with quantitative proton-pumping measurements for mechanistic studies. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

A binuclear Mn(III) complex of a scorpiand-like ligand displaying a single unsupported Mn(III)-O-Mn(III) bridge.

PubMed

Blasco, Salvador; Cano, Joan; Clares, M Paz; García-Granda, Santiago; Doménech, Antonio; Jiménez, Hermas R; Verdejo, Begoña; Lloret, Francesc; García-España, Enrique

2012-11-05

The crystal structure of a binuclear Mn(III) complex of a scorpiand-like ligand (L) displays an unsupported single oxo bridging ligand with a Mn(III)-O-Mn(III) angle of 174.7°. Magnetic susceptibility measurements indicate strong antiferromagnetic coupling between the two metal centers. DFT calculations have been carried out to understand the magnetic behavior and to analyze the nature of the observed Jahn-Teller distortion. Paramagnetic (1)H NMR has been applied to rationalize the formation and magnetic features of the complexes formed in solution.

Is there a genetic solution to bovine respiratory disease complex?

USDA-ARS?s Scientific Manuscript database

Bovine respiratory disease complex (BRDC) is a complex multi-factor disease, which increases costs and reduces revenue from feedlot cattle. Multiple stressors and pathogens (viral and bacterial) have been implicated in the etiology of BRDC, therefore multiple approaches will be needed to evaluate a...

Reactivity of a Cobalt(III)–Hydroperoxo Complex in Electrophilic Reactions

DOE PAGES

Shin, Bongki; Sutherlin, Kyle D.; Ohta, Takehiro; ...

2016-11-15

The reactivity of mononuclear metal-hydroperoxo adducts has fascinated researchers in many areas due to their diverse biological and catalytic processes. In this study, a mononuclear cobalt(III)-peroxo complex bearing a tetradentate macrocyclic ligand, [Co III(Me 3-TPADP)(O 2)] + (Me 3-TPADP = 3,6,9-trimethyl-3,6,9-triaza-1(2,6)-pyridinacyclodecaphane), was prepared by reacting [Co II(Me 3-TPADP)(CH 3CN) 2] 2+ with H 2O 2 in the presence of triethylamine. Upon protonation, the cobalt(III)- peroxo intermediate was converted into a cobalt(III)-hydroperoxo complex, [Co III(Me 3-TPADP)(O 2H)(CH 3CN)] 2+. The mononuclear cobalt(III)-peroxo and -hydroperoxo intermediates were characterized by a variety of physicochemical methods. Results of electrospray ionization mass spectrometry clearly showmore » the transformation of the intermediates: the peak at m/z 339.2 assignable to the cobalt(III)-peroxo species disappears with concomitant growth of the peak at m/z 190.7 corresponding to the cobalt(III)-hydroperoxo complex (with bound CH 3CN). Isotope labeling experiments further support the existence of the cobalt(III)-peroxo and -hydroperoxo complexes. In particular, the O-O bond stretching frequency of the cobalt(III)-hydroperoxo complex was determined to be 851 cm -1 for 16O 2H samples (803 cm -1 for 18O 2H samples) and its Co-O vibrational energy was observed at 571 cm -1 for 16O 2H samples (551 cm -1 for 18O 2H samples; 568 cm -1 for 16O 2 2H samples) by resonance Raman spectroscopy. Reactivity studies performed with the cobalt(III)-peroxo and -hydroperoxo complexes in organic functionalizations reveal that the latter is capable of conducting oxygen atom transfer with an electrophilic character, whereas the former exhibits no oxygen atom transfer reactivity under the same reaction conditions. Alternatively, the cobalt(III)-hydroperoxo complex does not perform hydrogen atom transfer reactions, while analogous low-spin Fe(III)-hydroperoxo complexes are capable of this

Reactivity of a Cobalt(III)–Hydroperoxo Complex in Electrophilic Reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, Bongki; Sutherlin, Kyle D.; Ohta, Takehiro

The reactivity of mononuclear metal-hydroperoxo adducts has fascinated researchers in many areas due to their diverse biological and catalytic processes. In this study, a mononuclear cobalt(III)-peroxo complex bearing a tetradentate macrocyclic ligand, [Co III(Me 3-TPADP)(O 2)] + (Me 3-TPADP = 3,6,9-trimethyl-3,6,9-triaza-1(2,6)-pyridinacyclodecaphane), was prepared by reacting [Co II(Me 3-TPADP)(CH 3CN) 2] 2+ with H 2O 2 in the presence of triethylamine. Upon protonation, the cobalt(III)- peroxo intermediate was converted into a cobalt(III)-hydroperoxo complex, [Co III(Me 3-TPADP)(O 2H)(CH 3CN)] 2+. The mononuclear cobalt(III)-peroxo and -hydroperoxo intermediates were characterized by a variety of physicochemical methods. Results of electrospray ionization mass spectrometry clearly showmore » the transformation of the intermediates: the peak at m/z 339.2 assignable to the cobalt(III)-peroxo species disappears with concomitant growth of the peak at m/z 190.7 corresponding to the cobalt(III)-hydroperoxo complex (with bound CH 3CN). Isotope labeling experiments further support the existence of the cobalt(III)-peroxo and -hydroperoxo complexes. In particular, the O-O bond stretching frequency of the cobalt(III)-hydroperoxo complex was determined to be 851 cm -1 for 16O 2H samples (803 cm -1 for 18O 2H samples) and its Co-O vibrational energy was observed at 571 cm -1 for 16O 2H samples (551 cm -1 for 18O 2H samples; 568 cm -1 for 16O 2 2H samples) by resonance Raman spectroscopy. Reactivity studies performed with the cobalt(III)-peroxo and -hydroperoxo complexes in organic functionalizations reveal that the latter is capable of conducting oxygen atom transfer with an electrophilic character, whereas the former exhibits no oxygen atom transfer reactivity under the same reaction conditions. Alternatively, the cobalt(III)-hydroperoxo complex does not perform hydrogen atom transfer reactions, while analogous low-spin Fe(III)-hydroperoxo complexes are capable of this

Development of a C3-symmetric benzohydroxamate tripod: Trimetallic complexation with Fe(III), Cr(III) and Al(III)

NASA Astrophysics Data System (ADS)

Baral, Minati; Gupta, Amit; Kanungo, B. K.

2016-06-01

The design, synthesis and physicochemical characterization of a C3-symmetry Benzene-1,3,5-tricarbonylhydroxamate tripod, noted here as BTHA, are described. The chelator was built from a benzene as an anchor, symmetrically extended by three hydroxamate as ligating moieties, each bearing O, O donor sites. A combination of absorption spectrophotometry, potentiometry and theoretical investigations are used to explore the complexation behavior of the ligand with some trivalent metal ions: Fe(III), Cr(III), and Al(III). Three protonation constants were calculated for the ligand in a pH range of 2-11 in a highly aqueous medium (9:1 H2O: DMSO). A high rigidity in the molecular structure restricts the formation of 1:1 (M/L) metal encapsulation but shows a high binding efficiency for a 3:1 metal ligand stoichiometry giving formation constant (in β unit) 28.73, 26.13 and 19.69 for [M3L]; Mdbnd Fe(III), Al(III) and Cr(III) respectively, and may be considered as an efficient Fe-carrier. The spectrophotometric study reveals of interesting electronic transitions occurred during the complexation. BTHA exhibits a peak at 238 nm in acidic pH and with the increase of pH, a new peak appeared at 270 nm. A substantial shifting in both of the peaks in presence of the metal ions implicates a s coordination between ligand and metal ions. Moreover, complexation of BTHA with iron shows three distinct colors, violet, reddish orange and yellow in different pH, enables the ligand to be considered for the use as colorimetric sensor.

Complexation of Nd(III) with tetraborate ion and its effect on actinide (III) solubility in WIPP brine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borkowski, Marian; Richmann, Michael K; Reed, Donald T

2010-01-01

The potential importance of tetraborate complexation on lanthanide(III) and actinide(III) solubility is recognized in the literature but a systematic study of f-element complexation has not been performed. In neodymium solubility studies in WIPP brines, the carbonate complexation effect is not observed since tetraborate ions form a moderately strong complex with neodymium(III). The existence of these tetraborate complexes was established for low and high ionic strength solutions. Changes in neodymium(III) concentrations in undersaturation experiments were used to determine the neodymium with tetraborate stability constants as a function of NaCl ionic strength. As very low Nd(III) concentrations have to be measured, itmore » was necessary to use an extraction pre-concentration step combined with ICP-MS analysis to extend the detection limit by a factor of 50. The determined Nd(III) with borate stability constants at infinite dilution and 25 C are equal to log {beta}{sub 1} = 4.55 {+-} 0.06 using the SIT approach, equal to log {beta}{sub 1} = 4.99 {+-} 0.30 using the Pitzer approach, with an apparent log {beta}{sub 1} = 4.06 {+-} 0.15 (in molal units) at I = 5.6 m NaCl. Pitzer ion-interaction parameters for neodymium with tetraborate and SIT interaction coefficients were also determined and reported.« less

Control of electron transport routes through redox-regulated redistribution of respiratory complexes

PubMed Central

Liu, Lu-Ning; Bryan, Samantha J.; Huang, Fang; Yu, Jianfeng; Nixon, Peter J.; Rich, Peter R.; Mullineaux, Conrad W.

2012-01-01

In cyanobacteria, respiratory electron transport takes place in close proximity to photosynthetic electron transport, because the complexes required for both processes are located within the thylakoid membranes. The balance of electron transport routes is crucial for cell physiology, yet the factors that control the predominance of particular pathways are poorly understood. Here we use a combination of tagging with green fluorescent protein and confocal fluorescence microscopy in live cells of the cyanobacterium Synechococcus elongatus PCC 7942 to investigate the distribution on submicron scales of two key respiratory electron donors, type-I NAD(P)H dehydrogenase (NDH-1) and succinate dehydrogenase (SDH). When cells are grown under low light, both complexes are concentrated in discrete patches in the thylakoid membranes, about 100–300 nm in diameter and containing tens to hundreds of complexes. Exposure to moderate light leads to redistribution of both NDH-1 and SDH such that they become evenly distributed within the thylakoid membranes. The effects of electron transport inhibitors indicate that redistribution of respiratory complexes is triggered by changes in the redox state of an electron carrier close to plastoquinone. Redistribution does not depend on de novo protein synthesis, and it is accompanied by a major increase in the probability that respiratory electrons are transferred to photosystem I rather than to a terminal oxidase. These results indicate that the distribution of complexes on the scale of 100–300 nm controls the partitioning of reducing power and that redistribution of electron transport complexes on these scales is a physiological mechanism to regulate the pathways of electron flow. PMID:22733774

Luminescence of europium (III) complexes for visualization

NASA Astrophysics Data System (ADS)

Kolontaeva, Olga A.; Pozharov, Mikhail V.; Korolovich, Vladimir F.; Khokhlova, Anastasia R.; Kirdyanova, Anna N.; Burmistrova, Natalia A.; Zakharova, Tamara V.; Goryacheva, Irina Y.

2016-04-01

With the purpose to develop bright non-toxic luminescent label for theranostic application we have studied complexation of lanthanide dipicolinates (2,6-pyridinedicarboxylates) by sodium alginate and effect of thermal exposure of synthesized micro-capsules on their luminescent properties. Synthesized micro-capsules are stable in acidic medium but dissolve at pH ~ 4 due to transformation of cationic europium dipicolinate complex to anionic. Luminescence studies have shown that emission spectra of europium(III)-alginate complexes (both chloride and dipicolinate) contain two intensive bands characteristic to Eu3+ ion (5D0 --> 7F1 (590 nm) and 5D0 --> 7F1 (612 nm)). We have also found that at 160ºC europium(III)- alginate micro-capsules decompose to black, soot-like substance, therefore, their thermal treatment must be performed in closed environment (i.e., sealed ampoules).

Lanthanoplatins: emissive Eu(iii) and Tb(iii) complexes staining nucleoli targeted through Pt-DNA crosslinking.

PubMed

Singh, Khushbu; Singh, Swati; Srivastava, Payal; Sivakumar, Sri; Patra, Ashis K

2017-06-01

Two highly luminescent water-soluble heterometallic LnPt 2 complexes, [{cis-PtCl(NH 3 ) 2 } 2 Ln(L)(H 2 O)](NO 3 ) 2 (Ln = Eu (1), Tb (2)), have been designed for their selective nucleoli staining through formation of Pt-DNA crosslinks. The complexes showed significant cellular uptake and distinctive nucleoli localization through intrinsic emission from Eu III or Tb III observed through confocal fluorescence microscopy.

Synthesis, structure, and magnetic characterization of a C3-symmetric Mn(III)3Cr(III) assembly: molecular recognition between a trinuclear Mn(III) triplesalen complex and a fac-triscyano Cr(III) complex.

PubMed

Freiherr von Richthofen, Carl-Georg; Stammler, Anja; Bögge, Hartmut; DeGroot, Marty W; Long, Jeffrey R; Glaser, Thorsten

2009-11-02

The reaction of the tris(tetradentate) triplesalen ligand H(6)talen(t-Bu(2)), which provides three salen-like coordination environments bridged in a meta-phenylene arrangement by a phloroglucinol backbone, with Mn(II) salts under aerobic conditions, affords, in situ, the trinuclear Mn(III) triplesalen complex [(talen(t-Bu(2))){Mn(III)(solv)(n)}(3)](3+). This species then reacts with [(Me(3)tacn)Cr(CN)(3)] to form the tetranuclear complex [{(talen(t-Bu(2)))Mn(III)(3)}{(Me(3)tacn)Cr(CN)(3)}](3+) ([Mn(III)(3)Cr(III)](3+)). The regular ligand folding observed in the trinuclear triplesalen complex preorganizes the three metal ions for the reaction with three facially coordinated nitrogen atoms of [(Me(3)tacn)Cr(CN)(3)]. [{(talen(t-Bu(2)))(Mn(III)(MeOH))(3)}{(Me(3)tacn)Cr(CN)(3)}](ClO(4))(3) (1) was characterized by infrared spectroscopy, elemental analysis, mass spectrometry, electron absorption spectroscopy, and magnetic measurements. The molecular structure was established for the acetate-substituted derivative [{(talen(t-Bu(2)))(Mn(III)(MeOH))(2)(Mn(III)(OAc))}{(Me(3)tacn)Cr(CN)(3)}](ClO(4))(2) (2) by single-crystal X-ray diffraction. Variable-temperature-variable-field and mu(eff) versus T magnetic data have been analyzed in detail by full-matrix diagonalization of the appropriate spin-Hamiltonian, consisting of isotropic exchange, zero-field splitting, and Zeeman interaction components. Satisfactory reproduction of the experimental data has been obtained for the parameters J(Mn-Cr) = -0.12 +/- 0.04 cm(-1), J(Mn-Mn) = -0.70 +/- 0.03 cm(-1), and D(Mn) = -3.0 +/- 0.4 cm(-1). These generate a triply degenerate pseudo S(t) = 7/2 spin manifold, which cannot be appropriately described by a giant spin model and which exhibits a weak easy-axis magnetic anisotropy. This is corroborated by the onset of a frequency-dependent chi'' signal at low temperatures, demonstrating a slow relaxation of the magnetization indicative of 1 being a single-molecule magnet. Comparing the

Synthesis and spectroscopic studies of biologically active compounds derived from oxalyldihydrazide and benzil, and their Cr(III), Fe(III) and Mn(III) complexes.

PubMed

Singh, D P; Kumar, Ramesh; Singh, Jitender

2009-04-01

A new series of complexes have been synthesized by template condensation of oxalyldihydrazide and benzil in methanolic medium in the presence of trivalent chromium, manganese and iron salts forming complexes of the type [M(C(32)H(24)N(8)O(4))X]X(2) where M = Cr(III), Mn(III), Fe(III) and X = Cl(-1), NO(3)(-1), CH(3)COO(-1). The complexes have been characterized with the help of elemental analyses, conductance measurements, magnetic susceptibility measurements, electronic, NMR, infrared and far infrared spectral studies. On the basis of these studies, a five coordinate square pyramidal geometry has been proposed for all these complexes. The biological activities of the metal complexes have been tested in vitro against a number of pathogenic bacteria to assess their inhibiting potential. Some of these complexes have been found to exhibit remarkable antibacterial activities.

A Paramagnetic Copper(III) Complex Containing an Octahedral CuIII S6 Coordination Polyhedron.

PubMed

Krebs, Carsten; Glaser, Thorsten; Bill, Eckhard; Weyhermüller, Thomas; Meyer-Klaucke, Wolfram; Wieghardt, Karl

1999-02-01

Only the second octahedral, paramagnetic copper(III) complex (S=1) has now been synthesized and characterized. Six thiolato bridging ligands in the heterotrinuclear species [LCo III Cu III Co III L](ClO 4 ) 3 ⋅2 Me 2 CO (L=1,4,7-tris(4-tert-butyl-2-sulfidobenzyl)-1,4,7-triazacyclononane) stabilize this rare electron configuration. A section of the structure of the reduced form (Cu II , S=½) is shown. XAS, EXAFS, and EPR spectroscopy prove unambiguously that the one-electron oxidation to the copper(III) is metal- rather than ligand-centered. © 1999 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.

Dissolution of Fe(III) (hydr) oxides by metal-EDTA complexes

NASA Astrophysics Data System (ADS)

Ngwack, Bernd; Sigg, Laura

1997-03-01

The dissolution of Fe(III)(hydr)oxides (goethite and hydrous ferric oxide) by metal-EDTA complexes occurs by ligand-promoted dissolution. The process is initiated by the adsorption of metal-EDTA complexes to the surface and is followed by the dissociation of the complex at the surface and the release of Fe(III)EDTA into solution. The dissolution rate is decreased to a great extent if EDTA is complexed by metals in comparison to the uncomplexed EDTA. The rate decreases in the order EDTA CaEDTA ≫ PbEDTA > ZnEDTA > CuEDTA > Co(II)EDTA > NiEDTA. Two different rate-limiting steps determine the dissolution process: (1) detachment of Fe(III) from the oxide-structure and (2) dissociation of the metal-EDTA complexes. In the case of goethite, step 1 is slower than step 2 and the dissolution rates by various metals are similar. In the case of hydrous ferric oxide, step 2 is rate-limiting and the effect of the complexed metal is very pronounced.

Structure and reactivity of a mononuclear non-haem iron(III)–peroxo complex

PubMed Central

Cho, Jaeheung; Jeon, Sujin; Wilson, Samuel A.; Liu, Lei V.; Kang, Eun A; Braymer, Joseph J.; Lim, Mi Hee; Hedman, Britt; Hodgson, Keith O.; Valentine, Joan Selverstone; Solomon, Edward I.; Nam, Wonwoo

2012-01-01

Oxygen-containing mononuclear iron species—iron(III)–peroxo, iron(III)–hydroperoxo and iron(IV)–oxo—are key intermediates in the catalytic activation of dioxygen by iron-containing metalloenzymes1–7. It has been difficult to generate synthetic analogues of these three active iron–oxygen species in identical host complexes, which is necessary to elucidate changes to the structure of the iron centre during catalysis and the factors that control their chemical reactivities with substrates. Here we report the high-resolution crystal structure of a mononuclear non-haem side-on iron(III)–peroxo complex, [Fe(III)(TMC)(OO)]+. We also report a series of chemical reactions in which this iron(III)–peroxo complex is cleanly converted to the iron(III)–hydroperoxo complex, [Fe(III)(TMC)(OOH)]2+, via a short-lived intermediate on protonation. This iron(III)–hydroperoxo complex then cleanly converts to the ferryl complex, [Fe(IV)(TMC)(O)]2+, via homolytic O–O bond cleavage of the iron(III)–hydroperoxo species. All three of these iron species—the three most biologically relevant iron–oxygen intermediates—have been spectroscopically characterized; we note that they have been obtained using a simple macrocyclic ligand. We have performed relative reactivity studies on these three iron species which reveal that the iron(III)–hydroperoxo complex is the most reactive of the three in the deformylation of aldehydes and that it has a similar reactivity to the iron(IV)–oxo complex in C–H bond activation of alkylaromatics. These reactivity results demonstrate that iron(III)–hydroperoxo species are viable oxidants in both nucleophilic and electrophilic reactions by iron-containing enzymes. PMID:22031443

Crystallization of Mitochondrial Respiratory Complex II from Chicken Heart: a Membrane Protein Complex Diffracting to 2.0 Å.

PubMed Central

Huang, Li-shar; Borders, Toni M.; Shen, John T.; Wang, Chung-Jen; Berry, Edward

2006-01-01

Synopsis A multi-subunit mitochondrial membrane protein complex involved in the Krebs Cycle and respiratory chain has been crystallized in a form suitable for near-atomic resolution structure determination. A procedure is presented for preparation of diffraction-quality crystals of a vertebrate mitochondrial respiratory Complex II. The crystals have the potential to diffract to at least 2.0 Å with optimization of post-crystal-growth treatment and cryoprotection. This should allow determination of the structure of this important and medically relevant membrane protein complex at near-atomic resolution and provide great detail of the mode of binding of substrates and inhibitors at the two substrate-binding sites. PMID:15805592

TRLFS study on the complexation of Cm(III) and Eu(III) with SO3-Ph-BTBP.

PubMed

Wagner, Christoph; Müllich, Udo; Geist, Andreas; Panak, Petra J

2015-10-21

The complexation of Cm(iii) and Eu(iii) with a water soluble BTBP (sodium 3,3',3'',3'''-([2,2'-bipyridine]-6,6'-diylbis(1,2,4-triazine-3,5,6-triyl))tetrabenzenesulfonate, SO3-Ph-BTBP) is studied using time resolved laser fluorescence spectroscopy. For the complexation of Cm(iii) the influence of the medium (10(-3) M HClO4→ 0.5 M HNO3) is investigated in detail revealing important impacts of the applied medium (pH, ionic strength, anions) on the speciation and conditional stability constants. SO3-Ph-BTBP forms 1 : 2 complexes with Cm(iii) and Eu(iii). The conditional stability constants of [Cm(SO3-Ph-BTBP)2](5-) and [Eu(SO3-Ph-BTBP)2](5-) in 0.5 M HNO3 are determined to be log β02 = 7.3 ± 0.3 and log β02 = 5.4 ± 0.5, respectively. The difference of 1.9 orders of magnitude is in line with hydrophobic BT(B)P type ligands and shows that the selectivity is not affected by tuning the hydrophilicity using SO3-Ph-side chains.

Respiratory chain complex II as general sensor for apoptosis.

PubMed

Grimm, Stefan

2013-05-01

I review here the evidence that complex II of the respiratory chain (RC) constitutes a general sensor for apoptosis induction. This concept emerged from work on neurodegenerative diseases and from recent data on metabolic alterations in cancer cells affecting the RC and in particular on mutations of complex II subunits. It is also supported by experiments with many anticancer compounds that compared the apoptosis sensitivities of complex II-deficient versus WT cells. These results are explained by the mechanistic understanding of how complex II mediates the diverse range of apoptosis signals. This protein aggregate is specifically activated for apoptosis by pH change as a common and early feature of dying cells. This leads to the dissociation of its SDHA and SDHB subunits from the remaining membrane-anchored subunits and the consequent block of it enzymatic SQR activity, while its SDH activity, which is contained in the SDHA/SDHB subcomplex, remains intact. The uncontrolled SDH activity then generates excessive amounts of reactive oxygen species for the demise of the cell. Future studies on these mitochondrial processes will help refine this model, unravel the contribution of mutations in complex II subunits as the cause of degenerative neurological diseases and tumorigenesis, and aid in discovering novel interference options. This article is part of a Special Issue entitled: Respiratory complex II: Role in cellular physiology and disease. Copyright © 2012 Elsevier B.V. All rights reserved.

On the structure and spin states of Fe(III)-EDDHA complexes.

PubMed

Gómez-Gallego, Mar; Fernández, Israel; Pellico, Daniel; Gutiérrez, Angel; Sierra, Miguel A; Lucena, Juan J

2006-07-10

DFT methods are suitable for predicting both the geometries and spin states of EDDHA-Fe(III) complexes. Thus, extensive DFT computational studies have shown that the racemic-Fe(III) EDDHA complex is more stable than the meso isomer, regardless of the spin state of the central iron atom. A comparison of the energy values obtained for the complexes under study has also shown that high-spin (S = 5/2) complexes are more stable than low-spin (S = 1/2) ones. These computational results matched the experimental results of the magnetic susceptibility values of both isomers. In both cases, their behavior has been fitted as being due to isolated high-spin Fe(III) in a distorted octahedral environment. The study of the correlation diagram also confirms the high-spin iron in complex 2b. The geometry optimization of these complexes performed with the standard 3-21G* basis set for hydrogen, carbon, oxygen, and nitrogen and the Hay-Wadt small-core effective core potential (ECP) including a double-xi valence basis set for iron, followed by single-point energy refinement with the 6-31G* basis set, is suitable for predicting both the geometries and the spin-states of EDDHA-Fe(III) complexes. The presence of a high-spin iron in Fe(III)-EDDHA complexes could be the key to understanding their lack of reactivity in electron-transfer processes, either chemically or electrochemically induced, and their resistance to photodegradation.

Steric Effect on the Nucleophilic Reactivity of Nickel(III) Peroxo Complexes.

PubMed

Kim, Jalee; Shin, Bongki; Kim, Hyunjeong; Lee, Junhyung; Kang, Joongoo; Yanagisawa, Sachiko; Ogura, Takashi; Masuda, Hideki; Ozawa, Tomohiro; Cho, Jaeheung

2015-07-06

A set of nickel(III) peroxo complexes bearing tetraazamacrocyclic ligands, [Ni(III)(TBDAP)(O2)](+) (TBDAP = N,N'-di-tert-butyl-2,11-diaza[3.3](2,6)pyridinophane) and [Ni(III)(CHDAP)(O2)](+) (CHDAP = N,N'-dicyclohexyl-2,11-diaza[3.3](2,6)pyridinophane), were prepared by reacting [Ni(II)(TBDAP)(NO3)(H2O)](+) and [Ni(II)(CHDAP)(NO3)](+), respectively, with H2O2 in the presence of triethylamine. The mononuclear nickel(III) peroxo complexes were fully characterized by various physicochemical methods, such as UV-vis, electrospray ionization mass spectrometry, resonance Raman, electron paramagnetic resonance, and X-ray analysis. The spectroscopic and structural characterization clearly shows that the NiO2 cores are almost identical where the peroxo ligand is bound in a side-on fashion. However, the different steric properties of the supporting ligands were confirmed by X-ray crystallography, where the CHDAP ligand gives enough space around the Ni core compared to the TBDAP ligand. The nickel(III) peroxo complexes showed reactivity in the oxidation of aldehydes. In the aldehyde deformylation reaction, the nucleophilic reactivity of the nickel(III) peroxo complexes was highly dependent on the steric properties of the macrocyclic ligands, with a reactivity order of [Ni(III)(TBDAP)(O2)](+) < [Ni(III)(CHDAP)(O2)](+). This result provides fundamental insight into the mechanism of the structure (steric)-reactivity relationship of metal peroxo intermediates.

Synthesis and physico-chemical studies on neodymium(III) and samarium(III) complexes with tetraaza macrocyclic ligands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goel, S.; Pandey, U.K.; Pandey, O.P.

1988-05-01

Reactions of neodymium trichloride and samarium trichloride with 6,7,13,14-R/sub 4/ - 3,10-X/sub 2/-(14)-5,7,12,14-tetraene-1,5,8,12-N/sub 4/-(2,4,9,11-N/sub 4/) (R = CH/sub 3/, X = 0 (L/sub 1//sup (1)/); R = C/sub 6/H/sub 5/, X = O (L/sub 1//sup (2)/); R = CH/sub 3/, X = S(L/sub 2//sup (1)/)) and R = C/sub 6/H/sub 5/, X = S(/sub 2//sup (2)/)) have been studied in ethanol and complexes of the type (M(L/sub 1//sup (1)/ or L/sub 1//sup (2)/))Cl/sub 3/ and (M(L/sub 2//sup (1)/ or L/sub 2//sup (2)/)(H/sub 2/O)/sub 2/)Cl/sub 3/ (M = Nd(III) and Sm(III)) have been isolated. In addition, macrocyclic complexes of Nd(III) andmore » Sm(III) with another series of tetraaza ligands, viz, 5,6,11,12-R/sub 4/-3,8-X/sub 2/-(12)-4,6,10,12-tetraene-1,4,7,10-N/sub 4/-(2,9-N/sub 2/) (R = CH/sub 3/, X = O (L/sub 3//sup (1)/); R = C/sub 6/H/sub 5/, X = O(L/sub 3//sup (2)/); R = CH/sub 3/, X = S(L/sub 4//sup (1)/); R = C/sub 6/H/sub 5/, X = S(L/sub 4//sup (2)/)), formulated as (M(L/sub 3//sup (1)/, L/sub 3//sup (2)/, L/sub 4//sup (1)/ or L/sub 4//sup (2)/)(H/sub 2/O)/sub 2/)Cl/sub 3/ (M = Nd(III) and Sm(III)) have been prepared by template condensation of Nd(III) and Sm(III) complexes of diacetylbis(semicarbazonethiosemicarbazone) or benzilibis(semicarbazonethiosemicarbazone) with diacetyl or benzil. The complexes have been identified by elemental analysis, electrical conductance, spectral and thermal measurements.« less

Ternary complex formation of Eu(III) with o-phthalate in aqueous solutions.

PubMed

Park, K K; Jung, E C; Cho, H-R; Kim, W H

2009-08-15

Ternary hydroxo complex formation of Eu(III) with o-phthalate was investigated by potentiometry and fluorescence spectrophotometry. Curves of the equilibrium pH versus the amount of NaOH added showed that the pH value starting to form a Eu(III) precipitate was decreased due to the formation of a ternary hydroxo complex, EuOHL(s) (L = phthalate). The formation of EuOHL(s) was qualitatively confirmed by the enhancement of the fluorescence intensity of Eu(III) in the precipitate with the light absorbed by phthalate, and was quantitatively confirmed by the measurement of the amounts of Eu(III), OH(-) and phthalate included in the precipitate. The solubility product of EuOHL(s) was determined as pK(sp)(0) = 15.6+/-0.4. Characteristic features in the fluorescence spectra and the solubility product of the Eu(III)-phthalate complex were compared with those of the Eu(III)-PDA (PDA = pyridine-2,6-dicarboxylate) complex. The fluorescence intensity of the EuL(+) complex of L = PDA was about 11 times stronger than that of L = phthalate. The origin of the difference in the fluorescence intensity is discussed based on the intramolecular energy transfer effect from the lowest triplet energy level of the ligand to the resonance energy level of Eu(III).

Biological and protein-binding studies of newly synthesized polymer-cobalt(III) complexes.

PubMed

Vignesh, G; Pradeep, I; Arunachalam, S; Vignesh, S; Arthur James, R; Arun, R; Premkumar, K

2016-03-01

The polymer-cobalt(III) complexes, [Co(bpy)(dien)BPEI]Cl3 · 4H2O (bpy = 2,2'-bipyridine, dien = diethylentriamine, BPEI = branched polyethyleneimine) were synthesized and characterized. The interaction of these complexes with human serum albumin (HSA) and bovine serum albumin (BSA) was investigated under physiological conditions using various physico-chemical techniques. The results reveal that the fluorescence quenching of serum albumins by polymer-cobalt(III) complexes took place through static quenching. The binding of these complexes changed the molecular conformation of the protein considerably. The polymer-cobalt(III) complex with x = 0.365 shows antimicrobial activity against several human pathogens. This complex also induces cytotoxicity against MCF-7 through apoptotic induction. However, further studies are needed to decipher the molecular mode of action of polymer-cobalt(III) complex and for its possible utilization in anticancer therapy. Copyright © 2015 John Wiley & Sons, Ltd.

Theoretical study of the magnetic exchange coupling behavior substituting Cr(III) with Mo(III) in cyano-bridged transition metal complexes

NASA Astrophysics Data System (ADS)

Zhang, Yi-Quan; Luo, Cheng-Lin

Molecular magnetism in a series of cyano-bridged first and second transition metal complexes has been investigated using density functional theory (DFT) combined with the broken-symmetry (BS) approach. Several exchange-correlation (XC) functionals in the ADF package were used to investigate complexes I [-(Me3tacn)2(cyclam)NiMo2(CN)6]2+, II [-(Me3tacn)2(cyclam)Ni-Cr2(CN)6]2+, III [(Me3tacn)6MnMo6(CN)18]2+, and IV [(Me3tacn)6MnCr6(CN)18]2+ (Me3tacn = N,N?,N‴-trimethyl-1,4,7-triazacyclononane). For models A (the molded structure of complex I) and B (the modeled structure of complex II), all the XCs given qualitatively reasonable results and predict ferromagnetic coupling character between M (M = MoIII for A or CrIII for B) and NiII in coincidence with the experimental results (see Tables and ). The calculated using Operdew, OPBE, O3LYP, and B3LYP functionals and experimental J values show that substituting CrIII with MoIII will enhance the ferromagnetic exchange coupling interactions. But VWN, PW91, PBE, VSXC, and tau-HCTH functionals have no way to differentiate the relative strength of the intramolecular magnetic exchange coupling interactions of A and B correctly. For models C (the modeled structure of complex III) and D (the modeled structure of complex IV), all the XCs in ADF and B3LYP in Gaussian 03 with several basis sets show that substituting CrIII with MoIII will enhance the antiferromagnetic exchange coupling interactions. From the above calculations, the substitution of CrIII by MoIII will enhance the magnetic coupling interactions, whether the magnetic coupling interactions are ferro- or antiferromagnetic. Moreover, Kahn's model was applied to investigate the above facts.

9,10-phenanthrenesemiquinone radical complexes of ruthenium(III), osmium(III) and rhodium(III) and redox series.

PubMed

Biswas, Manas Kumar; Patra, Sarat Chandra; Maity, Amarendra Nath; Ke, Shyue-Chu; Weyhermüller, Thomas; Ghosh, Prasanta

2013-05-14

Reactions of 9,10-phenanthrenequinone (PQ) in toluene with [M(II)(PPh3)3X2] at 298 K afford green complexes, trans-[M(PQ)(PPh3)2X2] (M = Ru, X = Cl, 1; M = Os, X = Br, 2) in moderate yields. Reaction of anhydrous RhCl3 with PQ and PPh3 in boiling ethanol affords the dark brown paramagnetic complex, cis-[Rh(PQ)(PPh3)2Cl2] (3) in good yields. Diffusion of iodine solution in n-hexane to the trans-[Os(PQ) (PPh3)2(CO)(Br)] solution in CH2Cl2 generates the crystals of trans-[Os(PQ)(PPh3)2(CO)(Br)](+)I3(-), (4(+))I3(-)), in lower yields. Single crystal X-ray structure determinations of 1·2toluene, 2·CH2Cl2 and 4(+)I3(-), UV-vis/NIR absorption spectra, EPR spectra of 3, electrochemical activities and DFT calculations on 1, 2, trans-[Ru(PQ)(PMe3)2Cl2] (1Me), trans-[Os(PQ)(PMe3)2Br2] (2Me), cis-[Rh(PQ)(PMe3)2Cl2] (3Me) and their oxidized and reduced analogues including trans-[Os(PQ)(PMe3)2(CO)(Br)](+) (4Me(+)) substantiated that 1-3 are the 9,10-phenanthrenesemiquinone radical (PQ(˙-)) complexes of ruthenium(III), osmium(III) and rhodium(III) and are defined as trans/cis-[M(III)(PQ(˙-))(PPh3)2X2] with a minor contribution of the resonance form trans/cis-[M(II)(PQ)(PPh3)2X2]. Two comparatively longer C-O (1.286(4) Å) and the shorter C-C lengths (1.415(7) Å) of the OO-chelate of 1·2toluene and 2·CH2Cl2 and the isotropic fluid solution EPR signal at g = 1.999 of 3 are consistent with the existence of the reduced PQ(˙-) ligand in 1-3 complexes. Anisotropic EPR spectra of the frozen glasses (g11 = g22 = 2.0046 and g33 = 1.9874) and solids (g11 = g22 = 2.005 and g33 = 1.987) instigate the contribution of the resonance form, cis-[Rh(II)(PQ)(PPh3)2Cl2] in 3. DFT calculations established that the closed shell singlet (CSS) solutions of 1Me and 2Me are unstable due to open shell singlet (OSS) perturbation. However, the broken symmetry (BS) (1,1) Ms = 0 solutions of 1Me and 2Me are respectively 22.6 and 24.2 kJ mole(-1) lower in energy and reproduced the experimental bond

Quantum Computational Studies of Electron Transfer in Respiratory Complex III and its Application for Designing New Mitocan Drugs

NASA Astrophysics Data System (ADS)

Hagras, Muhammad Ahmed

Electron transfer occurs in many biological systems which are imperative to sustain life; oxidative phosphorylation in prokaryotes and eukaryotes, and photophosphorylation in photosynthetic and plant cells are well-balanced and complementary processes. Investigating electron transfer in those natural systems provides detailed knowledge of the atomistic events that lead eventually to production of ATP, or harvesting light energy. Ubiquinol:cytochrome c oxidoreductase complex (also known as bc 1 complex, or respiratory complex III) is a middle player in the electron transport proton pumping orchestra, located in the inner-mitochondrial membrane in eukaryotes or plasma membrane in prokaryotes, which converts the free energy of redox reactions to electrochemical proton gradient across the membrane, following the fundamental chemiosmotic principle discovered by Peter Mitchell 1. In humans, the malfunctioned bc1 complex plays a major role in many neurodegenerative diseases, stress-induced aging, and cancer development, because it produces most of the reactive oxygen species, which are also involved in cellular signaling 2. The mitochondrial bc1 complex has an intertwined dimeric structure comprised of 11 subunits in each monomer, but only three of them have catalytic function, and those are the only domains found in bacterial bc1 complex. The core subunits include: Rieske domain, which incorporates iron-sulfur cluster [2Fe-2S]; trans-membrane cytochrome b domain, incorporating low-potential heme group (heme b L) and high-potential heme group (heme b H); and cytochrome c1 domain, containing heme c1 group and two separate binding sites, Qo (or QP) site where the hydrophobic electron carrier ubihydroquinol QH2 is oxidized, and Qi (or QN) site where ubiquinone molecule Q is reduced 3. Electrons and protons in the bc1 complex flow according to the proton-motive Q-cycle proposed by Mitchell, which includes a unique electron flow bifurcation at the Qo site. At this site, one

Spectroscopic characterization and reactivity studies of a mononuclear nonheme Mn(III)-hydroperoxo complex.

PubMed

So, Hee; Park, Young Jun; Cho, Kyung-Bin; Lee, Yong-Min; Seo, Mi Sook; Cho, Jaeheung; Sarangi, Ritimukta; Nam, Wonwoo

2014-09-03

We report the first example of a mononuclear nonheme manganese(III)-hydroperoxo complex derived from protonation of an isolated manganese(III)-peroxo complex bearing an N-tetramethylated cyclam (TMC) ligand, [Mn(III)(TMC)(OOH)](2+). The Mn(III)-hydroperoxo intermediate is characterized with various spectroscopic methods as well as with density functional theory (DFT) calculations, showing the binding of a hydroperoxide ligand in an end-on fashion. The Mn(III)-hydroperoxo species is a competent oxidant in oxygen atom transfer (OAT) reactions, such as the oxidation of sulfides. The electrophilic character of the Mn(III)-hydroperoxo complex is demonstrated unambiguously in the sulfoxidation of para-substituted thioanisoles.

Unsymmetrical Bimetallic Complexes with MII–(μ-OH)–MII Cores (MIIMIII = FeIIFeIII, MnIIFeIII, MnIIMnIII): Structural, Magnetic, and Redox Properties

PubMed Central

Sano, Yohei; Weitz, Andrew C.; Ziller, Joseph W.; Hendrich, Michael P.; Borovik, A.S.

2013-01-01

Heterobimetallic cores are important unit within the active sites of metalloproteins, but are often difficult to duplicate in synthetic systems. We have developed a synthetic approach for the preparation of a complex with a MnII–(μ-OH)–FeIII core, in which the metal centers have different coordination environments. Structural and physical data support the assignment of this complex as a heterobimetallic system. Comparison with the analogous homobimetallic complexes, those containing MnII–(μ-OH)–MnIII and FeII–(μ-OH)–FeIII cores, further supports this assignment. PMID:23992041

Quantitative description and local structures of trivalent metal ions Eu(III) and Cm(III) complexed with polyacrylic acid.

PubMed

Montavon, G; Bouby, M; Huclier-Markai, S; Grambow, B; Geckeis, H; Rabung, T; Pashalidis, I; Amekraz, B; Moulin, C

2008-11-15

The trivalent metal ion (M(III)=Cm, Eu)/polyacrylic acid (PAA) system was studied in the pH range between 3 and 5.5 for a molar PAA-to-metal ratio above 1. The interaction was studied for a wide range of PAA (0.05 mg L(-1)-50 g L(-1)) and metal ion concentrations (2x10(-9)-10(-3) M). This work aimed at 3 goals (i) to determine the stoichiometry of M(III)-PAA complexes, (ii) to determine the number of complexed species and the local environment of the metal ion, and (iii) to quantify the reaction processes. Asymmetric flow-field-flow fractionation (AsFlFFF) coupled to ICP-MS evidenced that size distributions of Eu-PAA complexes and PAA were identical, suggesting that Eu bound to only one PAA chain. Time-resolved laser fluorescence spectroscopy (TRLFS) measurements performed with Eu and Cm showed a continuous shift of the spectra with increasing pH. The environment of complexed metal ions obviously changes with pH. Most probably, spectral variations arose from conformational changes within the M(III)-PAA complex due to pH variation. Complexation data describing the distribution of complexed and free metal ion were measured with Cm by TRLFS. They could be quantitatively described in the whole pH-range studied by considering the existence of only a single complexed species. This indicates that the slight changes in M(III) speciation with pH observed at the molecular level do not significantly affect the intrinsic binding constant. The interaction constant obtained from the modelling must be considered as a mean interaction constant.

A needs assessment to determine the need for respiratory therapy in complex continuing care: A methods paper.

PubMed

Nickerson, Jason W

2015-01-01

There is an emerging demand for complex continuing care for patients who are too ill to safely return home, but for whom hospitalization in an acute care environment is unnecessary or inappropriate. Despite the need and medical complexity of these patients, few respiratory therapists are practising in this environment, and little evidence exists to guide the implementation of respiratory therapy services in this setting. In response to a perceived need for greater respiratory services at Saint Vincent Hospital (Ottawa, Ontario), a needs assessment was undertaken to assess the prevalence of respiratory diseases and for increased respiratory therapist coverage at this complex continuing care hospital. An initial literature review was conducted to guide the assessment, and identified only one tool of relevance, which was obtained and formed the basis of the further development of tools for collecting data at the hospital level and on patient care units at the facility. This needs assessment tool was expanded to include priority areas of relevance that fall within the scope of practice of respiratory therapists, and was supplemented by the analysis of administrative databases and qualitative data gathered through unit walkthroughs and unstructured key informant interviews. A health systems framework was used to structure recommendations for the development of interventions and programs for this patient population. The burden of respiratory disease was significant, and included a high prevalence of inhaled medication and oxygen use, and a significant workload that could be attributed to addressing the respiratory needs of patients. A range of tools and methods are needed to conduct needs assessments for respiratory therapy in complex continuing care. Using multiple data sources, a significant burden of respiratory diseases was present at the Saint Vincent Hospital; further studies in other complex continuing care hospitals are needed to understand the significance of

Organometallic rhodium(III) and iridium(III) cyclopentadienyl complexes with curcumin and bisdemethoxycurcumin co-ligands.

PubMed

Pettinari, Riccardo; Marchetti, Fabio; Pettinari, Claudio; Condello, Francesca; Petrini, Agnese; Scopelliti, Rosario; Riedel, Tina; Dyson, Paul J

2015-12-21

A series of half-sandwich cyclopentadienyl rhodium(III) and iridium(III) complexes of the type [Cp*M(curc/bdcurc)Cl] and [Cp*M(curc/bdcurc)(PTA)][SO3CF3], in which Cp* = pentamethylcyclopentadienyl, curcH = curcumin and bdcurcH = bisdemethoxycurcumin as O^O-chelating ligands, and PTA = 1,3,5-triaza-7-phosphaadamantane, is described. The X-ray crystal structures of three of the complexes, i.e. [Cp*Rh(curc)(PTA)][SO3CF3] (5), [Cp*Rh(bdcurc)(PTA)][SO3CF3] (6) and [Cp*Ir(bdcurc)(PTA)][SO3CF3] (8), confirm the expected "piano-stool" geometry. With the exception of 5, the complexes are stable under pseudo-physiological conditions and are moderately cytotoxic to human ovarian carcinoma (A2780 and A2780cisR) cells and also to non-tumorigenic human embryonic kidney (HEK293) cells, but lack the cancer cell selectivity observed for related arene ruthenium(II) complexes.

Dynamic subcellular localization of a respiratory complex controls bacterial respiration

PubMed Central

Alberge, François; Espinosa, Leon; Seduk, Farida; Sylvi, Léa; Toci, René; Walburger, Anne; Magalon, Axel

2015-01-01

Respiration, an essential process for most organisms, has to optimally respond to changes in the metabolic demand or the environmental conditions. The branched character of their respiratory chains allows bacteria to do so by providing a great metabolic and regulatory flexibility. Here, we show that the native localization of the nitrate reductase, a major respiratory complex under anaerobiosis in Escherichia coli, is submitted to tight spatiotemporal regulation in response to metabolic conditions via a mechanism using the transmembrane proton gradient as a cue for polar localization. These dynamics are critical for controlling the activity of nitrate reductase, as the formation of polar assemblies potentiates the electron flux through the complex. Thus, dynamic subcellular localization emerges as a critical factor in the control of respiration in bacteria. DOI: http://dx.doi.org/10.7554/eLife.05357.001 PMID:26077726

Strongly Circularly Polarized Emission from Water-Soluble Eu(III)- and Tb(III)-Based Complexes: A Structural and Spectroscopic Study.

PubMed

Leonzio, Marco; Melchior, Andrea; Faura, Georgina; Tolazzi, Marilena; Zinna, Francesco; Di Bari, Lorenzo; Piccinelli, Fabio

2017-04-17

Water-soluble Eu(III) and Tb(III) complexes with N,N'-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane-N,N'-diacetic acid (H 2 bpcd) have been synthesized and characterized in their racemic and enantiopure forms. The ligand has been designed to bind Ln(III) ions, providing a dissymmetric environment able to solicit strong chiroptical features while at the same time leaving a few coordination sites available for engaging further ancillary ligands. Potentiometric studies show that Ln(III) complexes have a relatively good stability and that at pH 7 the [Ln(bpcd)] + species is largely dominant. DFT calculations carried out on the (S,S)-[Y(bpcd)(H 2 O) 5 ] + complexes (the closed-shell equivalents of [Eu(bpcd)(H 2 O) 5 ] + and [Tb(bpcd)(H 2 O) 5 ] + ) indicate that the two trans-O,O and trans-N py ,N py configurations are equally stable in solution and present two coordinated water molecules. This is in agreement with the hydration number ∼2.6 determined by luminescence lifetime measurements on Tb(III) and Eu(III) complexes. A detailed optical and chiroptical spectroscopic characterization has been carried out and reveals that the complexes display an efficient luminescence in the visible spectral range accompanied by a strong CPL activity. A value for g lum (around 0.1 on the top of the 546 nm band) for the Tb-based complex has been found. This is one of the highest g lum values measured up to now for chiral Tb complexes. These results suggest that in principle Tb(bpcd)Cl is suitable to be employed as a CPL bioprobe for relevant analytes in aqueous media.

Synthesis, spectroscopic, thermal and anticancer studies of metal-antibiotic chelations: Ca(II), Fe(III), Pd(II) and Au(III) chloramphenicol complexes

NASA Astrophysics Data System (ADS)

Al-Khodir, Fatima A. I.; Refat, Moamen S.

2016-09-01

Four Ca(II), Fe(III), Pd(II) and Au(III) complexes of chloramphenicol drug have been synthesized and well characterized using elemental analyses, (infrared, electronic, and 1H-NMR) spectra, magnetic susceptibility measurement, and thermal analyses. Infrared spectral data show that the chloramphenicol drug coordinated to Ca(II), Pd(II) and Au(III) metal ions through two hydroxyl groups with 1:1 or 1:2 M ratios, but Fe(III) ions chelated towards chloramphenicol drug via the oxygen and nitrogen atoms of amide group with 1:2 ratio based on presence of keto↔enol form. The X-ray powder diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) techniques were used to identify the nano-size particles of both iron(III) and gold(III) chloramphenicol complexes. The antimicrobial assessments of the chloramphenicol complexes were scanned and collected the results against of some kind of bacteria and fungi. The cytotoxic activity of the gold(III) complex was tested against the human colon carcinoma (HCT-116) and human hepatocellular carcinoma (HepG-2) tumor cell lines.

Deficiency of respiratory chain complex I in Hashimoto thyroiditis.

PubMed

Zimmermann, Franz A; Neureiter, Daniel; Feichtinger, René G; Trost, Andrea; Sperl, Wolfgang; Kofler, Barbara; Mayr, Johannes A

2016-01-01

Oncocytic cells (OCs) are characterized by an accumulation of mitochondria and their occurrence in the thyroid gland of patients with Hashimoto thyroiditis (HT) is well known. However, their properties and functional relevance are poorly understood. We investigated OC lesions (n=212) in the thyroid of 12 HT patients. Loss of complex I protein was observed in oncocytic lesions of each of the patients. In addition to isolated complex I deficiency, 25% of oncocytic lesions showed combined deficiency of complex I and IV. Thus, we demonstrate for the first time a defect of respiratory chain complex I in OCs of HT patients. Copyright © 2015 Elsevier B.V. and Mitochondria Research Society. All rights reserved.

Luminescent and triboluminescent properties of europium(III) complex with cinnamic acid

NASA Astrophysics Data System (ADS)

Kalinovskaya, I. V.; Mirochnik, A. G.; Nagornyi, I. G.

2014-10-01

An intensely emitting crystalline europium(III) complex with cinnamic acid [Eu(Cin)3] n and exhibiting triboluminescent properties is synthesized. It is established that the measured photo- and triboluminescence spectra are identical for the above polymeric non-centrosymmetric complex and are determined by the characteristic f-f luminescence of the europium(III) ion.

Synthesis and characterization of a new Inonotus obliquus polysaccharide-iron(III) complex.

PubMed

Wang, Jia; Chen, Haixia; Wang, Yanwei; Xing, Lisha

2015-04-01

A new Inonotus obliquus polysaccharide-iron(III) complex (IOPS-iron) was synthesized and characterized. The preparation conditions of IOPS-iron(III) were optimized and the physicochemical properties were characterized by physicochemical methods, scanning electron microscopy (SEM), electron paramagnetic resonance (EPR) spectroscopy, fourier transform infrared (FTIR) spectroscopy, circular dichroism (CD) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy, respectively. The highest iron content of IOPS-iron(III) complex (19.40%) was obtained at the conditions: the ratio of IOPS and FeCl3 • 6H2O was 3:5 (w/w), the pH value of alkali solution was 10, the reaction temperature was 30 °C and the reaction time was 6h. The iron(III) was shown to be bound through the binding sites of the polysaccharide IOPS and it could form spatially separated iron centers on the polysaccharide backbone. IOPS-iron(III) complex was found to have good digestive availability and antioxidant activities in the in vitro assays, which suggested the IOPS-iron(III) complex might be used as a new iron supplement candidate. Copyright © 2015 Elsevier B.V. All rights reserved.

An isoelectronic NO dioxygenase reaction using a nonheme iron(III)-peroxo complex and nitrosonium ion.

PubMed

Yokoyama, Atsutoshi; Han, Jung Eun; Karlin, Kenneth D; Nam, Wonwoo

2014-02-18

Reaction of a nonheme iron(III)-peroxo complex, [Fe(III)(14-TMC)(O2)](+), with NO(+), a transformation which is essentially isoelectronic with that for nitric oxide dioxygenases [Fe(III)(O2˙(-)) + NO], affords an iron(IV)-oxo complex, [Fe(IV)(14-TMC)(O)](2+), and nitrogen dioxide (NO2), followed by conversion to an iron(III)-nitrato complex, [Fe(III)(14-TMC)(NO3)(F)](+).

Effects of reactive Mn(III)-oxalate complexes on structurally intact plant cell walls

NASA Astrophysics Data System (ADS)

Summering, J. A.; Keiluweit, M.; Goni, M. A.; Nico, P. S.; Kleber, M.

2011-12-01

Lignin components in the in plant litter are commonly assumed to have longer residence times in soil than many other compounds, which are supposedly, more easily degradable. The supposed resistance of lignin compounds to decomposition is generally attributed to the complex chain of biochemical steps required to create footholds in the non-porous structure of ligno-cellulose in cell walls. Interestingly, Mn(III) complexes have shown the ability to degrade ligno-cellulose. Mn(III) chelated by ligands such as oxalate are soluble oxidizers with a high affinity for lignin structures. Here we determined (i) the formation and decay kinetics of the Mn(III)-oxalate complexes in aqueous solution and (ii) the effects that these complexes have on intact ligno-cellulose. UV/vis spectroscopy and iodometric titrations confirmed the transient nature of Mn(III)-oxalate complexes with decay rates being in the order of hours. Zinnia elegans tracheary elements - a model ligno-cellulose substrate - were treated with Mn(III)-oxalate complexes in a newly developed flow-through reactor. Soluble decomposition products released during the treatment were analyzed by GC/MS and the degree of cell integrity was measured by cell counts, pre- and post-treatment counts indicate a decrease in intact Zinnia elegans as a result of Mn(III)-treatment. GC/MS results showed the release of a multitude of solubilized lignin breakdown products from plant cell walls. We conclude that Mn(III)-oxalate complexes have the ability to lyse intact plant cells and solubilize lignin. Lignin decomposition may thus be seen as resource dependent, with Mn(III) a powerful resource that should be abundant in terrestrial characterized by frequent redox fluctuations.

The Effect of Pressure and Temperature on Separation of Free Gadolinium(III) From Gd-DTPA Complex by Nanofiltration-Complexation Method

NASA Astrophysics Data System (ADS)

Rahayu, Iman; Anggraeni, Anni; Ukun, MSS; Bahti, Husein H.

2017-05-01

Nowdays, the utilization of rare earth elements has been carried out widely in industry and medicine, one of them is gadolinium in Gd-DTPA complex is used as a contrast agent in a magnetic resonance imaging (MRI) diagnostic to increase the visual contrast between normal tissue and diseased. Although the stability of a given complex may be high enough, the complexation step couldnot have been completed, so there is possible to gadolinium(III) in the complex compound. Therefore, the function of that compounds should be dangerous because of the toxicity of gadolinium(III) in human body. So, it is necessarry to separate free gadolinium(III) from Gd-DTPA complex by nanofiltration-complexation. The method of this study is complexing of Gd2O3 with DTPA ligand by reflux and separation of Gd-DTPA complex from gadolinium(III) with a nanofiltration membrane on the variation of pressures(2, 3, 4, 5, 6 bars) and temperature (25, 30, 35, 40 °C) and determined the flux and rejection. The results of this study are the higher of pressures and temperatures, permeation flux are increasing and ion rejections are decreasing and gave the free gadolinium(III) rejection until 86.26%.

Impact of Fe(III)-OM complexes and Fe(III) polymerization on SOM pools reactivity under different land uses

NASA Astrophysics Data System (ADS)

Giannetta, B.; Plaza, C.; Zaccone, C.; Siebecker, M. G.; Rovira, P.; Vischetti, C.; Sparks, D. L.

2017-12-01

Soil organic matter (SOM) protection and long-term accumulation are controlled by adsorption to mineral surfaces in different ways, depending on its molecular structure and pedo-climatic conditions. Iron (Fe) oxides are known to be key regulators of the soil carbon (C) cycle, and Fe speciation in soils is highly dependent on environmental conditions and chemical interactions with SOM. However, the molecular structure and hydrolysis of Fe species formed in association with SOM is still poorly described. We hypothesize the existence of two pools of Fe which interact with SOM: mononuclear Fe(III)-SOM complexes and precipitated Fe(III) hydroxides. To verify our hypothesis, we investigated the interactions between Fe(III) and physically isolated soil fractions by means of batch experiments at pH 7. Specifically, we examined the fine silt plus clay (FSi+C) fraction, obtained by ultrasonic dispersion and wet sieving. The soil samples spanned several land uses, including coniferous forest (CFS), grassland (GS), technosols (TS) and agricultural (AS) soils. Solid phase products and supernatants were analyzed for C and Fe content. X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analysis were also performed. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to assess the main C functional groups involved in C complexation and desorption experiments. Preliminary linear combination fitting (LCF) of Fe K-edge extended X-ray absorption fine structure (EXAFS) spectra suggested the formation of ferrihydrite-like polymeric Fe(III) oxides in reacted CFS and GS samples, with higher C and Fe concentration. Conversely, mononuclear Fe(III) OM complexes dominated the speciation for TS and AS samples, characterized by lower C and Fe concentration, inhibiting the hydrolysis and polymerization of Fe (III). This approach will help revealing the mechanisms by which SOM pools can control Fe(III) speciation, and will elucidate how both Fe(III

An isoelectronic NO dioxygenase reaction using a nonheme iron(III)-peroxo complex and nitrosonium ion†

PubMed Central

Yokoyama, Atsutoshi; Han, Jung Eun; Karlin, Kenneth D.; Nam, Wonwoo

2014-01-01

Reaction of a nonheme iron(III)-peroxo complex, [FeIII(14-TMC)(O2)]+, with NO+, a transformation which is essentially isoelectronic with that for nitric oxide dioxygenases [Fe(III)(O2•−) + NO], affords an iron(IV)-oxo complex, [FeIV(14-TMC)(O)]2+, and nitrogen dioxide (NO2), followed by conversion to an iron(III)-nitrato complex, [FeIII(14-TMC)(NO3)(F)]+. PMID:24394960

Syntheses, structures, and magnetic properties of a family of heterometallic heptanuclear [Cu5Ln2] (Ln = Y(III), Lu(III), Dy(III), Ho(III), Er(III), and Yb(III)) complexes: observation of SMM behavior for the Dy(III) and Ho(III) analogues.

PubMed

Chandrasekhar, Vadapalli; Dey, Atanu; Das, Sourav; Rouzières, Mathieu; Clérac, Rodolphe

2013-03-04

Sequential reaction of the multisite coordination ligand (LH3) with Cu(OAc)2·H2O, followed by the addition of a rare-earth(III) nitrate salt in the presence of triethylamine, afforded a series of heterometallic heptanuclear complexes containing a [Cu5Ln2] core {Ln = Y(1), Lu(2), Dy(3), Ho(4), Er(5), and Yb(6)}. Single-crystal X-ray crystallography reveals that all the complexes are dicationic species that crystallize with two nitrate anions to compensate the charge. The heptanuclear aggregates in 1-6 are centrosymmetrical complexes, with a hexagonal-like arrangement of six peripheral metal ions (two rare-earth and four copper) around a central Cu(II) situated on a crystallographic inversion center. An all-oxygen environment is found to be present around the rare-earth metal ions, which adopt a distorted square-antiprismatic geometry. Three different Cu(II) sites are present in the heptanuclear complexes: two possess a distorted octahedral coordination sphere while the remaining one displays a distorted square-pyramidal geometry. Detailed static and dynamic magnetic properties of all the complexes have been studied and revealed the single-molecule magnet behavior of the Dy(III) and Ho(III) derivatives.

Synthesis and luminescence properties of iridium(III) azide- and triazole-bisterpyridine complexes.

PubMed

Goldstein, Daniel C; Peterson, Joshua R; Cheng, Yuen Yap; Clady, Raphael G C; Schmidt, Timothy W; Thordarson, Pall

2013-07-26

We describe here the synthesis of azide-functionalised iridium(III) bisterpyridines using the "chemistry on the complex" strategy. The resulting azide-complexes are then used in the copper(I)-catalysed azide-alkyne Huisgen 1,3-dipolar cycloaddition "click chemistry" reaction to from the corresponding triazole-functionalised iridium(III) bisterpyridines. The photophysical characteristics, including lifetimes, of these compounds were also investigated. Interestingly, oxygen appears to have very little effect on the lifetime of these complexes in aqueous solutions. Unexpectedly, sodium ascorbate acid appears to quench the luminescence of triazole-functionalised iridium(III) bisterpyridines, but this effect can be reversed by the addition of copper(II) sulfate, which is known to oxidize ascorbate under aerobic conditions. The results demonstrate that iridium(III) bisterpyridines can be functionalized for use in "click chemistry" facilitating the use of these photophysically interesting complexes in the modification of polymers or surfaces, to highlight just two possible applications.

Synthesis and characterization of monomeric Mn (IV) and pseudo-tetrameric Mn (III) complexes: magnetic properties of Mn (III) complex.

PubMed

Yahsi, Yasemin; Kara, Hulya

2014-06-05

Two novel monomer Mn (IV) [Mn(3,5-ClL1)2]⋅(CH3OH), (1), [3,5-ClL1H2=N-(2-hydroxyethyl)-3,5-dichlorosalicylaldimine] (1) and hydrogen-bonded pseudo-tetramer Mn (III) [Mn(5-BrL2)(H2O)2]2⋅[Mn(5-BrL2)(H2O)]2⋅2⋅(ClO4), (2), [5-BrL2H2=N,N'-bis(5-bromosalicylidenato)-1,2-diamino-2-methylpropane)] (2) Schiff base complexes have been synthesized and their crystal structures have been determined by single crystal X-ray diffraction analysis. A variable temperature magnetic susceptibility measurement study has been performed for complex (2) and the result indicates there is a very weak antiferromagnetic interaction (J=-0.40±0.016cm(-1)) between the two manganese (III) centers. Copyright © 2014 Elsevier B.V. All rights reserved.

Photoluminescence studies on the complexation of Eu(III) and Tb(III) with acetohydroxamic acid (AHA) in nitrate medium.

PubMed

Pathak, P N; Mohapatra, M; Godbole, S V

2013-11-01

UREX process has been proposed for selective extraction of U(VI) and Tc(VII) from nitric acid medium (∼1M HNO3) using tri-n-butyl phosphate (TBP) as extractant and retaining Pu, Np and fission products in the aqueous phase. The feasibility of the use of luminescence spectroscopy as a technique to understand the complexation of trivalent f-elements cations viz. Eu(III) and Tb(III) with acetohydroxamic acid (AHA) in nitric acid medium has been examined. The luminescence lifetimes for the 1×10(-3)M Eu(III) and AHA complex system decreased with increased AHA concentration from 116±0.2μs (no AHA) to 1.6±0.1μs (0.1M AHA) which was attributed to dynamic quenching. The corrected fluorescence intensities were used to calculate the stability constant (log K) for the formation of 1:1 Eu(3+)-AHA complex as 1.42±0.64 under the conditions of this study. By contrast, the Tb(III)-AHA system at pH 3 (HNO3) did not show any significant variation in the life times of the excited state (364±9μs) suggesting the absence of dynamic quenching. The spectral changes in Tb(III)-AHA system showed the formation of 1:1 complex (log K: 1.72±0.21). These studies suggest that the extent of AHA complexation with the rare earth elements will be insignificant as compared to tetravalent metal ions Pu(IV) and Np(IV) under UREX process conditions. Copyright © 2013 Elsevier B.V. All rights reserved.

Photoluminescence studies on the complexation of Eu(III) and Tb(III) with acetohydroxamic acid (AHA) in nitrate medium

NASA Astrophysics Data System (ADS)

Pathak, P. N.; Mohapatra, M.; Godbole, S. V.

2013-11-01

UREX process has been proposed for selective extraction of U(VI) and Tc(VII) from nitric acid medium (∼1 M HNO3) using tri-n-butyl phosphate (TBP) as extractant and retaining Pu, Np and fission products in the aqueous phase. The feasibility of the use of luminescence spectroscopy as a technique to understand the complexation of trivalent f-elements cations viz. Eu(III) and Tb(III) with acetohydroxamic acid (AHA) in nitric acid medium has been examined. The luminescence lifetimes for the 1 × 10-3 M Eu(III) and AHA complex system decreased with increased AHA concentration from 116 ± 0.2 μs (no AHA) to 1.6 ± 0.1 μs (0.1 M AHA) which was attributed to dynamic quenching. The corrected fluorescence intensities were used to calculate the stability constant (log K) for the formation of 1:1 Eu3+-AHA complex as 1.42 ± 0.64 under the conditions of this study. By contrast, the Tb(III)-AHA system at pH 3 (HNO3) did not show any significant variation in the life times of the excited state (364 ± 9 μs) suggesting the absence of dynamic quenching. The spectral changes in Tb(III)-AHA system showed the formation of 1:1 complex (log K: 1.72 ± 0.21). These studies suggest that the extent of AHA complexation with the rare earth elements will be insignificant as compared to tetravalent metal ions Pu(IV) and Np(IV) under UREX process conditions.

Respiratory Chain Complexes in Dynamic Mitochondria Display a Patchy Distribution in Life Cells

PubMed Central

Muster, Britta; Kohl, Wladislaw; Wittig, Ilka; Strecker, Valentina; Joos, Friederike; Haase, Winfried; Bereiter-Hahn, Jürgen; Busch, Karin

2010-01-01

Background Mitochondria, the main suppliers of cellular energy, are dynamic organelles that fuse and divide frequently. Constraining these processes impairs mitochondrial is closely linked to certain neurodegenerative diseases. It is proposed that functional mitochondrial dynamics allows the exchange of compounds thereby providing a rescue mechanism. Methodology/Principal Findings The question discussed in this paper is whether fusion and fission of mitochondria in different cell lines result in re-localization of respiratory chain (RC) complexes and of the ATP synthase. This was addressed by fusing cells containing mitochondria with respiratory complexes labelled with different fluorescent proteins and resolving their time dependent re-localization in living cells. We found a complete reshuffling of RC complexes throughout the entire chondriome in single HeLa cells within 2–3 h by organelle fusion and fission. Polykaryons of fused cells completely re-mixed their RC complexes in 10–24 h in a progressive way. In contrast to the recently described homogeneous mixing of matrix-targeted proteins or outer membrane proteins, the distribution of RC complexes and ATP synthase in fused hybrid mitochondria, however, was not homogeneous but patterned. Thus, complete equilibration of respiratory chain complexes as integral inner mitochondrial membrane complexes is a slow process compared with matrix proteins probably limited by complete fusion. In co-expressing cells, complex II is more homogenously distributed than complex I and V, resp. Indeed, this result argues for higher mobility and less integration in supercomplexes. Conclusion/Significance Our results clearly demonstrate that mitochondrial fusion and fission dynamics favours the re-mixing of all RC complexes within the chondriome. This permanent mixing avoids a static situation with a fixed composition of RC complexes per mitochondrion. PMID:20689601

Mitochondrial reactive oxygen species production and respiratory complex activity in rats with pressure overload-induced heart failure

PubMed Central

Schwarzer, Michael; Osterholt, Moritz; Lunkenbein, Anne; Schrepper, Andrea; Amorim, Paulo; Doenst, Torsten

2014-01-01

We investigated the impact of cardiac reactive oxygen species (ROS) during the development of pressure overload-induced heart failure. We used our previously described rat model where transverse aortic constriction (TAC) induces compensated hypertrophy after 2 weeks, heart failure with preserved ejection fraction at 6 and 10 weeks, and heart failure with systolic dysfunction after 20 weeks. We measured mitochondrial ROS production rates, ROS damage and assessed the therapeutic potential of in vivo antioxidant therapies. In compensated hypertrophy (2 weeks of TAC) ROS production rates were normal at both mitochondrial ROS production sites (complexes I and III). Complex I ROS production rates increased with the appearance of diastolic dysfunction (6 weeks of TAC) and remained high thereafter. Surprisingly, maximal ROS production at complex III peaked at 6 weeks of pressure overload. Mitochondrial respiratory capacity (state 3 respiration) was elevated 2 and 6 weeks after TAC, decreased after this point and was significantly impaired at 20 weeks, when contractile function was also impaired and ROS damage was found with increased hydroxynonenal. Treatment with the ROS scavenger α-phenyl-N-tert-butyl nitrone or the uncoupling agent dinitrophenol significantly reduced ROS production rates at 6 weeks. Despite the decline in ROS production capacity, no differences in contractile function between treated and untreated animals were observed. Increased ROS production occurs early in the development of heart failure with a peak at the onset of diastolic dysfunction. However, ROS production may not be related to the onset of contractile dysfunction. PMID:24951621

Inner-sphere oxidation of ternary iminodiacetatochromium(III) complexes involving DL-valine and L-arginine as secondary ligands. Isokinetic relationship for the oxidation of ternary iminodiacetato-chromium(III) complexes by periodate.

PubMed

Ewais, Hassan A; Dahman, Faris D; Abdel-Khalek, Ahmed A

2009-02-04

In this paper, the kinetics of oxidation of [CrIII(HIDA)(Val)(H2O)2]+ and [CrIII(HIDA)(Arg)(H2O)2]+ (HIDA = iminodiacetic acid, Val = DL-valine and Arg = L-arginine) were studied. The choice of ternary complexes was attributed to two considerations. Firstly, in order to study the effect of the secondary ligands DL-valine and L-arginine on the stability of binary complex [CrIII(HIDA)(IDA)(H2O)] towards oxidation. Secondly, transition metal ternary complexes have received particular focus and have been employed in mapping protein surfaces as probes for biological redox centers and in protein capture for both purification and study. The results have shown that the reaction is first order with respect to both [IO4(-)] and the complex concentration, and the rate increases over the pH range 2.62 - 3.68 in both cases. The experimental rate law is consistent with a mechanism in which both the deprotonated forms of the complexes [CrIII(IDA)(Val)(H2O)2] and [CrIII(IDA)(Arg)(H2O)2] are significantly more reactive than the conjugate acids. The value of the intramolecular electron transfer rate constant for the oxidation of [CrIII(HIDA)(Arg)(H2O)2]+, k3 (1.82 x 10(-3) s(-1)), is greater than the value of k1 (1.22 x 10(-3) s(-1)) for the oxidation of [CrIII(HIDA)(Val)(H2O)2]+ at 45.0 degrees C and I = 0.20 mol dm(-3). It is proposed that electron transfer proceeds through an inner-sphere mechanism via coordination of IO4(-) to chromium(III). The oxidation of [CrIII(HIDA)(Val)(H2O)2]+ and [CrIII(HIDA)(Arg)(H2O)2]+ by periodate may proceed through an inner-sphere mechanism via two electron transfer giving chromium(VI). The value of the intramolecular electron transfer rate constant for the oxidation of [CrIII(HIDA)(Arg)(H2O)2]+, k3, is greater than the value of k1 for the oxidation of [CrIII(HIDA)(Val)(H2O)2]+. A common mechanism for the oxidation of ternary iminodiacetatochromium(III) complexes by periodate is proposed, and this is supported by an excellent isokinetic

Inner-sphere oxidation of ternary iminodiacetatochromium(III) complexes involving DL-valine and L-arginine as secondary ligands. Isokinetic relationship for the oxidation of ternary iminodiacetato-chromium(III) complexes by periodate

PubMed Central

Ewais, Hassan A; Dahman, Faris D; Abdel-Khalek, Ahmed A

2009-01-01

Background In this paper, the kinetics of oxidation of [CrIII(HIDA)(Val)(H2O)2]+ and [CrIII(HIDA)(Arg)(H2O)2]+ (HIDA = iminodiacetic acid, Val = DL-valine and Arg = L-arginine) were studied. The choice of ternary complexes was attributed to two considerations. Firstly, in order to study the effect of the secondary ligands DL-valine and L-arginine on the stability of binary complex [CrIII(HIDA)(IDA)(H2O)] towards oxidation. Secondly, transition metal ternary complexes have received particular focus and have been employed in mapping protein surfaces as probes for biological redox centers and in protein capture for both purification and study. Results The results have shown that the reaction is first order with respect to both [IO4-] and the complex concentration, and the rate increases over the pH range 2.62 – 3.68 in both cases. The experimental rate law is consistent with a mechanism in which both the deprotonated forms of the complexes [CrIII(IDA)(Val)(H2O)2] and [CrIII(IDA)(Arg)(H2O)2] are significantly more reactive than the conjugate acids. The value of the intramolecular electron transfer rate constant for the oxidation of [CrIII(HIDA)(Arg)(H2O)2]+, k3 (1.82 × 10-3 s-1), is greater than the value of k1 (1.22 × 10-3 s-1) for the oxidation of [CrIII(HIDA)(Val)(H2O)2]+ at 45.0°C and I = 0.20 mol dm-3. It is proposed that electron transfer proceeds through an inner-sphere mechanism via coordination of IO4- to chromium(III). Conclusion The oxidation of [CrIII(HIDA)(Val)(H2O)2]+ and [CrIII(HIDA)(Arg)(H2O)2]+ by periodate may proceed through an inner-sphere mechanism via two electron transfer giving chromium(VI). The value of the intramolecular electron transfer rate constant for the oxidation of [CrIII(HIDA)(Arg)(H2O)2]+, k3, is greater than the value of k1 for the oxidation of [CrIII(HIDA)(Val)(H2O)2]+. A common mechanism for the oxidation of ternary iminodiacetatochromium(III) complexes by periodate is proposed, and this is supported by an excellent

Cr(III), Fe(III) and Co(III) complexes of tetradentate (ONNO) Schiff base ligands: Synthesis, characterization, properties and biological activity

NASA Astrophysics Data System (ADS)

Keskioğlu, Eren; Gündüzalp, Ayla Balaban; Çete, Servet; Hamurcu, Fatma; Erk, Birgül

2008-08-01

A series of metal complexes were synthesized from equimolar amounts of Schiff bases: 1,4-bis[3-(2-hydroxy-1-naphthaldimine)propyl]piperazine (bappnaf) and 1,8-bis[3-(2-hydroxy-1-naphthaldimine)- p-menthane (damnaf) with metal chlorides. All of synthesized compounds were characterized by elemental analyses, spectral (UV-vis, IR, 1H- 13C NMR, LC-MS) and thermal (TGA-DTA) methods, magnetic and conductance measurements. Schiff base complexes supposed in tetragonal geometry have the general formula [M(bappnaf or damnaf)]Cl· nH 2O, where M = Cr(III), Co(III) and n = 2, 3. But also Fe(III) complexes have octahedral geometry by the coordination of two water molecules and the formula is [Fe(bappnaf or damnaf)(H 2O) 2]Cl. The changes in the selected vibration bands in FT-IR indicate that Schiff bases behave as (ONNO) tetradentate ligands and coordinate to metal ions from two phenolic oxygen atoms and two azomethine nitrogen atoms. Conductance measurements suggest 1:1 electrolytic nature of the metal complexes. The synthesized compounds except bappnaf ligand have the antimicrobial activity against the bacteria: Escherichia coli (ATCC 11230), Yersinia enterocolitica (ATCC 1501), Bacillus magaterium (RSKK 5117), Bacillus subtilis (RSKK 244), Bacillus cereus (RSKK 863) and the fungi: Candida albicans (ATCC 10239). These results have been considerably interest in piperazine derivatives due to their significant applications in antimicrobial studies.

Troxerutin attenuates diet-induced oxidative stress, impairment of mitochondrial biogenesis and respiratory chain complexes in mice heart.

PubMed

Rajagopalan, Geetha; Chandrasekaran, Sathiya Priya; Carani Venkatraman, Anuradha

2017-01-01

Mitochondrial abnormality is thought to play a key role in cardiac disease originating from the metabolic syndrome (MS). We evaluated the effect of troxerutin (TX), a semi-synthetic derivative of the natural bioflavanoid rutin, on the respiratory chain complex activity, oxidative stress, mitochondrial biogenesis and dynamics in heart of high fat, high fructose diet (HFFD) -induced mouse model of MS. Adult male Mus musculus mice of body weight 25-30 g were fed either control diet or HFFD for 60 days. Mice from each dietary regimen were divided into two groups on the 16th day and were treated or untreated with TX (150 mg/kg body weight [bw], per oral) for the next 45 days. At the end of experimental period, respiratory chain complex activity, uncoupling proteins (UCP)-2 and -3, mtDNA content, mitochondrial biogenesis and dynamics, oxidative stress markers and reactive oxygen species (ROS) generation were analyzed. Reduced mtDNA abundance with alterations in the expression of genes related to mitochondrial biogenesis and fission and fusion processes were observed in HFFD-fed mice. Disorganized and smaller mitochondria, reduction in complexes I, III and IV activities (by about 55%) and protein levels of UCP-2 (52%) and UCP-3 (46%) were noted in these mice. TX administration suppressed oxidative stress, improved the oxidative capacity and biogenesis and restored fission/fusion imbalance in the cardiac mitochondria of HFFD-fed mice. TX protects the myocardium by modulating the putative molecules of mitochondrial biogenesis and dynamics and by its anti-oxidant function in a mouse model of MS. © 2016 John Wiley & Sons Australia, Ltd.

Complexation of Curium(III) with DTPA at 10–70 °C: Comparison with Eu(III)–DTPA in Thermodynamics, Luminescence, and Coordination Modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Guoxin; Zhang, Zhiyong; Martin, Leigh R.

Separation of trivalent actinides (An(III)) from trivalent lanthanides (Ln(III)) is a challenging task because of their nearly identical chemical properties. Diethylenetriaminepentaacetate (DTPA), a key reagent used in the TALSPEAK process that effectively separates An(III) from Ln(III), is believed to play a critical role in the An(III)/Ln(III) separation. However, the underlying principles for the separation based on the difference in the complexation of DTPA with An(III) and Ln(III) remain unclear. In this work, the complexation of DTPA with Cm(III) at 10-70 ºC was investigated by spectrophotometry, luminescence spectroscopy, and microcalorimetry, in conjunction with computational methods. The binding strength, the enthalpy ofmore » complexation, the coordination modes, and the luminescence properties are compared between the Cm(III)-DTPA and Eu(III)-DTPA systems. The experimental and computational data have demonstrated that the difference between Cm(III) and Eu(III) in the binding strength with DTPA can be attributed to the stronger covalence bonding between Cm(III) and the nitrogen donors of DTPA.« less

Novel Luminescent Probe Based on a Terbium(III) Complex for Hemoglobin Determination

NASA Astrophysics Data System (ADS)

Yegorova, A. V.; Leonenko, I. I.; Aleksandrova, D. I.; Scrypynets, Yu. V.; Antonovich, V. P.; Ukrainets, I. V.

2014-09-01

We have studied the spectral luminescent properties of Tb(III) and Eu(III) complexes with a number of novel derivatives of oxoquinoline-3-carboxylic acid amides (L1-L5 ). We have observed quenching of the luminescence of 1:1 Tb(III)-L1-5 complexes by hemoglobin (Hb), which is explained by resonance energy transfer of electronic excitation from the donor (Tb(III)-L1-5 ) to the acceptor (Hb). Using the novel luminescent probe Tb(III)-L1, we have developed a method for determining Hb in human blood. The calibration Stern-Volmer plot is linear in the Hb concentration range 0.6-36.0 μg/mL, detection limit 0.2 μg/mL (3·10-9 mol/L).

Evidence for a hyperglycaemia-dependent decrease of antithrombin III-thrombin complex formation in humans.

PubMed

Ceriello, A; Giugliano, D; Quatraro, A; Marchi, E; Barbanti, M; Lefèbvre, P

1990-03-01

In the presence of increased levels of fibrinopeptide A, decreased antithrombin III biological activity, and thrombin-antithrombin III complex levels are seen in diabetic patients. Induced-hyperglycaemia in diabetic and normal subjects decreased antithrombin III activity and thrombin-antithrombin III levels, and increased fibrinopeptide A plasma levels, while antithrombin III concentration did not change; heparin was shown to reduced these phenomena. In diabetic patients, euglycaemia induced by insulin infusion restored antithrombin III activity, thrombin-antithrombin III complex and fibrinopeptide A concentrations; heparin administration had the same effects. These data stress the role of a hyperglycaemia-dependent decrease of antithrombin III activity in precipitating thrombin hyperactivity in diabetes mellitus.

PARACEST Properties of a Dinuclear Neodymium(III) Complex Bound to DNA or Carbonate

PubMed Central

Nwe, Kido; Andolina, Christopher M.; Huang, Ching-Hui; Morrow, Janet R.

2009-01-01

A dinuclear Nd(III) macrocyclic complex of 1 (1,4-bis[1-(4,7,10-tris(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane]-p-xylene) and mononuclear complexes of 1,4,7-tris-1,4,7,10-tetraazacyclododecane 2, and 1,4,7-tris[(N-N-diethyl)carbamoylmethyl]-1,4,7,10-tetraazacyclododecane, 3, are prepared. Complexes of 1 and 2 give rise to a PARACEST (paramagnetic chemical exchange saturation transfer) peak from exchangeable amide protons that resonate approximately 12 ppm downfield from the bulk water proton resonance. The dinuclear Nd(III) complex is promising as a PARACEST contrast agent for MRI applications because it has an optimal pH of 7.5 and the rate constant for amide proton exchange (2700 s−1) is nearly as large as it can be within slow exchange conditions with bulk water. Dinuclear Ln2(1) complexes (Ln(III) = Nd(III), Eu(III)) bind tightly to anionic ligands including carbonate, diethylphosphate and DNA. The CEST amide peak of Nd2(1) is enhanced by certain DNA sequences that contain hairpin loops, but decreases in the presence of diethyl phosphate or carbonate. Direct excitation luminescence studies of Eu2(1) show that double-stranded and hairpin loop DNA sequences displace one water ligand on each Eu(III) center. DNA displaces carbonate ion despite the low dissociation constant for the Eu2(1) carbonate complex (Kd = 15 µM). Enhancement of the CEST effect of a lanthanide complex by binding to DNA is a promising step toward the preparation of PARACEST agents containing DNA scaffolds. PMID:19555071

PARACEST properties of a dinuclear neodymium(III) complex bound to DNA or carbonate.

PubMed

Nwe, Kido; Andolina, Christopher M; Huang, Ching-Hui; Morrow, Janet R

2009-07-01

A dinuclear Nd(III) macrocyclic complex of 1 (1,4-bis[1-(4,7,10-tris(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane]-p-xylene) and mononuclear complexes of 1,4,7-tris-1,4,7,10-tetraazacyclododecane, 2, and 1,4,7-tris[(N-N-diethyl)carbamoylmethyl]-1,4,7,10-tetraazacyclododecane, 3, are prepared. Complexes of 1 and 2 give rise to a PARACEST (paramagnetic chemical exchange saturation transfer) peak from exchangeable amide protons that resonate approximately 12 ppm downfield from the bulk water proton resonance. The dinuclear Nd(III) complex is promising as a PARACEST contrast agent for MRI applications, because it has an optimal pH of 7.5 and the rate constant for amide proton exchange (2700 s(-1)) is nearly as large as it can be within slow exchange conditions with bulk water. Dinuclear Ln(2)(1) complexes (Ln(III) = Nd(III), Eu(III)) bind tightly to anionic ligands including carbonate, diethyl phosphate, and DNA. The CEST amide peak of Nd(2)(1) is enhanced by certain DNA sequences that contain hairpin loops, but decreases in the presence of diethyl phosphate or carbonate. Direct excitation luminescence studies of Eu(2)(1) show that double-stranded and hairpin-loop DNA sequences displace one water ligand on each Eu(III) center. DNA displaces carbonate ion despite the low dissociation constant for the Eu(2)(1) carbonate complex (K(d) = 15 microM). Enhancement of the CEST effect of a lanthanide complex by binding to DNA is a promising step toward the preparation of PARACEST agents containing DNA scaffolds.

Metabolic pathway profiling of mitochondrial respiratory chain mutants in C. elegans

PubMed Central

MJ, Falk; Z, Zhang; Rosenjack; Nissim; E, Daikhin; Nissim; MM, Sedensky; M, Yudkoff; PG, Morgan

2008-01-01

C. elegans affords a model of primary mitochondrial dysfunction that provides insight into cellular adaptations which accompany mutations in nuclear gene that encode mitochondrial proteins. To this end, we characterized genome-wide expression profiles of C. elegans strains with mutations in nuclear-encoded subunits of respiratory chain complexes. Our goal was to detect concordant changes among clusters of genes that comprise defined metabolic pathways. Results indicate that respiratory chain mutants significantly upregulate a variety of basic cellular metabolic pathways involved in carbohydrate, amino acid, and fatty acid metabolism, as well as cellular defense pathways such as the metabolism of P450 and glutathione. To further confirm and extend expression analysis findings, quantitation of whole worm free amino acid levels was performed in C. elegans mitochondrial mutants for subunits of complexes I, II, and III. Significant differences were seen for 13 of 16 amino acid levels in complex I mutants compared with controls, as well as overarching similarities among profiles of complex I, II, and III mutants compared with controls. The specific pattern of amino acid alterations observed provides novel evidence to suggest that an increase in glutamate-linked transamination reactions caused by the failure of NAD+ dependent oxidation of ketoacids occurs in primary mitochondrial respiratory chain mutants. Recognition of consistent alterations among patterns of nuclear gene expression for multiple biochemical pathways and in quantitative amino acid profiles in a translational genetic model of mitochondrial dysfunction allows insight into the complex pathogenesis underlying primary mitochondrial disease. Such knowledge may enable the development of a metabolomic profiling diagnostic tool applicable to human mitochondrial disease. PMID:18178500

Nucleophilic reactivity of a series of peroxomanganese(III) complexes supported by tetradentate aminopyridyl ligands.

PubMed

Geiger, Robert A; Chattopadhyay, Swarup; Day, Victor W; Jackson, Timothy A

2011-02-28

Peroxomanganese(iii) adducts have been postulated as important intermediates in manganese-containing enzymes and small molecule oxidation catalysts. Synthetic peroxomanganese(iii) complexes are known to be nucleophilic and facilitate aldehyde deformylation, offering a convenient way to compare relative reactivities of complexes supported by different ligands. In this work, tetradentate dipyridyldiazacycloalkane ligands with systematically perturbed steric and electronic properties were used to generate a series of manganese(ii) and peroxomanganese(iii) complexes. X-Ray crystal structures of five manganese(ii) complexes all show the ligands bound to give trans complexes. Treatment of these Mn(II) precursors with H(2)O(2) and Et(3)N in MeCN at -40 °C results in the formation of peroxomanganese(iii) complexes that differ only in the identity of the pyridine ring substituent and/or the number of carbons in the diazacycloalkane backbone. To determine the effects of small ligand perturbations on the reactivity of the peroxo group, the more thermally stable peroxomanganese(iii) complexes were reacted with cyclohexanecarboxaldehyde. For these complexes, the rate of deformylation does not correlate with the expected nucleophilicity of the peroxomanganese(iii) unit, as the inclusion of methyl substituents on the pyridines affords slower deformylation rates. It is proposed that adding methyl-substituents to the pyridines, or increasing the number of carbons on the diazacycloalkane, sterically hinders nucleophilic attack of the peroxo ligand on the carbonyl carbon of the aldehyde.

The role of geochemistry and energetics in the evolution of modern respiratory complexes from a proton-reducing ancestor.

PubMed

Schut, Gerrit J; Zadvornyy, Oleg; Wu, Chang-Hao; Peters, John W; Boyd, Eric S; Adams, Michael W W

2016-07-01

Complex I or NADH quinone oxidoreductase (NUO) is an integral component of modern day respiratory chains and has a close evolutionary relationship with energy-conserving [NiFe]-hydrogenases of anaerobic microorganisms. Specifically, in all of biology, the quinone-binding subunit of Complex I, NuoD, is most closely related to the proton-reducing, H2-evolving [NiFe]-containing catalytic subunit, MbhL, of membrane-bound hydrogenase (MBH), to the methanophenzine-reducing subunit of a methanogenic respiratory complex (FPO) and to the catalytic subunit of an archaeal respiratory complex (MBX) involved in reducing elemental sulfur (S°). These complexes also pump ions and have at least 10 homologous subunits in common. As electron donors, MBH and MBX use ferredoxin (Fd), FPO uses either Fd or cofactor F420, and NUO uses either Fd or NADH. In this review, we examine the evolutionary trajectory of these oxidoreductases from a proton-reducing ancestral respiratory complex (ARC). We hypothesize that the diversification of ARC to MBH, MBX, FPO and eventually NUO was driven by the larger energy yields associated with coupling Fd oxidation to the reduction of oxidants with increasing electrochemical potential, including protons, S° and membrane soluble organic compounds such as phenazines and quinone derivatives. Importantly, throughout Earth's history, the availability of these oxidants increased as the redox state of the atmosphere and oceans became progressively more oxidized as a result of the origin and ecological expansion of oxygenic photosynthesis. ARC-derived complexes are therefore remarkably stable respiratory systems with little diversity in core structure but whose general function appears to have co-evolved with the redox state of the biosphere. This article is part of a Special Issue entitled Respiratory Complex I, edited by Volker Zickermann and Ulrich Brandt. Copyright © 2016 Elsevier B.V. All rights reserved.

Atorvastatin affects negatively respiratory function of isolated endothelial mitochondria.

PubMed

Broniarek, Izabela; Jarmuszkiewicz, Wieslawa

2018-01-01

The purpose of this research was to elucidate the direct effects of two popular blood cholesterol-lowering drugs used to treat cardiovascular diseases, atorvastatin and pravastatin, on respiratory function, membrane potential, and reactive oxygen species formation in mitochondria isolated from human umbilical vein endothelial cells (EA.hy926 cell line). Hydrophilic pravastatin did not significantly affect endothelial mitochondria function. In contrast, hydrophobic calcium-containing atorvastatin induced a loss of outer mitochondrial membrane integrity, an increase in hydrogen peroxide formation, and reductions in maximal (phosphorylating or uncoupled) respiratory rate, membrane potential and oxidative phosphorylation efficiency. The atorvastatin-induced changes indicate an impairment of mitochondrial function at the level of ATP synthesis and at the level of the respiratory chain, likely at complex I and complex III. The atorvastatin action on endothelial mitochondria was highly dependent on calcium ions and led to a disturbance in mitochondrial calcium homeostasis. Uptake of calcium ions included in atorvastatin molecule induced mitochondrial uncoupling that enhanced the inhibition of the mitochondrial respiratory chain by atorvastatin. Our results indicate that hydrophobic calcium-containing atorvastatin, widely used as anti-atherosclerotic agent, has a direct negative action on isolated endothelial mitochondria. Copyright © 2017. Published by Elsevier Inc.

Anion responsive Europium (III) complexes for Optical Sensing and PARACEST MRI

NASA Astrophysics Data System (ADS)

Buttarazzi, Leandro Alfredo

The Eu(III) complexes of 1-(acetyl-7-Methyl-4-(trifluoromethyl) quinolin-2(1H)-one)4,7,10 tris(2-hydroxypropyl)-1,4,7,10-tetraazacycladodecane (Eu(S-THPC)3+ ) and 1-(acetyl-dioctadecylamine)4,7,10 tris(hydroxypropyl)-1,4,7,10-tetraazacycladodecane (Eu(S-THMC)3+) were studied in order to develop complexes that are both optical sensors and MRI contrast agents that respond to biologically relevant anions. Both complexes are related to Eu(S-THP) where S-THP = (1S,4S,7S,10S)-1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane. Eu(III) excitation, emission and time resolved luminescence spectroscopy experiments were used to study binding of the anions. One complex, Eu(THPC)3+ has an appended carbostyril dye for sensitization of Eu(III) luminescence. Luminescence experiments were done on this complex in order to quantify the effectiveness of the energy transfer from the dye to the lanthanide and to obtain binding constants of the anions from the Eu(III) emission peaks. Emission spectra were obtained by exciting the chromophore at 340 nm. Our results suggest that phosphate binds with a dissociation constant (Kd) of 4.2mM and citrate binds with a Kd of 228 uM. The quantum yield for the complex was low compared to other reported complexes in literature. Eu(S-THMC) 3+, and Eu(S-THMAC)3+ containing long carbon chains for incorporation into liposomes were explored as an approach to develop complexes with increased sensitivity as CEST agents. CEST experiments with the complex incorporated into a liposome and as a micelle were carried out. Liposome formation was achieved but no CEST effect was observed with two different lanthanide complexes. Eu(S-THMC)3+ gave the most promising results by showing CEST in acetonitrile and 50/50 acetonitrile/H 2O. However further experiments with this complex in buffered aqueous solution failed. Yb(S-THMAC)3+ solubility was poor in both acetonitrile and in water and this likely prevented the observation of CEST spectra.

The Ins and Outs of Breath Holding: Simple Demonstrations of Complex Respiratory Physiology

ERIC Educational Resources Information Center

Skow, Rachel J.; Day, Trevor A.; Fuller, Jonathan E.; Bruce, Christina D.; Steinback, Craig D.

2015-01-01

The physiology of breath holding is complex, and voluntary breath-hold duration is affected by many factors, including practice, psychology, respiratory chemoreflexes, and lung stretch. In this activity, we outline a number of simple laboratory activities or classroom demonstrations that illustrate the complexity of the integrative physiology…

Reactive Oxygen Species Production by Forward and Reverse Electron Fluxes in the Mitochondrial Respiratory Chain

PubMed Central

Selivanov, Vitaly A.; Votyakova, Tatyana V.; Pivtoraiko, Violetta N.; Zeak, Jennifer; Sukhomlin, Tatiana; Trucco, Massimo; Roca, Josep; Cascante, Marta

2011-01-01

Reactive oxygen species (ROS) produced in the mitochondrial respiratory chain (RC) are primary signals that modulate cellular adaptation to environment, and are also destructive factors that damage cells under the conditions of hypoxia/reoxygenation relevant for various systemic diseases or transplantation. The important role of ROS in cell survival requires detailed investigation of mechanism and determinants of ROS production. To perform such an investigation we extended our rule-based model of complex III in order to account for electron transport in the whole RC coupled to proton translocation, transmembrane electrochemical potential generation, TCA cycle reactions, and substrate transport to mitochondria. It fits respiratory electron fluxes measured in rat brain mitochondria fueled by succinate or pyruvate and malate, and the dynamics of NAD+ reduction by reverse electron transport from succinate through complex I. The fitting of measured characteristics gave an insight into the mechanism of underlying processes governing the formation of free radicals that can transfer an unpaired electron to oxygen-producing superoxide and thus can initiate the generation of ROS. Our analysis revealed an association of ROS production with levels of specific radicals of individual electron transporters and their combinations in species of complexes I and III. It was found that the phenomenon of bistability, revealed previously as a property of complex III, remains valid for the whole RC. The conditions for switching to a state with a high content of free radicals in complex III were predicted based on theoretical analysis and were confirmed experimentally. These findings provide a new insight into the mechanisms of ROS production in RC. PMID:21483483

A general access to organogold(iii) complexes by oxidative addition of diazonium salts.

PubMed

Huang, Long; Rominger, Frank; Rudolph, Matthias; Hashmi, A Stephen K

2016-05-11

At room temperature under mild photochemical conditions, namely irradiation with a simple blue light LED, gold(i) chloro complexes of both phosphane and carbene ligands in combination with aryldiazonium salts afford arylgold(iii) complexes. With chelating P,N-ligands cationic six- or five-membered chelate complexes were isolated in the form of salts with weakly coordinating counter anions that were brought in from the diazonium salt. With monodentate P ligands or N-heterocyclic carbene ligands and diazonium chlorides neutral arylgold(iii) dichloro complexes were obtained. The coordination geometry was determined by X-ray crystal structure analyses of representative compounds, a cis arrangement of the aryl and the phosphane ligand at the square planar gold(iii) center is observed.

The patient with a complex chronic respiratory disease: a specialist of his own life?

PubMed

Houben-Wilke, Sarah; Augustin, Ingrid Ml; Wouters, Birgit Bref; Stevens, Rosita Ah; Janssen, Daisy Ja; Spruit, Martijn A; Vanfleteren, Lowie Egw; Franssen, Frits Me; Wouters, Emiel Fm

2017-12-01

The independent and central role of the patient with a complex chronic respiratory disease in targeted, personalized disease management strategies is becoming increasingly important. Patients are the ones living with the disease and are finally responsible for their lives underlining their role as essential members of the interdisciplinary treatment team. Areas covered: The present paper narratively reviews existing research and discusses the special, as well as specialized, role of the patient with a complex chronic respiratory disease in the healthcare system and highlights fundamental elements of the (future) relationship between patient and healthcare professionals. Expert commentary: Since the chronic respiratory disease at hand is part of the patient's entire life, we need holistic, personalized approaches optimizing patients' quality of life by not only treating the disease but considering the patients' whole environment and where healthcare professionals and patients are co-creating value care.

Structure and luminescent property of complexes of aryl carboxylic acid-functionalized polystyrene with Eu(III) and Tb(III) ions.

PubMed

Gao, Baojiao; Shi, Nan; Qiao, Zongwen

2015-11-05

Via polymer reactions, naphthoic acid (NA) and benzoic acid (BA) were bonded onto the side chains of polystyrene (PS), respectively, and two aryl carboxylic acid-functionalized polystyrenes, PSNA and PSBA, were obtained. Using PSNA and PSBA as macromolecule ligands and Eu(3+) and Tb(3+) ions as central ions, various luminescent binary polymer-rare earth complexes were prepared. At the same time, with 1,10-phenanthroline (Phen) and 4,4'-bipyridine (Bipy) as small-molecule co-ligands, various ternary polymer-rare earth complexes were also prepared. On the basis of characterizing PSNA, PSBA and complexes, the relationship between structure and luminescent property for these prepared complexes were mainly investigated. The study results show that the macromolecule ligands PSNA and PSBA, or the bonded NA and BA ligands, can strongly sensitize the fluorescence emissions of Eu(3+) ion or Tb(3+) ion, but the sensitization effect is strongly dependent on the structure of the ligands and the property of the central ions, namely it is strongly dependent on the matching degree of energy levels. The fluorescence emission of the binary complex PS-(NA)3-Eu(III) is stronger than that PS-(BA)3-Eu(III), indicating ligand NA has stronger sensitization action for Eu(3+) ion than ligand BA; the binary complex PS-(BA)3-Tb(III) emit strong characteristic fluorescence of Tb(3+) ion, displaying that ligand BA can strongly sensitize Tb(3+) ion, whereas the binary complex PS-(NA)3-Tb(III) nearly does not emit the characteristic fluorescence of Tb(3+) ion, showing that ligand NA does not sensitize Tb(3+) ion. The fluorescence intensity of the ternary complexes is much stronger than that of the binary complexes in the same series. Copyright © 2015 Elsevier B.V. All rights reserved.

Mononuclear ruthenium(III) complexes containing chelating thiosemicarbazones: Synthesis, characterization and catalytic property

NASA Astrophysics Data System (ADS)

Raja, N.; Ramesh, R.

2010-02-01

Mononuclear ruthenium(III) complexes of the type [RuX(EPh 3) 2(L)] (E = P or As; X = Cl or Br; L = dibasic terdentate dehydroacetic acid thiosemicarbazones) have been synthesized from the reaction of thiosemicarbazone ligands with ruthenium(III) precursors, [RuX 3(EPh 3) 3] (where E = P, X = Cl; E = As, X = Cl or Br) and [RuBr 3(PPh 3) 2(CH 3OH)] in benzene. The compositions of the complexes have been established by elemental analysis, magnetic susceptibility measurement, FT-IR, UV-vis and EPR spectral data. These complexes are paramagnetic and show intense d-d and charge transfer transitions in dichloromethane. The complexes show rhombic EPR spectra at LNT which are typical of low-spin distorted octahedral ruthenium(III) species. All the complexes are redox active and display an irreversible metal centered redox processes. Complex [RuCl(PPh 3) 2(DHA-PTSC)] ( 5) was used as catalyst for transfer hydrogenation of ketones in the presence of isopropanol/KOH and was found to be the active species.

Rényi entropy and Lempel-Ziv complexity of mechanomyographic recordings of diaphragm muscle as indexes of respiratory effort.

PubMed

Torres, Abel; Fiz, Jose A; Jane, Raimon; Laciar, Eric; Galdiz, Juan B; Gea, Joaquim; Morera, Josep

2008-01-01

The study of the mechanomyographic (MMG) signals of respiratory muscles is a promising technique in order to evaluate the respiratory muscles effort. A new approach for quantifying the relationship between respiratory MMG signals and respiratory effort is presented by analyzing the spatio-temporal patterns in the MMG signal using two non-linear methods: Rényi entropy and Lempel-Ziv (LZ) complexity analysis. Both methods are well suited to the analysis of non-stationary biomedical signals of short length. In this study, MMG signals of the diaphragm muscle acquired by means of a capacitive accelerometer applied on the costal wall were analyzed. The method was tested on an animal model (dogs), and the diaphragmatic MMG signal was recorded continuously while two non anesthetized mongrel dogs performed a spontaneous ventilation protocol with an incremental inspiratory load. The performance in discriminating high and low respiratory effort levels with these two methods was analyzed with the evaluation of the Pearson correlation coefficient between the MMG parameters and respiratory effort parameters extracted from the inspiratory pressure signal. The results obtained show an increase of the MMG signal Rényi entropy and LZ complexity values with the increase of the respiratory effort. Compared with other parameters analyzed in previous works, both Rényi entropy and LZ complexity indexes demonstrates better performance in all the signals analyzed. Our results suggest that these non-linear techniques are useful to detect and quantify changes in the respiratory effort by analyzing MMG respiratory signals.

Exposing the Complex III Qo semiquinone radical

PubMed Central

Zhang, Haibo; Osyczka, Artur; Dutton, P. L.; Moser, Christopher C.

2012-01-01

Complex III Qo site semiquinone has been assigned pivotal roles in productive energy-conversion and destructive superoxide generation. After a 30 year search, a genetic heme bH knockout arrests this transient semiquinone EPR radical, revealing the natural engineering balance pitting energy-conserving, short-circuit minimizing, split electron transfer and catalytic speed against damaging oxygen reduction. PMID:17560537

Me-3,2-HOPO Complexes of Near Infra-Red (NIR) Emitting Lanthanides: Efficient Sensitization of Yb(III) and Nd(III) in Aqueous Solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, Evan G.; Xu, Jide; Dodani, Sheel

2009-11-10

The synthesis, X-ray structure, solution stability, and photophysical properties of several trivalent lanthanide complexes of Yb(III) and Nd(III) using both tetradentate and octadentate ligand design strategies and incorporating the 1-methyl-3-hydroxy-pyridin-2-one (Me-3,2-HOPO) chelate group are reported. Both the Yb(III) and Nd(III) complexes have emission bands in the Near Infra-Red (NIR) region, and this luminescence is retained in aqueous solution ({Phi}{sub tot}{sup Yb} {approx} 0.09-0.22%). Furthermore, the complexes demonstrate very high stability (pYb {approx} 18.8-21.9) in aqueous solution, making them good candidates for further development as probes for NIR imaging. Analysis of the low temperature (77 K) photophysical measurements for a modelmore » Gd(III) complex were used to gain an insight into the electronic structure, and were found to agree well with corresponding TD-DFT calculations at the B3LYP/6-311G{sup ++}(d,p) level of theory for a simplified model monovalent sodium complex.« less

Rhombus-shaped tetranuclear [Ln4] complexes [Ln = Dy(III) and Ho(III)]: synthesis, structure, and SMM behavior.

PubMed

Chandrasekhar, Vadapalli; Hossain, Sakiat; Das, Sourav; Biswas, Sourav; Sutter, Jean-Pascal

2013-06-03

The reaction of a new hexadentate Schiff base hydrazide ligand (LH3) with rare earth(III) chloride salts in the presence of triethylamine as the base afforded two planar tetranuclear neutral complexes: [{(LH)2Dy4}(μ2-O)4](H2O)8·2CH3OH·8H2O (1) and [{(LH)2Ho4}(μ2-O)4](H2O)8·6CH3OH·4H2O (2). These neutral complexes possess a structure in which all of the lanthanide ions and the donor atoms of the ligand remain in a perfect plane. Each doubly deprotonated ligand holds two Ln(III) ions in its two distinct chelating coordination pockets to form [LH(Ln)2](4+) units. Two such units are connected by four [μ2-O](2-) ligands to form a planar tetranuclear assembly with an Ln(III)4 core that possesses a rhombus-shaped structure. Detailed static and dynamic magnetic analysis of 1 and 2 revealed single-molecule magnet (SMM) behavior for complex 1. A peculiar feature of the χM" versus temperature curve is that two peaks that are frequency-dependent are revealed, indicating the occurrence of two relaxation processes that lead to two energy barriers (16.8 and 54.2 K) and time constants (τ0 = 1.4 × 10(-6) s, τ0 = 7.2 × 10(-7) s). This was related to the presence of two distinct geometrical sites for Dy(III) in complex 1.

Respiratory complex I: 'steam engine' of the cell?

PubMed

Efremov, Rouslan G; Sazanov, Leonid A

2011-08-01

Complex I is the first enzyme of the respiratory chain and plays a central role in cellular energy production. It has been implicated in many human neurodegenerative diseases, as well as in ageing. One of the biggest membrane protein complexes, it is an L-shaped assembly consisting of hydrophilic and membrane domains. Previously, we have determined structures of the hydrophilic domain in several redox states. Last year was marked by fascinating breakthroughs in the understanding of the complete structure. We described the architecture of the membrane domain and of the entire bacterial complex I. X-ray analysis of the larger mitochondrial enzyme has also been published. The core subunits of the bacterial and mitochondrial enzymes have remarkably similar structures. The proposed mechanism of coupling between electron transfer and proton translocation involves long-range conformational changes, coordinated in part by a long α-helix, akin to the coupling rod of a steam engine. Copyright © 2011 Elsevier Ltd. All rights reserved.

Identification of an iridium(III) complex with anti-bacterial and anti-cancer activity

PubMed Central

Lu, Lihua; Liu, Li-Juan; Chao, Wei-chieh; Zhong, Hai-Jing; Wang, Modi; Chen, Xiu-Ping; Lu, Jin-Jian; Li, Ruei-nian; Ma, Dik-Lung; Leung, Chung-Hang

2015-01-01

Group 9 transition metal complexes have been widely explored as therapeutic agents due to their unique geometry, their propensity to undergo ligand exchanges with biomolecules and their diverse steric and electronic properties. These metal complexes can offer distinct modes of action in living organisms compared to carbon-based molecules. In this study, we investigated the antimicrobial and anti-proliferative abilities of a series of cyclometallated iridium(III) complexes. The iridium(III) complex 1 inhibited the growth of S. aureus with MIC and MBC values of 3.60 and 7.19 μM, respectively, indicating its potent bactericidal activity. Moreover, complex 1 also exhibited cytotoxicity against a number of cancer cell lines, with particular potency against ovarian, cervical and melanoma cells. This cyclometallated iridium(III) complex is the first example of a substitutionally-inert, Group 9 organometallic compound utilized as a direct and selective inhibitor of S. aureus. PMID:26416333

Synthesis, antiproliferative activity and mechanism of gallium(III)-thiosemicarbazone complexes as potential anti-breast cancer agents.

PubMed

Qi, Jinxu; Yao, Qian; Qian, Kun; Tian, Liang; Cheng, Zhen; Yang, Dongmei; Wang, Yihong

2018-05-14

Five thiosemicarbazone ligands were synthesized and characterized by condensation with different aldehydes or ketones by 4-phenylthiosemicarbazone. The representative dichlorido[2-(Di-2-pyridinylmethylene)-Nphenylhydrazinecarbothioamide-N,N,S]-gallium(III) (Ga4) was characterized by X-ray single crystal diffraction, which was 1:1 ligand/Ga(III) complexes. The structure-activity relationship of these ligands and Ga (III) complexes have been investigated, and the results demonstrate that the formation of Ga (III) complexes have significant antiproliferative activity over the corresponding ligands. The anticancer mechanism of gallium (III) complexes has been studied in detail, which is typical agents that effect on the mitochondrial apoptotic pathway. The ability of gallium (III) complexes to inhibit the cell cycle does not enhanced with the increasing concentrations, whereas the ability to promote apoptosis is concentration-dependent. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Dissociation kinetics of Fe(III)- and Al(III)-natural organic matter complexes at pH 6.0 and 8.0 and 25 °C

NASA Astrophysics Data System (ADS)

Jones, Adele M.; Pham, A. Ninh; Collins, Richard N.; Waite, T. David

2009-05-01

The rate at which iron- and aluminium-natural organic matter (NOM) complexes dissociate plays a critical role in the transport of these elements given the readiness with which they hydrolyse and precipitate. Despite this, there have only been a few reliable studies on the dissociation kinetics of these complexes suggesting half-times of some hours for the dissociation of Fe(III) and Al(III) from a strongly binding component of NOM. First-order dissociation rate constants are re-evaluated here at pH 6.0 and 8.0 and 25 °C using both cation exchange resin and competing ligand methods for Fe(III) and a cation exchange resin method only for Al(III) complexes. Both methods provide similar results at a particular pH with a two-ligand model accounting satisfactorily for the dissociation kinetics results obtained. For Fe(III), half-times on the order of 6-7 h were obtained for dissociation of the strong component and 4-5 min for dissociation of the weak component. For aluminium, the half-times were on the order of 1.5 h and 1-2 min for the strong and weak components, respectively. Overall, Fe(III) complexes with NOM are more stable than analogous complexes with Al(III), implying Fe(III) may be transported further from its source upon dilution and dispersion.

Supramolecular organization of cytochrome c oxidase- and alternative oxidase-dependent respiratory chains in the filamentous fungus Podospora anserina.

PubMed

Krause, Frank; Scheckhuber, Christian Q; Werner, Alexandra; Rexroth, Sascha; Reifschneider, Nicole H; Dencher, Norbert A; Osiewacz, Heinz D

2004-06-18

To elucidate the molecular basis of the link between respiration and longevity, we have studied the organization of the respiratory chain of a wild-type strain and of two long-lived mutants of the filamentous fungus Podospora anserina. This established aging model is able to respire by either the standard or the alternative pathway. In the latter pathway, electrons are directly transferred from ubiquinol to the alternative oxidase and thus bypass complexes III and IV. We show that the cytochrome c oxidase pathway is organized according to the mammalian "respirasome" model (Schägger, H., and Pfeiffer, K. (2000) EMBO J. 19, 1777-1783). In contrast, the alternative pathway is composed of distinct supercomplexes of complexes I and III (i.e. I(2) and I(2)III(2)), which have not been described so far. Enzymatic analysis reveals distinct functional properties of complexes I and III belonging to either cytochrome c oxidase- or alternative oxidase-dependent pathways. By a gentle colorless-native PAGE, almost all of the ATP synthases from mitochondria respiring by either pathway were preserved in the dimeric state. Our data are of significance for the understanding of both respiratory pathways as well as lifespan control and aging.

Electron-transfer reactions of cobalt(III) complexes. 1. The kinetic investigation of the reduction of various surfactant cobalt(III) complexes by iron(II) in surface active ionic liquids

NASA Astrophysics Data System (ADS)

Nagaraj, Karuppiah; Senthil Murugan, Krishnan; Thangamuniyandi, Pilavadi; Sakthinathan, Subramanian

2015-05-01

The kinetics of outer sphere electron transfer reaction of surfactant cobalt(III) complex ions, cis-[Co(en)2(C12H25NH2)2]3+ (1), cis-[Co(dp)2(C12H25NH2)2]3+ (2), cis-[Co(trien)(C12H25NH2)2]3+ (3), cis-[Co(bpy)2(C12H25NH2)2]3+ (4) and cis-[Co(phen)2(C12H25NH2)2]3+ (5) (en: ethylenediamine, dp: diaminopropane, trien : triethylenetetramine, bpy: 2,2‧-bipyridyl, phen: 1,10-phenanthroline and C12H25NH2 : dodecylamine) have been interrogated by Fe2+ ion in ionic liquid (1-butyl-3-methylimidazoliumbromide) medium at different temperatures (298, 303, 308, 313, 318 and 323 K) by the spectrophotometry method under pseudo first order conditions using an excess of the reductant. Experimentally the reactions were found to be of second order and the electron transfer as outer sphere. The second order rate constant for the electron transfer reaction in ionic liquids was found to increase with increase in the concentration of all these surfactant cobalt(III) complexes. Among these complexes (from en to phen ligand), complex containing the phenanthroline ligand rate is higher compared to other complexes. By assuming the outer sphere mechanism, the results have been explained based on the presence of aggregated structures containing cobalt(III) complexes at the surface of ionic liquids formed by the surfactant cobalt(III) complexes in the reaction medium. The activation parameters (enthalpy of activation ΔH‡ and entropy of activation ΔS‡) of the reaction have been calculated which substantiate the kinetics of the reaction.

Synthesis, spectral and electrochemical studies of binuclear Ru(III) complexes containing dithiosemicarbazone ligand

NASA Astrophysics Data System (ADS)

Kanchana Devi, A.; Ramesh, R.

2014-01-01

Synthesis of several new octahedral binuclear ruthenium(III) complexes of the general composition [(EPh3)2(X)Ru-L-Ru(X)(EPh3)2] containing benzene dithiosemicarbazone ligands (where E = P or As; X = Cl or Br; L = binucleating ligands) is presented. All the complexes have been fully characterized by elemental analysis, FT-IR, UV-vis and EPR spectroscopy together with magnetic susceptibility measurements. IR study shows that the dithiosemicarbazone ligands behave as dianionic tridentate ligands coordinating through the oxygen atom of the deprotonated phenolic group, nitrogen atom of the azomethine group and thiolate sulphur. In DMF solution, all the complexes exhibit intense d-d transition and ligand-to-metal charge transfer (LMCT) transition in the visible region. The magnetic moment values of the complexes are in the range 1.78-1.82 BM, which reveals the presence of one unpaired electron on each metal ion. The EPR spectra of the liquid samples at LNT show the presence of three different 'g' values (gx ≠ gy ≠ gz) indicate a rhombic distortion around the ruthenium ion. All the complexes exhibit two quasi-reversible one electron oxidation responses (RuIII-RuIII/RuIII-RuIV; RuIII-RuIV/RuIV-RuIV) within the E1/2 range of 0.61-0.74 V and 0.93-0.98 V respectively, versus Ag/AgCl.

Photophysical properties of ortho-metalated monomeric and dimeric complexes containing rhodium(III) and iridium(III) metal centers

NASA Astrophysics Data System (ADS)

Marshall, Jason Alexander

Photophysical properties of dichloro-bridged dimers and monomeric tris complexes of the type [M(NC)2Cl]2 and M(NC)3, where NC refers to the ortho-metalating ligands 2-phenylpyridine (ppy), benzo[h]quinoline (bzq), or 2-(p-tolyl)pyridine (ptpy) and M is Rh(III) or Ir(III), were investigated. Excited-state emission of Rh(III) complexes are highly structured and independent of temperature from 4--100 K in glassy media, with long lifetimes (102 mus to ms). Emission is not observed from the pale yellow, fluid solutions of Rh(III) complexes at room temperature. Below 7K, decay kinetics are sensitive to temperature and are complicated, requiring multi-exponential fits in 4:1 EtOH/MeOH. The spectroscopic properties are consistent with the assignment of a lowest 3pipi* excited-state manifold perturbed by an admixture of higher-lying states possessing strong spin-orbit interactions. The complicated decays are attributed to spin-relaxation-limited behavior between spin-levels in the 3pipi* manifold. Deep yellow solutions of Ir(III) complexes in 4:1 EtOH/MeOH are observed to emit in both glassy media and in fluid solution, displaying severe changes in spectral shape as the glass softens which are not attributable to rigidochromic shifts. Low-temperature spectra are structured with emission origins in the range 496--520 nm whereas room-temperature emission of complexes in fluid solution are characteristically broad structureless bands with maxima redshifted from spectra measured in rigid media. Both the emission and the excited-state lifetimes display temperature dependence, with lifetimes in the microsecond to tens of microseconds range at 77 K, increasing by more than an order of magnitude as the temperature is decreased to 4 K. Each of these characteristic band shapes arises from separate components of the emission which have been time-resolved from the low-temperature spectrum. A long-lived, structured component of the emission, only observed in rigid media, has been

Exploring the Influence of Diamagnetic Ions on the Mechanism of Magnetization Relaxation in {CoIII2LnIII2} (Ln = Dy, Tb, Ho) "Butterfly" Complexes.

PubMed

Vignesh, Kuduva R; Langley, Stuart K; Murray, Keith S; Rajaraman, Gopalan

2017-03-06

The synthesis and magnetic and theoretical studies of three isostructural heterometallic [Co III 2 Ln III 2 (μ 3 -OH) 2 (o-tol) 4 (mdea) 2 (NO 3 ) 2 ] (Ln = Dy (1), Tb (2), Ho (3)) "butterfly" complexes are reported (o-tol = o-toluate, (mdea) 2- = doubly deprotonated N-methyldiethanolamine). The Co III ions are diamagnetic in these complexes. Analysis of the dc magnetic susceptibility measurements reveal antiferromagnetic exchange coupling between the two Ln III ions for all three complexes. ac magnetic susceptibility measurements reveal single-molecule magnet (SMM) behavior for complex 1, in the absence of an external magnetic field, with an anisotropy barrier U eff of 81.2 cm -1 , while complexes 2 and 3 exhibit field induced SMM behavior, with a U eff value of 34.2 cm -1 for 2. The barrier height for 3 could not be quantified. To understand the experimental observations, we performed DFT and ab initio CASSCF+RASSI-SO calculations to probe the single-ion properties and the nature and magnitude of the Ln III -Ln III magnetic coupling and to develop an understanding of the role the diamagnetic Co III ion plays in the magnetization relaxation. The calculations were able to rationalize the experimental relaxation data for all complexes and strongly suggest that the Co III ion is integral to the observation of SMM behavior in these systems. Thus, we explored further the effect that the diamagnetic Co III ions have on the magnetization blocking of 1. We did this by modeling a dinuclear {Dy III 2 } complex (1a), with the removal of the diamagnetic ions, and three complexes of the types {K I 2 Dy III 2 } (1b), {Zn II 2 Dy III 2 } (1c), and {Ti IV 2 Dy III 2 } (1d), each containing a different diamagnetic ion. We found that the presence of the diamagnetic ions results in larger negative charges on the bridging hydroxides (1b > 1c > 1 > 1d), in comparison to 1a (no diamagnetic ion), which reduces quantum tunneling of magnetization effects, allowing for more desirable SMM

New Sm(III) complexes as electronic-excitation donors of the Seta-632 squaraine dye

NASA Astrophysics Data System (ADS)

Egorova, A. V.; Leonenko, I. I.; Aleksandrova, D. I.; Skripinets, Yu. V.; Antonovich, V. P.; Obukhova, E. N.; Patsenker, L. D.

2015-07-01

We have found optimal formation conditions of new Sm(III) chelate complexes with derivatives of oxoquinolinecarboxylic acid ( L 1 and L 2) and determined their spectral-luminescent characteristics (the luminescence and luminescence excitation wavelength maxima and the luminescence lifetimes). We have revealed that the Seta-632 squaraine dye (a fluorescent label of proteins and other biological molecules) quenches the luminescence of complexes Sm(III)- L 1 and Sm(III)- L 2. The quenching of chelate complexes is caused by the Förster resonant electronic-excitation energy transfer (FRET) from the donor (Sm(III)- L 1 or Sm(III)- L 2) to the acceptor (Seta-632). In this case, the luminescence intensity of the Seta-632 dye in the presence of Sm(III)- L 1 and Sm(III)- L 2 increases by factors of 64 and 27, respectively. The values of the Förster radii ( R 0(Sm- L1) = 38 Å, R 0(Sm- L2) = 35 Å) and the overlap integrals of the luminescence spectra of the two energy donors with the absorption spectrum of the acceptor ( J Sm- L1 = 1.22 × 1012 M-1 cm-1 nm4 and J Sm- L2 = 1.06 × 1012 M-1 cm-1 nm4), which have been calculated from the luminescence quantum intensity of the donors and from the absorption spectrum of the acceptor and its molar absorption coefficient, have made it possible to characterize the Seta-632 dye as an efficient quencher of the luminescence of Sm(III) ions. We are the first to propose Sm(III)- L 1 and Sm(III)- L 2 chelate complexes as FRET donors.

The long story of mitochondrial DNA and respiratory complex I.

PubMed

Degli Esposti, Mauro

2017-01-01

This article examines the long story of the relationship between mitochondrial DNA (mtDNA) and respiratory complex I, NADH:Ubiquinone Oxidoreductase, from its beginning  in the genome of the bacterial endosymbiont which then evolved into the mitochondria of our cells. The story begins with the evolution of ancient forms of bacterial complex I into the Nuo14 complex I that was present in the alpha proteobacterial ancestor of mitochondria. The story then becomes complicated in the diversity of eukaryotic organisms that are currently recognized. Therefore, it does not have a clear end, because currently available information shows different situations of metabolic adaptation and gene loss, indicating cases of de-evolution of the original protonmotive complex into a system that may fundamentally assist [FeFe]-hydrogenases in re-oxidising metabolically produced NADH under anaerobic conditions. The history of complex I is thus a never ending story of molecular and physiological evolution producing new perspectives for studying the enzyme complex that occupies the largest proportion of mitochondrial DNA.

Sensitized terbium(III) macrocyclic-phthalimide complexes as luminescent pH switches.

PubMed

Chen, Gaoyun; Wardle, Nicholas J; Sarris, Jason; Chatterton, Nicholas P; Bligh, S W Annie

2013-10-21

Four new macrocyclic-phthalimide ligands were synthesised via the coupling of N-(3-bromopropyl)phthalimide either to cyclen (1,4,7,10-tetraazacyclododecane) itself or its carboxylate-functionalized analogues, and photophysical studies were carried out on their corresponding Tb(III) complexes in aqueous media as a function of pH. Luminescence intensities of Tb·L1a–Tb·L3a were in ‘switched off’ mode under acidic conditions (pH < 4), and were activated on progression to basic conditions as the phthalimido functions therein were hydrolysed to their corresponding phthalamates Tb·L1b–Tb·L3b. Emission of phthalamate-based macrocyclic Tb(III) complexes Tb·L1b–Tb·L3b was in ‘switched on’ mode between pH 4 and 11, exhibiting high quantum yields (Φ) and long lifetimes (τ) of the order of milliseconds at pH ~ 6. Tb(III) emissions were found to decline with increasing number of chromophores. The values of Φ and τ were 46% and 2.4 ms respectively for Tb·L1b at pH ~ 6 when activated. This is the best pH-dependent sensor based on a Tb(III) complex reported to date, benefiting from the macrocyclic architecture of the ligand.

Surface Complexation Modeling of Eu(III) and U(VI) Interactions with Graphene Oxide.

PubMed

Xie, Yu; Helvenston, Edward M; Shuller-Nickles, Lindsay C; Powell, Brian A

2016-02-16

Graphene oxide (GO) has great potential for actinide removal due to its extremely high sorption capacity, but the mechanism of sorption remains unclear. In this study, the carboxylic functional group and an unexpected sulfonate functional group on GO were characterized as the reactive surface sites and quantified via diffuse layer modeling of the GO acid/base titrations. The presence of sulfonate functional group on GO was confirmed using elemental analysis and X-ray photoelectron spectroscopy. Batch experiments of Eu(III) and U(VI) sorption to GO as the function of pH (1-8) and as the function of analyte concentration (10-100, 000 ppb) at a constant pH ≈ 5 were conducted; the batch sorption results were modeled simultaneously using surface complexation modeling (SCM). The SCM indicated that Eu(III) and U(VI) complexation to carboxylate functional group is the main mechanism for their sorption to GO; their complexation to the sulfonate site occurred at the lower pH range and the complexation of Eu(III) to sulfonate site are more significant than that of U(VI). Eu(III) and U(VI) facilitated GO aggregation was observed with high Eu(III) and U(VI) concentration and may be caused by surface charge neutralization of GO after sorption.

Intramolecular deactivation processes of electronically excited Lanthanide(III) complexes with organic acids of low molecular weight

NASA Astrophysics Data System (ADS)

Burek, Katja; Eidner, Sascha; Kuke, Stefanie; Kumke, Michael U.

2018-02-01

The luminescence of Lanthanide(III) complexes with different model ligands was studied under direct as well as sensitized excitation conditions. The research was performed in the context of studies dealing with deep-underground storages for high-level nuclear waste. Here, Lanthanide(III) ions served as natural analogues for Actinide(III) ions and the low-molecular weight organic ligands are present in clay minerals and furthermore, they were employed as proxies for building blocks of humic substances, which are important complexing molecules in the natural environment, e.g., in the far field of a repository site. Time-resolved luminescence spectroscopy was applied for a detailed characterization of Eu(III), Tb(III), Sm(III) and Dy(III) complexes in aqueous solutions. Based on the observed luminescence the ligands were tentatively divided into two groups (A, B). The luminescence of Lanthanide(III) complexes of group A was mainly influenced by an energy transfer to OH-vibrations. Lanthanide(III) complexes of group B showed ligand-related luminescence quenching, which was further investigated. To gain more information on the underlying quenching processes of group A and B ligands, measurements at different temperatures (77 K ≤ T ≤ 353 K) were performed and activation energies were determined based on an Arrhenius analysis. Moreover, the influence of the ionic strength between 0 M ≤ I ≤ 4 M on the Lanthanide(III) luminescence was monitored for different complexes, in order to evaluate the influence of specific conditions encountered in host rocks foreseen as potential repository sites.

Environmentally-relevant concentrations of Al(III) and Fe(III) cations induce aggregation of free DNA by complexation with phosphate group.

PubMed

Qin, Chao; Kang, Fuxing; Zhang, Wei; Shou, Weijun; Hu, Xiaojie; Gao, Yanzheng

2017-10-15

Environmental persistence of free DNA is influenced by its complexation with other chemical species and its aggregation mechanisms. However, it is not well-known how naturally-abundant metal ions, e.g., Al(III) and Fe(III), influence DNA aggregation. This study investigated aggregation behaviors of model DNA from salmon testes as influenced by metal cations, and elucidated the predominant mechanism responsible for DNA aggregation. Compared to monovalent (K + and Na + ) and divalent (Ca 2+ and Mg 2+ ) cations, Al(III) and Fe(III) species in aqueous solution caused rapid DNA aggregations. The maximal DNA aggregation occurred at 0.05 mmol/L Al(III) or 0.075 mmol/L Fe(III), respectively. A combination of atomic force microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy revealed that Al(III) and Fe(III) complexed with negatively charged phosphate groups to neutralize DNA charges, resulting in decreased electrostatic repulsion and subsequent DNA aggregation. Zeta potential measurements and molecular computation further support this mechanism. Furthermore, DNA aggregation was enhanced at higher temperature and near neutral pH. Therefore, DNA aggregation is collectively determined by many environmental factors such as ion species, temperature, and solution pH. Copyright © 2017 Elsevier Ltd. All rights reserved.

Probing Aspergillus niger glucose oxidase with pentacyanoferrate(III) aza- and thia-complexes.

PubMed

Kulys, J; Tetianec, L; Ziemys, A

2006-10-01

Complexes of pentacyanoferrate(III) and biologically relevant ligands, such as pyridine, pyrazole, imidazole, histidine, and other aza- and thia-heterocycles, were synthesized. Their spectral, electrochemical properties, electron exchange constants, electronic structure parameters, and reactivity with glucose oxidase from Aspergillus niger were determined. The formation of the complexes following ammonia replacement by the ligands was associated with the appearance of a new band of absorbance in the visible spectrum. The constants of the complexes formation calculated at a ligand-pentacyanoferrate(III) concentrations ratio of 10:1, were 7.5 x 10(-5), 7.7 x 10(-5), and 1.8 x 10(-3) s(-1) for benzotriazole, benzimidazole, and aminothiazole ligands, respectively. The complexes showed quasi-reversible redox conversion at a glassy carbon electrode. The redox potential of the complexes spanned the potential range from 70 to 240 mV vs. saturated calomel electrode (SCE) at pH7.2. For most of the complexes self-exchange constants (k(11)) were similar to or larger than that of hexacyanoferrate(III) (ferricyanide). The complexes containing pyridine derivatives and thia-heterocyclic ligands held a lower value of k(11) than that of ferricyanide. All complexes reacted with reduced glucose oxidase at pH7.2. The reactivity of the complex containing pyrazole was the largest in comparison to the rest of the complexes. Correlations between the complexes' reactivity and both the free energy of reaction and k(11) shows that the reactivity of pentacyanoferrates obeys the principles of Marcus's electron transfer theory. The obtained data suggest that large negative charges of the complexes decrease their reactivity.

Enhanced Respiratory Chain Supercomplex Formation in Response to Exercise in Human Skeletal Muscle.

PubMed

Greggio, Chiara; Jha, Pooja; Kulkarni, Sameer S; Lagarrigue, Sylviane; Broskey, Nicholas T; Boutant, Marie; Wang, Xu; Conde Alonso, Sonia; Ofori, Emmanuel; Auwerx, Johan; Cantó, Carles; Amati, Francesca

2017-02-07

Mitochondrial dysfunction is a hallmark of multiple metabolic complications. Physical activity is known to increase mitochondrial content in skeletal muscle, counteracting age-related decline in muscle function and protecting against metabolic and cardiovascular complications. Here, we investigated the effect of 4 months of exercise training on skeletal muscle mitochondria electron transport chain complexes and supercomplexes in 26 healthy, sedentary older adults. Exercise differentially modulated respiratory complexes. Complex I was the most upregulated complex and not stoichiometrically associated to the other complexes. In contrast to the other complexes, complex I was almost exclusively found assembled in supercomplexes in muscle mitochondria. Overall, supercomplex content was increased after exercise. In particular, complexes I, III, and IV were redistributed to supercomplexes in the form of I+III 2 +IV. Taken together, our results provide the first evidence that exercise affects the stoichiometry of supercomplex formation in humans and thus reveal a novel adaptive mechanism for increased energy demand. Copyright © 2017 Elsevier Inc. All rights reserved.

Spontaneous Tl(I)-to-Tl(III) oxidation in dynamic heterobimetallic Hg(II)/Tl(I) porphyrin complexes.

PubMed

Ndoyom, Victoria; Fusaro, Luca; Roisnel, Thierry; Le Gac, Stéphane; Boitrel, Bernard

2016-01-11

Strapped heterobimetallic Hg(II)/Tl(I) porphyrin complexes, with both metal ions bridged by the N-core in a dynamic way, undergo spontaneous Tl(I)-to-Tl(III) oxidation leading to a mono-Tl(III) complex and a mixed valence Tl(I)/Tl(III) bimetallic complex. It provides a new opportunity to tune metal ion translocations in bimetallic porphyrin systems.

Cannabinoid-Induced Changes in the Activity of Electron Transport Chain Complexes of Brain Mitochondria.

PubMed

Singh, Namrata; Hroudová, Jana; Fišar, Zdeněk

2015-08-01

The aim of this study was to investigate changes in the activity of individual mitochondrial respiratory chain complexes (I, II/III, IV) and citrate synthase induced by pharmacologically different cannabinoids. In vitro effects of selected cannabinoids on mitochondrial enzymes were measured in crude mitochondrial fraction isolated from pig brain. Both cannabinoid receptor agonists, Δ(9)-tetrahydrocannabinol, anandamide, and R-(+)-WIN55,212-2, and antagonist/inverse agonists of cannabinoid receptors, AM251, and cannabidiol were examined in pig brain mitochondria. Different effects of these cannabinoids on mitochondrial respiratory chain complexes and citrate synthase were found. Citrate synthase activity was decreased only by Δ(9)-tetrahydrocannabinol and AM251. Significant increase in the complex I activity was induced by anandamide. At micromolar concentration, all the tested cannabinoids inhibited the activity of electron transport chain complexes II/III and IV. Stimulatory effect of anandamide on activity of complex I may participate on distinct physiological effects of endocannabinoids compared to phytocannabinoids or synthetic cannabinoids. Common inhibitory effect of cannabinoids on activity of complex II/III and IV confirmed a non-receptor-mediated mechanism of cannabinoid action on individual components of system of oxidative phosphorylation.

Loss of Pink1 modulates synaptic mitochondrial bioenergetics in the rat striatum prior to motor symptoms: concomitant complex I respiratory defects and increased complex II-mediated respiration.

PubMed

Stauch, Kelly L; Villeneuve, Lance M; Purnell, Phillip R; Ottemann, Brendan M; Emanuel, Katy; Fox, Howard S

2016-12-01

Mutations in PTEN-induced putative kinase 1 (Pink1), a mitochondrial serine/threonine kinase, cause a recessive inherited form of Parkinson's disease (PD). Pink1 deletion in rats results in a progressive PD-like phenotype, characterized by significant motor deficits starting at 4 months of age. Despite the evidence of mitochondrial dysfunction, the pathogenic mechanism underlying disease due to Pink1-deficiency remains obscure. Striatal synaptic mitochondria from 3-month-old Pink1-deficient rats were characterized using bioenergetic and mass spectroscopy (MS)-based proteomic analyses. Striatal synaptic mitochondria from Pink1-deficient rats exhibit decreased complex I-driven respiration and increased complex II-mediated respiration compared with wild-type rats. MS-based proteomics revealed 69 of the 811 quantified mitochondrial proteins were differentially expressed between Pink1-deficient rats and controls. Down-regulation of several electron carrier proteins, which shuttle electrons to reduce ubiquinone at complex III, in the Pink1-knockouts suggests disruption of the linkage between fatty acid, amino acid, and choline metabolism and the mitochondrial respiratory system. These results suggest that complex II activity is increased to compensate for loss of electron transfer mechanisms due to reduced complex I activity and loss of electron carriers within striatal nerve terminals early during disease progression. This may contribute to the pathogenesis of PD. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ferromagnetic dinuclear mixed-valence Mn(II)/Mn(III) complexes: building blocks for the higher nuclearity complexes. structure, magnetic properties, and density functional theory calculations.

PubMed

Hänninen, Mikko M; Välivaara, Juha; Mota, Antonio J; Colacio, Enrique; Lloret, Francesc; Sillanpää, Reijo

2013-02-18

A series of six mixed-valence Mn(II)/Mn(III) dinuclear complexes were synthesized and characterized by X-ray diffraction. The reactivity of the complexes was surveyed, and structures of three additional trinuclear mixed-valence Mn(III)/Mn(II)/Mn(III) species were resolved. The magnetic properties of the complexes were studied in detail both experimentally and theoretically. All dinuclear complexes show ferromagnetic intramolecular interactions, which were justified on the basis of the electronic structures of the Mn(II) and Mn(III) ions. The large Mn(II)-O-Mn(III) bond angle and small distortion of the Mn(II) cation from the ideal square pyramidal geometry were shown to enhance the ferromagnetic interactions since these geometrical conditions seem to favor the orthogonal arrangement of the magnetic orbitals.

O-H bond oxidation by a monomeric Mn(III)-OMe complex.

PubMed

Wijeratne, Gayan B; Day, Victor W; Jackson, Timothy A

2015-02-21

Manganese-containing, mid-valent oxidants (Mn(III)-OR) that mediate proton-coupled electron-transfer (PCET) reactions are central to a variety of crucial enzymatic processes. The Mn-dependent enzyme lipoxygenase is such an example, where a Mn(III)-OH unit activates fatty acid substrates for peroxidation by an initial PCET. This present work describes the quantitative generation of the Mn(III)-OMe complex, [Mn(III)(OMe)(dpaq)](+) (dpaq = 2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8-yl-acetamidate) via dioxygen activation by [Mn(II)(dpaq)](+) in methanol at 25 °C. The X-ray diffraction structure of [Mn(III)(OMe)(dpaq)](+) exhibits a Mn-OMe group, with a Mn-O distance of 1.825(4) Å, that is trans to the amide functionality of the dpaq ligand. The [Mn(III)(OMe)(dpaq)](+) complex is quite stable in solution, with a half-life of 26 days in MeCN at 25 °C. [Mn(III)(OMe)(dpaq)](+) can activate phenolic O-H bonds with bond dissociation free energies (BDFEs) of less than 79 kcal mol(-1) and reacts with the weak O-H bond of TEMPOH (TEMPOH = 2,2'-6,6'-tetramethylpiperidine-1-ol) with a hydrogen/deuterium kinetic isotope effect (H/D KIE) of 1.8 in MeCN at 25 °C. This isotope effect, together with other experimental evidence, is suggestive of a concerted proton-electron transfer (CPET) mechanism for O-H bond oxidation by [Mn(III)(OMe)(dpaq)](+). A kinetic and thermodynamic comparison of the O-H bond oxidation reactivity of [Mn(III)(OMe)(dpaq)](+) to other M(III)-OR oxidants is presented as an aid to gain more insight into the PCET reactivity of mid-valent oxidants. In contrast to high-valent counterparts, the limited examples of M(III)-OR oxidants exhibit smaller H/D KIEs and show weaker dependence of their oxidation rates on the driving force of the PCET reaction with O-H bonds.

A new supramolecular chromium(III) complex: Synthesis, structural determination, optical study, magnetic and antibacterial activity

NASA Astrophysics Data System (ADS)

Dridi, Rihab; Dhieb, Cyrine; Cherni, Saoussen Namouchi; Boudjada, Nassira Chniba; Sadfi Zouaoui, Najla; Zid, Mohamed Faouzi

2018-01-01

A new chromium (III) complex 1,5-Naphthyridine Trans-diaquadioxalatochromate (III) dihydrate, had been synthesized by self-assembly of chromium (III) nitrate with oxalic acid and 1,5-Naphthyridine. The complex was characterized by X-ray diffraction, Fourier Transform Infrared spectroscopy, thermogravimetric analysis and UV-Visible spectroscopy. The crystal morphology was carried out using Bravais-Friedel-Donnay-Harker (BFDH) model. Single crystal X-Ray structure determination revealed that the complex posses two crystallographically independent Cr(III) centers. Each Cr(III) has a distorted octahedron geometry involving two axial O atoms from two water molecules and four equatorial O atoms from two oxalate dianions forming trans-[Cr(C2O4)2(H2O)2]- complex anions. The charge compensation is accomplished by the incorporation of 1,5-Naphthyridine cations. Connection between these entities is ensured by means of strong hydrogen bonds giving rise to 3D supramolecular architecture. Hirshfeld surface analysis and the related 2D fingerprint plots were used for decoding plausible intermolecular interactions in the crystal packing. The magnetic properties of the complex had been investigated and discussed in the context of its structure. The antimicrobial activity was evaluated by disc diffusion method highlighting an antagonistic effect of the synthesized complex against Gram-positive and Gram-negative species.

Biochemical investigation of yttrium(III) complex containing 1,10-phenanthroline: DNA binding and antibacterial activity.

PubMed

Khorasani-Motlagh, Mozhgan; Noroozifar, Meissam; Moodi, Asieh; Niroomand, Sona

2013-03-05

Characterization of the interaction between yttrium(III) complex containing 1,10-phenanthroline as ligand, [Y(phen)2Cl(OH2)3]Cl2⋅H2O, and DNA has been carried out by UV absorption, fluorescence spectra and viscosity measurements in order to investigate binding mode. The experimental results indicate that the yttrium(III) complex binds to DNA and absorption is decreasing in charge transfer band with the increase in amount of DNA. The binding constant (Kb) at different temperatures as well as thermodynamic parameters, enthalpy change (ΔH°) and entropy change (ΔS°), were calculated according to relevant fluorescent data and Vant' Hoff equation. The results of interaction mechanism studies, suggested that groove binding plays a major role in the binding of the complex and DNA. The activity of yttrium(III) complex against some bacteria was tested and antimicrobial screening tests shown growth inhibitory activity in the presence of yttrium(III) complex. Copyright © 2013 Elsevier B.V. All rights reserved.

Enhanced anti-cancer activities of a gold(III) pyrrolidinedithiocarbamato complex incorporated in a biodegradable metal-organic framework.

PubMed

Sun, Raymond Wai-Yin; Zhang, Ming; Li, Dan; Li, Mian; Wong, Alice Sze-Tsai

2016-10-01

An anti-cancer active gold(III) pyrrolidinedithiocarbamato complex [(PDTC)Au III Cl 2 ] (1) has been synthesized and characterized by means of X-ray crystallography. Compared to the pyrrolidinedithiocarbamate ligand itself, this gold(III) complex displays an up to 33-fold higher anti-cancer potency towards a panel of cancer cell lines including the cisplatin-resistant ovarian carcinoma cell line (A2780cis). As demonstrated by a set of Transwell® assay-based cytotoxicity experiments, incorporating this gold(III) complex in a zinc-based biodegradable metal-organic framework (MOF) displays a significant enhancement in anti-cancer activity towards A2780cis than the gold(III) complex alone. Copyright © 2016 Elsevier Inc. All rights reserved.

The First Seven-Coordinated Triiodo Complex of Rhenium(III)

NASA Astrophysics Data System (ADS)

Schoultz, X.; Gerber, T. I. A.; Betz, R.; Hosten, E. C.

2017-12-01

The reaction of cis-[ReO2I(P Ph 3)2] with tert-butyl isocyanide in benzene led to the isolation of the complex [ReI3(CN- t-Bu)3(P Ph 3)] ( 1). The complex is unusual since it contains bulky ligands with large cone angles, i.e. three iodides, three isocyanides with tert-butyl groups and a triphenylphosphine as ligands in a seven-coordinate geometry around the rhenium(III) metal ion.

In vivo anti-radiation activities of the Ulva pertusa polysaccharides and polysaccharide-iron(III) complex.

PubMed

Shi, Jinming; Cheng, Cuilin; Zhao, Haitian; Jing, Jing; Gong, Ning; Lu, Weihong

2013-09-01

Polysaccharides with different molecular weights were extracted from Ulva pertusa and fractionated by ultrafiltration. Iron(III) complex of the low molecular-weight U. pertusa polysaccharides were synthesized. Atomic absorption spectrum showed that the iron content of iron(III)-polysaccharide complex was 27.4%. The comparison between U. pertusa polysaccharides and their iron(III) complex showed that iron chelating altered the structural characteristics of the polysaccharides. The bioactivity analysis showed that polysaccharide with low molecular weight was more effective than polysaccharide with high molecular weight in protecting mice from radiation induced damages on bone marrow cells and immune system. Results also proved that the anti-radiation and anti-oxidative activity of iron(III) complex of low molecular-weight polysaccharides were not less than that of low molecular-weight polysaccharides. Copyright © 2013 Elsevier B.V. All rights reserved.

Two binuclear cyanide-bridged Cr(III)-Mn(III) complexes based-on [Cr(2,2'-bipy)(CN)4]- building block: synthesis, crystal structures and magnetic properties.

PubMed

Zhanga, Daopeng; Kong, Lingqian; Zhang, Hongyan

2015-01-01

Tetracyanide building block [Cr(2,2'-bipy)(CN)(4)]- and two bicompartimental Schiff-base based manganese(III) compounds have been employed to assemble cyanide-bridged heterometallic complexes, resulting in two cyanide-bridged CrIII-MnIII complexes: [Mn(L(1))(H(2)O)][Cr(2,2'-bipy)(CN)(4)]·CH(3)OH·2.5H(2)O (1) and [Mn(L(2))(H(2)O)][Cr(2,2'-bipy)(CN)(4)]·CH(3)OH·(3)H(2)O (2) (L1 = N,N'-(1,3-propylene)-bis(3-methoxysalicylideneiminate), L2 = N,N'-ethylene-bis(3-ethoxysalicylideneiminate)). Single X-ray diffraction analysis shows their similar cyanide-bridged binuclear structures, in which the cyanide precursor acting as monodentate ligand connects the manganese(III) ion. The binuclear complexes are self-complementary through coordinated aqua ligand and the free O4 compartment from the neighboring complex, giving H-bond linking dimer structure. Investigation over magnetic properties reveals the antiferromagnetic magnetic coupling between the cyanide-bridged Cr(III) and Mn(III) ions. A best-fit to the magnetic susceptibilities of these two complexes leads to the magnetic coupling constants J = -5.95 cm(-1), j = -0.61 cm(-1) (1) and J = -4.15 cm(-1), j = -0.57 cm(-1) (2), respectively.

Stereoselective Synthesis of Cyclometalated Iridium (III) Complexes: Characterization and Photophysical Properties

PubMed Central

Yang, Liangru; von Zelewsky, Alex; Nguyen, Huong P.; Muller, Gilles; Labat, Gaël; Stoeckli-Evans, Helen

2009-01-01

The stereoselective synthesis of a highly luminescent neutral Ir(III) complex comprising two bidentate chiral, cyclometalating phenylpyridine derivatives, and one acetylacetonate as ligands is described. The final complex and some intermediates were characterized by X-ray structural analysis, NMR-, CD-, and CPL-spectroscopy. PMID:20161195

Synthesis, spectroscopic and antimicrobial studies of La(III), Ce(III), Sm(III) and Y(III) Metformin HCl chelates.

PubMed

Refat, Moamen S; Al-Azab, Fathi M; Al-Maydama, Hussein M A; Amin, Ragab R; Jamil, Yasmin M S; Kobeasy, Mohamed I

2015-05-05

Metal complexes of Metformin hydrochloride were prepared using La(III), Ce(III), Sm(III) and Y(III). The resulting complexes were discussed and synthesized to serve as potential insulin-mimetic. Some physical properties and analytical data of the four complexes were checked. The elemental analysis shows that La(III), Ce(III) Sm(III) and Y(III) formed complexes with Metformin in 1:3 (metal:MF) molar ratio. All the synthesized complexes are white and possess high melting points. These complexes are soluble in dimethylsulfoxide and dimethylformamide, partially soluble in hot methanol and insoluble in water and some other organic solvents. From the spectroscopic (infrared, UV-vis and florescence), effective magnetic moment and elemental analyses data, the formula structures are suggested. The results obtained suggested that Metformin reacted with metal ions as a bidentate ligand through its two imino groups. The molar conductance measurements proved that the Metformin complexes are slightly electrolytic in nature. The kinetic thermodynamic parameters such as: E(∗), ΔH(∗), ΔS(∗) and ΔG(∗) were estimated from the DTG curves. The antibacterial evaluations of the Metformin and their complexes were also performed against some gram positive, negative bacteria as well as fungi. Copyright © 2015 Elsevier B.V. All rights reserved.

[Effects of different hypoxic training modes on activities of mitochondrial antioxidants and respiratory chain complex in skeletal muscle after exhaustive running in rat].

PubMed

Li, Jie; Zhang, Yao-Bin

2011-02-25

The present study was aimed to investigate the effect of hypoxic training on mitochondrial antioxidants and activities of respiratory chain complexes in mitochondria of skeletal muscle in rats. Forty healthy male Wistar rats were randomized to 5 groups (n=8): living low-training low (LoLo), living high-training high (HiHi), living high-training low (HiLo), living low-training high (LoHi), and living high-exercise high-training low (HiHiLo). All the animals were subjected to 5-week training in normoxic (atmospheric pressure=632 mmHg, altitude of about 1 500 m) or hypoxic environment (atmospheric pressure=493 mmHg, simulated altitude of about 3 500 m). Before exhaustive running, the animals stayed in normoxia for 3 d. Skeletal muscles were prepared immediately after exhaustive running. Muscle mitochondria were extracted by differential centrifugation. Spectrophotometric analysis was used to evaluate activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), malondialdehyde (MDA) level and respiratory chain complex (C) I-III activities in muscle homogenate and mitochondria. Results showed that SOD, GSH-Px, CAT activities and MDA level in skeletal muscle homogenate in HiHi and HiHiLo groups were significantly increased (P<0.05 or P<0.01) compared with those in LoLo group. Muscle mitochondrial MDA level in HiHi and HiHiLo groups was significantly lower (P<0.01), while activities of SOD, GSH-Px and CAT were remarkably higher (P<0.01) than those in LoLo group. Meanwhile, C I-III activities in HiHi and HiHiLo groups were increased significantly (P<0.01), and C II activity in HiLo group also was increased remarkably (P<0.01) compared with those in LoLo group. These results suggest that HiHiLo might be an ideal hypoxic training mode.

Trifluoromethyl-Substituted Iridium(III) Complexes: From Photophysics to Photooxidation of a Biological Target.

PubMed

Bevernaegie, Robin; Marcélis, Lionel; Laramée-Milette, Baptiste; De Winter, Julien; Robeyns, Koen; Gerbaux, Pascal; Hanan, Garry S; Elias, Benjamin

2018-02-05

Photodynamic therapeutic agents are of key interest in developing new strategies to develop more specific and efficient anticancer treatments. In comparison to classical chemotherapeutic agents, the activity of photodynamic therapeutic compounds can be finely controlled thanks to the light triggering of their photoreactivity. The development of type I photosensitizing agents, which do not rely on the production of ROS, is highly desirable. In this context, we developed new iridium(III) complexes which are able to photoreact with biomolecules; namely, our Ir(III) complexes can oxidize guanine residues under visible light irradiation. We report the synthesis and extensive photophysical characterization of four new Ir(III) complexes, [Ir(ppyCF 3 ) 2 (N^N)] + [ppyCF 3 = 2-(3,5-bis(trifluoromethyl)phenyl)pyridine) and N^N = 2,2'-dipyridyl (bpy); 2-(pyridin-2-yl)pyrazine (pzpy); 2,2'-bipyrazine (bpz); 1,4,5,8-tetraazaphenanthrene (TAP)]. In addition to an extensive experimental and theoretical study of the photophysics of these complexes, we characterize their photoreactivity toward model redox-active targets and the relevant biological target, the guanine base. We demonstrate that photoinduced electron transfer takes place between the excited Ir(III) complex and guanine which leads to the formation of stable photoproducts, indicating that the targeted guanine is irreversibly damaged. These results pave the way to the elaboration of new type I photosensitizers for targeting cancerous cells.

Biological activity of Fe(III) aquo-complexes towards ferric chelate reductase (FCR).

PubMed

Escudero, Rosa; Gómez-Gallego, Mar; Romano, Santiago; Fernández, Israel; Gutiérrez-Alonso, Ángel; Sierra, Miguel A; López-Rayo, Sandra; Nadal, Paloma; Lucena, Juan J

2012-03-21

In this study we have obtained experimental evidence that confirms the high activity of aquo complexes III and IV towards the enzyme FCR, responsible for the reduction of Fe(III) to Fe(II) in the process of iron acquisition by plants. The in vivo FCR assays in roots of stressed cucumber plants have shown a higher efficiency of the family of complexes III and a striking structure-activity relationship with the nature of the substituent placed in a phenyl group far away from the metal center. The results obtained in this work demonstrate that all the aquo compounds tested interact efficiently with the enzyme FCR and hence constitute a new concept of iron chelates that could be of great use in agronomy.

Preparation of manganese(II), chromium(III) and ferric(III) oxides nanoparticles in situ metal citraconate complexes frameworks

NASA Astrophysics Data System (ADS)

Refat, Moamen S.

2014-12-01

The new reactions of some divalent and trivalent transition metal ions (Mn(II), Cr(III), and Fe(III)) with citraconic acid has been studied. The obtained results indicate the formation of citraconic acid compounds with molar ratio of metal to citraconic acid of 2:2 or 2:3 with general formulas Mn2(C5H4O4)2 or M2(C5H4O4)3ṡnH2O where n = 6 for Cr, and Fe(III). The thermal decomposition of the crystalline solid complexes was investigated. The IR spectra of citraconate suggested that the carboxylic groups are bidentatically bridging and chelating. In the course of decomposition the complexes are dehydrated and then decompose either directly to oxides in only one step or with intermediate formation of oxocarbonates. This proposal dealing the preparation of MnO2, Fe2O3 and Cr2O3 nanoparticles. The crystalline structure of oxide products were checked by X-ray powder diffraction (XRD), and the morphology of particles by scanning electron microscopy (SEM).

Deficiency of PHB complex impairs respiratory supercomplex formation and activates mitochondrial flashes.

PubMed

Jian, Chongshu; Xu, Fengli; Hou, Tingting; Sun, Tao; Li, Jinghang; Cheng, Heping; Wang, Xianhua

2017-08-01

Prohibitins (PHBs; prohibitin 1, PHB1 or PHB, and prohibitin 2, PHB2) are evolutionarily conserved and ubiquitously expressed mitochondrial proteins. PHBs form multimeric ring complexes acting as scaffolds in the inner mitochondrial membrane. Mitochondrial flashes (mitoflashes) are newly discovered mitochondrial signaling events that reflect electrical and chemical excitations of the organelle. Here, we investigate the possible roles of PHBs in the regulation of mitoflash signaling. Downregulation of PHBs increases mitoflash frequency by up to 5.4-fold due to elevated basal reactive oxygen species (ROS) production in the mitochondria. Mechanistically, PHB deficiency impairs the formation of mitochondrial respiratory supercomplexes (RSCs) without altering the abundance of individual respiratory complex subunits. These impairments induced by PHB deficiency are effectively rescued by co-expression of PHB1 and PHB2, indicating that the multimeric PHB complex acts as the functional unit. Furthermore, downregulating other RSC assembly factors, including SCAFI (also known as COX7A2L), RCF1a (HIGD1A), RCF1b (HIGD2A), UQCC3 and SLP2 (STOML2), all activate mitoflashes through elevating mitochondrial ROS production. Our findings identify the PHB complex as a new regulator of RSC formation and mitoflash signaling, and delineate a general relationship among RSC formation, basal ROS production and mitoflash biogenesis. © 2017. Published by The Company of Biologists Ltd.

Structural and catalytic properties of some azo-rhodanine Ruthenium(III) complexes

NASA Astrophysics Data System (ADS)

Shoair, A. F.; El-Bindary, A. A.; Abd El-Kader, M. K.

2017-09-01

Novel azo-rhodanine ruthenium(III) complexes of the type trans-[Ru(Ln)2(AsPh3)2]Cl (Ln = monobasic bidentate anions of 5-(4‧-methoxyphenylazo)-3-phenylamino-2-thioxothiazolidin-4-one (HL1), 5-(phenylazo)-3-phenylamino-2-thioxothiazolidin-4-one (HL2) and 5-(4‧-chlorophenylazo)-3-phenylamino-2-thioxothiazolidin-4-one (HL3); AsPh3 = triphenylarsine) have been synthesized and characterized by elemental analysis, spectroscopic (IR, 1H NMR and UV-VIS), magnetic, X-ray diffraction, mass spectra and thermal analysis techniques. These techniques confirm the formation of octahedral ruthenium(III) complexes. The Ru(III) complexes were tested as a catalysts for the oxidation of benzyl alcohol to benzaldehyde with N-methylmorpholine-N-oxide as a co-oxidant. The effect of time, temperature, and solvent were also studied and the mechanism of this catalytic oxidation reaction is suggested. Molecular docking was used to predict the binding between azo rhodanine derivatives (HLn) with the receptor of 3qum- immune system receptor of human prostate specific antigen (PSA) in a Fab sandwich with a high affinity and a PCa selective antibody.

Management of complex glottic stenosis in children with recurrent respiratory papillomatosis.

PubMed

Siegel, Bianca; Smith, Lee P

2013-10-01

To describe our management of complex glottic stenosis in tracheotomy dependent children with severe recurrent respiratory papillomatosis. Retrospective chart review at a tertiary care children's hospital. Three children with complex glottic stenosis secondary to severe recurrent respiratory papillomatosis were treated at our institution since 2011. Two patients had complete stenosis, and the third had near-complete stenosis. Two patients were managed using balloon dilation alone, and the third also underwent laryngotracheal reconstruction with posterior costal cartilage grafting. Two patients have been successfully decannulated and the third has been tolerating continuous tracheotomy capping for greater than twelve months. All three patients underwent aggressive debridement of papillomatosis and balloon dilation every 4-6 weeks until their burden of disease was controlled. In two patients, the glottic airway was patent, and the third continued to have complete restenosis between procedures and required laryngotracheoplasty with multiple post-operative dilation procedures to establish an adequate glottic airway. Severe laryngeal stenosis is a well-described complication of recurrent respiratory papillomatosis, but its management is not well-defined. Aggressive management of papillomatosis with frequent debridement is critical in successfully managing laryngeal stenosis. Balloon dilation alone may be surprisingly effective in these patients, and laryngotracheoplasty can be used as an adjunct procedure in those patients who fail balloon dilation. Given the quality of life issues and concerns regarding distal spread of disease with tracheotomies in these patients, we feel that aggressive management and early decannulation is in the patient's best interest. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Theoretical Modeling of the Magnetic Behavior of Thiacalix[4]arene Tetranuclear Mn(II)2Gd(III)2 and Co(II)2Eu(III)2 Complexes.

PubMed

Aldoshin, Sergey M; Sanina, Nataliya A; Palii, Andrew V; Tsukerblat, Boris S

2016-04-04

In view of a wide perspective of 3d-4f complexes in single-molecule magnetism, here we propose an explanation of the magnetic behavior of the two thiacalix[4]arene tetranuclear heterometallic complexes Mn(II)2Gd(III)2 and Co(II)2Eu(III)2. The energy pattern of the Mn(II)2Gd(III)2 complex evaluated in the framework of the isotropic exchange model exhibits a rotational band of the low-lying spin excitations within which the Landé intervals are affected by the biquadratic spin-spin interactions. The nonmonotonic temperature dependence of the χT product observed for the Mn(II)2Gd(III)2 complex is attributed to the competitive influence of the ferromagnetic Mn-Gd and antiferromagnetic Mn-Mn exchange interactions, the latter being stronger (J(Mn, Mn) = -1.6 cm(-1), Js(Mn, Gd) = 0.8 cm(-1), g = 1.97). The model for the Co(II)2Eu(III)2 complex includes uniaxial anisotropy of the seven-coordinate Co(II) ions and an isotropic exchange interaction in the Co(II)2 pair, while the Eu(III) ions are diamagnetic in their ground states. Best-fit analysis of χT versus T showed that the anisotropic contribution (arising from a large zero-field splitting in Co(II) ions) dominates (weak-exchange limit) in the Co(II)2Eu(III)2 complex (D = 20.5 cm(-1), J = -0.4 cm(-1), gCo = 2.22). This complex is concluded to exhibit an easy plane of magnetization (arising from the Co(II) pair). It is shown that the low-lying part of the spectrum can be described by a highly anisotropic effective spin-(1)/2 Hamiltonian that is deduced for the Co(II)2 pair in the weak-exchange limit.

Mn(II) Oxidation by the Multicopper Oxidase Complex Mnx: A Coordinated Two-Stage Mn(II)/(III) and Mn(III)/(IV) Mechanism.

PubMed

Soldatova, Alexandra V; Romano, Christine A; Tao, Lizhi; Stich, Troy A; Casey, William H; Britt, R David; Tebo, Bradley M; Spiro, Thomas G

2017-08-23

The bacterial manganese oxidase MnxG of the Mnx protein complex is unique among multicopper oxidases (MCOs) in carrying out a two-electron metal oxidation, converting Mn(II) to MnO 2 nanoparticles. The reaction occurs in two stages: Mn(II) → Mn(III) and Mn(III) → MnO 2 . In a companion study , we show that the electron transfer from Mn(II) to the low-potential type 1 Cu of MnxG requires an activation step, likely forming a hydroxide bridge at a dinuclear Mn(II) site. Here we study the second oxidation step, using pyrophosphate (PP) as a Mn(III) trap. PP chelates Mn(III) produced by the enzyme and subsequently allows it to become a substrate for the second stage of the reaction. EPR spectroscopy confirms the presence of Mn(III) bound to the enzyme. The Mn(III) oxidation step does not involve direct electron transfer to the enzyme from Mn(III), which is shown by kinetic measurements to be excluded from the Mn(II) binding site. Instead, Mn(III) is proposed to disproportionate at an adjacent polynuclear site, thereby allowing indirect oxidation to Mn(IV) and recycling of Mn(II). PP plays a multifaceted role, slowing the reaction by complexing both Mn(II) and Mn(III) in solution, and also inhibiting catalysis, likely through binding at or near the active site. An overall mechanism for Mnx-catalyzed MnO 2 production from Mn(II) is presented.

Interaction of curcumin with Al(III) and its complex structures based on experiments and theoretical calculations

NASA Astrophysics Data System (ADS)

Jiang, Teng; Wang, Long; Zhang, Sui; Sun, Ping-Chuan; Ding, Chuan-Fan; Chu, Yan-Qiu; Zhou, Ping

2011-10-01

Curcumin has been recognized as a potential natural drug to treat the Alzheimer's disease (AD) by chelating baleful metal ions, scavenging radicals and preventing the amyloid β (Aβ) peptides from the aggregation. In this paper, Al(III)-curcumin complexes with Al(III) were synthesized and characterized by liquid-state 1H, 13C and 27Al nuclear magnetic resonance (NMR), mass spectroscopy (MS), ultraviolet spectroscopy (UV) and generalized 2D UV-UV correlation spectroscopy. In addition, the density functional theory (DFT)-based UV and chemical shift calculations were also performed to view insight into the structures and properties of curcumin and its complexes. It was revealed that curcumin could interact strongly with Al(III) ion, and form three types of complexes under different molar ratios of [Al(III)]/[curcumin], which would restrain the interaction of Al(III) with the Aβ peptide, reducing the toxicity effect of Al(III) on the peptide.

Mussel-Inspired Protein Nanoparticles Containing Iron(III)-DOPA Complexes for pH-Responsive Drug Delivery.

PubMed

Kim, Bum Jin; Cheong, Hogyun; Hwang, Byeong Hee; Cha, Hyung Joon

2015-06-15

A novel bioinspired strategy for protein nanoparticle (NP) synthesis to achieve pH-responsive drug release exploits the pH-dependent changes in the coordination stoichiometry of iron(III)-3,4-dihydroxyphenylalanine (DOPA) complexes, which play a major cross-linking role in mussel byssal threads. Doxorubicin-loaded polymeric NPs that are based on Fe(III)-DOPA complexation were thus synthesized with a DOPA-modified recombinant mussel adhesive protein through a co-electrospraying process. The release of doxorubicin was found to be predominantly governed by a change in the structure of the Fe(III)-DOPA complexes induced by an acidic pH value. It was also demonstrated that the fabricated NPs exhibited effective cytotoxicity towards cancer cells through efficient cellular uptake and cytosolic release. Therefore, it is anticipated that Fe(III)-DOPA complexation can be successfully utilized as a new design principle for pH-responsive NPs for diverse controlled drug-delivery applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gd(III) complexes for electron-electron dipolar spectroscopy: Effects of deuteration, pH and zero field splitting.

PubMed

Garbuio, Luca; Zimmermann, Kaspar; Häussinger, Daniel; Yulikov, Maxim

2015-10-01

Spectral parameters of Gd(III) complexes are intimately linked to the performance of the Gd(III)-nitroxide or Gd(III)-Gd(III) double electron-electron resonance (DEER or PELDOR) techniques, as well as to that of relaxation induced dipolar modulation enhancement (RIDME) spectroscopy with Gd(III) ions. These techniques are of interest for applications in structural biology, since they can selectively detect site-to-site distances in biomolecules or biomolecular complexes in the nanometer range. Here we report relaxation properties, echo detected EPR spectra, as well as the magnitude of the echo reduction effect in Gd(III)-nitroxide DEER for a series of Gadolinium(III) complexes with chelating agents derived from tetraazacyclododecane. We observed that solvent deuteration does not only lengthen the relaxation times of Gd(III) centers but also weakens the DEER echo reduction effect. Both of these phenomena lead to an improved signal-to-noise ratios or, alternatively, longer accessible distance range in pulse EPR measurements. The presented data enrich the knowledge on paramagnetic Gd(III) chelate complexes in frozen solutions, and can help optimize the experimental conditions for most types of the pulse measurements of the electron-electron dipolar interactions. Copyright © 2015 Elsevier Inc. All rights reserved.

Synthesis, characterization and electrochemistry studies of iron(III) complex with curcumin ligand.

PubMed

Özbolat, Gülüzar; Yegani, Arash Alizadeh; Tuli, Abdullah

2018-05-11

Iron overload is a serious clinical condition for humans and is a key target in drug development. The aim of this study was to investigate the coordination of iron(III) ions with curcumin ligand that may be used in the treatment of iron overload. Iron(III) complex of curcumin was synthesized and structurally characterized in its solid and solution state by FT-IR, UV-Vis, elemental analysis, and magnetic susceptibility. Electrochemical behaviour of the ligand and the complexes were examined using cyclic voltammetry. The cytotoxic activities of the ligand and the iron(III) complex were evaluated by the MTT assay. Curcumin reacted with iron in high concentrations at physiological pH at room temperature. Subsequently, a brown-red complex was formed. Data regarding magnetic susceptibility showed that the complexes with a 1:2 (metal/ligand) mole ratio had octahedral geometry. The complex showed higher anti-oxidant effect towards the cell line ECV304 at IC 50 values of 4.83 compared to curcumin. The complex exhibited very high cytotoxic activity and showed a cytotoxic effect that was much better than that of the ligand. The potentials for redox were calculated as 0.180 V and 0.350 V, respectively. The electrochemistry studies showed that Fe 3+ /Fe 2+ couple redox process occurred at low potentials. This value was within the range of compounds that are expected to show superoxide dismutase activity. This finding indicates that the iron complex is capable of removing free radicals. The observed cytotoxicity could be pursued to obtain a potential drug. Further studies investigating the use of curcumin for this purpose are needed. © 2018 John Wiley & Sons Australia, Ltd.

Kinetics of the reduction of cobalt(III) amine complexes by 1-hydroxy-1-methylethyl radicals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kusaba, K.; Ogino, Hiroshi; Bakac, A.

1989-03-08

In order to better understand the rate constants for the reduction of several cobalt complexes by 1-hydroxy-1-methylene radicals ({sup {sm bullet}}C(CH{sub 3}){sub 2}OH), the reactions of {sup {sm bullet}}(CH{sub 3}){sub 2}OH with several cobalt(III) complexes of bidentate amines have been studied. The Marcus-Hush theory was deemed the most appropriate for analysis of the kinetic data. The correlation between the kinetics of the reduction of the Co(III) amines by C(CH{sub 3}){sub 2}OH and the reduction of the first d-d band for Co(III) complexes is discussed. 21 refs., 2 figs., 1 tab.

Synthesis and structures of a pincer-type rhodium(iii) complex: reactivity toward biomolecules.

PubMed

Milutinović, Milan M; Bogojeski, Jovana V; Klisurić, Olivera; Scheurer, Andreas; Elmroth, Sofi K C; Bugarčić, Živadin D

2016-10-04

A novel rhodium(iii) complex [Rh III (H 2 L tBu )Cl 3 ] (1) (H 2 L tBu = 2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)pyridine) containing a pincer type, tridentate nitrogen-donor chelate system was synthesized. Single crystal X-ray structure analysis revealed that 1 crystallizes in the orthorhombic space group Pbcn with a = 20.7982(6), b = 10.8952(4), c = 10.9832(4) Å, V = 2488.80(15) Å 3 , and eight molecules in the unit cell. The rhodium center in the complex [Rh III (H 2 L tBu )Cl 3 ] (1) is coordinated in a slightly distorted octahedral geometry by the tridentate N,N,N-donor and three chloro ligands, adopting a mer arrangement with an essentially planar ligand skeleton. Due to the tridentate coordination of the N,N,N-donor, the central nitrogen atom N1 is located closer to the Rh III center. The reactivity of the synthesized complex toward small biomolecules (l-methionine (l-Met), guanosine-5'-monophosphate (5'-GMP), l-histidine (l-His) and glutathione (GSH)) and to a series of duplex DNAs and RNA was investigated. The order of reactivity of the studied small biomolecules is: 5'-GMP > GSH > l-Met > l-His. Duplex RNA reacts faster with the [Rh III (H 2 L tBu )Cl 3 ] complex than duplex DNA, while shorter duplex DNA (15mer GG) reacts faster compared with 22mer GG duplex DNA. In addition, a higher reactivity is achieved with a DNA duplex with a centrally located GG-sequence than with a 22GTG duplex DNA, in which the GG-sequence is separated by a T base. Furthermore, the interaction of this metal complex 1 with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) was examined by absorption (UV-Vis) and emission spectral studies (EthBr displacement studies). Overall, the studied complex exhibited good DNA and BSA interaction ability.

^1H NMR studies of the diamagnetic gallium (III) and paramagnetic iron (III) complexes of a chiral macrobicyclic ligand of bicapped tris (binaphtol) type

NASA Astrophysics Data System (ADS)

Baret, P.; Beaujolais, V.; Bougault, C.; Gaude, D.; Pierre, J.-L.

1998-01-01

^1H NMR studies of the diamagnetic gallium (III) and paramagnetic iron (III) complexes of a chiral macrobicyclic ligand of bicapped tris (binaphtol) type are described. The study of the gallium complex emphasizes: (i) that the inversion of the octahedral center is not observed and: (ii) the absence of exchange between free ligand and complex, at room temperature. In the case of the iron complex, assignments of the hyperfine shifted resolved resonances are achieved, based on temperature-behavior studies, which evidence the D3 symmetry of the complex. These assignments are in complete agreement with measured T1 values and proton-to-iron distances obtained from molecular modelling. Les complexes du gallium (III) et du fer (III) d'un ligand macrobicyclique chiral impliquant trois sous-unités de type binaphtol sont étudiés en RMN du proton en solution méthanolique. L'étude du complexe (diamagnétique) du gallium permet de montrer que le complexe : (i) ne subit pas d'inversion de la configuration (Δ/Λ) du site octaédrique et : (ii) qu'il n'y a pas d'échange entre ligand libre et complexe à la température ambiante. L'évolution du spectre du complexe paramagnétique du fer avec la température permet une attribution des protons du ligand et met en évidence la symétrie D3 du complexe. Une bonne corrélation est obtenue entre la distance fer-proton (donnée par la modélisation moléculaire) et le T1 du proton considéré.

Synthesis, spectroscopic, thermal and antimicrobial studies of neodymium(III) and samarium(III) complexes derived from tetradentate ligands containing N and S donor atoms

NASA Astrophysics Data System (ADS)

Ain, Qurratul; Pandey, S. K.; Pandey, O. P.; Sengupta, S. K.

2015-04-01

Trivalent lanthanide complexes of the type [Ln(L)Cl(H2O)2] (where Ln = Nd(III) or Sm(III) and LH2 = Schiff bases derived by the condensation of 3-(phenyl/substitutedphenyl)-4-amino-5-mercapto-1,2,4-triazole with diacetyl/benzil) have been synthesized by the reactions of anhydrous lanthanide(III) chloride with Schiff bases in methanol. The structures of the complexes have been proposed on the basis of elemental analysis, electrical conductance, magnetic moment, spectroscopic measurements (IR, 1H, 13C NMR and UV-vis spectra) and X-ray diffraction studies. The spectral data reveal that the Schiff base ligands behave as dibasic tetradentate chelating agents having coordination sites at two thiol sulfur atoms and two azomethine nitrogen atoms. The presence of coordinated water in metal complexes was confirmed by thermal and IR data of the complexes. All the Schiff bases and their metal complexes have also been screened for their antibacterial activity against Bacillus subtilis, Staphylococcus aureus and antifungal activities against Aspergillus niger, Curvularia pallescens and Colletotrichum capsici.

Polymer-Supported Optically Active fac(S)-Tris(thiotato)rhodium(III) Complex for Sulfur-Bridging Reaction With Precious Metal Ions.

PubMed

Aizawa, Sen-Ichi; Tsubosaka, Soshi

2016-01-01

The optically active mixed-ligand fac(S)-tris(thiolato)rhodium(III) complexes, ΔL -fac(S)-[Rh(aet)2 (L-cys-N,S)](-) (aet = 2-aminoethanethiolate, L-cys = L-cysteinate) () and ΔLL -fac(S)-[Rh(aet)(L-cys-N,S)2 ](2-) were newly prepared by the equatorial preference of the carboxyl group in the coordinated L-cys ligand. The amide formation reaction of with 1,10-diaminodecane and polyallylamine gave the diamine-bridged dinuclear Rh(III) complex and the single-chain polymer-supported Rh(III) complex with retention of the ΔL configuration of , respectively. These Rh(III) complexes reacted with Co(III) or Co(II) to give the linear-type trinuclear structure with the S-bridged Co(III) center and the two Δ-Rh(III) terminal moieties. The polymer-supported Rh(III) complex was applied not only to the CD spectropolarimetric detection and determination of a trace of precious metal ions such as Au(III), Pt(II), and Pd(II) but also to concentration and extraction of these metal ions into the solid polymer phase. Chirality 28:85-91, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Well-Defined Chiral Gold(III) Complexes: New Opportunities in Asymmetric Catalysis.

PubMed

Rodriguez, Jessica; Bourissou, Didier

2018-01-08

Square way to heaven: As a result of their square-planar geometry, the reactive site of gold(III) complexes is much closer to the ancillary ligands. This offers new perspectives in asymmetric catalysis, as recently evidenced by the groups of Wong and Toste with well-defined chiral complexes. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

New Insights into Structure and Luminescence of Eu III and Sm III Complexes of the 3,4,3-LI(1,2-HOPO) Ligand

DOE PAGES

Daumann, Lena J.; Tatum, David S.; Snyder, Benjamin E. R.; ...

2015-01-21

We report the preparation and new insight into photophysical properties of luminescent hydroxypyridonate complexes [M IIIL] - (M = Eu or Sm) of the versatile 3,4,3-LI(1,2-HOPO) ligand (L). We report the crystal structure of this ligand with EuIII as well as insights into the coordination behavior and geometry in solution by using magnetic circular dichroism. In addition TD-DFT calculations were used to examine the excited states of the two different chromophores present in the 3,4,3-LI(1,2-HOPO) ligand. We find that the Eu III and Sm III complexes of this ligand undergo a transformation after in situ preparation to yield complexes withmore » higher quantum yield (QY) over time. We propose that the lower QY in the in situ complexes is not only due to water quenching but could also be due to a lower degree of f-orbital overlap (in a kinetic isomer) as indicated by magnetic circular dichroism measurements.« less

C-H activation in Ir(III) and N-demethylation in Pt(II) complexes with mesoionic carbene ligands: examples of monometallic, homobimetallic and heterobimetallic complexes.

PubMed

Maity, Ramananda; Tichter, Tim; van der Meer, Margarethe; Sarkar, Biprajit

2015-11-14

Mononuclear Pt(II) and the first dinuclear Pt(II) complexes along with a cyclometalated heterobimetallic Ir(III)/Pd(II) complex bearing mesoionic carbene donor ligands are presented starting from the same bis-triazolium salt. The mononuclear Pt(II) complex possesses a free triazole moiety which is generated from the corresponding triazolium salt through an N-demethylation reaction, whereas the mononuclear Ir(III) complex features an unreacted triazolium unit.

Synthesis, structural characterization and photoluminescence properties of a novel La(III) complex

NASA Astrophysics Data System (ADS)

Köse, Muhammet; Ceyhan, Gökhan; Atcı, Emine; McKee, Vickie; Tümer, Mehmet

2015-05-01

In this study, a novel La(III) complex [La(H2L)2(NO3)3(MeOH)] of a Schiff base ligand was synthesized and characterized by spectroscopic and analytical methods. Single crystals of the complex suitable for X-ray diffraction study were obtained by slow diffusion of diethyl ether into a MeOH solution of the complex which was found to crystallise as [La(H2L)2(NO3)3(MeOH)]ṡ2MeOHṡH2O. The structure was solved in monoclinic crystal system, P21/n space group with unit cell parameters a = 10.5641(11), b = 12.6661(16), c = 16.0022(17) Å, α = 67.364(2), β = 83.794(2)°, γ = 70.541(2)°, V = 1862.9(4) Å3 and Z = 2 with R final value of 0.526. In the complex, the La(III) ion is ten-coordinated by O atoms, five of which come from three nitrate ions, four from the two Schiff base ligands and one from MeOH oxygen atom. The Schiff base ligands in the structure are in a zwitter ion form with the phenolic H transferred to the imine N atom. Thermal properties of the La(III) complex were examined by thermogravimetric analysis and the complex was found to be thermally stable up to 310 °C. The Schiff base ligand and its La(II) complex were screened for their in vitro antimicrobial activity against Bacillus megaterium, Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus (Gram positive bacteria), Klebsiella pneumonia, Escherichia coli, Enterobacter aerogenes, Pseudomonas aeruginosa (Gram negative bacteria), Candida albicans,Yarrowia lipolytica (fungus) and Saccharomyces cerevisiae (yeast). The complex shows more antimicrobial activity than the free ligand.

Calculation of genomic predicted transmitting abilities for bovine respiratory disease complex in Holsteins

USDA-ARS?s Scientific Manuscript database

Bovine Respiratory Disease Complex is a disease that is very costly to the dairy industry. Genomic selection may be an effective tool to improve host resistance to the pathogens that cause this disease. Use of genomic predicted transmitting abilities (GPTA) for selection has had a dramatic effect on...

Four-dimensional computed tomography based respiratory-gated radiotherapy with respiratory guidance system: analysis of respiratory signals and dosimetric comparison.

PubMed

Lee, Jung Ae; Kim, Chul Yong; Yang, Dae Sik; Yoon, Won Sup; Park, Young Je; Lee, Suk; Kim, Young Bum

2014-01-01

To investigate the effectiveness of respiratory guidance system in 4-dimensional computed tomography (4 DCT) based respiratory-gated radiation therapy (RGRT) by comparing respiratory signals and dosimetric analysis of treatment plans. The respiratory amplitude and period of the free, the audio device-guided, and the complex system-guided breathing were evaluated in eleven patients with lung or liver cancers. The dosimetric parameters were assessed by comparing free breathing CT plan and 4 DCT-based 30-70% maximal intensity projection (MIP) plan. The use of complex system-guided breathing showed significantly less variation in respiratory amplitude and period compared to the free or audio-guided breathing regarding the root mean square errors (RMSE) of full inspiration (P = 0.031), full expiration (P = 0.007), and period (P = 0.007). The dosimetric parameters including V(5 Gy), V(10 Gy), V(20 Gy), V(30 Gy), V(40 Gy), and V(50 Gy) of normal liver or lung in 4 DCT MIP plan were superior over free breathing CT plan. The reproducibility and regularity of respiratory amplitude and period were significantly improved with the complex system-guided breathing compared to the free or the audio-guided breathing. In addition, the treatment plan based on the 4D CT-based MIP images acquired with the complex system guided breathing showed better normal tissue sparing than that on the free breathing CT.

Exploring the Photoreduction of Au(III) Complexes in the Gas-Phase

NASA Astrophysics Data System (ADS)

Marcum, Jesse C.; Kaufman, Sydney H.; Weber, J. Mathias

2010-06-01

We have used photodissociation spectroscopy to probe the electronic structure and photoreduction of Au(III) in gas-phase complexes containing Cl- and OH-. The gas-phase electronic spectrum of [AuCl_4]- closely resembles the aqueous solution spectrum, showing a lack of strong solvatochromic shifts. Substitution of Cl- ligands with OH- results in a strong blue shift, in agreement with ligand-field theory. Upon excitation, [AuCl_4]- can dissociate by loss of either one or two neutral Cl atoms, resulting in the reduction of gold from Au(III) to Au(II) and Au(I) respectively. The hydroxide substituted complex, [AuCl_2(OH)_2]-, demonstrates similar behavior but the only observable fragment channel is the loss of two neutral OH ligands, leading only to Au(I).

A comparative study of the biosorption of iron(III)-cyanide complex anions to Rhizopus arrhizus and Chlorella vulgaris

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aksu, Z.; Calik, A.

1999-03-01

In this study a comparative biosorption of iron(III)-cyanide complex anions from aqueous solutions to Rhizopus arrhizus and Chlorella vulgaris was investigated. The iron(III)-cyanide complex ion-binding capacities of the biosorbents were shown as a function of initial pH, initial iron(III)-cyanide complex ion, and biosorbent concentrations. The results indicated that a significant reduction of iron(III)-cyanide complex ions was achieved at pH 13, a highly alkaline condition for both the biosorbents. The maximum loading capacities of the biosorbents were found to be 612.2 mg/g for R.arrhizus at 1,996.2 mg/L initial iron(III)-cyanide complex ion concentration and 387.0 mg/g for C. vulgaris at 845.4 mg/Lmore » initial iron(III)-cyanide complex ion concentration at this pH. The Freundlich, Langmuir, and Redlich-Peterson adsorption models were fitted to the equilibrium data at pH 3, 7, and 13. The equilibrium data of the biosorbents could be best fitted by all the adsorption models over the entire concentration range at pH 13.« less

Binuclear ruthenium(III) bis(thiosemicarbazone) complexes: Synthesis, spectral, electrochemical studies and catalytic oxidation of alcohol

NASA Astrophysics Data System (ADS)

Mohamed Subarkhan, M.; Ramesh, R.

2015-03-01

A new series of binuclear ruthenium(III) thiosemicarbazone complexes of general formula [(EPh3)2(X)2Ru-L-Ru(X)2(EPh3)2] (where E = P or As; X = Cl or Br; L = NS chelating bis(thiosemicarbazone ligands) has been synthesized and characterized by analytical and spectral (FT-IR, UV-Vis and EPR). IR spectra show that the thiosemicarbazones behave as monoanionic bidentate ligands coordinating through the azomethine nitrogen and thiolate sulphur. The electronic spectra of the complexes indicate that the presence of d-d and intense LMCT transitions in the visible region. The complexes are paramagnetic (low spin d5) in nature and all the complexes show rhombic distortion around the ruthenium ion with three different 'g' values (gx ≠ gy ≠ gz) at 77 K. All the complexes are redox active and exhibit an irreversible metal centered redox processes (RuIII-RuIII/RuIV-RuIV; RuIII-RuIII/RuII-RuII) within the potential range of 0.38-0.86 V and -0.39 to -0.66 V respectively, versus Ag/AgCl. Further, the catalytic efficiency of one of the complexes [Ru2Cl2(AsPh3)4(L1)] (4) has been investigated in the case of oxidation of primary and secondary alcohols into their corresponding aldehydes and ketones in the presence of N-methylmorpholine-N-oxide(NMO) as co-oxidant. The formation of high valent RuVdbnd O species is proposed as catalytic intermediate for the catalytic cycle.

Construction of Polynuclear Lanthanide (Ln = Dy(III), Tb(III), and Nd(III)) Cage Complexes Using Pyridine-Pyrazole-Based Ligands: Versatile Molecular Topologies and SMM Behavior.

PubMed

Bala, Sukhen; Sen Bishwas, Mousumi; Pramanik, Bhaskar; Khanra, Sumit; Fromm, Katharina M; Poddar, Pankaj; Mondal, Raju

2015-09-08

Employment of two different pyridyl-pyrazolyl-based ligands afforded three octanuclear lanthanide(III) (Ln = Dy, Tb) cage compounds and one hexanuclear neodymium(III) coordination cage, exhibiting versatile molecular architectures including a butterfly core. Relatively less common semirigid pyridyl-pyrazolyl-based asymmetric ligand systems show an interesting trend of forming polynuclear lanthanide cage complexes with different coordination environments around the metal centers. It is noteworthy here that construction of lanthanide complex itself is a challenging task in a ligand system as soft N-donor rich as pyridyl-pyrazol. We report herein some lanthanide complexes using ligand containing only one or two O-donors compare to five N-coordinating sites. The resultant multinuclear lanthanide complexes show interesting magnetic and spectroscopic features originating from different spatial arrangements of the metal ions. Alternating current (ac) susceptibility measurements of the two dysprosium complexes display frequency- and temperature-dependent out-of-phase signals in zero and 0.5 T direct current field, a typical characteristic feature of single-molecule magnet (SMM) behavior, indicating different energy reversal barriers due to different molecular topologies. Another aspect of this work is the occurrence of the not-so-common SMM behavior of the terbium complex, further confirmed by ac susceptibility measurement.

Modulation of Respiratory Frequency by Peptidergic Input to Rhythmogenic Neurons in the PreBötzinger Complex

PubMed Central

Gray, Paul A.; Rekling, Jens C.; Bocchiaro, Christopher M.; Feldman, Jack L.

2010-01-01

Neurokinin-1 receptor (NK1R) and μ-opioid receptor (μOR) agonists affected respiratory rhythm when injected directly into the preBötzinger Complex (preBötC), the hypothesized site for respiratory rhythmogenesis in mammals. These effects were mediated by actions on preBötC rhythmogenic neurons. The distribution of NK1R+ neurons anatomically defined the preBötC. Type 1 neurons in the preBötC, which have rhythmogenic properties, expressed both NK1Rs and μORs, whereas type 2 neurons expressed only NK1Rs. These findings suggest that the preBötC is a definable anatomic structure with unique physiological function and that a subpopulation of neurons expressing both NK1Rs and μORs generate respiratory rhythm and modulate respiratory frequency. PMID:10567264

A family of acetato-diphenoxo triply bridged dimetallic Zn(II)Ln(III) complexes: SMM behavior and luminescent properties.

PubMed

Oyarzabal, Itziar; Artetxe, Beñat; Rodríguez-Diéguez, Antonio; García, JoséÁngel; Seco, José Manuel; Colacio, Enrique

2016-06-21

Eleven dimetallic Zn(II)-Ln(III) complexes of the general formula [Zn(µ-L)(µ-OAc)Ln(NO3)2]·CH3CN (Ln(III) = Pr (1), Nd (2), Sm (3), Eu (4), Gd (5), Tb (6), Dy (7), Ho (8), Er (9), Tm (10), Yb (11)) have been prepared in a one-pot reaction from the compartmental ligand N,N'-dimethyl-N,N'-bis(2-hydroxy-3-formyl-5-bromo-benzyl)ethylenediamine (H2L). In all these complexes, the Zn(II) ions occupy the internal N2O2 site whereas the Ln(III) ions show preference for the O4 external site. Both metallic ions are bridged by an acetate bridge, giving rise to triple mixed diphenoxido/acetate bridged Zn(II)Ln(III) compounds. The Nd, Dy, Er and Yb complexes exhibit field induced single-ion magnet (SIM) behaviour, with Ueff values ranging from 14.12 to 41.55 K. The Er complex shows two relaxation processes, but only the second relaxation process with an energy barrier of 21.0 K has been characterized. The chromophoric L(2-) ligand is able to act as an "antenna" group, sensitizing the near-infrared (NIR) Nd(III) and Yb(III)-based luminescence in complexes 2 and 11 and therefore, both compounds can be considered as magneto-luminescent materials. In addition, the Sm(III), Eu(III) and Tb(III) derivatives exhibit characteristic emissions in the visible region.

Thiocyanato Chromium (III) Complexes: Separation by Paper Electrophoresis and Estimate of Stability Constants

ERIC Educational Resources Information Center

Larsen, Erik; Eriksen, J.

1975-01-01

Describes an experiment wherein the student can demonstrate the existence of all the thiocyanato chromium complexes, estimate the stepwise formation constants, demonstrate the robustness of chromium III complexes, and show the principles of paper electrophoresis. (GS)

Spectroscopic studies on interaction of BSA and Eu(III) complexes with H5ph-dtpa and H5dtpa ligands

NASA Astrophysics Data System (ADS)

Kong, Deyong; Qin, Cui; Fan, Ping; Li, Bing; Wang, Jun

2015-04-01

An novel aromatic aminopolycarboxylic acid ligand, N-(2-N,N-Dicarboxymethylaminophenyl) ethylenediamine-N,N‧,N‧-triacetic acid (H5ph-dtpa), was synthesized by improving experimental method and its corresponding Eu(III) complex, Na2[EuIII(ph-dtpa)(H2O)]·6H2O, was successfully prepared through heat-refluxing method. As a comparison, the Eu(III) complex with diethylenetriamine-N,N,N‧,N‧,N″-pentaacetic acid (H5dtpa) ligand, Na2[EuIII(dtpa)(H2O)]·6H2O, was also prepared by the same method. And then, the interaction between prepared Eu(III) complexes ([EuIII(dtpa)(H2O)]2- and [EuIII(ph-dtpa)(H2O)]2-) and bovine serum albumin (BSA) in aqueous solution were studied by the combination of ultraviolet-visible (UV-vis), fluorescence and circular dichroism (CD) spectroscopies. In addition, the binding sites of Eu(III) complexes ([EuIII(dtpa)(H2O)]2- and [EuIII(ph-dtpa)(H2O)]2-) to BSA molecules were also estimated by synchronous fluorescence. Moreover, the theoretical and experimental results show that the Van der Waals, hydrogen bond and π-π stacking interactions are the mainly impulse to the reaction. The binding distances (r) between Eu(III) complexes ([EuIII(dtpa)(H2O)]2- and [EuIII(ph-dtpa)(H2O)]2-) and BSA were obtained according to Förster's non-radiative energy transfer theory. Also, the determined UV-vis absorption spectroscopy, synchronous fluorescence and circular dichroism (CD) spectra showed that the conformation of BSA could be changed in the presence of Eu(III) complexes. The obtained results can help understand the action mode between rare earth metal complexes of aminopolycarboxylic acid ligands with BSA and they are also expected to provide important information of designs of new inspired drugs.

Absence of Complex I Is Associated with Diminished Respiratory Chain Function in European Mistletoe.

PubMed

Maclean, Andrew E; Hertle, Alexander P; Ligas, Joanna; Bock, Ralph; Balk, Janneke; Meyer, Etienne H

2018-05-21

Parasitism is a life history strategy found across all domains of life whereby nutrition is obtained from a host. It is often associated with reductive evolution of the genome, including loss of genes from the organellar genomes [1, 2]. In some unicellular parasites, the mitochondrial genome (mitogenome) has been lost entirely, with far-reaching consequences for the physiology of the organism [3, 4]. Recently, mitogenome sequences of several species of the hemiparasitic plant mistletoe (Viscum sp.) have been reported [5, 6], revealing a striking loss of genes not seen in any other multicellular eukaryotes. In particular, the nad genes encoding subunits of respiratory complex I are all absent and other protein-coding genes are also lost or highly diverged in sequence, raising the question what remains of the respiratory complexes and mitochondrial functions. Here we show that oxidative phosphorylation (OXPHOS) in European mistletoe, Viscum album, is highly diminished. Complex I activity and protein subunits of complex I could not be detected. The levels of complex IV and ATP synthase were at least 5-fold lower than in the non-parasitic model plant Arabidopsis thaliana, whereas alternative dehydrogenases and oxidases were higher in abundance. Carbon flux analysis indicates that cytosolic reactions including glycolysis are greater contributors to ATP synthesis than the mitochondrial tricarboxylic acid (TCA) cycle. Our results describe the extreme adjustments in mitochondrial functions of the first reported multicellular eukaryote without complex I. Copyright © 2018 Elsevier Ltd. All rights reserved.

Slow Magnetic Relaxation and Single-Molecule Toroidal Behaviour in a Family of Heptanuclear {CrIII LnIII6 } (Ln=Tb, Ho, Er) Complexes.

PubMed

Vignesh, Kuduva R; Langley, Stuart K; Swain, Abinash; Moubaraki, Boujemaa; Damjanović, Marko; Wernsdorfer, Wolfgang; Rajaraman, Gopalan; Murray, Keith S

2018-01-15

The synthesis, magnetic properties, and theoretical studies of three heterometallic {Cr III Ln III 6 } (Ln=Tb, Ho, Er) complexes, each containing a metal topology consisting of two Ln 3 triangles connected via a Cr III linker, are reported. The {CrTb 6 } and {CrEr 6 } analogues display slow relaxation of magnetization in a 3000 Oe static magnetic field. Single-crystal measurements reveal opening up of the hysteresis loop for {CrTb 6 } and {CrHo 6 } molecules at low temperatures. Ab initio calculations predict toroidal magnetic moments in the two Ln 3 triangles, which are found to couple, stabilizing a con-rotating ferrotoroidal ground state in Tb and Ho examples and extend the possibility of observing toroidal behaviour in non Dy III complexes for the first time. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Steric and Electronic Influence on Proton-Coupled Electron-Transfer Reactivity of a Mononuclear Mn(III)-Hydroxo Complex.

PubMed

Rice, Derek B; Wijeratne, Gayan B; Burr, Andrew D; Parham, Joshua D; Day, Victor W; Jackson, Timothy A

2016-08-15

A mononuclear hydroxomanganese(III) complex was synthesized utilizing the N5 amide-containing ligand 2-[bis(pyridin-2-ylmethyl)]amino-N-2-methyl-quinolin-8-yl-acetamidate (dpaq(2Me) ). This complex is similar to previously reported [Mn(III)(OH)(dpaq(H))](+) [Inorg. Chem. 2014, 53, 7622-7634] but contains a methyl group adjacent to the hydroxo moiety. This α-methylquinoline group in [Mn(III)(OH)(dpaq(2Me))](+) gives rise to a 0.1 Å elongation in the Mn-N(quinoline) distance relative to [Mn(III)(OH)(dpaq(H))](+). Similar bond elongation is observed in the corresponding Mn(II) complex. In MeCN, [Mn(III)(OH)(dpaq(2Me))](+) reacts rapidly with 2,2',6,6'-tetramethylpiperidine-1-ol (TEMPOH) at -35 °C by a concerted proton-electron transfer (CPET) mechanism (second-order rate constant k2 of 3.9(3) M(-1) s(-1)). Using enthalpies and entropies of activation from variable-temperature studies of TEMPOH oxidation by [Mn(III)(OH)(dpaq(2Me))](+) (ΔH(‡) = 5.7(3) kcal(-1) M(-1); ΔS(‡) = -41(1) cal M(-1) K(-1)), it was determined that [Mn(III)(OH)(dpaq(2Me))](+) oxidizes TEMPOH ∼240 times faster than [Mn(III)(OH)(dpaq(H))](+). The [Mn(III)(OH)(dpaq(2Me))](+) complex is also capable of oxidizing the stronger O-H and C-H bonds of 2,4,6-tri-tert-butylphenol and xanthene, respectively. However, for these reactions [Mn(III)(OH)(dpaq(2Me))](+) displays, at best, modest rate enhancement relative to [Mn(III)(OH)(dpaq(H))](+). A combination of density function theory (DFT) and cyclic voltammetry studies establish an increase in the Mn(III)/Mn(II) reduction potential of [Mn(III)(OH)(dpaq(2Me))](+) relative to [Mn(III)(OH)(dpaq(H))](+), which gives rise to a larger driving force for CPET for the former complex. Thus, more favorable thermodynamics for [Mn(III)(OH)(dpaq(2Me))](+) can account for the dramatic increase in rate with TEMPOH. For the more sterically encumbered substrates, DFT computations suggest that this effect is mitigated by unfavorable steric interactions between the

Synthesis and Mossbauer spectroscopy of macrocyclic complexes of iron(III)

NASA Astrophysics Data System (ADS)

Mishra, A.; Sura, Kamaljeet S.; Sharma, P.

2016-10-01

The article deals with a fresh series of the complexes of the type: [Fe(III)(TML)Cl]Cl2; where TML is a tetra-dentate macrocyclic ligand; has been synthesized by condensation of o-phenylenediamine, diethyl malonate and diazonium ion in the ethanolic medium, through refluxing with FeCl3.The synthesized metal complexes were characterized by Mossbauer spectroscopy. Mossbauer measurements were carried out using standard PC-based spectrometer equipped with Weissel velocity drive operating in the constant acceleration mode. Mossbauer study interprets paramagnetic nature of complexes. Mossbauer measurement of complex 1 and 2 has been taken to find out the value of isomer shift and quadrapole splitting and oxidation state after complaxsation.

Copper-Mediated Fluorination of Arylboronate Esters. Identification of a Copper(III) Fluoride Complex

PubMed Central

Fier, Patrick S.; Luo, Jingwei; Hartwig, John F.

2013-01-01

A method for the direct conversion of arylboronate esters to aryl fluorides under mild conditions with readily available reagents is reported. Tandem reactions have also been developed for the fluorination of arenes and aryl bromides through aryl-boronate ester intermediates. Mechanistic studies suggest that this fluorination reaction occurs through facile oxidation of Cu(I) to Cu(III) followed by rate-limiting transmetallation of a bound arylboronate to Cu(III). Fast C-F reductive elimination is proposed to occur from an aryl-copper(III)-fluoride complex. Cu(III) intermediates have been generated independently and identified by NMR spectroscopy and ESI-MS. PMID:23384209

Eu(III) Complexes of Octadentate 1-Hydroxy-2-pyridinones: Stability and Improved Photophysical Performance[].

PubMed

Moore, Evan G; D'Aléo, Anthony; Xu, Jide; Raymond, Kenneth N

2009-10-13

The luminescence properties of lanthanoid ions can be dramatically enhanced by coupling them to antenna ligands that absorb light in the UV/visible and then efficiently transfer the energy to the lanthanoid center. The synthesis and the complexation of Ln(III) cations (Ln=Eu; Gd) for a ligand based on four 1-hydroxy-2-pyridinone (1,2-HOPO) chelators appended to a ligand backbone derived by linking two L-lysine units (3LI-bis-LYS) is described. This octadentate Eu(III) complex ([Eu(3LI-bis-LYS-1,2-HOPO)](-)) has been evaluated in terms of its thermodynamic stability, UV/visible absorption and luminescence properties. For this complex the conditional stability constant (pM) is 19.9, which is an order of magnitude higher than diethylenetriaminepentacetic acid (DTPA) at pH= 7.4. This Eu(III) complex also shows an almost two-fold increase in its luminescence quantum yield in aqueous solution (pH= 7.4) when compared to other octadentate ligands. Hence, despite a slight decrease of the molar absorption coefficient, a much higher brightness is obtained for [Eu(3LI-bis-LYS-1,2-HOPO)](-). This overall improvement was achieved by saturating the coordination sphere of the Eu(III) cation, yielding an increased metal centered efficiency by excluding solvent water molecules from the metal's inner sphere.

Photochemical and DFT studies on DNA-binding ability and antibacterial activity of lanthanum(III)-phenanthroline complex

NASA Astrophysics Data System (ADS)

Niroomand, Sona; Khorasani-Motlagh, Mozhgan; Noroozifar, Meissam; Jahani, Shohreh; Moodi, Asieh

2017-02-01

The binding of the lanthanum(III) complex containing 1,10-phenanthroline (phen), [La(phen)3Cl3·OH2], to DNA is investigated by absorption and emission methods. This complex shows absorption decreasing in a charge transfer band, and fluorescence decrement when it binds to DNA. Electronic absorption spectroscopy (UV-Vis), fluorescence spectra, iodide quenching experiments, salt effect and viscosity measurements, ethidium bromide (EB) competition test, circular dichroism (CD) spectra as well as variable temperature experiments indicate that the La(III) complex binds to fish salmon (FS) DNA, presumably via groove binding mode. The binding constants (Kb) of the La(III) complex with DNA is (2.55 ± 0.02) × 106 M-1. Furthermore, the binding site size, n, the Stern-Volmer constant KSV and thermodynamic parameters; enthalpy change (ΔH0) and entropy change (ΔS0) and Gibb's free energy (ΔG0), are calculated according to relevant fluorescent data and the Van't Hoff equation. The La(III) complex has been screened for its antibacterial activities by the disc diffusion method. Also, in order to supplement the experimental findings, DFT computation and NBO analysis are carried out.

Metabolic flexibility of mitochondrial respiratory chain disorders predicted by computer modelling.

PubMed

Zieliński, Łukasz P; Smith, Anthony C; Smith, Alexander G; Robinson, Alan J

2016-11-01

Mitochondrial respiratory chain dysfunction causes a variety of life-threatening diseases affecting about 1 in 4300 adults. These diseases are genetically heterogeneous, but have the same outcome; reduced activity of mitochondrial respiratory chain complexes causing decreased ATP production and potentially toxic accumulation of metabolites. Severity and tissue specificity of these effects varies between patients by unknown mechanisms and treatment options are limited. So far most research has focused on the complexes themselves, and the impact on overall cellular metabolism is largely unclear. To illustrate how computer modelling can be used to better understand the potential impact of these disorders and inspire new research directions and treatments, we simulated them using a computer model of human cardiomyocyte mitochondrial metabolism containing over 300 characterised reactions and transport steps with experimental parameters taken from the literature. Overall, simulations were consistent with patient symptoms, supporting their biological and medical significance. These simulations predicted: complex I deficiencies could be compensated using multiple pathways; complex II deficiencies had less metabolic flexibility due to impacting both the TCA cycle and the respiratory chain; and complex III and IV deficiencies caused greatest decreases in ATP production with metabolic consequences that parallel hypoxia. Our study demonstrates how results from computer models can be compared to a clinical phenotype and used as a tool for hypothesis generation for subsequent experimental testing. These simulations can enhance understanding of dysfunctional mitochondrial metabolism and suggest new avenues for research into treatment of mitochondrial disease and other areas of mitochondrial dysfunction. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Self-assembly of Terbium(III)-based metal-organic complexes with two-photon absorbing active

NASA Astrophysics Data System (ADS)

Li, Dandan; Shao, Nanqi; Sun, Xianshun; Zhang, Guocui; Li, Shengli; Zhou, Hongping; Wu, Jieying; Tian, Yupeng

2014-12-01

Hybrid complexes based on D-π-A type dyes p-aminostyryl-pyridinum and Terbium(III) complex anion (1, 2) have been synthesized by ionic exchange reaction. Meanwhile two different alkyl-substituted amino groups were used as electron donors in organic dyes cations. The synthesized complexes were characterized by element analysis. In addition, the structural features of them were systematic studied by single crystal X-ray diffraction analysis. Their linear properties have been systematically investigated by absorption spectra and fluorescence, the results show that the energy transfer takes place from the trans-4-[4‧-(N,N-diethylamino)styryl]-N-methyl pyridinium (2‧) cation to Tb(III). In addition, complex 2 exhibit a large two-photon absorption coefficient β: 0.044 cm/GW at 710 nm.

Structural, luminescence, thermodynamic and theoretical studies on mononuclear complexes of Eu(III) with pyridine monocarboxylate-N-oxides in aqueous solution

NASA Astrophysics Data System (ADS)

Dumpala, Rama Mohana Rao; Rawat, Neetika; Boda, Anil; Ali, Sk. Musharaf; Tomar, B. S.

2018-02-01

The mononuclear complexes formed by Eu(III) with three isomeric pyridine monocarboxylate-N-oxides namely picolinic acid-N-oxide (PANO), nicotinic acid-N-oxide (NANO) and isonicotinic acid-N-oxide (IANO) in aqueous solutions were studied by potentiometry, luminescence spectroscopy and isothermal titration calorimetry (ITC) to determine the speciation, coordination, luminescence properties and thermodynamic parameters of the complexes formed during the course of the reaction. More stable six membered chelate complexes with stoichiometry (MLi, i = 1-4) are formed by Eu(III) with PANO while non chelating ML and ML2 complexes are formed by NANO and IANO. The stability of Eu(III) complexes follow the order PANO > IANO > NANO. The ITC studies inferred an endothermic and innersphere complex formation of Eu(III)-PANO and Eu(III)-IANO whereas an exothermic and outer-sphere complex formation for Eu(III)-NANO. The luminescence life time data further supported the ITC results. Density functional theoretical calculations were carried out to optimize geometries of the complexes and to estimate the energies, structural parameters (bond distances, bond angles) and charges on individual atoms of the same. Theoretical approximations are found to be in good agreement with the experimental observations.

Single Pathogen Challenge with Agents of the Bovine Respiratory Disease Complex.

PubMed

Gershwin, Laurel J; Van Eenennaam, Alison L; Anderson, Mark L; McEligot, Heather A; Shao, Matt X; Toaff-Rosenstein, Rachel; Taylor, Jeremy F; Neibergs, Holly L; Womack, James

2015-01-01

Bovine respiratory disease complex (BRDC) is an important cause of mortality and morbidity in cattle; costing the dairy and beef industries millions of dollars annually, despite the use of vaccines and antibiotics. BRDC is caused by one or more of several viruses (bovine respiratory syncytial virus, bovine herpes type 1 also known as infectious bovine rhinotracheitis, and bovine viral diarrhea virus), which predispose animals to infection with one or more bacteria. These include: Pasteurella multocida, Mannheimia haemolytica, Mycoplasma bovis, and Histophilus somni. Some cattle appear to be more resistant to BRDC than others. We hypothesize that appropriate immune responses to these pathogens are subject to genetic control. To determine which genes are involved in the immune response to each of these pathogens it was first necessary to experimentally induce infection separately with each pathogen to document clinical and pathological responses in animals from which tissues were harvested for subsequent RNA sequencing. Herein these infections and animal responses are described.

Single Pathogen Challenge with Agents of the Bovine Respiratory Disease Complex

PubMed Central

Gershwin, Laurel J.; Van Eenennaam, Alison L.; Anderson, Mark L.; McEligot, Heather A.; Toaff-Rosenstein, Rachel; Taylor, Jeremy F.; Neibergs, Holly L.; Womack, James

2015-01-01

Bovine respiratory disease complex (BRDC) is an important cause of mortality and morbidity in cattle; costing the dairy and beef industries millions of dollars annually, despite the use of vaccines and antibiotics. BRDC is caused by one or more of several viruses (bovine respiratory syncytial virus, bovine herpes type 1 also known as infectious bovine rhinotracheitis, and bovine viral diarrhea virus), which predispose animals to infection with one or more bacteria. These include: Pasteurella multocida, Mannheimia haemolytica, Mycoplasma bovis, and Histophilus somni. Some cattle appear to be more resistant to BRDC than others. We hypothesize that appropriate immune responses to these pathogens are subject to genetic control. To determine which genes are involved in the immune response to each of these pathogens it was first necessary to experimentally induce infection separately with each pathogen to document clinical and pathological responses in animals from which tissues were harvested for subsequent RNA sequencing. Herein these infections and animal responses are described. PMID:26571015

Effect of alkaline precipitation on Cr species of Cr(III)-bearing complexes typically used in the tannery industry.

PubMed

Wang, Dandan; Ye, Yuxuan; Liu, Hui; Ma, Hongrui; Zhang, Weiming

2018-02-01

Various organic compounds extensively used in the leather industry could influence the performance of alkaline precipitation with Cr(III). This study focused on two typical Cr(III)-bearing complexes (Cr(III)-collagen and Cr(III)-citrate) ubiquitous in tannery effluent yet with distinct treatment efficiencies, as Cr(III) was much more difficult to remove in the Cr(III)-citrate solution. Comprehensive analytical methods were employed to explore the intrinsic mechanism. It was found that a lower removal efficiency towards Cr(III) was significantly associated with higher oligomers. The molecular size of the Cr(III)-citrate complex continued to increase with rising pH, making it larger overall than Cr(III)-collagen species. The growing oligomer moiety of dissolved Cr(III)-complex species could persist in the stronger basic pH range, leading to the large amount of residual Cr(III) in the Cr(III)-citrate system. Combining this result with potentiometric titration and X-ray photoelectron spectroscopy data, it was believed that the polymeric species other than monomers facilitated resisting the attack from hydroxide ions, and the postulated Cr(III)-citrate species towards higher oligomers were discovered. Beyond that, both charge neutralization and sweeping effects were presented among the gradually emerging flocs in the Cr(III)-collagen system together with the electric double layer compression effect derived from salinity, thus resulting in a larger floc size and higher Cr(III) removal efficiency in saline solutions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spectroscopic studies on interaction of BSA and Eu(III) complexes with H5ph-dtpa and H5dtpa ligands.

PubMed

Kong, Deyong; Qin, Cui; Fan, Ping; Li, Bing; Wang, Jun

2015-04-05

An novel aromatic aminopolycarboxylic acid ligand, N-(2-N,N-Dicarboxymethylaminophenyl) ethylenediamine-N,N',N'-triacetic acid (H5ph-dtpa), was synthesized by improving experimental method and its corresponding Eu(III) complex, Na2[EuIII(ph-dtpa)(H2O)]·6H2O, was successfully prepared through heat-refluxing method. As a comparison, the Eu(III) complex with diethylenetriamine-N,N,N',N',N″-pentaacetic acid (H5dtpa) ligand, Na2[Eu(III)(dtpa)(H2O)]·6H2O, was also prepared by the same method. And then, the interaction between prepared Eu(III) complexes ([EuIII(dtpa)(H2O)]2- and [EuIII(ph-dtpa)(H2O)]2-) and bovine serum albumin (BSA) in aqueous solution were studied by the combination of ultraviolet-visible (UV-vis), fluorescence and circular dichroism (CD) spectroscopies. In addition, the binding sites of Eu(III) complexes ([EuIII(dtpa)(H2O)]2- and [EuIII(ph-dtpa)(H2O)]2-) to BSA molecules were also estimated by synchronous fluorescence. Moreover, the theoretical and experimental results show that the Van der Waals, hydrogen bond and π-π stacking interactions are the mainly impulse to the reaction. The binding distances (r) between Eu(III) complexes ([EuIII(dtpa)(H2O)]2- and [EuIII(ph-dtpa)(H2O)]2-) and BSA were obtained according to Förster's non-radiative energy transfer theory. Also, the determined UV-vis absorption spectroscopy, synchronous fluorescence and circular dichroism (CD) spectra showed that the conformation of BSA could be changed in the presence of Eu(III) complexes. The obtained results can help understand the action mode between rare earth metal complexes of aminopolycarboxylic acid ligands with BSA and they are also expected to provide important information of designs of new inspired drugs. Copyright © 2015 Elsevier B.V. All rights reserved.

Eu(III)-Fulvic Acid Complexation: Evidence of Fulvic Acid Concentration Dependent Interactions by Time-Resolved Luminescence Spectroscopy.

PubMed

Kouhail, Yasmine Z; Benedetti, Marc F; Reiller, Pascal E

2016-04-05

Europium speciation is investigated by time-resolved luminescence spectroscopy (TRLS) in the presence of Suwannee River fulvic acid (SRFA). From complexation isotherms built at different total Eu(III) concentrations, pH values, ionic strength, and SRFA concentrations, it appears that two luminescence behaviors of Eu(III) are occurring. The first part, at the lowest CSRFA values, is showing the typical luminescence evolution of Eu(III) complexed by humic substances--that is, the increase of the asymmetry ratio between the (5)D0 → (7)F2 and (5)D0 → (7)F1 transitions up to a plateau--, and the occurrence of a biexponential decay--the first decay being faster than free Eu(3+). At higher CSRFA, a second luminescence mode is detected as the asymmetry ratio is increasing again after the previous plateau, and could correspond to the formation of another type of complex, and/or it can reflect a different spatial organization of complexed europium within the SRFA structure. The luminescence decay keeps on evolving but link to hydration number is not straightforward due to quenching mechanisms. The Eu(III) chemical environment evolution with CSRFA is also ionic strength dependent. These observations suggest that in addition to short-range interactions--intraparticulate complexation--, there might be interactions at longer range--interparticulate repulsion--between particles that are complexing Eu(III) at high CSRFA. These interactions are not yet accounted by the different complexation models.

Reactivity of tris(acetylacetonato) iron(III) with tridentate [ONO] donor Schiff base as an access to newer mixed-ligand iron(III) complexes

NASA Astrophysics Data System (ADS)

Bhattacharjee, Chira R.; Goswami, Pankaj; Pramanik, Harun A. R.; Paul, Pradip C.; Mondal, Paritosh

2011-05-01

Two new mixed-ligand iron(III) complexes, [Fe(L n)(acac)(C 2H 5OH)] incorporating coordinated ethanol from the reaction solvent were accessed from the reaction of [Fe(acac) 3] with [ONO] donor dibasic tridentate unsymmetrical Schiff base ligands derived from condensation of 2-hydroxy-1-napthaldehyde with 2-aminophenol (H 2L 1) or 2-aminobenzoic acid (H 2L 2). The thermal study (TGA-DTA) provided evidence for weakly bound ethanol which is readily substituted by neutral N-donor molecule imidazole, benzimidazole or pyridine to produce an array of newer complexes, [Fe(L n)(acac)X] ( n = 1, 2; X = Im, Bim, Py). The compounds were characterized by elemental analyses, FT-IR, UV-vis, solution electrical conductivity, FAB mass, 1H and 13C NMR spectroscopy. Room temperature magnetic susceptibility measurements ( μeff ˜ 5.8 B.M.) are consistent with spin-free octahedral iron(III) complexes. Cyclic voltammetry of ethanol complexes revealed a quasi-reversible one electron redox response (Δ Ep > 100 mV) for the Fe(III)/Fe(II) couple. Low half wave redox potential ( E1/2) values suggested easy redox susceptibility. The ground state geometries of the ethanol and imidazole complexes have been ascertained to be distorted octahedral by density functional theory using DMol3 program at BLYP/DNP level.

Reactivity of tris(acetylacetonato) iron(III) with tridentate [ONO] donor Schiff base as an access to newer mixed-ligand iron(III) complexes.

PubMed

Bhattacharjee, Chira R; Goswami, Pankaj; Pramanik, Harun A R; Paul, Pradip C; Mondal, Paritosh

2011-05-01

Two new mixed-ligand iron(III) complexes, [Fe(L(n))(acac)(C(2)H(5)OH)] incorporating coordinated ethanol from the reaction solvent were accessed from the reaction of [Fe(acac)(3)] with [ONO] donor dibasic tridentate unsymmetrical Schiff base ligands derived from condensation of 2-hydroxy-1-napthaldehyde with 2-aminophenol (H(2)L(1)) or 2-aminobenzoic acid (H(2)L(2)). The thermal study (TGA-DTA) provided evidence for weakly bound ethanol which is readily substituted by neutral N-donor molecule imidazole, benzimidazole or pyridine to produce an array of newer complexes, [Fe(L(n))(acac)X] (n=1, 2; X=Im, Bim, Py). The compounds were characterized by elemental analyses, FT-IR, UV-vis, solution electrical conductivity, FAB mass, (1)H and (13)C NMR spectroscopy. Room temperature magnetic susceptibility measurements (μ(eff)∼5.8 B.M.) are consistent with spin-free octahedral iron(III) complexes. Cyclic voltammetry of ethanol complexes revealed a quasi-reversible one electron redox response (ΔE(p)>100 mV) for the Fe(III)/Fe(II) couple. Low half wave redox potential (E(1/2)) values suggested easy redox susceptibility. The ground state geometries of the ethanol and imidazole complexes have been ascertained to be distorted octahedral by density functional theory using DMol3 program at BLYP/DNP level. Copyright © 2011 Elsevier B.V. All rights reserved.

A new iron(III) complex-containing sulfadiazine inhibits the proliferation and induces cystogenesis of Toxoplasma gondii.

PubMed

Portes, Juliana de A; Azeredo, Nathália F B; Siqueira, Pedro G T; de Souza, Tatiana Guinancio; Fernandes, Christiane; Horn, Adolfo; Candela, Dalber R S; de Souza, Wanderley; DaMatta, Renato A; Seabra, Sérgio H

2018-06-22

We have previously shown that metallocomplexes can control the growth of Toxoplasma gondii, the agent that causes toxoplasmosis. In order to develop new metallodrugs to treat this disease, we investigated the influence of the coordination of sulfadiazine (SDZ), a drug used to treat toxoplasmosis, on the biological activity of the iron(III) complex [Fe(HBPClNOL)Cl 2 ]·H 2 O, 1, (H 2 BPClNOL=N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)(3-chloro)(2-hydroxy)-propylamine). The new complex [(Cl)(SDZ)Fe(III)(μ-BPClNOL) 2 Fe(III)(SDZ)(Cl)]·2H 2 O, 2, which was obtained by the reaction between complex 1 and SDZ, was characterized using a range of physico-chemical techniques. The cytotoxic effect of the complexes and the ability of T. gondii to infect LLC-MK2 cells were assessed. It was found that both complexes reduced the growth of T. gondii while also causing low cytotoxicity in the host cells. After 48 h of treatment, complex 2 reduced the parasite's ability to proliferate by about 50% with an IC 50 of 1.66 μmol/L. Meanwhile, complex 1 or SDZ alone caused a 40% reduction in proliferation, and SDZ displayed an IC 50 of 5.3 μmol/L. In addition, complex 2 treatment induced distinct morphological and ultrastructural changes in the parasites and triggered the formation of cyst-like forms. These results show that the coordination of SDZ to the iron(III) complex is a good strategy for increasing the anti-toxoplasma activity of these compounds.

Synthesis of square-planar aluminum(III) complexes.

PubMed

Thompson, Emily J; Myers, Thomas W; Berben, Louise A

2014-12-15

The synthesis of two four-coordinate and square planar (SP) complexes of aluminum(III) is presented. Reaction of a phenyl-substituted bis(imino)pyridine ligand that is reduced by two electrons, Na2((Ph)I2P(2-)), with AlCl3 afforded five-coordinate [((Ph)I2P(2-))Al(THF)Cl] (1). Square-planar [((Ph)I2P(2-))AlCl] (2) was obtained by performing the same reaction in diethyl ether followed by lyphilization of 2 from benzene. The four-coordinate geometry index for 2, τ4, is 0.22, where 0 would be a perfectly square-planar molecule. The analogous aluminum hydride complex, [((Ph)I2P(2-))AlH] (3), is also square-planar, and was characterized crystallographically and has τ4=0.13. Both 2 and 3 are Lewis acidic and bind 2,6-lutidine. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and characterization of carbazolide-based iridium PNP pincer complexes. Mechanistic and computational investigation of alkene hydrogenation: evidence for an Ir(III)/Ir(V)/Ir(III) catalytic cycle.

PubMed

Cheng, Chen; Kim, Bong Gon; Guironnet, Damien; Brookhart, Maurice; Guan, Changjian; Wang, David Y; Krogh-Jespersen, Karsten; Goldman, Alan S

2014-05-07

New carbazolide-based iridium pincer complexes ((carb)PNP)Ir(C2H4), 3a, and ((carb)PNP)Ir(H)2, 3b, have been prepared and characterized. The dihydride, 3b, reacts with ethylene to yield the cis-dihydride ethylene complex cis-((carb)PNP)Ir(C2H4)(H)2. Under ethylene this complex reacts slowly at 70 °C to yield ethane and the ethylene complex, 3a. Kinetic analysis establishes that the reaction rate is dependent on ethylene concentration and labeling studies show reversible migratory insertion to form an ethyl hydride complex prior to formation of 3a. Exposure of cis-((carb)PNP)Ir(C2H4)(H)2 to hydrogen results in very rapid formation of ethane and dihydride, 3b. DFT analysis suggests that ethane elimination from the ethyl hydride complex is assisted by ethylene through formation of ((carb)PNP)Ir(H)(Et)(C2H4) and by H2 through formation of ((carb)PNP)Ir(H)(Et)(H2). Elimination of ethane from Ir(III) complex ((carb)PNP)Ir(H)(Et)(H2) is calculated to proceed through an Ir(V) complex ((carb)PNP)Ir(H)3(Et) which reductively eliminates ethane with a very low barrier to return to the Ir(III) dihydride, 3b. Under catalytic hydrogenation conditions (C2H4/H2), cis-((carb)PNP)Ir(C2H4)(H)2 is the catalyst resting state, and the catalysis proceeds via an Ir(III)/Ir(V)/Ir(III) cycle. This is in sharp contrast to isoelectronic (PCP)Ir systems in which hydrogenation proceeds through an Ir(III)/Ir(I)/Ir(III) cycle. The basis for this remarkable difference is discussed.

Colorimetric and luminescent bifunctional iridium(III) complexes for the sensitive recognition of cyanide ions

NASA Astrophysics Data System (ADS)

Chen, Xiudan; Wang, Huili; Li, Jing; Hu, Wenqin; Li, Mei-Jin

2017-02-01

Two new cyclometalated iridium(III) complexes [(ppy)2Irppz]Cl (1) and [(ppy)2Irbppz]Cl (2) (where ppy = 2-phenylpyridine, ppz = 4,7-phenanthrolino-5,6:5,6-pyrazine, bppz = 2.3-di-2-pyridylpyrazine), were designed and synthesized. The structure of [(ppy)2Irppz]Cl was determined by single crystal X-ray diffraction. Their photophysical properties were also studied. This kind of complexes could coordinate with Cu2 +, the photoluminescence (PL) of the complex was quenched, and the color changed from orange-red to green. The forming M-Cu (M: complexes 1 and 2) ensemble could be further utilized as a colorimetric and emission ;turn-on; bifunctional detection for CN-, especially for complex 1-Cu2 + showed a high sensitivity toward CN- with a limit of diction is 97 nM. Importantly, this kind of iridium(III) complexes shows a unique recognition of cyanide ions over other anions which makes it an eligible sensing probe for cyanide ions.

Self-assembly of Terbium(III)-based metal-organic complexes with two-photon absorbing active.

PubMed

Li, Dandan; Shao, Nanqi; Sun, Xianshun; Zhang, Guocui; Li, Shengli; Zhou, Hongping; Wu, Jieying; Tian, Yupeng

2014-12-10

Hybrid complexes based on D-π-A type dyes p-aminostyryl-pyridinum and Terbium(III) complex anion (1, 2) have been synthesized by ionic exchange reaction. Meanwhile two different alkyl-substituted amino groups were used as electron donors in organic dyes cations. The synthesized complexes were characterized by element analysis. In addition, the structural features of them were systematic studied by single crystal X-ray diffraction analysis. Their linear properties have been systematically investigated by absorption spectra and fluorescence, the results show that the energy transfer takes place from the trans-4-[4'-(N,N-diethylamino)styryl]-N-methyl pyridinium (2') cation to Tb(III). In addition, complex 2 exhibit a large two-photon absorption coefficient β: 0.044cm/GW at 710nm. Copyright © 2014 Elsevier B.V. All rights reserved.

Mono- and bis-tolylterpyridine iridium(III) complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hinkle, Lindsay M.; Young, Jr., Victor G.; Mann, Kent R.

The first structure report of trichlorido[4'-(p-tolyl)-2,2':6',2{double_prime}-terpyridine]iridium(III) dimethyl sulfoxide solvate, [IrCl{sub 3}(C{sub 22}H{sub 17}N{sub 3})] {center_dot} C{sub 2}H{sub 6}OS, (I), is presented, along with a higher-symmetry setting of previously reported bis[4'-(p-tolyl)-2,2':6',2{double_prime}-terpyridine]iridium(III) tris(hexafluoridophosphate) acetonitrile disolvate, [Ir(C{sub 22}H{sub 17}N{sub 3})2](PF{sub 6}){sub 3} {center_dot} 2C{sub 2}H{sub 3}N, (II) [Yoshikawa, Yamabe, Kanehisa, Kai, Takashima & Tsukahara (2007). Eur. J. Inorg. Chem. pp. 1911-1919]. For (I), the data were collected with synchrotron radiation and the dimethyl sulfoxide solvent molecule is disordered over three positions, one of which is an inversion center. The previously reported structure of (II) is presented in the more appropriate C2/c space group.more » The iridium complex and one PF{sub 6}{sup -} anion lie on twofold axes in this structure, making half of the molecule unique.« less

Closed genomes of seven histophilus somni isolates from beef calves with bovine respiratory disease complex

USDA-ARS?s Scientific Manuscript database

Histophilus somni is a fastidious gram-negative opportunistic pathogenic Pasteurellacea that affects multiple organ systems and is one of the principle bacterial species contributing to bovine respiratory disease complex (BRDC) in feed yard cattle. Here we present seven closed genomes isolated from...

ARTICLES: Microwave Assisted Synthesis of a New Triplet Iridium(III) Pyrazine Complex

NASA Astrophysics Data System (ADS)

Wu, Qiu-hua; Wang, Chuan-hong; Song, Xi-ming; Zhang, Guo-lin

2010-06-01

A new cyclometalated iridium(III) complex Ir(DPP)3 (DPP = 2,3-diphenylpyrazine) was prepared by reaction of DPP with iridium trichloride hydrate under microwave irradiation. The structure of the complex was confirmed by elemental analysis, 1H NMR, and mass spectroscopy. The UV-Vis absorption and photoluminescent properties of the complex were investigated. The complex shows strong 1MLCT (singlet metal to ligand charge-transfer) and 3MLCT (triplet metal to ligand charge-transfer) absorption at 382 and 504 nm, respectively. The complex also shows strong photoluminescence at 573 nm at room temperature. These results suggest the complex to be a promising phosphorescent material.

Differences and Comparisons of the Properties and Reactivities of Iron(III)–hydroperoxo Complexes with Saturated Coordination Sphere

PubMed Central

Faponle, Abayomi S; Quesne, Matthew G; Sastri, Chivukula V; Banse, Frédéric; de Visser, Sam P

2015-01-01

Heme and nonheme monoxygenases and dioxygenases catalyze important oxygen atom transfer reactions to substrates in the body. It is now well established that the cytochrome P450 enzymes react through the formation of a high-valent iron(IV)–oxo heme cation radical. Its precursor in the catalytic cycle, the iron(III)–hydroperoxo complex, was tested for catalytic activity and found to be a sluggish oxidant of hydroxylation, epoxidation and sulfoxidation reactions. In a recent twist of events, evidence has emerged of several nonheme iron(III)–hydroperoxo complexes that appear to react with substrates via oxygen atom transfer processes. Although it was not clear from these studies whether the iron(III)–hydroperoxo reacted directly with substrates or that an initial O–O bond cleavage preceded the reaction. Clearly, the catalytic activity of heme and nonheme iron(III)–hydroperoxo complexes is substantially different, but the origins of this are still poorly understood and warrant a detailed analysis. In this work, an extensive computational analysis of aromatic hydroxylation by biomimetic nonheme and heme iron systems is presented, starting from an iron(III)–hydroperoxo complex with pentadentate ligand system (L52). Direct C–O bond formation by an iron(III)–hydroperoxo complex is investigated, as well as the initial heterolytic and homolytic bond cleavage of the hydroperoxo group. The calculations show that [(L52)FeIII(OOH)]2+ should be able to initiate an aromatic hydroxylation process, although a low-energy homolytic cleavage pathway is only slightly higher in energy. A detailed valence bond and thermochemical analysis rationalizes the differences in chemical reactivity of heme and nonheme iron(III)–hydroperoxo and show that the main reason for this particular nonheme complex to be reactive comes from the fact that they homolytically split the O–O bond, whereas a heterolytic O–O bond breaking in heme iron(III)–hydroperoxo is found. PMID:25399782

A spectrophotometric study of aqueous Au(III) halide-hydroxide complexes at 25-80 °C

NASA Astrophysics Data System (ADS)

Usher, Al; McPhail, D. C.; Brugger, Joël

2009-06-01

The mobility and transport of gold in low-temperature waters and brines is affected by the aqueous speciation of gold, which is sensitive in particular to pH, oxidation and halide concentrations. In this study, we use UV-Vis spectrophotometry to identify and measure the thermodynamic properties of Au(III) aqueous complexes with chloride, bromide and hydroxide. Au(III) forms stable square planar complexes with hydroxide and halide ligands. Based on systematic changes in the absorption spectra of solutions in three binary systems NaCl-NaBr, NaCl-NaOH and NaBr-NaOH at 25 °C, we derived log dissociation constants for the following mixed and end-member halide and hydroxide complexes: [AuCl 3Br] -, [AuCl 2Br 2] -, [AuBr 3Cl] - and [AuBr 4] -; [AuCl 3(OH)] -, [AuCl 2(OH) 2] -, [AuCl(OH) 3] - and [Au(OH) 4] -; and [AuBr 3(OH)] -, [AuBr 2(OH) 2] - and [AuBr(OH) 3] -. These are the first reported results for the mixed chloride-bromide complexes. Increasing temperature to 80 °C resulted in an increase in the stability of the mixed chloride-bromide complexes, relative to the end-member chloride and bromide complexes. For the [AuCl (4-n)(OH) n] - series of complexes ( n = 0-4), there is an excellent agreement between our spectrophotometric results and previous electrochemical results of Chateau et al. [Chateau et al. (1966)]. In other experiments, the iodide ion (I -) was found to be unstable in the presence of Au(III), oxidizing rapidly to I 2(g) and causing Au to precipitate. Predicted Au(III) speciation indicates that Au(III) chloride-bromide complexes can be important in transporting gold in brines with high bromide-chloride ratios (e.g., >0.05), under oxidizing (atmospheric), acidic (pH < 5) conditions. Native gold solubility under atmospheric oxygen conditions is predicted to increase with decreasing pH in acidic conditions, increasing pH in alkaline conditions, increasing chloride, especially at acid pH, and increasing bromide for bromide/chloride ratios greater than 0

Grafting of a novel gold(III) complex on nanoporous MCM-41 and evaluation of its toxicity in Saccharomyces cerevisiae.

PubMed

Fazaeli, Yousef; Amini, Mostafa M; Ashourion, Hamed; Heydari, Homayoun; Majdabadi, Abbas; Jalilian, Amir Reza; Abolmaali, Shamsozoha

2011-01-01

The goal of this research was to investigate the potential of newly synthesized gold complex trichloro(2,4,6-trimethylpyridine)Au(III) as an anticancer agent. The gold(III) complex was synthesized and grafted on nanoporous silica, MCM-41, to produce AuCl(3)@PF-MCM- 41 (AuCl(3) grafted on pyridine-functionalized MCM-41). The toxicity of trichloro(2,4,6- trimethylpyridine)Au(III) and AuCl(3)@PF-MCM-41 in Saccharomyces cerevisiae (as a model system) was studied. The gold(III) complex showed a mid cytotoxic effect on yeast viability. Using the drug delivery system, nanoporous MCM-41, the gold(III) complex became a strong inhibitor for growth of yeast cells at a very low concentration. Furthermore, the animal tests revealed a high uptake of AuCl(3)@PF-MCM-41 in tumor cells. The stability of the compound was confirmed in human serum.

Clinical evaluation of the Abbott RealTime MTB Assay for direct detection of Mycobacterium tuberculosis-complex from respiratory and non-respiratory samples.

PubMed

Hinić, Vladimira; Feuz, Kinga; Turan, Selda; Berini, Andrea; Frei, Reno; Pfeifer, Karin; Goldenberger, Daniel

2017-05-01

Rapid and reliable diagnosis is crucial for correct management of tuberculosis. The Abbott RealTime MTB Assay represents a novel qualitative real-time PCR assay for direct detection of M. tuberculosis-complex (MTB) DNA from respiratory samples. The test targets two highly conserved sequences, the multi-copy insertion element IS6110 and the protein antigen B (PAB) gene of MTB, allowing even the detection of IS6610-deficient strains. We evaluated this commercial diagnostic test by analyzing 200 respiratory and, for the first time, 87 non-respiratory clinical specimens from our tertiary care institution and compared its results to our IS6110-based in-house real-time PCR for MTB as well as MTB culture. Overall sensitivity for Abbott RealTime MTB was 100% (19/19) in smear positive and 87.5% (7/8) in smear negative specimens, while the specificity of the assay was 100% (260/260). For both non-respiratory smear positive and smear negative specimens Abbott RealTime MTB tests showed 100% (8/8) sensitivity and 100% (8/8) specificity. Cycle threshold (Ct) value analysis of 16 MTB positive samples showed a slightly higher Ct value of the Abbott RealTime MTB test compared to our in-house MTB assay (mean delta Ct = 2.55). In conclusion, the performance of the new Abbott RealTime MTB Assay was highly similar to culture and in-house MTB PCR. We document successful analysis of 87 non-respiratory samples with the highly automated Abbott RealTime MTB test with no inhibition observed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis, structure, luminescent, and magnetic properties of carbonato-bridged Zn(II)2Ln(III)2 complexes [(μ4-CO3)2{Zn(II)L(n)Ln(III)(NO3)}2] (Ln(III) = Gd(III), Tb(III), Dy(III); L(1) = N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, L(2) = N,N'-bis(3-ethoxy-2-oxybenzylidene)-1,3-propanediaminato).

PubMed

Ehama, Kiyomi; Ohmichi, Yusuke; Sakamoto, Soichiro; Fujinami, Takeshi; Matsumoto, Naohide; Mochida, Naotaka; Ishida, Takayuki; Sunatsuki, Yukinari; Tsuchimoto, Masanobu; Re, Nazzareno

2013-11-04

Carbonato-bridged Zn(II)2Ln(III)2 complexes [(μ4-CO3)2{Zn(II)L(n)Ln(III)(NO3)}2]·solvent were synthesized through atmospheric CO2 fixation reaction of [Zn(II)L(n)(H2O)2]·xH2O, Ln(III)(NO3)3·6H2O, and triethylamine, where Ln(III) = Gd(III), Tb(III), Dy(III); L(1) = N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, L(2) = N,N'-bis(3-ethoxy-2-oxybenzylidene)-1,3-propanediaminato. Each Zn(II)2Ln(III)2 structure possessing an inversion center can be described as two di-μ-phenoxo-bridged {Zn(II)L(n)Ln(III)(NO3)} binuclear units bridged by two carbonato CO3(2-) ions. The Zn(II) ion has square pyramidal coordination geometry with N2O2 donor atoms of L(n) and one oxygen atom of a bridging carbonato ion at the axial site. Ln(III) ion is coordinated by nine oxygen atoms consisting of four from the deprotonated Schiff-base L(n), two from a chelating nitrate, and three from two carbonate groups. The temperature-dependent magnetic susceptibilities in the range 1.9-300 K, field-dependent magnetization from 0 to 5 T at 1.9 K, and alternating current magnetic susceptibilities under the direct current bias fields of 0 and 1000 Oe were measured. The magnetic properties of the Zn(II)2Ln(III)2 complexes are analyzed on the basis of the dicarbonato-bridged binuclear Ln(III)-Ln(III) structure, as the Zn(II) ion with d(10) electronic configuration is diamagnetic. ZnGd1 (L(1)) and ZnGd2 (L(2)) show a ferromagnetic Gd(III)-Gd(III) interaction with J(Gd-Gd) = +0.042 and +0.028 cm(-1), respectively, on the basis of the Hamiltonian H = -2J(Gd-Gd)ŜGd1·ŜGd2. The magnetic data of the Zn(II)2Ln(III)2 complexes (Ln(III) = Tb(III), Dy(III)) were analyzed by a spin Hamiltonian including the crystal field effect on the Ln(III) ions and the Ln(III)-Ln(III) magnetic interaction. The Stark splitting of the ground state was so evaluated, and the energy pattern indicates a strong easy axis (Ising type) anisotropy. Luminescence spectra of Zn(II)2Tb(III)2 complexes were observed, while those

Substrate complexes of human dipeptidyl peptidase III reveal the mechanism of enzyme inhibition

PubMed Central

Kumar, Prashant; Reithofer, Viktoria; Reisinger, Manuel; Wallner, Silvia; Pavkov-Keller, Tea; Macheroux, Peter; Gruber, Karl

2016-01-01

Human dipeptidyl-peptidase III (hDPP III) is a zinc-dependent hydrolase cleaving dipeptides off the N-termini of various bioactive peptides. Thus, the enzyme is likely involved in a number of physiological processes such as nociception and is also implicated in several forms of cancer. We present high-resolution crystal structures of hDPP III in complex with opioid peptides (Met-and Leu-enkephalin, endomorphin-2) as well as with angiotensin-II and the peptide inhibitor IVYPW. These structures confirm the previously reported large conformational change of the enzyme upon ligand binding and show that the structure of the closed conformation is independent of the nature of the bound peptide. The overall peptide-binding mode is also conserved ensuring the correct positioning of the scissile peptide bond with respect to the catalytic zinc ion. The structure of the angiotensin-II complex shows, how longer peptides are accommodated in the binding cleft of hDPP III. Differences in the binding modes allow a distinction between real substrates and inhibitory peptides or “slow” substrates. The latter displace a zinc bound water molecule necessitating the energetically much less favoured anhydride mechanism as opposed to the favoured promoted-water mechanism. The structural data also form the necessary framework for the design of specific hDPP III inhibitors. PMID:27025154

What should be impossible: resolution of the mononuclear gallium coordination complex, Tris(benzohydroxamato)gallium(III).

PubMed

Brumaghim, Julia L; Raymond, Kenneth N

2003-10-08

Complexes of Ga3+, a d10 metal ion which lacks ligand-field-stabilization energy, are considered labile. In fact, hexaaquagallium(III) has a ligand exchange rate of 403 s-1, 2.5 times that of the analagous Fe3+ complex (Hugi-Cleary, D.; Helm, L.; Merbach, A. E. J. Am. Chem. Soc. 1987, 109, 4444-4450). Given this lability, resolution of Ga3+ complexes should be impossible. Despite this, we report the resolution of the Lambda and Delta isomers of tris(benzohydroxamate)gallium (III) (1), the first resolution of a mononuclear gallium complex. Not only is resolution possible, but these resolved complexes show remarkable resistance to racemization in aprotic solvents. The unprecedented stability of Lambda- and Delta-1 is a surprise, and as such, alters our understanding of classical coordination chemistry.

Complexation equilibria and spectrophotometric determination of iron(III) with 1-amino-4-hydroxyanthraquinone.

PubMed

Abu-Bakr, M S; Sedaira, H; Hashem, E Y

1994-10-01

The complex equilibria of iron(III) with 1-amino-4-hydroxyanthraquinone (AMHA) were studied spectrophotometrically in 40% (v/v) ethanol and an ionic strength of 0.1M (NaClO(4)). The complexation reactions were demonstrated and characterized using graphical logarithmic analysis of the absorbance-pH graphs. A simple, rapid, selective and sensitive method for the spectrophotometric determination of trace amounts of Fe(III) is developed based on the formation of Fe(AMHA) complex at pH 2.5 (lambda(max) = 640 nm, epsilon approximately = 2.1 x 10(4) L. mol(-1) . cm(-1)) in the presence of a large number of foreign ions. Interferences caused by palladium(II) was masked by the addition of cyanide ions. The method has been applied to the determination of iron in some synthetic samples and polymetallic iron ores.

Anion-exchange high-performance liquid chromatography of water-soluble chromium (VI) and chromium (III) complexes in biological materials.

PubMed

Suzuki, Y

1987-04-10

A high-performance anion-exchange liquid chromatograph coupled to visible-range (370 nm) and UV (280 nm) detectors and an atomic-absorption spectrometer allowed the rapid determination of CrVI and/or complexes of CrIII in rat plasma, erythrocyte lysate and liver supernatant treated with CrVI or CrIII in vitro. CrVI in the eluates was determined using both the visible-range detector and atomic-absorption spectrometer (AAS). The detection limits of CrVI in standard solutions using these methods were 2 and 5 ng (signal-to-noise ratio = 2), respectively. Separations of the biological components and of CrIII complexes were monitored by UV and AAS analyses, respectively. Time-related decreases of CrVI accompanied by increases in CrIII complexes were observed, indicating the reduction of CrVI by some of the biological components. The reduction rates were considerably higher in the liver supernatant and erythrocyte lysate than in the plasma. These results indicate that the anion-exchange high-performance liquid chromatographic system is useful for simultaneous determination of CrVI and CrIII complexes in biological materials.

[Ni III(OMe)]-mediated reductive activation of CO 2 affording a Ni(κ 1-OCO) complex

DOE PAGES

Chiou, Tzung -Wen; Tseng, Yen -Ming; Lu, Tsai -Te; ...

2016-02-24

Here, carbon dioxide is expected to be employed as an inexpensive and potential feedstock of C 1 sources for the mass production of valuable chemicals and fuel. Versatile chemical transformations of CO 2, i.e. insertion of CO 2 producing bicarbonate/acetate/formate, cleavage of CO 2 yielding μ-CO/μ-oxo transition-metal complexes, and electrocatalytic reduction of CO 2 affording CO/HCOOH/CH 3OH/CH 4/C 2H 4/oxalate were well documented. Herein, we report a novel pathway for the reductive activation of CO 2 by the [Ni III(OMe)(P(C 6H 3-3-SiMe 3-2-S) 3)] – complex, yielding the [Ni III(κ 1-OCO˙ –)(P(C 6H 3-3-SiMe 3-2-S) 3)] – complex. The formationmore » of this unusual Ni III(κ 1-OCO ˙–) complex was characterized by single-crystal X-ray diffraction, EPR, IR, SQUID, Ni/S K-edge X-ray absorption spectroscopy, and Ni valence-to-core X-ray emission spectroscopy. The inertness of the analogous complexes [Ni III(SPh)], [Ni II(CO)], and [Ni II(N 2H 4)] toward CO 2, in contrast, demonstrates that the ionic [Ni III(OMe)] core attracts the binding of weak σ-donor CO 2 and triggers the subsequent reduction of CO 2 by the nucleophilic [OMe] – in the immediate vicinity. This metal–ligand cooperative activation of CO 2 may open a novel pathway promoting the subsequent incorporation of CO 2 in the buildup of functionalized products.« less

Thermodynamics of complexation in an aqueous solution of Tb(III) nitrate at 298 K

NASA Astrophysics Data System (ADS)

Lobacheva, O. L.; Berlinskii, I. V.; Dzhevaga, N. V.

2017-01-01

The pH of the formation of hydroxo complexes and hydrates in an aqueous solution of terbium Tb(III) is determined using combined means of potentiometric and conductometric titration. The stability constants of the hydroxo complexes, the products of hydroxide solubility, and the Gibbs energy of terbium hydroxo complex formation are calculated.

Comparative adsorption of Eu(III) and Am(III) on TPD.

PubMed

Fan, Q H; Zhao, X L; Ma, X X; Yang, Y B; Wu, W S; Zheng, G D; Wang, D L

2015-09-01

Comparative adsorption behaviors of Eu(III) and Am(III) on thorium phosphate diphosphate (TPD), i.e., Th4(PO4)4P2O7, have been studied using a batch approach and surface complexation model (SCM) in this study. The results showed that Eu(III) and Am(III) adsorption increased to a large extent with the increase in TPD dose. Strong pH-dependence was observed in both Eu(III) and Am(III) adsorption processes, suggesting that inner-sphere complexes (ISCs) were possibly responsible for the adsorption of Eu(III) and Am(III). Meanwhile, the adsorption of Eu(III) and Am(III) decreased to a different extent with the increase in ion strength, which was possibly related to outer-sphere complexes and/or ion exchange. In the presence of fulvic acid (FA), the adsorption of Eu(III) and Am(III) showed high enhancement mainly due to the ternary surface complexes of TPD-FA-Eu(3+) and TPD-FA-Am(3+). The SCM showed that one ion exchange (≡S3Am/Eu) and two ISCs (≡(XO)2Am/EuNO3 and ≡(YO)2Am/EuNO3) seemed more reasonable to quantitatively describe the adsorption edges of both Eu(III) and Am(III). Our findings obviously showed that Eu(III) could be a good analogue to study actinide behaviors in practical terms. However, it should be kept in mind that there are still obvious differences between the characteristics of Eu(III) and Am(III) in some special cases, for instance, the complex ability with organic matter and adsorption affinity to a solid surface.

Atpenins, potent and specific inhibitors of mitochondrial complex II (succinate-ubiquinone oxidoreductase)

PubMed Central

Miyadera, Hiroko; Shiomi, Kazuro; Ui, Hideaki; Yamaguchi, Yuichi; Masuma, Rokuro; Tomoda, Hiroshi; Miyoshi, Hideto; Osanai, Arihiro; Kita, Kiyoshi; Ōmura, Satoshi

2003-01-01

Enzymes in the mitochondrial respiratory chain are involved in various physiological events in addition to their essential role in the production of ATP by oxidative phosphorylation. The use of specific and potent inhibitors of complex I (NADH-ubiquinone reductase) and complex III (ubiquinol-cytochrome c reductase), such as rotenone and antimycin, respectively, has allowed determination of the role of these enzymes in physiological processes. However, unlike complexes I, III, and IV (cytochrome c oxidase), there are few potent and specific inhibitors of complex II (succinate-ubiquinone reductase) that have been described. In this article, we report that atpenins potently and specifically inhibit the succinate-ubiquinone reductase activity of mitochondrial complex II. Therefore, atpenins may be useful tools for clarifying the biochemical and structural properties of complex II, as well as for determining its physiological roles in mammalian tissues. PMID:12515859

Remarkable high efficiency of red emitters using Eu(iii) ternary complexes.

PubMed

Kalyakina, Alena S; Utochnikova, Valentina V; Zimmer, Manuel; Dietrich, Fabian; Kaczmarek, Anna M; Van Deun, Rik; Vashchenko, Andrey A; Goloveshkin, Alexander S; Nieger, Martin; Gerhards, Markus; Schepers, Ute; Bräse, Stefan

2018-05-17

We have synthesized Eu(iii) ternary complexes possessing record photoluminescence yields up to 90%. This high luminescence performance resulted from the absence of quenching moieties in the Eu coordination environment and an efficient energy transfer between ligands, combined with a particular symmetry of the coordination environment.

Structural and catalytic characterization of a heterovalent Mn(II)Mn(III) complex that mimics purple acid phosphatases.

PubMed

Smith, Sarah J; Riley, Mark J; Noble, Christopher J; Hanson, Graeme R; Stranger, Robert; Jayaratne, Vidura; Cavigliasso, Germán; Schenk, Gerhard; Gahan, Lawrence R

2009-11-02

The binuclear heterovalent manganese model complex [Mn(II)Mn(III)(L1)(OAc)(2)] ClO(4) x H(2)O (H(2)L1 = 2-(((3-((bis(pyridin-2-ylmethyl)amino)methyl)-2-hydroxy-5-methylbenzyl)(pyridin-2-ylmethyl)amino)-methyl)phenol) has been prepared and studied structurally, spectroscopically, and computationally. The magnetic and electronic properties of the complex have been related to its structure. The complex is weakly antiferromagnetically coupled (J approximately -5 cm(-1), H = -2J S(1) x S(2)) and the electron paramagnetic resonance (EPR) and magnetic circular dichroism (MCD) spectra identify the Jahn-Teller distortion of the Mn(III) center as predominantly a tetragonal compression, with a significant rhombic component. Electronic structure calculations using density functional theory have confirmed the conclusions derived from the experimental investigations. In contrast to isostructural M(II)Fe(III) complexes (M = Fe, Mn, Zn, Ni), the Mn(II)Mn(III) system is bifunctional possessing both catalase and hydrolase activities, and only one catalytically relevant pK(a) (= 8.2) is detected. Mechanistic implications are discussed.

DFT-based molecular modeling and vibrational study of the La(III) complex of 3,3'-(benzylidene)bis(4-hydroxycoumarin).

PubMed

Mihaylov, Tzvetan; Trendafilova, Natasha; Georgieva, Ivelina

2008-05-01

Molecular modeling of the La(III) complex of 3,3'-(benzylidene)bis(4-hydroxycoumarin) (PhDC) was performed using density functional theory (DFT) methods at B3LYP/6-31G(d) and BP86/TZP levels. Both Stuttgart-Dresden effective core potential and ZORA approximation were applied to the La(III) center. The electron density distribution and the nucleophilic centers of the deprotonated ligand PhDC(2-) in a solvent environment were estimated on the basis of Hirshfeld atomic charges, electrostatic potential values at the nuclei, and Nalewajski-Mrozek bond orders. In accordance with the empirical formula La(PhDC)(OH)(H(2)O), a chain structure of the complex was simulated by means of two types of molecular fragment: (1) two La(III) cations bound to one PhDC(2-) ligand, and (2) two PhDC(2-) ligands bound to one La(III) cation. Different orientations of PhDC(2-), OH(-) and H(2)O ligands in the La(III) complexes were investigated using 20 possible [La(PhDC(2-))(2)(OH)(H(2)O)](2-) fragments. Energy calculations predicted that the prism-like structure based on "tail-head" cis-LML2 type binding and stabilized via HO...HOH intramolecular hydrogen bonds is the most probable structure for the La(III) complex. The calculated vibrational spectrum of the lowest energy La(III) model fragment is in very good agreement with the experimental IR spectrum of the complex, supporting the suggested ligand binding mode to La(III) in a chain structure, namely, every PhDC(2-) interacts with two La(III) cations through both carbonylic and both hydroxylic oxygens, and every La(III) cation binds four oxygen atoms of two different PhDC(2-).

Structure and spectroscopic study of aqueous Fe(III)-As(V) complexes using UV-Vis, XAS and DFT-TDDFT.

PubMed

Chai, Liyuan; Yang, Jinqin; Zhang, Ning; Wu, Pin-Jiun; Li, Qingzhu; Wang, Qingwei; Liu, Hui; Yi, Haibo

2017-09-01

Aqueous complexes between ferric (Fe(III)) and arsenate (As(V)) are indispensable for understanding the mobility of arsenic (As) in Fe(III)-As(V)-rich systems. In this study, aqueous Fe(III)-As(V) complexes, FeH 2 AsO 4 2+ and FeHAsO 4 + , were postulated based on the qualitative analysis of UV-Vis spectra in both Fe(III)-As(V)-HClO 4 and Fe(III)-As(V)-H 2 SO 4 systems. Subsequently, monodentate structures were evidenced by Fe K-edge EXAFS and modeled as [FeH 2 AsO 4 (H 2 O) 5 ] 2+ and [FeHAsO 4 (H 2 O) 5 ] + by DFT. The feature band at ∼280 nm was verified as electron excitation chiefly from Fe-As-bridged O atoms to d-orbital of Fe in [FeH 2 AsO 4 (H 2 O) 5 ] 2+ and [FeHAsO 4 (H 2 O) 5 ] + . The structural and spectral information of Fe(III)-As(V) complexes will enable future speciation analysis in Fe(III)-As(V)-rich system. Copyright © 2017. Published by Elsevier Ltd.

Light-activated protein inhibition through photoinduced electron transfer of a ruthenium(II)–cobalt(III) bimetallic complex

DOE PAGES

Holbrook, Robert J.; Weinberg, David J.; Peterson, Mark D.; ...

2015-02-11

In this paper, we describe a mechanism of light activation that initiates protein inhibitory action of a biologically inert Co(III) Schiff base (Co(III)-sb) complex. Photoinduced electron transfer (PET) occurs from a Ru(II) bipyridal complex to a covalently attached Co(III) complex and is gated by conformational changes that occur in tens of nanoseconds. Reduction of the Co(III)-sb by PET initiates displacement of the inert axial imidazole ligands, promoting coordination to active site histidines of α-thrombin. Upon exposure to 455 nm light, the rate of ligand exchange with 4-methylimidazole, a histidine mimic, increases by approximately 5-fold, as observed by NMR spectroscopy. Similarly,more » the rate of α-thrombin inhibition increases over 5-fold upon irradiation. Finally, these results convey a strategy for light activation of inorganic therapeutic agents through PET utilizing redox-active metal centers.« less

Single-molecule magnetism in a family of {Co(III)2Dy(III)2} butterfly complexes: effects of ligand replacement on the dynamics of magnetic relaxation.

PubMed

Langley, Stuart K; Ungur, Liviu; Chilton, Nicholas F; Moubaraki, Boujemaa; Chibotaru, Liviu F; Murray, Keith S

2014-05-05

The synthesis and structural characterization of four related heterometallic complexes of formulas [Dy(III)2Co(III)2(OMe)2(teaH)2(O2CPh)4(MeOH)4](NO3)2·MeOH·H2O (1a) and [Dy(III)2Co(III)2(OMe)2(teaH)2(O2CPh)4(MeOH)2(NO3)2]·MeOH·H2O (1b), [Dy(III)2Co(III)2(OMe)2(dea)2(O2CPh)4(MeOH)4](NO3)2 (2), [Dy(III)2Co(III)2(OMe)2(mdea)2(O2CPh)4(NO3)2] (3), and [Dy(III)2Co(III)2(OMe)2(bdea)2(O2CPh)4(MeOH)4](NO3)2·0.5MeOH·H2O (4a) and [Dy(III)2Co(III)2(OMe)2(bdea)2(O2CPh)4(MeOH)2(NO3)2]·MeOH·1.5H2O (4b) are reported (teaH3 = triethanolamine, deaH2 = diethanolamine, mdeaH2 = N-methyldiethanolamine, and bdeaH2 = N-n-butyldiethanolamine). Compounds 1 (≡ 1a and 1b) and 4 (≡ 4a and 4b) both display two unique molecules within the same crystal and all compounds display a butterfly type core, with the Dy(III) ions occupying the central body positions and the diamagnetic Co(III) ions the outer wing-tip sites. Compounds 1-4 were investigated via direct current and alternating current magnetic susceptibility measurements, and it was found that each complex displayed single-molecule magnet (SMM) behavior. All four compounds display unique coordination and geometric environments around the Dy(III) ions and it was found that each displays a different anisotropy barrier. Ab initio calculations were performed on 1-4 and these determined the low lying electronic structure of each Dy(III) ion and the magnetic interactions for each cluster. It was found that there was a strong correlation between the calculated energy gap between the ground and first excited states of the single-ion ligand-field split Dy(III) levels and the experimentally observed anisotropy barrier. Furthermore, the transverse g factors found for the Dy(III) ions, defining the tunnelling rates within the ground Kramers doublets, are largest for 1, which agrees with the experimental observation of the shortest relaxation time in the high-temperature domain for this complex. The magnetic exchange between the Dy(III

Synthesis, Photoluminescence Behavior of Green Light Emitting Tb(III) Complexes and Mechanistic Investigation of Energy Transfer Process.

PubMed

Bala, Manju; Kumar, Satish; Devi, Rekha; Khatkar, Avni; Taxak, V B; Boora, Priti; Khatkar, S P

2018-06-04

A series of five new terbium(III) ion complexes with 4,4-difluoro-1-phenylbutane-1,3-dione (HDPBD) and anciliary ligands was synthesized. The composition and properties of complexes were analyzed by elemental analysis, IR, NMR, powder X-ray diffaraction, TG-DTG and photoluminescence spectroscopy. These complexes exhibited ligand sensitized green emission at 546 nm associated with 5 D 4  →  7 F 5 transitions of terbium ion in the emission spectra. The photoluminescence study manifested that the organic ligands act as antenna and facilitate the absorbed energy to emitting levels of Tb(III) ion efficiently. The enhanced luminescence intensity and decay time of ternary C2-C5 complexes observed due to synergistic effect of anciliary ligands. The CIE color coordinates of complexes came under the green region of chromaticity diagram. The mechanistic investigation of intramolecular energy transfer in the complexes was discussed in detail. These terbium(III) complexes can be thrivingly used as one of the green component in light emitting material and in display devices. Graphical Abstract Illustrate the sensitization process of the Tb ion and intramolecular energy transfer process in the Tb 3+ complex.

Reactivity of molecular dioxygen towards a series of isostructural dichloroiron(III) complexes with tripodal tetraamine ligands: general access to mu-oxodiiron(III) complexes and effect of alpha-fluorination on the reaction kinetics.

PubMed

Thallaj, Nasser K; Rotthaus, Olaf; Benhamou, Leila; Humbert, Nicolas; Elhabiri, Mourad; Lachkar, Mohammed; Welter, Richard; Albrecht-Gary, Anne-Marie; Mandon, Dominique

2008-01-01

We have synthesized the mono, di-, and tri-alpha-fluoro ligands in the tris(2-pyridylmethyl)amine (TPA) series, namely, FTPA, F(2)TPA and F(3)TPA, respectively. Fluorination at the alpha-position of these nitrogen-containing tripods shifts the oxidation potential of the ligand by 45-70 mV per added fluorine atom. The crystal structures of the dichloroiron(II) complexes with FTPA and F(2)TPA reveal that the iron center lies in a distorted octahedral geometry comparable to that already found in TPAFeCl(2). All spectroscopic data indicate that the geometry is retained in solution. These three isostructural complexes all react with molecular dioxygen to yield stable mu-oxodiiron(III) complexes. Crystal structure analyses are reported for each of these three mu-oxo compounds. With TPA, a symmetrical structure is obtained for a dicationic compound with the tripod coordinated in the kappa(4)N coordination mode. With FTPA, the compound is a neutral mu-oxodiiron(III) complex with a kappa(3)N coordination mode of the ligand. Oxygenation of the F(2)TPA complex gave a neutral unsymmetrical compound, the structure of which is reminiscent of that already found with the trifluorinated ligand. On reduction, all mu-oxodiiron(III) complexes revert to the starting iron(II) species. The oxygenation reaction parallels the well-known formation of mu-oxo derivatives from dioxygen in the chemistry of porphyrins reported almost three decades ago. The striking feature of the series of iron(II) precursors is the effect of the ligand on the kinetics of oxygenation of the complexes. Whereas the parent complex undergoes 90 % conversion over 40 h, the monofluorinated ligand provides a complex that has fully reacted after 30 h, whereas the reaction time for the complex with the difluorinated ligand is only 10 h. Analysis of the spectroscopic data reveals that formation of the mu-oxo complexes proceeds in two distinct reversible kinetic steps with k(1) approximately 10 k(2). For TPAFeCl(2) and

Synthesis, characterization, and binding assessment with human serum albumin of three bipyridine lanthanide(III) complexes.

PubMed

Aramesh-Boroujeni, Zahra; Bordbar, Abdol-Khalegh; Khorasani-Motlagh, Mozhgan; Sattarinezhad, Elham; Fani, Najme; Noroozifar, Meissam

2018-05-18

In this work, the terbium(III), dysprosium(III), and ytterbium(III) complexes containing 2, 2'-bipyridine (bpy) ligand have been synthesized and characterized using CHN elemental analysis, FT-IR, UV-Vis and 1 H-NMR techniques and their binding behavior with human serum albumin (HSA) was studied by UV-Vis, fluorescence and molecular docking examinations. The experimental data indicated that all three lanthanide complexes have high binding affinity to HSA with effective quenching of HSA fluorescence via static mechanism. The binding parameters, the type of interaction, the value of resonance energy transfer, and the binding distance between complexes and HSA were estimated from the analysis of fluorescence measurements and Förster theory. The thermodynamic parameters suggested that van der Waals interactions and hydrogen bonds play an important role in the binding mechanism. While, the energy transfer from HSA molecules to all these complexes occurs with high probability, the order of binding constants (BpyTb > BpyDy > BpyYb) represents the importance of radius of Ln 3+ ion in the complex-HSA interaction. The results of molecular docking calculation and competitive experiments assessed site 3 of HSA, located in subdomain IB, as the most probable binding site for these ligands and also indicated the microenvironment residues around the bound mentioned complexes. The computational results kept in good agreement with experimental data.

Systematic theoretical investigation of the zero-field splitting in Gd(III) complexes: Wave function and density functional approaches

NASA Astrophysics Data System (ADS)

Khan, Shehryar; Kubica-Misztal, Aleksandra; Kruk, Danuta; Kowalewski, Jozef; Odelius, Michael

2015-01-01

The zero-field splitting (ZFS) of the electronic ground state in paramagnetic ions is a sensitive probe of the variations in the electronic and molecular structure with an impact on fields ranging from fundamental physical chemistry to medical applications. A detailed analysis of the ZFS in a series of symmetric Gd(III) complexes is presented in order to establish the applicability and accuracy of computational methods using multiconfigurational complete-active-space self-consistent field wave functions and of density functional theory calculations. The various computational schemes are then applied to larger complexes Gd(III)DOTA(H2O)-, Gd(III)DTPA(H2O)2-, and Gd(III)(H2O)83+ in order to analyze how the theoretical results compare to experimentally derived parameters. In contrast to approximations based on density functional theory, the multiconfigurational methods produce results for the ZFS of Gd(III) complexes on the correct order of magnitude.

Redox homeostasis and respiratory metabolism in camels (Camelus dromedaries): comparisons with domestic goats and laboratory rats and mice.

PubMed

Al-Otaiba, Amna; John, Annie; Al-Belooshi, Thekra; Raza, Haider

2010-11-01

We have previously reported the occurrence of multiple forms of drug-metabolizing enzymes in camel tissues. Here, we investigate glutathione (GSH)-dependent redox homeostasis, reactive oxygen species (ROS) production and mitochondrial respiratory functions in camel tissues and compare them with imported domestic goats and laboratory rats and mice. Cytochrome P450 2E1 (CYP 2E1) and GSH-metabolizing enzymes were differentially expressed in the liver and kidney of these animals. Camel liver has significantly lower GSH pool than that in goats, rats and mice. Mitochondria isolated from the tissues of these animals showed a comparable ability to metabolize specific substrates for respiratory enzyme complexes I, II/III and IV. These complexes were metabolically more active in the kidney than in the liver of all the species. Furthermore, the activity of complex IV in camel tissues was significantly lower than in other species. On the other hand, complex II/III activity in camel kidney was higher compared to the other species. In addition, as expected, we observed that inhibitors of these enzyme complexes augment the production of mitochondrial ROS in camel and goat tissues. These results help to better understand the metabolic ability and adaptation in desert camels in comparison with domestic goats and laboratory rats and mice since they are exposed to different environmental and dietary conditions. Our study may also have implications in the pharmacology and toxicology of drugs and pollutants in these species.

Structure of the membrane domain of respiratory complex I.

PubMed

Efremov, Rouslan G; Sazanov, Leonid A

2011-08-07

Complex I is the first and largest enzyme of the respiratory chain, coupling electron transfer between NADH and ubiquinone to the translocation of four protons across the membrane. It has a central role in cellular energy production and has been implicated in many human neurodegenerative diseases. The L-shaped enzyme consists of hydrophilic and membrane domains. Previously, we determined the structure of the hydrophilic domain. Here we report the crystal structure of the Esherichia coli complex I membrane domain at 3.0 Å resolution. It includes six subunits, NuoL, NuoM, NuoN, NuoA, NuoJ and NuoK, with 55 transmembrane helices. The fold of the homologous antiporter-like subunits L, M and N is novel, with two inverted structural repeats of five transmembrane helices arranged, unusually, face-to-back. Each repeat includes a discontinuous transmembrane helix and forms half of a channel across the membrane. A network of conserved polar residues connects the two half-channels, completing the proton translocation pathway. Unexpectedly, lysines rather than carboxylate residues act as the main elements of the proton pump in these subunits. The fourth probable proton-translocation channel is at the interface of subunits N, K, J and A. The structure indicates that proton translocation in complex I, uniquely, involves coordinated conformational changes in six symmetrical structural elements.

Gold(III) complexes with ONS-Tridentate thiosemicarbazones: Toward selective trypanocidal drugs.

PubMed

Rettondin, Andressa R; Carneiro, Zumira A; Gonçalves, Ana C R; Ferreira, Vanessa F; Oliveira, Carolina G; Lima, Angélica N; Oliveira, Ronaldo J; de Albuquerque, Sérgio; Deflon, Victor M; Maia, Pedro I S

2016-09-14

Tridentate thiosemicarbazone ligands with an ONS donor set, H2L(R) (R = Me and Et) were prepared by reactions of 1-phenyl-1,3-butanedione with 4-R-3-thiosemicarbazides. H2L(R) reacts with Na[AuCl4]·2H2O in MeOH in a 1:1 M ratio under formation of green gold(III) complexes of composition [AuCl(L(R))]. These compounds represent the first examples of gold(III) complexes with ONS chelate-bonded thiosemicarbazones. The in vitro anti-Trypanosoma cruzi activity against both trypomastigote and amastigote forms (IC50try/ama) of CL Brener strains as well as the cytotoxicity against LLC-MK2 cells of the free ligands and complexes was evaluated. The complex [AuCl(L(Me))] was found to be more active and more selective than its precursor ligand and the standard drug benznidazole with a SItry/ama value higher than 200, being considered as a lead candidate for Chagas disease treatment. Moreover the in vitro activity against the replicative amastigote form (IC50ama) of T. cruzi was additionally investigated revealing that [AuCl(L(Me))] was also more potent than benznidazole still with a similar selectivity index. Finally, docking studies showed that free ligands and complexes interact with the same residues of the parasite protease cruzain but with different intensities, suggesting that this protease could be a possible target for the trypanocidal action of the obtained compounds. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

A rhodium(III) complex inhibits LPS-induced nitric oxide production and angiogenic activity in cellulo.

PubMed

Liu, Li-Juan; Lin, Sheng; Chan, Daniel Shiu-Hin; Vong, Chi Teng; Hoi, Pui Man; Wong, Chun-Yuen; Ma, Dik-Lung; Leung, Chung-Hang

2014-11-01

Metal-containing complexes have arisen as viable alternatives to organic molecules as therapeutic agents. Metal complexes possess a number of advantages compared to conventional carbon-based compounds, such as distinct geometries, interesting electronic properties, variable oxidation states and the ability to arrange different ligands around the metal centre in a precise fashion. Meanwhile, nitric oxide (NO) plays key roles in the regulation of angiogenesis, vascular permeability and inflammation. We herein report a novel cyclometalated rhodium(III) complex as an inhibitor of lipopolysaccharides (LPS)-induced NO production in RAW264.7 macrophages. Experiments suggested that the inhibition of NO production in cells by complex 1 was mediated through the down-regulation of nuclear factor-κB (NF-κB) activity. Furthermore, complex 1 inhibited angiogenesis in human umbilical vein endothelial cells (HUVECs) as revealed by an endothelial tube formation assay. This study demonstrates that kinetically inert rhodium(III) complexes may be potentially developed as effective anti-angiogenic agents. Copyright © 2014 Elsevier Inc. All rights reserved.

Use of whole-exome sequencing to determine the genetic basis of multiple mitochondrial respiratory chain complex deficiencies.

PubMed

Taylor, Robert W; Pyle, Angela; Griffin, Helen; Blakely, Emma L; Duff, Jennifer; He, Langping; Smertenko, Tania; Alston, Charlotte L; Neeve, Vivienne C; Best, Andrew; Yarham, John W; Kirschner, Janbernd; Schara, Ulrike; Talim, Beril; Topaloglu, Haluk; Baric, Ivo; Holinski-Feder, Elke; Abicht, Angela; Czermin, Birgit; Kleinle, Stephanie; Morris, Andrew A M; Vassallo, Grace; Gorman, Grainne S; Ramesh, Venkateswaran; Turnbull, Douglass M; Santibanez-Koref, Mauro; McFarland, Robert; Horvath, Rita; Chinnery, Patrick F

2014-07-02

Mitochondrial disorders have emerged as a common cause of inherited disease, but their diagnosis remains challenging. Multiple respiratory chain complex defects are particularly difficult to diagnose at the molecular level because of the massive number of nuclear genes potentially involved in intramitochondrial protein synthesis, with many not yet linked to human disease. To determine the molecular basis of multiple respiratory chain complex deficiencies. We studied 53 patients referred to 2 national centers in the United Kingdom and Germany between 2005 and 2012. All had biochemical evidence of multiple respiratory chain complex defects but no primary pathogenic mitochondrial DNA mutation. Whole-exome sequencing was performed using 62-Mb exome enrichment, followed by variant prioritization using bioinformatic prediction tools, variant validation by Sanger sequencing, and segregation of the variant with the disease phenotype in the family. Presumptive causal variants were identified in 28 patients (53%; 95% CI, 39%-67%) and possible causal variants were identified in 4 (8%; 95% CI, 2%-18%). Together these accounted for 32 patients (60% 95% CI, 46%-74%) and involved 18 different genes. These included recurrent mutations in RMND1, AARS2, and MTO1, each on a haplotype background consistent with a shared founder allele, and potential novel mutations in 4 possible mitochondrial disease genes (VARS2, GARS, FLAD1, and PTCD1). Distinguishing clinical features included deafness and renal involvement associated with RMND1 and cardiomyopathy with AARS2 and MTO1. However, atypical clinical features were present in some patients, including normal liver function and Leigh syndrome (subacute necrotizing encephalomyelopathy) seen in association with TRMU mutations and no cardiomyopathy with founder SCO2 mutations. It was not possible to confidently identify the underlying genetic basis in 21 patients (40%; 95% CI, 26%-54%). Exome sequencing enhances the ability to identify

Synthesis, Structure, and Antiproliferative Activity of Three Gallium(III) Azole Complexes

PubMed Central

Zanias, Stergios; Papaefstathiou, Giannis S.; Raptopoulou, Catherine P.; Papazisis, Konstantinos T.; Vala, Vasiliki; Zambouli, Dimitra; Kortsaris, Alexandros H.; Kyriakidis, Dimitrios A.; Zafiropoulos, Theodoros F.

2010-01-01

As part of our interest into the bioinorganic chemistry of gallium, gallium(III) complexes of the azole ligands 2,1,3-benzothiadiazole (btd), 1,2,3-benzotriazole (btaH), and 1-methyl-4,5-diphenylimidazole (L) have been isolated. Reaction of btaH or btd with GaBr3 or GaCl3 resulted in the mononuclear complexes [GaBr3(btaH)2] (1) and [GaCl3(btd)2] (2), respectively, while treatment of GaCl3 with L resulted in the anionic complex (LH)2[GaCl4] (3). All three complexes were characterized by single-crystal X-ray crystallography and IR spectroscopy, while their antiproliferative activities were investigated against a series of human and mouse cancer cell lines. PMID:20721278

Automated respiratory cycles selection is highly specific and improves respiratory mechanics analysis.

PubMed

Rigo, Vincent; Graas, Estelle; Rigo, Jacques

2012-07-01

Selected optimal respiratory cycles should allow calculation of respiratory mechanic parameters focusing on patient-ventilator interaction. New computer software automatically selecting optimal breaths and respiratory mechanics derived from those cycles are evaluated. Retrospective study. University level III neonatal intensive care unit. Ten mins synchronized intermittent mandatory ventilation and assist/control ventilation recordings from ten newborns. The ventilator provided respiratory mechanic data (ventilator respiratory cycles) every 10 secs. Pressure, flow, and volume waves and pressure-volume, pressure-flow, and volume-flow loops were reconstructed from continuous pressure-volume recordings. Visual assessment determined assisted leak-free optimal respiratory cycles (selected respiratory cycles). New software graded the quality of cycles (automated respiratory cycles). Respiratory mechanic values were derived from both sets of optimal cycles. We evaluated quality selection and compared mean values and their variability according to ventilatory mode and respiratory mechanic provenance. To assess discriminating power, all 45 "t" values obtained from interpatient comparisons were compared for each respiratory mechanic parameter. A total of 11,724 breaths are evaluated. Automated respiratory cycle/selected respiratory cycle selections agreement is high: 88% of maximal κ with linear weighting. Specificity and positive predictive values are 0.98 and 0.96, respectively. Averaged values are similar between automated respiratory cycle and ventilator respiratory cycle. C20/C alone is markedly decreased in automated respiratory cycle (1.27 ± 0.37 vs. 1.81 ± 0.67). Tidal volume apparent similarity disappears in assist/control: automated respiratory cycle tidal volume (4.8 ± 1.0 mL/kg) is significantly lower than for ventilator respiratory cycle (5.6 ± 1.8 mL/kg). Coefficients of variation decrease for all automated respiratory cycle parameters in all infants. "t

X-ray diffraction, FTIR, UV-VIS and SEM studies on chromium (III) complexes

NASA Astrophysics Data System (ADS)

Mishra, Ashutosh; Dwivedi, Jagrati; Shukla, Kritika

2015-06-01

Five Chromium (III) complexes have been prepared using Schiff base ligands which derived from benzoin and five different amino acids (H2N-R). Samples were characterized by XRD, FTIR, UV-VIS and SEM method. X-Ray diffraction pattern analyzed that all chromium (III) complexes have hexagonal structure and crystalline, in nature, using Bruker D8 Advance instrument. Using VERTAX 70, FTIR spectroscopy reveals that Samples have (C=N), (C-O), (M-N) and (M-O) bonds in the range of 4000-400cm-1. UV-VIS spectroscopy give information that samples absorb the visible light which is in the range of 380-780nm. For this, Lambda 960 spectrometer used. SEM is designed for studying of the solid objects, using JEOL JSM 5600 instrument.

Synthesis, characterization, DNA binding and catalytic applications of Ru(III) complexes.

PubMed

Shoair, A F; El-Shobaky, A R; Azab, E A

2015-01-01

A new series of azodye ligands 5-chloro-3-hydroxy-4-(aryldiazenyl)pyridin-2(1H)-one (HLn) were synthesized by coupling of 5-chloro-3-hydroxypyridin-2(1H)-one with aniline and its p-derivatives. These ligands and their Ru(III) complexes of the type trans-[Ru(Ln)2(AsPh3)2]Cl were characterized by elemental analyses, IR, (1)H NMR and UV-Visible spectra as well as magnetic and thermal measurements. The molar conductance measurements proved that all the complexes are electrolytes. IR spectra show that the ligands (HLn) acts as a monobasic bidentate ligand by coordinating via the nitrogen atom of the azo group (NN) and oxygen atom of the deprotonated phenolic OH group, thereby forming a six-membered chelating ring and concomitant formation of an intramolecular hydrogen bond. The molecular and electronic structures of the investigated compounds (HLn) were also studied using quantum chemical calculations. The calf thymus DNA binding activity of the ligands (HLn) and their Ru(III) complexes were studied by absorption spectra and viscosity measurements. The mechanism and the catalytic oxidation of benzyl alcohol by trans-[Ru(Ln)2(AsPh3)2]Cl with hydrogen peroxide as co-oxidant were described. Copyright © 2015 Elsevier B.V. All rights reserved.

Single crystal X- and Q-band EPR spectroscopy of a binuclear Mn(2)(III,IV) complex relevant to the oxygen-evolving complex of photosystem II.

PubMed

Yano, Junko; Sauer, Kenneth; Girerd, Jean-Jacques; Yachandra, Vittal K

2004-06-23

The anisotropic g and hyperfine tensors of the Mn di-micro-oxo complex, [Mn(2)(III,IV)O(2)(phen)(4)](PF(6))(3).CH(3)CN, were derived by single-crystal EPR measurements at X- and Q-band frequencies. This is the first simulation of EPR parameters from single-crystal EPR spectra for multinuclear Mn complexes, which are of importance in several metalloenzymes; one of them is the oxygen-evolving complex in photosystem II (PS II). Single-crystal [Mn(2)(III,IV)O(2)(phen)(4)](PF(6))(3).CH(3)CN EPR spectra showed distinct resolved (55)Mn hyperfine lines in all crystal orientations, unlike single-crystal EPR spectra of other Mn(2)(III,IV) di-micro-oxo bridged complexes. We measured the EPR spectra in the crystal ab- and bc-planes, and from these spectra we obtained the EPR spectra of the complex along the unique a-, b-, and c-axes of the crystal. The crystal orientation was determined by X-ray diffraction and single-crystal EXAFS (Extended X-ray Absorption Fine Structure) measurements. In this complex, the three crystallographic axes, a, b, and c, are parallel or nearly parallel to the principal molecular axes of Mn(2)(III,IV)O(2)(phen)(4) as shown in the crystallographic data by Stebler et al. (Inorg. Chem. 1986, 25, 4743). This direct relation together with the resolved hyperfine lines significantly simplified the simulation of single-crystal spectra in the three principal directions due to the reduction of free parameters and, thus, allowed us to define the magnetic g and A tensors of the molecule with a high degree of reliability. These parameters were subsequently used to generate the solution EPR spectra at both X- and Q-bands with excellent agreement. The anisotropic g and hyperfine tensors determined by the simulation of the X- and Q-band single-crystal and solution EPR spectra are as follows: g(x) = 1.9887, g(y) = 1.9957, g(z) = 1.9775, and hyperfine coupling constants are A(III)(x) = |171| G, A(III)(y) = |176| G, A(III)(z) = |129| G, A(IV)(x) = |77| G, A

Eu(III) complexes as Anion-responsive Luminescent Sensors and PARACEST Agents

PubMed Central

Hammell, Jacob; Buttarazzi, Leandro; Huang, Ching-Hui; Morrow, Janet R.

2011-01-01

The Eu(III) complex of (1S,4S,7S,10S)-1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane (S-THP) is studied as a sensor for biologically relevant anions. Anion interactions produce changes in the luminescence emission spectrum of the Eu(III) complex, in the 1H NMR spectrum, and correspondingly, in the PARACEST spectrum of the complex (PARACEST = paramagnetic chemical exchange saturation transfer). Direct excitation spectroscopy and luminescence lifetime studies of Eu(S-THP) give information about the speciation and nature of anion interactions including carbonate, acetate, lactate, citrate, phosphate and methylphosphate at pH 7.2. Data is consistent with the formation of both innersphere and outersphere complexes of Eu(S-THP) with acetate, lactate and carbonate. These anions have weak dissociation constants that range from 19–38 mM. Citrate binding to Eu(S-THP) is predominantly innersphere with a dissociation constant of 17 μM. Luminescence emission peak changes upon addition of anion to Eu(S-THP) show that there are two distinct binding events for phosphate and methylphosphate with dissociation constants of 0.3 mM and 3.0 mM for phosphate and 0.6 mM and 9.8 mM for methyl phosphate. Eu(THPC) contains an appended carbostyril derivative as an antenna to sensitize Eu(III) luminescence. Eu(THPC) binds phosphate and citrate with dissociation constants that are 10-fold less than that of the Eu(S-THP) parent, suggesting that functionalization through a pendent group disrupts the anion binding site. Eu(S-THP) functions as an anion responsive PARACEST agent through exchange of the alcohol protons with bulk water. The alcohol proton resonances of Eu(S-THP) shift downfield in the presence of acetate, lactate, citrate and methylphosphate, giving rise to distinct PARACEST peaks. In contrast, phosphate binds to Eu(S-THP) to suppress the PARACEST alcohol OH peak and carbonate does not markedly change the alcohol peak at 5 mM Eu(S-THP), 15 mM carbonate at pH 6

Rapid screening for nuclear genes mutations in isolated respiratory chain complex I defects.

PubMed

Pagniez-Mammeri, Hélène; Lombes, Anne; Brivet, Michèle; Ogier-de Baulny, Hélène; Landrieu, Pierre; Legrand, Alain; Slama, Abdelhamid

2009-04-01

Complex I or reduced nicotinamide adenine dinucleotide (NADH): ubiquinone oxydoreductase deficiency is the most common cause of respiratory chain defects. Molecular bases of complex I deficiencies are rarely identified because of the dual genetic origin of this multi-enzymatic complex (nuclear DNA and mitochondrial DNA) and the lack of phenotype-genotype correlation. We used a rapid method to screen patients with isolated complex I deficiencies for nuclear genes mutations by Surveyor nuclease digestion of cDNAs. Eight complex I nuclear genes, among the most frequently mutated (NDUFS1, NDUFS2, NDUFS3, NDUFS4, NDUFS7, NDUFS8, NDUFV1 and NDUFV2), were studied in 22 cDNA fragments spanning their coding sequences in 8 patients with a biochemically proved complex I deficiency. Single nucleotide polymorphisms and missense mutations were detected in 18.7% of the cDNA fragments by Surveyor nuclease treatment. Molecular defects were detected in 3 patients. Surveyor nuclease screening is a reliable method for genotyping nuclear complex I deficiencies, easy to interpret, and limits the number of sequence reactions. Its use will enhance the possibility of prenatal diagnosis and help us for a better understanding of complex I molecular defects.

Managing complex respiratory patients in the community: an evaluation of a pilot integrated respiratory care service.

PubMed

Gillett, K; Lippiett, K; Astles, C; Longstaff, J; Orlando, R; Lin, S X; Powell, A; Roberts, C; Chauhan, A J; Thomas, M; Wilkinson, T M

2016-01-01

In the UK, there is significant variation in respiratory care and outcomes. An integrated approach to the management of high-risk respiratory patients, incorporating specialist and primary care teams' expertise, is the basis for new integrated respiratory services designed to reduce this variation; however, this model needs evaluating. To evaluate an integrated service managing high-risk respiratory patients, electronic searches for patients with asthma and chronic obstructive pulmonary disease at risk of poor outcomes were performed in two general practitioner (GP) practices in a local service-development initiative. Patients were reviewed at joint clinics by primary and secondary care professionals. GPs also nominated patients for inclusion. Reviews were delivered to best standards of care including assessments of diagnosis, control, spirometry, self-management, education, medication, inhaler technique and smoking cessation support. Follow-up of routine clinical data collected at 9-months postclinic were compared with seasonally matched 9-months prior to integrated review. 82 patients were identified, 55 attended. 13 (23.6%) had their primary diagnosis changed. In comparison with the seasonally adjusted baseline period, in the 9-month follow-up there was an increase in inhaled corticosteroid prescriptions of 23.3%, a reduction in short-acting β 2 -agonist prescription of 33.3%, a reduction in acute respiratory exacerbations of 67.6%, in unscheduled GP surgery visits of 53.3% and acute respiratory hospital admissions reduced from 3 to 0. Only 4 patients (7.3%) required referral to secondary care. Health economic evaluation showed respiratory-related costs per patient reduced by £231.86. Patients with respiratory disease in this region at risk of suboptimal outcomes identified proactively and managed by an integrated team improved outcomes without the need for hospital referral.

Genomic Binding Profiles of Functionally Distinct RNA Polymerase III Transcription Complexes in Human Cells

PubMed Central

Moqtaderi, Zarmik; Wang, Jie; Raha, Debasish; White, Robert J.; Snyder, Michael; Weng, Zhiping; Struhl, Kevin

2012-01-01

Genome-wide occupancy profiles of five components of the RNA Polymerase III (Pol III) machinery in human cells identified the expected tRNA and non-coding RNA targets and revealed many additional Pol III-associated loci, mostly near SINEs. Several genes are targets of an alternative TFIIIB containing Brf2 instead of Brf1 and have extremely low levels of TFIIIC. Strikingly, expressed Pol III genes, unlike non-expressed Pol III genes, are situated in regions with a pattern of histone modifications associated with functional Pol II promoters. TFIIIC alone associates with numerous ETC loci, via the B box or a novel motif. ETCs are often near CTCF binding sites, suggesting a potential role in chromosome organization. Our results suggest that human Pol III complexes associate preferentially with regions near functional Pol II promoters and that TFIIIC-mediated recruitment of TFIIIB is regulated in a locus-specific manner. PMID:20418883

Development of a one-run real-time PCR detection system for pathogens associated with bovine respiratory disease complex.

PubMed

Kishimoto, Mai; Tsuchiaka, Shinobu; Rahpaya, Sayed Samim; Hasebe, Ayako; Otsu, Keiko; Sugimura, Satoshi; Kobayashi, Suguru; Komatsu, Natsumi; Nagai, Makoto; Omatsu, Tsutomu; Naoi, Yuki; Sano, Kaori; Okazaki-Terashima, Sachiko; Oba, Mami; Katayama, Yukie; Sato, Reiichiro; Asai, Tetsuo; Mizutani, Tetsuya

2017-03-18

Bovine respiratory disease complex (BRDC) is frequently found in cattle worldwide. The etiology of BRDC is complicated by infections with multiple pathogens, making identification of the causal pathogen difficult. Here, we developed a detection system by applying TaqMan real-time PCR (Dembo respiratory-PCR) to screen a broad range of microbes associated with BRDC in a single run. We selected 16 bovine respiratory pathogens (bovine viral diarrhea virus, bovine coronavirus, bovine parainfluenza virus 3, bovine respiratory syncytial virus, influenza D virus, bovine rhinitis A virus, bovine rhinitis B virus, bovine herpesvirus 1, bovine adenovirus 3, bovine adenovirus 7, Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, Trueperella pyogenes, Mycoplasma bovis and Ureaplasma diversum) as detection targets and designed novel specific primer-probe sets for nine of them. The assay performance was assessed using standard curves from synthesized DNA. In addition, the sensitivity of the assay was evaluated by spiking solutions extracted from nasal swabs that were negative by Dembo respiratory-PCR for nucleic acids of pathogens or synthesized DNA. All primer-probe sets showed high sensitivity. In this study, a total of 40 nasal swab samples from cattle on six farms were tested by Dembo respiratory-PCR. Dembo respiratory-PCR can be applied as a screening system with wide detection targets.

Slow magnetic relaxation and luminescence properties in lanthanide(iii)/anil complexes.

PubMed

Maniaki, Diamantoula; Mylonas-Margaritis, Ioannis; Mayans, Julia; Savvidou, Aikaterini; Raptopoulou, Catherine P; Bekiari, Vlasoula; Psycharis, Vassilis; Escuer, Albert; Perlepes, Spyros P

2018-05-22

The initial use of anils, i.e. bidentate Schiff bases derived from the condensation of anilines with salicylaldehyde or its derivatives, in 4f-metal chemistry is described. The 1 : 1 reactions between Ln(NO3)3·xH2O (Ln = lanthanide) or Y(NO3)3·6H2O and N-(5-bromosalicylidene)aniline (5BrsalanH) in MeCN has provided access to complexes [Ln(NO3)3(5BrsalanH)2(H2O)]·MeCN (Ln = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) and [Y(NO3)3(5BrsalanH)2(H2O)]·MeCN, respectively, in good yields. The structures of the isomorphous complexes with Ln = Pr(1·MeCN), Sm(3·MeCN), Gd(5·MeCN), Dy(7·MeCN) and Er(9·MeCN) have been determined by single-crystal X-ray crystallography. The other complexes were proven to be isostructural with the fully structurally characterized compounds based on elemental analyses, IR spectra, unit cell determinations and powder X-ray patterns. The 9-coordinate LnIII centre in the [Ln(NO3)3(5BrsalanH)2(H2O)] molecules is bound to six oxygen atoms from the three bidentate chelating nitrato groups, two oxygen atoms that belong to the organic ligands and one oxygen atom from the aquo ligand. The 5BrsalanH molecules behave as monodentate O-donors; the acidic H atom is clearly located on the imino N atom and thus the formally neutral ligands adopt an extremely rare coordination mode participating in the zwitterionic form. The coordination polyhedra defined by the nine donor atoms around the LnIII centres are best described as spherical capped square antiprisms. Various intermolecular interactions build the crystal structures and Hirshfeld surface analysis was applied to evaluate the magnitude of interactions between the molecules. Solid-state IR and UV/VIS data are discussed in terms of structural features. 1H NMR data prove that the diamagnetic [Y(NO3)3(5BrsalanH)2(H2O)] complex decomposes in DMSO. Combined dc and ac magnetic susceptibility, as well as magnetization data for 7 suggest that this complex shows field-induced slow magnetic relaxation. Two

Regulation of the Tumor-Suppressor Function of the Class III Phosphatidylinositol 3-Kinase Complex by Ubiquitin and SUMO.

PubMed

Reidick, Christina; El Magraoui, Fouzi; Meyer, Helmut E; Stenmark, Harald; Platta, Harald W

2014-12-23

The occurrence of cancer is often associated with a dysfunction in one of the three central membrane-involution processes-autophagy, endocytosis or cytokinesis. Interestingly, all three pathways are controlled by the same central signaling module: the class III phosphatidylinositol 3-kinase (PI3K-III) complex and its catalytic product, the phosphorylated lipid phosphatidylinositol 3-phosphate (PtdIns3P). The activity of the catalytic subunit of the PI3K-III complex, the lipid-kinase VPS34, requires the presence of the membrane-targeting factor VPS15 as well as the adaptor protein Beclin 1. Furthermore, a growing list of regulatory proteins associates with VPS34 via Beclin 1. These accessory factors define distinct subunit compositions and thereby guide the PI3K-III complex to its different cellular and physiological roles. Here we discuss the regulation of the PI3K-III complex components by ubiquitination and SUMOylation. Especially Beclin 1 has emerged as a highly regulated protein, which can be modified with Lys11-, Lys48- or Lys63-linked polyubiquitin chains catalyzed by distinct E3 ligases from the RING-, HECT-, RBR- or Cullin-type. We also point out other cross-links of these ligases with autophagy in order to discuss how these data might be merged into a general concept.

Cytotoxicity of Manganese (III) Complex in Human Breast Adenocarcinoma Cell Line Is Mediated by the Generation of Reactive Oxygen Species Followed by Mitochondrial Damage.

PubMed

Al-Anbaky, Qudes; Al-Karakooly, Zeiyad; Kilaparty, Surya P; Agrawal, Megha; Albkuri, Yahya M; RanguMagar, Ambar B; Ghosh, Anindya; Ali, Nawab

2016-11-01

Manganese (Mn) complexes are widely studied because of their important catalytic properties in synthetic and biochemical reactions. A Mn (III) complex of an amidoamine ligand was synthesized using a tetradentate amidoamine ligand. In this study, the Mn (III) complex was evaluated for its biological activity by measuring its cytotoxicity in human breast adenocarcinoma cell line (MCF-7). Cytotoxic effects of the Mn (III) complex were determined using established biomarkers in an attempt to delineate the mechanism of action and the utility of the complex as a potential anticancer drug. The Mn (III) complex induces cell death in a dose- and time-dependent manner as shown by microculture tetrazolium assay, a measure of cytotoxic cell death. Our results demonstrated that cytotoxic effects were significantly increased at higher concentrations of Mn (III) complex and with longer time of treatment. The IC 50 (Inhibitor concentration that results in 50% cell death) value of Mn (III) complex in MCF-7 cells was determined to be 2.5 mmol/L for 24 hours of treatment. In additional experiments, we determined the Mn (III) complex-mediated cell death was due to both apoptotic and nonspecific necrotic cell death mechanisms. This was assessed by ethidium bromide/acridine orange staining and flow cytometry techniques. The Mn (III) complex produced reactive oxygen species (ROS) triggering the expression of manganese superoxide dismutase 1 and ultimately damaging the mitochondrial function as is evident by a decline in mitochondrial membrane potential. Treatment of the cells with free radical scavenger, N, N-dimethylthiourea decreased Mn (III) complex-mediated generation of ROS and attenuated apoptosis. Together, these results suggest that the Mn (III) complex-mediated MCF-7 cell death utilizes combined mechanism involving apoptosis and necrosis perhaps due to the generation of ROS. © The Author(s) 2016.

Saturation kinetics in phenolic O-H bond oxidation by a mononuclear Mn(III)-OH complex derived from dioxygen.

PubMed

Wijeratne, Gayan B; Corzine, Briana; Day, Victor W; Jackson, Timothy A

2014-07-21

The mononuclear hydroxomanganese(III) complex, [Mn(III)(OH)(dpaq)](+), which is supported by the amide-containing N5 ligand dpaq (dpaq = 2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8-yl-acetamidate) was generated by treatment of the manganese(II) species, [Mn(II)(dpaq)](OTf), with dioxygen in acetonitrile solution at 25 °C. This oxygenation reaction proceeds with essentially quantitative yield (greater than 98% isolated yield) and represents a rare example of an O2-mediated oxidation of a manganese(II) complex to generate a single product. The X-ray diffraction structure of [Mn(III)(OH)(dpaq)](+) reveals a short Mn-OH distance of 1.806(13) Å, with the hydroxo moiety trans to the amide function of the dpaq ligand. No shielding of the hydroxo group is observed in the solid-state structure. Nonetheless, [Mn(III)(OH)(dpaq)](+) is remarkably stable, decreasing in concentration by only 10% when stored in MeCN at 25 °C for 1 week. The [Mn(III)(OH)(dpaq)](+) complex participates in proton-coupled electron transfer reactions with substrates with relatively weak O-H and C-H bonds. For example, [Mn(III)(OH)(dpaq)](+) oxidizes TEMPOH (TEMPOH = 2,2'-6,6'-tetramethylpiperidine-1-ol), which has a bond dissociation free energy (BDFE) of 66.5 kcal/mol, in MeCN at 25 °C. The hydrogen/deuterium kinetic isotope effect of 1.8 observed for this reaction implies a concerted proton-electron transfer pathway. The [Mn(III)(OH)(dpaq)](+) complex also oxidizes xanthene (C-H BDFE of 73.3 kcal/mol in dimethylsulfoxide) and phenols, such as 2,4,6-tri-t-butylphenol, with BDFEs of less than 79 kcal/mol. Saturation kinetics were observed for phenol oxidation, implying an initial equilibrium prior to the rate-determining step. On the basis of a collective body of evidence, the equilibrium step is attributed to the formation of a hydrogen-bonding complex between [Mn(III)(OH)(dpaq)](+) and the phenol substrates.

New mixed valence defect dicubane cobalt(II)/cobalt(III) complex: Synthesis, crystal structure, photoluminescence and magnetic properties

NASA Astrophysics Data System (ADS)

Coban, Mustafa Burak; Gungor, Elif; Kara, Hulya; Baisch, Ulrich; Acar, Yasemin

2018-02-01

A new defect dicubane cobalt(II)/cobalt(III), [(CoII2CoIII2L42(H2O)(CH3COO)(CH3COOH]. 4H2O complex (1) where H2L = [1-(3-hydroxypropyliminomethyl)naphthalene-2-ol], has been synthesized and characterized by element analysis, FT-IR, solid UV-Vis spectroscopy and single crystal X-ray diffraction. The crystal structure determination shows a cationic tetrameric arrangement consisting of a defect dicubane core with two missing vertexes. Each cobalt ion has a distorted octahedral geometry with six coordinate ordered CoII and CoIII ions. The solid state photoluminescence properties of complex (1) and its ligand H2L have been investigated under UV light at 349 nm in the visible region. H2L exhibits blue emission while complex (1) shows red emission at room temperature. Variable-temperature magnetic susceptibility measurements on the complex (1) in the range 2-300 K indicate an antiferromagnetic interaction.

Synthesis, characterization, photoluminescence and cytotoxic properties of novel luminescent Eu(III)complexes based on chromone Schiff base

NASA Astrophysics Data System (ADS)

Saif, M.; El-Shafiy, Hoda F.; Mashaly, Mahmoud M.; Eid, Mohamed F.; Nabeel, A. I.; Fouad, R.

2018-06-01

Three novel Eu(III) phosphor complexes, [Eu(HL)(OH2)2(C2H5OH)](NO3)2 (1), [Eu(HL)(Bpy)(NO3)2(EtOH)] (2) and [Eu(HL)(Phen)(NO3)2(H2O)] (3) (HL = (11E)-2-hydroxy-N/-((4-oxo-4H-chromen-3-yl)methylene)benzohydrazide; Bpy = 2,2/-bibyridyl and Phen = 1,10-phenanthroline) were prepared. Elemental, thermal, FT-IR and XRD methods were used to characterize their structural configuration. The HL behaves as a monoanionic tridentate ligand. The XRD analysis shows that the ligand and its Eu3+complexes are in nano domain. From fluorescence spectroscopy, all the prepared complexes are highly luminescent, having an impressive visual emission under UV excitation. The H2L and its Eu3+nano-complexes (1-3) were tested for their in vitro cytotoxicity against Ehrlich Ascites Carcinoma cell line (EAC). The Eu(III) nano-complexes (1-3) effectively inhibited EAC growth with IC50 value of 25 μM. The high antitumor activity of the Eu(III) nano-complexes (1-3) were attributed to its chemical structure, and nano size properties.

Risk of developing pneumonia is enhanced by the combined traits of fluoroquinolone resistance and type III secretion virulence in respiratory isolates of Pseudomonas aeruginosa.

PubMed

Sullivan, Eva; Bensman, Joyce; Lou, Mimi; Agnello, Melissa; Shriner, Kimberly; Wong-Beringer, Annie

2014-01-01

To determine the differential association of host characteristics, antimicrobial resistance, and type III secretion system virulence of Pseudomonas aeruginosa isolates with respiratory syndromes in hospitalized adult patients. Retrospective, cohort study. Community teaching hospital. Two hundred eighteen consecutive adult patients with respiratory culture positive for P. aeruginosa between January 2005 to January 2010. Medical charts were reviewed to obtain demographic, laboratory, radiographic, and clinical information. Isolates were assayed by polymerase chain reaction for genes encoding the type III secretion system effectors (ExoU, ExoS, and PcrV) and for strain relatedness using randomly amplified polymorphic DNA analysis. Levofloxacin susceptibility was determined by broth microdilution. Patients were grouped by colonization, bronchitis, or pneumonia and were compared for differential risk of developing the clinical syndrome with respect to host and microbial characteristics. Half of the study cohort (54%, 117 of 218) had pneumonia, 32% (70 of 218) had bronchitis, and 14% (31 of 218) had colonization; in-hospital mortality was 35%, 11%, and 0%, respectively. Host factors strongly associated with pneumonia development were residence in long-term care facility, healthcare-associated acquisition of P. aeruginosa, higher Acute Physiology and Chronic Health Evaluation II score, presence of enteral feeding tube, mechanical ventilation, and recent history of pneumonia. Fluoroquinolone-resistant (57% vs 34%, 16%; p < 0.0001) and multidrug-resistant (36% vs 26%, 7%; p = 0.0045) strains were more likely to cause pneumonia than bronchitis or colonization, respectively. Analysis of host and microbial factors in a multivariate regression model yielded the combined traits of fluoroquinolone resistance and gene encoding the type III secretion system ExoU effector in P. aeruginosa as the single most significant predictor of pneumonia development. These results suggest that

[FeIII(SR)4]1− Complexes Can Be Synthesized By the Direct Reaction of Thiolates With FeCl3**

PubMed Central

Chang, Sechin; Koch, Stephen A.

2007-01-01

It is shown that the previously characterized [FeIII(SR)4]1− (R= Et, i-Pr, Ph) complexes can be synthesized by the direct reaction of 4 equiv of LiSR with FeCl3 in DMF solution. [FeIII(SR)4]1− complexes are synthetic analogs for the [FeIII(S-Cys)4] center in rubredoxin proteins. PMID:17723243

A trinuclear oxo-chromium(III) complex containing the natural flavonoid primuletin: Synthesis, characterization, and antiradical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rocha, Reginaldo C.; Alexiou, Anamaria D.P.; Decandio, Carla C.

A new trinuclear oxo-centered chromium(III) complex with formula [Cr₃O(CH₃CO₂)₆(L)(H₂O)₂] (L = 5-hydroxyflavone, known as primuletin) was synthetized and characterized by ESI mass spectrometry, thermogravimetry, and ¹H-NMR, UV-Vis, and FTIR spectroscopies. In agreement with the experimental results, DFT calculations indicated that the flavonoid ligand is coordinated to one of the three Cr(III) centers in an O,O-bidentate mode through the 5-hydroxy/4-keto groups. In a comparative study involving the uncoordinated primuletin and its corresponding complex, systematic reactions with the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) showed that antiradical activity increases upon complexation.

A trinuclear oxo-chromium(III) complex containing the natural flavonoid primuletin: Synthesis, characterization, and antiradical properties

DOE PAGES

Rocha, Reginaldo C.; Alexiou, Anamaria D.P.; Decandio, Carla C.; ...

2015-04-10

A new trinuclear oxo-centered chromium(III) complex with formula [Cr₃O(CH₃CO₂)₆(L)(H₂O)₂] (L = 5-hydroxyflavone, known as primuletin) was synthetized and characterized by ESI mass spectrometry, thermogravimetry, and ¹H-NMR, UV-Vis, and FTIR spectroscopies. In agreement with the experimental results, DFT calculations indicated that the flavonoid ligand is coordinated to one of the three Cr(III) centers in an O,O-bidentate mode through the 5-hydroxy/4-keto groups. In a comparative study involving the uncoordinated primuletin and its corresponding complex, systematic reactions with the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) showed that antiradical activity increases upon complexation.

Novel polymer anchored Cr(III) Schiff base complexes: Synthesis, characterization and antimicrobial properties

NASA Astrophysics Data System (ADS)

Selvi, Canan; Nartop, Dilek

2012-09-01

New polymer-bound Schiff bases and Cr(III) complexes have been synthesized by the reaction of 4-benzyloxybenzaldehyde, polymer-bound with 2-aminophenol, 2-amino-4-chlorophenol and 2-amino-4-methylphenol. The structure of polymeric-Schiff bases and their Cr(III) complexes have been characterized by elemental analyses, magnetic measurements, IR, UV-Vis, TG-DTA and 1H-NMR. All these compounds have also been investigated for antibacterial activity by the well-diffusion method against Staphylococcus aureus (RSKK-07035), Shigella dysenteria type 10 (RSKK 1036), Listeria monocytogenes 4b(ATCC 19115, Escherichia coli (ATCC 1230), Salmonella typhi H (NCTC 901.8394), Staphylococcus epidermis (ATCC 12228), Brucella abortus (RSKK-03026), Micrococcs luteus (ATCC 93419, Bacillus cereus sp., Pseudomonas putida sp. and for antifungal activity against Candida albicans (Y-1200-NIH).

Genomic binding profiles of functionally distinct RNA polymerase III transcription complexes in human cells.

PubMed

Moqtaderi, Zarmik; Wang, Jie; Raha, Debasish; White, Robert J; Snyder, Michael; Weng, Zhiping; Struhl, Kevin

2010-05-01

Genome-wide occupancy profiles of five components of the RNA polymerase III (Pol III) machinery in human cells identified the expected tRNA and noncoding RNA targets and revealed many additional Pol III-associated loci, mostly near short interspersed elements (SINEs). Several genes are targets of an alternative transcription factor IIIB (TFIIIB) containing Brf2 instead of Brf1 and have extremely low levels of TFIIIC. Strikingly, expressed Pol III genes, unlike nonexpressed Pol III genes, are situated in regions with a pattern of histone modifications associated with functional Pol II promoters. TFIIIC alone associates with numerous ETC loci, via the B box or a novel motif. ETCs are often near CTCF binding sites, suggesting a potential role in chromosome organization. Our results suggest that human Pol III complexes associate preferentially with regions near functional Pol II promoters and that TFIIIC-mediated recruitment of TFIIIB is regulated in a locus-specific manner.

Complexation Effect on Redox Potential of Iron(III)-Iron(II) Couple: A Simple Potentiometric Experiment

ERIC Educational Resources Information Center

Rizvi, Masood Ahmad; Syed, Raashid Maqsood; Khan, Badruddin

2011-01-01

A titration curve with multiple inflection points results when a mixture of two or more reducing agents with sufficiently different reduction potentials are titrated. In this experiment iron(II) complexes are combined into a mixture of reducing agents and are oxidized to the corresponding iron(III) complexes. As all of the complexes involve the…

[Mitochondrial disease due to the deficit of Q-cytochrome C oxidoreductase coenzyme in the respiratory chain. Report of a new case].

PubMed

Roldán, S; Lluch, M D; Navarro Quesada, F J; Hevia, A

1995-01-01

Reference has been made in the literature of the variability in the clinical presentation of deficiency of complex III of the respiratory chain, identifying up to the moment, four groups, the first of which is characterized by hipotonia and wearness starting at variable ages. We report a new case of mitochondrial myopathy due to deficiency of this complex and included within this first group, and consider the importance of defining the clinical and histochemical characteristics of this polymorphous entity.

Thermodynamic stability, kinetic inertness and relaxometric properties of monoamide derivatives of lanthanide(III) DOTA complexes.

PubMed

Tei, Lorenzo; Baranyai, Zsolt; Gaino, Luca; Forgács, Attila; Vágner, Adrienn; Botta, Mauro

2015-03-28

A complete thermodynamic and kinetic solution study on lanthanide(III) complexes with monoacetamide (DOTAMA, L1) and monopropionamide (DOTAMAP, L2) derivatives of DOTA (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) was undertaken with the aim to elucidate their stability and inertness in aqueous media. The stability constants of GdL1 and GdL2 are comparable, whereas a more marked difference is found in the kinetic inertness of the two complexes. The formation of the Eu(III) and Ce(III) complexes takes place via the formation of the protonated intermediates which can deprotonate and transform into the final complex through a OH(-) assisted pathway. GdL2 shows faster rates of acid catalysed decomplexation with respect to GdL1, which has a kinetic inertness comparable to GdDOTA. Nevertheless, GdL2 is one order of magnitude more inert than GdDO3A. A novel DOTAMAP-based bifunctional chelating ligand and its deoxycholic acid derivative (L5) were also synthesized. Since the coordinated water molecule in GdL2 is characterized by an exchange rate ca. two orders of magnitude greater than in GdL1, the relaxivity of the macromolecular derivatives of L5 should not be limited by the slow water exchange process. The relaxometric properties of the supramolecular adduct of GdL5 with human serum albumin (HSA) were investigated in aqueous solution by measuring the magnetic field dependence of the (1)H relaxivity which, at 20 MHz and 298 K, shows a 430% increase over that of the unbound GdL5 chelate. Thus, Gd(III) complexes with DOTAMAP macrocyclic ligands can represent good candidates for the development of stable and highly effective bioconjugate systems for molecular imaging applications.

Spectroscopic and biological approach in the characterization of a novel 14-membered [N4] macrocyclic ligand and its palladium(II), platinum(II), ruthenium(III) and iridium(III) complexes.

PubMed

Rani, Soni; Kumar, Sumit; Chandra, Sulekh

2014-01-24

A novel, tetradentate nitrogen donor [N4] macrocyclic ligand, i.e. 3,5,14,16-tetramethyl-2,6,13,17-tetraazatricyclo[12,0,0(7-12)] cosa-1(22),2,5,7,9,11,13,16,18,20-decaene(L), has been synthesized and characterized by elemental analyses, IR, Mass, and (1)H NMR spectral studies. Complexes of Pd(II), Pt(II), Ru(III) and Ir(III) have been prepared and characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, Mass, electronic spectral and thermal studies. On the basis of molar conductance the complexes may be formulated as [PdL]Cl2, [PtL]Cl2, [Ru(L)Cl2]Cl and [Ir(L)Cl2]Cl. The complexes are insoluble in most common solvents, including water, ethanol, carbon tetrachloride and acetonitrile, but soluble in DMF/DMSO. The value of magnetic moment indicates that all the complexes are diamagnetic except Ru(III) complex which shows magnetic moment corresponding to one unpaired electron. The magnetic moment of Ru(III) complex is 1.73 B.M. at room temperature. The antimicrobial activities of ligand and its complexes have been screened in vitro, as growth inhibiting agents. The antifungal and antibacterial screening were carried out using Food Poison and Disc Diffusion Method against plant pathogenic fungi and bacteria Alternaria porri, Fusarium oxysporum, Xanthomonas compestris and Pseudomonas aeruginosa respectively. The compounds were dissolved in DMSO to get the required solutions. The required medium used for these activities was PDA and nutrient agar. Copyright © 2013 Elsevier B.V. All rights reserved.

Spectroscopic and biological approach in the characterization of a novel 14-membered [N4] macrocyclic ligand and its Palladium(II), Platinum(II), Ruthenium(III) and Iridium(III) complexes

NASA Astrophysics Data System (ADS)

Rani, Soni; Kumar, Sumit; Chandra, Sulekh

2014-01-01

A novel, tetradentate nitrogen donor [N4] macrocyclic ligand, i.e. 3,5,14,16-tetramethyl-2,6,13,17-tetraazatricyclo[12,0,07-12] cosa-1(22),2,5,7,9,11,13,16,18,20-decaene(L), has been synthesized and characterized by elemental analyses, IR, Mass, and 1H NMR spectral studies. Complexes of Pd(II), Pt(II), Ru(III) and Ir(III) have been prepared and characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, Mass, electronic spectral and thermal studies. On the basis of molar conductance the complexes may be formulated as [PdL]Cl2, [PtL]Cl2, [Ru(L)Cl2]Cl and [Ir(L)Cl2]Cl. The complexes are insoluble in most common solvents, including water, ethanol, carbon tetrachloride and acetonitrile, but soluble in DMF/DMSO. The value of magnetic moment indicates that all the complexes are diamagnetic except Ru(III) complex which shows magnetic moment corresponding to one unpaired electron. The magnetic moment of Ru(III) complex is 1.73 B.M. at room temperature. The antimicrobial activities of ligand and its complexes have been screened in vitro, as growth inhibiting agents. The antifungal and antibacterial screening were carried out using Food Poison and Disc Diffusion Method against plant pathogenic fungi and bacteria Alternaria porri, Fusarium oxysporum, Xanthomonas compestris and Pseudomonas aeruginosa respectively. The compounds were dissolved in DMSO to get the required solutions. The required medium used for these activities was PDA and nutrient agar.

The role of Te(IV) and Bi(III) chloride complexes in hydrothermal mass transfer: An X-ray absorption spectroscopic study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Etschmann, Barbara E.; Liu, Weihua; Pring, Allan

2016-05-01

Tellurium (Te) and bismuth (Bi) are two metal(loid)s often enriched together with gold (Au) in hydrothermal deposits; however the speciation and transport properties for these two metals in hydrothermal systems are poorly understood. We investigated the effect of chloride on the speciation of Te(IV) and Bi(III) in hydrothermal solutions using in-situ XAS spectroscopy. At ambient temperature, oxy-hydroxide complexes containing the [TeO3] moiety (e.g., H3TeO3+ under highly acidic conditions) predominate in salty solutions over a wide range in pH and salt concentrations. Te(IV)-Cl complexes only appear at pH(25 degrees C) <= 2 and high Cl- activity (>= 10). The highest ordermore » Te(IV) chloride complex detected is TeCl4(aq), and contains the [TeCl4] moiety. Upon heating to 199 degrees C, the Te(IV)-Cl complexes become more stable; however they still required highly acidic conditions which are likely to exist only in very limited environments in nature. At ambient temperature, Bi(III) is coordinated to 5.5(5) Cl atoms in high salinity, acidic (HCl >= 0.5 m) chloride solutions. This, combined with large EXAFS-derived structural disorder parameters, suggests that the Bi(III) complex is most likely present as both BiCl52- and BiCl63-. The number of Cl atoms coordinated to Bi(III) decreases with increasing temperature; at around 200 degrees C and above, Bi(III) is coordinated to three Cl atoms. Overall the data show that Te(IV) chloride complexes can be ignored in predicting Te mobility under oxidizing conditions in most geological environments, but that Bi(III) chloride complexes are expected to account for Bi mobility in acidic brines. New thermodynamic properties for Bi(III) chloride complexes are provided to improve reactive transport modeling of Bi up to 500 degrees C. Although higher order complexes such as BiCl52- and BiCl63- exist at ambient temperature, the BiCl3(aq) complex becomes the predominant chloride complex in saline solutions at T >= 200 degrees C.« less

Hydrothermal synthesis, crystal structure, luminescent and magnetic properties of a new mononuclear GdIII coordination complex

NASA Astrophysics Data System (ADS)

Coban, Mustafa Burak

2018-06-01

A new GdIII coordination complex, {[Gd(2-stp)2(H2O)6].2(4,4'-bipy).4(H2O)}, complex 1, (2-stp = 2-sulfoterephthalate anion and 4,4'-bipy = 4,4'-bipyridine), has been synthesized by hydrothermal method and characterized by elemental analysis, solid state UV-Vis and FT-IR spectroscopy, single-crystal X-ray diffraction, solid state photoluminescence and variable-temperature magnetic measurements. The crystal structure determination shows that GdIII ions are eight coordinated and adopt a distorted square-antiprismatic geometry. Molecules interacting through intra- and intermolecular (O-H⋯O, O-H⋯N) hydrogen bonds in complex 1, give rise to 3D hydrogen bonded structure and the discrete lattice 4,4'-bipy molecules occupy the channel of the 3D structure. π-π stacking interactions also exist 4,4'-bipy-4,4'-bipy and 4,4'-bipy-2-stp molecule rings in 3D structures. Additionally, solid state photoluminescence properties of complex 1 at room temperature have been investigated. Under the excitation of UV light (at 349 nm), the complex 1 exhibited green emissions (at 505 nm) of GdIII ion in the visible region. Furthermore, Variable-temperature magnetic susceptibility and isothermal magnetization as function of external magnetic field studies reveal that complex 1 displays possible antiferromagnetic interaction.

Theoretical Determination of Energy Transfer Processes and Influence of Symmetry in Lanthanide(III) Complexes: Methodological Considerations.

PubMed

Beltrán-Leiva, María J; Páez-Hernández, Dayán; Arratia-Pérez, Ramiro

2018-05-07

This work presents a theoretical protocol to analyze the symmetry effect on the allowed character of the transitions and to estimate the probability of energy transfer in lanthanide(III) complexes. For this purpose, a complete study was performed based on the multireference CASSCF/PT2 technique along with TDDFT, to build the energy level diagrams and determine the spectral overlap integrals, respectively. This approach was applied on a series of LnIII complexes, viz. [LnCl 3 (DMF) 2 (Dpq)]/[Ln(NO 3 ) 3 (DMF) 2 (Dpq)], where Ln = Sm III , Tb III , Er III /Eu III , Nd III and dpq = dipyridoquinoxaline, synthesized and characterized by Patra et al. ( Dalton Trans. 2015 , 44 ( 46 ), 19844 - 19855 ; CrystEngComm 2016 , 18 ( 23 ), 4313 - 4322 ; Inorg. Chim. Acta 2016 , 451 , 73 - 81 ). A fragmentation scheme was applied where both the ligand and the lanthanide fragments were treated separately but at the same level of theory. The symmetry analysis only partially reproduced the expected results, and a more detailed analysis of the crystal field became necessary. On the other hand, the most probable energy transfer pathways that take place in the complexes were elucidated from the energy gaps between the ligand-localized triplet state and the emitting levels of the lanthanide fragments. These gaps, which are related to the energy transfer rate, properly reproduced the trend reported experimentally for the best and worst yields. Finally, the spectral overlap integral was calculated from the emission spectra of the dpq ligand and the absorption spectra of the lanthanide fragment. The obtained values are in good agreement with the quantum yields calculated for the systems. The most remarkable aspect of this protocol was its ability to explain the emission and nonemission of the studied compounds.

Closed genomes and phenotypes of seven Histophilus somni isolates from beef calves with bovine respiratory disease complex

USDA-ARS?s Scientific Manuscript database

Background: Histophilus somni is a fastidious gram-negative opportunistic pathogenic Pasteurellacea that affects multiple organ systems and is one of three principle bacterial species contributing to bovine respiratory disease complex (BRDC) in North American feed yard cattle. BRDC outbreaks accoun...

Amphiphilic complexes of Ho(iii), Dy(iii), Tb(iii) and Eu(iii) for optical and high field magnetic resonance imaging.

PubMed

Harris, Michael; Henoumont, Céline; Peeters, Wannes; Toyouchi, Shuichi; Vander Elst, Luce; Parac-Vogt, Tatjana N

2018-05-29

Lanthanides, holmium(iii), dysprosium(iii), and terbium(iii), were coordinated to an amphiphilic DOTA bis-coumarin derivative and then further assembled with an amphiphilic europium(iii) DTPA bis-coumarin derivative into mono-disperse micelles. The self-assembled micelles were characterized and assessed for their potential as bimodal contrast agents for high field magnetic resonance and optical imaging applications. All micelles showed a high transverse relaxation (r2) of 46, 34, and 30 s-1 mM-1 at 500 MHz and 37 °C for Dy(iii), Ho(iii) and Tb(iii), respectively, which is a result of the high magnetic moment of these lanthanides and the long rotational correlation time of the micelles. The quantum yield in aqueous solution ranged from 1.8% for Tb/Eu to 1.4% for Dy/Eu and 1.0% for the Ho/Eu micelles. Multi-photon excited emission spectroscopy has shown that due to the two-photon absorption of the coumarin chromophore the characteristic Eu(iii) emission could be observed upon excitation at 800 nm, demonstrating the usefulness of the system for in vivo fluorescence imaging applications. To the best of our knowledge, this is the first example reporting the potential of a holmium(iii) chelate as a negative MRI contrast agent.

Synthesis, structure, DNA/protein binding, and cytotoxic activity of a rhodium(III) complex with 2,6-bis(2-benzimidazolyl)pyridine.

PubMed

Esteghamat-Panah, Roya; Hadadzadeh, Hassan; Farrokhpour, Hossein; Simpson, Jim; Abdolmaleki, Amir; Abyar, Fatemeh

2017-02-15

A new mononuclear rhodium(III) complex, [Rh(bzimpy)Cl 3 ] (bzimpy = 2,6-bis(2-benzimidazolyl)pyridine), was synthesized and characterized by elemental analysis and spectroscopic methods. The molecular structure of the complex was confirmed by single-crystal X-ray crystallography. The interaction of the complex with fish sperm DNA (FS-DNA) was investigated by UV spectroscopy, emission titration, and viscosity measurement in order to evaluate the possible DNA-binding mode and to calculate the corresponding DNA-binding constant. The results reveal that the Rh(III) complex interacts with DNA through groove binding mode with a binding affinity on the order of 10 4 . In addition, the binding of the Rh(III) complex to bovine serum albumin (BSA) was monitored by UV-Vis and fluorescence emission spectroscopy at different temperatures. The mechanism of the complex interaction was found to be static quenching. The thermodynamic parameters (ΔH, ΔS, and ΔG) obtained from the fluorescence spectroscopy data show that van der Waals interactions and hydrogen bonds play a major role in the binding of the Rh(III) complex to BSA. For the comparison of the DNA- and BSA-binding affinities of the free bzimpy ligand with its Rh(III) complex, the absorbance titration and fluorescence quenching experiments of the free bzimpy ligand with DNA and BSA were carried out. Competitive experiments using eosin Y and ibuprofen as site markers indicated that the complex was mainly located in the hydrophobic cavity of site I of the protein. These experimental results were confirmed by the results of molecular docking. Finally, the in vitro cytotoxicity properties of the Rh(III) complex against the MCF-7, K562, and HT-29 cell lines were evaluated and compared with those of the free ligand (bzimpy). It was found that the complexation process improved the anticancer activity significantly. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Synthesis and optoelectronic properties of a heterobimetallic Pt(II)-Ir(III) complex used as a single-component emitter in white PLEDs.

PubMed

Li, Xiaoshuang; Liu, Yu; Luo, Jian; Zhang, Zhiyong; Shi, Danyan; Chen, Qing; Wang, Yafei; He, Juan; Li, Jianming; Lei, Gangtie; Zhu, Weiguo

2012-03-14

To tune aggregation/excimer emission and obtain a single active emitter for white polymer light-emitting devices (PLEDs), a heterobimetallic Pt(II)-Ir(III) complex of FIr(pic)-C(6)DBC(6)-(pic)PtF was designed and synthesized, in which C(6)DBC(6) is a di(phenyloxyhexyloxy) bridging group, FIr(pic) is an iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C(2)'] (picolinate) chromophore and FPt(pic) is a platinum(II) [(4,6-difluorophenyl)pyridinato-N,C(2)'] (picolinate) chromophore. Its physical and opto-electronic properties were investigated. Interestingly, the excimer emission was efficiently controlled by this heterobimetallic Pt(II)-Ir(III) complex compared to the PL profile of the mononuclear FPt(pic) complex in the solid state. Near-white emissions were obtained in the single emissive layer (SEL) PLEDs using this heterobimetallic Pt(II)-Ir(III) complex as a single dopant and poly(vinylcarbazole) as a host matrix at dopant concentrations from 0.5 wt% to 2 wt%. This work indicates that incorporating a non-planar iridium(III) complex into the planar platinum(II) complex can control aggregation/excimer emissions and a single phosphorescent emitter can be obtained to exhibit white emission in SEL devices.

Assembly and Properties of Heterobimetallic CoII/III/CaII Complexes with Aquo and Hydroxo Ligands

PubMed Central

Lacy, David C.; Park, Young Jun; Ziller, Joseph W.; Yano, Junko; Borovik, A. S.

2012-01-01

The use of water as a reagent in redox-driven reactions is advantageous because it is abundant and environmentally compatible. The conversion of water to dioxygen in photosynthesis illustrates one example, in which a redox-inactive CaII ion and four manganese ions are required for function. In this report we describe the stepwise formation of two new heterobimetallic complexes containing CoII/III and CaII ions, and either hydroxo or aquo ligands. The preparation of a 4-coordinate CoII synthon was achieved with the tripodal ligand, N,N′,N″-[2,2′,2″-nitrilotris(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzenesulfonamido, [MST]3−. Water binds to [CoIIMST]− to form the 5-coordinate [CoIIMST(OH2)]− complex that was used to prepare the CoII/CaII complex [CoIIMST(μ-OH2)CaII⊂15-crown-5(OH2)]+ ([CoII(μ-OH2)CaIIOH2]+). [CoII(μ-OH2)CaOH2]+ contained two aquo ligands, one bonded to the CaII ion and one bridging between the two metal ions and thus represents an unusual example of a heterobimetallic complex containing 2 aquo ligands spanning different metal ions. Both aquo ligands formed intramolecular hydrogen bonds with the [MST]3− ligand. [CoIIMST(OH2)]− was oxidized to form [CoIIIMST(OH2)] that was further converted to [CoIIIMST(μ-OH)CaII⊂15-crown-5]+ ([CoIII(μ-OH)CaII]+) in the presence of base and CaIIOTf2/15-crown-5. [CoIII(μ-OH)CaII]+ was also synthesized from the oxidation of [CoIIMST]− with PhIO in the presence of CaIIOTf2/15-crown-5. Allowing [CoIII(μ-OH)CaII]+ to react with diphenylhydrazine afforded [CoII(μ-OH2)CaIIOH2]+ and azobenzene. Additionally, the characterization of [CoIII(μ-OH)CaII]+ provides another formulation for the previously reported CoIV–oxo complex, [(TMG3tren)CoIV(μ-O)ScIII(OTf)3]2+ to one that instead could contain a CoIII–OH unit. PMID:22998407

Protonation of a peroxodiiron(III) complex and conversion to a diiron(III/IV) intermediate: implications for proton-assisted O-O bond cleavage in nonheme diiron enzymes.

PubMed

Cranswick, Matthew A; Meier, Katlyn K; Shan, Xiaopeng; Stubna, Audria; Kaizer, Jószef; Mehn, Mark P; Münck, Eckard; Que, Lawrence

2012-10-01

Oxygenation of a diiron(II) complex, [Fe(II)(2)(μ-OH)(2)(BnBQA)(2)(NCMe)(2)](2+) [2, where BnBQA is N-benzyl-N,N-bis(2-quinolinylmethyl)amine], results in the formation of a metastable peroxodiferric intermediate, 3. The treatment of 3 with strong acid affords its conjugate acid, 4, in which the (μ-oxo)(μ-1,2-peroxo)diiron(III) core of 3 is protonated at the oxo bridge. The core structures of 3 and 4 are characterized in detail by UV-vis, Mössbauer, resonance Raman, and X-ray absorption spectroscopies. Complex 4 is shorter-lived than 3 and decays to generate in ~20% yield of a diiron(III/IV) species 5, which can be identified by electron paramagnetic resonance and Mössbauer spectroscopies. This reaction sequence demonstrates for the first time that protonation of the oxo bridge of a (μ-oxo)(μ-1,2-peroxo)diiron(III) complex leads to cleavage of the peroxo O-O bond and formation of a high-valent diiron complex, thereby mimicking the steps involved in the formation of intermediate X in the activation cycle of ribonucleotide reductase.

Chitosan-bound pyridinedicarboxylate Ni(II) and Fe(III) complex biopolymer films as waste water decyanidation agents.

PubMed

Adewuyi, Sheriff; Jacob, Julianah Modupe; Olaleye, Oluwatoyin Omolola; Abdulraheem, Taofiq Olanrewaju; Tayo, Jubril Ayopo; Oladoyinbo, Fatai Oladipupo

2016-10-20

Chitosan is a biopolymer with immense structural advantage for chemical and mechanical modifications to generate novel properties, functions and applications. This work depicts new pyridinedicarboxylicacid (PDC) crosslinked chitosan-metal ion films as veritable material for cyanide ion removal from aqueous solution. The PDC-crosslinked chitosan-metal films (PDC-Chit-Ni(II) and PDC-Chit-Fe(III)) were formed by complexing PDC-crosslinked chitosan film with anhydrous nickel(II) and iron(III) chloride salts respectively. The PDC-Chit and its metal films were characterized employing various analytical and spectroscopic techniques. The FT-IR, UV-vis and the XRD results confirm the presence of the metal ions in the metal coordinated PDC-crosslinked chitosan film. The surface morphological difference of PDC-Chit-Ni(II) film before and after decyanidation was explored with scanning electron microscopy. Furthermore, the quantitative amount of nickel(II) and iron(III) present in the complex were determined using Atomic Absorption Spectrophotometer as 32.3 and 37.2μg/g respectively which portends the biopolymer film as a good complexing agent. Removal of cyanide from aqueous solution with PDC-Chit, PDC-Chit-Ni(II) and PDC-Chit-Fe(III) films was studied with batch equilibrium experiments. At equilibrium, decyanidation capacity (DC) followed the order PDC-Chit-Ni (II)≈PDC-Chit-Fe(III)>PDC-Chit. PDC-Chit-Ni(II) film gave 100% CN(-) removal within 40min decyanidation owing to favorable coordination geometry. Copyright © 2016 Elsevier Ltd. All rights reserved.

Regulation of the Tumor-Suppressor Function of the Class III Phosphatidylinositol 3-Kinase Complex by Ubiquitin and SUMO

PubMed Central

Reidick, Christina; El Magraoui, Fouzi; Meyer, Helmut E.; Stenmark, Harald; Platta, Harald W.

2014-01-01

The occurrence of cancer is often associated with a dysfunction in one of the three central membrane-involution processes—autophagy, endocytosis or cytokinesis. Interestingly, all three pathways are controlled by the same central signaling module: the class III phosphatidylinositol 3-kinase (PI3K-III) complex and its catalytic product, the phosphorylated lipid phosphatidylinositol 3-phosphate (PtdIns3P). The activity of the catalytic subunit of the PI3K-III complex, the lipid-kinase VPS34, requires the presence of the membrane-targeting factor VPS15 as well as the adaptor protein Beclin 1. Furthermore, a growing list of regulatory proteins associates with VPS34 via Beclin 1. These accessory factors define distinct subunit compositions and thereby guide the PI3K-III complex to its different cellular and physiological roles. Here we discuss the regulation of the PI3K-III complex components by ubiquitination and SUMOylation. Especially Beclin 1 has emerged as a highly regulated protein, which can be modified with Lys11-, Lys48- or Lys63-linked polyubiquitin chains catalyzed by distinct E3 ligases from the RING-, HECT-, RBR- or Cullin-type. We also point out other cross-links of these ligases with autophagy in order to discuss how these data might be merged into a general concept. PMID:25545884

Kinetics and thermodynamics of irreversible inhibition of matrix metalloproteinase 2 by a Co(III) Schiff base complex

PubMed Central

Harney, Allison S.; Sole, Laura B.

2012-01-01

Cobalt(III) Schiff base complexes have been used as potent inhibitors of protein function through the coordination to histidine residues essential for activity. The kinetics and thermodynamics of the binding mechanism of Co(acacen)(NH3)2Cl [Co(acacen); where H2acacen is bis(acetylacetone)ethylenediimine] enzyme inhibition has been examined through the inactivation of matrix metalloproteinase 2 (MMP-2) protease activity. Co(acacen) is an irreversible inhibitor that exhibits time- and concentration-dependent inactivation of MMP-2. Co(acacen) inhibition of MMP-2 is temperature-dependent, with the inactivation increasing with temperature. Examination of the formation of the transition state for the MMP-2/Co(acacen) complex was determined to have a positive entropy component indicative of greater disorder in the MMP-2/Co(acacen) complex than in the reactants. With further insight into the mechanism of Co(acacen) complexes, Co(III) Schiff base complex protein inactivators can be designed to include features regulating activity and protein specificity. This approach is widely applicable to protein targets that have been identified to have clinical significance, including matrix metalloproteinases. The mechanistic information elucidated here further emphasizes the versatility and utility of Co(III) Schiff base complexes as customizable protein inhibitors. PMID:22729838

Closed Genome Sequences of Seven Histophilus somni Isolates from Beef Calves with Bovine Respiratory Disease Complex.

PubMed

Harhay, Gregory P; Harhay, Dayna M; Bono, James L; Smith, Timothy P L; Capik, Sarah F; DeDonder, Keith D; Apley, Michael D; Lubbers, Brian V; White, Bradley J; Larson, Robert L

2017-10-05

Histophilus somni is a fastidious Gram-negative opportunistic pathogenic Pasteurellaceae that affects multiple organ systems and is one of the principal bacterial species contributing to bovine respiratory disease complex (BRDC) in feed yard cattle. Here, we present seven closed genome sequences isolated from three beef calves showing sign of BRDC.

Biotransformations of anticancer ruthenium(III) complexes: an X-ray absorption spectroscopic study.

PubMed

Levina, Aviva; Aitken, Jade B; Gwee, Yee Yen; Lim, Zhi Jun; Liu, Mimi; Singharay, Anannya Mitra; Wong, Pok Fai; Lay, Peter A

2013-03-11

An anti-metastatic drug, NAMI-A ((ImH)[Ru(III) Cl4 (Im)(dmso)]; Im=imidazole, dmso=S-bound dimethylsulfoxide), and a cytotoxic drug, KP1019 ((IndH)[Ru(III) Cl4 (Ind)2 ]; Ind=indazole), are two Ru-based anticancer drugs in human clinical trials. Their reactivities under biologically relevant conditions, including aqueous buffers, protein solutions or gels (e.g, albumin, transferrin and collagen), undiluted blood serum, cell-culture medium and human liver (HepG2) cancer cells, were studied by Ru K-edge X-ray absorption spectroscopy (XAS). These XAS data were fitted from linear combinations of spectra of well-characterised Ru compounds. The absence of XAS data from the parent drugs in these fits points to profound changes in the coordination environments of Ru(III) . The fits point to the presence of Ru(IV/III) clusters and binding of Ru(III) to S-donor groups, amine/imine and carboxylato groups of proteins. Cellular uptake of KP1019 is approximately 20-fold higher than that of NAMI-A under the same conditions, but it diminishes drastically after the decomposition of KP1019 in cell-culture media, which indicate that the parent complex is taken in by cells through passive diffusion. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Colorimetric and Luminescent Dual-Modal Assay for Cu(II) Ion Detection Using an Iridium(III) Complex

PubMed Central

Ma, Dik-Lung; He, Hong-Zhang; Chan, Daniel Shiu-Hin; Wong, Chun-Yuen; Leung, Chung-Hang

2014-01-01

A novel iridium(III) complex-based chemosensor bearing the 5,6-bis(salicylideneimino)-1,10-phenanthroline ligand receptor was developed, which exhibited a highly sensitive and selective color change from colorless to yellow and a visible turn-off luminescence response upon the addition of Cu(II) ions. The interactions of this iridium(III) complex with Cu2+ ions and thirteen other cations have been investigated by UV-Vis absorption titration, emission titration, and 1H NMR titration. PMID:24927177

Gd(III) complexes as paramagnetic tags: Evaluation of the spin delocalization over the nuclei of the ligand

NASA Astrophysics Data System (ADS)

Collauto, A.; Feintuch, A.; Qi, M.; Godt, A.; Meade, T.; Goldfarb, D.

2016-02-01

Complexes of the Gd(III) ion are currently being established as spin labels for distance determination in biomolecules by pulse dipolar spectroscopy. Because Gd(III) is an f ion, one expects electron spin density to be localized on the Gd(III) ion - an important feature for the mentioned application. Most of the complex ligands have nitrogens as Gd(III) coordinating atoms. Therefore, measurement of the 14N hyperfine coupling gives access to information on the localization of the electron spin on the Gd(III) ion. We carried out W-band, 1D and 2D 14N and 1H ENDOR measurements on the Gd(III) complexes Gd-DOTA, Gd-538, Gd-595, and Gd-PyMTA that serve as spin labels for Gd-Gd distance measurements. The obtained 14N spectra are particularly well resolved, revealing both the hyperfine and nuclear quadrupole splittings, which were assigned using 2D Mims ENDOR experiments. Additionally, the spectral contributions of the two different types of nitrogen atoms of Gd-PyMTA, the aliphatic N atom and the pyridine N atom, were distinguishable. The 14N hyperfine interaction was found to have a very small isotropic hyperfine component of -0.25 to -0.37 MHz. Furthermore, the anisotropic hyperfine interactions with the 14N nuclei and with the non-exchangeable protons of the ligands are well described by the point-dipole approximation using distances derived from the crystal structures. We therefore conclude that the spin density is fully localized on the Gd(III) ion and that the spin density distribution over the nuclei of the ligands is rightfully ignored when analyzing distance measurements.

Respiratory and metabolic acidosis differentially affect the respiratory neuronal network in the ventral medulla of neonatal rats.

PubMed

Okada, Yasumasa; Masumiya, Haruko; Tamura, Yoshiyasu; Oku, Yoshitaka

2007-11-01

Two respiratory-related areas, the para-facial respiratory group/retrotrapezoid nucleus (pFRG/RTN) and the pre-Bötzinger complex/ventral respiratory group (preBötC/VRG), are thought to play key roles in respiratory rhythm. Because respiratory output patterns in response to respiratory and metabolic acidosis differ, we hypothesized that the responses of the medullary respiratory neuronal network to respiratory and metabolic acidosis are different. To test these hypotheses, we analysed respiratory-related activity in the pFRG/RTN and preBötC/VRG of the neonatal rat brainstem-spinal cord in vitro by optical imaging using a voltage-sensitive dye, and compared the effects of respiratory and metabolic acidosis on these two populations. We found that the spatiotemporal responses of respiratory-related regional activities to respiratory and metabolic acidosis are fundamentally different, although both acidosis similarly augmented respiratory output by increasing respiratory frequency. PreBötC/VRG activity, which is mainly inspiratory, was augmented by respiratory acidosis. Respiratory-modulated pixels increased in the preBötC/VRG area in response to respiratory acidosis. Metabolic acidosis shifted the respiratory phase in the pFRG/RTN; the pre-inspiratory dominant pattern shifted to inspiratory dominant. The responses of the pFRG/RTN activity to respiratory and metabolic acidosis are complex, and involve either augmentation or reduction in the size of respiratory-related areas. Furthermore, the activation pattern in the pFRG/RTN switched bi-directionally between pre-inspiratory/inspiratory and post-inspiratory. Electrophysiological study supported the results of our optical imaging study. We conclude that respiratory and metabolic acidosis differentially affect activities of the pFRG/RTN and preBötC/VRG, inducing switching and shifts of the respiratory phase. We suggest that they differently influence the coupling states between the pFRG/RTN and preBötC/VRG.

Solubility and transport of Cr(III) in a historically contaminated soil - Evidence of a rapidly reacting dimeric Cr(III) organic matter complex.

PubMed

Löv, Åsa; Sjöstedt, Carin; Larsbo, Mats; Persson, Ingmar; Gustafsson, Jon Petter; Cornelis, Geert; Kleja, Dan B

2017-12-01

Chromium is a common soil contaminant and, although it has been studied widely, questions about its speciation and dissolutions kinetics remain unanswered. We combined information from an irrigation experiment performed with intact soil columns with data from batch experiments to evaluate solubility and mobilization mechanisms of Cr(III) in a historically contaminated soil (>65 years). Particulate and colloidal Cr(III) forms dominated transport in this soil, but their concentrations were independent of irrigation intensity (2-20 mm h -1 ). Extended X-ray absorption fine structure (EXAFS) measurements indicated that Cr(III) associated with colloids and particles, and with the solid phase, mainly existed as dimeric hydrolyzed Cr(III) bound to natural organic matter. Dissolution kinetics of this species were fast (≤1 day) at low pH (<3) and slightly slower (≤5 days) at neutral pH. Furthermore, it proved possible to describe the solubility of the dimeric Cr(III) organic matter complex with a geochemical equilibrium model using only generic binding parameters, opening the way for use of geochemical models in risk assessments of Cr(III)-contaminated sites. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Three series of heterometallic NiII-LnIII Schiff base complexes: synthesis, crystal structures and magnetic characterization.

PubMed

Jiang, Lin; Liu, Yue; Liu, Xin; Tian, Jinlei; Yan, Shiping

2017-09-26

Three series of Ni II -Ln III complexes were synthesized with the general formulae [(μ 3 -CO 3 ) 2 {Ni(HL)(CH 3 -CH 2 OH)Ln(CH 3 COO)} 2 ]·2CH 3 CH 2 OH (1-6) (Ln = Tb (1), Dy (2), Ho (3), Er (4), Tm (5), Yb (6); H 3 L = N,N'-bis(3-methoxysalicylidene)-1,3-diamino-2-prop-anol), [Ni(HL)Ln(dbm) 3 ]·CH 3 OH 2 ·2CH 2 Cl 2 (7-10) (Ln = Tb (7), Eu (8), Gd (9), Ho (10); Hdbm = 1,3-diphenyl-1,3-propanedione) and [Ni(HL)(H 2 O)(tfa)Ln(hfac) 2 ] (11-15) (Ln = Tb (11), Dy (12), Eu (13), Gd (14), Ho (15); Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione, tfa - = trifluoroacetate) using compartmental Schiff base ligands in conjunction with auxiliary ligands. For the NiLn series, the tetranuclear structure could be considered as two Ni II -Ln III dinuclear subunits bridged by two carbonates derived from atmospheric carbon dioxide. The Ln III ions of complexes 1-6 were octa-coordinated with distorted triangular dodecahedral geometry, while the Ln III ions of the dinuclear complexes 7-15 were nona-coordinated with distorted muffin geometry. The magnetic properties of the three series complexes were studied using dc and ac magnetic measurements. For the Ni II -Gd III complexes, the dc magnetic susceptibility measurements suggested the existence of the anticipated ferromagnetic interaction between Ni II and Gd III ions. The fitting of the χ M T vs. T data processed by PHI software provided the parameters g = 2.08 (J = +0.87 cm -1 ) for 9 and g = 2.02 (J = +1.83 cm -1 ) for 14. The interaction exchange was magneto-structurally correlated to the Ni-O-Gd angle (α) and Ni(μ-O)Gd dihedral angle (β). With an applied dc field, complexes 1 (Tb), 2 (Dy), 7 (Tb) and 12 (Dy) exhibited single magnetic relaxation with SMM parameters of U eff /k = 13.60 K, 11.52 K, 7.69 K and 5.14 K, respectively. Analysis of the Cole-Cole plots for complexes 2 and 7 suggested that a single relaxation process was mainly involved in the relaxation process, with α values in the range of 0.37-0.17 and 0

Closed Genome Sequences of Seven Histophilus somni Isolates from Beef Calves with Bovine Respiratory Disease Complex

PubMed Central

Harhay, Dayna M.; Bono, James L.; Smith, Timothy P. L.; Capik, Sarah F.; DeDonder, Keith D.; Apley, Michael D.; Lubbers, Brian V.; White, Bradley J.; Larson, Robert L.

2017-01-01

ABSTRACT Histophilus somni is a fastidious Gram-negative opportunistic pathogenic Pasteurellaceae that affects multiple organ systems and is one of the principal bacterial species contributing to bovine respiratory disease complex (BRDC) in feed yard cattle. Here, we present seven closed genome sequences isolated from three beef calves showing sign of BRDC. PMID:28983006

Investigation of iron(III) complex with crown-porphyrin

NASA Astrophysics Data System (ADS)

Pankratov, Denis A.; Dolzhenko, Vladimir D.; Stukan, Reonald A.; Al Ansari, Yana F.; Savinkina, Elena V.; Kiselev, Yury M.

2013-08-01

Iron complex of 5-(4-(((4'-hydroxy-benzo-15-crown-5)-5'-yl)diazo)phenyl)-10,15,20-triphenylporphyrin was investigated by 57Fe Mössbauer spectroscopy and EPR. Two Fe sites were identified; they give two differing signals, doublet and wide absorption in a large velocity interval. EPR spectra of solutions of the complex in chloroform at room temperature also show two signals with g = 2.064, AFe = 0.032 cm - 1; g = 2.015, AFe = 0.0034 cm - 1. The doublet asymmetry is studied vs. temperature and normal angle to the sample plane and gamma-beam. The isomer shift δ in the doublet varies from 0.25 to 0.41 mm/s in the 360-5 K temperature range, whereas quadruple splitting value is constant, Δ ˜ 0.65 mm/s. The relax absorption may be described as a wide singlet ( δ = 0.30- 0.44 mm/s and Γ = 2.83-3.38 mm/s); its relative area strongly depends on temperature. According to δ, both signals are assigned to Fe(III).

Crystal structure and solution species of Ce(III) and Ce(IV) formates: from mononuclear to hexanuclear complexes.

PubMed

Hennig, Christoph; Ikeda-Ohno, Atsushi; Kraus, Werner; Weiss, Stephan; Pattison, Philip; Emerich, Hermann; Abdala, Paula M; Scheinost, Andreas C

2013-10-21

Cerium(III) and cerium(IV) both form formate complexes. However, their species in aqueous solution and the solid-state structures are surprisingly different. The species in aqueous solutions were investigated with Ce K-edge EXAFS spectroscopy. Ce(III) formate shows only mononuclear complexes, which is in agreement with the predicted mononuclear species of Ce(HCOO)(2+) and Ce(HCOO)2(+). In contrast, Ce(IV) formate forms in aqueous solution a stable hexanuclear complex of [Ce6(μ3-O)4(μ3-OH)4(HCOO)x(NO3)y](12-x-y). The structural differences reflect the different influence of hydrolysis, which is weak for Ce(III) and strong for Ce(IV). Hydrolysis of Ce(IV) ions causes initial polymerization while complexation through HCOO(-) results in 12 chelate rings stabilizing the hexanuclear Ce(IV) complex. Crystals were grown from the above-mentioned solutions. Two crystal structures of Ce(IV) formate were determined. Both form a hexanuclear complex with a [Ce6(μ3-O)4(μ3-OH)4](12+) core in aqueous HNO3/HCOOH solution. The pH titration with NaOH resulted in a structure with the composition [Ce6(μ3-O)4(μ3-OH)4(HCOO)10(NO3)2(H2O)3]·(H2O)9.5, while the pH adjustment with NH3 resulted in [Ce6(μ3-O)4(μ3-OH)4(HCOO)10(NO3)4]·(NO3)3(NH4)5(H2O)5. Furthermore, the crystal structure of Ce(III) formate, Ce(HCOO)3, was determined. The coordination polyhedron is a tricapped trigonal prism which is formed exclusively by nine HCOO(-) ligands. The hexanuclear Ce(IV) formate species from aqueous solution is widely preserved in the crystal structure, whereas the mononuclear solution species of Ce(III) formate undergoes a polymerization during the crystallization process.

Carbonato-bridged Ni(II)2Ln(III)2 (Ln(III) = Gd(III), Tb(III), Dy(III)) complexes generated by atmospheric CO2 fixation and their single-molecule-magnet behavior: [(μ4-CO3)2{Ni(II)(3-MeOsaltn)(MeOH or H2O)Ln(III)(NO3)}2]·solvent [3-MeOsaltn = N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato].

PubMed

Sakamoto, Soichiro; Fujinami, Takeshi; Nishi, Koshiro; Matsumoto, Naohide; Mochida, Naotaka; Ishida, Takayuki; Sunatsuki, Yukinari; Re, Nazzareno

2013-06-17

Atmospheric CO2 fixation of [Ni(II)(3-MeOsaltn)(H2O)2]·2.5H2O [3-MeOsaltn = N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato], Ln(III)(NO3)3·6H2O, and triethylamine occurred in methanol/acetone, giving a first series of carbonato-bridged Ni(II)2Ln(III)2 complexes [(μ4-CO3)2{Ni(II)(3-MeOsaltn)(MeOH)Ln(III)(NO3)}2] (1Gd, 1Tb, and 1Dy). When the reaction was carried out in acetonitrile/water, it gave a second series of complexes [(μ4-CO3)2{Ni(II)(3-MeOsaltn)(H2O)Ln(III)(NO3)}2]·2CH3CN·2H2O (2Gd, 2Tb, and 2Dy). For both series, each Ni(II)2Ln(III)2 structure can be described as two di-μ-phenoxo-bridged Ni(II)Ln(III) binuclear units bridged by two carbonato CO3(2-) units to form a carbonato-bridged (μ4-CO3)2{Ni(II)2Ln(III)2} structure. The high-spin Ni(II) ion has octahedral coordination geometry, and the Ln(III) ion is coordinated by O9 donor atoms from Ni(II)(3-MeOsaltn), bidentate NO3(-), and one and two oxygen atoms of two CO3(2-) ions. The NO3(-) ion for the first series roughly lie on Ln-O(methoxy) bonds and are tilted toward the outside, while for the second series, the two oxygen atoms roughly lie on one of the Ln-O(phenoxy) bonds due to the intramolecular hydrogen bond. The temperature-dependent magnetic susceptibilities indicated a ferromagnetic interaction between the Ni(II) and Ln(III) ions (Ln(III) = Gd(III), Tb(III), Dy(III)) for all of the complexes, with a distinctly different magnetic behavior between the two series in the lowest-temperature region due to the Ln(III)-Ln(III) magnetic interaction and/or different magnetic anisotropies of the Tb(III) or Dy(III) ion. Alternating-current susceptibility measurements under the 0 and 1000 Oe direct-current (dc) bias fields showed no magnetic relaxation for the Ni(II)2Gd(III)2 complexes but exhibited an out-of-phase signal for Ni(II)2Tb(III)2 and Ni(II)2Dy(III)2, indicative of slow relaxation of magnetization. The energy barriers, Δ/kB, for the spin flipping were estimated from the Arrhenius

Structural comparative studies on new MnII, CrIII and RuIII complexes derived from 2,4,6-tri-(2-pyridyl)-1,3,5-triazine (TPTZ)

NASA Astrophysics Data System (ADS)

Al-Assy, Waleed H.; El-Askalany, Abdel Moneum H.; Mostafa, Mohsen M.

2013-12-01

The structure of a new MnII complex, [Mn(TPTZ)Cl2(H2O)]ṡH2O, was established by a single crystal X-ray diffraction. Crystal data are as follow: monoclinic, P21/c, a = 8.7202 (3) Å, b = 11.5712 (4) Å, c = 20.8675 (9) Å, β = 11 (18) × 1010, V = 2029.27 (13) Å3, Z = 4. The HOMO, LUMO and other DFT parameters on the atoms have been calculated to confirm the geometry of the ligand and its complexes using material studio program. The complexes were characterized by elemental analyses, spectral, magnetic, thermal and cyclic voltammetry measurements. Electronic spectra and magnetic moments of the complexes suggest distorted-octahedral structures around the metal ions (MnII, CrIII and RuIII). The redox properties were investigated by cyclic voltammetry. Kinetic parameters were determined using Coats-Redfern and Horowitz-Metzger methods. The results of DNA studies of the metal complexes promised to be effective in tumour treatment.

Redox reactions of V(III) and Cr(III)picolinate complexes in aqueous solutions

NASA Astrophysics Data System (ADS)

Vinayakumar, C. K.; Dey, G. R.; Kishore, K.; Moorthy, P. N.

1996-12-01

Reactions of e aq-, H-atoms, OH, (CH 3) 2COH, and CO 2- radicals with V(III)picolinate and Cr(III)picolinate have been studied by the pulse radiolysis technique. The spectra of V(II)picolinate, V(IV)picolinate, Cr(II)picolinate, OH adduct of Cr(III)picolinate and Cr(IV)picolinate have been obtained and the rate constants of the reactions of various radicals with V(III) and Cr(III)picolinate have been determined. The implications of these results to the chemical decontamination of nuclear reactor systems are discussed.

Design and synthesis of novel adenine fluorescence probe based on Eu(III) complexes with dtpa-bis(guanine) ligand

NASA Astrophysics Data System (ADS)

Tian, Fengyun; Jiang, Xiaoqing; Dou, Xuekai; Wu, Qiong; Wang, Jun; Song, Youtao

2017-05-01

A novel adenine (Ad) fluorescence probe (EuIII-dtpa-bis(guanine)) was designed and synthesized by improving experimental method based on the Eu(III) complex and dtpa-bis(guanine) ligand. The dtpa-bis(guanine) ligand was first synthesized by the acylation action between dtpaa and guanine (Gu), and the corresponding Eu(III) complex was successfully prepared through heat-refluxing method with dtpa-bis(guanine) ligand. As a novel fluorescence probe, the EuIII-dtpa-bis(guanine) complex can detect adenine (Ad) with characteristics of strong targeting, high specificity and high recognition ability. The detection mechanism of the adenine (Ad) using this probe in buffer solution was studied by ultraviolet-visible (UV-vis) and fluorescence spectroscopy. When the EuIII-dtpa-bis(guanine) was introduced to the adenine (Ad) solution, the fluorescence emission intensity was significantly enhanced. However, adding other bases such as guanine (Gu), xanthine (Xa), hypoxanthine (Hy) and uric acid (Ur) with similar composition and structure to that of adenine (Ad) to the EuIII-dtpa-bis(guanine) solution, the fluorescence emission intensities are nearly invariable. Meanwhile, the interference of guanine (Gu), xanthine (Xa), hypoxanthine (Hy) and uric acid (Ur) on the detection of the adenine using EuIII-dtpa-bis(guanine) probe was also studied. It was found that presence of these bases does not affect the detection of adenine (Ad). A linear response of fluorescence emission intensities of EuIII-dtpa-bis(guanine) at 570 nm as a function of adenine (Ad) concentration in the range of 0.00-5.00 × 10- 5 mol L- 1 was observed. The detection limit is about 4.70 × 10- 7 mol L- 1.

miR-504 mediated down-regulation of nuclear respiratory factor 1 leads to radio-resistance in nasopharyngeal carcinoma

PubMed Central

Zhao, Luqing; Tang, Min; Hu, Zheyu; Yan, Bin; Pi, Weiwei; Li, Zhi; Zhang, Jing; Zhang, Liqin; Jiang, Wuzhong; Li, Guo; Qiu, Yuanzheng; Hu, Fang; Liu, Feng; Lu, Jingchen; Chen, Xue; Xiao, Lanbo; Xu, Zhijie; Tao, Yongguang; Yang, Lifang; Bode, Ann M.; Dong, Zigang; Zhou, Jian; Fan, Jia; Sun, Lunquan; Cao, Ya

2015-01-01

microRNAs (miRNAs) are involved in the various processes of DNA damage repair and play crucial roles in regulating response of tumors to radiation therapy. Here, we used nasopharyngeal carcinoma (NPC) radio-resistant cell lines as models and found that the expression of miR-504 was significantly up-regulated. In contrast, the expression of nuclear respiratory factor 1 (NRF1) and other mitochondrial metabolism factors, including mitochondrial transcription factor A (TFAM) and oxidative phosphorylation (OXPHOS) complex III were down-regulated in these cell lines. At the same time, the Seahorse cell mitochondrial stress test results indicated that the mitochondrial respiratory capacity was impaired in NPC radio-resistant cell lines and in a miR-504 over-expressing cell line. We also conducted dual luciferase reporter assays and verified that miR-504 could directly target NRF1. Additionally, miR-504 could down-regulate the expression of TFAM and OXPHOS complexes I, III, and IV and impaired the mitochondrial respiratory function of NPC cells. Furthermore, serum from NPC patients showed that miR-504 was up-regulated during different weeks of radiotherapy and correlated with tumor, lymph nodes and metastasis (TNM) stages and total tumor volume. The radio-therapeutic effect at three months after radiotherapy was evaluated. Results indicated that patients with high expression of miR-504 exhibited a relatively lower therapeutic effect ratio of complete response (CR), but a higher ratio of partial response (PR), compared to patients with low expression of miR-504. Taken together, these results demonstrated that miR-504 affected the radio-resistance of NPC by down-regulating the expression of NRF1 and disturbing mitochondrial respiratory function. Thus, miR-504 might become a promising biomarker of NPC radio-resistance and targeting miR-504 might improve tumor radiation response. PMID:26201446

Synthesis, spectroscopic, photoluminescence properties and biological evaluation of novel Zn(II) and Al(III) complexes of NOON tetradentate Schiff bases

NASA Astrophysics Data System (ADS)

Abdel Aziz, Ayman A.; Badr, Ibrahim H. A.; El-Sayed, Ibrahim S. A.

2012-11-01

Novel mononuclear Zn(II) and Al(III) complexes were synthesized from the reactions of Zn(OAc)2·2H2O and anhydrous AlCl3 with neutral N2O2 donor tetradentate Schiff bases; N,N'bis(salicylaldehyde)4,5-dimethyl-1,2-phenylenediamine (H2L1) and N,N'bis(salicylaldehyde)4,5-dichloro-1,2-phenylenediamine (H2L2). The new complexes were fully characterized by using micro analyses (CHN), FT-IR, 1H NMR, UV-Vis spectra and thermal analysis. The analytical data have been showed that, the stoichiometry of the complexes is 1:1. Spectroscopic data suggested tetrahedral and square pyramidal geometries for Zn(II) and Al(III) complexes, respectively. The synthesized Zn(II), and Al(III) complexes exhibited intense fluorescence emission in the visible region upon UV-excitation in methylene chloride solution at ambient temperature. This high fluorescence emission was assigned to the strong coordination of the ligands to the small and the highly charged Zn(II) and Al(III) ions. Such strong coordination seems to extend the π-conjugation of the complexes. Thermal analysis measurements indicated that the complexes have good thermal stability. As a potential application the biological activity (e.g., antimicrobial action) of the prepared ligands and complexes was assessed by in-vitro testing of their effect on the growth of various strains of bacteria and fungi.

Cytotoxic property of surfactant-cobalt(III) complexes on a human breast cancer cell line.

PubMed

Kumar, Rajendran Senthil; Riyasdeen, Anvarbatcha; Dinesh, Mohanakrishnan; Paul, Christo Preethy; Srinag, Suresh; Krishnamurthy, Hanumanthappa; Arunachalam, Sankaralingam; Akbarsha, Mohammad Abdulkadher

2011-07-01

The cancer chemotherapeutic potential of surfactant-cobalt(III) complexes, cis-[Co(bpy)(2)(C(14)H(29)NH(2))Cl](ClO(4))(2)·3 H(2)O (1) and cis-[Co(phen)(2)(C(14)H(29)NH(2))Cl](ClO(4))(2)·3 H(2)O (2) (bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline) on MCF-7 breast cancer cell was determined adopting MTT assay and specific staining techniques. The complexes affected the viability of the cells significantly and the cells succumbed to apoptosis as seen in the changes in the nuclear morphology and cytoplasmic features. Since the complex 2 appeared to be more potent, further assays were carried out on the complex 2. Single-cell electrophoresis indicated DNA damage. The translocation of phosphatidyl serine and loss of mitochondrial potential was revealed by annexin V-Cy3 staining and JC-1 staining respectively. Western blot analysis revealed up-regulation of pro-apoptotic p53 and down-regulation of anti-apoptotic Bcl-2 protein. Taken together, the surfactant-cobalt(III) complex 2 would be a potential candidate for further investigation for application as a chemotherapeutic for cancers in general and estrogen receptor-positive breast cancer in particular. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Automated RNA amplification for the rapid identification of Mycobacterium tuberculosis complex in respiratory specimens].

PubMed

Drouillon, V; Houriez, F; Buze, M; Lagrange, P; Herrmann, J-L

2006-01-01

Rapid and sensitive detection of Mycobacterium tuberculosis complex (MTB) directly on clinical respiratory specimens is essential for a correct management of patients suspected of tuberculosis. For this purpose PCR-based kits are available to detect MTB in respiratory specimen but most of them need at least 4 hours to be completed. New methods, based on TRC method (TRC: Transcription Reverse transcription Concerted--TRCRapid M. Tuberculosis--Tosoh Bioscience, Tokyo, Japon) and dedicated monitor have been developed. A new kit (TRC Rapid M. tuberculosis and Real-time monitor TRCRapid-160, Tosoh Corporation, Japan) enabling one step amplification and real-time detection of MTB 16S rRNA by a combination of intercalative dye oxazole yellow-linked DNA probe and isothermal RNA amplification directly on respiratory specimens has been tested in our laboratory. 319 respiratory specimens were tested in this preliminary study and results were compared to smear and culture. Fourteen had a positive culture for MTB. Among theses samples, smear was positive in 11 cases (78.6%) and TRC process was positive in 8 cases (57.1%). Overall sensitivity of TRC compared to smear positive samples is 73%. Theses first results demonstrated that a rapid identification of MTB was possible (less than 2 processing hours for 14 specimens and about 1 hour for 1 specimen) in most cases of smear positive samples using ready to use reagents for real time detection of MTB rRNA in clinical samples. New pretreatment and extraction reagents kits to increase the stability of the sputum RNA and the extraction efficiency are now tested in our laboratory.

The ins and outs of breath holding: simple demonstrations of complex respiratory physiology.

PubMed

Skow, Rachel J; Day, Trevor A; Fuller, Jonathan E; Bruce, Christina D; Steinback, Craig D

2015-09-01

The physiology of breath holding is complex, and voluntary breath-hold duration is affected by many factors, including practice, psychology, respiratory chemoreflexes, and lung stretch. In this activity, we outline a number of simple laboratory activities or classroom demonstrations that illustrate the complexity of the integrative physiology behind breath-hold duration. These activities require minimal equipment and are easily adapted to small-group demonstrations or a larger-group inquiry format where students can design a protocol and collect and analyze data from their classmates. Specifically, breath-hold duration is measured during a number of maneuvers, including after end expiration, end inspiration, voluntary prior hyperventilation, and inspired hyperoxia. Further activities illustrate the potential contribution of chemoreflexes through rebreathing and repeated rebreathing after a maximum breath hold. The outcome measures resulting from each intervention are easily visualized and plotted and can comprise a comprehensive data set to illustrate and discuss complex and integrated cardiorespiratory physiology. Copyright © 2015 The American Physiological Society.

Surfactant-cobalt(III) complexes: The impact of hydrophobicity on interaction with HSA and DNA - insights from experimental and theoretical approach.

PubMed

Veeralakshmi, Selvakumar; Sabapathi, Gopal; Nehru, Selvan; Venuvanalingam, Ponnambalam; Arunachalam, Sankaralingam

2017-05-01

To develop surfactant-based metallodrugs, it is very important to know about their hydrophobicity, micelle forming capacity, their interaction with biomacromolecules such as proteins and nucleic acids, and biological activities. Here, diethylenetriamine (dien) and tetradecylamine ligand (TA) based surfactant-cobalt(III) complexes with single chain domain, [Co(dien)(TA)Cl 2 ]ClO 4 (1) and double chain domain [Co(dien)(TA) 2 Cl](ClO 4 ) 2 (2) were chosen to study the effect of hydrophobicity on the interaction with human serum albumin and calf thymus DNA. The obtained results showed that (i) single chain surfactant-cobalt(III) complex (1) interact with HSA and DNA via electrostatic interaction and groove binding, respectively; (ii) double chain surfactant-cobalt(III) complex (2) interact with HSA and DNA via hydrophobic interaction and partial intercalation, respectively, due to the play of hydrophobicity by single and double chain domains. Further it is noted that, double chain surfactant-cobalt(III) complex interact strongly with HSA and DNA, compared single chain surfactant-cobalt(III) complex due to their more hydrophobicity nature. DFT and molecular docking studies offer insights into the mechanism and mode of binding towards the molecular target CT-DNA and HSA. Hence, the present findings will create new avenue towards the use of hydrophobic metallodrugs for various therapeutic applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Luminescent Rhenium(I) and Iridium(III) Polypyridine Complexes as Biological Probes, Imaging Reagents, and Photocytotoxic Agents.

PubMed

Lo, Kenneth Kam-Wing

2015-12-15

Although the interactions of transition metal complexes with biological molecules have been extensively studied, the use of luminescent transition metal complexes as intracellular sensors and bioimaging reagents has not been a focus of research until recently. The main advantages of luminescent transition metal complexes are their high photostability, long-lived phosphorescence that allows time-resolved detection, and large Stokes shifts that can minimize the possible self-quenching effect. Also, by the use of transition metal complexes, the degree of cellular uptake can be readily determined using inductively coupled plasma mass spectrometry. For more than a decade, we have been interested in the development of luminescent transition metal complexes as covalent labels and noncovalent probes for biological molecules. We argue that many transition metal polypyridine complexes display triplet charge transfer ((3)CT) emission that is highly sensitive to the local environment of the complexes. Hence, the biological labeling and binding interactions can be readily reflected by changes in the photophysical properties of the complexes. In this laboratory, we have modified luminescent tricarbonylrhenium(I) and bis-cyclometalated iridium(III) polypyridine complexes of general formula [Re(bpy-R(1))(CO)3(py-R(2))](+) and [Ir(ppy-R(3))2(bpy-R(4))](+), respectively, with reactive functional groups and used them to label the amine and sulfhydryl groups of biomolecules such as oligonucleotides, amino acids, peptides, and proteins. Additionally, using a range of biological substrates such as biotin, estradiol, and indole, we have designed luminescent rhenium(I) and iridium(III) polypyridine complexes as noncovalent probes for biological receptors. The interesting results generated from these studies have prompted us to investigate the possible applications of luminescent transition metal complexes in intracellular systems. Thus, in the past few years, we have developed an interest

The aerobic respiratory chain of the acidophilic archaeon Ferroplasma acidiphilum: A membrane-bound complex oxidizing ferrous iron.

PubMed

Castelle, Cindy J; Roger, Magali; Bauzan, Marielle; Brugna, Myriam; Lignon, Sabrina; Nimtz, Manfred; Golyshina, Olga V; Giudici-Orticoni, Marie-Thérèse; Guiral, Marianne

2015-08-01

The extremely acidophilic archaeon Ferroplasma acidiphilum is found in iron-rich biomining environments and is an important micro-organism in naturally occurring microbial communities in acid mine drainage. F. acidiphilum is an iron oxidizer that belongs to the order Thermoplasmatales (Euryarchaeota), which harbors the most extremely acidophilic micro-organisms known so far. At present, little is known about the nature or the structural and functional organization of the proteins in F. acidiphilum that impact the iron biogeochemical cycle. We combine here biochemical and biophysical techniques such as enzyme purification, activity measurements, proteomics and spectroscopy to characterize the iron oxidation pathway(s) in F. acidiphilum. We isolated two respiratory membrane protein complexes: a 850 kDa complex containing an aa3-type cytochrome oxidase and a blue copper protein, which directly oxidizes ferrous iron and reduces molecular oxygen, and a 150 kDa cytochrome ba complex likely composed of a di-heme cytochrome and a Rieske protein. We tentatively propose that both of these complexes are involved in iron oxidation respiratory chains, functioning in the so-called uphill and downhill electron flow pathways, consistent with autotrophic life. The cytochrome ba complex could possibly play a role in regenerating reducing equivalents by a reverse ('uphill') electron flow. This study constitutes the first detailed biochemical investigation of the metalloproteins that are potentially directly involved in iron-mediated energy conservation in a member of the acidophilic archaea of the genus Ferroplasma. Copyright © 2015 Elsevier B.V. All rights reserved.

A comparative study on the binding of single and double chain surfactant-cobalt(III) complexes with bovine serum albumin

NASA Astrophysics Data System (ADS)

Vignesh, G.; Sugumar, K.; Arunachalam, S.; Vignesh, S.; Arthur James, R.

2013-09-01

The comparative binding effect of single and double aliphatic chain containing surfactant-cobalt(III) complexes cis-[Co(bpy)2(DA)2](ClO4)3ṡ2H2O (1), cis-[Co(bpy)2(DA)Cl](ClO4)2ṡ2H2O (2), cis-[Co(phen)2(CA)2](ClO4)3ṡ2H2O (3), and cis-[Co(phen)2(CA)Cl](ClO4)2ṡ2H2O (4) with bovine serum albumin (BSA) under physiological condition was analyzed by steady state, time resolved fluorescence, synchronous, three-dimensional fluorescence, UV-Visible absorption and circular dichroism spectroscopic techniques. The results show that these complexes cause the fluorescence quenching of BSA through a static mechanism. The binding constants (Kb) and the number of binding sites were calculated and binding constant values are found in the range of 104-105 M-1. The results indicate that compared to single chain complex, double chain surfactant-cobalt(III) complex interacts strongly with BSA. Also the sign of thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicate that all the complexes interact with BSA through hydrophobic force. The binding distance (r) between complexes and BSA was calculated using Förster non-radiation energy transfer theory and found to be less than 7 nm. The results of synchronous, three dimensional fluorescence and circular dichroism spectroscopic methods indicate that the double chain surfactant-cobalt(III) complexes changed the conformation of the protein considerably than the respective single chain surfactant-cobalt(III) complexes. Antimicrobial studies of the complexes showed good activities against pathogenic microorganisms.

Gold(III) bis-thiosemicarbazonato complexes: synthesis, characterization, radiochemistry and X-ray crystal structure analysis.

PubMed

Bottenus, Brienne N; Kan, Para; Jenkins, Tyler; Ballard, Beau; Rold, Tammy L; Barnes, Charles; Cutler, Cathy; Hoffman, Timothy J; Green, Mark A; Jurisson, Silvia S

2010-01-01

A variety of (bis)thiosemicarbazone-based ligand systems have been investigated as chelating agents for Au(III) complexes with potential radiotherapeutic applications. Ligand systems containing an ethyl, propyl or butyl backbone between the two imine N donors have been synthesized to evaluate chelate ring size effects on the resultant Au(III) complex stability at the macroscopic and radiotracer levels. The Au(III) complexes were synthesized and characterized by NMR, electrospray ionization mass spectra, elemental analysis and X-ray crystallography. The (198)Au complexes were evaluated in vitro at the tracer level for stability in phosphate-buffered saline at pH 7.4 and 37 degrees C. One of these complexes [(198)Au(3,4-HxTSE)] showed high in vitro stability and was further evaluated in vivo in normal mice. [Au(ATSM)]AuCl(4).2CH(3)OH, (ATSM=diacetyl-bis(N(4)-methylthiosemicarbazone)) H(14)C(8)N(6)O(2)S(2)Cl(4)Au(2).2CH(3)OH, crystallized from methanol in the monoclinic space group P21/n with a=14.7293(13) A, b=7.7432(7) A, c=20.4363(18) A, beta=100.140(2) degrees, V=2294.4 (4) A(3), Z=4; [Au(3,4-HxTSE)]Cl.CH(3)CH(2)OH/AuCl(2), (3,4-HxTSE=3,4-hexanedione-bis(N(4)-ethylthiosemicarbazone)) H(26)C(13.6)N(6)O(0.8)S(2)Cl(1.2)Au(1.2), crystallized from ethanol in the monoclinic space group P21/c with a=10.1990(10) A, b=13.8833(14) A, c=15.1752(15) A, beta=99.353(2) degrees , V=2120.2 (4) A(3), Z=4. These studies revealed poor stability of the [(198)Au][Au(3,4-HxTSE)](+) complex; however, crystal structure data suggest potential alterations to the ligand backbone may increase stability. Copyright 2010 Elsevier Inc. All rights reserved.

Cytotoxic and genotoxic potential of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA complex in human hepatoma (HepG2) cells.

PubMed

Novotnik, Breda; Ščančar, Janez; Milačič, Radmila; Filipič, Metka; Žegura, Bojana

2016-07-01

Chromium (Cr) and ethylenediaminetetraacetate (EDTA) are common environmental pollutants and can be present in high concentrations in surface waters at the same time. Therefore, chelation of Cr with EDTA can occur and thereby stable Cr(III)-EDTA complex is formed. Since there are no literature data on Cr(III)-EDTA toxicity, the aim of our work was to evaluate and compare Cr(III)-EDTA cytotoxic and genotoxic activity with those of Cr(VI) and Cr(III)-nitrate in human hepatoma (HepG2) cell line. First the effect of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA on cell viability was studied in the concentration range from 0.04 μg mL(-1) to 25 μg mL(-1) after 24 h exposure. Further the influence of non-cytotoxic concentrations of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA on DNA damage and genomic stability was determined with the comet assay and cytokinesis block micronucleus cytome assay, respectively. Cell viability was decreased only by Cr(VI) at concentrations above 1.0 μg mL(-1). Cr(VI) at ≥0.2 μg mL(-1) and Cr(III) at ≥1.0 μg mL(-1) induced DNA damage, while after Cr(III)-EDTA exposure no formation DNA strand breaks was determined. Statistically significant formation of micronuclei was induced only by Cr(VI) at ≥0.2 μg mL(-1), while no influence on the frequency of nuclear buds nor nucleoplasmic bridges was observed at any exposure. This study provides the first evidence that Cr(III)-EDTA did not induce DNA damage and had no influence on the genomic stability of HepG2 cells. Copyright © 2016 Elsevier Ltd. All rights reserved.

Uranium(iii) complexes supported by hydrobis(mercaptoimidazolyl)borates: synthesis and oxidation chemistry.

PubMed

Maria, Leonor; Santos, Isabel C; Santos, Isabel

2018-05-23

The reaction of [UI3(thf)4] with the sodium or lithium salts of hydrobis(2-mercapto-1-methylimidazolyl)borate ligands ([H(R)B(timMe)2]-) in a 1 : 2 ratio, in tetrahydrofuran, gave the U(iii) complexes [UI{κ3-H,S,S'-H(R)B(timMe)2}2(thf)2] (R = H (1), Ph (2)) in good yields. Crystals of [UI{κ3-H,S,S'-H(Ph)B(timMe)2}2(thf)2] (2) were obtained by recrystallization from a tetrahydrofuran/acetonitrile solution, and the ion-separated uranium complex [U{κ3-H,S,S'-H(Ph)B(timMe)2}2(CH3CN)3][I] (3-I) was obtained by dissolution of 2 in acetonitrile followed by recrystallization. One-electron oxidation of 2 with AgBPh4 or I2 resulted in the formation of the cationic U(iv) complexes [U{κ3-H,S,S'-H(Ph)B(timMe)2}3][X] (X = BPh4 (6-BPh4), I (6-I)), due to a ligand redistribution process. These complexes are the first examples of homoleptic poly(azolyl)borate U(iv) complexes. Treatment of complex 2 with azobenzene led to the isolation of crystals of the U(iv) compound [UI{κ3-H(Ph)B(timMe)2}2(κ2-timMe)] (7). Treatment of 2 with pyridine-N oxide (pyNO) led to the formation of the uranyl complex [UO2{κ2-S,S'-H(Ph)B(timMe)2}2] (8) and of complex 6-I, while from the reaction of [U{κ3-H(Ph)B(timMe)2}2(thf)3][BPh4] (5) with pyNO, the oxo-bridged U(iv) complex [{U{κ3-H(Ph)B(timMe)2}2(pyNO)}2(μ-O)][BPh4]2 (9) was also obtained. In the U(iii) and U(iv) complexes, the bis(azolyl)borate ligands bind to the uranium center in a κ3-H,S,S' coordination mode, while in the U(vi) complex the ligands bind to the metal in a κ2-S,S' mode. The presence of UH-B interactions in the solid-state, for the nine-coordinate complexes 1, 2, 3, 6 and 7 and for the eight-coordinate complex 9, was supported by IR spectroscopy and/or X-ray diffraction analysis.

Structure-activity relationships in cytotoxic Au(I)/Au(III) complexes derived from 2-(2'-pyridyl)benzimidazole.

PubMed

Maiore, Laura; Aragoni, Maria Carla; Deiana, Carlo; Cinellu, Maria Agostina; Isaia, Francesco; Lippolis, Vito; Pintus, Anna; Serratrice, Maria; Arca, Massimiliano

2014-04-21

Gold(I) and gold(III) complexes derived from 2-(2'-pyridyl)benzimidazole (pbiH) were proven to be a promising class of in vitro antitumor agents against A2780 human ovarian cancer cells. In this paper, a comparative electrochemical, UV-vis absorption, and emission spectroscopic investigation is reported on pbiH, the two mononuclear Au(III) complexes [(pbi)AuX2] (X = Cl (1), AcO (2)), the four mononuclear Au(I) derivatives [(pbiH)AuCl] (3), [(pbiH)Au(PPh3)]PF6 ((4(+))(PF6(-))), [(pbi)Au(PPh3)] (5), and [(pbi)Au(TPA)] (6), the three mixed-valence Au(III)/Au(I) complexes [(μ-pbi)Au2Cl3] (7), [(Ph3P)Au(μ-pbi)AuX2]PF6 (X = Cl ((8(+))(PF6(-))), AcO ((9(+))(PF6(-)))), and the binuclear Au(I)-Au(I) compound [(μ-pbi)Au2(PPh3)2]PF6 ((10(+))(PF6(-))). All complexes feature irreversible reduction processes related to the Au(III)/Au(I) or Au(I)/Au(0) processes and peculiar luminescent emission at about 360-370 nm in CH2Cl2, with quantum yields that are remarkably lower ((0.7-14.5) × 10(-2)) in comparison to that determined for the free pbiH ligand (31.5 × 10(-2)) in the same solvent. The spectroscopic and electrochemical properties of all complexes were interpreted on the grounds of time-dependent PBE0/DFT calculations carried out both in the gas phase and in CH2Cl2 implicitly considered within the IEF-PCM SCRF approach. The electronic structure of the complexes, and in particular the energy and composition of the Kohn-Sham LUMOs, can be related to the antiproliferative properties against the A2780 ovarian carcinoma cell line, providing sound quantitative structure-activity relationships and shedding a light on the role played by the global charge and nature of ancillary ligands in the effectiveness of Au-based antitumor drugs.

A Ni(iii) complex stabilized by silica nanoparticles as an efficient nanoheterogeneous catalyst for oxidative C-H fluoroalkylation.

PubMed

Khrizanforov, Mikhail N; Fedorenko, Svetlana V; Strekalova, Sofia O; Kholin, Kirill V; Mustafina, Asiya R; Zhilkin, Mikhail Ye; Khrizanforova, Vera V; Osin, Yuri N; Salnikov, Vadim V; Gryaznova, Tatyana V; Budnikova, Yulia H

2016-07-26

We have developed Ni(III)-doped silica nanoparticles ([(bpy)xNi(III)]@SiO2) as a recyclable, low-leaching, and efficient oxidative functionalization nanocatalyst for aromatic C-H bonds. The catalyst is obtained by doping the complex [(bpy)3Ni(II)] on silica nanoparticles along with its subsequent electrooxidation to [(bpy)xNi(III)] without an additional oxidant. The coupling reaction of arenes with perfluoroheptanoic acid occurs with 100% conversion of reactants in a single step at room temperature under nanoheterogeneous conditions. The catalyst content is only 1% with respect to the substrates under electrochemical regeneration conditions. The catalyst can be easily separated from the reaction mixture and reused a minimum of five times. The results emphasize immobilization on the silica support and the electrochemical regeneration of Ni(III) complexes as a facile route for developing an efficient nanocatalyst for oxidative functionalization.

Synthesis, spectroscopic, photoluminescence properties and biological evaluation of novel Zn(II) and Al(III) complexes of NOON tetradentate Schiff bases.

PubMed

Abdel Aziz, Ayman A; Badr, Ibrahim H A; El-Sayed, Ibrahim S A

2012-11-01

Novel mononuclear Zn(II) and Al(III) complexes were synthesized from the reactions of Zn(OAc)(2).2H(2)O and anhydrous AlCl(3) with neutral N2O2 donor tetradentate Schiff bases; N,N'bis(salicylaldehyde)4,5-dimethyl-1,2-phenylenediamine (H(2)L(1)) and N,N'bis(salicylaldehyde)4,5-dichloro-1,2-phenylenediamine (H(2)L(2)). The new complexes were fully characterized by using micro analyses (CHN), FT-IR, (1)H NMR, UV-Vis spectra and thermal analysis. The analytical data have been showed that, the stoichiometry of the complexes is 1:1. Spectroscopic data suggested tetrahedral and square pyramidal geometries for Zn(II) and Al(III) complexes, respectively. The synthesized Zn(II), and Al(III) complexes exhibited intense fluorescence emission in the visible region upon UV-excitation in methylene chloride solution at ambient temperature. This high fluorescence emission was assigned to the strong coordination of the ligands to the small and the highly charged Zn(II) and Al(III) ions. Such strong coordination seems to extend the π-conjugation of the complexes. Thermal analysis measurements indicated that the complexes have good thermal stability. As a potential application the biological activity (e.g., antimicrobial action) of the prepared ligands and complexes was assessed by in-vitro testing of their effect on the growth of various strains of bacteria and fungi. Copyright © 2012 Elsevier B.V. All rights reserved.

Biogenesis of the yeast cytochrome bc1 complex.

PubMed

Zara, Vincenzo; Conte, Laura; Trumpower, Bernard L

2009-01-01

The mitochondrial respiratory chain is composed of four different protein complexes that cooperate in electron transfer and proton pumping across the inner mitochondrial membrane. The cytochrome bc1 complex, or complex III, is a component of the mitochondrial respiratory chain. This review will focus on the biogenesis of the bc1 complex in the mitochondria of the yeast Saccharomyces cerevisiae. In wild type yeast mitochondrial membranes the major part of the cytochrome bc1 complex was found in association with one or two copies of the cytochrome c oxidase complex. The analysis of several yeast mutant strains in which single genes or pairs of genes encoding bc1 subunits had been deleted revealed the presence of a common set of bc1 sub-complexes. These sub-complexes are represented by the central core of the bc1 complex, consisting of cytochrome b bound to subunit 7 and subunit 8, by the two core proteins associated with each other, by the Rieske protein associated with subunit 9, and by those deriving from the unexpected interaction of each of the two core proteins with cytochrome c1. Furthermore, a higher molecular mass sub-complex is that composed of cytochrome b, cytochrome c1, core protein 1 and 2, subunit 6, subunit 7 and subunit 8. The identification and characterization of all these sub-complexes may help in defining the steps and the molecular events leading to bc1 assembly in yeast mitochondria.

Bowl adamanzanes--bicyclic tetraamines: syntheses and crystal structures of complexes with cobalt(III) and chelating coordinated oxo-anions.

PubMed

Broge, Louise; Søtofte, Inger; Jensen, Kristian; Jensen, Nicolai; Pretzmann, Ulla; Springborg, Johan

2007-09-14

Seven cobalt(III) complexes of the macrobicyclic tetraamine ligand [2(4).3(1)]adamanzane ([2(4).3(1)]adz) are reported along with the crystal structure of six of these complexes. The solid state and solution structures are discussed, and a detailed assignment of the NMR spectra of the sulfato complex is provided. Four of the seven complexes contain a chelate coordinating oxo-anion (sulfate, formiate, nitrate, carbonate). Equilibration of these species with the corresponding diaqua complex is generally slow. The rates of equilibration in 5 mol dm(-3) perchloric acid at 25 degrees C have been measured, yielding half lives of 20 min, 10 min and 3 h for the sulfato, formiato and carbonato species respectively. The corresponding reaction for the nitrato complex occurs with a half life of less than 3 min. The concentration acid dissociation constant for the Co([2(4).3(1)]adz)(HCO(3))(2+) ion has been measured to K(a) = 0.33 mol dm(-3) [25 degrees C, I = 2 mol dm(-3)] and K(a) = 0.15 mol dm(-3) [25 degrees C, I = 5 mol dm(-3)]. The propensity for coordination of sulfate was found to be large enough for a quantitative conversion of the carbonato complex to the sulfato complex to occur in 3 mol dm(-3) triflic acid containing a small sulfate contamination. On this basis the decarboxylation in 5 mol dm(-3) triflic acid of the corresponding cobalt(III) carbonato complex of the larger macrobicyclic tetraamine ligand [3(5)]adz was reinvestigated and found to lead to the sulfato complex as well. The difference in exchange rate of the oxo-anion ligands for the cobalt(III) complexes of the two adamanzane ligands is discussed and attributed to fundamental differences in the molecular structure where an inverted configuration of the secondary non-bridged amine groups is seen for the complexes of the larger [3(5)]adz ligand. The high affinity for chelating coordination of oxo-anions for these two cobalt(iii)-adamanzane-moieties is rationalised on basis of the N-Co-N angles. N

A chemiluminescence method to detect hydroquinone with water-soluble sulphonato-(salen)manganese(III) complex as catalyst.

PubMed

Zhang, Guangbin; Tang, Yuhai; Sun, Yang; Yu, Hua; Du, Wei; Fu, Qiang

2016-02-01

A water-soluble sulphonato-(salen)manganese(III) complex with excellent catalytic properties was synthesized and demonstrated to greatly enhance the chemiluminescence signal of the hydrogen peroxide - luminol reaction. Coupled with flow-injection technique, a simple and sensitive chemiluminescence method was first developed to detect hydroquinone based on the chemiluminescence system of the hydrogen peroxide-luminol-sulphonato-(salen)manganese(III) complex. Under optimal conditions, the assay exhibited a wide linear range from 0.1 to 10 ng mL(-1) with a detection limit of 0.05 ng mL(-1) for hydroquinone. The method was applied successfully to detect hydroquinone in tap-water and mineral-water, with a sampling frequency of 120 times per hour. The relative standard deviation for determination of hydroquinone was less than 5.6%, and the recoveries ranged from 96.8 to 103.0%. The ultraviolet spectra, chemiluminescence spectra, and the reaction kinetics for the peroxide-luminol-sulphonato-(salen)manganese(III) complex system were employed to study the possible chemiluminescence mechanism. The proposed chemiluminescence analysis technique is rapid and sensitive, with low cost, and could be easily extended and applied to other compounds. Copyright © 2015 John Wiley & Sons, Ltd.

Mono- and bis-tolyl­terpyridine iridium(III) complexes

PubMed Central

Hinkle, Lindsay M.; Young, Victor G.; Mann, Kent R.

2010-01-01

The first structure report of trichlorido[4′-(p-tolyl)-2,2′:6′,2′′-terpyridine]iridium(III) dimethyl sulfoxide solvate, [IrCl3(C22H17N3)]·C2H6OS, (I), is presented, along with a higher-symmetry setting of previously reported bis­[4′-(p-tolyl)-2,2′:6′,2′′-terpyridine]iridium(III) tris­(hexa­fluorido­phosphate) acetonitrile disolvate, [Ir(C22H17N3)2](PF6)3·2C2H3N, (II) [Yoshikawa, Yamabe, Kanehisa, Kai, Takashima & Tsukahara (2007 ▶). Eur. J. Inorg. Chem. pp. 1911–1919]. For (I), the data were collected with synchrotron radiation and the dimethyl sulfoxide solvent mol­ecule is disordered over three positions, one of which is an inversion center. The previously reported structure of (II) is presented in the more appropriate C2/c space group. The iridium complex and one PF6 − anion lie on twofold axes in this structure, making half of the mol­ecule unique. PMID:20203396

Genome Analysis of Structure–Function Relationships in Respiratory Complex I, an Ancient Bioenergetic Enzyme

PubMed Central

Degli Esposti, Mauro

2016-01-01

Respiratory complex I (NADH:ubiquinone oxidoreductase) is a ubiquitous bioenergetic enzyme formed by over 40 subunits in eukaryotes and a minimum of 11 subunits in bacteria. Recently, crystal structures have greatly advanced our knowledge of complex I but have not clarified the details of its reaction with ubiquinone (Q). This reaction is essential for bioenergy production and takes place in a large cavity embedded within a conserved module that is homologous to the catalytic core of Ni–Fe hydrogenases. However, how a hydrogenase core has evolved into the protonmotive Q reductase module of complex I has remained unclear. This work has exploited the abundant genomic information that is currently available to deduce structure–function relationships in complex I that indicate the evolutionary steps of Q reactivity and its adaptation to natural Q substrates. The results provide answers to fundamental questions regarding various aspects of complex I reaction with Q and help re-defining the old concept that this reaction may involve two Q or inhibitor sites. The re-definition leads to a simplified classification of the plethora of complex I inhibitors while throwing a new light on the evolution of the enzyme function. PMID:26615219

Structural Diversities in Heterometallic Mn-Ca Cluster Chemistry from the Use of Salicylhydroxamic Acid: {MnIII4Ca2}, {MnII/III6Ca2}, {MnIII/IV8Ca}, and {MnIII8Ca2} Complexes with Relevance to Both High- and Low-Valent States of the Oxygen-Evolving Complex.

PubMed

Alaimo, Alysha A; Koumousi, Evangelia S; Cunha-Silva, Luís; McCormick, Laura J; Teat, Simon J; Psycharis, Vassilis; Raptopoulou, Catherine P; Mukherjee, Shreya; Li, Chaoran; Gupta, Sayak Das; Escuer, Albert; Christou, George; Stamatatos, Theocharis C

2017-09-05

One-pot reactions between the [Mn 3 O(O 2 CPh) 6 (py) x ] +/0 triangular precursors and either CaBr 2 ·xH 2 O or CaCl 2 ·6H 2 O, in the presence of salicylhydroxamic acid (shaH 2 ), have afforded the heterometallic complexes [Mn III 4 Ca 2 (O 2 CPh) 4 (shi) 4 (H 2 O) 3 (Me 2 CO)] (1) and (pyH)[Mn II 2 Mn III 4 Ca 2 Cl 2 (O 2 CPh) 7 (shi) 4 (py) 4 ] (2), respectively, in good yields. Further reactions but using a more flexible synthetic scheme comprising the Mn(NO 3 ) 2 ·4H 2 O/Ca(NO 3 ) 2 ·4H 2 O and Mn(O 2 CPh) 2 ·2H 2 O/Ca(ClO 4 ) 2 ·4H 2 O "metal blends" and shaH 2 , in the presence of external base NEt 3 , led to the new complexes (NHEt 3 ) 2 [Mn III 4 Mn IV 4 Ca(OEt) 2 (shi) 10 (EtOH) 2 ] (3) and (NHEt 3 ) 4 [Mn III 8 Ca 2 (CO 3 ) 4 (shi) 8 ] (4), respectively. In all reported compounds, the anion of the tetradentate (N,O,O,O)-chelating/bridging ligand salicylhydroxime (shi 3- ), resulting from the in situ metal-ion-assisted amide-iminol tautomerism of shaH 2 , was found to bridge both Mn and Ca atoms. Complexes 1-4 exhibit a variety of different structures, metal stoichiometries, and Mn oxidation-state descriptions; 1 possesses an overall octahedral metal arrangement, 2 can be described as a Mn 4 Ca 2 octahedron bound to an additional Mn 2 unit, 3 consists of a Mn 8 "ring" surrounding a Ca II atom, and 4 adopts a rectangular cuboidal motif of eight Mn atoms accommodating two Ca II atoms. Solid-state direct-current magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the Mn centers, leading to S = 0 spin ground-state values for all complexes. From a bioinorganic chemistry perspective, the reported compounds may demonstrate some relevance to both high-valent scheme (3) and lower-oxidation-level species (1, 2, and 4) of the catalytic cycle of the oxygen-evolving complex.

Light-driven, proton-controlled, catalytic aerobic C-H oxidation mediated by a Mn(III) porphyrinoid complex.

PubMed

Neu, Heather M; Jung, Jieun; Baglia, Regina A; Siegler, Maxime A; Ohkubo, Kei; Fukuzumi, Shunichi; Goldberg, David P

2015-04-15

The visible light-driven, catalytic aerobic oxidation of benzylic C-H bonds was mediated by a Mn(III) corrolazine complex. To achieve catalytic turnovers, a strict selective requirement for the addition of protons was established. The resting state of the catalyst was unambiguously characterized by X-ray diffraction as [Mn(III)(H2O)(TBP8Cz(H))](+), in which a single, remote site on the ligand is protonated. If two remote sites are protonated, however, reactivity with O2 is shut down. Spectroscopic methods revealed that the related Mn(V)(O) complex is also protonated at the same remote site at -60 °C, but undergoes valence tautomerization upon warming.

Structural comparative studies on new Mn(II), Cr(III) and Ru(III) complexes derived from 2,4,6-tri-(2-pyridyl)-1,3,5-triazine (TPTZ).

PubMed

Al-Assy, Waleed H; El-Askalany, Abdel Moneum H; Mostafa, Mohsen M

2013-12-01

The structure of a new Mn(II) complex, [Mn(TPTZ)Cl2(H2O)]⋅H2O, was established by a single crystal X-ray diffraction. Crystal data are as follow: monoclinic, P21/c,a = 8.7202 (3)Å, b = 11.5712 (4)Å, c = 20.8675 (9)Å, β=11 (18) × 1010, V = 2029.27 (13)Å(3), Z = 4. The HOMO, LUMO and other DFT parameters on the atoms have been calculated to confirm the geometry of the ligand and its complexes using material studio program. The complexes were characterized by elemental analyses, spectral, magnetic, thermal and cyclic voltammetry measurements. Electronic spectra and magnetic moments of the complexes suggest distorted-octahedral structures around the metal ions (Mn(II), Cr(III) and Ru(III)). The redox properties were investigated by cyclic voltammetry. Kinetic parameters were determined using Coats-Redfern and Horowitz-Metzger methods. The results of DNA studies of the metal complexes promised to be effective in tumour treatment. Copyright © 2013 Elsevier B.V. All rights reserved.

Combined EXAFS Spectroscopic and Quantum Chemical Study on the Complex Formation of Am(III) with Formate.

PubMed

Fröhlich, Daniel R; Kremleva, Alena; Rossberg, André; Skerencak-Frech, Andrej; Koke, Carsten; Krüger, Sven; Rösch, Notker; Panak, Petra J

2017-06-19

The complexation of Am(III) with formate in aqueous solution is studied as a function of the pH value using a combination of extended X-ray absorption fine structure (EXAFS) spectroscopy, iterative transformation factor analysis (ITFA), and quantum chemical calculations. The Am L III -edge EXAFS spectra are analyzed to determine the molecular structure (coordination numbers; Am-O and Am-C distances) of the formed Am(III)-formate species and to track the shift of the Am(III) speciation with increasing pH. The experimental data are compared to predictions from density functional calculations. The results indicate that formate binds to Am(III) in a monodentate fashion, in agreement with crystal structures of lanthanide formates. Furthermore, the investigations are complemented by thermodynamic speciation calculations to verify further the results obtained.

Quantum electron tunneling in respiratory complex I.

PubMed

Hayashi, Tomoyuki; Stuchebrukhov, Alexei A

2011-05-12

We have simulated the atomistic details of electronic wiring of all Fe/S clusters in complex I, a key enzyme in the respiratory electron transport chain. The tunneling current theory of many-electron systems is applied to the broken-symmetry (BS) states of the protein at the ZINDO level. While the one-electron tunneling approximation is found to hold in electron tunneling between the antiferromagnetic binuclear and tetranuclear Fe/S clusters without major orbital or spin rearrangement of the core electrons, induced polarization of the core electrons contributes significantly to decrease the electron transfer rates to 19-56 %. Calculated tunneling energy is about 3 eV higher than Fermi level in the band gap of the protein, which supports that the mechanism of electron transfer is quantum mechanical tunneling, as in the rest of the electron transport chain. Resulting electron tunneling pathways consist of up to three key contributing protein residues between neighboring Fe/S clusters. A signature of the wave properties of electrons is observed as distinct quantum interferences when multiple tunneling pathways exist. In N6a-N6b, electron tunnels along different pathways depending on the involved BS states, suggesting possible fluctuations of the tunneling pathways driven by the local protein environment. The calculated distance dependence of the electron transfer rates with internal water molecules included is in good agreement with a reported phenomenological relation.

Transmetallation from CCC-NHC pincer Zr complexes in the synthesis of air-stable CCC-NHC pincer Co(iii) complexes and initial hydroboration trials.

PubMed

Reilly, Sean W; Webster, Charles Edwin; Hollis, T Keith; Valle, Henry U

2016-02-21

Development of CCC-NHC pincer Co complexes via transmetalation from Zr is reported. Formation of these air-stable Co(iii) complexes was achieved through use of a CoCl2 or Co(acac)3in situ or with a discrete CCC-NHC pincer Zr transmetallating agent. Preliminary activity in the hydroboration of styrene is reported. This facile methodology will further the development of CCC-NHC pincer first-row transition metal complexes.

CO Column Density and Extinction in the Chamaeleon II--III Dark-Cloud Complex

NASA Astrophysics Data System (ADS)

Hayakawa, Takahiro; Cambrésy, Laurent; Onishi, Toshikazu; Mizuno, Akira; Fukui, Yasuo

2001-12-01

We carried out 13CO (J = 1 -- 0) and C18O (J = 1 -- 0) observations of the Chamaeleon II--III dark-cloud complex with the NANTEN radio telescope. The column densities of both molecular isotopes were derived assuming LTE. The AV values were obtained by scaling the AV values that were derived using an adaptive-grid star-count method applied to the DENIS J-band data. We established the AV--CO isotope column-density relations in Cha II and III, and compared them with those in Cha I. The slopes of the AV--13CO relations for Cha II and III are steeper than that for Cha I. Those of the AV -- C18O relations are similar among the three clouds. The total column density ratio, N(13O) / N(C18O, in Cha I tends to be small compared with those in Cha II or Cha III; the ratios range from ~ 5 to ~ 25 at low extinction in Cha II and III, but at most ~ 10 in Cha I. We suggest that the increase of N(13CO) due to the 13CO formation process causes cloud-to-cloud variations in the AV -- N(13CO) correlation.

Mitochondrial respiratory chain enzyme assay and DNA analysis in peripheral blood leukocytes for the etiological study of Chinese children with Leigh syndrome due to complex I deficiency.

PubMed

Ma, Yan Yan; Wu, Tong Fei; Liu, Yu Peng; Wang, Qiao; Li, Xi Yuan; Zhang, Yao; Song, Jin Qing; Wang, Yu Jie; Yang, Yan Ling

2013-02-01

Mitochondrial respiratory chain complex I enzyme deficiency is the most commonly seen mitochondrial respiratory chain disorder. Although screening and diagnostic methods are available overseas, clinically feasible diagnostic methods have not yet been established in China. In this study, four Chinese boys with Leigh syndrome due to complex I deficiency were diagnosed by mitochondrial respiratory chain enzyme assay and DNA analysis using peripheral blood leukocytes. Four patients were admitted at the age of 5-14 years because of unexplained progressive neuromuscular symptoms, including motor developmental delay or regression, weakness, and seizures. Their cranial magnetic resonance imaging revealed typical finding as Leigh syndrome. Peripheral leukocyte mitochondrial respiratory chain complex I activities were found decreased to 9.6-33.1 nmol/min/mg mitochondrial protein(control 44.0 ± 5.4 nmol/min/mg). The ratios of complex I to citrate synthase activity were also decreased (8.9-19.8% in patients vs. control 48 ± 11%). Three mtDNA mutations were identified from three out of four patients, supporting the diagnosis of complex I deficiency. Point mutations m.10191T>C in mitochondrial ND3 gene, m.13513G>A in ND5 gene and m.14,453G>A in ND6 gene were detected in three patients.

Argentate(i) and (iii) complexes as intermediates in silver-mediated cross-coupling reactions.

PubMed

Weske, Sebastian; Hardin, Richard A; Auth, Thomas; O'Hair, Richard A J; Koszinowski, Konrad; Ogle, Craig A

2018-04-30

Despite the potential of silver to mediate synthetically valuable cross-coupling reactions, the operating mechanisms have remained unknown. Here, we use a combination of rapid-injection NMR spectroscopy, electrospray-ionization mass spectrometry, and quantum chemical calculations to demonstrate that these transformations involve argentate(i) and (iii) complexes as key intermediates.

[Evaluation of Xpert® MTB/RIF technique for Mycobacterium tuberculosis complex detection in extra-respiratory specimens].

PubMed

García, Patricia; Balcells, M Elvira; Castillo, Claudia; Miranda, Carolina; Geoffroy, Enrique; Román, Juan C; Wozniak, Aniela

2017-08-01

Extra-pulmonary tuberculosis (TB) represents the 26.2% of total TB cases in Chile. Culture is the gold standard method, but the process is extremely slow. Xpert®MTB/RIF technique detects Mycobacterium tuberculosis complex (MTBc) through real time PCR in less than 3 h. However, it has been validated only for respiratory specimens. We aimed to determine the performance of Xpert®MTB/RIF test in detecting MTBc in extra-respiratory specimens compared with a combined gold standard consisting in a positive (liquid and solid) mycobacterial culture and/or a positive validated molecular method (q-RPC, Cobas®TaqMan®-MTB). Fifty extra-respiratory specimens were analyzed, from which 25 were positive and 25 negative for MTBc based on the combined gold standard. The 25 positive specimens had a positive result by Xpert®MTB/RIF; from the 25 negative specimens, 24 had a negative result and one had a positive result. We obtained an overall concordance of 98% between Xpert®MTB/RIF and the combined gold standard. Xpert®MTB/RIF test was able to detect 12 smear-negative specimens and 3 culture-negative specimens, all of them corresponding to extra-pulmonary TB cases. Xpert®MTB/RIF showed similar sensitivity to q-RPC in detecting MTBc in extra-respiratory specimens. This procedure allowed a substantial reduction in the time of diagnosis.

Reaction landscape of a pentadentate N5-ligated Mn(II) complex with O2˙- and H2O2 includes conversion of a peroxomanganese(III) adduct to a bis(μ-oxo)dimanganese(III,IV) species.

PubMed

Leto, Domenick F; Chattopadhyay, Swarup; Day, Victor W; Jackson, Timothy A

2013-09-28

Herein we describe the chemical reactivity of the mononuclear [Mn(II)(N4py)(OTf)](OTf) (1) complex with hydrogen peroxide and superoxide. Treatment of 1 with one equivalent superoxide at -40 °C in MeCN formed the peroxomanganese(III) adduct, [Mn(III)(O2)(N4py)](+) (2) in ~30% yield. Complex 2 decayed over time and the formation of the bis(μ-oxo)dimanganese(III,IV) complex, [Mn(III)Mn(IV)(μ-O)2(N4py)2](3+) (3) was observed. When 2 was formed in higher yields (~60%) using excess superoxide, the [Mn(III)(O2)(N4py)](+) species thermally decayed to Mn(II) species and 3 was formed in no greater than 10% yield. Treatment of [Mn(III)(O2)(N4py)](+) with 1 resulted in the formation of 3 in ~90% yield, relative to the concentration of [Mn(III)(O2)(N4py)](+). This reaction mimics the observed chemistry of Mn-ribonucleotide reductase, as it features the conversion of two Mn(II) species to an oxo-bridged Mn(III)Mn(IV) compound using O2(-) as oxidant. Complex 3 was independently prepared through treatment of 1 with H2O2 and base at -40 °C. The geometric and electronic structures of 3 were probed using electronic absorption, electron paramagnetic resonance (EPR), magnetic circular dichroism (MCD), variable-temperature, variable-field MCD (VTVH-MCD), and X-ray absorption (XAS) spectroscopies. Complex 3 was structurally characterized by X-ray diffraction (XRD), which revealed the N4py ligand bound in an unusual tetradentate fashion.

Assessing the exchange coupling in binuclear lanthanide(iii) complexes and the slow relaxation of the magnetization in the antiferromagnetically coupled Dy2 derivative.

PubMed

Chow, Chun Y; Bolvin, Hélène; Campbell, Victoria E; Guillot, Régis; Kampf, Jeff W; Wernsdorfer, Wolfgang; Gendron, Frédéric; Autschbach, Jochen; Pecoraro, Vincent L; Mallah, Talal

2015-07-01

We report here the synthesis and the investigation of the magnetic properties of a series of binuclear lanthanide complexes belonging to the metallacrown family. The isostructural complexes have a core structure with the general formula [Ga 4 Ln 2 (shi 3- ) 4 (Hshi 2- ) 2 (H 2 shi - ) 2 (C 5 H 5 N) 4 (CH 3 OH) x (H 2 O) x ]· x C 5 H 5 N· x CH 3 OH· x H 2 O (where H 3 shi = salicylhydroxamic acid and Ln = Gd III 1 ; Tb III 2 ; Dy III 3 ; Er III 4 ; Y III 5 ; Y III 0.9 Dy III 0.1 6 ). Apart from the Er-containing complex, all complexes exhibit an antiferromagnetic exchange coupling leading to a diamagnetic ground state. Magnetic studies, below 2 K, on a single crystal of 3 using a micro-squid array reveal an opening of the magnetic hysteresis cycle at zero field. The dynamic susceptibility studies of 3 and of the diluted DyY 6 complexes reveal the presence of two relaxation processes for 3 that are due to the excited ferromagnetic state and to the uncoupled Dy III ions. The antiferromagnetic coupling in 3 was shown to be mainly due to an exchange mechanism, which accounts for about 2/3 of the energy gap between the antiferro- and the ferromagnetic states. The overlap integrals between the Natural Spin Orbitals (NSOs) of the mononuclear fragments, which are related to the magnitude of the antiferromagnetic exchange, are one order of magnitude larger for the Dy 2 than for the Er 2 complex.

Coexistence of spin crossover and magnetic ordering in a dendrimeric Fe(III) complex

NASA Astrophysics Data System (ADS)

Vorobeva, V. E.; Domracheva, N. E.; Pyataev, A. V.; Gruzdev, M. S.; Chervonova, U. V.

2015-01-01

The magnetic properties of a new dendrimeric spin crossover Fe(III) complex, [Fe(L)2]+PF6-, where L = 3,5-di[3,4,5-tris(tetradecyloxy) benzoyloxy]benzoyl-4-salicylidene-N-ethyl-N-ethylene-diamine, are reported for the first time. EPR studies show that this compound undergoes a gradual spin transition in the temperature range 70-300 K and has antiferromagnetic ordering below 10 K. Mössbauer spectroscopy at 5 K confirms the presence of magnetic ordering in the dendrimeric iron complex.

Changes in amniotic fluid concentration of thrombin-antithrombin III complexes in patients with preterm labor: evidence of an increased thrombin generation

PubMed Central

Erez, Offer; Romero, Roberto; Vaisbuch, Edi; Chaiworapongsa, Tinnakorn; Kusanovic, Juan Pedro; Mazaki-Tovi, Shali; Gotsch, Francesca; Gomez, Ricardo; Maymon, Eli; Pacora, Percy; Edwin, Samuel S.; Kim, Chong Jai; Than, Nandor Gabor; Mittal, Pooja; Yeo, Lami; Dong, Zhong; Yoon, Bo Hyun; Hassan, Sonia S; Mazor, Moshe

2012-01-01

Objective Preterm labor is associated with excessive maternal thrombin generation as evidenced by increased circulating thrombin–antithrombin (TAT) III complexes concentration. In addition to its hemostatic functions, thrombin has uterotonic properties that may participate in the mechanism leading to preterm birth in cases of intrauterine bleeding. Thrombin also has a proinflammatory role, and inflammation is associated with increased thrombin generation. The aim of this study was to determine whether intra-amniotic infection/inflammation (IAI) is associated with increased amniotic fluid (AF) thrombin generation in women with preterm and term deliveries. Study design This cross-sectional study included the following groups: 1) mid-trimester (n=74); 2) term not in labor (n=39); 3) term in labor (n=25); 4) term in labor with IAI (n=22); 5) spontaneous preterm labor (PTL) who delivered at term (n=62); 6) PTL without IAI who delivered preterm (n=59); 7) PTL with IAI (n=71). The AF TAT III complexes concentration was measured by ELISA. Non-parametric statistics were used for analysis. Results 1) TAT III complexes were identified in all AF samples; 2) patients with PTL who delivered preterm, with and without IAI, had a significantly higher median AF TAT III complexes concentration than those with an episode of PTL who delivered at term (p<0.001, p=0.03, respectively); 3) among patients with preterm labor without IAI, elevated AF TAT III complexes concentration were independently associated with a shorter amniocentesis-to-delivery interval (hazard ratio- 1.5, 95%CI, 1.07–2.1); 4) among patients at term, those with IAI had a higher median AF TAT III complexes concentration than those without IAI, whether in labor or not in labor (p=0.02); 5) there was no significant difference between the median AF TAT III complexes concentration of patients at term with and without labor; and 6) patients who had a mid-trimester amniocentesis had a lower median AF TAT III complexes

[Pathophysiology of respiratory muscle weakness].

PubMed

Windisch, W

2008-03-01

The respiratory system consists of two parts which can be impaired independently from each other, the lungs and the respiratory pump. The latter is a complex system covering different anatomic structures: the breathing centre, the peripheral nervous system, the respiratory muscles, and the thorax. According to this complexity several underlying conditions can cause insufficiency of the respiratory pump, i. e. ventilatory failure. Disturbances of the breathing centre, different neuromuscular disorders, impairments of the mechanics, such as thoracic deformities or hyperinflation, and airway obstruction are example conditions responsible for ventilatory failure. Main characteristic of ventilatory failure is the occurrence of hypercapnia which is in contrast to pulmonary failure where diffusion disturbances typically not cause hypercapnia. Both acute and chronic ventilatory failure presenting with hypercapnia can develop. In acute ventilatory failure respiratory acidosis develops, but in chronic respiratory failure pH is normalized as a consequence of metabolic retention of bicarbonate. However, acute on chronic ventilatory failure can present with a combined picture, i. e. elevated bicarbonate levels, acidosis, and often severe hypercapnia. Clinical signs such as tachypnea, features of the underlying disease or hypercapnia are important diagnostic tools in addition to the measurement of pressures generated by the respiratory muscles. Non-invasive and widely available techniques, such as the assessment of the maximal ins- and expiratory mouth pressures (PImax, PEmax), should be used as screening instruments, but the reliability of these measurements is reduced due to the volitional character of the tests and due to the impossibility to define normal values. Inspiratory pressures can be assessed more accurately and independently from the patients' effort: with or without the insertion of oesophageal and gastric balloon catheters. However, this technique is more invasive

Pirfenidone Reduces Respiratory-related Hospitalizations in Idiopathic Pulmonary Fibrosis.

PubMed

Ley, Brett; Swigris, Jeffrey; Day, Bann-Mo; Stauffer, John L; Raimundo, Karina; Chou, Willis; Collard, Harold R

2017-09-15

Respiratory-related hospitalizations of patients with idiopathic pulmonary fibrosis (IPF) are more frequent than those for acute IPF exacerbations and are associated with poor outcomes. To compare the risk of nonelective hospitalization by type (all-cause, respiratory related, and non-respiratory related) and death after hospitalization with use of pirfenidone versus placebo over 52 weeks using data derived from three phase III IPF clinical trials. Individual patient data was pooled from three phase III randomized, placebo-controlled studies of pirfenidone for IPF (the two CAPACITY [Clinical Studies Assessing Pirfenidone in IPF: Research of Efficacy and Safety Outcomes] trials and the ASCEND [Assessment of Pirfenidone to Confirm Efficacy and Safety in Idiopathic Pulmonary Fibrosis] trial), including all patients randomized to pirfenidone 2,403 mg/d (n = 623) or placebo (n = 624). The risk of hospitalization over 52 weeks was compared using standard time-to-event methods. Among those hospitalized, the risk of death after hospitalization was compared with adjustment for treatment group propensity. A total of 1,247 patients (692 from the CAPACITY trials and 555 from the ASCEND trial) were included in the pooled analysis. Pirfenidone was associated with lower risk of respiratory-related hospitalization than placebo (7% vs. 12%; hazard ratio [HR], 0.52; 95% confidence interval [CI], 0.36-0.77; P = 0.001), but all-cause (HR, 0.91; 95% CI, 0.70-1.19; P = 0.528) or non-respiratory-related hospitalization (HR, 1.32; 95% CI, 0.92-1.88; P = 0.145) was not. Among those hospitalized for any reason, treatment with pirfenidone was associated with lower risk of death after hospitalization up to 52 weeks after randomization, but this association was no longer significant with longer follow-up. In a pooled analysis of three phase III IPF clinical trials, patients receiving pirfenidone had a lower risk of nonelective respiratory-related hospitalization over the

Evaluating the metagenome of two sampling locations in the nasal cavity of cattle with bovine respiratory disease complex

USDA-ARS?s Scientific Manuscript database

Bovine respiratory disease complex (BRDC) is a multi-factor disease, and disease incidence may be associated with an animal’s commensal microbiota (metagenome). Evaluation of the animal’s resident microbiota in the nasal cavity may help us to understand the impact of the metagenome on incidence of ...

Coordination Complexes of Titanium(IV) and Indium(III) Phthalocyanines with Carbonyl-Containing Dyes: The Formation of Singly Bonded Anionic Squarylium Dimers.

PubMed

Konarev, Dmitri V; Kuzmin, Alexey V; Khasanov, Salavat S; Fatalov, Alexey M; Yudanova, Evgenia I; Lyubovskaya, Rimma N

2018-04-14

Reduction methods for the preparation of coordination complexes of titanium(IV) and indium(III) phthalocyanines (Pc) with organic dyes such as indigo, thioindigo, and squarylium dye III (SQ) have been developed, which allow one to obtain crystalline {cryptand(K + )}{(cis-indigo-O,O) 2- Ti IV (Pc 2- )}(Cl - )⋅C 6 H 4 Cl 2 (1), {cryptand(K + )}{(cis-thioindigo-O,O) 2- In III (Pc 2- )} - ⋅C 6 H 4 Cl 2 (2), and {cryptand(K + )}{[(SQ) 2 -O,O] 2- In III (Pc 2- )} - ⋅3.5 C 6 H 4 Cl 2 (3) complexes. The formation of these complexes is accompanied by the reduction of the starting dyes to the anionic state. Transition of trans-indigo or trans-thioindigo to the cis conformation in 1 and 2 provides coordination of both carbonyl oxygen atoms of the dye to Ti IV Pc or In III Pc. SQ is reduced to the radical anion state and forms unusual diamagnetic singly bonded (SQ - ) 2 dimers in 3. These dimers have two closely positioned carbonyl oxygen atoms coordinated to In III Pc. Dianionic Pc 2- macrocycles have been found in 1-3. The complexes contain two chromophore molecules at one metal center. However, their optical spectra are defined mainly by absorption bands of the metal phthalocyanines. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mitochondrial Ca2+ influx targets cardiolipin to disintegrate respiratory chain complex II for cell death induction

PubMed Central

Hwang, M-S; Schwall, C T; Pazarentzos, E; Datler, C; Alder, N N; Grimm, S

2014-01-01

Massive Ca2+ influx into mitochondria is critically involved in cell death induction but it is unknown how this activates the organelle for cell destruction. Using multiple approaches including subcellular fractionation, FRET in intact cells, and in vitro reconstitutions, we show that mitochondrial Ca2+ influx prompts complex II of the respiratory chain to disintegrate, thereby releasing an enzymatically competent sub-complex that generates excessive reactive oxygen species (ROS) for cell death induction. This Ca2+-dependent dissociation of complex II is also observed in model membrane systems, but not when cardiolipin is replaced with a lipid devoid of Ca2+ binding. Cardiolipin is known to associate with complex II and upon Ca2+ binding coalesces into separate homotypic clusters. When complex II is deprived of this lipid, it disintegrates for ROS formation and cell death. Our results reveal Ca2+ binding to cardiolipin for complex II disintegration as a pivotal step for oxidative stress and cell death induction. PMID:24948011

Synthesis, characterization, cytotoxic and antitubercular activities of new gold(I) and gold(III) complexes containing ligands derived from carbohydrates.

PubMed

Chaves, Joana Darc Souza; Damasceno, Jaqueline Lopes; Paula, Marcela Cristina Ferreira; de Oliveira, Pollyanna Francielli; Azevedo, Gustavo Chevitarese; Matos, Renato Camargo; Lourenço, Maria Cristina S; Tavares, Denise Crispim; Silva, Heveline; Fontes, Ana Paula Soares; de Almeida, Mauro Vieira

2015-10-01

Novel gold(I) and gold(III) complexes containing derivatives of D-galactose, D-ribose and D-glucono-1,5-lactone as ligands were synthesized and characterized by IR, (1)H, and (13)C NMR, high resolution mass spectra and cyclic voltammetry. The compounds were evaluated in vitro for their cytotoxicity against three types of tumor cells: cervical carcinoma (HeLa) breast adenocarcinoma (MCF-7) and glioblastoma (MO59J) and one non-tumor cell line: human lung fibroblasts (GM07492A). Their antitubercular activity was evaluated as well expressed as the minimum inhibitory concentration (MIC90) in μg/mL. In general, the gold(I) complexes were more active than gold(III) complexes, for example, the gold(I) complex (1) was about 8.8 times and 7.6 times more cytotoxic than gold(III) complex (8) in MO59J and MCF-7 cells, respectively. Ribose and alkyl phosphine derivative complexes were more active than galactose and aryl phosphine complexes. The presence of a thiazolidine ring did not improve the cytotoxicity. The study of the cytotoxic activity revealed effective antitumor activities for the gold(I) complexes, being more active than cisplatin in all the tested tumor cell lines. Gold(I) compounds (1), (2), (3), (4) and (6) exhibited relevant antitubercular activity even when compared with first line drugs such as rifampicin.

Expression of the transcription factor FOXP2 in brainstem respiratory circuits of adult rat is restricted to upper-airway pre-motor areas.

PubMed

Stanić, Davor; Dhingra, Rishi R; Dutschmann, Mathias

2018-04-01

Expression of the transcription factor FOXP2 is linked to brain circuits that control motor function and speech. Investigation of FOXP2 protein expression in respiratory areas of the ponto-medullary brainstem of adult rat revealed distinct rostro-caudal expression gradients. A high density of FOXP2 immunoreactive nuclei was observed within the rostral pontine Kölliker-Fuse nucleus, compared to low densities in caudal pontine and rostral medullary respiratory nuclei, including the: (i) noradrenergic A5 and parafacial respiratory groups; (ii) Bötzinger and pre-Bötzinger complex and; (iii) rostral ventral respiratory group. Moderate densities of FOXP2 immunoreactive nuclei were observed in the caudal ventral respiratory group and the nucleus retroambiguus, with significant density levels found in the caudal half of the dorsal respiratory group and the hypoglossal pre-motor area lateral around calamus scriptorius. FOXP2 immunoreactivity was absent in all cranial nerve motor nuclei. We conclude that FOXP2 expression in respiratory brainstem areas selectively delineates laryngeal and hypoglossal pre-motor neuron populations essential for the generation of sound and voice. Copyright © 2018 Elsevier B.V. All rights reserved.

Effects of tramadol, clonazepam, and their combination on brain mitochondrial complexes.

PubMed

Mohamed, Tarek Mostafa; Ghaffar, Hamdy M Abdel; El Husseiny, Rabee M R

2015-12-01

The present study is an unsubstantiated qualitative assessment of the abused drugs-tramadol and clonazepam. The aim of this study is to evaluate whether the effects of tramadol, clonazepam, and their combination on mitochondrial electron transport chain (ETC) complexes were influential at therapeutic or at progressively increasing doses. The study comprised of a total of 70 healthy male rats, aged 3 months. According to the drug intake regimen, animals were divided into seven groups: control, tramadol therapeutic, clonazepam therapeutic, combination therapeutic, tramadol abuse, clonazepam abuse, and combination abuse group. At the end of the experiment, brain mitochondrial ETC complexes (I, II, III, and IV) were evaluated. Histopathological examinations were also performed on brain tissues. The results showed that groups that received tramadol (therapeutic and abuse) suffered from weight loss. Tramadol abuse group and combination abuse group showed significant decrease in the activities of I, III, and IV complexes but not in the activity of complex II. In conclusion, tramadol but not clonazepam has been found to partially inhibit the activities of respiratory chain complexes I, III, and IV but not the activity of complex II and such inhibition occurred only at doses that exceeded the maximum recommended adult human daily therapeutic doses. This result explains the clinical and histopathological effects of tramadol, such as seizures and red neurons (marker for apoptosis), respectively. © The Author(s) 2012.

Anionic carbonato and oxalato cobalt(III) nitrogen mustard complexes.

PubMed

Craig, Peter R; Brothers, Penelope J; Clark, George R; Wilson, William R; Denny, William A; Ware, David C

2004-02-21

Synthetic approaches to cobalt(III) complexes [Co(L)(L')2] containing the bidentate dialkylating nitrogen mustard N,N-bis(2-chloroethyl)-1,2-ethanediamine (L = dce) together with anionic ancilliary ligands (L') which are either carbonato (CO3(2-)), oxalato (ox2-), bis(2-hydroxyethyl)dithiocarbamato (bhedtc-), 2-pyridine carboxylato (pico-) or 2-pyrazine carboxylato (pyzc-) were investigated. Synthetic routes were developed using the related amines N,N-diethyl-1,2-ethanediamine (dee) and 1,2-ethanediamine (en). The complexes [Co(CO3)2(L)]- (L = dee 1, dce 2), [Co(ox)2(L)]- (L = dee 3, dce 4), [Co(bhedtc)2(dee)]+ 5, [Co(bhedtc)2(en)]+ 6, mer-[Co(pico)3], mer-[Co(pyzc)]3 7 and [Co(pico)2(dee)]+ 8 were prepared and were characterised by IR, UV-Vis, 1H and 13C[1H] NMR spectroscopy, mass spectrometry and cyclic voltammetry. [Co(bhedtc)2(en)]BPh4 6b and trans(O)-[Co(pico)2(dee)]ClO4 8 were characterised by X-ray crystallography. In vitro biological tests were carried out on complexes 1-4 in order to assess the degree to which coordination of the mustard to cobalt attenuated its cytotoxicity, and the differential toxicity in air vs. nitrogen.

Role of the Diphosphine Chelate in Emissive, Charge-Neutral Iridium(III) Complexes.

PubMed

Liao, Jia-Ling; Devereux, Leon R; Fox, Mark A; Yang, Chun-Chieh; Chiang, Yu-Cheng; Chang, Chih-Hao; Lee, Gene-Hsiang; Chi, Yun

2018-01-12

A class of neutral tris-bidentate Ir III metal complexes incorporating a diphosphine as a chelate is prepared and characterized here for the first time. Treatment of [Ir(dppBz)(tht)Cl 3 ] (1, dppBz=1,2-bis(diphenylphosphino)benzene, tht=tetrahydrothiophene) with fppzH (3-trifluoromethyl-5-(2'-pyridyl)-1H-pyrazole) afforded the dichloride complexes, trans-(Cl,Cl)[Ir(dppBz)(fppz)Cl 2 ] (2) and cis-(Cl,Cl)[Ir(dppBz)(fppz)Cl 2 ] (3). The reaction of 3 with the dianionic chelate precursor, 5,5'-di(trifluoromethyl)-3,3'-bipyrazole (bipzH 2 ) or 5,5'-(1-methylethylidene)-bis(3-trifluoromethyl-1H-pyrazole) (mepzH 2 ), in DMF gave the tris-bidentate complex [Ir(dppBz)(fppz)(bipz)] (4) or [Ir(dppBz)(fppz)(mepz)] (5), respectively. In contrast, a hydride complex [Ir(dppBz)(fppz)(bipzH)H] (6) was isolated instead of 4 in protic solvent, namely: diethylene glycol monomethyl ether (DGME). All complexes 2-6 are luminescent in powder form and thin films where the dichlorides (2, 3) emit with maxima at 590-627 nm (orange) and quantum yields (QYs) up to 90 % whereas the tris-bidentate (4, 5) and hydride (6) complexes emit at 455-458 nm (blue) with QYs up to 70 %. Hybrid (time-dependent) DFT calculations showed considerable metal-to-ligand charge transfer contribution to the orange-emitting 2 and 3 but substantial ligand-centered 3 π-π* transition character in the blue-emitting 4-6. The dppBz does not participate in the radiative transitions in 4-6, but it provides the rigidity and steric bulk needed to promote the luminescence by suppressing the self-quenching in the solid state. Fabrication of an organic light-emitting diode (OLED) with dopant 5 gave a deep-blue CIE chromaticity of (0.16, 0.15). Superior blue emitters, which are vital in OLED applications, may be found in other neutral Ir III complexes containing phosphine chelates. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Absorption spectral analysis of 4f-4f transitions for the complexation of Pr(III) and Nd(III) with thiosemicarbazide in absence and presence of Zn(II) in aqueous and organic solvents

NASA Astrophysics Data System (ADS)

Anita, K.; Rajmuhon Singh, N.

2011-10-01

The complexation of thiosemicarbazide with Pr(III) and Nd(III) in absence and presence of Zn(II), a soft metal ion in aqueous and organic solvents like CH 3OH,CH 3CN, dioxane (C 4H 8O 2) and DMF (C 3H 7NO) and their equimolar mixtures are discussed by employing absorption difference and comparative absorption spectrophotometry. Complexation of thiosemicarbazide with Pr(III) and Nd(III) is indicated by the changes in the absorption intensity following the subsequent changes in the oscillator strength of different 4f-4f bands and Judd-Ofelt intensity ( Tλ) parameters. The other spectral parameters like energy interaction parameters namely Slater-Condon ( Fk), Racah ( Ek), Lande ( ξ4f), Nephelauxetic ratio ( β) and bonding parameters ( b1/2) are further computed to explain the nature of complexation. The difference in the energy parameters with respect to donor atoms and solvents reveal that the chemical environment around the lanthanide ions has great impact on f-f transition and any change in the environment result in modification of the spectra. Various solvents and their equimolar mixtures are also used to discuss the participation of solvents in the complexation.

pH-sensitive fluorescent sensors based on europium(III) complexes.

PubMed

Zhang, Xiaolin; Jiao, Yang; Jing, Xu; Wu, Hongmei; He, Guangjie; Duan, Chunying

2011-03-21

New europium(III) complexes Eu(TTA)(2)-DSQ and Eu(TTA)(3)-DR1 were designed and synthesized as new fluorescent pH probes (where HDSQ = 5-(dimethylamino)-N-(4-(2-((8-hydroxyquinolin-2-yl)methylene)hydrazinecarbonyl)phenyl)naphthalene-1-sulfonamide, DR1 = N(1)-(4-(dimethylamino)benzylidene)-N(2)-(rhodamine-6G) lactamethylene-diamine and TTA = thiophentrifluoroacetone). Eu(TTA)(2)-DSQ exhibited high sensitivity in monitoring pH changes in neutral aqueous solution with negligible background fluorescence. Eu(TTA)(3)-DR1 comprised a green light emitting Rhodamine 6G fluorophore and a Eu(III) moiety as the origin of red light. These pH-sensitive emitter components have pK(a) values of 5.0 and 7.2 respectively, and exhibit isolated protonated steps within one molecule. Luminescence titrations demonstrate that Eu(TTA)(3)-DR1 was able to detect pH values at both near neutral pH and acidic pH ranges, and was also able to detect pH in both cultured cells and in vivo.

Distinct respiratory responses of soils to complex organic substrate are governed predominantly by soil architecture and its microbial community.

PubMed

Fraser, F C; Todman, L C; Corstanje, R; Deeks, L K; Harris, J A; Pawlett, M; Whitmore, A P; Ritz, K

2016-12-01

Factors governing the turnover of organic matter (OM) added to soils, including substrate quality, climate, environment and biology, are well known, but their relative importance has been difficult to ascertain due to the interconnected nature of the soil system. This has made their inclusion in mechanistic models of OM turnover or nutrient cycling difficult despite the potential power of these models to unravel complex interactions. Using high temporal-resolution respirometery (6 min measurement intervals), we monitored the respiratory response of 67 soils sampled from across England and Wales over a 5 day period following the addition of a complex organic substrate (green barley powder). Four respiratory response archetypes were observed, characterised by different rates of respiration as well as different time-dependent patterns. We also found that it was possible to predict, with 95% accuracy, which type of respiratory behaviour a soil would exhibit based on certain physical and chemical soil properties combined with the size and phenotypic structure of the microbial community. Bulk density, microbial biomass carbon, water holding capacity and microbial community phenotype were identified as the four most important factors in predicting the soils' respiratory responses using a Bayesian belief network. These results show that the size and constitution of the microbial community are as important as physico-chemical properties of a soil in governing the respiratory response to OM addition. Such a combination suggests that the 'architecture' of the soil, i.e. the integration of the spatial organisation of the environment and the interactions between the communities living and functioning within the pore networks, is fundamentally important in regulating such processes.

Lutetium(iii) aqua ion: On the dynamical structure of the heaviest lanthanoid hydration complex

NASA Astrophysics Data System (ADS)

Sessa, Francesco; Spezia, Riccardo; D'Angelo, Paola

2016-05-01

The structure and dynamics of the lutetium(iii) ion in aqueous solution have been investigated by means of a polarizable force field molecular dynamics (MD). An 8-fold square antiprism (SAP) geometry has been found to be the dominant configuration of the lutetium(iii) aqua ion. Nevertheless, a low percentage of 9-fold complexes arranged in a tricapped trigonal prism (TTP) geometry has been also detected. Dynamic properties have been explored by carrying out six independent MD simulations for each of four different temperatures: 277 K, 298 K, 423 K, 632 K. The mean residence time of water molecules in the first hydration shell at room temperature has been found to increase as compared to the central elements of the lanthanoid series in agreement with previous experimental findings. Water exchange kinetic rate constants at each temperature and activation parameters of the process have been determined from the MD simulations. The obtained structural and dynamical results suggest that the water exchange process for the lutetium(iii) aqua ion proceeds with an associative mechanism, in which the SAP hydration complex undergoes temporary structural changes passing through a 9-fold TTP intermediate. Such results are consistent with the water exchange mechanism proposed for heavy lanthanoid atoms.

Lutetium(III) aqua ion: On the dynamical structure of the heaviest lanthanoid hydration complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sessa, Francesco; D’Angelo, Paola, E-mail: p.dangelo@uniroma1.it; Spezia, Riccardo

2016-05-28

The structure and dynamics of the lutetium(III) ion in aqueous solution have been investigated by means of a polarizable force field molecular dynamics (MD). An 8-fold square antiprism (SAP) geometry has been found to be the dominant configuration of the lutetium(III) aqua ion. Nevertheless, a low percentage of 9-fold complexes arranged in a tricapped trigonal prism (TTP) geometry has been also detected. Dynamic properties have been explored by carrying out six independent MD simulations for each of four different temperatures: 277 K, 298 K, 423 K, 632 K. The mean residence time of water molecules in the first hydration shellmore » at room temperature has been found to increase as compared to the central elements of the lanthanoid series in agreement with previous experimental findings. Water exchange kinetic rate constants at each temperature and activation parameters of the process have been determined from the MD simulations. The obtained structural and dynamical results suggest that the water exchange process for the lutetium(III) aqua ion proceeds with an associative mechanism, in which the SAP hydration complex undergoes temporary structural changes passing through a 9-fold TTP intermediate. Such results are consistent with the water exchange mechanism proposed for heavy lanthanoid atoms.« less

Lutetium(iii) aqua ion: On the dynamical structure of the heaviest lanthanoid hydration complex.

PubMed

Sessa, Francesco; Spezia, Riccardo; D'Angelo, Paola

2016-05-28

The structure and dynamics of the lutetium(iii) ion in aqueous solution have been investigated by means of a polarizable force field molecular dynamics (MD). An 8-fold square antiprism (SAP) geometry has been found to be the dominant configuration of the lutetium(iii) aqua ion. Nevertheless, a low percentage of 9-fold complexes arranged in a tricapped trigonal prism (TTP) geometry has been also detected. Dynamic properties have been explored by carrying out six independent MD simulations for each of four different temperatures: 277 K, 298 K, 423 K, 632 K. The mean residence time of water molecules in the first hydration shell at room temperature has been found to increase as compared to the central elements of the lanthanoid series in agreement with previous experimental findings. Water exchange kinetic rate constants at each temperature and activation parameters of the process have been determined from the MD simulations. The obtained structural and dynamical results suggest that the water exchange process for the lutetium(iii) aqua ion proceeds with an associative mechanism, in which the SAP hydration complex undergoes temporary structural changes passing through a 9-fold TTP intermediate. Such results are consistent with the water exchange mechanism proposed for heavy lanthanoid atoms.

Neodymium(III) Complexes of Dialkylphosphoric and Dialkylphosphonic Acids Relevant to Liquid-Liquid Extraction Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lumetta, Gregg J.; Sinkov, Sergey I.; Krause, Jeanette A.

2016-01-27

The complexes formed during the extraction of neodymium(III) into hydrophobic solvents containing acidic organophosphorus extractants were probed by single-crystal X-ray diffractometry, visible spectrophotometry, and Fourier-transform infrared spectroscopy. The crystal structure of the compound Nd(DMP)3 (1, DMP = dimethyl phosphate) revealed a polymeric arrangement in which each Nd(III) center is surrounded by six DMP oxygen atoms in a pseudo-octahedral environment. Adjacent Nd(III) ions are bridged by (MeO)2POO– anions, forming the polymeric network. The diffuse reflectance visible spectrum of 1 is nearly identical to that of the solid that is formed when an n-dodecane solution of di-(2-ethylhexyl)phosphoric acid (HA) is saturated withmore » Nd(III), indicating a similar coordination environment around the Nd center in the NdA3 solid. The visible spectrum of the HA solution fully loaded with Nd(III) is very similar to that of the NdA3 material, both displaying hypersensitive bands characteristic of an pseudo-octahedral coordination environment around Nd. These spectral characteristics persisted across a wide range of organic Nd concentrations, suggesting that the pseudo-octahedral coordination environment is maintained from dilute to saturated conditions.« less

Neodymium(III) Complexes of Dialkylphosphoric and Dialkylphosphonic Acids Relevant to Liquid-Liquid Extraction Systems.

PubMed

Lumetta, Gregg J; Sinkov, Sergey I; Krause, Jeanette A; Sweet, Lucas E

2016-02-15

The complexes formed during the extraction of neodymium(III) into hydrophobic solvents containing acidic organophosphorus extractants were probed by single-crystal X-ray diffractometry, visible spectrophotometry, and Fourier-transform infrared spectroscopy. The crystal structure of the compound Nd(DMP)3 (1, DMP = dimethyl phosphate) revealed a polymeric arrangement in which each Nd(III) center is surrounded by six DMP oxygen atoms in a pseudo-octahedral environment. Adjacent Nd(III) ions are bridged by (MeO)2POO(-) anions, forming the polymeric network. The diffuse reflectance visible spectrum of 1 is nearly identical to that of the solid that is formed when an n-dodecane solution of di(2-ethylhexyl)phosphoric acid (HA) is saturated with Nd(III), indicating a similar coordination environment around the Nd center in the NdA3 solid. The visible spectrum of the HA solution fully loaded with Nd(III) is very similar to that of the NdA3 material, both displaying hypersensitive bands characteristic of an pseudo-octahedral coordination environment around Nd. These spectral characteristics persisted across a wide range of organic Nd concentrations, suggesting that the pseudo-octahedral coordination environment is maintained from dilute to saturated conditions.

Silica nanoparticles for micro-particle imaging velocimetry: fluorosurfactant improves nanoparticle stability and brightness of immobilized iridium(III) complexes.

PubMed

Lewis, David J; Dore, Valentina; Rogers, Nicola J; Mole, Thomas K; Nash, Gerard B; Angeli, Panagiota; Pikramenou, Zoe

2013-11-26

To establish highly luminescent nanoparticles for monitoring fluid flows, we examined the preparation of silica nanoparticles based on immobilization of a cyclometalated iridium(III) complex and an examination of the photophysical studies provided a good insight into the Ir(III) microenvironment in order to reveal the most suitable silica nanoparticles for micro particle imaging velocimetry (μ-PIV) studies. Iridium complexes covalently incorporated at the surface of preformed silica nanoparticles, [Ir-4]@Si500-Z, using a fluorinated polymer during their preparation, demonstrated better stability than those without the polymer, [Ir-4]@Si500, as well as an increase in steady state photoluminescence intensity (and therefore particle brightness) and lifetimes which are increased by 7-fold compared with nanoparticles with the same metal complex attached covalently throughout their core, [Ir-4]⊂Si500. Screening of the nanoparticles in fluid flows using epi-luminescence microscopy also confirm that the brightest, and therefore most suitable particles for microparticle imaging velocimetry (μ-PIV) measurements are those with the Ir(III) complex immobilized at the surface with fluorosurfactant, that is [Ir-4]@Si500-Z. μ-PIV studies demonstrate the suitability of these nanoparticles as nanotracers in microchannels.

Impact of zeolite-Y framework on the geometry and reactivity of Ru (III) benzimidazole complexes - A DFT study

NASA Astrophysics Data System (ADS)

Selvaraj, Tamilmani; Rajalingam, Renganathan; Balasubramanian, Viswanathan

2018-03-01

A detailed comparative Density Functional Theory (DFT) study is made to understand the structural changes of the guest complex due to steric and electronic interactions with the host framework. In this study, Ru(III) benzimidazole and 2- ethyl Ru(III) benzimidazole complexes encapsulated in a supercage of zeolite Y. The zeolitic framework integrity is not disturbed by the intrusion of the large guest complex. A blue shift in the d-d transition observed in the UV-Visible spectroscopic studies of the zeolite encapsulated complexes and they shows a higher catalytic efficiency. Encapsulation of zeolite matrix makes the metal center more viable to nucleophilic attack and favors the phenol oxidation reaction. Based on the theoretical calculations, transition states and structures of reaction intermediates involved in the catalytic cycles are derived.

Bifunctional Zn(II)Ln(III) dinuclear complexes combining field induced SMM behavior and luminescence: enhanced NIR lanthanide emission by 9-anthracene carboxylate bridging ligands.

PubMed

Palacios, María A; Titos-Padilla, Silvia; Ruiz, José; Herrera, Juan Manuel; Pope, Simon J A; Brechin, Euan K; Colacio, Enrique

2014-02-03

There were new dinuclear Zn(II)-Ln(III) complexes of general formulas [Zn(μ-L)(μ-OAc)Ln(NO3)2] (Ln(III) = Tb (1), Dy (2), Er (3), and Yb (4)), [Zn(μ-L)(μ-NO3)Er(NO3)2] (5), [Zn(H2O)(μ-L)Nd(NO3)3]·2CH3OH (6), [Zn(μ-L)(μ-9-An)Ln(NO3)2]·2CH3CN (Ln(III) = Tb (7), Dy (8), Er (9), Yb(10)), [Zn(μ-L)(μ-9-An)Yb(9-An)(NO3)3]·3CH3CN (11), [Zn(μ-L)(μ-9-An)Nd(9-An)(NO3)3]·2CH3CN·3H2O (12), and [Zn(μ-L)(μ-9-An)Nd(CH3OH)2(NO3)]ClO4·2CH3OH (13) prepared from the reaction of the compartmental ligand N,N',N″-trimethyl-N,N″-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H2L), with ZnX2·nH2O (X = NO3(-) or OAc(-)) salts, Ln(NO3)3·nH2O, and, in some instances, 9-anthracenecarboxylate anion (9-An). In all these complexes, the Zn(II) ions invariably occupy the internal N3O2 site whereas the Ln(III) ions show preference for the O4 external site, giving rise to a Zn(μ-diphenoxo)Ln bridging fragment. Depending on the Zn(II) salt and solvent used in the reaction, a third bridge can connect the Zn(II) and Ln(III) metal ions, giving rise to triple-bridged diphenoxoacetate in complexes 1-4, diphenoxonitrate in complex 5, and diphenoxo(9-anthracenecarboxylate) in complexes 8-13. Dy(III) and Er(III) complexes 2, 8 and 3, 5, respectively, exhibit field induced single molecule magnet (SMM) behavior, with Ueff values ranging from 11.7 (3) to 41(2) K. Additionally, the solid-state photophysical properties of these complexes are presented showing that ligand L(2-) is able to sensitize Tb(III)- and Dy(III)-based luminescence in the visible region through an energy transfer process (antenna effect). The efficiency of this process is much lower when NIR emitters such as Er(III), Nd(III), and Yb(III) are considered. When the luminophore 9-anthracene carboxylate is incorporated into these complexes, the NIR luminescence is enhanced which proves the efficiency of this bridging ligand to act as antenna group. Complexes 2, 3, 5, and 8 can be considered as dual materials

Synthesis, photoluminescence and biological properties of terbium(III) complexes with hydroxyketone and nitrogen containing heterocyclic ligands

NASA Astrophysics Data System (ADS)

Poonam; Kumar, Rajesh; Boora, Priti; Khatkar, Anurag; Khatkar, S. P.; Taxak, V. B.

2016-01-01

The ternary terbium(III) complexes [Tb(HDAP)3ṡbiq], [Tb(HDAP)3ṡdmph] and [Tb(HDAP)3ṡbathophen] were prepared by using methoxy substituted hydroxyketone ligand HDAP (2-hydroxy-4,6-dimethoxyacetophenone) and an ancillary ligand 2,2-biquinoline or 5,6-dimethyl-1,10-phenanthroline or bathophenanthroline respectively. The ligand and synthesized complexes were characterised based on elemental analysis, FT-IR and 1H NMR. Thermal behaviour of the synthesized complexes illustrates the general decomposition patterns of the complexes by thermogravimetric analysis. Photophysical properties such as excitation spectra, emission spectra and luminescence decay curves of the complexes were investigated in detail. The main green emitting peak at 548 nm can be attributed to 5D4 → 7F5 of Tb3+ ion. Thus, these complexes might be used to make a bright green light-emitting diode for display purpose. In addition the in vitro antibacterial activities of HDAP and its Tb(III) complexes against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and antifungal activities against Candida albicans and Aspergillus niger are reported. The Tb3+ complexes were found to be more potent antimicrobial agent as compared to the ligand. Among all these complexes, [Tb(HDAP)3ṡbathophen] exhibited excellent antimicrobial activity which proves its potential usefulness as an antimicrobial agent. Furthermore, in vitro antioxidant activity tests were carried out by using DPPH method which indicates that the complexes have considerable antioxidant activity when compared with the standard ascorbic acid.

Localisation of deformations of the midfacial complex in subjects with class III malocclusions employing thin-plate spline analysis

PubMed Central

SINGH, G. D.; McNAMARA JR, J. A.; LOZANOFF, S.

1997-01-01

This study determines deformations of the midface that contribute to a class III appearance, employing thin-plate spline analysis. A total of 135 lateral cephalographs of prepubertal children of European-American descent with either class III malocclusions or a class I molar occlusion were compared. The cephalographs were traced and checked, and 7 homologous landmarks of the midface were identified and digitised. The data sets were scaled to an equivalent size and subjected to Procrustes analysis. These statistical tests indicated significant differences (P<0.05) between the averaged class I and class III morphologies. Thin-plate spline analysis indicated that both affine and nonaffine transformations contribute towards the total spline for the averaged midfacial configuration. For nonaffine transformations, partial warp 3 had the highest magnitude, indicating the large scale deformations of the midfacial configuration. These deformations affected the palatal landmarks, and were associated with compression of the midfacial complex in the anteroposterior plane predominantly. Partial warp 4 produced some vertical compression of the posterior aspect of the midfacial complex whereas partial warps 1 and 2 indicated localised shape changes of the maxillary alveolus region. Large spatial-scale deformations therefore affect the midfacial complex in an anteroposterior axis, in combination with vertical compression and localised distortions. These deformations may represent a developmental diminution of the palatal complex anteroposteriorly that, allied with vertical shortening of midfacial height posteriorly, results in class III malocclusions with a retrusive midfacial profile. PMID:9449078

Localisation of deformations of the midfacial complex in subjects with class III malocclusions employing thin-plate spline analysis.

PubMed

Singh, G D; McNamara, J A; Lozanoff, S

1997-11-01

This study determines deformations of the midface that contribute to a class III appearance, employing thinplate spline analysis. A total of 135 lateral cephalographs of prepubertal children of European-American descent with either class III malocclusions or a class I molar occlusion were compared. The cephalographs were traced and checked, and 7 homologous landmarks of the midface were identified and digitised. The data sets were scaled to an equivalent size and subjected to Procrustes analysis. These statistical tests indicated significant differences (P < 0.05) between the averaged class I and class III morphologies. Thinplate spline analysis indicated that both affine and nonaffine transformations contribute towards the total spline for the averaged midfacial configuration. For nonaffine transformations, partial warp 3 had the highest magnitude, indicating the large scale deformations of the midfacial configuration. These deformations affected the palatal landmarks, and were associated with compression of the midfacial complex in the anteroposterior plane predominantly. Partial warp 4 produced some vertical compression of the posterior aspect of the midfacial complex whereas partial warps 1 and 2 indicated localised shape changes of the maxillary alveolus region. large spatial-scale deformations therefore affect the midfacial complex in an anteroposterior axis, in combination with vertical compression and localised distortions. These deformations may represent a developmental diminution of the palatal complex anteroposteriorly that, allied with vertical shortening of midfacial height posteriorly, results in class III malocclusions with a retrusive midfacial profile.

Malfunctioning of the iron-sulfur cluster assembly machinery in Saccharomyces cerevisiae produces oxidative stress via an iron-dependent mechanism, causing dysfunction in respiratory complexes.

PubMed

Gomez, Mauricio; Pérez-Gallardo, Rocío V; Sánchez, Luis A; Díaz-Pérez, Alma L; Cortés-Rojo, Christian; Meza Carmen, Victor; Saavedra-Molina, Alfredo; Lara-Romero, Javier; Jiménez-Sandoval, Sergio; Rodríguez, Francisco; Rodríguez-Zavala, José S; Campos-García, Jesús

2014-01-01

Biogenesis and recycling of iron-sulfur (Fe-S) clusters play important roles in the iron homeostasis mechanisms involved in mitochondrial function. In Saccharomyces cerevisiae, the Fe-S clusters are assembled into apoproteins by the iron-sulfur cluster machinery (ISC). The aim of the present study was to determine the effects of ISC gene deletion and consequent iron release under oxidative stress conditions on mitochondrial functionality in S. cerevisiae. Reactive oxygen species (ROS) generation, caused by H2O2, menadione, or ethanol, was associated with a loss of iron homeostasis and exacerbated by ISC system dysfunction. ISC mutants showed increased free Fe2+ content, exacerbated by ROS-inducers, causing an increase in ROS, which was decreased by the addition of an iron chelator. Our study suggests that the increment in free Fe2+ associated with ROS generation may have originated from mitochondria, probably Fe-S cluster proteins, under both normal and oxidative stress conditions, suggesting that Fe-S cluster anabolism is affected. Raman spectroscopy analysis and immunoblotting indicated that in mitochondria from SSQ1 and ISA1 mutants, the content of [Fe-S] centers was decreased, as was formation of Rieske protein-dependent supercomplex III2IV2, but this was not observed in the iron-deficient ATX1 and MRS4 mutants. In addition, the activity of complexes II and IV from the electron transport chain (ETC) was impaired or totally abolished in SSQ1 and ISA1 mutants. These results confirm that the ISC system plays important roles in iron homeostasis, ROS stress, and in assembly of supercomplexes III2IV2 and III2IV1, thus affecting the functionality of the respiratory chain.

Effects of maturation and acidosis on the chaos-like complexity of the neural respiratory output in the isolated brainstem of the tadpole, Rana esculenta.

PubMed

Straus, Christian; Samara, Ziyad; Fiamma, Marie-Noëlle; Bautin, Nathalie; Ranohavimparany, Anja; Le Coz, Patrick; Golmard, Jean-Louis; Darré, Pierre; Zelter, Marc; Poon, Chi-Sang; Similowski, Thomas

2011-05-01

Human ventilation at rest exhibits mathematical chaos-like complexity that can be described as long-term unpredictability mediated (in whole or in part) by some low-dimensional nonlinear deterministic process. Although various physiological and pathological situations can affect respiratory complexity, the underlying mechanisms remain incompletely elucidated. If such chaos-like complexity is an intrinsic property of central respiratory generators, it should appear or increase when these structures mature or are stimulated. To test this hypothesis, we employed the isolated tadpole brainstem model [Rana (Pelophylax) esculenta] and recorded the neural respiratory output (buccal and lung rhythms) of pre- (n = 8) and postmetamorphic tadpoles (n = 8), at physiologic (7.8) and acidic pH (7.4). We analyzed the root mean square of the cranial nerve V or VII neurograms. Development and acidosis had no effect on buccal period. Lung frequency increased with development (P < 0.0001). It also increased with acidosis, but in postmetamorphic tadpoles only (P < 0.05). The noise-titration technique evidenced low-dimensional nonlinearities in all the postmetamorphic brainstems, at both pH. Chaos-like complexity, assessed through the noise limit, increased from pH 7.8 to pH 7.4 (P < 0.01). In contrast, linear models best fitted the ventilatory rhythm in all but one of the premetamorphic preparations at pH 7.8 (P < 0.005 vs. postmetamorphic) and in four at pH 7.4 (not significant vs. postmetamorphic). Therefore, in a lower vertebrate model, the brainstem respiratory central rhythm generator accounts for ventilatory chaos-like complexity, especially in the postmetamorphic stage and at low pH. According to the ventilatory generators homology theory, this may also be the case in mammals.

The life of plant mitochondrial complex I.