bluuebunny/crossref_metadata_2025 huggingface dataset:
Addition of Gentamicin or Rifampin Does Not Enhance the Effectiveness of Daptomycin in Treatment of Experimental Endocarditis Due to Methicillin-Resistant
Staphylococcus aureus
Authors: Miró J. M. , García-de-la-Mària C. , Armero Y. , Soy D. , Moreno A. , del Río A. , Almela M. , Sarasa M. , Mestres C. A. , Gatell J. M. , Jiménez de Anta M. T. , Marco F.
Published: July 2009

This study evaluated the activity of daptomycin combined with either gentamicin or rifampin against three methicillin-resistant
Staphylococcus aureus
(MRSA) clinical isolates in vitro and one isolate in vivo against a representative strain (MRSA-572). Time-kill experiments showed that daptomycin was bactericidal against these strains at concentrations over the MIC. Daptomycin at sub-MIC concentrations plus gentamicin at 1× and 2× the MIC yielded synergy, while the addition of rifampin at 2 to 4 μg/ml resulted in indifference (two strains) or antagonism (one strain). The in vivo activity of daptomycin (6 mg/kg of body weight once a day) was evaluated ± gentamicin (1 mg/kg intravenously [i.v.] every 8 h [q8h]) or rifampin (300 mg i.v. q8h) in a rabbit model of infective endocarditis by simulating human pharmacokinetics. Daptomycin plus gentamicin (median, 0 [interquartile range, 0 to 2] log
10
CFU/g vegetation) was as effective as daptomycin alone (0 [0 to 2] log
10
CFU/g vegetation) in reducing the density of bacteria in valve vegetations (
P
= 0.83), and both were more effective than daptomycin plus rifampin (3 [2 to 3.5] log
10
CFU/g vegetation;
P
< 0.05) for the strain studied. In addition, daptomycin sterilized a ratio of vegetations that was similar to that of daptomycin plus gentamicin (10/15 [67%] versus 9/15 [60%];
P
= 0.7), and both regimens did so more than daptomycin plus rifampin (3/15 [20%];
P
= 0.01 and
P
= 0.02, respectively). No statistical difference was noted between daptomycin plus gentamicin and daptomycin alone for MRSA treatment. In the combination arm, all isolates from vegetations remained susceptible to daptomycin, gentamicin, and rifampin. Sixty-one percent of the isolates (8/13) acquired resistance to rifampin during monotherapy. In the daptomycin arm, resistance was detected in only one case, in which the daptomycin MIC rose to 2 μg/ml among the recovered bacteria. In conclusion, the addition of gentamicin or rifampin does not enhance the effectiveness of daptomycin in the treatment of experimental endocarditis due to MRSA.
Evaluating Aztreonam and Ceftazidime Pharmacodynamics withEscherichia coliin Combination with Daptomycin, Linezolid, or Vancomycin in an In Vitro Pharmacodynamic Model
Authors: LaPlante Kerry L. , Sakoulas George
Published: July 2009

In an in vitro pharmacodynamic model, linezolid attenuated the activity of aztreonam and ceftazidime againstEscherichia coli. Conversely, synergy was detected at 24 and 48 h when daptomycin or vancomycin was added to aztreonam and ceftazidime. We conclude that significant yet underappreciated interactions may occur between gram-positive-spectrum and gram-negative-spectrum antibacterials.
Development and Validation of a Fluorescent Microsphere Immunoassay for Soluble CD30 Testing
Authors: Pavlov Igor , Martins Thomas B. , Delgado Julio C.
Published: July 2009

Testing for soluble CD30 (sCD30), an indicator of Th2 immune response, is a useful prognostic marker in solid organ transplantation, lymphoproliferative disorders, autoimmunity, and various parasitic diseases. In this study we report the development and validation of a fluorescent microsphere immunoassay for the detection of sCD30 in serum, plasma, and culture supernatants. The dynamic range of this assay is 1 to 400 ng/ml, and the rate of recovery of various concentrations of recombinant sCD30 ranges from 97 to 116% (average recovery, 105%). The test showed a high degree of precision in both intra-assay and interassay studies (coefficients of variation, as high as 7% and 8%, respectively), with a sensitivity of 1 ng/ml. The normal reference range calculated for a cohort of 151 healthy individuals was 1 to 29 ng/ml. The clinical usefulness of the sCD30 fluorescent microsphere immunoassay was demonstrated by showing that levels of sCD30 have a positive correlation with specimens containing high titers of anti-double-stranded DNA antibodies and high titers of immunoglobulin G againstLeishmaniaspecies. Given the multiplexing potential of the sCD30 fluorescent microsphere immunoassay reported in this study, it is expected that testing of sCD30 concentrations along with those of other cytokines will become an important diagnostic tool for selected immunological and inflammatory diseases where Th2-type cytokine responses have been reported.
Antiretroviral Therapy Restores Diversity in the T-Cell Receptor Vβ Repertoire of CD4 T-Cell Subpopulations among Human Immunodeficiency Virus Type 1-Infected Children and Adolescents
Authors: Yin Li , Kou Zhong Chen , Rodriguez Carina , Hou Wei , Goodenow Maureen M. , Sleasman John W.
Published: July 2009

Human immunodeficiency virus (HIV) type 1 infection perturbs the T-cell receptor (TCR) Vβ repertoire. The TCR CDR3 length diversity of individual Vβ families was examined within CD45RA and CD45RO CD4 T cells to assess the impact of the virus on clonality throughout CD4 T-cell activation and differentiation. A cross-sectional and longitudinal cohort study of 13 HIV-infected and 8 age-matched healthy children and adolescents examined the Vβ CDR3 length profiles within CD4 T-cell subsets by the use of spectratyping. HIV-infected subjects demonstrated higher numbers of perturbations in CD4 CD45RA T cells (5.8 ± 4.9 Vβ families) than healthy individuals (1.6 ± 1.8 Vβ families) (P= 0.04). Surprisingly, CD4 CD45RO central memory T cells from infected subjects showed no increased perturbations compared to the perturbations for the same cells from healthy subjects (2.9 ± 3.1 and 1.1 ± 1.8 Vβ families, respectively;P= 0.11). CD4 CD45RA TCR perturbations were higher among infected subjects with >25% CD4 cells than healthy subjects (mean number of perturbed Vβfamilies, 6.6 ± 5.4;P= 0.04). No correlations between perturbations in CD4 subsets and pretherapy age or viral load were evident. In contrast to CD8 T cells, HIV induces TCR disruptions within CD45RA but not CD45RO CD4 T cells. Therapy-induced viral suppression resulted in increases in thymic output and the normalization of the diversity of TCR within CD45RA CD4 T cells after 2 months of treatment. Perturbations occur prior to CD4 T-cell attrition and normalize with effective antiretroviral therapy. The impact of HIV on the diversity of TCR within naïve, central memory, and effector memory CD4 T cells is distinctly different from that in CD8 T cells.
The Flagella of an Atypical Enteropathogenic
Escherichia coli
Strain Are Required for Efficient Interaction with and Stimulation of Interleukin-8 Production by Enterocytes In Vitro
Authors: Sampaio Suely C. F. , Gomes Tânia A. T. , Pichon Christophe , du Merle Laurence , Guadagnini Stéphanie , Abe Cecilia M. , Sampaio Jorge L. M. , Le Bouguénec Chantal
Published: July 2009

The ability of some typical enteropathogenic
Escherichia coli
(EPEC) strains to adhere to, invade, and increase interleukin-8 (IL-8) production in intestinal epithelial cells in vitro has been demonstrated. However, few studies regarding these aspects have been performed with atypical EPEC (aEPEC) strains, which are emerging enteropathogens in Brazil. In this study, we evaluated a selected aEPEC strain (1711-4) of serotype O51:H40, the most prevalent aEPEC serotype in Brazil, in regard to its ability to adhere to and invade Caco-2 and T84 cells and to elicit IL-8 production in Caco-2 cells. The role of flagella in aEPEC 1711-4 adhesion, invasion, and IL-8 production was investigated by performing the same experiments with an isogenic aEPEC mutant unable to produce flagellin (FliC), the flagellum protein subunit. We demonstrated that this mutant (
fliC
mutant) had a marked decrease in the ability to adhere to T84 cells and invade both T84 and Caco-2 cells in gentamicin protection assays and by transmission electron microscopy. In addition, the aEPEC 1711-4
fliC
mutant had a reduced ability to stimulate IL-8 production by Caco-2 cells in early (3-h) but not in late (24-h) infections. Our findings demonstrate that flagella of aEPEC 1711-4 are required for efficient adhesion, invasion, and early but not late IL-8 production in intestinal epithelial cells in vitro.
Inhibitory Antibodies Specific for the 19-Kilodalton Fragment of Merozoite Surface Protein 1 Do Not Correlate with Delayed Appearance of Infection withPlasmodium falciparumin Semi-Immune Individuals in Vietnam
Authors: Murhandarwati E. Elsa Herdiana , Wang Lina , Black Casilda G. , Nhan Doan Hanh , Richie Thomas L. , Coppel Ross L.
Published: July 2009

Inhibitory antibodies specific for the 19-kDa fragment of merozoite surface protein 1 (MSP119) are a significant component of inhibitory responses in individuals immune to malaria. Nevertheless, conflicting results have been obtained in determining whether this antibody specificity correlates with protection in residents of areas where malaria is endemic. In this study, we examined sera collected from a population of semi-immune individuals living in an area of Vietnam with meso-endemicity during a 6-month period. We used twoPlasmodium falciparumparasite lines that express either endogenous MSP119or the homologous region fromPlasmodium yoeliito measure the MSP119-specific inhibitory activity. We showed that (i) the level of MSP119-specific inhibitory antibodies was not associated with a delay inP. falciparuminfection, (ii) MSP119-specific inhibitory antibodies declined significantly during the convalescent period after infection, and (iii) there was no significant correlation between the MSP119-specific inhibitory antibodies and the total antibodies measured by enzyme-linked immunosorbent assay. These results have implications for understanding naturally acquired immunity to malaria and for the development and evaluation of MSP119-based vaccines.
Direct Sequencing of
Legionella pneumophila
from Respiratory Samples for Sequence-Based Typing Analysis
Authors: Coscollá Mireia , González-Candelas Fernando
Published: July 2009

We have developed a procedure to test the efficiency and reliability of sequencing of
Legionella pneumophila
genes directly from respiratory samples and have compared the results with those derived from cultured isolates. We tried to obtain the nucleotide sequences of six protein-coding loci included in the sequence-based typing scheme for
Legionella pneumophila
and three intergenic regions from 132 samples corresponding to 106 patients positive for urine antigen. A seminested PCR approach was used to amplify and sequence these nine loci directly from respiratory samples. Nucleotide sequences were directly obtained for 23
Legionella
isolates and also for 66 respiratory secretions from a total of 69 patients. The efficiency of sequencing from respiratory secretions was higher than that of sequencing after the isolation of the
Legionella
isolates. Moreover, the perfect match between the sequences obtained by both approaches when respiratory samples and cultured isolates from the same patient were available corroborates the suitability of the direct sequencing approach for the identification of
Legionella
species and molecular epidemiology studies with
Legionella
species.
Cooccurrence of Predominant Panton-Valentine Leukocidin-Positive Sequence Type (ST) 152 and Multidrug-Resistant ST 241
Staphylococcus aureus
Clones in Nigerian Hospitals
Authors: Okon Kenneth O. , Basset Patrick , Uba Auwalu , Lin Johnson , Oyawoye Bukola , Shittu Adebayo O. , Blanc Dominique S.
Published: July 2009

Ninety-six clinical isolates of
Staphylococcus aureus
from Nigeria were characterized phenotypically and genetically. Twelve multidrug-resistant methicillin (meticillin)-resistant
S. aureus
(MRSA) isolates carrying a new staphylococcal cassette chromosome
mec
element and a high proportion of Panton-Valentine leukocidin (PVL)-positive methicillin-susceptible
S. aureus
(MSSA) isolates were observed. The cooccurrence of multidrug-resistant MRSA and PVL-positive MSSA isolates entails the risk of emergence of a multidrug-resistant PVL-positive MRSA clone.
Characterization of Hepatitis C Virus Core Protein Multimerization and Membrane Envelopment: Revelation of a Cascade of Core-Membrane Interactions
Authors: Ai Li-Shuang , Lee Yu-Wen , Chen Steve S.-L.
Published: July 2009

The molecular basis underlying hepatitis C virus (HCV) core protein maturation and morphogenesis remains elusive. We characterized the concerted events associated with core protein multimerization and interaction with membranes. Analyses of core proteins expressed from a subgenomic system showed that the signal sequence located between the core and envelope glycoprotein E1 is critical for core association with endoplasmic reticula (ER)/late endosomes and the core's envelopment by membranes, which was judged by the core's acquisition of resistance to proteinase K digestion. Despite exerting an inhibitory effect on the core's association with membranes, (Z-LL)
2
-ketone, a specific inhibitor of signal peptide peptidase (SPP), did not affect core multimeric complex formation, suggesting that oligomeric core complex formation proceeds prior to or upon core attachment to membranes. Protease-resistant core complexes that contained both innate and processed proteins were detected in the presence of (Z-LL)
2
-ketone, implying that core envelopment occurs after intramembrane cleavage. Mutations of the core that prevent signal peptide cleavage or coexpression with an SPP loss-of-function D219A mutant decreased the core's envelopment, demonstrating that SPP-mediated cleavage is required for core envelopment. Analyses of core mutants with a deletion in domain I revealed that this domain contains sequences crucial for core envelopment. The core proteins expressed by infectious JFH1 and Jc1 RNAs in Huh7 cells also assembled into a multimeric complex, associated with ER/late-endosomal membranes, and were enveloped by membranes. Treatment with (Z-LL)
2
-ketone or coexpression with D219A mutant SPP interfered with both core envelopment and infectious HCV production, indicating a critical role of core envelopment in HCV morphogenesis. The results provide mechanistic insights into the sequential and coordinated processes during the association of the HCV core protein with membranes in the early phase of virus maturation and morphogenesis.
The Carboxy-Terminal Tail of Human Cytomegalovirus (HCMV) US28 Regulates both Chemokine-Independent and Chemokine-Dependent Signaling in HCMV-Infected Cells
Authors: Stropes Melissa P. , Schneider Olivia D. , Zagorski William A. , Miller Jeanette L. C. , Miller William E.
Published: July 2009

The human cytomegalovirus (HCMV)-encoded G-protein-coupled receptor (GPCR) US28 is a potent activator of a number of signaling pathways in HCMV-infected cells. The intracellular carboxy-terminal domain of US28 contains residues critical for the regulation of US28 signaling in heterologous expression systems; however, the role that this domain plays during HCMV infection remains unknown. For this study, we constructed an HCMV recombinant virus encoding a carboxy-terminal domain truncation mutant of US28, FLAG-US28/1-314, to investigate the role that this domain plays in US28 signaling. We demonstrate that US28/1-314 exhibits a more potent phospholipase C-β (PLC-β) signal than does wild-type US28, indicating that the carboxy-terminal domain plays an important role in regulating agonist-independent signaling in infected cells. Moreover, HMCV-infected cells expressing the US28/1-314 mutant exhibit a prolonged calcium signal in response to CCL5, indicating that the US28 carboxy-terminal domain also regulates agonist-dependent signaling. Finally, while the chemokine CX3CL1 behaves as an inverse agonist or inhibitor of constitutive US28 signaling to PLC-β, we demonstrate that CX3CL1 functions as an agonist with regard to US28-stimulated calcium release. This study is the first to demonstrate that the carboxy terminus of US28 controls US28 signaling in the context of HCMV infection and indicates that chemokines such as CX3CL1 can decrease constitutive US28 signals and yet simultaneously promote nonconstitutive US28 signals.
The Hepatitis C Virus Core Protein Contains a BH3 Domain That Regulates Apoptosis through Specific Interaction with Human Mcl-1
Authors: Mohd-Ismail Nur Khairiah , Deng Lin , Sukumaran Sunil Kumar , Yu Victor C. , Hotta Hak , Tan Yee-Joo
Published: July 2009

The hepatitis C virus (HCV) core protein is known to modulate apoptosis and contribute to viral replication and pathogenesis. In this study, we have identified a Bcl-2 homology 3 (BH3) domain in the core protein that is essential for its proapoptotic property. Coimmunoprecipitation experiments showed that the core protein interacts specifically with the human myeloid cell factor 1 (Mcl-1), a prosurvival member of the Bcl-2 family, but not with other prosurvival members (Bcl-X
L
and Bcl-w). Moreover, the overexpression of Mcl-1 protects against core-induced apoptosis. By using peptide mimetics, core was found to release cytochrome
c
from isolated mitochondria when complemented with Bad. Thus, core is a bona fide BH3-only protein having properties similar to those of Noxa, a BH3-only member of the Bcl-2 family that binds preferentially to Mcl-1. There are three critical hydrophobic residues in the BH3 domain of the core protein, and they are essential for the proapoptotic property of the core protein. Furthermore, the genotype 1b core protein is more effective than the genotype 2a core protein in inducing apoptosis due to a single-amino-acid difference at one of these hydrophobic residues (residue 119). Replacing this residue in the J6/JFH-1 infectious clone (genotype 2a) with the corresponding amino acid in the genotype 1b core protein produced a mutant virus, J6/JFH-1(V119L), which induced significantly higher levels of apoptosis in the infected cells than the parental J6/JFH-1 virus. Furthermore, the core protein of J6/JFH-1(V119L), but not that of J6/JFH-1, interacted with Mcl-1 in virus-infected cells. Taken together, the core protein is a novel BH3-only viral homologue that contributes to the induction of apoptosis during HCV infection.
Molecular Mechanism of BST2/Tetherin Downregulation by K5/MIR2 of Kaposi's Sarcoma-Associated Herpesvirus
Authors: Mansouri Mandana , Viswanathan Kasinath , Douglas Janet L. , Hines Jennie , Gustin Jean , Moses Ashlee V. , Früh Klaus
Published: July 2009

K3/MIR1 and K5/MIR2 of Kaposi's sarcoma-associated herpesvirus (KSHV) are viral members of the membrane-associated RING-CH (MARCH) ubiquitin ligase family and contribute to viral immune evasion by directing the conjugation of ubiquitin to immunostimulatory transmembrane proteins. In a quantitative proteomic screen for novel host cell proteins downregulated by viral immunomodulators, we previously observed that K5, as well as the human immunodeficiency virus type 1 (HIV-1) immunomodulator VPU, reduced steady-state levels of bone marrow stromal cell antigen 2 (BST2; also called CD317 or tetherin), suggesting that BST2 might be a novel substrate of K5 and VPU. Recent work revealed that in the absence of VPU, HIV-1 virions are tethered to the plasma membrane in BST2-expressing HeLa cells. By targeting BST2, K5 might thus similarly overcome an innate antiviral host defense mechanism. Here we establish that despite its type II transmembrane topology and carboxy-terminal glycosylphosphatidylinositol (GPI) anchor, BST2 represents a bona fide target of K5 that is downregulated during primary infection by and reactivation of KSHV. Upon exit of the protein from the endoplasmic reticulum, lysines in the short amino-terminal domain of BST2 are ubiquitinated by K5, resulting in rapid degradation of BST2. Ubiquitination of BST2 is required for degradation, since BST2 lacking cytosolic lysines was K5 resistant and ubiquitin depletion by proteasome inhibitors restored BST2 surface expression. Thus, BST2 represents the first type II transmembrane protein targeted by K5 and the first example of a protein that is both ubiquitinated and GPI linked. We further demonstrate that KSHV release is decreased in the absence of K5 in a BST2-dependent manner, suggesting that K5 contributes to the evasion of intracellular antiviral defense programs.
Selective-Advantage Profile of Human Immunodeficiency Virus Type 1 Integrase Mutants Explains In Vivo Evolution of Raltegravir Resistance Genotypes
Authors: Quercia Romina , Dam Elisabeth , Perez-Bercoff Danielle , Clavel François
Published: July 2009

The emergence of human immunodeficiency virus type 1 resistance to raltegravir, an integrase strand transfer inhibitor, follows distinct and independent genetic pathways, among which the N155H and Q148HKR pathways are the most frequently encountered in treated patients. After prolonged viral escape, mutants of the N155H pathway are replaced by mutants of the Q148HKR pathway. We have examined the mechanisms driving this evolutionary pattern using an approach that assesses the selective advantage of site-directed mutant viruses as a function of drug concentration. These selective-advantage curves revealed that among single mutants, N155H had the highest and the widest (1 to 500 nM) selective-advantage profile. Despite the higher 50% inhibitory concentration, Q148H displayed a lower and narrower (10 to 100 nM) selective-advantage profile. Among double mutants, the highest and widest selective-advantage profile was seen with G140S+Q148H. This finding likely explains why N155H can be selected early in the course of RAL resistance evolution in vivo but is later replaced by genotypes that include Q148HKR.
Interactions between Viral and Prokaryotic Pathogens in a Mixed Infection with Cardiovirus and Mycoplasma
Authors: Lidsky Peter V. , Romanova Lyudmila I. , Kolesnikova Marina S. , Bardina Maryana V. , Khitrina Elena V. , Hato Stanleyson V. , van Kuppeveld Frank J. M. , Agol Vadim I.
Published: July 2009

In the natural environment, animal and plant viruses often share ecological niches with microorganisms, but the interactions between these pathogens, although potentially having important implications, are poorly investigated. The present report demonstrates, in a model system, profound mutual effects of mycoplasma and cardioviruses in animal cell cultures. In contrast to mycoplasma-free cells, cultures contaminated with
Mycoplasma hyorhinis
responded to infection with encephalomyocarditis virus (EMCV), a picornavirus, but not with poliovirus (also a picornavirus), with a strong activation of a DNase(s), as evidenced by the TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) immunofluorescence assay and electrophoretic analysis of host DNA. This degradation was reminiscent of that observed upon apoptosis but was caspase independent, judging by the failure of the specific pan-caspase inhibitor Q-VD-OPh to prevent it. The electrophoretic mobility of the enzyme responsible for DNA degradation and dependence of its activity on ionic conditions strongly suggested that it was represented by a DNase(s) of mycoplasma origin. In cells not infected with EMCV, the relevant DNase was dormant. The possibility is discussed that activation of the mycoplasma DNase might be linked to a relatively early increase in permeability of plasma membrane of the infected cells caused by EMCV. This type of unanticipated virus-mycoplasma “cooperation” may exemplify the complexity of pathogen-host interactions under conditions when viruses and microorganisms are infecting the same host. In the course of the present study, it was also demonstrated that pan-caspase inhibitor zVAD(OMe).fmk strongly suppressed cardiovirus polyprotein processing, illustrating an additional pitfall in investigations of viral effects on the apoptotic system of host cells.
When the Guillain-Barré patient fails to respond to treatment: Figure
Authors: Winer J B
Published: July 2009

Most patients with Guillain-Barré syndrome (GBS) respond to treatment with intravenous immunoglobulin, but it is not uncommon for some to continue to deteriorate for a period after treatment has been started. This may reflect the natural history of the disease, or an error in diagnosis. This article reflects my own view of what to do in this situation, with a review of what few data there are to guide decision making.
Prevention and treatment of medical and neurological complications in patients with aneurysmal subarachnoid haemorrhage
Authors: Rinkel G J E , Klijn C J M
Published: July 2009

Treatment of patients with aneurysmal subarachnoid haemorrhage not only involves securing the aneurysm by endovascular coiling or surgical clipping but also prevention and treatment of the medical and neurological complications of the bleed. These acutely ill patients should be looked after in specialised centres by a multidisciplinary team that is available 24 h a day, 7 days a week. No medical intervention is known to improve outcome by reducing the risk of rebleeding but oral nimodipine should be standard care to prevent delayed cerebral ischaemia. For patients who develop delayed ischaemia, there is no evidence that hypervolaemia, haemodilution, hypertension, balloon angioplasty or intra-arterial vasodilating agents improve outcome. Lumbar puncture is a safe and reasonably effective way of treating those forms of acute hydrocephalus that are not caused by intraventricular obstruction.
INDUCED ELECTROSTATIC SELF-INTERACTION IN THE SPACE–TIME OF A GLOBAL MONOPOLE WITH INNER STRUCTURE
Authors: BARBOSA D. , BEZERRA DE MELLO E. R. , SPINELLY J.
Published: July 2009

In this work we analyze the electrostatic self-energy and self-force on a pointlike electric-charged particle induced by a global monopole space–time considering an inner structure for it. In order to develop this analysis we calculate the three-dimensional Green function associated with this physical system. We explicitly show that for points inside and outside the monopole's core the self-energy presents two distinct contributions. The first is induced by the geometry associated with the space–time under consideration, and the second is a correction due to the nonvanishing inner structure attributed to it. Considering specifically the ballpoint pen model for the region inside, we are able to obtain exact expressions for the self-energies in the regions outside and inside the monopole's core.
HIGH POTENTIAL GRADIENT OF Y2O3-DOPED THICK FILM VARISTORS
Authors: KE L. , JIANG D. M. , MA X. M.
Published: July 2009

The electrical and microstructural properties of a series of ZnO -based thick film varistors (TFVs) doped with 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10 mol% Y 2 O 3 were studied. It was found that sample doped with 0.08 mol% Y 2 O 3 showed the highest potential gradient of 3159.4 V/mm with a leakage current of 36.4 μA and a nonlinear exponent of 13.1. The ZnO grain size decreased with increasing Y 2 O 3 content, which was the origin for the increase in potential gradient. Raman spectra results showed that the tensile stress increased linearly with Y 2 O 3 doping. Larger tensile stress was considered to result from the lattice distortion and inevitably influenced the grain boundary characteristics. While the Y 2 O 3 doping concentration was beyond 0.08 mol%, the effect of residual stress on electrical properties was much more remarkable than that of grain size, leading potential gradient to be weakened. As a result, high potential gradient of ZnO -based TFVs could be obtained with Y 2 O 3 doping concentration of 0.08 mol% and qualified as excellent candidates for high voltage varistor application.
ADHESIVE WEAR AND FRICTIONAL BEHAVIOR OF MULTILAYERED POLYESTER COMPOSITE BASED ON BETELNUT FIBER MATS UNDER WET CONTACT CONDITIONS
Authors: YOUSIF B. F. , DEVADAS ALVIN , YUSAF TALAL F.
Published: July 2009

In the current study, a multilayered polyester composite based on betelnut fiber mats is fabricated. The adhesive wear and frictional performance of the composite was studied against a smooth stainless steel at different sliding distances (0–6.72 km) and applied loads (20–200 N) at 2.8 m/s sliding velocity. Variations in specific wear rate and friction coefficient were evaluated at two different orientations of fiber mat; namely parallel (P–O) and normal (N–O). Results obtained were presented against sliding distance. The worn surfaces of the composite were studied using an optical microscope. The effect of the composite sliding on the stainless steel counterface roughness was investigated. The results revealed that the wear performance of betelnut fiber reinforced polyester (BFRP) composite under wet contact condition was highly dependent on test parameters and fiber mat orientation. The specific wear rate performance for each orientation showed an inverse relationship to sliding distance. BFRP composite in N–O exhibited better wear performance compared with P–O. However, the friction coefficient in N–O was higher than that in P–O at lower range of applied load. The predominant wear mechanism was debonding of fiber with no pullout or ploughing. Moreover, at higher applied loads, micro- and macrocracking and fracture were observed in the resinous region.
EFFECT OF PULSE DUTY CYCLE ON PROPERTIES OF HARD NANOCRYSTALLINE SURFACE FABRICATED BY DUPLEX TREATMENTS
Authors: ALIOFKHAZRAEI M. , ROUHAGHDAM A. SABOUR
Published: July 2009

Up to fourth moment distribution of carbide nanocrystallites produced by duplex treatments of surface nanocrystallization and pulsed plasma electrolytic carbonitriding on AISI 1010 mild steel was investigated by the means of figure analysis with high precision. Skewness and kurtosis study of the Gaussian distribution have been studied and the effect of duty cycle of pulsed current has been determined. The usage of lower duty cycles of pulsed current is more suitable for achieving lower sizes of carbide nanocrystallites. Surface roughness of treated samples was measured and it has been observed that there is an optimum level of duty cycle of pulsed current for surface roughness increasing (difference between two measured data).
GUIDING OF O+ ION THROUGH Al2O3 NANOCAPILLARIES: DEPENDENCE ON CAPILLARY DIAMETER
Authors: CHEN YIFENG , CHEN XIMENG , LOU FENGJUN
Published: July 2009

The transmission of 60 keV O + ions through Al 2 O 3 nanocapillaries target in a series of different tilted angles was measured. The capillaries with diameters of 50 nm and 30 nm respectively, and 10 μm in length were used. Our results indicate the existence of guiding effect when ions through the capillary and a significant dependence of the ion transmission on the diameters of the capillaries.
Synthesis and spectral characterization of bis(β-diketonato)zirconium(IV) and -hafnium(IV) phthalocyaninates
Authors: Tomachynski L. A. , Chernii V. Ya. , Volkov S. V.
Published: July 2009

The reaction of PcMCl 2 ( M = Zr , Hf ) with β-diketones is reported. 1 H NMR and elemental analysis suggest the substitution of two Cl atoms for two β-diketone fragments takes place as a result of this reaction and the complexes PcM(β-dik)2 are formed. All obtained complexes are stable and highly soluble in most organic solvents. The data from 1 H and 19 F NMR, and UV-vis spectroscopy suggest the coordination of two β-diketone ligands in a cis geometry about the central atom of the macrocycle. It was shown bis(β-diketonato)zirconium(IV) and hafnium(IV) phthalocyanines containing β-diketones with donor or acceptor groups or with bulky substituents can be obtained.
A perspective on four new porphyrin-based functional materials and devices
Authors: Drain Charles Michael , Hupp Joeseph T. , Suslick Kenneth S. , Wasielewski Michael R. , Chen Xin
Published: July 2009

The tremendous potential for the manifold applications of porphyrins, porphyrazines, and phthalocyanines derives from their photophysical and electrochemical properties, their remarkable stability, and their predictable and rigid structure. These applications include nonlinear optics, catalysts, sensors, actuators, molecular sieves, and therapeutics. All of these properties are modulated by appending various chemical moieties onto the macrocycles, by choice of metallo derivative, and by the choice of environment. In multichromophoric systems, furthermore, the relative orientation of the chromophores, the nature of the linker, and the size of the system also dictate the properties. The synthesis of multichromophoric systems – both via covalent and noncovalent linkers – is driven by the desire to make new materials and to understand biological processes such as the various aspects of photosynthesis. Though electron and energy transfer processes continue to drive the synthesis of ever more complex systems, more recent focus has shifted toward other applications and functionalities of these structures. The focus of this perspective is on four recent developments in formation and characterization of functional, porphyrinic materials and devices: (1) self-assembly and self-organization of porphyrin arrays and aggregates into phototransistors and photonic devices; (2) self-assembled porphyrin squares for sensors, sieves, and catalysts; (3) covalently bound arrays of different chromophores as photonic materials; and (4) spatially separated arrays of metalloporphyrins as cross-reactive sensors.
Recent advances in the electrochemistry of porphyrins and phthalocyanines
Authors: D'Souza Francis
Published: July 2009

Recent developments in the electrochemistry of metalloporphyrins and metallophthalocyanines are reviewed briefly by focusing on the electroanalytical, electrocatalytic and electrochemical sensor applications.
Fabrication of Langmuir-Blodgett films of metallo- phthalocyanines by flow-orientation and dilution methods
Authors: Matsuura Toshihiko , Shimoyama Yuhei
Published: July 2009

This paper reports on novel fabrication techniques for well-ordered Langmuir (L) and Langmuir-Blodgett (LB) films of metallo tetra-tert-butyl phthalocyanines (MTBPcs) containing various transition metal ions, i.e. Co 2+, Cu 2+, Zn 2+ and VO 2+. An extreme dilute concentration of a developing solution releases the aggregation state of MTBPcs. Furthermore, the flow-orientation adjusts in-plane ordering of MTBPcs. Both procedures enable the fabrication of well-ordered L-monolayers of MTBPcs at the air-water interface. For the LB films prepared by the vertical dipping method, an annealing procedure dramatically improves the ordering of MTBPcs. Electron paramagnetic resonance spectroscopy also reveals that a spin-chain system in the MTBPc LB films possesses a two-dimensional order.
Meso-mesityl dithia- and diselenarubyrins: existence of planar and inverted forms in solution
Authors: Narayanan Seenichamy Jeyaprakash , Venkatraman Sundararaman , Anand Venkatara-manarao G. , Chandrashekar Tavarekere K.
Published: July 2009

Syntheses, characterization and spectroscopic studies of meso-mesityl substituted rubyrins are reported. Specifically, it has been shown that these rubyrins behave differently from the meso-phenyl containing rubyrins in their structure. 1 H NMR studies reveal the existence of both planar and inverted isomers in solution in different ratios both in the freebase and protonated forms.
Dynamic behavior and strategy for the complete 1H and 13C assignments for meso-aryl expanded heptaphyrins
Authors: Joshi Bhawani S. , Anand Venkataramanarao G. , Pushpan Simi K. , Srinivasan Alagar , Chandrashekar Tavarekere K. , Roy Raja
Published: July 2009

The detailed 1 H and 13 C NMR analysis of 5,10,19,24-tetramesityl-33,35,36,38,39-pentathiaheptaphyrin (1) and 5,10,19,24-tetraphenyl-35,36-dioxa-33,38,39-trithiaheptaphyrin (2) in the native and protonated state were carried out using two-dimensional NMR techniques. The analysis suggests that the earlier reported structure containing inverted terminal thiophene of trithiophene should be corrected as the inverted thiophene and furan of bithiophene and bifuran instead of trithiophene system of 1 and 2, respectively. Temperature dependent and titration studies suggest that 1 is less flexible in the native state then 2 due to presence of the mesityl group despite having disorder due to the presence of the heavier sulphur atom. This was consequently proven by the NMR information obtained in 5,10,19,24-tetramesityl-35,36-dioxa-33,38,39-trithiaheptaphyrin (3). Whereas in its protonated state, 2 was found to be less flexible than 1 due to presence of intramolecular hydrogen bonding involving N - H --- O between the pyrrole NH and oxygen of the furan of bifuran system. A systematic NMR strategy has been generated in order to provide complete a structure determination of expanded porphyrins along with their dynamic behavior.
Syntheses of regioselectively functionalized, asymmetric porphyrins via “2+2” condensation
Authors: Arumugam Nagarajan , Won Dong-Hoon , Lee Chang-Hee
Published: July 2009

Attachment of functional groups at the designated β-pyrrolic positions in asymmetrically substituted porphyrins is important in building customized model systems. We have developed a synthetic method of mono-functionalized dipyrromethanes at one of the β-pyrrolic positions. Synthesis of β-mono-brominated AB 2 C and ABCD type porphyrins was achieved by “2+2” condensation therefrom.
Investigation of a novel triazatetrabenzcorrole photosensitizer
Authors: Song Zhenglin , Zhang Fushi , Li Xue , Chan Shek-Kiu , Zhao Fuqun , Tang Yingwu
Published: July 2009

A novel phthalocyanine-like photosensitizer, oxophosphorus(V) tetrasulfotriaza-tetrabenzcorrole ( POTBCS 4), has been synthesized. Its structure and absorption spectrum are unique. POTBCS 4 has an axial P = O group and peripheral sulfo groups. The fluorescence emission spectra, fluorescence quantum yield and quantum yield of singlet oxygen generation have been studied. The uptake and the photodynamic activities against HeLa cells were measured. The results indicated that POTBCS 4 was a potential photosensitizer for photodynamic therapy (PDT).
Chlorophylldas the major photopigment inAcaryochloris marina
Authors: Chen Min , Quinnell Rosanne G. , Larkum Anthony W. D.
Published: July 2009

Chlorophyll (Chl) d is the major pigment in the photosystems (PS) and light-harvesting complex(es) of Acaryochloris marina. Chl a is present in small and variable amounts in PSII and in the light-harvesting complex(es). Isolated PSII complex showed a major fluorescence emission peak at 725 nm and a smaller emission peak due to Chl d at 701 nm, while the PSI complex showed two pools of Chl d, one with emission at 730 nm and the other at 709 nm at 77 K. In PSI and PSII of classical cyanobacteria and of higher plants, where Chl a is the predominant pigment rather than Chl d, these differences are not as pronounced. Light energy absorbed by phycobiliproteins was also active in these Chl d emissions. The major light-harvesting pigment protein is similar to the prochlorophyte Chl-binding protein (pcb) and had a major emission peak at 711 nm. In Cyanobacteria an iron-stress induced Chl-binding protein (isiA) forms a polymeric ring around PSI, and so the effect(s) of iron stress on A. marina where investigated. No clear evidence could be deduced for the formation of an isiA protein under iron stress and no clear changes in the proportion of Chl d :Chl a could be discerned although phycobilins showed a decreased under iron-stress conditions. That Chl d replaces Chl a in all its functions in A. marina is clear; the advantage of this evolutionary development appears to be to enable A. marina to absorb far-red light which occurs in environments where red light is filtered out by other photosynthetic organisms.
Synthesis of new singly metal-metal-bonded heterobinuclear complexes involving a porphyrin and a corrole: X-ray structure of the rhodium tetraphenylporphyrin-tin(2,3,7,13,17,18-hexamethyl-8,12-diethylcorrole) complex
Authors: Barbe Jean-Michel , Morata Gérald , Espinosa Enrique , Guilard Roger
Published: July 2009

The nucleophilic attack of a rhodium(I) porphyrin on a chlorotin(IV) corrole yields the heterobinuclear rhodium porphyrin-tin corrole complex where the two metals are bound via a single metal-metal bond. The X-ray structure of the rhodium tetraphenylporphyrin-tin(2,3,7,13,17,18-hexamethyl-8,12-diethylcorrole) complex is reported. The Rh-Sn single bond distance is equal to 2.5069(7) Å and the Rh and Sn atoms are located at 0.076 and 0.793 Å from the porphyrin and the corrole 4N mean planes, respectively.
Photodynamic anti-tumor activity of a new chlorin-based photosensitizer against Lewis Lung Carcinoma cells in vitro and in vivo
Authors: Lim Dae-Seog , Ko Si-Hwan , Won Dong-Hoon , Lee Chang-Hee , Lee Won-Young
Published: July 2009

A biological significance of photodynamic therapy (PDT) with a new porphyrin derivative, DH-I-180-3 (Max. Abs. 666 nm), was examined. Experimental PDT with DH-I-180-3 against Lewis Lung Carcinoma 1 (LLC1) cells was designed in vitro and in vivo. For the comparison, PDT with an established photosensitizer, Photofrin®, was done. When the cells were treated with DH-I-180-3 (1.0 μg/ml) in vitro, the cells became fatally susceptible to the light (1.2 J/cm2) as early as in 1 h. All of these cells were irreversibly damaged in 24 h after light irradiation and categorized as necrosis. These were not seen in cells treated with Photofrin® for more than 4 h and remained unharmed by the light until the end of experiments. Mice (C57BL/6J) bearing LLC1 tumor were treated (intravenously) with DH-I-180-3 (400 to 800 μg/kg) or with Photofrin® (2 mg/kg) for 4 h. Following the light irradiation (1.2 J/cm2), retarded tumor growth was significant in mice treated with DH-I-180-3 compared with those treated with Photofrin®/PDT. Survival of mice receiving DH-I-180-3/PDT was prolonged approximately 30% and 40% compared with that of mice in a Photofrin® group. In conclusion, DH-I-180-3 absorbs a longer light wavelength, and instantaneously accumulates in tumor cells to make them susceptible to the light. In mice, a significantly low dose of DH-I-180-3 as little as 400 μg/kg was sufficient to produce a successful PDT result. Thus, we conclude that DH-I-180-3 is an effective photosensitizer to be developed.
Some reactions of trimeric silicon phthalocyanine under alkaline conditions
Authors: Myakov Viktor N. , Kuropatov Vyacheslav A. , Lopatina Tatyana I. , Sedelnikova Valentina N.
Published: July 2009

The reaction of bis(trimethylsiloxy)triphthalocyaninatosilicon, Me 3 Si ( OSiPc )3 OSiMe 3 ( Pc 3) with KOH in o-xylene in the presence of 15-crown-5 in vacuum at 200°C has been studied by means of UV-vis, EPR and 1 H NMR spectroscopy. Upon gradual removal of H 2 O , the formation of mono- and dianions of Pc 3 with absorption bands positioned at 575-590 nm was observed. An EPR spectroscopic study revealed that both monoanionic and dianionic of Pc 3 are paramagnetic in solution. 1 H NMR spectra have shown the absence of a ring current in the π-electron system of dianion. The reaction of Pc 3 with KOH or metal Na led to degradation of the Si - O - Si - backbone happened.
Hierarchical self-assembly of a host-guest porphyrin array
Authors: Elemans Johannes A. A. W. , Nolte Roeland J. M. , Rowan Alan E.
Published: July 2009

The construction of a porphyrin array by a stepwise, hierarchical self-assembly process is described. Four molecular clip host molecules are complexed, in a solid state self-assembly process, to one porphyrin guest molecule. When dissolved in chloroform, the 4:1 host-guest complexes spontaneously self-assemble into an array in which the porphyrins are organized in a cofacial stack. The ensemble is stabilized by a combination of π-π interactions between the porphyrins and between the aromatic surfaces of the host molecules.
Second harmonic generation of a series of axially substituted titanium(IV) and gallium(III) tetra-tert-butylphthalocyanines
Authors: Claessens Christian G. , Gouloumis Andreas , Barthel Markus , Chen Yu , Martin Guillermo , Agulló-López Fernando , Ledoux-Rak Isabelle , Zyss Joseph , Hanack Michael , Torres Tomás
Published: July 2009

Electric Field Induced Second-Harmonic (EFISH) Generation and Hyper Raleigh Scattering (HRS) measurements were performed on a representative series of axially substituted titanium(IV) and gallium(III) tetra-tert-butylphthalocyanines. The comparison of γEFISH and βHRS values within the series and in particular in the case of the dimeric species shows the influence of both the reduction of symmetry of the phthalocyanine ring and the intramolecular stacking on the second order nonlinear optical properties.
New insights into the synthesis of porphyrin-corrole and biscorrole systems
Authors: Barbe Jean-Michel , Burdet Fabien , Espinosa Enrique , Gros Claude P. , Guilard Roger
Published: July 2009

As in the case of porphyrins, the relatively easier synthesis of meso-substituted corroles compared to that of β-pyrrole substituted ones greatly limits the use of these latter derivatives. Here we show, for the synthesis of β-substituted biscorrole and porphyrin-corrole dyads, that a simple replacement of sodium hydrogen carbonate by sodium acetate in the final cyclisation step of the a,c-biladiene to the corrole ring, increases the yield by at least a factor of 3. This reaction can be extended to the synthesis of β-substituted monocorroles. Moreover, when cobalt acetate is added instead of the reoxidation step, a 34 to 63% yield in porphyrin-spacer- Co ( III ) corrole is obtained, thus avoiding isolation of the free-base and further metalation of this latter derivative. This “cyclisation-oxidation-metalation” reaction is of particular interest in the preparation of heterobimetallic species in porphyrin-corrole series. Indeed, it leads to the formation of the monocobalt derivative with the cobalt atom inside the corrole moiety allowing for the further insertion of a large variety of metals into the porphyrin macrocycle. Crystals of the monocobalt complex of a biphenylene bridged porphyrin-corrole derivative were obtained in the presence of pyridine and the structure was determined by X-ray diffraction analysis. The structure shows that only one pyridine molecule is bound to the cobalt centre in an exo position, thus indicating a strong steric hindrance from the porphyrin counterpart.
Sandwich complexes of naphthalocyanine with the rare earth metals
Authors: Jiang Jianzhuang , Liu Wei , Arnold Dennis P.
Published: July 2009

Over the past two decades and in particular the past five years, numerous sandwich-type rare earth complexes containing naphthalocyanine ligands have been synthesized. The more extended delocalized π-electron system of naphthalocyanine in comparison with phthalocyanine generates unique physical, spectroscopic, electrochemical and photoelectrochemical properties which have aroused significant research interest in these compounds. This review summarizes recent progress in research on this important class of molecular materials and overviews the current status of the field.
Crystallosolvates ofZn(II)-tetra-tert-butylphthalocyanine with organic ligands: spectroscopic and thermogravimetric studies
Authors: Lebedeva Natalia Sh. , Pavlycheva Natalia A. , Parfenyuk Elena V. , Vyugin Anatoly I. , Malkova Elena A.
Published: July 2009

Molecular complexes of Zn (II)-tetra-tert-butylphthalocyanine ( Zn ( tert - Bu )4Pc ) with organic ligands (piperidine, morpholine, 1,4-dioxane) were obtained. The stoichiometry, energetic stability and decomposition temperature of the complexes were determined. The effect of specific solvation interactions with the organic solvents on the polymorphic state of Zn ( tert - Bu )4Pc was determined.
Synthesis of tetra(tricarbethoxy)- and tetra(dicarboxy)- substituted soluble phthalocyanines
Authors: Şener M. Kasim , Gül Ahmet , Koçak Makbule Burkut
Published: July 2009

Pd (II), Co (II), Cu (II) and Zn (II) phthalocyanines with a tricarbethoxyethyl substituent on each benzo group were prepared from 4-(1,1,2-tricarbethoxyethyl)-phthalonitrile and the corresponding divalent metal salt at 170°C. Transesterification occurred when the reaction was carried out in pentanol. Treatment of the palladium complex with sodium ethoxide at room temperature and further acidification resulted with tetra(1,2-dicarboxyethyl)phthalocyaninatopal-ladium. Its UV-vis spectrum in aqueous solution indicated dimeric and monomeric species at pH ≈ 12, but at pH ≈ 6 only the dimeric form were present.