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Sample records for calreticulin transacetylase catalyzed

  1. Calreticulin Transacetylase mediated activation of human platelet nitric oxide synthase by acetyl group donor compounds.

    PubMed

    Kumar, Ajit; Sushama, Anupam; Manral, Sushma; Sinha, Rajesh; Joshi, Rini; Singh, Usha; Rohil, Vishwajeet; Prasad, Ashok K; Parmar, Virinder S; Raj, Hanumantharao G

    2012-01-01

    Polyphenols have attracted immense interest because of their diverse biological and pharmacological activities. Surprisingly, not much is documented about the biological activities of acetoxy derivatives of polyphenol called polyphenolic acetates (PA). In our previous reports, we have conclusively established the Calreticulin Transacetylase (CRTAase) catalyzed activation of neuronal nitric oxide synthase (nNOS) and tumor necrosis factor-α (TNF-α) induced nitric oxide synthase (iNOS) by PA. In the present work, specificity of CRTAase to various classes of PA was characterized in human platelet. The effect of PA, on platelet NOS and intracellular cyclic guanosine monophosphate (cGMP), and adenosine diphosphate (ADP)-induced platelet aggregation were studied in an elaborated manner. Platelet CRTAase exhibited differential specificities to polyphenolic acetates upon incubation with l-arginine leading to activation of NOS. The intraplatelet generation of NO was studied by flowcytometry using DCFH-DA. The differential specificities of CRTAase to PA were found to positively correlate with increased production of NO upon incubation of PRP with PA and l-arginine. Further, the inhibitory effect of l-NAME on PA induced NO formation in platelets substantiated the CRTAase catalyzed activation of NOS. The real-time RT-PCR profile of NOS isoforms confirmed the preponderance of eNOS over iNOS in human platelets on treatment with PA. Western blot analysis also reiterated the differential pattern of acetylation of eNOS by PA. PA were also found effective in increasing the intraplatelet cGMP levels and inhibiting ADP-induced platelet aggregation. It is worth mentioning that the effects of PA were found to be in tune with the specificities of platelet CRTAase to PA as the substrates.

  2. Comparative specificities of Calreticulin Transacetylase to O-acetyl, N-acetyl and S-acetyl derivative of 4-methylcoumarins and their inhibitory effect on AFB1-induced genotoxicity in vitro and in vivo.

    PubMed

    Kumar, Ajit; Ponnan, Prija; Raj, Hanumantharao G; Parmar, Virinder S; Saso, Luciano

    2013-02-01

    We have earlier conclusively established the Calreticulin Transacetylase (CRTAase) catalyzed modifications of functional proteins such as cytochrome-P450-linked mixed function oxidases (Cyt-P450-linked MFOs), NADPH cytochrome c reductase, and glutathione S-transferase by acetoxy derivatives of polyphenols. In this study, we have investigated the comparative specificities of CRTAase to N-acetyl derivative, 7-acetamido-4-methylcoumarin (7-N-AMC), O-acetyl derivative, 7-acetoxy-4-methylcoumarin (7-AMC), S-acetyl derivative, 7-thioacetyl-4-methycoumarin (7-S-AMC) and their parent compounds in the modulation of catalytic activities of aforesaid proteins. Special attention concentrated on the comparative inhibitory effect of aforesaid acetyl moiety on Cyt-P450-linked MFOs such as 7-ethoxyresorufin O-deethylase (EROD), pentoxyresorufin O-dealkylase (PROD) and aflatoxin B(1) (AFB(1))-induced genotoxicity in vitro and in vivo. The results clearly indicated that N-acetyl and O-acetyl derivatives were better substrates for CRTAase while the S-acetyl was found to be a poorer substrate. Our study involving atomic charge, charge density and molecular electrostatic potential (MEP) calculations indicated the pivotal role of electronegativity and charge distribution values of O, N and S atoms of the acetyl group at C-7 position of the 4-methylcoumarins in CRTAase activity. These facts reinforce our hypothesis that the CRTAase catalyzed modifications of the catalytic activities of aforesaid proteins by acetyl derivative of 4-methylcoumarins is probably due to acetylation of these proteins.

  3. Calreticulin transacetylase mediated upregulation of thioredoxin by 7,8-diacetoxy-4-methylcoumarin enhances the antioxidant potential and the expression of vascular endothelial growth factor in peripheral blood mononuclear cells.

    PubMed

    Joshi, Rini; Kumar, Ajit; Manral, Sushma; Sinha, Rajesh; Arora, Shvetambri; Sharma, Anju; Goel, Sanjay; Kalra, Namita; Chatterji, Suvro; Dwarakanath, Bilikere S; Rawat, Diwan S; Depass, Anthony L; Rohil, Vishwajeet; Saluja, Daman; Parmar, Virinder S; Prasad, Ashok K; Raj, Hanumantharao G

    2013-11-25

    Extensive research carried out in our group on polyphenolic acetates (PAs) substantiated the potential role of PAs in causing diverse biological and pharmacological actions. Our earlier investigations firmly established the calreticulin transacetylase (CRTAase) catalyzed activation of nitric oxide synthase (NOS) by PAs. In this report, we have studied the effect of 7,8-diacetoxy-4-methylcoumarin (DAMC, a model PA) and other acetoxy coumarins on the thioredoxin and VEGF expression in human peripheral blood mononuclear cells (PBMCs), with a view to substantiate our earlier observation that DAMC was a superb inducer of angiogenesis. Real time RT-PCR analysis revealed the enhanced expression of thioredoxin reductase (TRXR) and diminished expression of thioredoxin interacting protein (TRXIP) leading to the increased expression and activity of thioredoxin (TRX) in PBMCs due to the the action of DAMC. The fact that TRX activity of PBMCs was enhanced by various acetoxy coumarins in tune with their affinity to CRTAase as substrate, suggested the possible activation of TRX due to acetylation. The overexpression of thioredoxin was found to correlate with that of VEGF as proved by real time RT-PCR and VEGF -ELISA results, apart from the DAMC-caused enhanced production of NO acting as an inducer of VEGF. Moreover, the intracellular ROS levels were also found to be reduced drastically, by DAMC thus reducing the oxidative stress in cells. These observations strongly evidenced the crucial role of TRX in DAMC-induced tissue angiogenesis with the involvement of VEGF.

  4. Emerging roles of calreticulin in cancer: implications for therapy.

    PubMed

    Venkateswaran, Kavya; Verma, Amit; Bhatt, Anant Narayan; Shrivastava, Anju; Manda, Kailash; Raj, Hanumantharao G; Prasad, Ashok; Len, Christophe; Parmar, Virinder S; Dwarakanath, Bilikere

    2017-01-11

    Calreticulin (CRT), initially identified as a ubiquitous calcium-binding protein in the endoplasmic reticulum, has emerged as a multifunctional protein with roles in calcium homeostasis, molecular chaperoning and cell adhesion. Emerging evidence suggests its involvement in tumorigenesis facilitating proliferation, migration, and adhesion. CRT translocated to the cell surface (ecto-CRT) serves as a phagocytic signal for immunogenic cell death (ICD) mediated through dendritic cells (DCs) and cytotoxic T-cell activation thereby making tumors susceptible to immunotherapy-based anti-cancer strategies. CRT is now regarded as one of the most potent danger-associated molecular patterns (DAMPs) with the ecto-CRT triggering restoration of homeostasis by immune stimulation. A recently identified novel transacetylase activity of CRT adds a new dimension to its multi-faceted involvement in cancer by virtue of polyphenolic acetates (PA): CRT transacetylase (CRTase) system which results in hyperacetylation of target proteins, thereby mimicking the effects of Histone deacetylase inhibitors (HDACi). Since protein acetylation is one of the crucial post-translational modifications (PTMs) influencing the epigenetic regulation and signal transduction, CRT can be a potential target for developing anticancer therapeutics and preventive strategies by employing pharmacologically compatible semi-synthetic acetyl donors like polyphenolic acetates and other agents.

  5. Calreticulin Mutations in Myeloproliferative Neoplasms

    PubMed Central

    Lavi, Noa

    2014-01-01

    With the discovery of the JAK2V617F mutation in patients with Philadelphia chromosome-negative (Ph−) myeloproliferative neoplasms (MPNs) in 2005, major advances have been made in the diagnosis of MPNs, in understanding of their pathogenesis involving the JAK/STAT pathway, and finally in the development of novel therapies targeting this pathway. Nevertheless, it remains unknown which mutations exist in approximately one-third of patients with non-mutated JAK2 or MPL essential thrombocythemia (ET) and primary myelofibrosis (PMF). At the end of 2013, two studies identified recurrent mutations in the gene encoding calreticulin (CALR) using whole-exome sequencing. These mutations were revealed in the majority of ET and PMF patients with non-mutated JAK2 or MPL but not in polycythemia vera patients. Somatic 52-bp deletions (type 1 mutations) and recurrent 5-bp insertions (type 2 mutations) in exon 9 of the CALR gene (the last exon encoding the C-terminal amino acids of the protein calreticulin) were detected and found always to generate frameshift mutations. All detected mutant calreticulin proteins shared a novel amino acid sequence at the C-terminal. Mutations in CALR are acquired early in the clonal history of the disease, and they cause activation of JAK/STAT signaling. The CALR mutations are the second most frequent mutations in Ph− MPN patients after the JAK2V617F mutation, and their detection has significantly improved the diagnostic approach for ET and PMF. The characteristics of the CALR mutations as well as their diagnostic, clinical, and pathogenesis implications are discussed in this review. PMID:25386351

  6. Regulation of Calreticulin Gene Expression by Calcium

    PubMed Central

    Waser, Mathilde; Mesaeli, Nasrin; Spencer, Charlotte; Michalak, Marek

    1997-01-01

    We have isolated and characterized a 12-kb mouse genomic DNA fragment containing the entire calreticulin gene and 2.14 kb of the promoter region. The mouse calreticulin gene consists of nine exons and eight introns, and it spans 4.2 kb of genomic DNA. A 1.8-kb fragment of the calreticulin promoter was subcloned into a reporter gene plasmid containing chloramphenicol acetyltransferase. This construct was then used in transient and stable transfection of NIH/ 3T3 cells. Treatment of transfected cells either with the Ca2+ ionophore A23187, or with the ER Ca2+-ATPase inhibitor thapsigargin, resulted in a five- to sevenfold increase of the expression of chloramphenicol acetyltransferase protein. Transactivation of the calreticulin promoter was also increased by fourfold in NIH/3T3 cells treated with bradykinin, a hormone that induces Ca2+ release from the intracellular Ca2+ stores. Analysis of the promoter deletion constructs revealed that A23187- and thapsigargin-responsive regions are confined to two regions (−115 to −260 and −685 to −1,763) in the calreticulin promoter that contain the CCAAT nucleotide sequences. Northern blot analysis of cells treated with A23187, or with thapsigargin, revealed a fivefold increase in calreticulin mRNA levels. Thapsigargin also induced a fourfold increase in calreticulun protein levels. Importantly, we show by nuclear run-on transcription analysis that calreticulin gene transcription is increased in NIH/3T3 cells treated with A23187 and thapsigargin in vivo. This increase in gene expression required over 4 h of continuous incubation with the drugs and was also sensitive to treatment with cycloheximide, suggesting that it is dependent on protein synthesis. Changes in the concentration of extracellular and cytoplasmic Ca2+ did not affect the increased expression of the calreticulin gene. These studies suggest that stress response to the depletion of intracellular Ca2+ stores induces expression of the calreticulin gene in vitro

  7. Calreticulin and Arginylated Calreticulin Have Different Susceptibilities to Proteasomal Degradation*

    PubMed Central

    Goitea, Victor E.; Hallak, Marta E.

    2015-01-01

    Post-translational arginylation has been suggested to target proteins for proteasomal degradation. The degradation mechanism for arginylated calreticulin (R-CRT) localized in the cytoplasm is unknown. To evaluate the effect of arginylation on CRT stability, we examined the metabolic fates and degradation mechanisms of cytoplasmic CRT and R-CRT in NIH 3T3 and CHO cells. Both CRT isoforms were found to be proteasomal substrates, but the half-life of R-CRT (2 h) was longer than that of cytoplasmic CRT (0.7 h). Arginylation was not required for proteasomal degradation of CRT, although R-CRT displays ubiquitin modification. A CRT mutant incapable of dimerization showed reduced metabolic stability of R-CRT, indicating that R-CRT dimerization may protect it from proteasomal degradation. Our findings, taken together, demonstrate a novel function of arginylation: increasing the half-life of CRT in cytoplasm. PMID:25969538

  8. Calreticulin: one protein, one gene, many functions.

    PubMed Central

    Michalak, M; Corbett, E F; Mesaeli, N; Nakamura, K; Opas, M

    1999-01-01

    The endoplasmic reticulum (ER) plays a critical role in the synthesis and chaperoning of membrane-associated and secreted proteins. The membrane is also an important site of Ca(2+) storage and release. Calreticulin is a unique ER luminal resident protein. The protein affects many cellular functions, both in the ER lumen and outside of the ER environment. In the ER lumen, calreticulin performs two major functions: chaperoning and regulation of Ca(2+) homoeostasis. Calreticulin is a highly versatile lectin-like chaperone, and it participates during the synthesis of a variety of molecules, including ion channels, surface receptors, integrins and transporters. The protein also affects intracellular Ca(2+) homoeostasis by modulation of ER Ca(2+) storage and transport. Studies on the cell biology of calreticulin revealed that the ER membrane is a very dynamic intracellular compartment affecting many aspects of cell physiology. PMID:10567207

  9. Role of Homoserine Transacetylase as a New Target for Antifungal Agents▿

    PubMed Central

    Nazi, Ishac; Scott, Adam; Sham, Anita; Rossi, Laura; Williamson, Peter R.; Kronstad, James W.; Wright, Gerard D.

    2007-01-01

    Microbial amino acid biosynthesis is a proven yet underexploited target of antibiotics. The biosynthesis of methionine in particular has been shown to be susceptible to small-molecule inhibition in fungi. The first committed step in Met biosynthesis is the acylation of homoserine (Hse) by the enzyme homoserine transacetylase (HTA). We have identified the MET2 gene of Cryptococcus neoformans H99 that encodes HTA (CnHTA) by complementation of an Escherichia coli metA mutant that lacks the gene encoding homoserine transsuccinylase (HTS). We cloned, expressed, and purified CnHTA and determined its steady-state kinetic parameters for the acetylation of L-Hse by acetyl coenzyme A. We next constructed a MET2 mutant in C. neoformans H99 and tested its growth behavior in Met-deficient media, confirming the expected Met auxotrophy. Furthermore, we used this mutant in a mouse inhalation model of infection and determined that MET2 is required for virulence. This makes fungal HTA a viable target for new antibiotic discovery. We screened a 1,000-compound library of small molecules for HTA inhibitors and report the identification of the first inhibitor of fungal HTA. This work validates HTA as an attractive drug-susceptible target for new antifungal agent design. PMID:17353245

  10. Calreticulin: Roles in Cell-Surface Protein Expression

    PubMed Central

    Jiang, Yue; Dey, Sandeepa; Matsunami, Hiroaki

    2014-01-01

    In order to perform their designated functions, proteins require precise subcellular localizations. For cell-surface proteins, such as receptors and channels, they are able to transduce signals only when properly targeted to the cell membrane. Calreticulin is a multi-functional chaperone protein involved in protein folding, maturation, and trafficking. However, evidence has been accumulating that calreticulin can also negatively regulate the surface expression of certain receptors and channels. In these instances, depletion of calreticulin enhances cell-surface expression and function. In this review, we discuss the role of calreticulin with a focus on its negative effects on the expression of cell-surface proteins. PMID:25230046

  11. Calnexin, calreticulin and the folding of glycoproteins.

    PubMed

    1997-05-01

    Calnexin and calreticulin are molecular chaperones in the endoplasmic reticulum (ERJ. They are lectins that interact with newly synthesized glycoproteins that have undergone partial trimming of their core N-linked oligosaccharides. Together with the enzymes responsible for glucose removal and a glucosyltransferase that re-glucosylates already-trimmed glycoproteins, they provide a novel mechanism for promoting folding, oligomeric assembly and quality control in the ER.

  12. The interactions of calreticulin with immunoglobulin G and immunoglobulin Y.

    PubMed

    Møllegaard, Karen Mai; Duus, Karen; Træholt, Sofie Dietz; Thaysen-Andersen, Morten; Liu, Yan; Palma, Angelina S; Feizi, Ten; Hansen, Paul R; Højrup, Peter; Houen, Gunnar

    2011-07-01

    Calreticulin is a chaperone of the endoplasmic reticulum (ER) assisting proteins in achieving the correctly folded structure. Details of the binding specificity of calreticulin are still a matter of debate. Calreticulin has been described as an oligosaccharide-binding chaperone but data are also accumulating in support of calreticulin as a polypeptide binding chaperone. In contrast to mammalian immunoglobulin G (IgG), which has complex type N-glycans, chicken immunoglobulin Y (IgY) possesses a monoglucosylated high mannose N-linked glycan, which is a ligand for calreticulin. Here, we have used solid and solution-phase assays to analyze the in vitro binding of calreticulin, purified from human placenta, to human IgG and chicken IgY in order to compare the interactions. In addition, peptides from the respective immunoglobulins were included to further probe the binding specificity of calreticulin. The experiments demonstrate the ability of calreticulin to bind to denatured forms of both IgG and IgY regardless of the glycosylation state of the proteins. Furthermore, calreticulin exhibits binding to peptides (glycosylated and non-glycosylated) derived from trypsin digestion of both immunoglobulins. Additionally, calreticulin peptide binding was examined with synthetic peptides covering the IgG Cγ2 domain demonstrating interaction with approximately half the peptides. Our results show that the dominant binding activity of calreticulin in vitro is toward the polypeptide moieties of IgG and IgY even in the presence of the monoglucosylated high mannose N-linked oligosaccharide on IgY.

  13. Cytoplasmic localization of the androgen receptor is independent of calreticulin

    PubMed Central

    Nguyen, Minh M.; Dincer, Zehra; Wade, James R.; Alur, Mahesh; Michalak, Marek; DeFranco, Donald B.; Wang, Zhou

    2009-01-01

    Identification and characterization of factors regulating intracellular localization of the androgen receptor (AR) are fundamentally important because nucleocytoplasmic trafficking of AR is a critical step in AR regulation by androgen manipulation. Normally, AR is localized to the cytoplasm in the absence of androgen. Upon ligand binding, AR translocates to the nucleus, where it can modulate transcription of AR-responsive genes. The withdrawal of androgen results in the export of unliganded AR from the nucleus to the cytoplasm, where it is transcriptionally inactive. Calreticulin has been implicated as a possible nuclear export factor for AR because the two proteins form a complex. In this study, we assessed whether the cytoplasmic localization of AR requires binding to calreticulin. To test this we substituted the calreticulin binding sequence (CBS) KVFFKR (residues 579–584) with the amino acids RLAARK in AR and monitored the cellular localization of a GFP-AR fusion protein in the absence of androgen. We also determined if knockdown or knockout of calreticulin expression affected the cytoplasmic localization of the AR. We found that a mutated CBS did not affect the localization of AR and that in the absence of androgen, AR is localized to the cytoplasm regardless of its ability to interact with calreticulin. Also, a reduction in the levels or loss of calreticulin did not affect the localization of AR. These data argue that calreticulin is not required for the cytoplasmic localization of AR. PMID:19150386

  14. Somatic mutations of calreticulin in myeloproliferative neoplasms.

    PubMed

    Klampfl, Thorsten; Gisslinger, Heinz; Harutyunyan, Ashot S; Nivarthi, Harini; Rumi, Elisa; Milosevic, Jelena D; Them, Nicole C C; Berg, Tiina; Gisslinger, Bettina; Pietra, Daniela; Chen, Doris; Vladimer, Gregory I; Bagienski, Klaudia; Milanesi, Chiara; Casetti, Ilaria Carola; Sant'Antonio, Emanuela; Ferretti, Virginia; Elena, Chiara; Schischlik, Fiorella; Cleary, Ciara; Six, Melanie; Schalling, Martin; Schönegger, Andreas; Bock, Christoph; Malcovati, Luca; Pascutto, Cristiana; Superti-Furga, Giulio; Cazzola, Mario; Kralovics, Robert

    2013-12-19

    Approximately 50 to 60% of patients with essential thrombocythemia or primary myelofibrosis carry a mutation in the Janus kinase 2 gene (JAK2), and an additional 5 to 10% have activating mutations in the thrombopoietin receptor gene (MPL). So far, no specific molecular marker has been identified in the remaining 30 to 45% of patients. We performed whole-exome sequencing to identify somatically acquired mutations in six patients who had primary myelofibrosis without mutations in JAK2 or MPL. Resequencing of CALR, encoding calreticulin, was then performed in cohorts of patients with myeloid neoplasms. Somatic insertions or deletions in exon 9 of CALR were detected in all patients who underwent whole-exome sequencing. Resequencing in 1107 samples from patients with myeloproliferative neoplasms showed that CALR mutations were absent in polycythemia vera. In essential thrombocythemia and primary myelofibrosis, CALR mutations and JAK2 and MPL mutations were mutually exclusive. Among patients with essential thrombocythemia or primary myelofibrosis with nonmutated JAK2 or MPL, CALR mutations were detected in 67% of those with essential thrombocythemia and 88% of those with primary myelofibrosis. A total of 36 types of insertions or deletions were identified that all cause a frameshift to the same alternative reading frame and generate a novel C-terminal peptide in the mutant calreticulin. Overexpression of the most frequent CALR deletion caused cytokine-independent growth in vitro owing to the activation of signal transducer and activator of transcription 5 (STAT5) by means of an unknown mechanism. Patients with mutated CALR had a lower risk of thrombosis and longer overall survival than patients with mutated JAK2. Most patients with essential thrombocythemia or primary myelofibrosis that was not associated with a JAK2 or MPL alteration carried a somatic mutation in CALR. The clinical course in these patients was more indolent than that in patients with the JAK2 V617F

  15. Calreticulin Is a Receptor for Nuclear Export

    PubMed Central

    Holaska, James M.; Black, Ben E.; Love, Dona C.; Hanover, John A.; Leszyk, John; Paschal, Bryce M.

    2001-01-01

    In previous work, we used a permeabilized cell assay that reconstitutes nuclear export of protein kinase inhibitor (PKI) to show that cytosol contains an export activity that is distinct from Crm1 (Holaska, J.M., and B.M. Paschal. 1995. Proc. Natl. Acad. Sci. USA. 95: 14739–14744). Here, we describe the purification and characterization of the activity as calreticulin (CRT), a protein previously ascribed to functions in the lumen of the ER. We show that cells contain both ER and cytosolic pools of CRT. The mechanism of CRT-dependent export of PKI requires a functional nuclear export signal (NES) in PKI and involves formation of an export complex that contains RanGTP. Previous studies linking CRT to downregulation of steroid hormone receptor function led us to examine its potential role in nuclear export of the glucocorticoid receptor (GR). We found that CRT mediates nuclear export of GR in permeabilized cell, microinjection, and transfection assays. GR export is insensitive to the Crm1 inhibitor leptomycin B in vivo, and it does not rely on a leucine-rich NES. Rather, GR export is facilitated by its DNA-binding domain, which is shown to function as an NES when transplanted to a green fluorescent protein reporter. CRT defines a new export pathway that may regulate the transcriptional activity of steroid hormone receptors. PMID:11149926

  16. Calreticulin Exon 9 Mutations in Myeloproliferative Neoplasms

    PubMed Central

    Kim, Yu-Kyung

    2015-01-01

    Background Calreticulin (CALR) mutations were recently discovered in patients with myeloproliferative neoplasms (MPNs). We studied the frequency and type of CALR mutations and their hematological characteristics. Methods A total of 168 MPN patients (36 polycythemia vera [PV], 114 essential thrombocythemia [ET], and 18 primary myelofibrosis [PMF] cases) were included in the study. CALR mutation was analyzed by the direct sequencing method. Results CALR mutations were detected in 21.9% of ET and 16.7% of PMF patients, which accounted for 58.5% and 33.3% of ET and PMF patients without Janus kinase 2 (JAK2) or myeloproliferative leukemia virus oncogenes (MPL) mutations, respectively. A total of five types of mutation were detected, among which, L367fs*46 (53.6%) and K385fs*47 (35.7%) were found to be the most common. ET patients with CALR mutation had lower leukocyte counts and ages compared with JAK2-mutated ET patients. Conclusion Genotyping for CALR could be a useful diagnostic tool for JAK2-or MPL-negative ET or PMF patients. CALR mutation may be a distinct disease group, with different hematological characteristics than that of JAK2-positive patients. PMID:25553276

  17. Mapping the Ca(2+) induced structural change in calreticulin.

    PubMed

    Boelt, Sanne Grundvad; Norn, Christoffer; Rasmussen, Morten Ib; André, Ingemar; Čiplys, Evaldas; Slibinskas, Rimantas; Houen, Gunnar; Højrup, Peter

    2016-06-16

    Calreticulin is a highly conserved multifunctional protein implicated in many different biological systems and has therefore been the subject of intensive research. It is primarily present in the endoplasmatic reticulum where its main functions are to regulate Ca(2+) homeostasis, act as a chaperone and stabilize the MHC class I peptide-loading complex. Although several high-resolution structures of calreticulin exist, these only cover three-quarters of the entire protein leaving the extended structures unsolved. Additionally, the structure of calreticulin is influenced by the presence of Ca(2+). The conformational changes induced by Ca(2+) have not been determined yet as they are hard to study with traditional approaches. Here, we investigated the Ca(2+)-induced conformational changes with a combination of chemical cross-linking, mass spectrometry, bioinformatics analysis and modelling in Rosetta. Using a bifunctional linker, we found a large Ca(2+)-induced change to the cross-linking pattern in calreticulin. Our results are consistent with a high flexibility in the P-loop, a stabilization of the acidic C-terminal and a relatively close interaction of the P-loop and the acidic C-terminal. The function of calreticulin, an endoplasmatic reticulin chaperone, is affected by fluctuations in Ca(2+)concentration, but the structural mechanism is unknown. The present work suggests that Ca(2+)-dependent regulation is caused by different conformations of a long proline-rich loop that changes the accessibility to the peptide/lectin-binding site. Our results indicate that the binding of Ca(2+) to calreticulin may thus not only just be a question of Ca(2+) storage but is likely to have an impact on the chaperone activity. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. lac operon induction in Escherichia coli: Systematic comparison of IPTG and TMG induction and influence of the transacetylase LacA.

    PubMed

    Marbach, Anja; Bettenbrock, Katja

    2012-01-01

    Most commonly used expression systems in bacteria are based on the Escherichia coli lac promoter. Furthermore, lac operon elements are used today in systems and synthetic biology. In the majority of the cases the gratuitous inducers IPTG or TMG are used. Here we report a systematic comparison of lac promoter induction by TMG and IPTG which focuses on the aspects inducer uptake, population heterogeneity and a potential influence of the transacetylase, LacA. We provide induction curves in E. coli LJ110 and in isogenic lacY and lacA mutant strains and we show that both inducers are substrates of the lactose permease at low inducer concentrations but can also enter cells independently of lactose permease if present at higher concentrations. Using a gfp reporter strain we compared TMG and IPTG induction at single cell level and showed that bimodal induction with IPTG occurred at approximately ten-fold lower concentrations than with TMG. Furthermore, we observed that lac operon induction is influenced by the transacetylase, LacA. By comparing two Plac-gfp reporter strains with and without a lacA deletion we could show that in the lacA(+) strain the fluorescence level decreased after few hours while the fluorescence further increased in the lacA(-) strain. The results indicate that through the activity of LacA the IPTG concentration can be reduced below an inducing threshold concentration-an influence that should be considered if low inducer amounts are used.

  19. Calreticulin (CALR) mutation in myeloproliferative neoplasms (MPNs)

    PubMed Central

    Luo, Wenyi

    2015-01-01

    As a heterogeneous group of disease, myeloproliferative neoplasms (MPNs) have confused hematologists and hematopathologists with their protean clinical presentations and myriads of morphologies. A thought of classifying MPNs based on molecular alterations has gained popularity because there is increasing evidence that molecular or chromosomal alterations have a better correlation with clinical presentation, response to therapies, and prognosis than conventional morphological classification. This type of efforts has been facilitated by the advancement of molecular technologies. A significant number of gene mutations have been identified in MPNs with JAK2 and MPL being the major ones. However, a significant gap is present in that many cases of MPNs do not harbor any of these mutations. This gap is recently filled by the discovery of Calreticulin (CALR) mutation in MPNs without JAK2 or MPL mutation and since then, the clinical and molecular correlation in MPNs has become a hot research topic. There seems to be a fairly consistent correlation between CALR mutation and certain hematological parameters such as a high platelet count and a better prognosis in MPNs with CALR mutation. However, controversies are present regarding the risks of thrombosis, interactions of CALR with other gene mutation, the role of CALR in the pathogenesis, and the optimal treatment strategies. In addition, there are many questions remain to be answered, which all boiled down to the molecular mechanisms by which CALR causes or contributes to MPNs. Here, we summarized current published literatures on CALR mutations in MPNs with an emphasis on the clinical-molecular correlation. We also discussed the controversies and questions remain to be answered. PMID:27358884

  20. Comparison of protein acetyltransferase action of CRTAase with the prototypes of HAT.

    PubMed

    Ponnan, Prija; Kumar, Ajit; Singh, Prabhjot; Gupta, Prachi; Joshi, Rini; Gaspari, Marco; Saso, Luciano; Prasad, Ashok K; Rastogi, Ramesh C; Parmar, Virinder S; Raj, Hanumantharao G

    2014-01-01

    Our laboratory is credited for the discovery of enzymatic acetylation of protein, a phenomenon unknown till we identified an enzyme termed acetoxy drug: protein transacetylase (TAase), catalyzing the transfer of acetyl group from polyphenolic acetates to receptor proteins (RP). Later, TAase was identified as calreticulin (CR), an endoplasmic reticulum luminal protein. CR was termed calreticulin transacetylase (CRTAase). Our persistent study revealed that CR like other families of histone acetyltransferases (HATs) such as p300, Rtt109, PCAF, and ESA1, undergoes autoacetylation. The autoacetylated CR was characterized as a stable intermediate in CRTAase catalyzed protein acetylation, and similar was the case with ESA1. The autoacetylation of CR like that of HATs was found to enhance protein-protein interaction. CR like HAT-1, CBP, and p300 mediated the acylation of RP utilizing acetyl CoA and propionyl CoA as the substrates. The similarities between CRTAase and HATs in mediating protein acylation are highlighted in this review.

  1. Calreticulin Is a Thermostable Protein with Distinct Structural Responses to Different Divalent Cation Environments*

    PubMed Central

    Wijeyesakere, Sanjeeva J.; Gafni, Ari A.; Raghavan, Malini

    2011-01-01

    Calreticulin is a soluble calcium-binding chaperone of the endoplasmic reticulum (ER) that is also detected on the cell surface and in the cytosol. Calreticulin contains a single high affinity calcium-binding site within a globular domain and multiple low affinity sites within a C-terminal acidic region. We show that the secondary structure of calreticulin is remarkably thermostable at a given calcium concentration. Rather than corresponding to complete unfolding events, heat-induced structural transitions observed for calreticulin relate to tertiary structural changes that expose hydrophobic residues and reduce protein rigidity. The thermostability and the overall secondary structure content of calreticulin are impacted by the divalent cation environment, with the ER range of calcium concentrations enhancing stability, and calcium-depleting or high calcium environments reducing stability. Furthermore, magnesium competes with calcium for binding to calreticulin and reduces thermostability. The acidic domain of calreticulin is an important mediator of calcium-dependent changes in secondary structure content and thermostability. Together, these studies indicate interactions between the globular and acidic domains of calreticulin that are impacted by divalent cations. These interactions influence the structure and stability of calreticulin, and are likely to determine the multiple functional activities of calreticulin in different subcellular environments. PMID:21177861

  2. Evidence for calreticulin attenuation of cardiac hypertrophy induced by pressure overload and soluble agonists.

    PubMed

    Papp, Sylvia; Dziak, Ewa; Kabir, Golam; Backx, Peter; Clement, Sophie; Opas, Michal

    2010-03-01

    While calreticulin has been shown to be critical for cardiac development, its role in cardiac pathology is unclear. Previous studies have shown the detrimental effects on the heart of sustained germline calreticulin overexpression, yet without calreticulin, the heart does not develop normally. Thus, carefully balanced calreticulin levels are required for the heart to develop and to function properly into adulthood. But what happens to calreticulin levels, and how is this regulated, during cardiac hypertrophy, during which the fetal gene program is reactivated, at least partially? Our working hypothesis was that c-Src, a kinase whose activity we previously found to be correlated with calreticulin expression, was involved with calreticulin in regulating the response to hypertrophic signals. Thus, we subjected adult mice to transverse aortic constriction to induce left ventricular hypertrophy. We found that aortic constriction caused calreticulin levels to increase, whereas those of c-Src fell with longer constriction time. We also examined the ability of embryonic stem cell-derived cardiomyocytes to respond to soluble hypertrophic agonists. Endothelin-1 treatment caused a significantly greater cell area increase of calreticulin-null cardiomyocytes, which had higher c-Src activity, compared with wild-type cells. c-Src inhibition abolished this difference. Greater c-Src activity may explain the efficacy with which calreticulin-null cells are able to induce the hypertrophic program, while cells containing calreticulin may be able to attenuate the hypertrophic response as a result of decreased c-Src activity. Thus, calreticulin may have a protective effect on the heart in the face of cardiac hypertrophy.

  3. Evidence for Calreticulin Attenuation of Cardiac Hypertrophy Induced by Pressure Overload and Soluble Agonists

    PubMed Central

    Papp, Sylvia; Dziak, Ewa; Kabir, Golam; Backx, Peter; Clement, Sophie; Opas, Michal

    2010-01-01

    While calreticulin has been shown to be critical for cardiac development, its role in cardiac pathology is unclear. Previous studies have shown the detrimental effects on the heart of sustained germline calreticulin overexpression, yet without calreticulin, the heart does not develop normally. Thus, carefully balanced calreticulin levels are required for the heart to develop and to function properly into adulthood. But what happens to calreticulin levels, and how is this regulated, during cardiac hypertrophy, during which the fetal gene program is reactivated, at least partially? Our working hypothesis was that c-Src, a kinase whose activity we previously found to be correlated with calreticulin expression, was involved with calreticulin in regulating the response to hypertrophic signals. Thus, we subjected adult mice to transverse aortic constriction to induce left ventricular hypertrophy. We found that aortic constriction caused calreticulin levels to increase, whereas those of c-Src fell with longer constriction time. We also examined the ability of embryonic stem cell-derived cardiomyocytes to respond to soluble hypertrophic agonists. Endothelin-1 treatment caused a significantly greater cell area increase of calreticulin-null cardiomyocytes, which had higher c-Src activity, compared with wild-type cells. c-Src inhibition abolished this difference. Greater c-Src activity may explain the efficacy with which calreticulin-null cells are able to induce the hypertrophic program, while cells containing calreticulin may be able to attenuate the hypertrophic response as a result of decreased c-Src activity. Thus, calreticulin may have a protective effect on the heart in the face of cardiac hypertrophy. PMID:20110410

  4. Nerve growth factor induces the expression of chaperone protein calreticulin in human epithelial ovarian cells.

    PubMed

    Vera, C; Tapia, V; Kohan, K; Gabler, F; Ferreira, A; Selman, A; Vega, M; Romero, C

    2012-07-01

    Epithelial ovarian cancer is highly angiogenic and high expression of Nerve Growth Factor (NGF), a proangiogenic protein. Calreticulin is a multifunctional protein with anti-angiogenic properties and its translocation to the tumor cell membrane promotes recognition and engulfment by dendritic cells. The aim of this work was to evaluate calreticulin expression in human normal ovaries, benign and borderline tumors, and epithelial ovarian cancer samples and to evaluate whether NGF regulates calreticulin expression in human ovarian surface epithelium and in epithelial ovarian cancer cell lines. Calreticulin mRNA and protein levels were analyzed using RT-PCR, Western blot and immunohistochemistry in 67 human ovarian samples obtained from our Institution. Calreticulin expression induced by NGF stimulation in cell lines was evaluated using RT-PCR, Western blot and immunocytochemistry. We found a significant increase of calreticulin mRNA levels in epithelial ovarian cancer samples as compared to normal ovaries, benign tumors, and borderline tumors. Calreticulin protein levels, evaluated by Western blot, were also increased in epithelial ovarian cancer with respect to benign and borderline tumors. When HOSE and A2780 cell lines were stimulated with Nerve Growth Factor, we found an increase in calreticulin protein levels compared to controls. This effect was reverted by GW441756, a TRKA specific inhibitor. These results suggest that NGF regulates calreticulin protein levels in epithelial ovarian cells through TRKA receptor activation. © Georg Thieme Verlag KG Stuttgart · New York.

  5. The evolutionary history of calreticulin and calnexin genes in green plants.

    PubMed

    Del Bem, Luiz Eduardo V

    2011-02-01

    Calreticulin and calnexin are Ca(2+)-binding chaperones localized in the endoplasmic reticulum of eukaryotes acting in glycoprotein folding quality control and Ca(2+) homeostasis. The evolutionary histories of calreticulin and calnexin gene families were inferred by comprehensive phylogenetic analyses using 18 completed genomes and ESTs covering the major green plants groups, from green algae to angiosperms. Calreticulin and calnexin possibly share a common origin, and both proteins are present along all green plants lineages. The calreticulin founder gene within green plants duplicated in early tracheophytes leading to two possible groups of orthologs with specialized functions, followed by lineage-specific gene duplications in spermatophytes. Calnexin founder gene in land plants was inherited from basal green algae during evolution in a very conservative copy number. A comprehensive classification in possible groups of orthologs and a catalog of calreticulin and calnexin genes from green plants are provided.

  6. Differential expression of calreticulin in developmental stages of Taenia solium.

    PubMed

    Mendlovic, Fela; Carrillo-Farga, Joaquín; Torres, José; Laclette, Juan Pedro; Flisser, Ana

    2006-08-01

    Taenia solium, a cestode that causes neurocysticercosis and taeniasis in humans, has a complex life cycle. The adult tapeworm develops in the intestine of human beings and is also responsible for neurocysticercosis, which is caused by the metacestode or cysticercus that develops in the brain. Recently, we have cloned the coding region for T. solium calreticulin (TsCRT) as a functional Ca(2+)-binding protein. Calreticulin is a ubiquitous protein involved in cellular Ca2+ homeostasis and protein folding. These important functions affect several aspects of cell physiology. To explore the expression of TsCRT during the T. solium life cycle, we used a specific polyclonal antibody raised against recombinant TsCRT to localize this protein by immunolabeling techniques. In sections of cysticerci obtained from swine muscle, as well as of adult tapeworms obtained after infection of hamsters with cysticerci, TsCRT was preferentially localized in tegumentary and muscle cytons of the suckers and rostellum. In mature proglottids obtained from infected humans, positive staining was observed in spermatogonia, ovogonia, uterine epithelium, and cells of the vas deferens. In the gravid uterus, the morula and early stage embryos were highly positive to TsCRT. However, expression diminished as embryonic development progressed and was absent in fully developed oncospheres that were surrounded by an embryophore. A similar down regulation was observed during spermatogenesis. Although early spermatocytes showed a high expression of TsCRT, mature spermatozoa present in the vas deferens were completely negative. These data indicate that calreticulin expression is spatially and temporally regulated during development of T. solium, especially during germ cell development and embryogenesis. In addition, these original images illustrate, for the first time, these processes at a histological level.

  7. Serum Calreticulin Is a Negative Biomarker in Patients with Alzheimer’s Disease

    PubMed Central

    Lin, Qiao; Cao, Yunpeng; Gao, Jie

    2014-01-01

    Calreticulin is down-regulated in the cortical neurons of patients with Alzheimer’s disease (AD) and may be a potential biomarker for the diagnosis of AD. A total of 128 AD patients were randomly recruited from May 2012 to July 2013. The mRNA levels of calreticulin were measured from the serum of tested subjects using real-time quantitative reverse transcriptase-PCR (real-time qRT-PCR). Serum levels of calreticulin were determined by ELISA and Western Blot. Serum levels of calreticulin in AD patients were significantly lower than those from a healthy group (p < 0.01). The baseline characters indicated that sample size, gender, mean age, diabetes and BMI (body mass index) were not major sources of heterogeneity. The serum levels of mRNA and protein of calreticulin were lower in AD patients than those from a healthy group, and negatively associated with the progression of AD according to CDR scores (p < 0.01). Thus, there is a trend toward decreased serum levels of calreticulin in the patients with progression of AD. Serum levels of calreticulin can be a negative biomarker for the diagnosis of AD patients. PMID:25429433

  8. Serum calreticulin is a negative biomarker in patients with Alzheimer's disease.

    PubMed

    Lin, Qiao; Cao, Yunpeng; Gao, Jie

    2014-11-25

    Calreticulin is down-regulated in the cortical neurons of patients with Alzheimer's disease (AD) and may be a potential biomarker for the diagnosis of AD. A total of 128 AD patients were randomly recruited from May 2012 to July 2013. The mRNA levels of calreticulin were measured from the serum of tested subjects using real-time quantitative reverse transcriptase-PCR (real-time qRT-PCR). Serum levels of calreticulin were determined by ELISA and Western Blot. Serum levels of calreticulin in AD patients were significantly lower than those from a healthy group (p < 0.01). The baseline characters indicated that sample size, gender, mean age, diabetes and BMI (body mass index) were not major sources of heterogeneity. The serum levels of mRNA and protein of calreticulin were lower in AD patients than those from a healthy group, and negatively associated with the progression of AD according to CDR scores (p < 0.01). Thus, there is a trend toward decreased serum levels of calreticulin in the patients with progression of AD. Serum levels of calreticulin can be a negative biomarker for the diagnosis of AD patients.

  9. Calreticulin mutation-specific immunostaining in myeloproliferative neoplasms: pathogenetic insight and diagnostic value

    PubMed Central

    Vannucchi, A M; Rotunno, G; Bartalucci, N; Raugei, G; Carrai, V; Balliu, M; Mannarelli, C; Pacilli, A; Calabresi, L; Fjerza, R; Pieri, L; Bosi, A; Manfredini, R; Guglielmelli, P

    2014-01-01

    Mutations in the gene calreticulin (CALR) occur in the majority of JAK2- and MPL-unmutated patients with essential thrombocythemia (ET) and primary myelofibrosis (PMF); identifying CALR mutations contributes to the diagnostic pathway of ET and PMF. CALR mutations are heterogeneous spanning over the exon 9, but all result in a novel common protein C terminus. We developed a polyclonal antibody against a 17-amino-acid peptide derived from mutated calreticulin that was used for immunostaining of bone marrow biopsies. We show that this antibody specifically recognized patients harboring different types of CALR mutation with no staining in healthy controls and JAK2- or MPL-mutated ET and PMF. The labeling was mostly localized in megakaryocytes, whereas myeloid and erythroid cells showed faint staining, suggesting a preferential expression of calreticulin in megakaryocytes. Megakaryocytic-restricted expression of calreticulin was also demonstrated using an antibody against wild-type calreticulin and by measuring the levels of calreticulin RNA by gene expression analysis. Immunostaining using an antibody specific for mutated calreticulin may become a rapid, simple and cost-effective method for identifying CALR-mutated patients complementing molecular analysis; furthermore, the labeling pattern supports the preferential expansion of megakaryocytic cell lineage as a result of CALR mutation in an immature hematopoietic stem cell. PMID:24618731

  10. Glycan-dependent and -independent Interactions Contribute to Cellular Substrate Recruitment by Calreticulin*

    PubMed Central

    Wijeyesakere, Sanjeeva J.; Rizvi, Syed M.; Raghavan, Malini

    2013-01-01

    Calreticulin is an endoplasmic reticulum chaperone with specificity for monoglucosylated glycoproteins. Calreticulin also inhibits precipitation of nonglycosylated proteins and thus contains generic protein-binding sites, but their location and contributions to substrate folding are unknown. We show that calreticulin binds glycosylated and nonglycosylated proteins with similar affinities but distinct interaction kinetics. Although both interactions involve the glycan-binding site or its vicinity, the arm-like proline-rich (P-) domain of calreticulin contributes to binding non/deglycosylated proteins. Correspondingly, ensemble FRET spectroscopy measurements indicate that glycosylated and nonglycosylated proteins induce “open” and “closed” P-domain conformations, respectively. The co-chaperone ERp57 influences substrate-binding kinetics and induces a closed P-domain conformation. Together with analysis of the interactions of calreticulin with cellular proteins, these findings indicate that the recruitment of monoglucosylated proteins to calreticulin is kinetically driven, whereas the P-domain and co-chaperone contribute to stable substrate binding. Substrate sequestration in the cleft between the glycan-binding site and P-domain is a likely mechanism for calreticulin-assisted protein folding. PMID:24100026

  11. Tc45, a dimorphic Trypanosoma cruzi immunogen with variable chromosomal localization, is calreticulin.

    PubMed

    Aguillón, J C; Ferreira, L; Pérez, C; Colombo, A; Molina, M C; Wallace, A; Solari, A; Carvallo, P; Galindo, M; Galanti, N; Orn, A; Billetta, R; Ferreira, A

    2000-01-01

    We demonstrate that Tc45, a polypeptide described as an immunogenetically restricted Trypanosoma cruzi antigen in mice, is calreticulin, a dimorphic molecule encoded by genes with variable chromosomal distribution. Previously we showed that IgG from A.SW (H2s) mice immunized with T. cruzi trypomastigotes or epimastigotes and sera from infected humans recognize Tc45, a 45 kD parasite polypeptide. Herein we describe the cloning, sequencing, and expression of the Tc45 gene. A 98% homology in the deduced amino acid sequence was found with a T. cruzi calreticulin-like molecule and 41% with Leishmania donovani and human calreticulin. In the T. cruzi CL Brener clone and in the Tulahuén strain, the gene is located in two and four chromosomes, respectively. Calreticulin was detected in several T. cruzi clones, in the Tulahuén strain, and in T. rangeli, displaying alternative 43 and 46 kD forms.

  12. The Endoplasmic Reticulum Stress Protein Calreticulin in Diabetic Chronic Kidney Disease

    DTIC Science & Technology

    2015-07-01

    1 AWARD NUMBER: W81XWH-14-1-0203 TITLE: The Endoplasmic Reticulum Stress Protein Calreticulin in Diabetic Chronic Kidney Disease PRINCIPAL...COVERED 07/01/2014-06/30/2015 4. TITLE AND SUBTITLE The Endoplasmic Reticulum Stress Protein Calreticulin in Diabetic Chronic Kidney Disease 5a...NUMBER(S) 13. SUPPLEMENTARY NOTES 14. ABSTRACT We hypothesize that ER stress induced by glucose in diabetes promotes diabetic CKD through CRT stimulation

  13. The Endoplasmic Reticulum Stress Protein Calreticulin in Diabetic Chronic Kidney Disease

    DTIC Science & Technology

    2016-07-01

    AWARD NUMBER: W81XWH-14-1-0203 TITLE: The Endoplasmic Reticulum Stress Protein Calreticulin in Diabetic Chronic Kidney Disease PRINCIPAL...1 July 2015- 30 June 2016 4. TITLE AND SUBTITLE The Endoplasmic Reticulum Stress Protein Calreticulin in Diabetic Chronic Kidney Disease 5a...We hypothesize that ER stress induced by glucose in diabetes promotes diabetic CKD through CRT stimulation of TGF-beta-dependent calcium/NFAT

  14. Entamoeba histolytica Cell Surface Calreticulin Binds Human C1q and Functions in Amebic Phagocytosis of Host Cells

    PubMed Central

    Vaithilingam, Archana; Teixeira, Jose E.; Miller, Peter J.; Heron, Bradley T.

    2012-01-01

    Phagocytosis of host cells is characteristic of tissue invasion by the intestinal ameba Entamoeba histolytica, which causes amebic dysentery and liver abscesses. Entamoeba histolytica induces host cell apoptosis and uses ligands, including C1q, on apoptotic cells to engulf them. Two mass spectrometry analyses identified calreticulin in amebic phagosome preparations, and, in addition to its function as an endoplasmic reticulum chaperone, calreticulin is believed to be the macrophage receptor for C1q. The purpose of this study was to determine if calreticulin functions as an E. histolytica C1q receptor during phagocytosis of host cells. Calreticulin was localized to the surface of E. histolytica during interaction with both Jurkat lymphocytes and erythrocytes and was present in over 75% of phagocytic cups during amebic erythrophagocytosis. Presence of calreticulin on the cell surface was further demonstrated using a method that selectively biotinylated cell surface proteins and by flow cytometry using trophozoites overexpressing epitope-tagged calreticulin. Regulated overexpression of calreticulin increased E. histolytica's ability to phagocytose apoptotic lymphocytes and calcium ionophore-treated erythrocytes but had no effect on amebic adherence to or destruction of cell monolayers or surface expression of the GalNAc lectin and serine-rich E. histolytica protein (SREHP) receptors. Finally, E. histolytica calreticulin bound specifically to apoptotic lymphocytes and to human C1q. Collectively, these data implicate cell surface calreticulin as a receptor for C1q during E. histolytica phagocytosis of host cells. PMID:22473608

  15. Structural and Functional Relationships between the Lectin and Arm Domains of Calreticulin*

    PubMed Central

    Pocanschi, Cosmin L.; Kozlov, Guennadi; Brockmeier, Ulf; Brockmeier, Achim; Williams, David B.; Gehring, Kalle

    2011-01-01

    Calreticulin and calnexin are key components in maintaining the quality control of glycoprotein folding within the endoplasmic reticulum. Although their lectin function of binding monoglucosylated sugar moieties of glycoproteins is well documented, their chaperone activity in suppressing protein aggregation is less well understood. Here, we use a series of deletion mutants of calreticulin to demonstrate that its aggregation suppression function resides primarily within its lectin domain. Using hydrophobic peptides as substrate mimetics, we show that aggregation suppression is mediated through a single polypeptide binding site that exhibits a Kd for peptides of 0.5–1 μm. This site is distinct from the oligosaccharide binding site and differs from previously identified sites of binding to thrombospondin and GABARAP (4-aminobutyrate type A receptor-associated protein). Although the arm domain of calreticulin was incapable of suppressing aggregation or binding hydrophobic peptides on its own, it did contribute to aggregation suppression in the context of the whole molecule. The high resolution x-ray crystal structure of calreticulin with a partially truncated arm domain reveals a marked difference in the relative orientations of the arm and lectin domains when compared with calnexin. Furthermore, a hydrophobic patch was detected on the arm domain that mediates crystal packing and may contribute to calreticulin chaperone function. PMID:21652723

  16. Demonstration of Calreticulin Expression in Hamster Pancreatic Adenocarcinoma with the Use of Fluorescent Gold Quantum Dots.

    PubMed

    Giorgakis, Emmanouil; Ramesh, Bala; Kamali-Dashtarzheneh, Ashkan; Fusai, Giuseppe Kito; Imber, Charles; Tsironis, Dimitrios; Loizidou, Marilena

    2016-03-01

    There is dire need for discovery of novel pancreatic cancer biomarkers and of agents with the potential for simultaneous diagnostic and therapeutic capacity. This study demonstrates calreticulin expression on hamster pancreatic adenocarcinoma via bio-conjugated gold quantum dots (AuQDs). Hamster pancreatic adenocarcinoma cells were cultured, fixed and incubated with fluorescent AuQDs, bio-conjugated to anti-calreticulin antibodies. Anti-calreticulin and AuQDs were produced in-house. AuQDs were manufactured to emit in the near-infrared. Cells were further characterized under confocal fluorescence. AuQDs were confirmed to emit in the near-infrared. AuQD bio-conjugation to calreticulin was confirmed via dot-blotting. Upon laser excitation and post-incubation with bio-conjugated AuQDs, pancreatic cancer cell lines emitted fluorescence in near-infrared. Hamster pancreatic cancer cells express calreticulin, which may be labelled with AuQDs. This study demonstrates the application of nanoparticle-based theranostics in pancreatic cancer. Such biomarker-targeting nanosystems are anticipated to play a significant role in the management of pancreatic cancer. Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

  17. Calreticulin secures calcium-dependent nuclear pore competency required for cardiogenesis.

    PubMed

    Faustino, Randolph S; Behfar, Atta; Groenendyk, Jody; Wyles, Saranya P; Niederlander, Nicolas; Reyes, Santiago; Puceat, Michel; Michalak, Marek; Terzic, Andre; Perez-Terzic, Carmen

    2016-03-01

    Calreticulin deficiency causes myocardial developmental defects that culminate in an embryonic lethal phenotype. Recent studies have linked loss of this calcium binding chaperone to failure in myofibrillogenesis through an as yet undefined mechanism. The purpose of the present study was to identify cellular processes corrupted by calreticulin deficiency that precipitate dysregulation of cardiac myofibrillogenesis related to acquisition of cardiac phenotype. In an embryonic stem cell knockout model, calreticulin deficit (crt(-/-)) compromised nucleocytoplasmic transport of nuclear localization signal-dependent and independent pathways, disrupting nuclear import of the cardiac transcription factor MEF2C. The expression of nucleoporins and associated nuclear transport proteins in derived crt(-/-) cardiomyocytes revealed an abnormal nuclear pore complex (NPC) configuration. Altered protein content in crt(-/-) cells resulted in remodeled NPC architecture that caused decreased pore diameter and diminished probability of central channel occupancy versus wild type counterparts. Ionophore treatment of impaired calcium handling in crt(-/-) cells corrected nuclear pore microarchitecture and rescued nuclear import resulting in normalized myofibrillogenesis. Thus, calreticulin deficiency alters nuclear pore function and structure, impeding myofibrillogenesis in nascent cardiomyocytes through a calcium dependent mechanism. This essential role of calreticulin in nucleocytoplasmic communication competency ties its regulatory action with proficiency of cardiac myofibrillogenesis essential for proper cardiac development. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. A novel assay to detect calreticulin mutations in myeloproliferative neoplasms

    PubMed Central

    Rosso, Valentina; Petiti, Jessica; Bracco, Enrico; Pedrola, Roberto; Carnuccio, Francesca; Signorino, Elisabetta; Carturan, Sonia; Calabrese, Chiara; Bot-Sartor, Giada; Ronconi, Michela; Serra, Anna; Saglio, Giuseppe; Frassoni, Francesco; Cilloni, Daniela

    2017-01-01

    The myeloproliferative neoplasms are chronic myeloid cancers divided in Philadelphia positive (Ph+), chronic myeloid leukemia, or negative: polycythemia vera (PV) essential thrombocythemia (ET), and primary myelofibrosis (PMF). Most Ph negative cases have an activating JAK2 or MPL mutation. Recently, somatic mutations in the calreticulin gene (CALR) were detected in 56–88% of JAK2/MPL-negative patients affected by ET or PMF. The most frequent mutations in CARL gene are type-1 and 2. Currently, CALR mutations are evaluated by sanger sequencing. The evaluation of CARL mutations increases the diagnostic accuracy in patients without other molecular markers and could represent a new therapeutic target for molecular drugs. We developed a novel detection assay in order to identify type-1 and 2 CALR mutations by PNA directed PCR clamping. Seventy-five patients affected by myeloproliferative neoplasms and seven controls were examined by direct DNA sequencing and by PNA directed PCR clamping. The assay resulted to be more sensitive, specific and cheaper than sanger sequencing and it could be applied even in laboratory not equipped for more sophisticated analysis. Interestingly, we report here a case carrying both type 1 and type2 mutations in CALR gene. PMID:28031530

  19. An in vivo role for Trypanosoma cruzi calreticulin in antiangiogenesis.

    PubMed

    Molina, María C; Ferreira, Viviana; Valck, Carolina; Aguilar, Lorena; Orellana, Juana; Rojas, Alvaro; Ramirez, Galia; Billetta, Rosario; Schwaeble, Wilhelm; Lemus, David; Ferreira, Arturo

    2005-04-01

    Angiogenesis leads to neovascularization from existing blood vessels. It is associated with tumor growth and metastasis and is regulated by pro- and antiangiogenic molecules, some of them currently under clinical trials for cancer treatment. During the last few years we have cloned, sequenced and expressed a Trypanosoma cruzi calreticulin gene (TcCRT). Its product, TcCRT, a 45 kDa protein, is more than 50% identical to human CRT (HuCRT). TcCRT, present on the surface of trypomastigotes, binds both C1q and mannan binding lectin and inhibits the classical activation pathway of human complement. Since TcCRT is highly homologous to a functional antiangiogenic fragment from HuCRT (aa 120-180), recombinant (r) and native (n) TcCRT were tested in their antiangiogenic effects, in the chick embryonic chorioallantoid membrane (CAM) assay. Both proteins mediated highly significant antiangiogenic effects in the in vivo CAM assay. This effect was further substantiated in experiments showing that the plasmid construct pSecTag/TcCRT also displayed significant antiangiogenic properties, as compared to the empty vector. Most likely, the fact that antiangiogenic substances act preferentially on growing neoplasic tissues, but not on already established tumors, is due to their effects on emerging blood vessels. The results shown here indicate that TcCRT, like its human counterpart, has antiangiogenic properties. These properties may explain, at least partly, the reported antineoplasic effect of experimental T. cruzi infection.

  20. Calreticulin mutation profile in Indian patients with primary myelofibrosis.

    PubMed

    Sazawal, Sudha; Singh, Neha; Mahapatra, Manoranjan; Saxena, Renu

    2015-12-01

    Somatic mutations in Calreticulin (CALR) have been recently discovered in JAK2/MPL unmutated patients with primary myelofibrosis (PMF) or essential thrombocythemia. Clinical and hematologic features were obtained for 80 patients with PMF. JAK2V617F mutation was analyzed by DNA tetra-primer amplification refractory mutation system (ARMS-PCR). CALR and MPL mutations were identified by bi-directional Sanger sequencing. CALR mutations were detected in 11.2% (9/80) of all PMF patients and 25.7% (9/35) of all JAK2V617F and MPL unmutated patients all of which were Type I mutation or deletions. A novel CALR mutation pattern (c.1241_1288del) was identified in one (1/9) patient. No case of Type II mutations or scattered point mutations was found in any of these patients. Uni-variate analysis at presentation showed that CALR mutations were significantly associated with younger age (P = 0.003) and larger spleen size (P = 0.001). No significant correlation was found between CALR mutation and clinico-hematologic characteristics or international prognostic scoring system (IPSS) scoring of the PMF patients. CALR mutations have a distinct molecular profile in Indian patients, different from that of other studies worldwide. Larger prospective studies need to be designed to establish the impact of paucity of Type II mutations in contributing to disease phenotype and prognostic outcome of patients.

  1. Overexpression of calreticulin sensitizes SERCA2a to oxidative stress.

    PubMed

    Ihara, Yoshito; Kageyama, Kan; Kondo, Takahito

    2005-04-22

    Calreticulin (CRT), a Ca(2+)-binding molecular chaperone in the endoplasmic reticulum, plays a vital role in cardiac physiology and pathology. Oxidative stress is a main cause of myocardiac disorder in the ischemic heart, but the function of CRT under oxidative stress is not fully understood. In this study, the effect of overexpression of CRT on sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase (SERCA) 2a under oxidative stress was examined using myocardiac H9c2 cells transfected with the CRT gene. The in vitro activity of SERCA2a and uptake of (45)Ca(2+) into isolated microsomes were suppressed by H(2)O(2) in CRT-overexpressing cells compared with controls. Moreover, SERCA2a protein was degraded via a proteasome-dependent pathway following the formation of a complex with CRT under the stress with H(2)O(2). Thus, we conclude that overexpression of CRT enhances the inactivation and degradation of SERCA2a in the cells under oxidative stress, suggesting some pathophysiological functions of CRT in Ca(2+) homeostasis of myocardiac disease.

  2. Trypanosoma cruzi Calreticulin Topographical Variations in Parasites Infecting Murine Macrophages.

    PubMed

    González, Andrea; Valck, Carolina; Sánchez, Gittith; Härtel, Steffen; Mansilla, Jorge; Ramírez, Galia; Fernández, María Soledad; Arias, José Luis; Galanti, Norbel; Ferreira, Arturo

    2015-05-01

    Trypanosoma cruzi calreticulin (TcCRT), a 47-kDa chaperone, translocates from the endoplasmic reticulum to the area of flagellum emergence. There, it binds to complement components C1 and mannan-binding lectin (MBL), thus acting as a main virulence factor, and inhibits the classical and lectin pathways. The localization and functions of TcCRT, once the parasite is inside the host cell, are unknown. In parasites infecting murine macrophages, polyclonal anti-TcCRT antibodies detected TcCRT mainly in the parasite nucleus and kinetoplast. However, with a monoclonal antibody (E2G7), the resolution and specificity of the label markedly improved, and TcCRT was detected mainly in the parasite kinetoplast. Gold particles, bound to the respective antibodies, were used as probes in electron microscopy. This organelle may represent a stopover and accumulation site for TcCRT, previous its translocation to the area of flagellum emergence. Finally, early during T. cruzi infection and by unknown mechanisms, an important decrease in the number of MHC-I positive host cells was observed. © The American Society of Tropical Medicine and Hygiene.

  3. Trypanosoma cruzi Calreticulin Topographical Variations in Parasites Infecting Murine Macrophages

    PubMed Central

    González, Andrea; Valck, Carolina; Sánchez, Gittith; Härtel, Steffen; Mansilla, Jorge; Ramírez, Galia; Fernández, María Soledad; Arias, José Luis; Galanti, Norbel; Ferreira, Arturo

    2015-01-01

    Trypanosoma cruzi calreticulin (TcCRT), a 47-kDa chaperone, translocates from the endoplasmic reticulum to the area of flagellum emergence. There, it binds to complement components C1 and mannan-binding lectin (MBL), thus acting as a main virulence factor, and inhibits the classical and lectin pathways. The localization and functions of TcCRT, once the parasite is inside the host cell, are unknown. In parasites infecting murine macrophages, polyclonal anti-TcCRT antibodies detected TcCRT mainly in the parasite nucleus and kinetoplast. However, with a monoclonal antibody (E2G7), the resolution and specificity of the label markedly improved, and TcCRT was detected mainly in the parasite kinetoplast. Gold particles, bound to the respective antibodies, were used as probes in electron microscopy. This organelle may represent a stopover and accumulation site for TcCRT, previous its translocation to the area of flagellum emergence. Finally, early during T. cruzi infection and by unknown mechanisms, an important decrease in the number of MHC-I positive host cells was observed. PMID:25758653

  4. Calreticulin is a secreted BMP antagonist, expressed in Hensen's node during neural induction.

    PubMed

    De Almeida, Irene; Oliveira, Nidia M M; Randall, Rebecca A; Hill, Caroline S; McCoy, John M; Stern, Claudio D

    2017-01-15

    Hensen's node is the "organizer" of the avian and mammalian early embryo. It has many functions, including neural induction and patterning of the ectoderm and mesoderm. Some of the signals responsible for these activities are known but these do not explain the full complexity of organizer activity. Here we undertake a functional screen to discover new secreted factors expressed by the node at this time of development. Using a Signal Sequence Trap in yeast, we identify several candidates. Here we focus on Calreticulin. We show that in addition to its known functions in intracellular Calcium regulation and protein folding, Calreticulin is secreted, it can bind to BMP4 and act as a BMP antagonist in vivo and in vitro. Calreticulin is not sufficient to account for all organizer functions but may contribute to the complexity of its activity.

  5. Calreticulin-like molecule in trophozoites of Entamoeba histolytica HM1:IMSS (Swissprot: accession P83003).

    PubMed

    González, Enrique; Rico, Guadalupe; Mendoza, Guillermo; Ramos, Fernando; García, Gabriela; Morán, Patricia; Valadez, Alicia; Melendro, Emma I; Ximénez, Cecilia

    2002-12-01

    In this work, we report the partial sequence of a 51 kDa protein of Entamoeba histolytica that is highly immunogenic in humans. Partial sequencing of the N-terminal end showed that 18 of the first 20 amino acid residues of the protein were identified uniquely, indicating that the final product was a homogeneous protein preparation. The N-terminal sequence that was found was: KVYFEETFENGWKXIWSKW. Comparing the 19-amino acid sequence of the protein in automated databases shows significant similarity with amino acid sequences of the calreticulin-like protein of spinach leaves (77%) and of the calreticulin precursor of Dictyostelium discoideum (60%).

  6. Calreticulin Mutations in Myeloproliferative Neoplasms: Comparison of Three Diagnostic Methods

    PubMed Central

    Park, Ji-Hye; Sevin, Margaux; Ramla, Selim; Truffot, Aurélie; Verrier, Tiffany; Bouchot, Dominique; Courtois, Martine; Bas, Mathilde; Benali, Sonia; Bailly, François; Favre, Bernardine; Guy, Julien; Martin, Laurent; Maynadié, Marc; Carillo, Serge; Girodon, François

    2015-01-01

    Calreticulin (CALR) mutations have recently been reported in 70–84% of JAK2V617F-negative myeloproliferative neoplasms (MPN), and this detection has become necessary to improve the diagnosis of MPN. In a large single-centre cohort of 298 patients suffering from Essential Thrombocythemia (ET), the JAK2V617F, CALR and MPL mutations were noted in 179 (60%), 56 (18.5%) and 13 (4.5%) respectively. For the detection of the CALR mutations, three methods were compared in parallel: high-resolution melting-curve analysis (HRM), product-sizing analysis and Sanger sequencing. The sensitivity for the HRM, product-sizing analysis and Sanger sequencing was 96.4%, 98.2% and 89.3% respectively, whereas the specificity was 96.3%, 100% and 100%. In our cohort, the product-sizing analysis was the most sensitive method and was the easiest to interpret, while the HRM was sometimes difficult to interpret. In contrast, when large series of samples were tested, HRM provided results more quickly than did the other methods, which required more time. Finally, the sequencing method, which is the reference method, had the lowest sensitivity but can be used to describe the type of mutation precisely. Altogether, our results suggest that in routine laboratory practice, product-sizing analysis is globally similar to HRM for the detection of CALR mutations, and that both may be used as first-line screening tests. If the results are positive, Sanger sequencing can be used to confirm the mutation and to determine its type. Product-sizing analysis provides sensitive and specific results, moreover, with the quantitative measurement of CALR, which might be useful to monitor specific treatments. PMID:26501981

  7. Confirmation of tick bite by detection of antibody to Ixodes calreticulin salivary protein.

    PubMed

    Alarcon-Chaidez, Francisco; Ryan, Raymond; Wikel, Stephen; Dardick, Kenneth; Lawler, Caroline; Foppa, Ivo M; Tomas, Patricio; Cushman, Alexis; Hsieh, Ann; Spielman, Andrew; Bouchard, Keith R; Dias, Filiciano; Aslanzadeh, Jaber; Krause, Peter J

    2006-11-01

    Ticks introduce a variety of pharmacologically active molecules into their host during attachment and feeding in order to obtain a blood meal. People who are repeatedly exposed to ticks may develop an immune response to tick salivary proteins. Despite this response, people usually are unaware of having been bitten, especially if they are not repeatedly exposed to ticks. In order to develop a laboratory marker of tick exposure that would be useful in understanding the epidemiology of tick-borne infection and the immune response to tick bite, we developed an enzyme-linked immunosorbent assay (ELISA) to detect antibody to a recombinant form of calreticulin protein found in the salivary glands of Ixodes scapularis, a member of a complex of Ixodes ticks that serve as the vectors for Lyme disease, human babesiosis, and human granulocytic anaplasmosis. Using this assay, we tested sera obtained from C3H/HeN and BALB/c mice before and after experimental deer tick infestation. These mice developed antibody to Ixodes calreticulin antigen after infestation. We then used the same assay to test sera obtained from people before and after they experienced deer tick bite(s). People experiencing deer tick bite(s) developed Ixodes calreticulin-specific antibody responses that persisted for up to 17 months. This Ixodes recombinant calreticulin ELISA provides objective evidence of deer tick exposure in people.

  8. Confirmation of Tick Bite by Detection of Antibody to Ixodes Calreticulin Salivary Protein▿

    PubMed Central

    Alarcon-Chaidez, Francisco; Ryan, Raymond; Wikel, Stephen; Dardick, Kenneth; Lawler, Caroline; Foppa, Ivo M.; Tomas, Patricio; Cushman, Alexis; Hsieh, Ann; Spielman, Andrew; Bouchard, Keith R.; Dias, Filiciano; Aslanzadeh, Jaber; Krause, Peter J.

    2006-01-01

    Ticks introduce a variety of pharmacologically active molecules into their host during attachment and feeding in order to obtain a blood meal. People who are repeatedly exposed to ticks may develop an immune response to tick salivary proteins. Despite this response, people usually are unaware of having been bitten, especially if they are not repeatedly exposed to ticks. In order to develop a laboratory marker of tick exposure that would be useful in understanding the epidemiology of tick-borne infection and the immune response to tick bite, we developed an enzyme-linked immunosorbent assay (ELISA) to detect antibody to a recombinant form of calreticulin protein found in the salivary glands of Ixodes scapularis, a member of a complex of Ixodes ticks that serve as the vectors for Lyme disease, human babesiosis, and human granulocytic anaplasmosis. Using this assay, we tested sera obtained from C3H/HeN and BALB/c mice before and after experimental deer tick infestation. These mice developed antibody to Ixodes calreticulin antigen after infestation. We then used the same assay to test sera obtained from people before and after they experienced deer tick bite(s). People experiencing deer tick bite(s) developed Ixodes calreticulin-specific antibody responses that persisted for up to 17 months. This Ixodes recombinant calreticulin ELISA provides objective evidence of deer tick exposure in people. PMID:16928887

  9. A comparative proteomic study identified calreticulin and prohibitin up-regulated in adrenocortical carcinomas

    PubMed Central

    2013-01-01

    Background Identifying novel tumor biomarkers to develop more effective diagnostic and therapeutic strategies for patients with ACC is urgently needed. The aim of the study was to compare the proteomic profiles between adrenocortical carcinomas (ACC) and normal adrenocortical tissues in order to identify novel potential biomarkers for ACC. Methods The protein samples from 12 ACC tissues and their paired adjacent normal adrenocortical tissues were profiled with two-dimensional electrophoresis; and differentially expressed proteins were identified by mass spectrometry. Expression patterns of three differently expressed proteins calreticulin, prohibitin and HSP60 in ACC, adrenocortical adenomas (ACA) and normal adrenocortical tissues were further validated by immunohistochemistry. Results In our proteomic study, we identified 20 up-regulated and 9 down-regulated proteins in ACC tissues compared with paired normal controls. Most of the up-regulated proteins were focused in protein binding and oxidoreductase activity in Gene Ontology (GO) molecular function classification. By immunohistochemistry, two biomarkers calreticulin and prohibitin were validated to be overexpressed in ACC compared with adrenocortical adenomas (ACA) and normal tissues, but also calreticulin overexpression was significantly associated with tumor stages of ACC. Conclusion For the first time, calreticulin and prohibitin were identified to be novel candidate biomarkers for ACC, and their roles during ACC carcinogenesis and clinical significance deserves further investigation. Virtual slides The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1897372598927465 PMID:23587357

  10. Transient dissociation of polyribosomes and concurrent recruitment of calreticulin and calmodulin transcripts in gravistimulated maize pulvini

    NASA Technical Reports Server (NTRS)

    Heilmann, I.; Shin, J.; Huang, J.; Perera, I. Y.; Davies, E.

    2001-01-01

    The dynamics of polyribosome abundance were studied in gravistimulated maize (Zea mays) stem pulvini. During the initial 15 min of gravistimulation, the amount of large polyribosomes transiently decreased. The transient decrease in polyribosome levels was accompanied by a transient decrease in polyribosome-associated mRNA. After 30 min of gravistimulation, the levels of polyribosomes and the amount of polyribosome-associated mRNA gradually increased over 24 h up to 3- to 4-fold of the initial value. Within 15 min of gravistimulation, total levels of transcripts coding for calreticulin and calmodulin were elevated 5-fold in maize pulvinus total RNA. Transcripts coding for calreticulin and calmodulin were recruited into polyribosomes within 15 min of gravistimulation. Over 4 h of gravistimulation, a gradual increase in the association of calreticulin and calmodulin transcripts with polyribosomes was seen predominantly in the lower one-half of the maize pulvinus; the association of transcripts for vacuolar invertase with polyribosomes did not change over this period. Our results suggest that within 15 min of gravistimulation, the translation of the majority of transcripts associated with polyribosomes decreased, resembling a general stress response. Recruitment of calreticulin and calmodulin transcripts into polyribosomes occurred predominantly in the lower pulvinus one-half during the first 4 h when the presentation time for gravistimulation in the maize pulvinus is not yet complete.

  11. Transient dissociation of polyribosomes and concurrent recruitment of calreticulin and calmodulin transcripts in gravistimulated maize pulvini

    NASA Technical Reports Server (NTRS)

    Heilmann, I.; Shin, J.; Huang, J.; Perera, I. Y.; Davies, E.

    2001-01-01

    The dynamics of polyribosome abundance were studied in gravistimulated maize (Zea mays) stem pulvini. During the initial 15 min of gravistimulation, the amount of large polyribosomes transiently decreased. The transient decrease in polyribosome levels was accompanied by a transient decrease in polyribosome-associated mRNA. After 30 min of gravistimulation, the levels of polyribosomes and the amount of polyribosome-associated mRNA gradually increased over 24 h up to 3- to 4-fold of the initial value. Within 15 min of gravistimulation, total levels of transcripts coding for calreticulin and calmodulin were elevated 5-fold in maize pulvinus total RNA. Transcripts coding for calreticulin and calmodulin were recruited into polyribosomes within 15 min of gravistimulation. Over 4 h of gravistimulation, a gradual increase in the association of calreticulin and calmodulin transcripts with polyribosomes was seen predominantly in the lower one-half of the maize pulvinus; the association of transcripts for vacuolar invertase with polyribosomes did not change over this period. Our results suggest that within 15 min of gravistimulation, the translation of the majority of transcripts associated with polyribosomes decreased, resembling a general stress response. Recruitment of calreticulin and calmodulin transcripts into polyribosomes occurred predominantly in the lower pulvinus one-half during the first 4 h when the presentation time for gravistimulation in the maize pulvinus is not yet complete.

  12. Transient dissociation of polyribosomes and concurrent recruitment of calreticulin and calmodulin transcripts in gravistimulated maize pulvini.

    PubMed

    Heilmann, I; Shin, J; Huang, J; Perera, I Y; Davies, E

    2001-11-01

    The dynamics of polyribosome abundance were studied in gravistimulated maize (Zea mays) stem pulvini. During the initial 15 min of gravistimulation, the amount of large polyribosomes transiently decreased. The transient decrease in polyribosome levels was accompanied by a transient decrease in polyribosome-associated mRNA. After 30 min of gravistimulation, the levels of polyribosomes and the amount of polyribosome-associated mRNA gradually increased over 24 h up to 3- to 4-fold of the initial value. Within 15 min of gravistimulation, total levels of transcripts coding for calreticulin and calmodulin were elevated 5-fold in maize pulvinus total RNA. Transcripts coding for calreticulin and calmodulin were recruited into polyribosomes within 15 min of gravistimulation. Over 4 h of gravistimulation, a gradual increase in the association of calreticulin and calmodulin transcripts with polyribosomes was seen predominantly in the lower one-half of the maize pulvinus; the association of transcripts for vacuolar invertase with polyribosomes did not change over this period. Our results suggest that within 15 min of gravistimulation, the translation of the majority of transcripts associated with polyribosomes decreased, resembling a general stress response. Recruitment of calreticulin and calmodulin transcripts into polyribosomes occurred predominantly in the lower pulvinus one-half during the first 4 h when the presentation time for gravistimulation in the maize pulvinus is not yet complete.

  13. Calreticulin mutation burden--is it a stable clone in patients with essential thrombocythemia and myelofibrosis?

    PubMed

    Shuly, Yulia; Nagar, Meital; Ben-Asaf, Lior; Kneller, Abraham; Steinberg, David M; Amariglio, Ninette; Salomon, Ophira

    2015-12-01

    Calreticulin mutation represents the second most frequent mutation after JAK2 V617F in myeloproliferative disorder and is considered to be a driving mutation. Herein the mutation burden was evaluated in patients with essential thrombocythemia or myelofibrosis and found to increase by 5.7% over time unrelated to the time elapsed from the initial to the final positive test. The longer the course of the disease when first tested (range 0-30 years, mean 7.9 years) the lower mutation burden was observed. The mutated clone was larger in type II in comparison with type I mutation when first tested but the difference in mutation burden from the final to the first positive test was significantly higher in those with type I. Similarly, the difference in mutation burden was higher in patients with essential thrombocythemia reaching almost 8% in comparison to 1.3% in post-essential thrombocythemia myelofibrosis. Thus a repeat calreticulin quantitative test is not warranted.

  14. Macrophages eat cancer cells using their own calreticulin as a guide: roles of TLR and Btk.

    PubMed

    Feng, Mingye; Chen, James Y; Weissman-Tsukamoto, Rachel; Volkmer, Jens-Peter; Ho, Po Yi; McKenna, Kelly M; Cheshier, Samuel; Zhang, Michael; Guo, Nan; Gip, Phung; Mitra, Siddhartha S; Weissman, Irving L

    2015-02-17

    Macrophage-mediated programmed cell removal (PrCR) is an important mechanism of eliminating diseased and damaged cells before programmed cell death. The induction of PrCR by eat-me signals on tumor cells is countered by don't-eat-me signals such as CD47, which binds macrophage signal-regulatory protein α to inhibit phagocytosis. Blockade of CD47 on tumor cells leads to phagocytosis by macrophages. Here we demonstrate that the activation of Toll-like receptor (TLR) signaling pathways in macrophages synergizes with blocking CD47 on tumor cells to enhance PrCR. Bruton's tyrosine kinase (Btk) mediates TLR signaling in macrophages. Calreticulin, previously shown to be an eat-me signal on cancer cells, is activated in macrophages for secretion and cell-surface exposure by TLR and Btk to target cancer cells for phagocytosis, even if the cancer cells themselves do not express calreticulin.

  15. Calreticulin and Jak2 as Chaperones for MPL: Insights into MPN Pathogenesis

    DTIC Science & Technology

    2016-09-01

    major myeloproliferative neoplasms (MPNs) as classified by the world health organization. One of the biggest challenges is to understand how Jak2 , MPL...myelofibrosis (PMF), two of the 8 major myeloproliferative neoplasms (MPNs) as classified by the WHO. One of the biggest challenges is to understand how Jak2 ...Thrombopoietin Receptor (Mpl) - Janus kinase 2 ( Jak2 ) - Calreticulin (CALR) - Myeloproliferative Neoplasms (MPN) - Essential Thrombocythemia (ET

  16. Cloning and characterization of the calreticulin gene from Ricinus communis L.

    PubMed

    Coughlan, S J; Hastings, C; Winfrey, R

    1997-08-01

    A full-length cDNA encoding a calreticulin-like protein was isolated by immune-screening a germinating castor bean endosperm cDNA library with antisera raised to the total lumenal fraction of purified plant endoplasmic reticulum. The calcium-binding properties of the recombinant protein were characterized and shown to be essentially identical to those reported for the mammalian calreticulin. Calcium overlays and immune blot analysis confirmed the endoplasmic lumenal identity of this reticuloplasmin. Probing protein blots of endoplasmic reticulum subfractions with radio-iodinated calreticulin showed specific associations with various polypeptides including one identified as the abundant reticuloplasmin protein disulfide isomerase. Characterization of the corresponding genomic clones revealed that calreticulin is encoded by a single gene of 3 kb in castor. The full genomic sequence reveals the presence of 12 introns, 12 translated exons, and one exon containing the last three amino acids of the translated sequence and the 3'-untranslated region of the gene. Northern blot analysis of RNA isolated from various organ tissues showed a basal constitutive level of expression throughout the plant, but more abundant mRNA being detected in tissues active in secretion. This was confirmed by analysis of transgenic tobacco plants containing 1.8 kb of 5'-untranslated genomic sequence fused to the beta-glucuronidase reporter gene (GUS) showed a more localized pattern of expression. Activity being localized to the vasculature (phloem, root hairs and root tip) in vegetative tissue, and being strongly expressed in the floral organs including the developing and germinating seed.

  17. Comparative effect of human and Trypanosoma cruzi calreticulin in wound healing.

    PubMed

    Ignacio Arias, J; Sepulveda, Caroll; Bravo, Patricia; Hamilton-West, Christopher; Maldonado, Ismael; Ferreira, Arturo

    2015-01-01

    In orthopaedics, the use of factors that enhance granulation tissue formation and prevent or delay new bone regeneration is sometimes desirable. Calreticulin (CRT), a unique endoplasmic reticulum luminal Ca(2+) -binding chaperone widely distributed in eukaryotic cells, is involved in many cellular functions. Among them, CRT has an important influence in cutaneous wound healing and diverse processes associated with cutaneous repair, inhibition of angiogenesis, promotion of cell adhesion and antitumour effect. One of the molecules involved in several aspects of the host-parasite interplay is Trypanosoma cruzi calreticulin (TcCRT), which is highly homologous to human calreticulin (HuCRT). Here, recombinant (r)HuCRT and rTcCRT are compared on their abilities to affect fibroblast behaviour in a scratch plate assay, and wound healing in in vivo skin rat models. In molar terms, rTcCRT is three orders of magnitude more efficient than rHuCRT in increasing proliferation and migration of human fibroblasts in vitro. A similar effect was observed in vivo on rat skin wounds and inhibition of bone gap bridging in rabbit unicortical bone osteotomies.

  18. Molecular characterisation and expression analysis of a novel calreticulin (CRT) gene in the dinoflagellate Prorocentrum minimum.

    PubMed

    Ponmani, Thangaraj; Guo, Ruoyu; Suh, Young Sang; Ki, Jang-Seu

    2015-03-01

    Calreticulin is a multifunctional Ca(2+)-binding protein that has been well characterised in mammalian cells. Here, we characterised a novel calreticulin (CRT2) gene in the dinoflagellate Prorocentrum minimum, which codes for a calcium binding protein and examined its expression pattern following the addition of calcium and ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA). PmCRT2 is encoded in the nuclear genome of P. minimum without introns. The full length cDNA of PmCRT2 was found to be 1,493 base pairs (bp) in length, which ranges from the dinoflagellate spliced leader sequence to the poly (A) tail and contains a 1,173-bp open reading frame, a 70-bp 5'-untranslated region (UTR), and a 207-bp 3'-UTR. On the basis of in silico analyses that revealed the distinct domain architectures of PmCRT2, we classified this protein under the calreticulin family. PmCRT2 gene expression was up-regulated in the presence of excess calcium in a dose-dependent manner; however, PmCRT2 expression was down-regulated by the addition of EGTA. These results clearly indicate that PmCRT2 plays a vital role in calcium regulation and this may be involved in the stress response of P. minimum.

  19. Nuclear export of the glucocorticoid receptor is accelerated by cell fusion-dependent release of calreticulin.

    PubMed

    Walther, Rhian F; Lamprecht, Claudia; Ridsdale, Andrew; Groulx, Isabelle; Lee, Stephen; Lefebvre, Yvonne A; Haché, Robert J G

    2003-09-26

    Nucleocytoplasmic exchange of nuclear hormone receptors is hypothesized to allow for rapid and direct interactions with cytoplasmic signaling factors. In addition to recycling between a naïve, chaperone-associated cytoplasmic complex and a liganded chaperone-free nuclear form, the glucocorticoid receptor (GR) has been observed to shuttle between nucleus and cytoplasm. Nuclear export of GR and other nuclear receptors has been proposed to depend on direct interactions with calreticulin, which is predominantly localized to the lumen of the endoplasmic reticulum. We show that rapid calreticulin-mediated nuclear export of GR is a specific response to transient disruption of the endoplasmic reticulum that occurs during polyethylene glycol-mediated cell fusion. Using live and digitonin-permeabilized cells we demonstrate that, in the absence of cell fusion, GR nuclear export occurs slowly over a period of many hours independent of direct interaction with calreticulin. Our findings temper expectations that nuclear receptors respond rapidly and directly to cytoplasmic signals in the absence of additional regulatory control. These results highlight the importance of verifying findings of nucleocytoplasmic trafficking using techniques in addition to heterokaryon cell fusion.

  20. Agarose gel shift assay reveals that calreticulin favors substrates with a quaternary structure in solution.

    PubMed

    Boelt, Sanne Grundvad; Houen, Gunnar; Højrup, Peter

    2015-07-15

    Here we present an agarose gel shift assay that, in contrast to other electrophoresis approaches, is loaded in the center of the gel. This allows proteins to migrate in either direction according to their isoelectric points. Therefore, the presented assay enables a direct visualization, separation, and prefractionation of protein interactions in solution independent of isoelectric point. We demonstrate that this assay is compatible with immunochemical methods and mass spectrometry. The assay was used to investigate interactions with several potential substrates for calreticulin, a chaperone that is involved in different biological aspects through interaction with other proteins. The current analytical assays used to investigate these interactions are mainly spectroscopic aggregation assays or solid phase assays that do not provide a direct visualization of the stable protein complex but rather provide an indirect measure of interactions. Therefore, no interaction studies between calreticulin and substrates in solution have been investigated previously. The results presented here indicate that calreticulin has a preference for substrates with a quaternary structure and primarily β-sheets in their secondary structure. It is also demonstrated that the agarose gel shift assay is useful in the study of other protein interactions and can be used as an alternative method to native polyacrylamide gel electrophoresis.

  1. The calcium-binding protein calreticulin is a major constituent of lytic granules in cytolytic T lymphocytes

    PubMed Central

    1993-01-01

    Cytolytic T lymphocytes (CTL), natural killer cells, and lymphokine- activated killer (LAK) cells are cytolytic cells known to release the cytolytic protein perforin and a family of proteases, named granzymes, from cytoplasmic stores upon interaction with target cells. We now report the purification of an additional major 60-kD granule-associated protein (grp 60) from human LAK cells and from mouse cytolytic T cells. The NH2-terminal amino acid sequence of the polypeptide was found to be identical to calreticulin. Calreticulin is a calcium storage protein and carries a COOH-terminal KDEL sequence, known to act as a retention signal for proteins destined to the lumen of the endoplasmic reticulum. In CTLs, however, calreticulin colocalizes with the lytic perforin to the lysosome-like secretory granules, as confirmed by double label immunofluorescence confocal microscopy. Moreover, when the release of granule-associated proteins was triggered by stimulation of the T cell receptor complex, calreticulin was released along with granzymes A and D. Since perforin is activated and becomes lytic in the presence of calcium, we propose that the role of calreticulin is to prevent organelle autolysis due to the protein's calcium chelator capacity. PMID:8418194

  2. Ovalbumin-derived precursor peptides are transferred sequentially from gp96 and calreticulin to MHC I in the endoplasmic reticulum

    PubMed Central

    Kropp, Laura E.; Garg, Manish; Binder, Robert J.

    2010-01-01

    Cellular peptides generated by proteasomal degradation of proteins in the cytosol and destined for presentation by MHC I are associated with several chaperones. Hsp70, hsp90 and the TCP1-ring complex have been implicated as important cytosolic players for chaperoning these peptides. In this study we report that gp96 and calreticulin are essential for chaperoning peptides in the endoplasmic reticulum. Importantly we demonstrate that cellular peptides are transferred sequentially from gp96 to calreticulin and then to MHC I forming a relay line. Disruption of this relay line by removal of gp96 or calreticulin prevents the binding of peptides by MHC I and hence presentation of the MHC I-peptide complex on the cell surface. Our results are important for understanding how peptides are processed and trafficked within the endoplasmic reticulum before exiting in association with MHC I heavy chains and β2-microglobulin as a trimolecular complex. PMID:20410492

  3. Interaction of HTLV-1 Tax protein with the calreticulin: Implications for Tax nuclear export and secretion

    PubMed Central

    Alefantis, Timothy; Flaig, Katherine E.; Wigdahl, Brian; Jain, Pooja

    2007-01-01

    Summary Human T cell leukemia virus type 1 (HTLV-1) is the etiologic agent of adult T cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The HTLV-1 transcriptional transactivator protein Tax plays an integral role in virus replication and disease progression. Traditionally, Tax is described as a nuclear protein where it performs its primary role as a transcriptional transactivator. However, recent studies have clearly shown that Tax can also be localized to the cytoplasm where it has been shown to interact with a number of host transcription factors most notably NF-κB, constitutive expression of which is directly related to the T cell transforming properties of Tax in ATL patients. The presence of a functional nuclear export signal (NES) within Tax and the secretion of full-length Tax have also been demonstrated previously. Additionally, release of Tax from HTLV-1-infected cells and the presence of cell-free Tax was demonstrated in the CSF of HAM/TSP patients suggesting that the progression of HAM/TSP might be mediated by the ability of Tax to work as an extracellular cytokine. Therefore, in both ATL and HAM/TSP Tax nuclear export and nucleocytoplasmic shuttling may play a critical role, the mechanism of which remains unknown. In this study, we have demonstrated that the calcium binding protein calreticulin interacts with Tax by coimmunoprecipitation. This interaction was found to localize to a region at or near the nuclear membrane. In addition, differential expression of calreticulin was demonstrated in various cell types that correlated with their ability to retain cytoplasmic Tax, particularly in astrocytes. Finally, a comparison of a number of HTLV-1-infected T cell lines to non-infected T cells revealed higher expression of calreticulin in infected cells implicating a direct role for this protein in HTLV-1 infection. PMID:17395420

  4. Thyroid hormone receptor alpha1 follows a cooperative CRM1/calreticulin-mediated nuclear export pathway.

    PubMed

    Grespin, Matthew E; Bonamy, Ghislain M C; Roggero, Vincent R; Cameron, Nicole G; Adam, Lindsay E; Atchison, Andrew P; Fratto, Victoria M; Allison, Lizabeth A

    2008-09-12

    The thyroid hormone receptor alpha1 (TRalpha) exhibits a dual role as an activator or repressor of its target genes in response to thyroid hormone (T(3)). Previously, we have shown that TRalpha, formerly thought to reside solely in the nucleus bound to DNA, actually shuttles rapidly between the nucleus and cytoplasm. An important aspect of the shuttling activity of TRalpha is its ability to exit the nucleus through the nuclear pore complex. TRalpha export is not sensitive to treatment with the CRM1-specific inhibitor leptomycin B (LMB) in heterokaryon assays, suggesting a role for an export receptor other than CRM1. Here, we have used a combined approach of in vivo fluorescence recovery after photobleaching experiments, in vitro permeabilized cell nuclear export assays, and glutathione S-transferase pull-down assays to investigate the export pathway used by TRalpha. We show that, in addition to shuttling in heterokaryons, TRalpha shuttles rapidly in an unfused monokaryon system as well. Furthermore, our data show that TRalpha directly interacts with calreticulin, and point to the intriguing possibility that TRalpha follows a cooperative export pathway in which both calreticulin and CRM1 play a role in facilitating efficient translocation of TRalpha from the nucleus to cytoplasm.

  5. Thyroid Hormone Receptor α1 Follows a Cooperative CRM1/Calreticulin-mediated Nuclear Export Pathway*

    PubMed Central

    Grespin, Matthew E.; Bonamy, Ghislain M. C.; Roggero, Vincent R.; Cameron, Nicole G.; Adam, Lindsay E.; Atchison, Andrew P.; Fratto, Victoria M.; Allison, Lizabeth A.

    2008-01-01

    The thyroid hormone receptor α1 (TRα) exhibits a dual role as an activator or repressor of its target genes in response to thyroid hormone (T3). Previously, we have shown that TRα, formerly thought to reside solely in the nucleus bound to DNA, actually shuttles rapidly between the nucleus and cytoplasm. An important aspect of the shuttling activity of TRα is its ability to exit the nucleus through the nuclear pore complex. TRα export is not sensitive to treatment with the CRM1-specific inhibitor leptomycin B (LMB) in heterokaryon assays, suggesting a role for an export receptor other than CRM1. Here, we have used a combined approach of in vivo fluorescence recovery after photobleaching experiments, in vitro permeabilized cell nuclear export assays, and glutathione S-transferase pull-down assays to investigate the export pathway used by TRα. We show that, in addition to shuttling in heterokaryons, TRα shuttles rapidly in an unfused monokaryon system as well. Furthermore, our data show that TRα directly interacts with calreticulin, and point to the intriguing possibility that TRα follows a cooperative export pathway in which both calreticulin and CRM1 play a role in facilitating efficient translocation of TRα from the nucleus to cytoplasm. PMID:18641393

  6. Calreticulin is a microbial-binding molecule with phagocytosis-enhancing capacity.

    PubMed

    Liu, Xuemei; Xu, Na; Zhang, Shicui

    2013-09-01

    Calreticulin (CRT) is a highly conserved calcium-binding protein mainly involved in directing proper conformation of proteins and controlling calcium level. Accumulating data also show that CRT is emerging as an immune-relevant molecule. In this study, we demonstrated that the CRT gene from the amphioxus Branchiostoma japonicum, named Bjcrt, consisted of a signal peptide, three domains (N-, P-, C-domains) and an ER retrieval signal sequence (KDEL), which appears to be the ancient form of vertebrate CRTs, and Bjcrt was expressed in a tissue-specific manner, with the most abundant expression in the notochord. We also demonstrated for the first time that the recombinant BjCRT (rBjCRT) was able to bind the Gram-negative bacterium Escherichia coli and the Gram-positive bacterium Staphylococcus aureus. Moreover, both BjCRT as well as human recombinant calreticulin were able to promote the phagocytosis of E. coli and S. aureus by sea bass macrophages. These results indicate that CRT is a microbial-binding molecule and possesses an ability to enhance phagocytosis, a novel function assigned to CRT, reenforcing the notion that CRT is an immune-relevant molecule associated with host immune responses.

  7. Calreticulin contributes to C1q-dependent recruitment of microglia in the leech Hirudo medicinalis following a CNS injury.

    PubMed

    Le Marrec-Croq, Francoise; Bocquet-Garcon, Annelise; Vizioli, Jacopo; Vancamp, Christelle; Drago, Francesco; Franck, Julien; Wisztorski, Maxence; Salzet, Michel; Sautiere, Pierre-Eric; Lefebvre, Christophe

    2014-04-19

    The medicinal leech is considered as a complementary and appropriate model to study immune functions in the central nervous system (CNS). In a context in which an injured leech's CNS can naturally restore normal synaptic connections, the accumulation of microglia (immune cells of the CNS that are exclusively resident in leeches) has been shown to be essential at the lesion to engage the axonal sprouting. HmC1q (Hm for Hirudo medicinalis) possesses chemotactic properties that are important in the microglial cell recruitment by recognizing at least a C1q binding protein (HmC1qBP alias gC1qR). Recombinant forms of C1q were used in affinity purification and in vitro chemotaxis assays. Anti-calreticulin antibodies were used to neutralize C1q-mediated chemotaxis and locate the production of calreticulin in leech CNS. A newly characterized leech calreticulin (HmCalR) has been shown to interact with C1q and participate to the HmC1q-dependent microglia accumulation. HmCalR, which has been detected in only some microglial cells, is consequently a second binding protein for HmC1q, allowing the chemoattraction of resident microglia in the nerve repair process. These data give new insight into calreticulin/C1q interaction in an immune function of neuroprotection, suggesting another molecular target to use in investigation of microglia reactivity in a model of CNS injury.

  8. Hijacking of host calreticulin is required for the white spot syndrome virus replication cycle.

    PubMed

    Watthanasurorot, Apiruck; Guo, Enen; Tharntada, Sirinit; Lo, Chu-Fang; Söderhäll, Kenneth; Söderhäll, Irene

    2014-07-01

    We have previously shown that multifunctional calreticulin (CRT), which resides in the endoplasmic reticulum (ER) and is involved in ER-associated protein processing, responds to infection with white spot syndrome virus (WSSV) by increasing mRNA and protein expression and by forming a complex with gC1qR and thereby delaying apoptosis. Here, we show that CRT can directly interact with WSSV structural proteins, including VP15 and VP28, during an early stage of virus infection. The binding of VP28 with CRT does not promote WSSV entry, and CRT-VP15 interaction was detected in the viral genome in virally infected host cells and thus may have an effect on WSSV replication. Moreover, CRT was detected in the viral envelope of purified WSSV virions. CRT was also found to be of high importance for proper oligomerization of the viral structural proteins VP26 and VP28, and when CRT glycosylation was blocked with tunicamycin, a significant decrease in both viral replication and assembly was detected. Together, these findings suggest that CRT confers several advantages to WSSV, from the initial steps of WSSV infection to the assembly of virions. Therefore, CRT is required as a "vital factor" and is hijacked by WSSV for its replication cycle. Importance: White spot syndrome virus (WSSV) is a double-stranded DNA virus and the cause of a serious disease in a wide range of crustaceans that often leads to high mortality rates. We have previously shown that the protein calreticulin (CRT), which resides in the endoplasmic reticulum (ER) of the cell, is important in the host response to the virus. In this report, we show that the virus uses this host protein to enter the cell and to make the host produce new viral structural proteins. Through its interaction with two viral proteins, the virus "hijacks" host calreticulin and uses it for its own needs. These findings provide new insight into the interaction between a large DNA virus and the host protein CRT and may help in understanding

  9. Folding of thyroglobulin in the calnexin/calreticulin pathway and its alteration by loss of Ca2+ from the endoplasmic reticulum.

    PubMed Central

    Di Jeso, Bruno; Ulianich, Luca; Pacifico, Francesco; Leonardi, Antonio; Vito, Pasquale; Consiglio, Eduardo; Formisano, Silvestro; Arvan, Peter

    2003-01-01

    During its initial folding in the endoplasmic reticulum (ER), newly synthesized thyroglobulin (Tg) is known to interact with calnexin and other ER molecular chaperones, but its interaction with calreticulin has not been examined previously. In the present study, we have investigated the interactions of endogenous Tg with calreticulin and with several other ER chaperones. We find that, in FRTL-5 and PC-Cl3 cells, calnexin and calreticulin interact with newly synthesized Tg in a carbohydrate-dependent manner, with largely overlapping kinetics that are concomitant with the maturation of Tg intrachain disulphide bonds, preceding Tg dimerization and exit from the ER. Calreticulin co-precipitates more newly synthesized Tg than does calnexin; however, using two different experimental approaches, calnexin and calreticulin were found in ternary complexes with Tg, making this the first endogenous protein reported in ternary complexes with calnexin and calreticulin in the ER of live cells. Depletion of Ca(2+) from the ER elicited by thapsigargin (a specific inhibitor of ER Ca(2+)-ATPases) results in retention of Tg in this organelle. Interestingly, thapsigargin treatment induces the premature exit of Tg from the calnexin/calreticulin cycle, while stabilizing and prolonging interactions of Tg with BiP (immunoglobulin heavy chain binding protein) and GRP94 (glucose-regulated protein 94), two chaperones whose binding is not carbohydrate-dependent. Our results suggest that calnexin and calreticulin, acting in ternary complexes with a large glycoprotein substrate such as Tg, might be engaged in the folding of distinct domains, and indicate that lumenal Ca(2+) strongly influences the folding of exportable glycoproteins, in part by regulating the balance of substrate binding to different molecular chaperone systems within the ER. PMID:12401114

  10. Novel germline mutations in the calreticulin gene: implications for the diagnosis of myeloproliferative neoplasms.

    PubMed

    Szuber, Natasha; Lamontagne, Bruno; Busque, Lambert

    2016-07-27

    Mutations in the calreticulin (CALR) gene are found in the majority of Janus kinase 2-negative myeloproliferative neoplasms MPN and, thus far, have exclusively been reported as acquired, somatic mutations. We assessed the mutational status of exon 9 of the CALR gene in 2000 blood samples submitted to our centre and identified 12 subjects (0.6%) harbouring distinctive CALR mutations, all with an allelic frequency of 50% and all involving indels occurring as multiples of 3 bp. Buccal cell samples obtained from these patients confirmed the germline nature of the mutations. Importantly, these germline mutations were not diagnostic of MPN. We thus report for the first time the identification and confirmation of germline mutations in CALR distinct from those somatic mutations that define classical MPN. The finding of a non-standard CALR mutation with an allelic frequency of 50% should raise suspicion of the possibility of a germline CALR mutation and these cases investigated further.

  11. Mutant calreticulin requires both its mutant C-terminus and the thrombopoietin receptor for oncogenic transformation

    PubMed Central

    Elf, Shannon; Abdelfattah, Nouran S.; Chen, Edwin; Perales-Patón, Javier; Rosen, Emily A.; Ko, Amy; Peisker, Fabian; Florescu, Natalie; Giannini, Silvia; Wolach, Ofir; Morgan, Elizabeth A.; Tothova, Zuzana; Losman, Julie-Aurore; Schneider, Rebekka K.; Al-Shahrour, Fatima; Mullally, Ann

    2016-01-01

    Somatic mutations in calreticulin (CALR) are present in approximately 40% of patients with myeloproliferative neoplasms (MPN) but the mechanism by which mutant CALR is oncogenic remains unclear. Here, we demonstrate that expression of mutant CALR alone is sufficient to engender MPN in mice and recapitulates the disease phenotype of CALR-mutant MPN patients. We further show that the thrombopoietin receptor, MPL is required for mutant CALR-driven transformation through JAK-STAT pathway activation, thus rendering mutant CALR-transformed hematopoietic cells sensitive to JAK2 inhibition. Finally, we demonstrate that the oncogenicity of mutant CALR is dependent on the positive electrostatic charge of the C-terminus of the mutant protein, which is necessary for physical interaction between mutant CALR and MPL. Together, our findings elucidate a novel paradigm of cancer pathogenesis and reveal how CALR mutations induce MPN. PMID:26951227

  12. Entamoeba histolytica calreticulin: an endoplasmic reticulum protein expressed by trophozoites into experimentally induced amoebic liver abscesses.

    PubMed

    González, Enrique; de Leon, Maria del Carmen García; Meza, Isaura; Ocadiz-Delgado, Rodolfo; Gariglio, Patricio; Silva-Olivares, Angelica; Galindo-Gómez, Silvia; Shibayama, Mineko; Morán, Patricia; Valadez, Alicia; Limón, Angelica; Rojas, Liliana; Hernández, Eric G; Cerritos, René; Ximenez, Cecilia

    2011-02-01

    Entamoeba histolytica calreticulin (EhCRT) is remarkably immunogenic in humans (90-100% of invasive amoebiasis patients). Nevertheless, the study of calreticulin in this protozoan is still in its early stages. The exact location, biological functions, and its role in pathogenesis are yet to be fully understood. The aim of the present work is to determine the location of EhCRT in virulent trophozoites in vivo and the expression of the Ehcrt gene during the development of experimentally induced amoebic liver abscesses (ALA) in hamsters. Antibodies against recombinant EhCRT were used for the immunolocalization of EhCRT in trophozoites through confocal microscopy; immunohistochemical assays were also performed on tissue sections of ALAs at different times after intrahepatic inoculation. The expression of the Ehcrt gene during the development of ALA was estimated through both in situ RT-PCR and real-time RT-PCR. Confocal assays of virulent trophozoites showed a distribution of EhCRT in the cytoplasmic vesicles of different sizes. Apparently, EhCRT is not exported into the hepatic tissue. Real-time RT-PCR demonstrated an over-expression of the Ehcrt gene at 30 min after trophozoite inoculation, reaching a peak at 1-2 h; thereafter, the expression fell sharply to its original levels. These results demonstrate for the first time in an in vivo model of ALA, the expression of Ehcrt gene in E. histolytica trophozoites and add evidence that support CRT as a resident protein of the ER in E. histolytica species. The in vivo experiments suggest that CRT may play an important role during the early stages of the host-parasite relationship, when the parasite is adapting to a new environment, although the protein seems to be constitutively synthesized. Moreover, trophozoites apparently do not export EhCRT into the hepatic tissue in ALA.

  13. Molecular cloning and characterization of wheat calreticulin (CRT) gene involved in drought-stressed responses.

    PubMed

    Jia, Xiao-Yun; Xu, Chong-Yi; Jing, Rui-Lian; Li, Run-Zhi; Mao, Xin-Guo; Wang, Ji-Ping; Chang, Xiao-Ping

    2008-01-01

    Calreticulin (CRT) is a highly conserved and ubiquitously expressed Ca(2+)-binding protein in multicellular eukaryotes. CRT plays a crucial role in many cellular processes including Ca(2+) storage and release, protein synthesis, and molecular chaperone activity. To elucidate the function of CRTs in plant responses against drought, a main abiotic stress limiting cereal crop production worldwide, a full-length cDNA encoding calreticulin protein namely TaCRT was isolated from wheat (Triticum aestivum L.). The deduced amino acid sequence of TaCRT shares high homology with other plant CRTs. Phylogenetic analysis indicates that TaCRT cDNA clone encodes a wheat CRT3 isoform. Southern analysis suggests that the wheat genome contains three copies of TaCRT. Subcellular locations of TaCRT were the cytoplasm and nucleus, evidenced by transient expression of GFP fused with TaCRT in onion epidermal cells. Enhanced accumulation of TaCRT transcript was observed in wheat seedlings in response to PEG-induced drought stress. To investigate further whether TaCRT is involved in the drought-stress response, transgenic plants were constructed. Compared to the wild-type and GFP-expressing plants, TaCRT-overexpressing tobacco (Nicotiana benthamiana) plants grew better and exhibited less wilt under the drought stress. Moreover, TaCRT-overexpressing plants exhibited enhanced drought resistance to water deficit, as shown by their capacity to maintain higher WUE (water use efficiency), WRA (water retention ability), RWC (relative water content), and lower MDR (membrane damaging ratio) (P < or = 0.01) under water-stress conditions. In conclusion, a cDNA clone encoding wheat CRT was successfully isolated and the results suggest that TaCRT is involved in the plant response to drought stress, indicating a potential in the transgenic improvements of plant water-stress.

  14. Calreticulin is highly expressed in pancreatic cancer stem-like cells.

    PubMed

    Matsukuma, Satoshi; Yoshimura, Kiyoshi; Ueno, Tomio; Oga, Atsunori; Inoue, Moeko; Watanabe, Yusaku; Kuramasu, Atsuo; Fuse, Masanori; Tsunedomi, Ryouichi; Nagaoka, Satoshi; Eguchi, Hidetoshi; Matsui, Hiroto; Shindo, Yoshitaro; Maeda, Noriko; Tokuhisa, Yoshihiro; Kawano, Reo; Furuya-Kondo, Tomoko; Itoh, Hiroshi; Yoshino, Shigefumi; Hazama, Shoichi; Oka, Masaaki; Nagano, Hiroaki

    2016-11-01

    Cancer stem-like cells (CSLCs) in solid tumors are thought to be resistant to conventional chemotherapy or molecular targeting therapy and to contribute to cancer recurrence and metastasis. In this study, we aimed to identify a biomarker of pancreatic CSLCs (P-CSLCs). A P-CSLC-enriched population was generated from pancreatic cancer cell lines using our previously reported method and its protein expression profile was compared with that of parental cells by 2-D electrophoresis and tandem mass spectrometry. The results indicated that a chaperone protein calreticulin (CRT) was significantly upregulated in P-CSLCs compared to parental cells. Flow cytometry analysis indicated that CRT was mostly localized to the surface of P-CSLCs and did not correlate with the levels of CD44v9, another P-CSLC biomarker. Furthermore, the side population in the CRT(high) /CD44v9(low) population was much higher than that in the CRT(low) /CD44v9(high) population. Calreticulin expression was also assessed by immunohistochemistry in pancreatic cancer tissues (n = 80) obtained after radical resection and was found to be associated with patients' clinicopathological features and disease outcomes in the Cox proportional hazard regression model. Multivariate analysis identified CRT as an independent prognostic factor for pancreatic cancer patients, along with age and postoperative therapy. Our results suggest that CRT can serve as a biomarker of P-CSLCs and a prognostic factor associated with poorer survival of pancreatic cancer patients. This novel biomarker can be considered as a therapeutic target for cancer immunotherapy.

  15. Cytokine, Antibody and Proliferative Cellular Responses Elicited by Taenia solium Calreticulin upon Experimental Infection in Hamsters

    PubMed Central

    Mendlovic, Fela; Cruz-Rivera, Mayra; Ávila, Guillermina; Vaughan, Gilberto; Flisser, Ana

    2015-01-01

    Taenia solium causes two diseases in humans, cysticercosis and taeniosis. Tapeworm carriers are the main risk factor for neurocysticercosis. Limited information is available about the immune response elicited by the adult parasite, particularly the induction of Th2 responses, frequently associated to helminth infections. Calreticulin is a ubiquitous, multifunctional protein involved in cellular calcium homeostasis, which has been suggested to play a role in the regulation of immune responses. In this work, we assessed the effect of recombinant T. solium calreticulin (rTsCRT) on the cytokine, humoral and cellular responses upon experimental infection in Syrian Golden hamsters (Mesocricetus auratus). Animals were infected with T. solium cysticerci and euthanized at different times after infection. Specific serum antibodies, proliferative responses in mesenteric lymph nodes and spleen cells, as well as cytokines messenger RNA (mRNA) were analyzed. The results showed that one third of the infected animals elicited anti-rTsCRT IgG antibodies. Interestingly, mesenteric lymph node (MLN) cells from either infected or non-infected animals did not proliferate upon in vitro stimulation with rTsCRT. Additionally, stimulation with a tapeworm crude extract resulted in increased expression of IL-4 and IL-5 mRNA. Upon stimulation, rTsCRT increased the expression levels of IL-10 in spleen and MLN cells from uninfected and infected hamsters. The results showed that rTsCRT favors a Th2-biased immune response characterized by the induction of IL-10 in mucosal and systemic lymphoid organs. Here we provide the first data on the cytokine, antibody and cellular responses to rTsCRT upon in vitro stimulation during taeniasis. PMID:25811778

  16. Cytokine, antibody and proliferative cellular responses elicited by Taenia solium calreticulin upon experimental infection in hamsters.

    PubMed

    Mendlovic, Fela; Cruz-Rivera, Mayra; Ávila, Guillermina; Vaughan, Gilberto; Flisser, Ana

    2015-01-01

    Taenia solium causes two diseases in humans, cysticercosis and taeniosis. Tapeworm carriers are the main risk factor for neurocysticercosis. Limited information is available about the immune response elicited by the adult parasite, particularly the induction of Th2 responses, frequently associated to helminth infections. Calreticulin is a ubiquitous, multifunctional protein involved in cellular calcium homeostasis, which has been suggested to play a role in the regulation of immune responses. In this work, we assessed the effect of recombinant T. solium calreticulin (rTsCRT) on the cytokine, humoral and cellular responses upon experimental infection in Syrian Golden hamsters (Mesocricetus auratus). Animals were infected with T. solium cysticerci and euthanized at different times after infection. Specific serum antibodies, proliferative responses in mesenteric lymph nodes and spleen cells, as well as cytokines messenger RNA (mRNA) were analyzed. The results showed that one third of the infected animals elicited anti-rTsCRT IgG antibodies. Interestingly, mesenteric lymph node (MLN) cells from either infected or non-infected animals did not proliferate upon in vitro stimulation with rTsCRT. Additionally, stimulation with a tapeworm crude extract resulted in increased expression of IL-4 and IL-5 mRNA. Upon stimulation, rTsCRT increased the expression levels of IL-10 in spleen and MLN cells from uninfected and infected hamsters. The results showed that rTsCRT favors a Th2-biased immune response characterized by the induction of IL-10 in mucosal and systemic lymphoid organs. Here we provide the first data on the cytokine, antibody and cellular responses to rTsCRT upon in vitro stimulation during taeniasis.

  17. Expression of the high capacity calcium-binding domain of calreticulin increases bioavailable calcium stores in plants

    NASA Technical Reports Server (NTRS)

    Wyatt, Sarah E.; Tsou, Pei-Lan; Robertson, Dominique; Brown, C. S. (Principal Investigator)

    2002-01-01

    Modulation of cytosolic calcium levels in both plants and animals is achieved by a system of Ca2+-transport and storage pathways that include Ca2+ buffering proteins in the lumen of intracellular compartments. To date, most research has focused on the role of transporters in regulating cytosolic calcium. We used a reverse genetics approach to modulate calcium stores in the lumen of the endoplasmic reticulum. Our goals were two-fold: to use the low affinity, high capacity Ca2+ binding characteristics of the C-domain of calreticulin to selectively increase Ca2+ storage in the endoplasmic reticulum, and to determine if those alterations affected plant physiological responses to stress. The C-domain of calreticulin is a highly acidic region that binds 20-50 moles of Ca2+ per mole of protein and has been shown to be the major site of Ca2+ storage within the endoplasmic reticulum of plant cells. A 377-bp fragment encoding the C-domain and ER retention signal from the maize calreticulin gene was fused to a gene for the green fluorescent protein and expressed in Arabidopsis under the control of a heat shock promoter. Following induction on normal medium, the C-domain transformants showed delayed loss of chlorophyll after transfer to calcium depleted medium when compared to seedlings transformed with green fluorescent protein alone. Total calcium measurements showed a 9-35% increase for induced C-domain transformants compared to controls. The data suggest that ectopic expression of the calreticulin C-domain increases Ca2+ stores, and that this Ca2+ reserve can be used by the plant in times of stress.

  18. Expression of the high capacity calcium-binding domain of calreticulin increases bioavailable calcium stores in plants

    NASA Technical Reports Server (NTRS)

    Wyatt, Sarah E.; Tsou, Pei-Lan; Robertson, Dominique; Brown, C. S. (Principal Investigator)

    2002-01-01

    Modulation of cytosolic calcium levels in both plants and animals is achieved by a system of Ca2+-transport and storage pathways that include Ca2+ buffering proteins in the lumen of intracellular compartments. To date, most research has focused on the role of transporters in regulating cytosolic calcium. We used a reverse genetics approach to modulate calcium stores in the lumen of the endoplasmic reticulum. Our goals were two-fold: to use the low affinity, high capacity Ca2+ binding characteristics of the C-domain of calreticulin to selectively increase Ca2+ storage in the endoplasmic reticulum, and to determine if those alterations affected plant physiological responses to stress. The C-domain of calreticulin is a highly acidic region that binds 20-50 moles of Ca2+ per mole of protein and has been shown to be the major site of Ca2+ storage within the endoplasmic reticulum of plant cells. A 377-bp fragment encoding the C-domain and ER retention signal from the maize calreticulin gene was fused to a gene for the green fluorescent protein and expressed in Arabidopsis under the control of a heat shock promoter. Following induction on normal medium, the C-domain transformants showed delayed loss of chlorophyll after transfer to calcium depleted medium when compared to seedlings transformed with green fluorescent protein alone. Total calcium measurements showed a 9-35% increase for induced C-domain transformants compared to controls. The data suggest that ectopic expression of the calreticulin C-domain increases Ca2+ stores, and that this Ca2+ reserve can be used by the plant in times of stress.

  19. Calreticulin contributes to C1q-dependent recruitment of microglia in the leech Hirudo medicinalis following a CNS injury

    PubMed Central

    Le Marrec-Croq, Françoise; Bocquet-Garcon, Annelise; Vizioli, Jacopo; Vancamp, Christelle; Drago, Francesco; Franck, Julien; Wisztorski, Maxence; Salzet, Michel; Sautiere, Pierre-Eric; Lefebvre, Christophe

    2014-01-01

    Background The medicinal leech is considered as a complementary and appropriate model to study immune functions in the central nervous system (CNS). In a context in which an injured leech’s CNS can naturally restore normal synaptic connections, the accumulation of microglia (immune cells of the CNS that are exclusively resident in leeches) has been shown to be essential at the lesion to engage the axonal sprouting. HmC1q (Hm for Hirudo medicinalis) possesses chemotactic properties that are important in the microglial cell recruitment by recognizing at least a C1q binding protein (HmC1qBP alias gC1qR). Material/Methods Recombinant forms of C1q were used in affinity purification and in vitro chemotaxis assays. Anti-calreticulin antibodies were used to neutralize C1q-mediated chemotaxis and locate the production of calreticulin in leech CNS. Results A newly characterized leech calreticulin (HmCalR) has been shown to interact with C1q and participate to the HmC1q-dependent microglia accumulation. HmCalR, which has been detected in only some microglial cells, is consequently a second binding protein for HmC1q, allowing the chemoattraction of resident microglia in the nerve repair process. Conclusions These data give new insight into calreticulin/C1q interaction in an immune function of neuroprotection, suggesting another molecular target to use in investigation of microglia reactivity in a model of CNS injury. PMID:24747831

  20. Proteomic identification of calcium-binding chaperone calreticulin as a potential mediator for the neuroprotective and neuritogenic activities of fruit-derived glycoside amygdalin.

    PubMed

    Cheng, Yuanyuan; Yang, Chuanbin; Zhao, Jia; Tse, Hung Fat; Rong, Jianhui

    2015-02-01

    Amygdalin is a fruit-derived glycoside with the potential for treating neurodegenerative diseases. This study was designed to identify the neuroprotective and neuritogenic activities of amygdalin. We initially demonstrated that amygdalin enhanced nerve growth factor (NGF)-induced neuritogenesis and attenuated 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in rat dopaminergic PC12 cells. To define protein targets for amygdalin, we selected a total of 11 mostly regulated protein spots from two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels for protein identification by matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry. We verified the effect of amygdalin on six representative proteins (i.e., calreticulin, Hsp90β, Grp94, 14-3-3η, 14-3-3ζ/δ and Rab GDI-α) for biological relevance to neuronal survival and differentiation. Calcium-binding chaperone calreticulin is of special interest for its activities to promote folding, oligomeric assembly and quality control of proteins that modulate cell survival and differentiation. We transiently knocked down calreticulin expression by specific siRNA and studied its effect on the neuroprotective and neuritogenic activities of amygdalin. We found that amygdalin failed to enhance NGF-induced neuritogenesis in calreticulin-siRNA transfected cells. On the other hand, amygdalin rescued 6-OHDA-induced loss of calreticulin expression. We also found that amygdalin increased the intracellular calcium concentration possibly via inducing calreticulin. Collectively, our results demonstrated the role of calreticulin in mediating the neuroprotective and neuritogenic activities of amygdalin.

  1. Identification and characterization of structural domains of human ERp57: association with calreticulin requires several domains.

    PubMed

    Silvennoinen, Laura; Myllyharju, Johanna; Ruoppolo, Margherita; Orrù, Stefania; Caterino, Marianna; Kivirikko, Kari I; Koivunen, Peppi

    2004-04-02

    The amino acid sequence of ERp57, which functions in the endoplasmic reticulum together with the lectins calreticulin and calnexin to achieve folding of newly synthesized glycoproteins, is highly similar to that of protein disulfide isomerase (PDI), but they have their own distinct roles in protein folding. We have characterized the domain structure of ERp57 by limited proteolysis and N-terminal sequencing and have found it to be similar but not identical to that of PDI. ERp57 had three major protease-sensitive regions, the first of which was located between residues 120 and 150, the second between 201 and 215, and the third between 313 and 341, the data thus being consistent with a four-domain structure abb'a'. Recombinant expression in Escherichia coli was used to verify the domain boundaries. Each single domain and a b'a' double domain could be produced in the form of soluble, folded polypeptides, as verified by circular dichroism spectra and urea gradient gel electrophoresis. When the ability of ERp57 and its a and a' domains to fold denatured RNase A was studied by electrospray mass analyses, ERp57 markedly enhanced the folding rate at early time points, although less effectively than PDI, but was an ineffective catalyst of the overall process. The a and a' domains produced only minor, if any, increases in the folding rate at the early stages and no increase at the late stages. Interaction of the soluble ERp57 domains with the P domain of calreticulin was studied by chemical cross-linking in vitro. None of the single ERp57 domains nor the b'a' double domain could be cross-linked to the P domain, whereas cross-linking was obtained with a hybrid ERpabb'PDIa'c polypeptide but not with ERpabPDIb'a'c, indicating that multiple domains are involved in this protein-protein interaction and that the b' domain of ERp57 cannot be replaced by that of PDI.

  2. Calnexin and calreticulin bind to enzymically active tissue-type plasminogen activator during biosynthesis and are not required for folding to the native conformation.

    PubMed Central

    Allen, S; Bulleid, N J

    1997-01-01

    The roles of the endoplasmic-reticulum lectins calnexin and calreticulin in the folding of tissue-type plasminogen activator (tPA) have been investigated using an in vitro translation system that reconstitutes these processes as they would occur in the intact cell. Using co-immunoprecipitation of newly synthesized tPA with antibodies to calnexin and calreticulin, it was demonstrated that the interaction of tPA with both lectins was dependent upon tPA glycosylation and glucosidase trimming. When tPA was synthesized in the presence of semi-permeabilized cells under conditions preventing complex formation with calnexin and calreticulin, the translation product had a specific plasminogenolytic activity identical with that when synthesized under conditions permitting interactions with both lectins. Furthermore, complexes of tPA bound to calnexin and calreticulin were shown to be enzymically active. These results demonstrate that calnexin and calreticulin can form a stable interaction with correctly folded tPA; however, such interactions are not required for the synthesis of enzymically active tPA. PMID:9359841

  3. Plasmodesmata without callose and calreticulin in higher plants - open channels for fast symplastic transport?

    PubMed

    Demchenko, Kirill N; Voitsekhovskaja, Olga V; Pawlowski, Katharina

    2014-01-01

    Plasmodesmata (PD) represent membrane-lined channels that link adjacent plant cells across the cell wall. PD of higher plants contain a central tube of endoplasmic reticulum (ER) called desmotubule. Membrane and lumen proteins seem to be able to move through the desmotubule, but most transport processes through PD occur through the cytoplasmic annulus (Brunkard etal., 2013). Calreticulin (CRT), a highly conserved Ca(2+)-binding protein found in all multicellular eukaryotes, predominantly located in the ER, was shown to localize to PD, though not all PD accumulate CRT. In nitrogen-fixing actinorhizal root nodules of the Australian tree Casuarina glauca, the primary walls of infected cells containing the microsymbiont become lignified upon infection. TEM analysis of these nodules showed that during the differentiation of infected cells, PD connecting infected cells, and connecting infected and adjacent uninfected cells, were reduced in number as well as diameter (Schubert etal., 2013). In contrast with PD connecting young infected cells, and most PD connecting mature infected and adjacent uninfected cells, PD connecting mature infected cells did not accumulate CRT. Furthermore, as shown here, these PD were not associated with callose, and based on their diameter, they probably had lost their desmotubules. We speculate that either this is a slow path to PD degradation, or that the loss of callose accumulation and presumably also desmotubules leads to the PD becoming open channels and improves metabolite exchange between cells.

  4. Role of calreticulin mutations in the aetiological diagnosis of splanchnic vein thrombosis.

    PubMed

    Turon, Fanny; Cervantes, Francisco; Colomer, Dolors; Baiges, Anna; Hernández-Gea, Virginia; Garcia-Pagán, Juan Carlos

    2015-01-01

    Myeloproliferative neoplasms are the most common aetiological cause of splanchnic vein thrombosis (SVT). In these patients, the JAK2V617F mutation has facilitated the diagnosis of an underlying myeloproliferative neoplasm (MPN). Recently, somatic mutations of the calreticulin (CALR) gene have been identified in MPN patients lacking the JAK2 mutation. The aim of the present study was to ascertain whether CALR mutations could also play a role in the diagnosis of masked MPN in SVT. We included 209 patients with SVT (140 with PVT and 69 with Budd-Chiari syndrome) who had a complete aetiological diagnostic work-out. They were investigated for CALR mutations. CALR mutations were found in 4 of the 209 patients (1.9%). They represented 5.4% of patients with an underlying MPN of whom all had already been diagnosed with a MPN using conventional criteria including bone marrow biopsy findings. In the screening of underlying MPNs in patients with SVT, given its high frequency in these disorders, the JAK2 mutation must be evaluated first and, if negative, CALR mutations should also be investigated. This approach would increase the diagnostic yield of masked MPNs by reducing the need for additional studies. Copyright © 2014 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

  5. The Mutation Profile of Calreticulin in Patients with Myeloproliferative Neoplasms and Acute Leukemia

    PubMed Central

    Wang, Jingyi; Hao, Jianguo; He, Na; Ji, Chunyan; Ma, Daoxin

    2016-01-01

    Objective: Calreticulin (CALR) plays important roles in cell proliferation, apoptosis, and immune responses. CALR mutations were described recently in Janus kinase 2 gene (JAK2)-negative or MPL-negative primary myelofibrosis (PMF) and essential thrombocythemia (ET) patients. CALR trails JAK2 as the second most mutated gene in myeloproliferative neoplasms (MPNs). However, little is known about CALR mutation in Chinese patients with leukemia. In the present study, a cohort of 305 Chinese patients with hematopoietic neoplasms was screened for CALR mutations, with the aim of uncovering the frequency of CALR mutations in leukemia and MPNs. Materials and Methods: Polymerase chain reaction and direct sequencing were performed to analyze mutations of CALR in 305 patients with hematopoietic malignancies, including 135 acute myeloid leukemia patients, 57 acute lymphoblastic leukemia patients, and 113 MPN patients. Results: CALR mutations were found in 10.6% (12 of 113) of samples from patients with MPNs. CALR mutations were determined in 11.3% (6 of 53), 21.7% (5 of 23), and 9.1% (1/11) of patients with ET, PMF, and unclassifiable MPN, respectively. Conclusion: We showed that MPN patients carrying CALR mutations presented with higher platelet counts and lower hemoglobin levels compared to those with mutated JAK2. However, all of the leukemia patients had negative results for CALR mutations. PMID:26377485

  6. Activation of the thrombopoietin receptor by mutant calreticulin in CALR-mutant myeloproliferative neoplasms.

    PubMed

    Araki, Marito; Yang, Yinjie; Masubuchi, Nami; Hironaka, Yumi; Takei, Hiraku; Morishita, Soji; Mizukami, Yoshihisa; Kan, Shin; Shirane, Shuichi; Edahiro, Yoko; Sunami, Yoshitaka; Ohsaka, Akimichi; Komatsu, Norio

    2016-03-10

    Recurrent somatic mutations of calreticulin (CALR) have been identified in patients harboring myeloproliferative neoplasms; however, their role in tumorigenesis remains elusive. Here, we found that the expression of mutant but not wild-type CALR induces the thrombopoietin (TPO)-independent growth of UT-7/TPO cells. We demonstrated that c-MPL, the TPO receptor, is required for this cytokine-independent growth of UT-7/TPO cells. Mutant CALR preferentially associates with c-MPL that is bound to Janus kinase 2 (JAK2) over the wild-type protein. Furthermore, we demonstrated that the mutant-specific carboxyl terminus portion of CALR interferes with the P-domain of CALR to allow the N-domain to interact with c-MPL, providing an explanation for the gain-of-function property of mutant CALR. We showed that mutant CALR induces the phosphorylation of JAK2 and its downstream signaling molecules in UT-7/TPO cells and that this induction was blocked by JAK2 inhibitor treatment. Finally, we demonstrated that c-MPL is required for TPO-independent megakaryopoiesis in induced pluripotent stem cell-derived hematopoietic stem cells harboring the CALR mutation. These findings imply that mutant CALR activates the JAK2 downstream pathway via its association with c-MPL. Considering these results, we propose that mutant CALR promotes myeloproliferative neoplasm development by activating c-MPL and its downstream pathway.

  7. Molecular cloning and characterization of sea bass (Dicentrarchus labrax, L.) calreticulin.

    PubMed

    Pinto, Rute D; Moreira, Ana R; Pereira, Pedro J B; dos Santos, Nuno M S

    2013-06-01

    Mammalian calreticulin (CRT) is a key molecular chaperone and regulator of Ca(2+) homeostasis in endoplasmic reticulum (ER), also being implicated in a variety of physiological/pathological processes outside the ER. Importantly, it is involved in assembly of MHC class I molecules. In this work, sea bass (Dicentrarchus labrax) CRT (Dila-CRT) gene and cDNA have been isolated and characterized. The mature protein retains two conserved motifs, three structural/functional domains (N, P and C), three type 1 and 2 motifs repeated in tandem, a conserved pair of cysteines and ER-retention motif. It is a single-copy gene composed of 9 exons. Dila-CRT three-dimensional homology models are consistent with the structural features described for mammalian molecules. Together, these results are supportive of a highly conserved structure of CRT through evolution. Moreover, the present data provides information that will allow further studies on sea bass CRT involvement in immunity and in particular class I antigen presentation. Copyright © 2013 Elsevier Ltd. All rights reserved.

  8. Reduction of endoplasmic reticulum Ca2+ levels favors plasma membrane surface exposure of calreticulin.

    PubMed

    Tufi, R; Panaretakis, T; Bianchi, K; Criollo, A; Fazi, B; Di Sano, F; Tesniere, A; Kepp, O; Paterlini-Brechot, P; Zitvogel, L; Piacentini, M; Szabadkai, G; Kroemer, G

    2008-02-01

    Some chemotherapeutic agents can elicit apoptotic cancer cell death, thereby activating an anticancer immune response that influences therapeutic outcome. We previously reported that anthracyclins are particularly efficient in inducing immunogenic cell death, correlating with the pre-apoptotic exposure of calreticulin (CRT) on the plasma membrane surface of anthracyclin-treated tumor cells. Here, we investigated the role of cellular Ca(2+) homeostasis on CRT exposure. A neuroblastoma cell line (SH-SY5Y) failed to expose CRT in response to anthracyclin treatment. This defect in CRT exposure could be overcome by the overexpression of Reticulon-1C, a manipulation that led to a decrease in the Ca(2+) concentration within the endoplasmic reticulum lumen. The combination of Reticulon-1C expression and anthracyclin treatment yielded more pronounced endoplasmic reticulum Ca(2+) depletion than either of the two manipulations alone. Chelation of intracellular (and endoplasmic reticulum) Ca(2+), targeted expression of the ligand-binding domain of the IP(3) receptor and inhibition of the sarco-endoplasmic reticulum Ca(2+)-ATPase pump reduced endoplasmic reticulum Ca(2+) load and promoted pre-apoptotic CRT exposure on the cell surface, in SH-SY5Y and HeLa cells. These results provide evidence that endoplasmic reticulum Ca(2+) levels control the exposure of CRT.

  9. Anti-calreticulin immunoglobulin A (IgA) antibodies in refractory coeliac disease.

    PubMed

    Sánchez, D; Palová-Jelínková, L; Felsberg, J; Simsová, M; Pekáriková, A; Pecharová, B; Swoboda, I; Mothes, T; Mulder, C J J; Benes, Z; Tlaskalová-Hogenová, H; Tucková, L

    2008-09-01

    Refractory coeliac disease (RCD) is a very rare and dangerous form of CD, in which gluten-free diet loses its therapeutic effect and the damage of intestinal mucosa persists. Because of the adherence to the diet, serological markers of CD [immunoglobulin A (IgA) antibodies against gliadin, tissue transglutaminase (tTG) and endomysium] are often missing in RCD patients. We found substantially elevated levels of IgA anti-calreticulin (CRT) antibodies in the sera of almost all RCD patients tested. These sera were negative for IgA antibodies to gliadin and tTG and only some of them showed IgA antibodies to enterocytes. Analysis of patients' IgA reactivity to CRT fragments (quarters and halves) by Western blotting revealed differences in the specificity of IgA antibodies between RCD and CD patients. We therefore used the Pepscan technique with synthetic overlapping decapeptides of CRT to characterize antigenic epitopes recognized by serum IgA antibodies of RCD patients. Employing this method we demonstrated several dominant antigenic epitopes recognized by IgA antibodies of RCD patients on the CRT molecule. Epitope GVTKAAEKQMKD was recognized predominantly by serum IgA of RCD patients. Our results suggest that testing for serum IgA antibodies against CRT and its selected peptide could be a very useful tool in RCD differential diagnosis.

  10. Taenia solium: immune response against oral or systemic immunization with purified recombinant calreticulin in mice.

    PubMed

    Fonseca-Coronado, Salvador; Ruiz-Tovar, Karina; Pérez-Tapia, Mayra; Mendlovic, Fela; Flisser, Ana

    2011-01-01

    Recombinant functional Taenia solium calreticulin (rTsCRT) confers different degrees of protection in the experimental model of intestinal taeniosis in hamsters. The aim of this study was to evaluate the immune response induced after oral or systemic immunization with an electroeluted rTsCRT in BALB/c mice. Oral immunization elicited high fecal IgA and the production of IL-4 and IL-5 by mesenteric lymph node cells after in vitro stimulation with rTSCRT, indicating a Th2 response. Mice subcutaneously immunized produced high amounts of serum IgG, being IgG1 (Th2-related) the predominant isotype, while in vitro stimulated spleen cells synthesized IL-4, IL-5 and also IFN-γ, indicating a mixed Th1/Th2 cellular response after systemic immunization. Our data show that purified rTsCRT induces polarized Th2 responses after oral immunization of mice, a common characteristic of protective immunity against helminths and, consequently, a desirable hallmark in the search for a vaccine.

  11. Overexpression of a Triticum aestivum Calreticulin gene (TaCRT1) Improves Salinity Tolerance in Tobacco

    PubMed Central

    Song, Min; Wang, Yun; Xu, Wenqi; Wu, Lintao; Wang, Hancheng; Ma, Zhengqiang

    2015-01-01

    Calreticulin (CRT) is a highly conserved and abundant multifunctional protein that is encoded by a small gene family and is often associated with abiotic/biotic stress responses in plants. However, the roles played by this protein in salt stress responses in wheat (Triticum aestivum) remain obscure. In this study, three TaCRT genes were identified in wheat and named TaCRT1, TaCRT2 and TaCRT3-1 based on their sequence characteristics and their high homology to other known CRT genes. Quantitative real-time PCR expression data revealed that these three genes exhibit different expression patterns in different tissues and are strongly induced under salt stress in wheat. The calcium-binding properties of the purified recombinant TaCRT1 protein were determined using a PIPES/Arsenazo III analysis. TaCRT1 gene overexpression in Nicotiana tabacum decreased salt stress damage in transgenic tobacco plants. Physiological measurements indicated that transgenic tobacco plants showed higher activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) than non-transgenic tobacco under normal growth conditions. Interestingly, overexpression of the entire TaCRT1 gene or of partial TaCRT1 segments resulted in significantly higher tolerance to salt stress in transgenic plants compared with their WT counterparts, thus revealing the essential role of the C-domain of TaCRT1 in countering salt stress in plants. PMID:26469859

  12. Is the Antitumor Property of Trypanosoma cruzi Infection Mediated by Its Calreticulin?

    PubMed Central

    Ramírez-Toloza, Galia; Abello, Paula; Ferreira, Arturo

    2016-01-01

    Eight to 10 million people in 21 endemic countries are infected with Trypanosoma cruzi. However, only 30% of those infected develop symptoms of Chagas’ disease, a chronic, neglected tropical disease worldwide. Similar to other pathogens, T. cruzi has evolved to resist the host immune response. Studies, performed 80 years ago in the Soviet Union, proposed that T. cruzi infects tumor cells with similar capacity to that displayed for target tissues such as cardiac, aortic, or digestive. An antagonistic relationship between T. cruzi infection and cancer development was also proposed, but the molecular mechanisms involved have remained largely unknown. Probably, a variety of T. cruzi molecules is involved. This review focuses on how T. cruzi calreticulin (TcCRT), exteriorized from the endoplasmic reticulum, targets the first classical complement component C1 and negatively regulates the classical complement activation cascade, promoting parasite infectivity. We propose that this C1-dependent TcCRT-mediated virulence is critical to explain, at least an important part, of the parasite capacity to inhibit tumor development. We will discuss how TcCRT, by directly interacting with venous and arterial endothelial cells, inhibits angiogenesis and tumor growth. Thus, these TcCRT functions not only illustrate T. cruzi interactions with the host immune defensive strategies, but also illustrate a possible co-evolutionary adaptation to privilege a prolonged interaction with its host. PMID:27462315

  13. Serum calreticulin as a novel biomarker of juvenile idiopathic arthritis disease activity

    PubMed Central

    Hashaad, Nashwa Ismail; Fawzy, Rasha Mohamed; Elazem, Abeer Ahmed Abo; Youssef, Mohamed Ibrahim

    2017-01-01

    Objective This study aimed to investigate the relations between calreticulin (CRT) serum level and both disease activity and severity parameters in juvenile idiopathic arthritis (JIA). Material and Methods In this study, 60 children with JIA and 50 age-and-sex-matched healthy subjects were enrolled. The assessment of the disease activity was done using juvenile arthritis disease activity score 27 (JADAS-27). The assessment of disease severity was done via gray-scale ultrasonography (US) and power Doppler US (PDUS). Enzyme-linked immunosorbent assay (ELISA) was used to assay the serum level of human CRT. Results The mean serum CRT levels in JIA patients was 8.6±1.2 ng/mL and showed a highly significant increase (p=0.001) as compared to the mean serum levels in the controls (5.02±0.77 ng/mL). There were statistically significant positive correlations between the serum CRT levels and disease duration, tender joint count, swollen joint count, visual analog scale, erythrocyte sedimentation rate, JADAS-27, C-reactive protein, rheumatoid factor titer, and ultrasonographic grading for synovitis and neovascularization. Conclusion Elevated serum CRT levels in JIA patients and its correlations with JIA disease activity and severity parameters signified that CRT might be used as a novel biomarker for disease activity and severity in JIA. PMID:28293448

  14. The Thrombopoietin Receptor: Structural Basis of Traffic and Activation by Ligand, Mutations, Agonists, and Mutated Calreticulin

    PubMed Central

    Varghese, Leila N.; Defour, Jean-Philippe; Pecquet, Christian; Constantinescu, Stefan N.

    2017-01-01

    A well-functioning hematopoietic system requires a certain robustness and flexibility to maintain appropriate quantities of functional mature blood cells, such as red blood cells and platelets. This review focuses on the cytokine receptor that plays a significant role in thrombopoiesis: the receptor for thrombopoietin (TPO-R; also known as MPL). Here, we survey the work to date to understand how this receptor functions at a molecular level throughout its lifecycle, from traffic to the cell surface, dimerization and binding cognate cytokine via its extracellular domain, through to its subsequent activation of associated Janus kinases and initiation of downstream signaling pathways, as well as the regulation of these processes. Atomic level resolution structures of TPO-R have remained elusive. The identification of disease-causing mutations in the receptor has, however, offered some insight into structure and function relationships, as has artificial means of receptor activation, through TPO mimetics, transmembrane-targeting receptor agonists, and engineering in dimerization domains. More recently, a novel activation mechanism was identified whereby mutated forms of calreticulin form complexes with TPO-R via its extracellular N-glycosylated domain. Such complexes traffic pathologically in the cell and persistently activate JAK2, downstream signal transducers and activators of transcription (STATs), and other pathways. This pathologic TPO-R activation is associated with a large fraction of human myeloproliferative neoplasms. PMID:28408900

  15. Detection of elevated antibody against calreticulin by ELISA in aged cynomolgus monkey plasma.

    PubMed

    Higashino, Atsunori; Kageyama, Takashi; Kantha, Sachi Sri; Terao, Keiji

    2011-02-01

    Calreticulin (Crt) is a molecular chaperone ubiquitously present in the endoplasmic reticulum. In non-human primates, age-related occurrence of anti-Crt antibody has not been reported. We developed an ELISA assay for an anti-Crt antibody and determined the age-related increase in the levels of anti-Crt antibody in three groups of cynomolgus monkeys: juvenile (1.5 yr), young adults (5-10 yr) and aged adults (20-34 yr). Mean ± SD auto-antibody levels at 450 nm in juvenile, young adults and aged groups were 0.23 ± 0.18, 0.30 ± 0.28, and 0.55 ± 0.33, respectively. Statistically significant differences were noted in the autoantibody levels to Crt among the aged group and juvenile or young adults. This is the first report to demonstrate the expression of anti-Crt autoantibody in aged monkeys and indicates that cynomologous monkeys may serve as an appropriate nonhuman primate model for studies of age-related alteration of immune function in elderly humans. Though preliminary, this finding merits further investigation to determine the relationship between immunosenescence and expression of antibodies to Crt.

  16. Calreticulin Release at an Early Stage of Death Modulates the Clearance by Macrophages of Apoptotic Cells

    PubMed Central

    Osman, Rim; Tacnet-Delorme, Pascale; Kleman, Jean-Philippe; Millet, Arnaud; Frachet, Philippe

    2017-01-01

    Calreticulin (CRT) is a well-known “eat-me” signal harbored by dying cells participating in their recognition by phagocytes. CRT is also recognized to deeply impact the immune response to altered self-cells. In this study, we focus on the role of the newly exposed CRT following cell death induction. We show that if CRT increases at the outer face of the plasma membrane and is well recognized by C1q even when phosphatidylserine is not yet detected, CRT is also released in the surrounding milieu and is able to interact with phagocytes. We observed that exogenous CRT is endocytosed by THP1 macrophages through macropinocytosis and that internalization is associated with a particular phenotype characterized by an increase of cell spreading and migration, an upregulation of CD14, an increase of interleukin-8 release, and a decrease of early apoptotic cell uptake. Importantly, CRT-induced pro-inflammatory phenotype was confirmed on human monocytes-derived macrophages by the overexpression of CD40 and CD274, and we found that monocyte-derived macrophages exposed to CRT display a peculiar polarization notably associated with a downregulation of the histocompatibility complex of class II molecules hampering its description through the classical M1/M2 dichotomy. Altogether our results highlight the role of soluble CRT with strong possible consequences on the macrophage-mediated immune response to dying cell. PMID:28878781

  17. Phylogenetic conservation of the preapoptotic calreticulin exposure pathway from yeast to mammals.

    PubMed

    Madeo, Frank; Durchschlag, Michael; Kepp, Oliver; Panaretakis, Theocharis; Zitvogel, Laurence; Fröhlich, Kai-Uwe; Kroemer, Guido

    2009-02-15

    The pre-apoptotic exposure of calreticulin (CRT) on the cell surface determines the efficient engulfment of mouse or human tumor cells by antigen-presenting dendritic cells. CRT exposure is rapidly induced by anthracyclins and ionizing irradiation and follows a complex signal transduction pathway that is interrupted by depletion of PERK, caspase-8, BAP31, Bax, Bak or SNAREs, as well as by knock-in mutation of eIF2alpha (to make it non-phosphorylable by PERK) or BAP31 (to render it uncleavable by caspase-8). Here, we show that yeast (Saccharomyces cerevisiae) can expose the CRT orthologue CNE1 on the surface in response to cell death induced by the anthracylin mitoxantrone (MTX). This MTX-triggered CNE1 translocation is abolished by knockout of the yeast orthologues of PERK (Gcn2), BAP31 (Yet3) and SNAREs (Nyv1, Sso1). Altogether, our data point to the existence of an ancestral and cell death-related CRT exposure pathway with conserved elements shared between unicellular fungi and mammals.

  18. Mechanisms of pre-apoptotic calreticulin exposure in immunogenic cell death.

    PubMed

    Panaretakis, Theocharis; Kepp, Oliver; Brockmeier, Ulf; Tesniere, Antoine; Bjorklund, Ann-Charlotte; Chapman, Daniel C; Durchschlag, Michael; Joza, Nicholas; Pierron, Gérard; van Endert, Peter; Yuan, Junying; Zitvogel, Laurence; Madeo, Frank; Williams, David B; Kroemer, Guido

    2009-03-04

    Dying tumour cells can elicit a potent anticancer immune response by exposing the calreticulin (CRT)/ERp57 complex on the cell surface before the cells manifest any signs of apoptosis. Here, we enumerate elements of the pathway that mediates pre-apoptotic CRT/ERp57 exposure in response to several immunogenic anticancer agents. Early activation of the endoplasmic reticulum (ER)-sessile kinase PERK leads to phosphorylation of the translation initiation factor eIF2alpha, followed by partial activation of caspase-8 (but not caspase-3), caspase-8-mediated cleavage of the ER protein BAP31 and conformational activation of Bax and Bak. Finally, a pool of CRT that has transited the Golgi apparatus is secreted by SNARE-dependent exocytosis. Knock-in mutation of eIF2alpha (to make it non-phosphorylatable) or BAP31 (to render it uncleavable), depletion of PERK, caspase-8, BAP31, Bax, Bak or SNAREs abolished CRT/ERp57 exposure induced by anthracyclines, oxaliplatin and ultraviolet C light. Depletion of PERK, caspase-8 or SNAREs had no effect on cell death induced by anthracyclines, yet abolished the immunogenicity of cell death, which could be restored by absorbing recombinant CRT to the cell surface.

  19. Immunogenic tumor cell death for optimal anticancer therapy: the calreticulin exposure pathway.

    PubMed

    Zitvogel, Laurence; Kepp, Oliver; Senovilla, Laura; Menger, Laurie; Chaput, Nathalie; Kroemer, Guido

    2010-06-15

    In response to some chemotherapeutic agents such as anthracyclines and oxaliplatin, cancer cells undergo immunogenic apoptosis, meaning that their corpses are engulfed by dendritic cells and that tumor cell antigens are presented to tumor-specific CD8(+) T cells, which then control residual tumor cells. One of the peculiarities of immunogenic apoptosis is the early cell surface exposure of calreticulin (CRT), a protein that usually resides in the lumen of the endoplasmic reticulum (ER). When elicited by anthracyclines or oxaliplatin, the CRT exposure pathway is activated by pre-apoptotic ER stress and the phosphorylation of the eukaryotic translation initiation factor eIF2alpha by the kinase PERK, followed by caspase-8-mediated proteolysis of the ER-sessile protein BAP31, activation of the pro-apoptotic proteins Bax and Bak, anterograde transport of CRT from the ER to the Golgi apparatus and exocytosis of CRT-containing vesicles, finally resulting in CRT translocation onto the plasma membrane surface. Interruption of this complex pathway abolishes CRT exposure, annihilates the immunogenicity of apoptosis, and reduces the immune response elicited by anticancer chemotherapies. We speculate that human cancers that are incapable of activating the CRT exposure pathway are refractory to the immune-mediated component of anticancer therapies.

  20. Calreticulin associates with non-HLA-A,-B class I proteins in the human choriocarcinoma cell lines JEG-3 and BeWo.

    PubMed Central

    Wainwright, S D; Simpson, K L; Holmes, C H

    1998-01-01

    Human placental trophoblast expresses as unusual repertoire of major histocompatibility complex (MHC) class I products that appears to reflect the unique role of this epithelium in mediating feto-maternal relations during pregnancy. Trophoblast is devoid of human leucocyte antigen (HLA)-A,-B antigens but can express one or more non-HLA-A,-B class I proteins. The human choriocarcinoma cell lines JEG-3, BeWo and JAR are widely used as models to study trophoblast. During attempts to isolate non-HLA-A,-B class I from JEG-3 and BeWo by immunoaffinity chromatography using a monoclonal antibody to beta 2-microglobulin we observed a 55,000 MW protein co-purifying with class I. N-terminal amino acid sequencing and immunoblotting using a specific antiserum identified this product as calreticulin, a molecule recently shown to be involved in the assembly of classical class I in human B-lymphoblastoid cells. In our hands JEG-3 and BeWo were found to express 45,000 MW non-HLA-A,-B class I proteins while the 40,000 MW HLA-G product was identified only in JEG-3. Our data suggest that calreticulin associates with non-HLA-A,-B class I heterodimers and with free 45,000 MW non-HLA-A,-B class I H chains in JEG-3. JAR was found to be devoid of detectable class I H chains but contained beta 2-microglobulin and calreticulin. However, calreticulin-beta 2-microglobulin complexes were not detected in JAR. Calreticulin and class I were apparently co-localized within the endoplasmic reticulum of JEG-3 cells whereas only class I was expressed at the cell surface. These studies demonstrate that calreticulin is associated with non-HLA-A,-B class I products in human choriocarcinoma cells. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 PMID:9640257

  1. Label-free proteomics identifies Calreticulin and GRP75/Mortalin as peripherally accessible protein biomarkers for spinal muscular atrophy

    PubMed Central

    2013-01-01

    Background Spinal muscular atrophy (SMA) is a neuromuscular disease resulting from mutations in the survival motor neuron 1 (SMN1) gene. Recent breakthroughs in preclinical research have highlighted several potential novel therapies for SMA, increasing the need for robust and sensitive clinical trial platforms for evaluating their effectiveness in human patient cohorts. Given that most clinical trials for SMA are likely to involve young children, there is a need for validated molecular biomarkers to assist with monitoring disease progression and establishing the effectiveness of therapies being tested. Proteomics technologies have recently been highlighted as a potentially powerful tool for such biomarker discovery. Methods We utilized label-free proteomics to identify individual proteins in pathologically-affected skeletal muscle from SMA mice that report directly on disease status. Quantitative fluorescent western blotting was then used to assess whether protein biomarkers were robustly changed in muscle, skin and blood from another mouse model of SMA, as well as in a small cohort of human SMA patient muscle biopsies. Results By comparing the protein composition of skeletal muscle in SMA mice at a pre-symptomatic time-point with the muscle proteome at a late-symptomatic time-point we identified increased expression of both Calreticulin and GRP75/Mortalin as robust indicators of disease progression in SMA mice. We report that these protein biomarkers were consistently modified in different mouse models of SMA, as well as across multiple skeletal muscles, and were also measurable in skin biopsies. Furthermore, Calreticulin and GRP75/Mortalin were measurable in muscle biopsy samples from human SMA patients. Conclusions We conclude that label-free proteomics technology provides a powerful platform for biomarker identification in SMA, revealing Calreticulin and GRP75/Mortalin as peripherally accessible protein biomarkers capable of reporting on disease progression in

  2. Novel distribution of calreticulin to cardiomyocyte mitochondria and its increase in a rat model of dilated cardiomyopathy

    SciTech Connect

    Zhang, Ming; Wei, Jin; Li, Yali; Shan, Hu; Yan, Rui; Lin, Lin; Zhang, Qiuhong; Xue, Jiahong

    2014-06-20

    Highlights: • Calreticulin can also be found in cardiomyocyte mitochondria. • The mitochondrial content of calreticulin is increased in DCM hearts. • Increased expression of mitochondrial CRT may induce mitochondrial damage. • Mitochondrial CRT may inhibit the phosphorylation of mitochondrial STAT3. - Abstract: Background: Calreticulin (CRT), a Ca{sup 2+}-binding chaperone of the endoplasmic reticulum, can also be found in several other locations including the cytosol, nucleus, secretory granules, the outer side of the plasma membrane, and the extracellular matrix. Whether CRT is localized at mitochondria of cardiomyocytes and whether such localization is affected under DCM are still unclear. Methods and results: The DCM model was generated in rats by the daily oral administration of furazolidone for thirty weeks. Echocardiographic and hemodynamic studies demonstrated enlarged left ventricular dimensions and reduced systolic and diastolic function in DCM rats. Immuno-electron microscopy and Western blot showed that CRT was present in cardiomyocyte mitochondria and the mitochondrial content of CRT was increased in DCM hearts (P < 0.05). Morphometric analysis showed notable myocardial apoptosis and mitochondrial swelling with fractured or dissolved cristae in the DCM hearts. Compared with the control group, the mitochondrial membrane potential level of the freshly isolated cardiac mitochondria and the enzyme activities of cytochrome c oxidase and succinate dehydrogenase in the model group were significantly decreased (P < 0.05), and the myocardial apoptosis index and the caspase activities of caspase-9 and caspase-3 were significantly increased (P < 0.05). Pearson linear correlation analysis showed that the mitochondrial content of CRT had negative correlations with the mitochondrial function, and a positive correlation with myocardial apoptosis index (P < 0.001). The protein expression level of cytochrome c and the phosphorylation activity of STAT3 in the

  3. Association of calreticulin expression with disease activity and organ damage in systemic lupus erythematosus patients.

    PubMed

    Wang, Yichao; Xie, Jiaogui; Liu, Zhili; Fu, Hongwei; Huo, Qianyu; Gu, Yajun; Liu, Yunde

    2017-05-01

    Measurement of disease activity in patients with systemic lupus erythematosus (SLE) is important for monitoring disease progression and evaluating the therapeutic effects. The severity of organ damage correlates with clinical status and prognosis. Therefore, it is imperative to find an effective biomarker measuring disease activity and organ damage for SLE management. The present study investigated the possibility of serum calreticulin (CRT) in the assessment of disease activity and organ damage in SLE patients. Serum CRT levels from 80 patients with SLE, 55 patients with other autoimmune diseases and 60 healthy controls (HC) were measured by ELISA. Disease activity was assessed using the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) scores. Organ damage was evaluated with the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index. CRT levels in SLE were significantly higher than that in other autoimmune diseases and HC. CRT was correlated with SLEDAI-2K score (r=0.3345, P=0.0024), and with anti-double-stranded DNA (anti-dsDNA) (r=0.4483, P<0.0001). A significant negative correlation of CRT levels with complement 3 (r=-0.3635, P=0.0009) and complement 4 (r=-0.3507, P=0.0014) was observed in patients with SLE. Furthermore, the patients with SLE and a positive anti-Ro52 result had higher levels of CRT compared with those with a negative anti-Ro52 result (P<0.001). Elevated levels of CRT were also reported among patients with SLE who also indicated the presence of cumulative organ damage. In addition, increased expression of CRT correlated with the presence of lupus nephritis. In conclusion, the results of the current report provided that CRT may be used as a potential biomarker for clinical diagnosis and of prognosis, providing additional information regarding disease activity and organ damage alongside other traditional indices.

  4. A new approach for investigating venom function applied to venom calreticulin in a parasitoid wasp

    PubMed Central

    Siebert, Aisha L.; Wheeler, David; Werren, John H.

    2015-01-01

    A new method is developed to investigate functions of venom components, using venom gene RNA interference knockdown in the venomous animal coupled with RNA sequencing in the envenomated host animal. The vRNAi/eRNA-Seq approach is applied to the venom calreticulin component (v-crc) of the parasitoid wasp Nasonia vitripennis. Parasitoids are common, venomous animals that inject venom proteins into host insects, where they modulate physiology and metabolism to produce a better food resource for the parasitoid larvae. vRNAi/eRNA-Seq indicates that v-crc acts to suppress expression of innate immune cell response, enhance expression of clotting genes in the host, and up-regulate cuticle genes. V-crc KD also results in an increased melanization reaction immediately following envenomation. We propose that v-crc inhibits innate immune response to parasitoid venom and reduces host bleeding during adult and larval parasitoid feeding. Experiments do not support the hypothesis that v-crc is required for the developmental arrest phenotype observed in envenomated hosts. We propose that an important role for some venom components is to reduce (modulate) the exaggerated effects of other venom components on target host gene expression, physiology, and survival, and term this venom mitigation. A model is developed that uses vRNAi/eRNA-Seq to quantify the contribution of individual venom components to total venom phenotypes, and to define different categories of mitigation by individual venoms on host gene expression. Mitigating functions likely contribute to the diversity of venom proteins in parasitoids and other venomous organisms. PMID:26359852

  5. Aberrant Calreticulin Expression in Articular Cartilage of Dio2 Deficient Mice

    PubMed Central

    Bomer, Nils; Cornelis, Frederique M. F.; Ramos, Yolande F. M.; den Hollander, Wouter; Lakenberg, Nico; van der Breggen, Ruud; Storms, Lies; Slagboom, P. Eline; Lories, Rik J. U.; Meulenbelt, Ingrid

    2016-01-01

    Objective To identify intrinsic differences in cartilage gene expression profiles between wild-type- and Dio2-/--mice, as a mechanism to investigate factors that contribute to prolonged healthy tissue homeostasis. Methods Previously generated microarray-data (Illumina MouseWG-6 v2) of knee cartilage of wild-type and Dio2 -/- -mice were re-analyzed to identify differential expressed genes independent of mechanical loading conditions by forced treadmill-running. RT-qPCR and western blot analyses of overexpression and knockdown of Calr in mouse chondro-progenitor cells (ATDC5) were applied to assess the direct effect of differential Calr expression on cartilage deposition. Results Differential expression analyses of articular cartilage of Dio2-/- (N = 9) and wild-type-mice (N = 11) while applying a cutoff threshold (P < 0.05 (FDR) and FC > |1,5|) resulted in 1 probe located in Calreticulin (Calr) that was found significantly downregulated in Dio2-/- mice (FC = -1.731; P = 0.044). Furthermore, overexpression of Calr during early chondrogenesis in ATDC5 cells leads to decreased proteoglycan deposition and corresponding lower Aggrecan expression, whereas knocking down Calr expression does not lead to histological differences of matrix composition. Conclusion We here demonstrate that the beneficial homeostatic state of articular cartilage in Dio2-/- mice is accompanied with significant lower expression of Calr. Functional analyses further showed that upregulation of Calr expression could act as an initiator of cartilage destruction. The consistent association between Calr and Dio2 expression suggests that enhanced expression of these genes facilitate detrimental effects on cartilage integrity. PMID:27163789

  6. Structures of parasite calreticulins provide insights into their flexibility and dual carbohydrate/peptide-binding properties

    PubMed Central

    Moreau, Christophe; Cioci, Gianluca; Iannello, Marina; Laffly, Emmanuelle; Chouquet, Anne; Ferreira, Arturo; Thielens, Nicole M.; Gaboriaud, Christine

    2016-01-01

    Calreticulin (CRT) is a multifaceted protein, initially discovered as an endoplasmic reticulum (ER) chaperone protein, that is essential in calcium metabolism. Various implications in cancer, early development and immunology have been discovered more recently for CRT, as well as its role as a dominant ‘eat-me’ prophagocytic signal. Intriguingly, cell-surface exposure/secretion of CRT is among the infective strategies used by parasites such as Trypanosoma cruzi, Entamoeba histolytica, Taenia solium, Leishmania donovani and Schistosoma mansoni. Because of the inherent flexibility of CRTs, their analysis by X-ray crystallography requires the design of recombinant constructs suitable for crystallization, and thus only the structures of two very similar mammalian CRT lectin domains are known. With the X-ray structures of two distant parasite CRTs, insights into species structural determinants that might be harnessed to fight against the parasites without affecting the functions of the host CRT are now provided. Moreover, although the hypothesis that CRT can exhibit both open and closed conformations has been proposed in relation to its chaperone function, only the open conformation has so far been observed in crystal structures. The first evidence is now provided of a complex conformational transition with the junction reoriented towards P-domain closure. SAXS experiments also provided additional information about the flexibility of T. cruzi CRT in solution, thus complementing crystallographic data on the open conformation. Finally, regarding the conserved lectin-domain structure and chaperone function, evidence is provided of its dual carbohydrate/protein specificity and a new scheme is proposed to interpret such unusual substrate-binding properties. These fascinating features are fully consistent with previous experimental observations, as discussed considering the broad spectrum of CRT sequence conservations and differences. PMID:27840680

  7. Calreticulin Regulates Transforming Growth Factor-β-stimulated Extracellular Matrix Production*

    PubMed Central

    Zimmerman, Kurt A.; Graham, Lauren V.; Pallero, Manuel A.; Murphy-Ullrich, Joanne E.

    2013-01-01

    Endoplasmic reticulum (ER) stress is an emerging factor in fibrotic disease, although precise mechanisms are not clear. Calreticulin (CRT) is an ER chaperone and regulator of Ca2+ signaling up-regulated by ER stress and in fibrotic tissues. Previously, we showed that ER CRT regulates type I collagen transcript, trafficking, secretion, and processing into the extracellular matrix (ECM). To determine the role of CRT in ECM regulation under fibrotic conditions, we asked whether CRT modified cellular responses to the pro-fibrotic cytokine, TGF-β. These studies show that CRT−/− mouse embryonic fibroblasts (MEFs) and rat and human idiopathic pulmonary fibrosis lung fibroblasts with siRNA CRT knockdown had impaired TGF-β stimulation of type I collagen and fibronectin. In contrast, fibroblasts with increased CRT expression had enhanced responses to TGF-β. The lack of CRT does not impact canonical TGF-β signaling as TGF-β was able to stimulate Smad reporter activity in CRT−/− MEFs. CRT regulation of TGF-β-stimulated Ca2+ signaling is important for induction of ECM. CRT−/− MEFs failed to increase intracellular Ca2+ levels in response to TGF-β. NFAT activity is required for ECM stimulation by TGF-β. In CRT−/− MEFs, TGF-β stimulation of NFAT nuclear translocation and reporter activity is impaired. Importantly, CRT is required for TGF-β stimulation of ECM under conditions of ER stress, as tunicamycin-induced ER stress was insufficient to induce ECM production in TGF-β stimulated CRT−/− MEFs. Together, these data identify CRT-regulated Ca2+-dependent pathways as a critical molecular link between ER stress and TGF-β fibrotic signaling. PMID:23564462

  8. Calreticulin mutants in mice induce an MPL-dependent thrombocytosis with frequent progression to myelofibrosis.

    PubMed

    Marty, Caroline; Pecquet, Christian; Nivarthi, Harini; El-Khoury, Mira; Chachoua, Ilyas; Tulliez, Micheline; Villeval, Jean-Luc; Raslova, Hana; Kralovics, Robert; Constantinescu, Stefan N; Plo, Isabelle; Vainchenker, William

    2016-03-10

    Frameshift mutations in the calreticulin (CALR) gene are seen in about 30% of essential thrombocythemia and myelofibrosis patients. To address the contribution of the CALR mutants to the pathogenesis of myeloproliferative neoplasms, we engrafted lethally irradiated recipient mice with bone marrow cells transduced with retroviruses expressing these mutants. In contrast to wild-type CALR, CALRdel52 (type I) and, to a lesser extent, CALRins5 (type II) induced thrombocytosis due to a megakaryocyte (MK) hyperplasia. Disease was transplantable into secondary recipients. After 6 months, CALRdel52-, in contrast to rare CALRins5-, transduced mice developed a myelofibrosis associated with a splenomegaly and a marked osteosclerosis. Monitoring of virus-transduced populations indicated that CALRdel52 leads to expansion at earlier stages of hematopoiesis than CALRins5. However, both mutants still specifically amplified the MK lineage and platelet production. Moreover, a mutant deleted of the entire exon 9 (CALRdelex9) did not induce a disease, suggesting that the oncogenic property of CALR mutants was related to the new C-terminus peptide. To understand how the CALR mutants target the MK lineage, we used a cell-line model and demonstrated that the CALR mutants, but not CALRdelex9, specifically activate the thrombopoietin (TPO) receptor (MPL) to induce constitutive activation of Janus kinase 2 and signal transducer and activator of transcription 5/3/1. We confirmed in c-mpl- and tpo-deficient mice that expression of Mpl, but not of Tpo, was essential for the CALR mutants to induce thrombocytosis in vivo, although Tpo contributes to disease penetrance. Thus, CALR mutants are sufficient to induce thrombocytosis through MPL activation.

  9. Hard tick calreticulin (CRT) gene coding regions have only one intron with conserved positions and variable sizes.

    PubMed

    Xu, Guang; Fang, Quentin Q; Sun, Yi; Keirans, James E; Durden, Lance A

    2005-12-01

    Calreticulin (CRT) is a unique eukaryotic gene. The CRT gene product, calreticulin, was first identified as a calcium binding protein in 1974, but further investigations have indicated that CRT protein performs many functions in cells, including involvement in evading the host's immune system by parasites. Many studies of CRT have been published since the molecule was first discovered; however, the CRT gene exon-intron structure is only known for a limited number of ectoparasite species. In this study, we compared tick CRT genomic sequences to the corresponding cDNA from 28 species and found that 2 exons and 1 intron are present in the tick CRT gene. The intron position is conserved in 28 hard ticks, but intron size and nucleotide sequences vary. Three tick introns possess duplicated fragments and are twice as long as other introns. All tick CRT introns obey the GT-AG rule in the splice-site junctions and are phase 1 introns. By comparing tick CRT introns to those of fruit fly, mouse, and human, we conclude that tick CRT introns belong to the intron-late type. The number and size of CRT introns have increased through the evolution of eukaryotes.

  10. Collaboration between a soluble C-type lectin and calreticulin facilitates white spot syndrome virus infection in shrimp.

    PubMed

    Wang, Xian-Wei; Xu, Yi-Hui; Xu, Ji-Dong; Zhao, Xiao-Fan; Wang, Jin-Xing

    2014-09-01

    White spot syndrome virus (WSSV) mainly infects crustaceans through the digestive tract. Whether C-type lectins (CLs), which are important receptors for many viruses, participate in WSSV infection in the shrimp stomach remains unknown. In this study, we orally infected kuruma shrimp Marsupenaeus japonicus to model the natural transmission of WSSV and identified a CL (designated as M. japonicus stomach virus-associated CL [MjsvCL]) that was significantly induced by virus infection in the stomach. Knockdown of MjsvCL expression by RNA interference suppressed the virus replication, whereas exogenous MjsvCL enhanced it. Further analysis by GST pull-down and coimmunoprecipitation showed that MjsvCL could bind to viral protein 28, the most abundant and functionally relevant envelope protein of WSSV. Furthermore, cell-surface calreticulin was identified as a receptor of MjsvCL, and the interaction between these proteins was a determinant for the viral infection-promoting activity of MjsvCL. The MjsvCL-calreticulin pathway facilitated virus entry likely in a cholesterol-dependent manner. This study provides insights into a mechanism by which soluble CLs capture and present virions to the cell-surface receptor to facilitate viral infection.

  11. Ectopic expression of a maize calreticulin mitigates calcium deficiency-like disorders in "sCAX1"-expressing tobacco and tomato

    USDA-ARS?s Scientific Manuscript database

    Deregulated expression of an Arabidopsis H(+)/Ca(2+) antiporter (sCAX1) in agricultural crops increases total calcium (Ca(2+)) but may result in yield losses due to Ca(2+) deficiency-like symptoms. Here we demonstrate that co-expression of a maize calreticulin (CRT, a Ca(2+) binding protein located ...

  12. Selective testing for calreticulin gene mutations in patients with splanchnic vein thrombosis: A prospective cohort study.

    PubMed

    Poisson, Johanne; Plessier, Aurélie; Kiladjian, Jean-Jacques; Turon, Fanny; Cassinat, Bruno; Andreoli, Annalisa; De Raucourt, Emmanuelle; Goria, Odile; Zekrini, Kamal; Bureau, Christophe; Lorre, Florence; Cervantes, Francisco; Colomer, Dolors; Durand, François; Garcia-Pagan, Juan-Carlos; Casadevall, Nicole; Valla, Dominique-Charles; Rautou, Pierre-Emmanuel; Marzac, Christophe

    2017-09-01

    Myeloproliferative neoplasms (MPN) are the leading cause of splanchnic vein thrombosis (SVT). Janus kinase 2 gene (JAK2)(V617F) mutations are found in 80 to 90% of patients with SVT and MPN. Mutations of the calreticulin (CALR) gene have also been reported. However, as their prevalence ranges from 0 to 2%, the utility of routine testing is questionable. This study aimed to identify a group of patients with SVT at high risk of harboring CALR mutations and thus requiring this genetic testing. CALR, JAK2(V617F) and thrombopoietin receptor gene (MPL) mutations were analysed in a test cohort that included 312 patients with SVT. Criteria to identify patients at high risk of CALR mutations in this test cohort was used and evaluated in a validation cohort that included 209 patients with SVT. In the test cohort, 59 patients had JAK2(V617F), five had CALR and none had MPL mutations. Patients with CALR mutations had higher spleen height and platelet count than patients without these mutations. All patients with CALR mutations had a spleen height ⩾16cm and platelet count >200×10(9)/L. These criteria had a positive predictive value of 56% (5/9) and a negative predictive value of 100% (0/233) for the identification of CALR mutations. In the validation cohort, these criteria had a positive predictive value of 33% (2/6) and a negative predictive value of 99% (1/96). CALR mutations should be tested in patients with SVT, a spleen height ⩾16cm, platelet count >200×10(9)/L, and no JAK2(V617F). This strategy avoids 96% of unnecessary CALR mutations testing. Lay summary: Mutations of the CALR gene are detected in 0 to 2% of patients with SVT, thus the utility of systematic CALR mutation testing to diagnose MPN is questionable. This study demonstrates that CALR mutations testing can be restricted to patients with SVT, a spleen height ⩾16cm, a platelet count >200×10(9)/L, and no JAK2(V617F). This strategy avoids 96% of unnecessary CALR mutations testing. Copyright © 2017

  13. Does native Trypanosoma cruzi calreticulin mediate growth inhibition of a mammary tumor during infection?

    PubMed

    Abello-Cáceres, Paula; Pizarro-Bauerle, Javier; Rosas, Carlos; Maldonado, Ismael; Aguilar-Guzmán, Lorena; González, Carlos; Ramírez, Galia; Ferreira, Jorge; Ferreira, Arturo

    2016-09-13

    For several decades now an antagonism between Trypanosoma cruzi infection and tumor development has been detected. The molecular basis of this phenomenon remained basically unknown until our proposal that T. cruzi Calreticulin (TcCRT), an endoplasmic reticulum-resident chaperone, translocated-externalized by the parasite, may mediate at least an important part of this effect. Thus, recombinant TcCRT (rTcCRT) has important in vivo antiangiogenic and antitumor activities. However, the relevant question whether the in vivo antitumor effect of T. cruzi infection is indeed mediated by the native chaperone (nTcCRT), remains open. Herein, by using specific modified anti-rTcCRT antibodies (Abs), we have neutralized the antitumor activity of T. cruzi infection and extracts thereof, thus identifying nTcCRT as a valid mediator of this effect. Polyclonal anti-rTcCRT F(ab')2 Ab fragments were used to reverse the capacity of rTcCRT to inhibit EAhy926 endothelial cell (EC) proliferation, as detected by BrdU uptake. Using these F(ab')2 fragments, we also challenged the capacity of nTcCRT, during T. cruzi infection, to inhibit the growth of an aggressive mammary adenocarcinoma cell line (TA3-MTXR) in mice. Moreover, we determined the capacity of anti-rTcCRT Abs to reverse the antitumor effect of an epimastigote extract (EE). Finally, the effects of these treatments on tumor histology were evaluated. The rTcCRT capacity to inhibit ECs proliferation was reversed by anti-rTcCRT F(ab')2 Ab fragments, thus defining them as valid probes to interfere in vivo with this important TcCRT function. Consequently, during infection, these Ab fragments also reversed the in vivo experimental mammary tumor growth. Moreover, anti-rTcCRT Abs also neutralized the antitumor effect of an EE, again identifying the chaperone protein as an important mediator of this anti mammary tumor effect. Finally, as determined by conventional histological parameters, in infected animals and in those treated with EE

  14. Exon-intron structure and sequence variation of the calreticulin gene among Rhipicephalus sanguineus group ticks.

    PubMed

    Porretta, Daniele; Latrofa, Maria Stefania; Dantas-Torres, Filipe; Mastrantonio, Valentina; Iatta, Roberta; Otranto, Domenico; Urbanelli, Sandra

    2016-12-12

    Calreticulin proteins (CRTs) are important components of tick saliva, which is involved in the blood meal success, pathogen transmission and host allergic responses. The characterization of the genes encoding for salivary proteins, such as CRTs, is pivotal to understand the mechanisms of tick-host interaction during blood meal and to develop tick control strategies based on their inhibition. In hard ticks, crt genes were shown to have only one intron with conserved position among species. In this study we investigated the exon-intron structure and variation of the crt gene in Rhipicephalus spp. ticks in order to assess the crt exon-intron structure and the potential utility of crt gene as a molecular marker. We sequenced the exon-intron region of crt gene in ticks belonging to so-called tropical and temperate lineages of Rhipicephalus sanguineus (sensu lato), Rhipicephalus sp. I, Rhipicephalus sp. III, Rhipicephalus sp. IV, R. guilhoni, R. muhsamae and R. turanicus. Genetic divergence and phylogenetic relationships between the sequences obtained were estimated. All individuals belonging to the tropical lineage of R. sanguineus (s.l.), R. guilhoni, R. muhsamae, R. turanicus, Rhipicephalus sp. III and Rhipicephalus sp. IV analysed showed crt intron-present alleles. However, both crt intron-present and intron-absent alleles were found in Rhipicephalus sp. I and the temperate lineage of R. sanguineus (s.l.), showing the occurrence of an intraspecific intron presence-absence polymorphism. Phylogenetic relationships among the crt intron-present sequences showed distinct lineages for all taxa, with the tropical and temperate lineages of R. sanguineus (s.l.) being more closely related to each other. We expanded previous studies about the characterization of crt gene in hard ticks. Our results highlighted a previously overlooked variation in the crt structure among Rhipicephalus spp., and among hard ticks in general. Notably, the intron presence/absence polymorphism

  15. Human Survivin and Trypanosoma cruzi Calreticulin Act in Synergy against a Murine Melanoma In Vivo

    PubMed Central

    Aguilar-Guzmán, Lorena; Lobos-González, Lorena; Rosas, Carlos; Vallejos, Gerardo; Falcón, Cristián; Sosoniuk, Eduardo; Coddou, Francisca; Leyton, Lisette; Lemus, David; Quest, Andrew F. G.; Ferreira, Arturo

    2014-01-01

    Immune-based anti-tumor or anti-angiogenic therapies hold considerable promise for the treatment of cancer. The first approach seeks to activate tumor antigen-specific T lymphocytes while, the second, delays tumor growth by interfering with blood supply. Tumor Associated Antigens are often employed to target tumors with therapeutic drugs, but some are also essential for tumor viability. Survivin (Surv) is a member of the inhibitor of apoptosis protein family that is considered a Tumor Associated Antigen important for cancer cell viability and proliferation. On the other hand, Trypanosoma cruzi (the agent of Chagas’ disease) calreticulin (TcCRT) displays remarkable anti-angiogenic properties. Because these molecules are associated with different tumor targets, we reasoned that immunization with a Surv-encoding plasmid (pSurv) and concomitant TcCRT administration should generate a stronger anti-tumor response than application of either treatment separately. To evaluate this possibility, C57BL/6 mice were immunized with pSurv and challenged with an isogenic melanoma cell line that had been pre-incubated with recombinant TcCRT (rTcCRT). Following tumor cell inoculation, mice were injected with additional doses of rTcCRT. For the combined regimen we observed in mice that: i). Tumor growth was impaired, ii). Humoral anti-rTcCRT immunity was induced and, iii). In vitro rTcCRT bound to melanocytes, thereby promoting the incorporation of human C1q and subsequent macrophage phagocytosis of tumor cells. These observations are interpreted to reflect the consequence of the following sequence of events: rTcCRT anti-angiogenic activity leads to stress in tumor cells. Murine CRT is then translocated to the external membrane where, together with rTcCRT, complement C1 is captured, thus promoting tumor phagocytosis. Presentation of the Tumor Associated Antigen Surv induces the adaptive anti-tumor immunity and, independently, mediates anti-endothelial cell immunity leading to an

  16. Programmed cell removal biomarkers calreticulin and CD47 implicated in oral lichen planus.

    PubMed

    Allon, I; Vered, H; Hirshberg, A

    2015-10-01

    To investigate the expression of the programmed cell removal markers, calreticulin (CRT) and CD47, known to be involved in various autoimmune diseases, in patients with oral lichen planus (OLP), and to investigate the association with clinical behavior. Biopsies of 78 patients with OLP were included. The clinical data were collected from patients' charts. The expression of CRT and CD47 was immunomorphometrically analyzed in the epithelial (CRTep, CD47ep) and inflammatory cells (CRTinf, CD47inf), and the results were correlated with the clinical presentation. The epithelial and inflammatory cells expressed CRT (2.83 ± 6.62 and 5.13 ± 3.72) and CD47 (7.92 ± 4.6 and 10.7 ± 7.16). The expressions of CD47ep and CD47inf were associated (R = 0.64, P < 0.0005) with one another. The expressions of CRTinf and CD47ep were higher in atrophic erosive forms (A/ELP) than in the keratotic form of patients with OLP (6.46 ± 0.76 and 9.38 ± 0.87 vs 4.2 ± 0.61 and 6.84 ± 0.91, respectively, P = 0.002 and P = 0.021). The expression of CRTep was associated with more localized lesions (P < 0.009) and more abundant in males (P = 0.049), and the expression of CRTinf was associated with the presence of skin lesions and symptoms (P < 0.034 and P = 0.047, respectively). Only in A/ELP patients, the expression of CRTep was associated with high expression of CD47ep (R = 0.6, P = 0.004), where both CD47ep and CD47inf were associated with lower age of the patients (R = -0.48, P = 0.03 and R = -0.54, P = 0.01). The pattern of expression of CRT and CD47 in OLP suggests a general programmed cell removal response in OLP. Symptomatic patients may benefit from CRT/CD47 targeted therapy in the future. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  17. Human survivin and Trypanosoma cruzi calreticulin act in synergy against a murine melanoma in vivo.

    PubMed

    Aguilar-Guzmán, Lorena; Lobos-González, Lorena; Rosas, Carlos; Vallejos, Gerardo; Falcón, Cristián; Sosoniuk, Eduardo; Coddou, Francisca; Leyton, Lisette; Lemus, David; Quest, Andrew F G; Ferreira, Arturo

    2014-01-01

    Immune-based anti-tumor or anti-angiogenic therapies hold considerable promise for the treatment of cancer. The first approach seeks to activate tumor antigen-specific T lymphocytes while, the second, delays tumor growth by interfering with blood supply. Tumor Associated Antigens are often employed to target tumors with therapeutic drugs, but some are also essential for tumor viability. Survivin (Surv) is a member of the inhibitor of apoptosis protein family that is considered a Tumor Associated Antigen important for cancer cell viability and proliferation. On the other hand, Trypanosoma cruzi (the agent of Chagas' disease) calreticulin (TcCRT) displays remarkable anti-angiogenic properties. Because these molecules are associated with different tumor targets, we reasoned that immunization with a Surv-encoding plasmid (pSurv) and concomitant TcCRT administration should generate a stronger anti-tumor response than application of either treatment separately. To evaluate this possibility, C57BL/6 mice were immunized with pSurv and challenged with an isogenic melanoma cell line that had been pre-incubated with recombinant TcCRT (rTcCRT). Following tumor cell inoculation, mice were injected with additional doses of rTcCRT. For the combined regimen we observed in mice that: i). Tumor growth was impaired, ii). Humoral anti-rTcCRT immunity was induced and, iii). In vitro rTcCRT bound to melanocytes, thereby promoting the incorporation of human C1q and subsequent macrophage phagocytosis of tumor cells. These observations are interpreted to reflect the consequence of the following sequence of events: rTcCRT anti-angiogenic activity leads to stress in tumor cells. Murine CRT is then translocated to the external membrane where, together with rTcCRT, complement C1 is captured, thus promoting tumor phagocytosis. Presentation of the Tumor Associated Antigen Surv induces the adaptive anti-tumor immunity and, independently, mediates anti-endothelial cell immunity leading to an

  18. Calreticulin and other components of endoplasmic reticulum stress in rat and human inflammatory demyelination

    PubMed Central

    2013-01-01

    Background Calreticulin (CRT) is a chaperone protein, which aids correct folding of glycosylated proteins in the endoplasmic reticulum (ER). Under conditions of ER stress, CRT is upregulated and may be displayed on the surface of cells or be secreted. This ‘ecto-CRT’ may activate the innate immune response or it may aid clearance of apoptotic cells. Our and other studies have demonstrated upregulation of ER stress markers CHOP, BiP, ATF4, XBP1 and phosphorylated e-IF2 alpha (p-eIF2 alpha) in biopsy and post-mortem human multiple sclerosis (MS) samples. We extend this work by analysing changes in expression of CRT, BiP, CHOP, XBP1 and p-eIF2 alpha in a rat model of inflammatory demyelination. Demyelination was induced in the spinal cord by intradermal injection of recombinant mouse MOG mixed with incomplete Freund’s adjuvant (IFA) at the base of the tail. Tissue samples were analysed by semi-quantitative scoring of immunohistochemically stained frozen tissue sections. Data generated following sampling of tissue from animals with spinal cord lesions, was compared to that obtained using tissue derived from IFA- or saline-injected controls. CRT present in rat serum and in a cohort of human serum derived from 14 multiple sclerosis patients and 11 healthy controls was measured by ELISA. Results Stained tissue scores revealed significantly (p<0.05) increased amounts of CRT, CHOP and p-eIF2 alpha in the lesion, lesion edge and normal-appearing white matter when compared to controls. CHOP and p-eIF2 alpha were also significantly raised in regions of grey matter and the central canal (p<0.05). Immunofluorescent dual-label staining confirmed expression of these markers in astrocytes, microglia or neurons. Dual staining of rat and human spinal cord lesions with Oil Red O and CRT antibody showed co-localisation of CRT with the rim of myelin fragments. ELISA testing of sera from control and EAE rats demonstrated significant down-regulation (p<0.05) of CRT in the serum of

  19. The miR-27a-calreticulin axis affects drug-induced immunogenic cell death in human colorectal cancer cells

    PubMed Central

    Colangelo, T; Polcaro, G; Ziccardi, P; Muccillo, L; Galgani, M; Pucci, B; Rita Milone, M; Budillon, A; Santopaolo, M; Mazzoccoli, G; Matarese, G; Sabatino, L; Colantuoni, V

    2016-01-01

    Immunogenic cell death (ICD) evoked by chemotherapeutic agents implies emission of selected damage-associated molecular patterns (DAMP) such as cell surface exposure of calreticulin, secretion of ATP and HMGB1. We sought to verify whether miR-27a is implicated in ICD, having demonstrated that it directly targets calreticulin. To this goal, we exposed colorectal cancer cell lines, genetically modified to express high or low miR-27a levels, to two bona fide ICD inducers (mitoxantrone and oxaliplatin). Low miR-27a-expressing cells displayed more ecto-calreticulin on the cell surface and increased ATP and HMGB1 secretion than high miR-27a-expressing ones in time-course experiments upon drug exposure. A calreticulin target protector counteracted the miR-27a effects while specific siRNAs mimicked them, confirming the results reported. In addition, miR-27a negatively influenced the PERK-mediated route and the late PI3K-dependent secretory step of the unfolded protein response to endoplasmic reticulum stress, suggesting that miR-27a modulates the entire ICD program. Interestingly, upon chemotherapeutic exposure, low miR-27a levels associated with an earlier and stronger induction of apoptosis and with morphological and molecular features of autophagy. Remarkably, in ex vivo setting, under the same chemotherapeutic induction, the conditioned media from high miR-27a-expressing cells impeded dendritic cell maturation while increased the secretion of specific cytokines (interleukin (IL)-4, IL-6, IL-8) and negatively influenced CD4+ T-cell interferon γ production and proliferation, all markers of a tumor immunoevasion strategy. In conclusion, we provide the first evidence that miR-27a impairs the cell response to drug-induced ICD through the regulatory axis with calreticulin. PMID:26913599

  20. Catalyzing RE Project Development

    SciTech Connect

    Anderson, Kate; Elgqvist, Emma; Walker, Andy; Cutler, Dylan; Olis, Dan; DiOrio, Nick; Simpkins, Travis

    2016-09-01

    This poster details how screenings done with REopt - NREL's software modeling platform for energy systems integration and optimization - are helping to catalyze the development of hundreds of megawatts of renewable energy.

  1. Muon Catalyzed Fusion

    NASA Technical Reports Server (NTRS)

    Armour, Edward A.G.

    2007-01-01

    Muon catalyzed fusion is a process in which a negatively charged muon combines with two nuclei of isotopes of hydrogen, e.g, a proton and a deuteron or a deuteron and a triton, to form a muonic molecular ion in which the binding is so tight that nuclear fusion occurs. The muon is normally released after fusion has taken place and so can catalyze further fusions. As the muon has a mean lifetime of 2.2 microseconds, this is the maximum period over which a muon can participate in this process. This article gives an outline of the history of muon catalyzed fusion from 1947, when it was first realised that such a process might occur, to the present day. It includes a description of the contribution that Drachrnan has made to the theory of muon catalyzed fusion and the influence this has had on the author's research.

  2. Proteomic screening identifies calreticulin as a miR-27a direct target repressing MHC class I cell surface exposure in colorectal cancer

    PubMed Central

    Colangelo, T; Polcaro, G; Ziccardi, P; Pucci, B; Muccillo, L; Galgani, M; Fucci, A; Milone, M R; Budillon, A; Santopaolo, M; Votino, C; Pancione, M; Piepoli, A; Mazzoccoli, G; Binaschi, M; Bigioni, M; Maggi, C A; Fassan, M; Laudanna, C; Matarese, G; Sabatino, L; Colantuoni, V

    2016-01-01

    Impairment of the immune response and aberrant expression of microRNAs are emerging hallmarks of tumour initiation/progression, in addition to driver gene mutations and epigenetic modifications. We performed a preliminary survey of independent adenoma and colorectal cancer (CRC) miRnoma data sets and, among the most dysregulated miRNAs, we selected miR-27a and disclosed that it is already upregulated in adenoma and further increases during the evolution to adenocarcinoma. To identify novel genes and pathways regulated by this miRNA, we employed a differential 2DE-DIGE proteome analysis. We showed that miR-27a modulates a group of proteins involved in MHC class I cell surface exposure and, mechanistically, demonstrated that calreticulin is a miR-27a direct target responsible for most downstream effects in epistasis experiments. In vitro miR-27a affected cell proliferation and angiogenesis; mouse xenografts of human CRC cell lines expressing different miR-27a levels confirmed the protein variations and recapitulated the cell growth and apoptosis effects. In vivo miR-27a inversely correlated with MHC class I molecules and calreticulin expression, CD8+ T cells infiltration and cytotoxic activity (LAMP-1 exposure and perforin release). Tumours with high miR-27a, low calreticulin and CD8+ T cells' infiltration were associated with distant metastasis and poor prognosis. Our data demonstrate that miR-27a acts as an oncomiRNA, represses MHC class I expression through calreticulin downregulation and affects tumour progression. These results may pave the way for better diagnosis, patient stratification and novel therapeutic approaches. PMID:26913609

  3. Catalyzed sodium chlorate candles

    NASA Technical Reports Server (NTRS)

    Malich, C. W.; Wydeven, T.

    1972-01-01

    The catalytic effect of cobalt powder on chlorate decomposition has been confirmed. Catalysis is enhanced by oxidation of the metal during burning. Catalysts other than cobalt compounds should also be effective; the complete elimination of fuel has shown that the oxidation of cobalt during decomposition is not a vital factor in the improved performance of catalyzed candles.

  4. The Interaction of Classical Complement Component C1 with Parasite and Host Calreticulin Mediates Trypanosoma cruzi Infection of Human Placenta

    PubMed Central

    Castillo, Christian; Ramírez, Galia; Valck, Carolina; Aguilar, Lorena; Maldonado, Ismael; Rosas, Carlos; Galanti, Norbel; Kemmerling, Ulrike; Ferreira, Arturo

    2013-01-01

    Background 9 million people are infected with Trypanosoma cruzi in Latin America, plus more than 300,000 in the United States, Canada, Europe, Australia, and Japan. Approximately 30% of infected individuals develop circulatory or digestive pathology. While in underdeveloped countries transmission is mainly through hematophagous arthropods, transplacental infection prevails in developed ones. Methodology/Principal Findings During infection, T. cruzi calreticulin (TcCRT) translocates from the endoplasmic reticulum to the area of flagellum emergence. There, TcCRT acts as virulence factor since it binds maternal classical complement component C1q that recognizes human calreticulin (HuCRT) in placenta, with increased parasite infectivity. As measured ex vivo by quantitative PCR in human placenta chorionic villi explants (HPCVE) (the closest available correlate of human congenital T. cruzi infection), C1q mediated up to a 3–5-fold increase in parasite load. Because anti-TcCRT and anti-HuCRT F(ab′)2 antibody fragments are devoid of their Fc-dependent capacity to recruit C1q, they reverted the C1q-mediated increase in parasite load by respectively preventing its interaction with cell-bound CRTs from both parasite and HPCVE origins. The use of competing fluid-phase recombinant HuCRT and F(ab′)2 antibody fragments anti-TcCRT corroborated this. These results are consistent with a high expression of fetal CRT on placental free chorionic villi. Increased C1q-mediated infection is paralleled by placental tissue damage, as evidenced by histopathology, a damage that is ameliorated by anti-TcCRT F(ab′)2 antibody fragments or fluid-phase HuCRT. Conclusions/Significance T. cruzi infection of HPCVE is importantly mediated by human and parasite CRTs and C1q. Most likely, C1q bridges CRT on the parasite surface with its receptor orthologue on human placental cells, thus facilitating the first encounter between the parasite and the fetal derived placental tissue. The results

  5. Calreticulin down-regulation inhibits the cell growth, invasion and cell cycle progression of human hepatocellular carcinoma cells.

    PubMed

    Feng, Ruo; Ye, Jianwen; Zhou, Chuang; Qi, Lei; Fu, Zhe; Yan, Bing; Liang, Zhiwei; Li, Renfeng; Zhai, Wenlong

    2015-08-27

    Hepatocellular carcinoma (HCC) is one of the most frequent cancers in the world. Calreticulin(CRT) is aberrantly overexpressed in many human cancer cells. The function of CRT in HCC cells remains unclear. We attempted to investigate the effects and the underlying mechanisms of CRT down-regulation on HCC cell growth, apoptosis, cell cycle progression and invasion. To investigate the function of CRT in HCC cells, small interfering RNA (siRNA) was used to knock down the expression of CRT in SMMC7721 and HepG2 HCC cells. CRT expression was examined by Western blot and immunofluorescence. Cell proliferation was detected by CCK-8 assay. Cell cycle and apoptosis were measured by the flow cytometry. The invasion capability was assessed by transwell assay. The phosphorylation level of Akt was evaluated by Western blot. Compared with human hepatic cells L02, CRT was apparently up-regulated in SMMC7721, HepG2 and Huh7 HCC cells. Down-regulation of CRT expression effectively inhibited HCC cell growth and invasion. CRT knockdown induced cell cycle arrest and the apoptosis in SMMC7721 and HepG2 cells. Furthermore, down-regulation of CRT expression significantly decreased the Akt phosphorylation. CRT was aberrantly over-expressed in HCC cell lines. CRT over-expression contributes greatly to HCC malignant behavior, likely via PI3K/Akt pathway. CRT could serve as a potential biomarker and therapeutic target for hepatocellular carcinoma.

  6. Calreticulin exposure by malignant blasts correlates with robust anticancer immunity and improved clinical outcome in AML patients

    PubMed Central

    Fucikova, Jitka; Truxova, Iva; Hensler, Michal; Becht, Etienne; Kasikova, Lenka; Moserova, Irena; Vosahlikova, Sarka; Klouckova, Jana; Church, Sarah E.; Cremer, Isabelle; Kepp, Oliver; Kroemer, Guido; Galluzzi, Lorenzo; Salek, Cyril

    2016-01-01

    Cancer cell death can be perceived as immunogenic by the host only when malignant cells emit immunostimulatory signals (so-called “damage-associated molecular patterns,” DAMPs), as they die in the context of failing adaptive responses to stress. Accumulating preclinical and clinical evidence indicates that the capacity of immunogenic cell death to (re-)activate an anticancer immune response is key to the success of various chemo- and radiotherapeutic regimens. Malignant blasts from patients with acute myeloid leukemia (AML) exposed multiple DAMPs, including calreticulin (CRT), heat-shock protein 70 (HSP70), and HSP90 on their plasma membrane irrespective of treatment. In these patients, high levels of surface-exposed CRT correlated with an increased proportion of natural killer cells and effector memory CD4+ and CD8+ T cells in the periphery. Moreover, CRT exposure on the plasma membrane of malignant blasts positively correlated with the frequency of circulating T cells specific for leukemia-associated antigens, indicating that ecto-CRT favors the initiation of anticancer immunity in patients with AML. Finally, although the levels of ecto-HSP70, ecto-HSP90, and ecto-CRT were all associated with improved relapse-free survival, only CRT exposure significantly correlated with superior overall survival. Thus, CRT exposure represents a novel powerful prognostic biomarker for patients with AML, reflecting the activation of a clinically relevant AML-specific immune response. PMID:27802968

  7. Genotoxicity induced by Taenia solium and its reduction by immunization with calreticulin in a hamster model of taeniosis.

    PubMed

    Salazar, Ana María; Mendlovic, Fela; Cruz-Rivera, Mayra; Chávez-Talavera, Oscar; Sordo, Monserrat; Avila, Guillermina; Flisser, Ana; Ostrosky-Wegman, Patricia

    2013-06-01

    Genotoxicity induced by neurocysticercosis has been demonstrated in vitro and in vivo in humans. The adult stage of Taenia solium lodges in the small intestine and is the main risk factor to acquire neurocysticercosis, nevertheless its carcinogenic potential has not been evaluated. In this study, we determined the genotoxic effect of T. solium infection in the hamster model of taeniosis. In addition, we assessed the effect of oral immunization with recombinant T. solium calreticulin (rTsCRT) plus cholera toxin as adjuvant on micronuclei induction, as this protein has been shown to induce 33-44% protection in the hamster model of taeniosis. Blood samples were collected from the orbital venous plexus of noninfected and infected hamsters at different days postinfection, as well as from orally immunized animals, to evaluate the frequency of micronucleated reticulocytes as a measure of genotoxicity induced by parasite exposure and rTsCRT vaccination. Our results indicate that infection with T. solium caused time-dependent DNA damage in vivo and that rTsCRT immunization reduced the genotoxic damage induced by the presence of the tapeworms.

  8. Tumor-specific immunity and antiangiogenesis generated by a DNA vaccine encoding calreticulin linked to a tumor antigen.

    PubMed

    Cheng, W F; Hung, C F; Chai, C Y; Hsu, K F; He, L; Ling, M; Wu, T C

    2001-09-01

    Antigen-specific cancer immunotherapy and antiangiogenesis have emerged as two attractive strategies for cancer treatment. An innovative approach that combines both mechanisms will likely generate the most potent antitumor effect. We tested this approach using calreticulin (CRT), which has demonstrated the ability to enhance MHC class I presentation and exhibit an antiangiogenic effect. We explored the linkage of CRT to a model tumor antigen, human papilloma virus type-16 (HPV-16) E7, for the development of a DNA vaccine. We found that C57BL/6 mice vaccinated intradermally with CRT/E7 DNA exhibited a dramatic increase in E7-specific CD8(+) T cell precursors and an impressive antitumor effect against E7-expressing tumors compared with mice vaccinated with wild-type E7 DNA or CRT DNA. Vaccination of CD4/CD8 double-depleted C57BL/6 mice and immunocompromised (BALB/c nu/nu) mice with CRT/E7 DNA or CRT DNA generated significant reduction of lung tumor nodules compared with wild-type E7 DNA, suggesting that antiangiogenesis may have contributed to the antitumor effect. Examination of microvessel density in lung tumor nodules and an in vivo angiogenesis assay further confirmed the antiangiogenic effect generated by CRT/E7 and CRT. Thus, cancer therapy using CRT linked to a tumor antigen holds promise for treating tumors by combining antigen-specific immunotherapy and antiangiogenesis.

  9. Involvement of calreticulin in cell proliferation, invasion and differentiation in diallyl disulfide-treated HL-60 cells.

    PubMed

    Yi, Lan; Shan, Jian; Chen, Xin; Li, Guoqing; Li, Linwei; Tan, Hui; Su, Qi

    2016-09-01

    Diallyl disulfide (DADS) has shown potential as a therapeutic agent in various cancers. Previously, calreticulin (CRT) was found to be downregulated in differentiated HL-60 cells treated with DADS. The present study investigated the role of CRT proteins in DADS-induced proliferation, invasion and differentiation in HL-60 cells. The present study demonstrated that DADS treatment significantly changed the morphology of HL-60 cells and caused the significant time-dependent downregulation of CRT. Small interfering RNA (siRNA)-mediated knockdown of CRT expression significantly inhibited proliferation, decreased invasion ability, increased the expression of cluster of differentiation (CD)11b and reduced the expression of CD33 in DADS-treated HL-60 cells. DADS also significantly affected cell proliferation, invasion and differentiation in CRT-overexpressed HL-60 cells. Nitroblue tetrazolium (NBT) reduction assays showed decreased NBT reduction activity in the CRT overexpression group and increased NBT reduction in the CRT siRNA group. Following treatment with DADS, the NBT reduction abilities in all groups were increased. In conclusion, the present study clearly demonstrates the downregulation of CRT during DADS-induced differentiation in HL-60 cells and indicates that CRT is involved in cell proliferation, invasion and differentiation in DADS-treated HL-60 cells.

  10. Glucocorticoids Prevent Enterovirus 71 Capsid Protein VP1 Induced Calreticulin Surface Exposure by Alleviating Neuronal ER Stress.

    PubMed

    Hu, Dan-Dan; Mai, Jian-Ning; He, Li-Ya; Li, Pei-Qing; Chen, Wen-Xiong; Yan, Jian-Jiang; Zhu, Wei-Dong; Deng, Li; Wei, Dan; Liu, Di-Hui; Yang, Si-Da; Yao, Zhi-Bin

    2017-02-01

    Severe hand-foot-and-mouth disease (HFMD) caused by Enterovirus 71 (EV71) always accompanies with inflammation and neuronal damage in the central nervous system (CNS). During neuronal injuries, cell surface-exposed calreticulin (Ecto-CRT) is an important mediator for primary phagocytosis of viable neurons by microglia. Our data confirmed that brainstem neurons underwent neuronophagia by glia in EV71-induced death cases of HFMD. EV71 capsid proteins VP1, VP2, VP3, or VP4 did not induce apoptosis of brainstem neurons. Interestingly, we found VP1-activated endoplasmic reticulum (ER) stress and autophagy could promote Ecto-CRT upregulation, but ER stress or autophagy alone was not sufficient to induce CRT exposure. Furthermore, we demonstrated that VP1-induced autophagy activation was mediated by ER stress. Meaningfully, we found dexamethasone treatment could attenuate Ecto-CRT upregulation by alleviating VP1-induced ER stress. Altogether, these findings identify VP1-promoted Ecto-CRT upregulation as a novel mechanism of EV71-induced neuronal cell damage and highlight the potential of the use of glucocorticoids to treat severe HFMD patients with CNS complications.

  11. Involvement of calreticulin in cell proliferation, invasion and differentiation in diallyl disulfide-treated HL-60 cells

    PubMed Central

    Yi, Lan; Shan, Jian; Chen, Xin; Li, Guoqing; Li, Linwei; Tan, Hui; Su, Qi

    2016-01-01

    Diallyl disulfide (DADS) has shown potential as a therapeutic agent in various cancers. Previously, calreticulin (CRT) was found to be downregulated in differentiated HL-60 cells treated with DADS. The present study investigated the role of CRT proteins in DADS-induced proliferation, invasion and differentiation in HL-60 cells. The present study demonstrated that DADS treatment significantly changed the morphology of HL-60 cells and caused the significant time-dependent downregulation of CRT. Small interfering RNA (siRNA)-mediated knockdown of CRT expression significantly inhibited proliferation, decreased invasion ability, increased the expression of cluster of differentiation (CD)11b and reduced the expression of CD33 in DADS-treated HL-60 cells. DADS also significantly affected cell proliferation, invasion and differentiation in CRT-overexpressed HL-60 cells. Nitroblue tetrazolium (NBT) reduction assays showed decreased NBT reduction activity in the CRT overexpression group and increased NBT reduction in the CRT siRNA group. Following treatment with DADS, the NBT reduction abilities in all groups were increased. In conclusion, the present study clearly demonstrates the downregulation of CRT during DADS-induced differentiation in HL-60 cells and indicates that CRT is involved in cell proliferation, invasion and differentiation in DADS-treated HL-60 cells. PMID:27588133

  12. Abundant accumulation of the calcium-binding molecular chaperone calreticulin in specific floral tissues of Arabidopsis thaliana.

    PubMed

    Nelson, D E; Glaunsinger, B; Bohnert, H J

    1997-05-01

    Calreticulin (CRT) is a calcium-binding protein in the endoplasmic reticulum (ER) with an established role as a molecular chaper-one. An additional function in signal transduction, specifically in calcium distribution, is suggested but not proven. We have analyzed the expression pattern of Arabidopsis thaliana CRTs for a comparison with these proposed roles. Three CRT genes were expressed, with identities of the encoded proteins ranging from 54 to 86%. Protein motifs with established functions found in CRTs of other species were conserved. CRT was found in all of the cells in low amounts, whereas three distinct floral tissues showed abundant expression: secreting nectaries, ovules early in development, and a set of subepidermal cells near the abaxial surface of the anther. Localization in the developing endosperm, which is characterized by high protein synthesis rates, can be reconciled with a specific chaperone function. Equally, nectar production and secretion, a developmental stage marked by abundant ER, may require abundant CRT to accommodate the traffic of secretory proteins through the ER. Localization of CRT in the anthers, which are degenerating at the time of maximum expression of CRT, cannot easily be reconciled with a chaperone function but may indicate a role for CRT in anther maturation or dehiscence.

  13. Two endoplasmic reticulum proteins (calnexin and calreticulin) are involved in innate immunity in Chinese mitten crab (Eriocheir sinensis)

    PubMed Central

    Huang, Ying; Hui, Kaimin; Jin, Min; Yin, Shaowu; Wang, Wen; Ren, Qian

    2016-01-01

    Calnexin (Cnx) and calreticulin (Crt), which are important chaperones in the endoplasmic reticulum (ER), participate in the folding and quality control of client proteins. Cnx and Crt identified from Chinese mitten crab (Eriocheir sinensis) are designated as EsCnx and EsCrt, respectively. EsCnx and EsCrt are expressed in the hemocyte, hepatopancrea, gill, and intestine at the mRNA and protein level. Immunofluorescence analysis indicated that EsCnx and EsCRT are located in the ER. Moreover, the mRNA and protein expression levels of EsCnx and EsCrt were altered by challenge with lipopolysaccharides (LPS), peptidoglycans (PGN), Staphyloccocus aureus, and Vibrio parahaemolyticus. Recombinant EsCnx and EsCrt (rEsCnx and rEsCrt, respectively) proteins can bind to various Gram-positive and Gram-negative bacteria, as well as to different polysaccharides (LPS and PGN). rEsCnx and rEsCrt assisted in the clearance of V. parahaemolyticus in vivo, and the clearance efficiency was impaired after silencing of EsCnx and EsCrt. Our results suggest that the two ER proteins are involved in anti-bacterial immunity in E. sinensis. PMID:27279413

  14. Triatoma infestans Calreticulin: Gene Cloning and Expression of a Main Domain That Interacts with the Host Complement System.

    PubMed

    Weinberger, Katherine; Collazo, Norberto; Aguillón, Juan Carlos; Molina, María Carmen; Rosas, Carlos; Peña, Jaime; Pizarro, Javier; Maldonado, Ismael; Cattan, Pedro E; Apt, Werner; Ferreira, Arturo

    2017-02-08

    Triatoma infestans is an important hematophagous vector of Chagas disease, a neglected chronic illness affecting approximately 6 million people in Latin America. Hematophagous insects possess several molecules in their saliva that counteract host defensive responses. Calreticulin (CRT), a multifunctional protein secreted in saliva, contributes to the feeding process in some insects. Human CRT (HuCRT) and Trypanosoma cruzi CRT (TcCRT) inhibit the classical pathway of complement activation, mainly by interacting through their central S domain with complement component C1. In previous studies, we have detected CRT in salivary gland extracts from T. infestans We have called this molecule TiCRT. Given that the S domain is responsible for C1 binding, we have tested its role in the classical pathway of complement activation in vertebrate blood. We have cloned and characterized the complete nucleotide sequence of CRT from T. infestans, and expressed its S domain. As expected, this S domain binds to human C1 and, as a consequence, it inhibits the classical pathway of complement, at its earliest stage of activation, namely the generation of C4b. Possibly, the presence of TiCRT in the salivary gland represents an evolutionary adaptation in hematophagous insects to control a potential activation of complement proteins, present in the massive blood meal that they ingest, with deleterious consequences at least on the anterior digestive tract of these insects.

  15. Immunological mechanisms involved in the protection against intestinal taeniosis elicited by oral immunization with Taenia solium calreticulin.

    PubMed

    Leon-Cabrera, Sonia; Cruz-Rivera, Mayra; Mendlovic, Fela; Romero-Valdovinos, Mirza; Vaughan, Gilberto; Salazar, Ana María; Avila, Guillermina; Flisser, Ana

    2012-11-01

    Oral immunization with functional recombinant Taenia solium calreticulin (rTsCRT) induces 37% reduction in tapeworm burden in the experimental model of intestinal taeniosis in hamsters. Furthermore, tapeworms recovered from vaccinated animals exhibit diminished length, being frequently found in more posterior parts of the small intestine. The aim of this study was to analyze the immunological mechanisms involved in protection in response to rTsCRT oral immunization. Hamsters were orally immunized with rTsCRT using cholera toxin (CT) as adjuvant, weekly for 4 weeks. Fifteen days after the last boost animals were challenged with four T. solium cysticerci. Reduction in the adult worm recovery and increased transcription of mRNA for IL-4 and IFN-γ in the mucosa of rTsCRT+CT immunized animals were observed. Immunization also induced goblet cell hyperplasia in the mucosa surrounding the implantation site of the parasite. Specific IgG and IgA antibodies in serum and fecal supernatants were detected after the second immunization, being more pronounced after challenge. Our data suggest that oral vaccination with rTsCRT+CT regulates a local expression of IL-4 and IFN-γ, stimulating secretion of IgA that, together with the increase of goblet cells and mucin production, could result in an unfavorable environment for T. solium promoting an impaired tapeworm development.

  16. Detection of cell surface calreticulin as a potential cancer biomarker using near-infrared emitting gold nanoclusters

    NASA Astrophysics Data System (ADS)

    Subramaniyam Ramesh, Bala; Giorgakis, Emmanouil; Lopez-Davila, Victor; Kamali Dashtarzheneha, Ashkan; Loizidou, Marilena

    2016-07-01

    Calreticulin (CRT) is a cytoplasmic calcium-binding protein. The aim of this study was to investigate CRT presence in cancer with the use of fluorescent gold nanoclusters (AuNCs) and to explore AuNC synthesis using mercaptosuccinic acid (MSA) as a coating agent. MSA-coated AuNCs conferred well-dispersed, bio-stable, water-soluble nanoparticles with bioconjugation capacity and 800-850 nm fluorescence after broad-band excitation. Cell-viability assay revealed good AuNC tolerability. A native CRT amino-terminus corresponding peptide sequence was synthesised and used to generate rabbit site-specific antibodies. Target specificity was demonstrated with antibody blocking in colorectal and breast cancer cell models; human umbilical vein endothelial cells served as controls. We demonstrated a novel route of AuNC/MSA manufacture and CRT presence on colonic and breast cancerous cell surface. AuNCs served as fluorescent bio-probes specifically recognising surface-bound CRT. These results are promising in terms of AuNC application in cancer theranostics and CRT use as surface biomarker in human cancer.

  17. Artificial feeding of Rhipicephalus microplus female ticks with anti calreticulin serum do not influence tick and Babesia bigemina acquisition.

    PubMed

    Antunes, Sandra; Merino, Octávio; Lérias, Joana; Domingues, Nuno; Mosqueda, Juan; de la Fuente, José; Domingos, Ana

    2015-02-01

    Ticks are obligate haematophagous ectoparasites considered the principal vectors of disease among animals. Rhipicephalus microplus and R. annulatus ticks are the most important vectors for Babesia bigemina and B. bovis, two of the most important intraerythrocytic protozoan parasites species in cattle, responsible for babesiosis which together with anaplasmosis account for substantial economic losses in the livestock industry worldwide. Anti-tick vaccines are a proved alternative to traditional tick and tick borne diseases control methods but are still limited primarily due to the lack of effective antigens. Subsequently to the identification of antigens the validation is a laborious work often expensive. Tick artificial feeding, is a low cost alternative to test antigens allowing achieving critical data. Herein, R. microplus females were successfully artificially fed using capillary tubes. Calreticulin (CRT) protein, which in a previous study has been identified as being involved in B. bigemina infection in R. annulatus ticks, was expressed as recombinant protein (rCRT) in an E. coli expression system and antibodies raised against rCRT. Anti-rCRT serum was supplemented to a blood meal, offered to partially engorged R. microplus females and their effect in feeding process as well as infection by B. bigemina was analyzed. No significant reductions in tick and egg weight were observed when ticks fed with anti-rCRT serum. Furthermore, B. bigemina infection levels did not show a statistically significant decrease when ticks fed with anti-rCRT antibodies. Results suggest that CRT is not a suitable candidate for cattle vaccination trials.

  18. Calreticulin activates β1 integrin via fucosylation by fucosyltransferase 1 in J82 human bladder cancer cells.

    PubMed

    Lu, Yi-Chien; Chen, Chiung-Nien; Chu, Chia-Ying; Lu, Jenher; Wang, Bo-Jeng; Chen, Chia-Hua; Huang, Min-Chuan; Lin, Tsui-Hwa; Pan, Chin-Chen; Chen, Swey-Shen Alex; Hsu, Wen-Ming; Liao, Yung-Feng; Wu, Pei-Yi; Hsia, Hsin-Yi; Chang, Cheng-Chi; Lee, Hsinyu

    2014-05-15

    Fucosylation regulates various pathological events in cells. We reported that different levels of CRT (calreticulin) affect the cell adhesion and metastasis of bladder cancer. However, the precise mechanism of tumour metastasis regulated by CRT remains unclear. Using a DNA array, we identified FUT1 (fucosyltransferase 1) as a gene regulated by CRT expression levels. CRT regulated cell adhesion through α1,2-linked fucosylation of β1 integrin and this modification was catalysed by FUT1. To clarify the roles for FUT1 in bladder cancer, we transfected the human FUT1 gene into CRT-RNAi stable cell lines. FUT1 overexpression in CRT-RNAi cells resulted in increased levels of β1 integrin fucosylation and rescued cell adhesion to type-I collagen. Treatment with UEA-1 (Ulex europaeus agglutinin-1), a lectin that recognizes FUT1-modified glycosylation structures, did not affect cell adhesion. In contrast, a FUT1-specific fucosidase diminished the activation of β1 integrin. These results indicated that α1,2-fucosylation of β1 integrin was not involved in integrin-collagen interaction, but promoted β1 integrin activation. Moreover, we demonstrated that CRT regulated FUT1 mRNA degradation at the 3'-UTR. In conclusion, the results of the present study suggest that CRT stabilized FUT1 mRNA, thereby leading to an increase in fucosylation of β1 integrin. Furthermore, increased fucosylation levels activate β1 integrin, rather than directly modifying the integrin-binding sites.

  19. Catalyzed Ceramic Burner Material

    SciTech Connect

    Barnes, Amy S., Dr.

    2012-06-29

    Catalyzed combustion offers the advantages of increased fuel efficiency, decreased emissions (both NOx and CO), and an expanded operating range. These performance improvements are related to the ability of the catalyst to stabilize a flame at or within the burner media and to combust fuel at much lower temperatures. This technology has a diverse set of applications in industrial and commercial heating, including boilers for the paper, food and chemical industries. However, wide spread adoption of catalyzed combustion has been limited by the high cost of precious metals needed for the catalyst materials. The primary objective of this project was the development of an innovative catalyzed burner media for commercial and small industrial boiler applications that drastically reduce the unit cost of the catalyzed media without sacrificing the benefits associated with catalyzed combustion. The scope of this program was to identify both the optimum substrate material as well as the best performing catalyst construction to meet or exceed industry standards for durability, cost, energy efficiency, and emissions. It was anticipated that commercial implementation of this technology would result in significant energy savings and reduced emissions. Based on demonstrated achievements, there is a potential to reduce NOx emissions by 40,000 TPY and natural gas consumption by 8.9 TBtu in industries that heavily utilize natural gas for process heating. These industries include food manufacturing, polymer processing, and pulp and paper manufacturing. Initial evaluation of commercial solutions and upcoming EPA regulations suggests that small to midsized boilers in industrial and commercial markets could possibly see the greatest benefit from this technology. While out of scope for the current program, an extension of this technology could also be applied to catalytic oxidation for volatile organic compounds (VOCs). Considerable progress has been made over the course of the grant

  20. Antiproton catalyzed fusion

    SciTech Connect

    Morgan, D.L. Jr.; Perkins, L.J.; Haney, S.W.

    1995-05-15

    Because of the potential application to power production, it is important to investigate a wide range of possible means to achieve nuclear fusion, even those that may appear initially to be infeasible. In antiproton catalyzed fusion, the negative antiproton shields the repulsion between the positively charged nuclei of hydrogen isotopes, thus allowing a much higher level of penetration through the repulsive Coulomb barrier, and thereby greatly enhancing the fusion cross section. Because of their more compact wave function, the more massive antiprotons offer considerably more shielding than do negative muons. The effects of the shielding on fusion cross sections are most predominate, at low energies. If the antiproton could exist in the ground state with a nucleus for a sufficient time without annihilating, the fusion cross sections are so enhanced that at room temperature energies, values up to about 1,000 barns (that for d+t) would be possible. Unfortunately, the cross section for antiproton annihilation with the incoming nucleus is even higher. A model that provides an upper bound for the fusion to annihilation cross section for all relevant energies indicates that each antiproton will catalyze no more than about one fusion. Because the energy required to make one antiproton greatly exceeds the fusion energy that is released, this level of catalysis is far from adequate for power production.

  1. Functional cooperation between BiP and calreticulin in the folding maturation of a glycoprotein in Trypanosoma cruzi

    PubMed Central

    Labriola, Carlos A.; Villamil Giraldo, Ana M.; Parodi, Armando J.; Caramelo, Julio J.

    2011-01-01

    Proteins may adopt diverse conformations during their folding in vivo, ranging from extended chains when they emerge from the ribosome to compact intermediates near the end of the folding process. Accordingly, a variety of chaperones and folding assisting enzymes have evolved to deal with this diversity. Chaperone selection by a particular substrate depends on the structural features of its folding intermediates. In addition, this process may be modulated by competitive effects between chaperones. Here we address this issue by using TcrCATL as model substrate. TcrCATL is an abundant Trypanosoma cruzi lysosomal protease and it was the first identified endogenous UDP-Glc:glycoprotein glucosyltransferase (UGGT) substrate. We found that TcrCATL associated sequentially with BiP and calreticulin (CRT) during its folding process. Early, extended conformations were bound to BiP, while more advanced and compact folding intermediates associated to CRT. The interaction between TcrCATL and CRT was impeded by deletion of the UGGT-encoding gene but, similarly to what was observed in wild type cells, in mutant cells TcrCATL associated to BiP only when displaying extended conformations. The absence of TcrCATL–CRT interactions in UGGT null cells resulted in a drastic reduction of TcrCATL folding efficiency and triggered the aggregation of TcrCATL through intermolecular disulfide bonds. These observations show that BiP and CRT activities complement each other to supervise a complete and efficient TcrCATL folding process. The present report provides further evidence on the early evolutionary acquisition of the basic tenets of the N-glycan dependent quality control mechanism of glycoprotein folding. PMID:20934456

  2. A Nematode Calreticulin, Rs-CRT, Is a Key Effector in Reproduction and Pathogenicity of Radopholus similis

    PubMed Central

    Li, Yu; Wang, Ke; Xie, Hui; Wang, Yan-Tao; Wang, Dong-Wei; Xu, Chun-Lin; Huang, Xin; Wang, De-Sen

    2015-01-01

    Radopholus similis is a migratory plant-parasitic nematode that causes severe damage to many agricultural and horticultural crops. Calreticulin (CRT) is a Ca2+-binding multifunctional protein that plays key roles in the parasitism, immune evasion, reproduction and pathogenesis of many animal parasites and plant nematodes. Therefore, CRT is a promising target for controlling R. similis. In this study, we obtained the full-length sequence of the CRT gene from R. similis (Rs-crt), which is 1,527-bp long and includes a 1,206-bp ORF that encodes 401 amino acids. Rs-CRT and Mi-CRT from Meloidogyne incognita showed the highest similarity and were grouped on the same branch of the phylogenetic tree. Rs-crt is a multi-copy gene that is expressed in the oesophageal glands and gonads of females, the gonads of males, the intestines of juveniles and the eggs of R. similis. The highest Rs-crt expression was detected in females, followed by juveniles, eggs and males. The reproductive capability and pathogenicity of R. similis were significantly reduced after treatment with Rs-crt dsRNA for 36 h. Using plant-mediated RNAi, we confirmed that Rs-crt expression was significantly inhibited in the nematodes, and resistance to R. similis was significantly improved in transgenic tomato plants. Plant-mediated RNAi-induced silencing of Rs-crt could be effectively transmitted to the F2 generation of R. similis; however, the silencing effect of Rs-crt induced by in vitro RNAi was no longer detectable in F1 and F2 nematodes. Thus, Rs-crt is essential for the reproduction and pathogenicity of R. similis. PMID:26061142

  3. Honokiol confers immunogenicity by dictating calreticulin exposure, activating ER stress and inhibiting epithelial-to-mesenchymal transition.

    PubMed

    Liu, Shing-Hwa; Lee, Wen-Jane; Lai, De-Wei; Wu, Sheng-Mao; Liu, Chia-Yu; Tien, Hsing-Ru; Chiu, Chien-Shan; Peng, Yen-Chun; Jan, Yee-Jee; Chao, Te-Hsin; Pan, Hung-Chuan; Sheu, Meei-Ling

    2015-04-01

    Peritoneal dissemination is a major clinical obstacle in gastrointestinal cancer therapy, and it accounts for the majority of cancer-related mortality. Calreticulin (CRT) is over-expressed in gastric tumors and has been linked to poor prognosis. In this study, immunohistochemistry studies revealed that the up-regulation of CRT was associated with lymph node and distant metastasis in patients with gastric cancer specimens. CRT was significantly down-regulated in highly metastatic gastric cancer cell lines and metastatic animal by Honokiol-treated. Small RNA interference blocking CRT by siRNA-CRT was translocated to the cells in the early immunogenic response to Honokiol. Honokiol activated endoplasmic reticulum (ER) stress and down-regulated peroxisome proliferator-activated receptor-γ (PPARγ) activity resulting in PPARγ and CRT degradation through calpain-II activity, which could be reversed by siRNA-calpain-II. The Calpain-II/PPARγ/CRT axis and interaction evoked by Honokiol could be blocked by gene silencing or pharmacological agents. Both transforming growth factor (TGF)-β1 and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) induced cell migration, invasion and reciprocal down-regulation of epithelial marker E-cadherin, which could be abrogated by siRNA-CRT. Moreover, Honokiol significantly suppressed MNNG-induced gastrointestinal tumor growth and over-expression of CRT in mice. Knockdown CRT in gastric cancer cells was found to effectively reduce growth ability and metastasis in vivo. The present study provides insight into the specific biological behavior of CRT in epithelial-to-mesenchymal transition (EMT) and metastasis. Taken together, our results suggest that the therapeutic inhibition of CRT by Honokiol suppresses both gastric tumor growth and peritoneal dissemination by dictating early translocation of CRT in immunogenic cell death, activating ER stress, and blocking EMT. Copyright © 2015 Federation of European Biochemical Societies. Published by

  4. Role of calreticulin in the sensitivity of myocardiac H9c2 cells to oxidative stress caused by hydrogen peroxide.

    PubMed

    Ihara, Yoshito; Urata, Yoshishige; Goto, Shinji; Kondo, Takahito

    2006-01-01

    Calreticulin (CRT), a Ca2+-binding molecular chaperone in the endoplasmic reticulum, plays a vital role in cardiac physiology and pathology. Oxidative stress is a main cause of myocardiac apoptosis in the ischemic heart, but the function of CRT under oxidative stress is not fully understood. In the present study, the effect of overexpression of CRT on susceptibility to apoptosis under oxidative stress was examined using myocardiac H9c2 cells transfected with the CRT gene. Under oxidative stress due to H2O2, the CRT-overexpressing cells were highly susceptible to apoptosis compared with controls. In the overexpressing cells, the levels of cytoplasmic free Ca2+ ([Ca2+]i) were significantly increased by H2O2, whereas in controls, only a slight increase was observed. The H2O2-induced apoptosis was enhanced by the increase in [Ca2+]i caused by thapsigargin in control cells but was suppressed by BAPTA-AM, a cell-permeable Ca2+ chelator in the CRT-overexpressing cells, indicating the importance of the level of [Ca2+]i in the sensitivity to H2O2-induced apoptosis. Suppression of CRT by the introduction of the antisense cDNA of CRT enhanced cytoprotection against oxidative stress compared with controls. Furthermore, we found that the levels of activity of calpain and caspase-12 were elevated through the regulation of [Ca2+]i in the CRT-overexpressing cells treated with H2O2 compared with controls. Thus we conclude that the level of CRT regulates the sensitivity to apoptosis under oxidative stress due to H2O2 through a change in Ca2+ homeostasis and the regulation of the Ca2+-calpain-caspase-12 pathway in myocardiac cells.

  5. Calreticulin is a fine tuning molecule in epibrassinolide-induced apoptosis through activating endoplasmic reticulum stress in colon cancer cells.

    PubMed

    Obakan-Yerlikaya, Pinar; Arisan, Elif Damla; Coker-Gurkan, Ajda; Adacan, Kaan; Ozbey, Utku; Somuncu, Berna; Baran, Didem; Palavan-Unsal, Narcin

    2017-06-01

    Epibrassinolide (EBR), a member of brassinostreoids plant hormones with cell proliferation promoting role in plants, is a natural polyhydroxysteroid with structural similarity to steroid hormones of vertebrates. EBR has antiproliferative and apoptosis-inducing effect in various cancer cells. Although EBR has been shown to affect survival and mitochondria-mediated apoptosis pathways in a p53-independent manner, the exact molecular targets of EBR are still under investigation. Our recent SILAC (Stable Isotope Labeling by Amino Acids in Cell Culture) data showed that the most significantly altered protein after EBR treatment was calreticulin (CALR). CALR, a chaperone localized in endoplasmic reticulum (ER) lumen, plays role in protein folding and buffering Ca(2+) ions. The alteration of CALR may cause ER stress and unfolded protein response correspondingly the induction of apoptosis. Unfolded proteins are conducted to 26S proteasomal degradation following ubiquitination. Our study revealed that EBR treatment caused ER stress and UPR by altering CALR expression causing caspase-dependent apoptosis in HCT 116, HT29, DLD-1, and SW480 colon cancer cells. Furthermore, 48 h EBR treatment did not caused UPR in Fetal Human Colon cells (FHC) and Mouse Embryonic Fibroblast cells (MEF). In addition our findings showed that HCT 116 colon cancer cells lacking Bax and Puma expression still undergo UPR and related apoptosis. CALR silencing and rapamycin co-treatment prevented EBR-induced UPR and apoptosis, whereas 26S proteasome inhibition further increased the effect of EBR in colon cancer cells. All these findings showed that EBR is an ER stress and apoptotic inducer in colon cancer cells without affecting non-malignant cells. © 2017 Wiley Periodicals, Inc.

  6. Amblyomma americanum tick calreticulin binds C1q but does not inhibit activation of the classical complement cascade

    PubMed Central

    Kim, Tae Kwon; Ibelli, Adriana Mércia Guaratini; Mulenga, Albert

    2014-01-01

    In this study we characterized Amblyomma americanum (Aam) tick calreticulin (CRT) homolog in tick feeding physiology. In nature, different tick species can be found feeding on the same animal host. This suggests that different tick species found feeding on the same host can modulate the same host anti-tick defense pathways to successfully feed. From this perspective it’s plausible that different tick species can utilize universally conserved proteins such as CRT to regulate and facilitate feeding. CRT is a multi-functional protein found in most taxa that is injected into the vertebrate host during tick feeding. Apart from it’s current use as a biomarker for human tick bites, role(s) of this protein in tick feeding physiology have not been elucidated. Here we show that annotated functional CRT amino acid motifs are well conserved in tick CRT. However our data show that despite high amino acid identity levels to functionally characterized CRT homologs in other organisms, AamCRT is apparently functionally different. Pichia pastoris expressed recombinant (r) AamCRT bound C1q, the first component of the classical complement system, but it did not inhibit activation of this pathway. This contrast with reports of other parasite CRT that inhibited activation of the classical complement pathway through sequestration of C1q. Furthermore rAamCRT did not bind factor Xa in contrast to reports of parasite CRT binding factor Xa, an important protease in the blood clotting system. Consistent with this observation, rAamCRT did not affect plasma clotting or platelet aggregation aggregation. We discuss our findings in the context of tick feeding physiology. PMID:25454607

  7. The Ca(2+) status of the endoplasmic reticulum is altered by induction of calreticulin expression in transgenic plants

    NASA Technical Reports Server (NTRS)

    Persson, S.; Wyatt, S. E.; Love, J.; Thompson, W. F.; Robertson, D.; Boss, W. F.; Brown, C. S. (Principal Investigator)

    2001-01-01

    To investigate the endoplasmic reticulum (ER) Ca(2+) stores in plant cells, we generated tobacco (Nicotiana tabacum; NT1) suspension cells and Arabidopsis plants with altered levels of calreticulin (CRT), an ER-localized Ca(2+)-binding protein. NT1 cells and Arabidopsis plants were transformed with a maize (Zea mays) CRT gene in both sense and antisense orientations under the control of an Arabidopsis heat shock promoter. ER-enriched membrane fractions from NT1 cells were used to examine how altered expression of CRT affects Ca(2+) uptake and release. We found that a 2.5-fold increase in CRT led to a 2-fold increase in ATP-dependent (45)Ca(2+) accumulation in the ER-enriched fraction compared with heat-shocked wild-type controls. Furthermore, after treatment with the Ca(2+) ionophore ionomycin, ER microsomes from NT1 cells overproducing CRT showed a 2-fold increase in the amount of (45)Ca(2+) released, and a 2- to 3-fold increase in the amount of (45)Ca(2+) retained compared with wild type. These data indicate that altering the production of CRT affects the ER Ca(2+) pool. In addition, CRT transgenic Arabidopsis plants were used to determine if altered CRT levels had any physiological effects. We found that the level of CRT in heat shock-induced CRT transgenic plants correlated positively with the retention of chlorophyll when the plants were transferred from Ca(2+)-containing medium to Ca(2+)-depleted medium. Together these data are consistent with the hypothesis that increasing CRT in the ER increases the ER Ca(2+) stores and thereby enhances the survival of plants grown in low Ca(2+) medium.

  8. A Nematode Calreticulin, Rs-CRT, Is a Key Effector in Reproduction and Pathogenicity of Radopholus similis.

    PubMed

    Li, Yu; Wang, Ke; Xie, Hui; Wang, Yan-Tao; Wang, Dong-Wei; Xu, Chun-Lin; Huang, Xin; Wang, De-Sen

    2015-01-01

    Radopholus similis is a migratory plant-parasitic nematode that causes severe damage to many agricultural and horticultural crops. Calreticulin (CRT) is a Ca2+-binding multifunctional protein that plays key roles in the parasitism, immune evasion, reproduction and pathogenesis of many animal parasites and plant nematodes. Therefore, CRT is a promising target for controlling R. similis. In this study, we obtained the full-length sequence of the CRT gene from R. similis (Rs-crt), which is 1,527-bp long and includes a 1,206-bp ORF that encodes 401 amino acids. Rs-CRT and Mi-CRT from Meloidogyne incognita showed the highest similarity and were grouped on the same branch of the phylogenetic tree. Rs-crt is a multi-copy gene that is expressed in the oesophageal glands and gonads of females, the gonads of males, the intestines of juveniles and the eggs of R. similis. The highest Rs-crt expression was detected in females, followed by juveniles, eggs and males. The reproductive capability and pathogenicity of R. similis were significantly reduced after treatment with Rs-crt dsRNA for 36 h. Using plant-mediated RNAi, we confirmed that Rs-crt expression was significantly inhibited in the nematodes, and resistance to R. similis was significantly improved in transgenic tomato plants. Plant-mediated RNAi-induced silencing of Rs-crt could be effectively transmitted to the F2 generation of R. similis; however, the silencing effect of Rs-crt induced by in vitro RNAi was no longer detectable in F1 and F2 nematodes. Thus, Rs-crt is essential for the reproduction and pathogenicity of R. similis.

  9. The Ca(2+) status of the endoplasmic reticulum is altered by induction of calreticulin expression in transgenic plants

    NASA Technical Reports Server (NTRS)

    Persson, S.; Wyatt, S. E.; Love, J.; Thompson, W. F.; Robertson, D.; Boss, W. F.; Brown, C. S. (Principal Investigator)

    2001-01-01

    To investigate the endoplasmic reticulum (ER) Ca(2+) stores in plant cells, we generated tobacco (Nicotiana tabacum; NT1) suspension cells and Arabidopsis plants with altered levels of calreticulin (CRT), an ER-localized Ca(2+)-binding protein. NT1 cells and Arabidopsis plants were transformed with a maize (Zea mays) CRT gene in both sense and antisense orientations under the control of an Arabidopsis heat shock promoter. ER-enriched membrane fractions from NT1 cells were used to examine how altered expression of CRT affects Ca(2+) uptake and release. We found that a 2.5-fold increase in CRT led to a 2-fold increase in ATP-dependent (45)Ca(2+) accumulation in the ER-enriched fraction compared with heat-shocked wild-type controls. Furthermore, after treatment with the Ca(2+) ionophore ionomycin, ER microsomes from NT1 cells overproducing CRT showed a 2-fold increase in the amount of (45)Ca(2+) released, and a 2- to 3-fold increase in the amount of (45)Ca(2+) retained compared with wild type. These data indicate that altering the production of CRT affects the ER Ca(2+) pool. In addition, CRT transgenic Arabidopsis plants were used to determine if altered CRT levels had any physiological effects. We found that the level of CRT in heat shock-induced CRT transgenic plants correlated positively with the retention of chlorophyll when the plants were transferred from Ca(2+)-containing medium to Ca(2+)-depleted medium. Together these data are consistent with the hypothesis that increasing CRT in the ER increases the ER Ca(2+) stores and thereby enhances the survival of plants grown in low Ca(2+) medium.

  10. A calreticulin-dependent nuclear export signal is involved in the regulation of liver receptor homologue-1 protein folding.

    PubMed

    Yang, Feng-Ming; Feng, Shan-Jung; Lai, Tsai-Chun; Hu, Meng-Chun

    2015-10-15

    As an orphan member of the nuclear receptor family, liver receptor homologue-1 (LRH-1) controls a tremendous range of transcriptional programmes that are essential for metabolism and hormone synthesis. Our previous studies have shown that nuclear localization of the LRH-1 protein is mediated by two nuclear localization signals (NLSs) that are karyopherin/importin-dependent. It is unclear whether LRH-1 can be actively exported from the nucleus to the cytoplasm. In the present study, we describe a nuclear export domain containing two leucine-rich motifs [named nuclear export signal (NES)1 and NES2] within the ligand-binding domain (LBD). Mutation of leucine residues in NES1 or NES2 abolished nuclear export, indicating that both NES1 and NES2 motifs are essential for full nuclear export activity. This NES-mediated nuclear export was insensitive to the chromosomal region maintenance 1 (CRM1) inhibitor leptomycin B (LMB) or to CRM1 knockdown. However, knockdown of calreticulin (CRT) prevented NES-mediated nuclear export. Furthermore, our data show that CRT interacts with LRH-1 and is involved in the nuclear export of LRH-1. With full-length LRH-1, mutation of NES1 led to perinuclear accumulation of the mutant protein. Immunofluorescence analysis showed that these perinuclear aggregates were co-localized with the centrosome marker, microtubule-associated protein 1 light chain 3 (LC3), ubiquitin and heat shock protein 70 (Hsp70), indicating that the mutant was misfolded and sequestered into aggresome-like structures via the autophagic clearance pathway. Our study demonstrates for the first time that LRH-1 has a CRT-dependent NES which is not only required for cytoplasmic trafficking, but also essential for correct protein folding to avoid misfolding-induced aggregation. © 2015 Authors; published by Portland Press Limited.

  11. Hydroxide-catalyzed bonding

    NASA Technical Reports Server (NTRS)

    Gwo, Dz-Hung (Inventor)

    2003-01-01

    A method of bonding substrates by hydroxide-catalyzed hydration/dehydration involves applying a bonding material to at least one surface to be bonded, and placing the at least one surface sufficiently close to another surface such that a bonding interface is formed between them. A bonding material of the invention comprises a source of hydroxide ions, and may optionally include a silicate component, a particulate filling material, and a property-modifying component. Bonding methods of the invention reliably and reproducibly provide bonds which are strong and precise, and which may be tailored according to a wide range of possible applications. Possible applications for bonding materials of the invention include: forming composite materials, coating substrates, forming laminate structures, assembly of precision optical components, and preparing objects of defined geometry and composition. Bonding materials and methods of preparing the same are also disclosed.

  12. Poly(I:C) treatment influences the expression of calreticulin and profilin-1 in a human HNSCC cell line: a proteomic study.

    PubMed

    Matijević, Tanja; Pavelić, Jasminka

    2012-08-01

    Polyinosinic:polycytidylic acid (poly (I:C)) has been formerly known to be an interferon inducer but the mechanism of its action was not revealed until the discovery of Toll-like receptors (TLRs). TLRs are members of transmembrane proteins that recognize conserved molecular motifs of viral and bacterial origin and initiate innate immune response. Recent studies have shown that they are also expressed on tumor cells, but their role in these cells is still not clear. TLR3 recognizes double-stranded RNA (poly (I:C)) and is primarily involved in the defense against viruses. TLR3 ligand binding initiates the activation of transcription factors NF-κB, IRF family members, and AP-1, which can induce wide cascading effect on the cell and consequently activate many cellular processes. Since little is known about TLR3 target genes, we have used the proteomic approach to widen the current knowledge. In this study, we have discovered 15 differentially expressed proteins, mostly connected with protein metabolic processes. Furthermore, we have confirmed by Western blot that calreticulin and profilin-1, proteins which have been shown previously to be involved in processes connected with tumor progression, are differentially expressed after poly(I:C) treatment. By using TLR3 small interfering RNA, we showed that calreticulin expression might be TLR3 dependent, unlike profilin-1.

  13. Entamoeba histolytica and E. dispar Calreticulin: Inhibition of Classical Complement Pathway and Differences in the Level of Expression in Amoebic Liver Abscess

    PubMed Central

    Ximénez, Cecilia; González, Enrique; Nieves, Miriam E.; Silva-Olivares, Angélica; Shibayama, Mineko; Galindo-Gómez, Silvia; Escobar-Herrera, Jaime; García de León, Ma del Carmen; Morán, Patricia; Valadez, Alicia; Rojas, Liliana; Hernández, Eric G.; Partida, Oswaldo; Cerritos, René

    2014-01-01

    The role of calreticulin (CRT) in host-parasite interactions has recently become an important area of research. Information about the functions of calreticulin and its relevance to the physiology of Entamoeba parasites is limited. The present work demonstrates that CRT of both pathogenic E. histolytica and nonpathogenic E. dispar species specifically interacted with human C1q inhibiting the activation of the classical complement pathway. Using recombinant EhCRT protein, we demonstrate that CRT interaction site and human C1q is located at the N-terminal region of EhCRT. The immunofluorescence and confocal microscopy experiments show that CRT and human C1q colocalize in the cytoplasmic vesicles and near to the surface membrane of previously permeabilized trophozoites or are incubated with normal human serum which is known to destroy trophozoites. In the presence of peripheral mononuclear blood cells, the distribution of EhCRT and C1q is clearly over the surface membrane of trophozoites. Nevertheless, the level of expression of CRT in situ in lesions of amoebic liver abscess (ALA) in the hamster model is different in both Entamoeba species; this molecule is expressed in higher levels in E. histolytica than in E. dispar. This result suggests that EhCRT may modulate some functions during the early moments of the host-parasite relationship. PMID:24860808

  14. Entamoeba histolytica and E. dispar Calreticulin: inhibition of classical complement pathway and differences in the level of expression in amoebic liver abscess.

    PubMed

    Ximénez, Cecilia; González, Enrique; Nieves, Miriam E; Silva-Olivares, Angélica; Shibayama, Mineko; Galindo-Gómez, Silvia; Escobar-Herrera, Jaime; García de León, Ma Del Carmen; Morán, Patricia; Valadez, Alicia; Rojas, Liliana; Hernández, Eric G; Partida, Oswaldo; Cerritos, René

    2014-01-01

    The role of calreticulin (CRT) in host-parasite interactions has recently become an important area of research. Information about the functions of calreticulin and its relevance to the physiology of Entamoeba parasites is limited. The present work demonstrates that CRT of both pathogenic E. histolytica and nonpathogenic E. dispar species specifically interacted with human C1q inhibiting the activation of the classical complement pathway. Using recombinant EhCRT protein, we demonstrate that CRT interaction site and human C1q is located at the N-terminal region of EhCRT. The immunofluorescence and confocal microscopy experiments show that CRT and human C1q colocalize in the cytoplasmic vesicles and near to the surface membrane of previously permeabilized trophozoites or are incubated with normal human serum which is known to destroy trophozoites. In the presence of peripheral mononuclear blood cells, the distribution of EhCRT and C1q is clearly over the surface membrane of trophozoites. Nevertheless, the level of expression of CRT in situ in lesions of amoebic liver abscess (ALA) in the hamster model is different in both Entamoeba species; this molecule is expressed in higher levels in E. histolytica than in E. dispar. This result suggests that EhCRT may modulate some functions during the early moments of the host-parasite relationship.

  15. Dietary Yeast Cell Wall Extract Alters the Proteome of the Skin Mucous Barrier in Atlantic Salmon (Salmo salar): Increased Abundance and Expression of a Calreticulin-Like Protein.

    PubMed

    Micallef, Giulia; Cash, Phillip; Fernandes, Jorge M O; Rajan, Binoy; Tinsley, John W; Bickerdike, Ralph; Martin, Samuel A M; Bowman, Alan S

    2017-01-01

    In order to improve fish health and reduce use of chemotherapeutants in aquaculture production, the immunomodulatory effect of various nutritional ingredients has been explored. In salmon, there is evidence that functional feeds can reduce the abundance of sea lice. This study aimed to determine if there were consistent changes in the skin mucus proteome that could serve as a biomarker for dietary yeast cell wall extract. The effect of dietary yeast cell wall extract on the skin mucus proteome of Atlantic salmon was examined using two-dimensional gel electrophoresis. Forty-nine spots showed a statistically significant change in their normalised volumes between the control and yeast cell wall diets. Thirteen spots were successfully identified by peptide fragment fingerprinting and LC-MS/MS and these belonged to a variety of functions and pathways. To assess the validity of the results from the proteome approach, the gene expression of a selection of these proteins was studied in skin mRNA from two different independent feeding trials using yeast cell wall extracts. A calreticulin-like protein increased in abundance at both the protein and transcript level in response to dietary yeast cell wall extract. The calreticulin-like protein was identified as a possible biomarker for yeast-derived functional feeds since it showed the most consistent change in expression in both the mucus proteome and skin transcriptome. The discovery of such a biomarker is expected to quicken the pace of research in the application of yeast cell wall extracts.

  16. Dietary Yeast Cell Wall Extract Alters the Proteome of the Skin Mucous Barrier in Atlantic Salmon (Salmo salar): Increased Abundance and Expression of a Calreticulin-Like Protein

    PubMed Central

    Micallef, Giulia; Cash, Phillip; Fernandes, Jorge M. O.; Rajan, Binoy; Tinsley, John W.; Bickerdike, Ralph

    2017-01-01

    In order to improve fish health and reduce use of chemotherapeutants in aquaculture production, the immunomodulatory effect of various nutritional ingredients has been explored. In salmon, there is evidence that functional feeds can reduce the abundance of sea lice. This study aimed to determine if there were consistent changes in the skin mucus proteome that could serve as a biomarker for dietary yeast cell wall extract. The effect of dietary yeast cell wall extract on the skin mucus proteome of Atlantic salmon was examined using two-dimensional gel electrophoresis. Forty-nine spots showed a statistically significant change in their normalised volumes between the control and yeast cell wall diets. Thirteen spots were successfully identified by peptide fragment fingerprinting and LC-MS/MS and these belonged to a variety of functions and pathways. To assess the validity of the results from the proteome approach, the gene expression of a selection of these proteins was studied in skin mRNA from two different independent feeding trials using yeast cell wall extracts. A calreticulin-like protein increased in abundance at both the protein and transcript level in response to dietary yeast cell wall extract. The calreticulin-like protein was identified as a possible biomarker for yeast-derived functional feeds since it showed the most consistent change in expression in both the mucus proteome and skin transcriptome. The discovery of such a biomarker is expected to quicken the pace of research in the application of yeast cell wall extracts. PMID:28046109

  17. Mannan-binding lectin, a serum collectin, suppresses T-cell proliferation via direct interaction with cell surface calreticulin and inhibition of proximal T-cell receptor signaling.

    PubMed

    Zhao, Na; Wu, Jie; Xiong, Simin; Zhang, Liyun; Lu, Xiao; Chen, Shangliang; Wu, Qifeng; Wang, Hailan; Liu, Ying; Chen, Zhengliang; Zuo, Daming

    2017-06-01

    Mannan binding lectin (MBL), initially reported to activate the complement pathway, is also known to be involved in the pathogenesis of autoimmune diseases. We report a thus far unknown function of MBL as a suppressor of T-cell activation. MBL markedly inhibited T-cell proliferation induced by anti-CD3 and anti-CD28 antibodies. Moreover, the presence of MBL during T-cell priming interfered with proximal T-cell receptor signaling by decreasing phosphorylation of Lck, ZAP-70, and LAT. MBL bound to T cells through interaction between the collagen-like region of MBL and calreticulin (CRT) expressed on the T-cell surface. The neutralizing antibody against CRT abrogated MBL-mediated suppression of T-cell proliferation, suggesting that MBL down-modulates T-cell proliferation via cell surface CRT. We further demonstrated that the feature of MBL-mediated T-cell suppression is shared by other serum collectins (e.g., C1q and collectin 11). The concentrations of MBL correlated negatively with in vivo T-cell activation status in patients with early-stage silicosis. Furthermore, MBL efficiently inhibited activation and proliferation of autoreactive T cells derived from patients with silicosis, indicating that MBL serves as a negative feedback control of the T-cell responses.-Zhao, N., Wu, J., Xiong, S., Zhang, L., Lu, X., Chen, S., Wu, Q., Wang, H., Liu, Y., Chen, Z., Zuo, D. Mannan-binding lectin, a serum collectin, suppresses T-cell proliferation via direct interaction with cell surface calreticulin and inhibition of proximal T-cell receptor signaling. © FASEB.

  18. Sublethal exposure to alpha radiation (223Ra dichloride) enhances various carcinomas’ sensitivity to lysis by antigen-specific cytotoxic T lymphocytes through calreticulin-mediated immunogenic modulation

    PubMed Central

    Malamas, Anthony S.; Gameiro, Sofia R.; Knudson, Karin M.; Hodge, James W.

    2016-01-01

    Radium-223 dichloride (Xofigo®; 223Ra) is an alpha-emitting radiopharmaceutical FDA-approved for the treatment of bone metastases in patients with advanced castration-resistant prostate cancer. It is also being examined clinically in patients with breast and lung carcinoma and patients with multiple myeloma. As with other forms of radiation, the aim of 223Ra is to reduce tumor burden by directly killing tumor cells. External beam (photon) and proton radiation have been shown to augment tumor sensitivity to antigen-specific CD8+ cytotoxic T lymphocytes (CTLs). However, little is known about whether treatment with 223Ra can also induce such immunogenic modulation in tumor cells that survive irradiation. We examined these effects in vitro by exposing human prostate, breast, and lung carcinoma cells to sublethal doses of 223Ra. 223Ra significantly enhanced T cell-mediated lysis of each tumor type by CD8+ CTLs specific for MUC-1, brachyury, and CEA tumor antigens. Immunofluorescence analysis revealed that the increase in CTL killing was accompanied by augmented protein expression of MHC-I and calreticulin in each tumor type, molecules that are essential for efficient antigen presentation. Enhanced tumor-cell lysis was facilitated by calreticulin surface translocation following 223Ra exposure. The phenotypic changes observed after treatment appear to be mediated by induction of the endoplasmic reticulum stress response pathway. By rendering tumor cells more susceptible to T cell-mediated lysis, 223Ra may potentially be effective in combination with various immunotherapies, particularly cancer vaccines that are designed to generate and expand patients’ endogenous antigen-specific T-cell populations against specific tumor antigens. PMID:27893426

  19. Sublethal exposure to alpha radiation (223Ra dichloride) enhances various carcinomas' sensitivity to lysis by antigen-specific cytotoxic T lymphocytes through calreticulin-mediated immunogenic modulation.

    PubMed

    Malamas, Anthony S; Gameiro, Sofia R; Knudson, Karin M; Hodge, James W

    2016-12-27

    Radium-223 dichloride (Xofigo®; 223Ra) is an alpha-emitting radiopharmaceutical FDA-approved for the treatment of bone metastases in patients with advanced castration-resistant prostate cancer. It is also being examined clinically in patients with breast and lung carcinoma and patients with multiple myeloma. As with other forms of radiation, the aim of 223Ra is to reduce tumor burden by directly killing tumor cells. External beam (photon) and proton radiation have been shown to augment tumor sensitivity to antigen-specific CD8+ cytotoxic T lymphocytes (CTLs). However, little is known about whether treatment with 223Ra can also induce such immunogenic modulation in tumor cells that survive irradiation. We examined these effects in vitro by exposing human prostate, breast, and lung carcinoma cells to sublethal doses of 223Ra. 223Ra significantly enhanced T cell-mediated lysis of each tumor type by CD8+ CTLs specific for MUC-1, brachyury, and CEA tumor antigens. Immunofluorescence analysis revealed that the increase in CTL killing was accompanied by augmented protein expression of MHC-I and calreticulin in each tumor type, molecules that are essential for efficient antigen presentation. Enhanced tumor-cell lysis was facilitated by calreticulin surface translocation following 223Ra exposure. The phenotypic changes observed after treatment appear to be mediated by induction of the endoplasmic reticulum stress response pathway. By rendering tumor cells more susceptible to T cell-mediated lysis, 223Ra may potentially be effective in combination with various immunotherapies, particularly cancer vaccines that are designed to generate and expand patients' endogenous antigen-specific T-cell populations against specific tumor antigens.

  20. Calreticulin discriminates the proximal region at the N-glycosylation site of Glc1Man9GlcNAc2 ligand

    SciTech Connect

    Hirano, Makoto; Adachi, Yuka; Ito, Yukishige; Totani, Kiichiro

    2015-10-23

    Calreticulin (CRT) is well known as a lectin-like chaperone that recognizes Glc1Man9GlcNAc2 (G1M9)-glycoproteins in the endoplasmic reticulum (ER). However, whether CRT can directly interact with the aglycone moiety (protein portion) of the glycoprotein remains controversial. To improve our understanding of CRT interactions, structure-defined G1M9-derivatives with different aglycones (–OH, –Gly–NH{sub 2}, and –Gly–Glu–{sup t}Bu) were used as CRT ligands, and their interactions with recombinant CRT were analyzed using thermal shift analysis. The results showed that CRT binds strongly to a G1M9-ligand in the order –Gly–Glu–{sup t}Bu > –Gly–NH{sub 2} > –OH, which is the same as that of the reglucosylation of Man9GlcNAc2 (M9)-derivatives by the folding sensor enzyme UGGT (UDP-glucose: glycoprotein glucosyltransferase). Our results indicate that, similar to UGGT, CRT discriminates the proximal region at the N-glycosylation site, suggesting a similar mechanism mediating the recognition of aglycone moieties in the ER glycoprotein quality control system. - Highlights: • Glc1Man9GlcNAc2 (G1M9) ligands with different aglycones were chemically prepared. • Calreticulin (CRT) discriminates the aglycone of Glc1Man9GlcNAc2 (G1M9) ligand. • CRT binds with G1M9 ligands in a similar manner to folding sensor enzyme.

  1. DNA-Catalyzed Amide Hydrolysis

    PubMed Central

    Zhou, Cong; Avins, Joshua L.; Klauser, Paul C.; Brandsen, Benjamin M.; Lee, Yujeong; Silverman, Scott K.

    2016-01-01

    DNA catalysts (deoxyribozymes) for a variety of reactions have been identified by in vitro selection. However, for certain reactions this identification has not been achieved. One important example is DNA-catalyzed amide hydrolysis, for which a previous selection experiment instead led to DNA-catalyzed DNA phosphodiester hydrolysis. Subsequent efforts in which the selection strategy deliberately avoided phosphodiester hydrolysis led to DNA-catalyzed ester and aromatic amide hydrolysis, but aliphatic amide hydrolysis has been elusive. In the present study, we show that including modified nucleotides that bear protein-like functional groups (any one of primary amino, carboxyl, or primary hydroxyl) enables identification of amide-hydrolyzing deoxyribozymes. In one case, the same deoxyribozyme sequence without the modifications still retains substantial catalytic activity. Overall, these findings establish the utility of introducing protein-like functional groups into deoxyribozymes for identifying new catalytic function. The results also suggest the longer-term feasibility of deoxyribozymes as artificial proteases. PMID:26854515

  2. Iodine-Catalyzed Polysaccharide Esterification

    USDA-ARS?s Scientific Manuscript database

    A review is provided of the recent reports to use iodine-catalyzed esterification reaction to produce esters from polysaccharides. The process entails reaction of the polysaccharide with an acid anhydride in the presence of a catalytic level of iodine, and in the absence of additional solvents. T...

  3. Performance of catalyzed hydrazine in field applications

    SciTech Connect

    Allgood, T.B.

    1987-01-01

    The performance of newly developed oxygen scavengers for boilers is often compared to sulfite and hydrazine. Catalyzed hydrazine out-performs hydrazine and might be preferred when catalyzed sulfite cannot be used. Data from a Midwest Utility confirms that, under field conditions, catalyzed hydrazine out-performance hydrazine and carbohydrazine when feedwater oxygen and iron levels were critical. Catalyzed hydrazine might be preferred when high performance and economics are the primary concerns.

  4. Gold-catalyzed domino reactions.

    PubMed

    Michelet, Véronique

    2015-01-01

    Gold-catalyzed reactions have appeared to be highly attractive tools for chemists to promote novel transformations to prepare elaborated structures from simple starting materials. This chapter presents selected and original examples of domino processes in the presence of gold catalysts, highlighting reports implying hydration, hydroxylation, and hydroamination as key starting point for cascade transformations. Domino processes implying 1,n-enynes, asymmetric domino transformations, and applications of all the presented processes in total synthesis are presented.

  5. Biochemical and ultrastructural correlations of calreticulin and thioredoxin expression in breast mucinous carcinoma and infiltrating ductal carcinoma non-special type.

    PubMed

    Baltatzis, G E; Gaitanarou, H; Arnogianaki, N; Misitzis, J; Voloudakis-Baltatzis, I E

    2011-02-01

    Mucinous infiltrating invasive ductal adenocarcinoma consists of 2-4% invasive breast cancer, but is a very interesting type due to its macroscopic similarity to non-special-type (NST) ductal carcinoma. The macroscopic similarity of mucinous and infiltrating ductal carcinoma NST adenocarcinomas consists of a loose and edematous stroma, which is often seen in portions of NST carcinoma and may mimic the mucin pools of mucinous carcinoma. In this study the authors examined the ultrastructural differences between mucinous carcinoma and infiltrating ductal carcinoma NST. They also examined the protein expression of the tissues by 2D electrophoresis due to their belief that from the results of these two levels it is possible to understand the changes that take place both in the ultrastructural and biochemical levels in these two types of breast cancer. The ultrastructural results from mucinous carcinoma have shown many changes in cytoplasmic organelles in comparison to normal samples, depending on the grade and the number of metastatic lymph nodes. At the 2D elecrophoresis level the authors studied two interesting polypeptides, calreticulin and thioredoxin. Both of these proteins were found in patterns of fibroadenoma, mucinous carcinoma, and NST carcinoma, but with different quantitative expression among them. In the future the quantitative differences of these two proteins may provide specific tumor markers for these two types of carcinoma.

  6. Adjuvanticity of a Recombinant Calreticulin Fragment in Assisting Anti-β-Glucan IgG Responses in T Cell-Deficient Mice

    PubMed Central

    Li, Wei-Ji; Long, Kai; Dong, Hong-Liang

    2013-01-01

    Polysaccharide-encapsulated fungi are the chief source of diseases in immunocompromised hosts such as those infected with human immunodeficiency virus or neutropenia patients. Currently available polysaccharide-protein conjugate vaccines are mainly T cell dependent and are usually ineffective in weakened immune systems. In this study, laminarin, a well-characterized β-1,3-glucan, was conjugated with a prokaryotically expressed recombinant fragment (amino acids [aa] 39 to 272) of calreticulin (rCRT/39–272), which exhibits extraordinarily potent immunogenicity and adjuvanticity in experimental animals. The resultant conjugate reserves the immunostimulatory effect of rCRT/39–272 on naïve murine B cells and is capable of eliciting anti-β-glucan IgG (mostly IgG1) responses in not only BALB/c mice but also athymic nude mice. Laminarin-CRT-induced mouse antibodies (Abs) are able to bind with Candida albicans and inhibit its growth in vitro. In addition, vaccination with laminarin-CRT partially protects mice from lethal C. albicans challenge. These results imply that rCRT/39–272 could be used as an ideal carrier or adjuvant for carbohydrate vaccines aimed at inducing or boosting IgG responses to fungal infections in immunodeficient hosts. PMID:23408527

  7. Ectopic expression of a maize calreticulin mitigates calcium deficiency-like disorders in sCAX1-expressing tobacco and tomato.

    PubMed

    Wu, Qingyu; Shigaki, Toshiro; Han, Jeung-Sul; Kim, Chang Kil; Hirschi, Kendal D; Park, Sunghun

    2012-12-01

    Deregulated expression of an Arabidopsis H⁺/Ca²⁺ antiporter (sCAX1) in agricultural crops increases total calcium (Ca²⁺) but may result in yield losses due to Ca²⁺ deficiency-like symptoms. Here we demonstrate that co-expression of a maize calreticulin (CRT, a Ca²⁺ binding protein located at endoplasmic reticulum) in sCAX1-expressing tobacco and tomato plants mitigated these adverse effects while maintaining enhanced Ca²⁺ content. Co-expression of CRT and sCAX1 could alleviate the hypersensitivity to ion imbalance in tobacco plants. Furthermore, blossom-end rot (BER) in tomato may be linked to changes in CAX activity and enhanced CRT expression mitigated BER in sCAX1 expressing lines. These findings suggest that co-expressing Ca²⁺ transporters and binding proteins at different intracellular compartments can alter the content and distribution of Ca²⁺ within the plant matrix.

  8. Trypanosoma cruzi carrying a monoallelic deletion of the calreticulin (TcCRT) gene are susceptible to complement mediated killing and defective in their metacyclogenesis.

    PubMed

    Sánchez Valdéz, Fernando J; Pérez Brandán, Cecilia; Zago, M Paola; Labriola, Carlos; Ferreira, Arturo; Basombrío, Miguel Ángel

    2013-03-01

    Trypanosoma cruzi calreticulin (TcCRT) can hijack complement C1, mannan-binding lectin and ficolins from serum thus inhibiting the classical and lectin complement pathway activation respectively. To understand the in vivo biological functions of TcCRT in T. cruzi we generated a clonal cell line lacking one TcCRT allele (TcCRT+/-) and another clone overexpressing it (TcCRT+). Both clones were derived from the TCC T. cruzi strain. As expected, TcCRT+/- epimastigotes showed impairment on TcCRT synthesis, whereas TcCRT+ ones showed increased protein levels. In correlation to this, monoallelic mutant parasites were significantly susceptible to killing by the complement machinery. On the contrary, TcCRT+ parasites showed higher levels of resistance to killing mediate by the classical and lectin but not the alternative pathway. The involvement of surface TcCRT in depleting C1 was demonstrated through restoration of serum killing activity by addition of exogenous C1. In axenic cultures, a reduced propagation rate of TcCRT+/- parasites was observed. Moreover, TcCRT+/- parasites presented a reduced rate of differentiation in in vitro assays. As shown by down- or upregulation of TcCRT expression this gene seems to play a major role in providing T. cruzi with the ability to resist complement system. Copyright © 2012 Elsevier Ltd. All rights reserved.

  9. Thermodynamics of Enzyme-Catalyzed Reactions Database

    National Institute of Standards and Technology Data Gateway

    SRD 74 Thermodynamics of Enzyme-Catalyzed Reactions Database (Web, free access)   The Thermodynamics of Enzyme-Catalyzed Reactions Database contains thermodynamic data on enzyme-catalyzed reactions that have been recently published in the Journal of Physical and Chemical Reference Data (JPCRD). For each reaction the following information is provided: the reference for the data, the reaction studied, the name of the enzyme used and its Enzyme Commission number, the method of measurement, the data and an evaluation thereof.

  10. Iridium-Catalyzed Allylic Substitution

    NASA Astrophysics Data System (ADS)

    Hartwig, John F.; Pouy, Mark J.

    Iridium-catalyzed asymmetric allylic substitution has become a valuable method to prepare products from the addition of nucleophiles at the more substituted carbon of an allyl unit. The most active and selective catalysts contain a phosphoramidite ligand possessing at least one arylethyl substituent on the nitrogen atom of the ligand. In these systems, the active catalyst is generated by a base-induced cyclometalation at the methyl group of this substituent to generate an iridium metalacycle bound by the COD ligand of the [Ir(COD)Cl]2 precursor and one additional labile dative ligand. Such complexes catalyze the reactions of linear allylic esters with alkylamines, arylamines, phenols, alcohols, imides, carbamates, ammonia, enolates and enolate equivalents, as well as typical stabilized carbon nucleophiles generated from malonates and cyanoesters. Iridium catalysts for enantioselective allylic substitution have also been generated from phosphorus ligands with substituents bound by heteroatoms, and an account of the studies of such systems, along with a description of the development of iridium catalysts is included.

  11. The Competence Of 7,8-Diacetoxy-4-Methylcoumarinand Other Polyphenolic Acetates In Mitigating The Oxidative Stress And Their Role In Angiogenesis.

    PubMed

    Joshi, Rini; Arora, Shvetambri; Kumar, Ajit; Manral, Sushma; Rohil, Vishwajeet; Goel, Sanjay; Priya, Nivedita; Singh, Prabhjot; Ponnan, Prija; Chatterji, Suvro; Dwarakanath, Bilikere S; Saluja, Daman; Rawat, Diwan S; Prasad, Ashok K; Saso, Luciano; Kohli, Ekta; DePass, Anthony L; Bracke, Marc E; Parmar, Virinder S; Raj, Hanumantharao G

    2014-12-09

    The potential role of polyphenolic acetate (PA) in causing diverse biological and pharmacological actions has been well studied in our laboratory. Our investigations, for the first time, established the role of calreticulin transacetylase (CRTAase) in catalyzing the acetylation of nitric oxide synthase (NOS) by Pas leading to robust activation of NOS. 7, 8-Diacetoxy-4-methylcoumarin (DAMC) and other acetoxycoumarins augmented the expression of thioredoxin (TRX) and vascular endothelial growth factor (VEGF) in human peripheral blood mononuclear cells (PBMCs). These findings substantiated our earlier observations that DAMC was a superb inducer of angiogenesis. The enhanced expression of thioredoxin reductase (TRXR) and diminished expression of thioredoxin interacting protein (TRXIP) leading to increased expression and activity of TRX in PBMCs due to the action of DAMC was revealed by real time RT-PCR analysis. The possible activation of TRX due to acetylation was confirmed by the fact that TRX activity of PBMCs was enhanced by variousacetoxycoumarins in tune with their affinities to CRTAase as substrates. DAMC caused enhanced production of NO by way of acetylation of NOS as mentioned above and thereby acted as an inducer of VEGF. Real time RT-PCR and VEGF ELISA results also revealed the overexpression of TRX. DAMC and other PAs were found to reduce the oxidative stress in cells as proved by significant reduction of intracellular ROS levels. Thus, the crucial role of TRX in DAMC-induced angiogenesis with the involvement of VEGF was established.

  12. The Competence of 7,8-Diacetoxy-4-Methylcoumarin and Other Polyphenolic Acetates in Mitigating the Oxidative Stress and their Role in Angiogenesis.

    PubMed

    Joshi, Rini; Arora, Shvetambri; Kumar, Ajit; Manral, Sushma; Rohil, Vishwajeet; Goel, Sanjay; Priya, Nivedita; Singh, Prabhjot; Ponnan, Prija; Chatterji, Suvro; Dwarakanath, Bilikere S; Saluja, Daman; Rawat, Diwan S; Prasad, Ashok K; Saso, Luciano; Kohli, Ekta; DePass, Anthony L; Bracke, Marc E; Parmar, Virinder S; Raj, Hanumantharao G

    2015-01-01

    The potential role of polyphenolic acetate (PA) in causing diverse biological and pharmacological actions has been well studied in our laboratory. Our investigations, for the first time, established the role of calreticulin transacetylase (CRTAase) in catalyzing the acetylation of nitric oxide synthase (NOS) by Pas leading to robust activation of NOS. 7, 8- Diacetoxy-4-methylcoumarin (DAMC) and other acetoxycoumarins augmented the expression of thioredoxin (TRX) and vascular endothelial growth factor (VEGF) in human peripheral blood mononuclear cells (PBMCs). These findings substantiated our earlier observations that DAMC was a superb inducer of angiogenesis. The enhanced expression of thioredoxin reductase (TRXR) and diminished expression of thioredoxin interacting protein (TRXIP) leading to increased expression and activity of TRX in PBMCs due to the action of DAMC was revealed by real time RT-PCR analysis. The possible activation of TRX due to acetylation was confirmed by the fact that TRX activity of PBMCs was enhanced by various acetoxycoumarins in tune with their affinities to CRTAase as substrates. DAMC caused enhanced production of NO by way of acetylation of NOS as mentioned above and thereby acted as an inducer of VEGF. Real time RT-PCR and VEGF ELISA results also revealed the overexpression of TRX. DAMC and other PAs were found to reduce the oxidative stress in cells as proved by significant reduction of intracellular ROS levels. Thus, the crucial role of TRX in DAMC-induced angiogenesis with the involvement of VEGF was established.

  13. In silico analyses of heat shock protein 60 and calreticulin to designing a novel vaccine shifting immune response toward T helper 2 in atherosclerosis.

    PubMed

    Karkhah, Ahmad; Saadi, Mahdiye; Nouri, Hamid Reza

    2017-04-01

    Recent experiments demonstrated that atherosclerosis is a Th1 dominant autoimmune condition, whereas Th2 cells are rarely detected within the atherosclerotic lesions. Several studies have indicated that Th2 type cytokines could be effective in the reduction and stabilization of atherosclerotic plaque. Therefore, the modulation of the adaptive immune response by shifting immune responses toward Th2 cells by a novel vaccine could represent a promising approach to prevent from progression and thromboembolic events in coronary artery disease. In the present study, an in silico approach was applied to design a novel multi-epitope vaccine to elicit a desirable immune response against atherosclerosis. Six novel IL-4 inducing epitopes were selected from HSP60 and calreticulin proteins. To enhance epitope presentation, IL-4 inducing epitopes were linked together by AAY and HEYGAEALERAG linkers. In addition, helper epitopes selected from Tetanus toxin fragment C (TTFrC) were applied to induce CD4+ helper T lymphocytes (HTLs) responses. Moreover, cholera toxin B (CTB) was employed as an adjuvant. A multi-epitope construct was designed based on predicted epitopes which was 320 residues in length. Then, the physico-chemical properties, secondary and tertiary structures, stability, intrinsic protein disorder, solubility and allergenicity of this chimeric protein were analyzed using bioinformatics tools and servers. Based on bioinformatics analysis, a soluble, and non-allergic protein with 35.405kDa molecular weight was designed. Expasy ProtParam classified this chimeric protein as a stable protein. In addition, predicted epitopes in the chimeric vaccine indicated strong potential to induce B-cell mediated immune response and shift immune responses toward protective Th2 immune response. Various in silico analyses indicate that this vaccine is a qualified candidate for improvement of atherosclerosis by inducing immune responses toward T helper 2.

  14. Nicotiana benthamiana calreticulin 3a is required for the ethylene-mediated production of phytoalexins and disease resistance against oomycete pathogen Phytophthora infestans.

    PubMed

    Matsukawa, Mizuki; Shibata, Yusuke; Ohtsu, Mina; Mizutani, Aki; Mori, Hitoshi; Wang, Ping; Ojika, Makoto; Kawakita, Kazuhito; Takemoto, Daigo

    2013-08-01

    Mature Nicotiana benthamiana shows strong resistance to the potato late blight pathogen Phytophthora infestans. By screening using virus-induced random gene silencing, we isolated a gene for plant-specific calreticulin NbCRT3a as a required gene for resistance of N. benthamiana against P. infestans. NbCRT3a encodes an endoplasmic reticulum quality-control (ERQC) chaperone for the maturation of glycoproteins, including glycosylated cell-surface receptors. NbCRT3a-silenced plants showed no detectable growth defects but resistance to P. infestans was significantly compromised. Defense responses induced by the treatment with INF1 (a secretory protein of P. infestans), such as production of reactive oxygen species and accumulation of phytoalexins, were suppressed in NbCRT3a-silenced N. benthamiana. Expression of an ethylene-regulated gene for phytoalexin biosynthesis, NbEAS, was reduced in NbCRT3a-silenced plants, whereas the expression of salicylic acid-regulated NbPR-1a was not affected. Consistently, induction of ethylene production by INF1 was suppressed in NbCRT3a-silenced plants. Resistance reactions induced by a hyphal wall components elicitor prepared from P. infestans were also impaired in NbCRT3a-silenced plants. However, cell death induced by active mitogen-activated protein kinase kinase (NbMEK2(DD)) was not affected by the silencing of NbCRT3a. Thus, NbCRT3a is required for the initiation of resistance reactions of N. benthamiana in response to elicitor molecules derived from P. infestans.

  15. The nerve growth factor alters calreticulin translocation from the endoplasmic reticulum to the cell surface and its signaling pathway in epithelial ovarian cancer cells.

    PubMed

    Vera, Carolina Andrea; Oróstica, Lorena; Gabler, Fernando; Ferreira, Arturo; Selman, Alberto; Vega, Margarita; Romero, Carmen Aurora

    2017-02-28

    Ovarian cancer is the seventh most common cancer among women worldwide, causing approximately 120,000 deaths every year. Immunotherapy, designed to boost the body's natural defenses against cancer, appears to be a promising option against ovarian cancer. Calreticulin (CRT) is an endoplasmic reticulum (ER) resident chaperone that, translocated to the cell membrane after ER stress, allows cancer cells to be recognized by the immune system. The nerve growth factor (NGF) is a pro-angiogenic molecule overexpressed in this cancer. In the present study, we aimed to determine weather NGF has an effect in CRT translocation induced by cytotoxic and ER stress. We treated A2780 ovarian cancer cells with NGF, thapsigargin (Tg), an ER stress inducer and mitoxantrone (Mtx), a chemotherapeutic drug; CRT subcellular localization was analyzed by immunofluorescence followed by confocal microscopy. In order to determine NGF effect on Mtx and Tg-induced CRT translocation from the ER to the cell membrane, cells were preincubated with NGF prior to Mtx or Tg treatment and CRT translocation to the cell surface was determined by flow cytometry. In addition, by western blot analyses, we evaluated proteins associated with the CRT translocation pathway, both in A2780 cells and human ovarian samples. We also measured NGF effect on cell apoptosis induced by Mtx. Our results indicate that Mtx and Tg, but not NGF, induce CRT translocation to the cell membrane. NGF, however, inhibited CRT translocation induced by Mtx, while it had no effect on Tg-induced CRT exposure. NGF also diminished cell death induced by Mtx. NGF effect on CRT translocation could have consequences in immunotherapy, potentially lessening the effectiveness of this type of treatment.

  16. Molecular cloning and transcriptional activity of a new Petunia calreticulin gene involved in pistil transmitting tract maturation, progamic phase, and double fertilization.

    PubMed

    Lenartowski, Robert; Suwińska, Anna; Prusińska, Justyna; Gumowski, Krzysztof; Lenartowska, Marta

    2014-02-01

    Calreticulin (CRT) is a highly conserved and ubiquitously expressed Ca²⁺-binding protein in multicellular eukaryotes. As an endoplasmic reticulum-resident protein, CRT plays a key role in many cellular processes including Ca²⁺ storage and release, protein synthesis, and molecular chaperoning in both animals and plants. CRT has long been suggested to play a role in plant sexual reproduction. To begin to address this possibility, we cloned and characterized the full-length cDNA of a new CRT gene (PhCRT) from Petunia. The deduced amino acid sequence of PhCRT shares homology with other known plant CRTs, and phylogenetic analysis indicates that the PhCRT cDNA clone belongs to the CRT1/CRT2 subclass. Northern blot analysis and fluorescent in situ hybridization were used to assess PhCRT gene expression in different parts of the pistil before pollination, during subsequent stages of the progamic phase, and at fertilization. The highest level of PhCRT mRNA was detected in the stigma-style part of the unpollinated pistil 1 day before anthesis and during the early stage of the progamic phase, when pollen is germinated and tubes outgrow on the stigma. In the ovary, PhCRT mRNA was most abundant after pollination and reached maximum at the late stage of the progamic phase, when pollen tubes grow into the ovules and fertilization occurs. PhCRT mRNA transcripts were seen to accumulate predominantly in transmitting tract cells of maturing and receptive stigma, in germinated pollen/growing tubes, and at the micropylar region of the ovule, where the female gametophyte is located. From these results, we suggest that PhCRT gene expression is up-regulated during secretory activity of the pistil transmitting tract cells, pollen germination and outgrowth of the tubes, and then during gamete fusion and early embryogenesis.

  17. Gold-catalyzed naphthalene functionalization

    PubMed Central

    Rivilla, Iván

    2011-01-01

    Summary The complexes IPrMCl (IPr = 1,3-bis(diisopropylphenyl)imidazol-2-ylidene, M = Cu, 1a; M = Au, 1b), in the presence of one equiv of NaBAr'4 (Ar' = 3,5-bis(trifluoromethyl)phenyl), catalyze the transfer of carbene groups: C(R)CO2Et (R = H, Me) from N2C(R)CO2Et to afford products that depend on the nature of the metal center. The copper-based catalyst yields exclusively a cycloheptatriene derivative from the Buchner reaction, whereas the gold analog affords a mixture of products derived either from the formal insertion of the carbene unit into the aromatic C–H bond or from its addition to a double bond. In addition, no byproducts derived from carbene coupling were observed. PMID:21647320

  18. Trypsin-Catalyzed Deltamethrin Degradation

    PubMed Central

    Xiong, Chunrong; Fang, Fujin; Chen, Lin; Yang, Qinggui; He, Ji; Zhou, Dan; Shen, Bo; Ma, Lei; Sun, Yan; Zhang, Donghui; Zhu, Changliang

    2014-01-01

    To explore if trypsin could catalyze the degradation of non-protein molecule deltamethrin, we compared in vitro hydrolytic reactions of deltamethrin in the presence and absence of trypsin with ultraviolet-visible (UV/Vis) spectrophotometry and gas chromatography-mass spectrometry (GC/MS). In addition, acute oral toxicity of the degradation products was determined in Wistar rats. The results show that the absorption peak of deltamethrin is around 264 nm, while the absorption peaks of deltamethrin degradation products are around 250 nm and 296 nm. In our GC setting, the retention time of undegraded deltamethrin was 37.968 min, while those of deltamethrin degradation products were 15.289 min and 18.730 min. The LD50 of deltamethrin in Wistar rats is 55 mg/kg, while that of deltamethrin degradation products is 3358 mg/kg in female rats and 1045 mg/kg in male rates (61-fold and 19-fold reductions in toxicity), suggesting that trypsin could directly degrade deltamethrin, which significantly reduces the toxicity of deltamethrin. These results expand people's understanding of the functions of proteases and point to potential applications of trypsin as an attractive agent to control residual pesticides in the environment and on agricultural products. PMID:24594869

  19. Trypsin-catalyzed deltamethrin degradation.

    PubMed

    Xiong, Chunrong; Fang, Fujin; Chen, Lin; Yang, Qinggui; He, Ji; Zhou, Dan; Shen, Bo; Ma, Lei; Sun, Yan; Zhang, Donghui; Zhu, Changliang

    2014-01-01

    To explore if trypsin could catalyze the degradation of non-protein molecule deltamethrin, we compared in vitro hydrolytic reactions of deltamethrin in the presence and absence of trypsin with ultraviolet-visible (UV/Vis) spectrophotometry and gas chromatography-mass spectrometry (GC/MS). In addition, acute oral toxicity of the degradation products was determined in Wistar rats. The results show that the absorption peak of deltamethrin is around 264 nm, while the absorption peaks of deltamethrin degradation products are around 250 nm and 296 nm. In our GC setting, the retention time of undegraded deltamethrin was 37.968 min, while those of deltamethrin degradation products were 15.289 min and 18.730 min. The LD50 of deltamethrin in Wistar rats is 55 mg/kg, while that of deltamethrin degradation products is 3358 mg/kg in female rats and 1045 mg/kg in male rates (61-fold and 19-fold reductions in toxicity), suggesting that trypsin could directly degrade deltamethrin, which significantly reduces the toxicity of deltamethrin. These results expand people's understanding of the functions of proteases and point to potential applications of trypsin as an attractive agent to control residual pesticides in the environment and on agricultural products.

  20. High prevalence of antibodies to calreticulin of the IgA class in primary biliary cirrhosis: a possible role of gut-derived bacterial antigens in its aetiology?

    PubMed

    Kreisel, W; Siegel, A; Bahler, A; Spamer, C; Schiltz, E; Kist, M; Seilnacht, G; Klein, R; Berg, P A; Heilmann, C

    1999-06-01

    In a preliminary study we showed that antibodies to the endoplasmic reticulum protein calreticulin (CR) occur in primary biliary cirrhosis (PBC) and autoimmune hepatitis type 1 (AIH). Since anti-CR antibodies have also been found in patients with infectious diseases, we investigated their prevalence and immunoglobulin classes in patients with various hepatic and intestinal diseases, hoping to get some information on a possible relationship between an infectious trigger and the induction of a certain class of anti-CR antibodies. Sera were tested for anti-CR antibodies of the IgA, IgG, and IgM class by Western blotting, using CR isolated from human liver: in autoimmune liver diseases (primary biliary cirrhosis (PBC) (n = 86) and autoimmune hepatitis (AIH) type 1 (n = 57)), alcoholic liver cirrhosis (ALC) (n = 32), viral liver infections (acute hepatitis A (n = 8), acute hepatitis B (n = 20), and chronic hepatitis C (n = 28)), and intestinal diseases (Crohn disease (CD) (n = 30), acute yersiniosis (n = 26)). Sera from 100 healthy individuals served as negative controls. The most prominent finding was the high prevalence of anti-CR antibodies of the IgA class and the similarity in the anti-CR antibody class pattern in PBC (IgA, 62%; IgG, 43%; IgM, 55%) and yersiniosis (IgA, 62%; IgG, 39%; IgM, 42%). Class IgA anti-CR antibodies also occurred frequently in ALC (IgA, 44%; IgG, 41%; IgM, 19%). In contrast, in AIH anti-CR antibodies were predominantly of class IgG (IgA, 28%; IgG, 60%; IgM, 33%). In hepatitis A anti-CR antibodies were absent. In the other diseases they had a low prevalence and were mostly of class IgG (acute hepatitis B: IgA, 0%; IgG, 15%; IgM, 0%; chronic hepatitis C: IgA, 7%; IgG, 21%; IgM, 0%; CD: IgA, 13%; IgG, 20%; IgM, 13%). Of the healthy individuals 7% had anti-CR antibodies exclusively of class IgG. The high prevalence of anti-CR antibodies of class IgA in patients with PBC and yersiniosis as well as in alcoholic liver disease reflects a reactivity

  1. Trypanosoma cruzi Evades the Complement System as an Efficient Strategy to Survive in the Mammalian Host: The Specific Roles of Host/Parasite Molecules and Trypanosoma cruzi Calreticulin

    PubMed Central

    Ramírez-Toloza, Galia; Ferreira, Arturo

    2017-01-01

    American Trypanosomiasis is an important neglected reemerging tropical parasitism, infecting about 8 million people worldwide. Its agent, Trypanosoma cruzi, exhibits multiple mechanisms to evade the host immune response and infect host cells. An important immune evasion strategy of T. cruzi infective stages is its capacity to inhibit the complement system activation on the parasite surface, avoiding opsonizing, immune stimulating and lytic effects. Epimastigotes, the non-infective form of the parasite, present in triatomine arthropod vectors, are highly susceptible to complement-mediated lysis while trypomastigotes, the infective form, present in host bloodstream, are resistant. Thus T. cruzi susceptibility to complement varies depending on the parasite stage (amastigote, trypomastigotes or epimastigote) and on the T. cruzi strain. To avoid complement-mediated lysis, T. cruzi trypomastigotes express on the parasite surface a variety of complement regulatory proteins, such as glycoprotein 58/68 (gp58/68), T. cruzi complement regulatory protein (TcCRP), trypomastigote decay-accelerating factor (T-DAF), C2 receptor inhibitor trispanning (CRIT) and T. cruzi calreticulin (TcCRT). Alternatively, or concomitantly, the parasite captures components with complement regulatory activity from the host bloodstream, such as factor H (FH) and plasma membrane-derived vesicles (PMVs). All these proteins inhibit different steps of the classical (CP), alternative (AP) or lectin pathways (LP). Thus, TcCRP inhibits the CP C3 convertase assembling, gp58/68 inhibits the AP C3 convertase, T-DAF interferes with the CP and AP convertases assembling, TcCRT inhibits the CP and LP, CRIT confers ability to resist the CP and LP, FH is used by trypomastigotes to inhibit the AP convertases and PMVs inhibit the CP and LP C3 convertases. Many of these proteins have similar molecular inhibitory mechanisms. Our laboratory has contributed to elucidate the role of TcCRT in the host-parasite interplay

  2. Trypanosoma cruzi Evades the Complement System as an Efficient Strategy to Survive in the Mammalian Host: The Specific Roles of Host/Parasite Molecules and Trypanosoma cruzi Calreticulin.

    PubMed

    Ramírez-Toloza, Galia; Ferreira, Arturo

    2017-01-01

    American Trypanosomiasis is an important neglected reemerging tropical parasitism, infecting about 8 million people worldwide. Its agent, Trypanosoma cruzi, exhibits multiple mechanisms to evade the host immune response and infect host cells. An important immune evasion strategy of T. cruzi infective stages is its capacity to inhibit the complement system activation on the parasite surface, avoiding opsonizing, immune stimulating and lytic effects. Epimastigotes, the non-infective form of the parasite, present in triatomine arthropod vectors, are highly susceptible to complement-mediated lysis while trypomastigotes, the infective form, present in host bloodstream, are resistant. Thus T. cruzi susceptibility to complement varies depending on the parasite stage (amastigote, trypomastigotes or epimastigote) and on the T. cruzi strain. To avoid complement-mediated lysis, T. cruzi trypomastigotes express on the parasite surface a variety of complement regulatory proteins, such as glycoprotein 58/68 (gp58/68), T. cruzi complement regulatory protein (TcCRP), trypomastigote decay-accelerating factor (T-DAF), C2 receptor inhibitor trispanning (CRIT) and T. cruzi calreticulin (TcCRT). Alternatively, or concomitantly, the parasite captures components with complement regulatory activity from the host bloodstream, such as factor H (FH) and plasma membrane-derived vesicles (PMVs). All these proteins inhibit different steps of the classical (CP), alternative (AP) or lectin pathways (LP). Thus, TcCRP inhibits the CP C3 convertase assembling, gp58/68 inhibits the AP C3 convertase, T-DAF interferes with the CP and AP convertases assembling, TcCRT inhibits the CP and LP, CRIT confers ability to resist the CP and LP, FH is used by trypomastigotes to inhibit the AP convertases and PMVs inhibit the CP and LP C3 convertases. Many of these proteins have similar molecular inhibitory mechanisms. Our laboratory has contributed to elucidate the role of TcCRT in the host-parasite interplay

  3. BEND3 is involved in the human-specific repression of calreticulin: Implication for the evolution of higher brain functions in human.

    PubMed

    Aghajanirefah, A; Nguyen, L N; Ohadi, M

    2016-01-15

    Recent emerging evidence indicates that changes in gene expression levels are linked to human evolution. We have previously reported a human-specific nucleotide in the promoter sequence of the calreticulin (CALR) gene at position -220C, which is the site of action of valproic acid. Reversion of this nucleotide to the ancestral A-allele has been detected in patients with degrees of deficit in higher brain cognitive functions. This mutation has since been reported in the 1000 genomes database at an approximate frequency of <0.0004 in humans (rs138452745). In the study reported here, we present update on the status of rs138452745 across evolution, based on the Ensembl and NCBI databases. The DNA pulldown assay was also used to identify the proteins binding to the C- and A-alleles, using two cell lines, SK-N-BE and HeLa. Consistent with our previous findings, the C-allele is human-specific, and the A-allele is the rule across all other species (N=38). This nucleotide resides in a block of 12-nucleotides that is strictly conserved across evolution. The DNA pulldown experiments revealed that in both SK-N-BE and HeLa cells, the transcription repressor BEN domain containing 3 (BEND3) binds to the human-specific C-allele, whereas the nuclear factor I (NFI) family members, NF1A, B, C, and X, specifically bind to the ancestral A-allele. This binding pattern is consistent with a previously reported decreased promoter activity of the C-allele vs. the A-allele. We propose that there is a link between binding of BEND3 to the CALR rs138452745 C-allele and removal of NFI binding site from this nucleotide, and the evolution of human-specific higher brain functions. To our knowledge, CALR rs138452745 is the first instance of enormous nucleotide conservation across evolution, except in the human species. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Advances in lipase-catalyzed esterification reactions.

    PubMed

    Stergiou, Panagiota-Yiolanda; Foukis, Athanasios; Filippou, Michalis; Koukouritaki, Maria; Parapouli, Maria; Theodorou, Leonidas G; Hatziloukas, Efstathios; Afendra, Amalia; Pandey, Ashok; Papamichael, Emmanuel M

    2013-12-01

    Lipase-catalyzed esterification reactions are among the most significant chemical and biochemical processes of industrial relevance. Lipases catalyze hydrolysis as well as esterification reactions. Enzyme-catalyzed esterification has acquired increasing attention in many applications, due to the significance of the derived products. More specifically, the lipase-catalyzed esterification reactions attracted research interest during the past decade, due to an increased use of organic esters in biotechnology and the chemical industry. Lipases, as hydrolyzing agents are active in environments, which contain a minimum of two distinct phases, where all reactants are partitioned between these phases, although their distribution is not fixed and changes as the reaction proceeds. The kinetics of the lipase-catalyzed reactions is governed by a number of factors. This article presents a thorough and descriptive evaluation of the applied trends and perspectives concerning the enzymatic esterification, mainly for biofuel production; an emphasis is given on essential factors, which affect the lipase-catalyzed esterification reaction. Moreover, the art of using bacterial and/or fungal strains for whole cell biocatalysis purposes, as well as carrying out catalysis by various forms of purified lipases from bacterial and fungal sources is also reviewed.

  5. Oligonucleotide formation catalyzed by mononucleotide matrices

    NASA Technical Reports Server (NTRS)

    Lohrmann, R.

    1982-01-01

    Pb(2+)-containing precipitates of mononucleotides form matrices which catalyze the self-condensation of nucleotide 5-prime-phosphorimidazolides and their condensation with nucleosides. The reactions exhibit base-pairing specificity between matrix nucleotide and substrate, and usually follow the Watson-Crick pairing rules. Although purine polynucleotides do not facilitate the oligomerization of pyrimidine nucleotide monomers in solution, it is interesting that purine-containing matrices do catalyze such a reaction. The significance of the results in the context of the prebiotic evolution of polynucleotides is discussed.

  6. Enantioselective, iridium-catalyzed monoallylation of ammonia.

    PubMed

    Pouy, Mark J; Stanley, Levi M; Hartwig, John F

    2009-08-19

    Highly enantioselective, iridium-catalyzed monoallylations of ammonia are reported. These reactions occur with electron-neutral, -rich, and -poor cinnamyl carbonates, alkyl and trityloxy-substituted allylic carbonates, and dienyl carbonates in moderate to good yields and excellent enantioselectivities. This process is enabled by the use of an iridium catalyst that does not require a Lewis acid for activation and that is stable toward a large excess of ammonia. This selective formation of primary allylic amines allows for one-pot syntheses of heterodiallylamines and allylic amides that are not otherwise accessible via iridium-catalyzed allylic amination without the use of blocking groups and protective group manipulations.

  7. Oligonucleotide formation catalyzed by mononucleotide matrices

    NASA Technical Reports Server (NTRS)

    Lohrmann, R.

    1982-01-01

    Pb(2+)-containing precipitates of mononucleotides form matrices which catalyze the self-condensation of nucleotide 5-prime-phosphorimidazolides and their condensation with nucleosides. The reactions exhibit base-pairing specificity between matrix nucleotide and substrate, and usually follow the Watson-Crick pairing rules. Although purine polynucleotides do not facilitate the oligomerization of pyrimidine nucleotide monomers in solution, it is interesting that purine-containing matrices do catalyze such a reaction. The significance of the results in the context of the prebiotic evolution of polynucleotides is discussed.

  8. Iron catalyzed asymmetric oxyamination of olefins.

    PubMed

    Williamson, Kevin S; Yoon, Tehshik P

    2012-08-01

    The regioselective and enantioselective oxyamination of alkenes with N-sulfonyl oxaziridines is catalyzed by a novel iron(II) bis(oxazoline) complex. This process affords oxazolidine products that can be easily manipulated to yield highly enantioenriched free amino alcohols. The regioselectivity of this process is complementary to that obtained from the analogous copper(II)-catalyzed reaction. Thus, both regioisomers of enantioenriched 1,2-aminoalcohols can be obtained using oxaziridine-mediated oxyamination reactions, and the overall sense of regiochemistry can be controlled using the appropriate choice of inexpensive first-row transition metal catalyst.

  9. Attractor Explosions and Catalyzed Vacuum Decay

    SciTech Connect

    Green, Daniel; Silverstein, Eva; Starr, David

    2006-05-05

    We present a mechanism for catalyzed vacuum bubble production obtained by combining moduli stabilization with a generalized attractor phenomenon in which moduli are sourced by compact objects. This leads straightforwardly to a class of examples in which the Hawking decay process for black holes unveils a bubble of a different vacuum from the ambient one, generalizing the new endpoint for Hawking evaporation discovered recently by Horowitz. Catalyzed vacuum bubble production can occur for both charged and uncharged bodies, including Schwarzschild black holes for which massive particles produced in the Hawking process can trigger vacuum decay. We briefly discuss applications of this process to the population and stability of metastable vacua.

  10. Enantioselective, Iridium-Catalyzed Monoallylation of Ammonia

    PubMed Central

    Pouy, Mark J.; Stanley, Levi M.; Hartwig, John F.

    2009-01-01

    Highly enantioselective, iridium-catalyzed monoallylations of ammonia are reported. These reactions occur with electron-neutral, -rich, and -poor cinnamyl carbonates, alkyl and trityloxy-substituted allylic carbonates, and dienyl carbonates in moderate to good yields and excellent enantioselectivities. This process is enabled by the use of an iridium catalyst that does not require a Lewis acid for activation and that is stable toward a large excess of ammonia. This selective formation of primary allylic amines allows for one-pot syntheses of heterodiallylamines and allylic amides that are not otherwise accessible via iridium-catalyzed allylic amination without the use of blocking groups and protective group manipulations. PMID:19722644

  11. Palladium catalyzed hydrogenation of bio-oils and organic compounds

    DOEpatents

    Elliott, Douglas C [Kennewick, WA; Hu, Jianli [Richland, WA; Hart,; Todd, R [Kennewick, WA; Neuenschwander, Gary G [Burbank, WA

    2011-06-07

    The invention provides palladium-catalyzed hydrogenations of bio-oils and certain organic compounds. Experimental results have shown unexpected and superior results for palladium-catalyzed hydrogenations of organic compounds typically found in bio-oils.

  12. Palladium catalyzed hydrogenation of bio-oils and organic compounds

    DOEpatents

    Elliott, Douglas C.; Hu, Jianli; Hart, Todd R.; Neuenschwander, Gary G.

    2008-09-16

    The invention provides palladium-catalyzed hydrogenations of bio-oils and certain organic compounds. Experimental results have shown unexpected and superior results for palladium-catalyzed hydrogenations of organic compounds typically found in bio-oils.

  13. Zeolite 5A Catalyzed Etherification of Diphenylmethanol

    ERIC Educational Resources Information Center

    Cooke, Jason; Henderson, Eric J.; Lightbody, Owen C.

    2009-01-01

    An experiment for the synthetic undergraduate laboratory is described in which zeolite 5A catalyzes the room temperature dehydration of diphenylmethanol, (C[subscript 6]H[subscript 5])[subscript 2]CHOH, producing 1,1,1',1'-tetraphenyldimethyl ether, (C[subscript 6]H[subscript 5])[subscript 2]CHOCH(C[subscript 6]H[subscript 5])[subscript 2]. The…

  14. Organic acids tunably catalyze carbonic acid decomposition.

    PubMed

    Kumar, Manoj; Busch, Daryle H; Subramaniam, Bala; Thompson, Ward H

    2014-07-10

    Density functional theory calculations predict that the gas-phase decomposition of carbonic acid, a high-energy, 1,3-hydrogen atom transfer reaction, can be catalyzed by a monocarboxylic acid or a dicarboxylic acid, including carbonic acid itself. Carboxylic acids are found to be more effective catalysts than water. Among the carboxylic acids, the monocarboxylic acids outperform the dicarboxylic ones wherein the presence of an intramolecular hydrogen bond hampers the hydrogen transfer. Further, the calculations reveal a direct correlation between the catalytic activity of a monocarboxylic acid and its pKa, in contrast to prior assumptions about carboxylic-acid-catalyzed hydrogen-transfer reactions. The catalytic efficacy of a dicarboxylic acid, on the other hand, is significantly affected by the strength of an intramolecular hydrogen bond. Transition-state theory estimates indicate that effective rate constants for the acid-catalyzed decomposition are four orders-of-magnitude larger than those for the water-catalyzed reaction. These results offer new insights into the determinants of general acid catalysis with potentially broad implications.

  15. Catalyzing curriculum evolution in graduate science education.

    PubMed

    Gutlerner, Johanna L; Van Vactor, David

    2013-05-09

    Strategies in life science graduate education must evolve in order to train a modern workforce capable of integrative solutions to challenging problems. Our institution has catalyzed such evolution through building a postdoctoral Curriculum Fellows Program that provides a collaborative and scholarly education laboratory for innovation in graduate training.

  16. Zeolite 5A Catalyzed Etherification of Diphenylmethanol

    ERIC Educational Resources Information Center

    Cooke, Jason; Henderson, Eric J.; Lightbody, Owen C.

    2009-01-01

    An experiment for the synthetic undergraduate laboratory is described in which zeolite 5A catalyzes the room temperature dehydration of diphenylmethanol, (C[subscript 6]H[subscript 5])[subscript 2]CHOH, producing 1,1,1',1'-tetraphenyldimethyl ether, (C[subscript 6]H[subscript 5])[subscript 2]CHOCH(C[subscript 6]H[subscript 5])[subscript 2]. The…

  17. Microorganisms detected by enzyme-catalyzed reaction

    NASA Technical Reports Server (NTRS)

    Vango, S. P.; Weetall, H. H.; Weliky, N.

    1966-01-01

    Enzymes detect the presence of microorganisms in soils. The enzyme lysozymi is used to release the enzyme catalase from the microorganisms in a soil sample. The catalase catalyzes the decomposition of added hydrogen peroxide to produce oxygen which is detected manometrically. The partial pressure of the oxygen serves as an index of the samples bacteria content.

  18. Palladium-catalyzed substitution of allylic fluorides.

    PubMed

    Hazari, Amaruka; Gouverneur, Véronique; Brown, John M

    2009-01-01

    As unusual substrates for the Tsuji-Trost allylation reaction, allylic fluorides are responsive to palladium-catalyzed substitution. Their activity towards this reaction fits in the series OCO(2)Me>OBz>F>OAc. The classic stereoretention mechanism that involves sequential inversions does not operate in this case. Several distinct cases are considered.

  19. Dual chemistry catalyzed by human acireductone dioxygenase.

    PubMed

    Deshpande, Aditi R; Pochapsky, Thomas C; Petsko, Gregory A; Ringe, Dagmar

    2017-03-01

    Acireductone dioxygenase (ARD) from the methionine salvage pathway of Klebsiella oxytoca is the only known naturally occurring metalloenzyme that catalyzes different reactions in vivo based solely on the identity of the divalent transition metal ion (Fe2+ or Ni2+) bound in the active site. The iron-containing isozyme catalyzes the cleavage of substrate 1,2-dihydroxy-3-keto-5-(thiomethyl)pent-1-ene (acireductone) by O2 to formate and the ketoacid precursor of methionine, whereas the nickel-containing isozyme uses the same substrates to catalyze an off-pathway shunt to form methylthiopropionate, carbon monoxide and formate. This dual chemistry was recently demonstrated in vitro by ARD from Mus musculus (MmARD), providing the first example of a mammalian ARD exhibiting metal-dependent catalysis. We now show that human ARD (HsARD) is also capable of metal-dependent dual chemistry. Recombinant HsARD was expressed and purified to obtain a homogeneous enzyme with a single transition metal ion bound. As with MmARD, the Fe2+-bound HsARD shows the highest activity and catalyzes on-pathway chemistry, whereas Ni2+, Co2+ or Mn2+ forms catalyze off-pathway chemistry. The thermal stability of the HsARD isozymes is a function of the metal ion identity, with Ni2+-bound HsARD being the most stable followed by Co2+ and Fe2+, and Mn2+-bound HsARD being the least stable. As with the bacterial ARD, solution NMR data suggest that HsARD isozymes can have significant structural differences depending upon the metal ion bound. © The Author 2017. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  20. Analytical rheology of metallocene-catalyzed polyethylenes

    NASA Astrophysics Data System (ADS)

    Shanbhag, Sachin; Takeh, Arsia

    2011-03-01

    A computational algorithm that seeks to invert the linear viscoelastic spectrum of single-site metallocene-catalyzed polyethylenes is presented. The algorithm uses a general linear rheological model of branched polymers as its underlying engine, and is based on a Bayesian formulation that transforms the inverse problem into a sampling problem. Given experimental rheological data on unknown single-site metallocene- catalyzed polyethylenes, it is able to quantitatively describe the range of values of weight-averaged molecular molecular weight, MW , and average branching density, bm , consistent with the data. The algorithm uses a Markov-chain Monte Carlo method to simulate the sampling problem. If, and when information about the molecular weight is available through supplementary experiments, such as chromatography or light scattering, it can easily be incorporated into the algorithm, as demonstrated. Financial support from NSF DMR 0953002.

  1. Cold fusion catalyzed by muons and electrons

    SciTech Connect

    Kulsrud, R.M.

    1990-10-01

    Two alternative methods have been suggested to produce fusion power at low temperature. The first, muon catalyzed fusion or MCF, uses muons to spontaneously catalyze fusion through the muon mesomolecule formation. Unfortunately, this method fails to generate enough fusion energy to supply the muons, by a factor of about ten. The physics of MCF is discussed, and a possible approach to increasing the number of MCF fusions generated by each muon is mentioned. The second method, which has become known as Cold Fusion,'' involves catalysis by electrons in electrolytic cells. The physics of this process, if it exists, is more mysterious than MCF. However, it now appears to be an artifact, the claims for its reality resting largely on experimental errors occurring in rather delicate experiments. However, a very low level of such fusion claimed by Jones may be real. Experiments in cold fusion will also be discussed.

  2. Horseradish-Peroxidase-Catalyzed Tyrosine Click Reaction.

    PubMed

    Sato, Shinichi; Nakamura, Kosuke; Nakamura, Hiroyuki

    2017-03-02

    The efficiency of protein chemical modification on tyrosine residues with N-methylluminol derivatives was drastically improved by using horseradish peroxidase (HRP). In the previous method, based on the use of hemin and H2 O2 , oxidative side reactions such as cysteine oxidation were problematic for functionalization of proteins selectively on tyrosine residues. Oxidative activation of N-methylluminol derivatives with a minimum amount of H2 O2 prevented the occurrence of oxidative side reactions under HRP-catalyzed conditions. As probes for HRP-catalyzed protein modification, N-methylluminol derivatives showed much higher efficiency than tyramide without inducing oligomerization of probe molecules. Tyrosine modification also proceeded in the presence of β-nicotinamide adenine dinucleotide (NADH, H2 O2 -free conditions).

  3. Stop-catalyzed baryogenesis beyond the MSSM

    NASA Astrophysics Data System (ADS)

    Katz, Andrey; Perelstein, Maxim; Ramsey-Musolf, Michael J.; Winslow, Peter

    2015-11-01

    Nonminimal supersymmetric models that predict a tree-level Higgs mass above the minimal supersymmetric standard model (MSSM) bound are well motivated by naturalness considerations. Indirect constraints on the stop sector parameters of such models are significantly relaxed compared to the MSSM; in particular, both stops can have weak-scale masses. We revisit the stop-catalyzed electroweak baryogenesis (EWB) scenario in this context. We find that the LHC measurements of the Higgs boson production and decay rates already rule out the possibility of stop-catalyzed EWB. We also introduce a gauge-invariant analysis framework that may generalize to other scenarios in which interactions outside the gauge sector drive the electroweak phase transition.

  4. Rhodium-catalyzed restructuring of carbon frameworks.

    PubMed

    Murakami, Masahiro

    2010-10-01

    Metal-catalyzed reactions involving an elementary step which cleaves a carbon-carbon bond provide unique organic transformations. Restructuring reactions recently developed in our laboratory, through which the carbon framework of a starting substance is restructured into a totally different carbon framework, are discussed, with the possibility of applying such methods to the synthesis of natural products. © 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

  5. Nickel-Catalyzed Synthesis of Quinazolinediones.

    PubMed

    Beutner, Gregory L; Hsiao, Yi; Razler, Thomas; Simmons, Eric M; Wertjes, William

    2017-03-03

    A nickel(0)-catalyzed method for the synthesis of quinazolinediones from isatoic anhydrides and isocyanates is described. High-throughput ligand screening revealed that XANTPHOS was the optimal ligand for this transformation. Subsequent optimization studies, supported by kinetic analysis, significantly expanded the reaction scope. The reaction exhibits a case of substrate inhibition kinetics with respect to the isocyanate. Preliminary results on an asymmetric synthesis of atropisomeric quinazolinediones are reported.

  6. Antiproton catalyzed microfission/fusion propulsion

    NASA Technical Reports Server (NTRS)

    Chiang, Pi-Ren; Lewis, Raymond A.; Smith, Gerald A.; Newton, Richard; Dailey, James; Werthman, W. Lance; Chakrabarti, Suman

    1994-01-01

    Inertial confinement fusion (ICF) utilizing an antiproton catalyzed hybrid fission/fusion target is discussed as a potential energy source for interplanetary propulsion. A proof-of-principle experiment underway at Phillips Laboratory, Kirtland AFB and antiproton trapping experiments at CERN, Geneva, Switzerland, are presented. The ICAN propulsion concept is described and results of performance analyses are reviewed. Future work to further define the ICAN concept is outlined.

  7. Cu2+-catalyzed oxidative degradation of thyroglobulin.

    PubMed

    Lee, H J; Sok, D E

    2000-10-01

    Thyroglobulin (Tg) was subjected to metal-catalyzed oxidation, and the oxidative degradation was analyzed by SDS-polyacrylamide gel electrophoresis under reducing conditions. In contrast to no effect of hydrogen peroxide (H2O2) alone on the Tg degradation, the inclusion of Cu2+ (30 microM), in combination with 2 mM H2O2, caused a remarkable degradation of Tg, time- and concentration-dependent. The action of Cu2+ was not mimicked by Fe2+, suggesting that Tg may interact selectively with Cu2+. A similar degradation of Tg was also observed with Cu2+/ascorbate system, and the concentration of Cu2+ (5-10 microM), in combination with ascorbate, required for the effective degradation was smaller than that of Cu2+ (10-30 microM) in combination with H2O2. In support of involvement of H2O2 in the Cu2+/ascorbate action, catalase expressed a complete protection. However, hydroxyl radical scavengers such as dimethylsulfoxide or mannitol failed to prevent the oxidation of Tg whereas phenolic compounds, which can interact with Cu2+, diminished the oxidative degradation, presumably consistent with the mechanism for Cu2+-catalyzed oxidation of protein. Moreover, the amount of carbonyl groups in Tg was increased as the concentration (3-100 microM) of Cu2+ was enhanced, while the formation of acid-soluble peptides was not remarkable in the presence of Cu2+ up to 200 microM. In further studies, Tg pretreated with heat or trichloroacetic acid seemed to be somewhat resistant to Cu2+-catalyzed oxidation, implying a possible involvement of protein conformation in the susceptibility to the oxidation. Based on these observations, it is proposed that Tg could be degraded non-enzymatically by Cu2+-catalyzed oxidation.

  8. Metal Catalyzed Oligomerization Reactions of Organosiloxanes.

    DTIC Science & Technology

    1982-10-28

    metallacycle from a mixture of stereo- isomers of the starting disiloxane is observed. The catalytic activity of these complexes for the oligomeriza... catalysts were adsorbed on oxide supports. Although the goal of synthesizing stereoregular silicones has not yet been achieved, the results warrant further...implicated as intermediates in several transi- tion metal-catalyzed reactions, e.g. olefin metathesis . 1 3 Metallacycles are also probable

  9. Iron-catalyzed trifluoromethylation of enamide.

    PubMed

    Rey-Rodriguez, Romain; Retailleau, Pascal; Bonnet, Pascal; Gillaizeau, Isabelle

    2015-02-23

    Herein the first example of the iron(II)-catalyzed trifluoromethylation of enamide using mild and simple reaction conditions is reported. The method is cost-effective and uses the easy-to-handle Togni's reagent as the electrophilic CF3 source. This transformation is totally regioselective at the C3 position of enamides and exhibits broad substrate scope, good functional group tolerance and thus demonstrates its useful application in a late-stage fluorination strategy.

  10. Palladium-Catalyzed Fluorosulfonylvinylation of Organic Iodides.

    PubMed

    Zha, Gao-Feng; Zheng, Qinheng; Leng, Jing; Wu, Peng; Qin, Hua-Li; Sharpless, K Barry

    2017-03-29

    A palladium-catalyzed fluorosulfonylvinylation reaction of organic iodides is described. Catalytic Pd(OAc)2 with a stoichiometric amount of silver(I) trifluoroacetate enables the coupling process between either an (hetero)aryl or alkenyl iodide with ethenesulfonyl fluoride (ESF). The method is demonstrated in the successful syntheses of eighty-eight otherwise difficult to access compounds, in up to 99 % yields, including the unprecedented 2-heteroarylethenesulfonyl fluorides and 1,3-dienylsulfonyl fluorides.

  11. Nickel-catalyzed enantioselective arylation of pyridine†

    PubMed Central

    Lutz, J. Patrick; Chau, Stephen T.

    2016-01-01

    We report an enantioselective Ni-catalyzed cross coupling of arylzinc reagents with pyridiniumions formed in situ from pyridine and a chloroformate. This reaction provides enantioenriched 2-aryl-1,2-dihydropyridine products that can be elaborated to numerous piperidine derivatives with little or no loss in ee. This method is notable for its use of pyridine, a feedstock chemical, to build a versatile, chiral heterocycle in a single synthetic step. PMID:28058106

  12. Transition metal catalyzed transformations of unsaturated molecules

    SciTech Connect

    Not Available

    1989-01-01

    In this proposal, research in three areas of transition metal catalyzed transformations of small molecules is proposed. The first encompasses metal catalyzed processes for the synthesis of several classes of carbon monoxide containing polymers. This section describes plans for metal catalyzed synthesis of (a) new alternating copolymers of carbon monoxide and olefins, (b) block copolymers consisting of segments of the olefin homopolymer and the olefin- carbon monoxide alternating copolymer, and (c) polycarbonates, polyesters and polyamides. The second section involves the examination of the chemistry of metal complexes incorporating oxo and hydrocarbyl ligands as a model for the heterogeneous oxidation of olefins and alkanes by meal oxides. Specific plans are to mimic in solution two proposed key steps in the heterogeneous oxidations. These are (a) the heterolytic cleavage of an alkyl (or allyl) C-H bond that is assisted by an oxo group, and (a) the transfer of an oxo group to the resultant metal bound alkyl (or allyl) ligand. The third section concerned with the development of a hybrid catalyst system involving both homogeneous and heterogeneous components for the oxidative functionalization of alkanes. The basic idea is to employ a transition metal in the elemental state to activate C-H bonds of alkanes and form surface alkyl groups. An additional transition metal species will be present in solution which will serve to oxidize these surface alkyl groups to ultimately yield oxidatively functionalized organic products. 57 refs.

  13. Fe-catalyzed etching of graphene layers

    NASA Astrophysics Data System (ADS)

    Cheng, Guangjun; Calizo, Irene; Hight Walker, Angela; PML, NIST Team

    We investigate the Fe-catalyzed etching of graphene layers in forming gas. Fe thin films are deposited by sputtering onto mechanically exfoliated graphene, few-layer graphene (FLG), and graphite flakes on a Si/SiO2 substrate. When the sample is rapidly annealed in forming gas, particles are produced due to the dewetting of the Fe thin film and those particles catalyze the etching of graphene layers. Monolayer graphene and FLG regions are severely damaged and that the particles catalytically etch channels in graphite. No etching is observed on graphite for the Fe thin film annealed in nitrogen. The critical role of hydrogen indicates that this graphite etching process is catalyzed by Fe particles through the carbon hydrogenation reaction. By comparing with the etched monolayer and FLG observed for the Fe film annealed in nitrogen, our Raman spectroscopy measurements identify that, in forming gas, the catalytic etching of monolayer and FLG is through carbon hydrogenation. During this process, Fe particles are catalytically active in the dissociation of hydrogen into hydrogen atoms and in the production of hydrogenated amorphous carbon through hydrogen spillover.

  14. Imidazole catalyzes chlorination by unreactive primary chloramines.

    PubMed

    Roemeling, Margo D; Williams, Jared; Beckman, Joseph S; Hurst, James K

    2015-05-01

    Hypochlorous acid and simple chloramines (RNHCl) are stable biologically derived chlorinating agents. In general, the chlorination potential of HOCl is much greater than that of RNHCl, allowing it to oxidize or chlorinate a much wider variety of reaction partners. However, in this study we demonstrate by kinetic analysis that the reactivity of RNHCl can be dramatically promoted by imidazole and histidyl model compounds via intermediary formation of the corresponding imidazole chloramines. Two biologically relevant reactions were investigated--loss of imidazole-catalyzed chlorinating capacity and phenolic ring chlorination using fluorescein and the tyrosine analog, 4-hydroxyphenylacetic acid (HPA). HOCl reacted stoichiometrically with imidazole, N-acetylhistidine (NAH), or imidazoleacetic acid to generate the corresponding imidazole chloramines which subsequently decomposed. Chloramine (NH2Cl) also underwent a markedly accelerated loss in chlorinating capacity when NAH was present, although in this case N-α-acetylhistidine chloramine (NAHCl) did not accumulate, indicating that the catalytic intermediate must be highly reactive. Mixing HOCl with 1-methylimidazole (MeIm) led to very rapid loss in chlorinating capacity via formation of a highly reactive chlorinium ion (MeImCl(+)) intermediate; this behavior suggests that the reactive forms of the analogous imidazole chloramines are their conjugate acids, e.g., the imidazolechlorinium ion (HImCl(+)). HOCl-generated imidazole chloramine (ImCl) reacted rapidly with fluorescein in a specific acid-catalyzed second-order reaction to give 3'-monochloro and 3',5'-dichloro products. Equilibrium constants for the transchlorination reactions HOCl + HIm = H2O + ImCl and NH2Cl + HIm = NH3 + ImCl were estimated from the dependence of the rate constants on [HIm]/[HOCl] and literature data. Acid catalysis again suggests that the actual chlorinating agent is HImCl(+); consistent with this interpretation, MeIm markedly catalyzed

  15. Imidazole catalyzes chlorination by unreactive primary chloramines

    PubMed Central

    Roemeling, Margo D.; Williams, Jared; Beckman, Joseph S.; Hurst, James K.

    2015-01-01

    Hypochlorous acid and simple chloramines (RNHCl) are stable biologically-derived chlorinating agents. In general, the chlorination potential of HOCl is much greater than that of RNHCl, allowing it to oxidize or chlorinate a much wider variety of reaction partners. However, in this study we demonstrate by kinetic analysis that the reactivity of RNHCl can be dramatically promoted by imidazole and histidyl model compounds via intermediary formation of the corresponding imidazole chloramines. Two biologically relevant reactions were investigated—loss of imidazole-catalyzed chlorinating capacity and phenolic ring chlorination using fluorescein and the tyrosine analog, 4-hydroxyphenylacetic acid (HPA). HOCl reacted stoichiometrically with imidazole, N-acetylhistidine (NAH), or imidazoleacetic acid to generate the corresponding imidazole chloramines which subsequently decomposed. Chloramine (NH2Cl) also underwent a markedly accelerated loss in chlorinating capacity when NAH was present, although in this case NAHCl did not accumulate, indicating that the catalytic intermediate must be highly reactive. Mixing HOCl with 1-methylimidazole (MeIm) led to very rapid loss in chlorinating capacity via formation of a highly reactive chlorinium ion (MeImCl+) intermediate; this behavior suggests that the reactive forms of the analogous imidazole chloramines are their conjugate acids, e.g., the imidazolechlorinium ion (HImCl+). HOCl-generated imidazole chloramine (ImCl) reacted rapidly with fluorescein in a specific acid-catalyzed second order reaction to give 3′-monochloro and 3′,5′-dichloro products. Equilibrium constants for the transchlorination reactions: HOCl + HIm = H2O + ImCl and NH2Cl + HIm = NH3 + ImCl were estimated from the dependence of the rate constants upon [HIm]/[HOCl] and literature data. Acid catalysis again suggests that the actual chlorinating agent is HImCl+; consistent with this interpretation, MeIm markedly catalyzed fluorescein chlorination by HOCl

  16. Hydroarylation of arynes catalyzed by silver for biaryl synthesis.

    PubMed

    Lee, Nam-Kyu; Yun, Sang Young; Mamidipalli, Phani; Salzman, Ryan M; Lee, Daesung; Zhou, Tao; Xia, Yuanzhi

    2014-03-19

    A new biaryl synthesis via silver-catalyzed hydroarylation of arynes from acyclic building blocks with unactivated arenes in intra- and intermolecular manners has been developed. The previously observed Diels-Alder reactions of arynes with arene were not observed under the current silver-catalyzed conditions. Deuterium scrambling and DFT calculations suggest a stepwise electrophilic aromatic substitution mechanism through the formation of a Wheland-type intermediate followed by a water-catalyzed proton transfer in the final step of the hydroarylation.

  17. Ligand Intermediates in Metal-Catalyzed Reactions

    SciTech Connect

    Gladysz, John A.

    1999-07-31

    The longest-running goal of this project has been the synthesis, isolation, and physical chemical characterization of homogeneous transition metal complexes containing ligand types believed to be intermediates in the metal-catalyzed conversion of CO/H{sub 2}, CO{sub 2}, CH{sub 4}, and similar raw materials to organic fuels, feedstocks, etc. In the current project period, complexes that contain unusual new types of C{sub x}(carbide) and C{sub x}O{sub y} (carbon oxide) ligands have been emphasized. A new program in homogeneous fluorous phase catalysis has been launched as described in the final report.

  18. Copper-catalyzed asymmetric oxidation of sulfides.

    PubMed

    O'Mahony, Graham E; Ford, Alan; Maguire, Anita R

    2012-04-06

    Copper-catalyzed asymmetric sulfoxidation of aryl benzyl and aryl alkyl sulfides, using aqueous hydrogen peroxide as the oxidant, has been investigated. A relationship between the steric effects of the sulfide substituents and the enantioselectivity of the oxidation has been observed, with up to 93% ee for 2-naphthylmethyl phenyl sulfoxide, in modest yield in this instance (up to 30%). The influence of variation of solvent and ligand structure was examined, and the optimized conditions were then used to oxidize a number of aryl alkyl and aryl benzyl sulfides, producing sulfoxides in excellent yields in most cases (up to 92%), and good enantiopurities in certain cases (up to 84% ee).

  19. Iron-catalyzed aminohydroxylation of olefins.

    PubMed

    Williamson, Kevin S; Yoon, Tehshik P

    2010-04-07

    We have discovered that N-sulfonyl oxaziridines react with a broad range of olefins in the presence of iron salts to afford 1,3-oxazolidines. This process provides access to 1,2-aminoalcohols with the opposite sense of regioselectivity produced from the copper-catalyzed oxyamination previously reported by our laboratories. Thus, either regioisomeric form of 1,2-aminoalcohols can easily be obtained from the reaction of oxaziridines with olefins, and the sense of regioselectivity can be controlled by the appropriate choice of inexpensive, nontoxic, first-row transition-metal catalyst.

  20. Aluminum Hydride Catalyzed Hydroboration of Alkynes.

    PubMed

    Bismuto, Alessandro; Thomas, Stephen P; Cowley, Michael J

    2016-12-05

    An aluminum-catalyzed hydroboration of alkynes using either the commercially available aluminum hydride DIBAL-H or bench-stable Et3 Al⋅DABCO as the catalyst and H-Bpin as both the boron reagent and stoichiometric hydride source has been developed. Mechanistic studies revealed a unique mode of reactivity in which the reaction is proposed to proceed through hydroalumination and σ-bond metathesis between the resultant alkenyl aluminum species and HBpin, which acts to drive turnover of the catalytic cycle. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Silver-catalyzed late-stage fluorination.

    PubMed

    Tang, Pingping; Furuya, Takeru; Ritter, Tobias

    2010-09-01

    Carbon-fluorine bond formation by transition metal catalysis is difficult, and only a few methods for the synthesis of aryl fluorides have been developed. All reported transition-metal-catalyzed fluorination reactions for the synthesis of functionalized arenes are based on palladium. Here we present silver catalysis for carbon-fluorine bond formation. Our report is the first example of the use of the transition metal silver to form carbon-heteroatom bonds by cross-coupling catalysis. The functional group tolerance and substrate scope presented here have not been demonstrated for any other fluorination reaction to date.

  2. [Fragment reaction catalyzed by E. coli ribosomes].

    PubMed

    Kotusov, V V; Kukhanova, M K; Sal'nikova, N E; Nikolaeva, L V; Kraevskiĭ, A A

    1977-01-01

    It has been shown that 50S subunits of E. coli MRE-600 ribosomes catalyze the reaction of N-(formyl)-methionyl ester of adenosine 5'-phosphate acting as peptide donor, with Phe-tRNA or CACCA-Phe serving as a peptide acceptor. The reaction is stimulated by cytidine 5'phosphate and inhibited by lincomycin, puromycin and chloramphenicol. The obtained results show that the structure of the donor site of peptidyltransferase is completely assembled on the 50S subunit and 30S subunit is not required for its formation.

  3. Palladium-Catalyzed Arylation of Fluoroalkylamines

    PubMed Central

    Brusoe, Andrew T.; Hartwig, John F.

    2015-01-01

    We report the synthesis of fluorinated anilines by palladium-catalyzed coupling of fluoroalkylamines with aryl bromides and aryl chlorides. The products of these reactions are valuable because anilines typically require the presence of an electron-withdrawing substituent on nitrogen to suppress aerobic or metabolic oxidation, and the fluoroalkyl groups have steric properties and polarity distinct from those of more common electron-withdrawing amide and sulfonamide units. The fluoroalkylaniline products are unstable under typical conditions for C–N coupling reactions (heat and strong base). However, the reactions conducted with the weaker base KOPh, which has rarely been used in cross-coupling to form C–N bonds, occurred in high yield in the presence of a catalyst derived from commercially available AdBippyPhos and [Pd(allyl)Cl]2. Under these conditions, the reactions occur with low catalyst loadings (<0.50 mol % for most substrates) and tolerate the presence of various functional groups that react with the strong bases that are typically used in Pd-catalyzed C–N cross-coupling reactions of aryl halides. The resting state of the catalyst is the phenoxide complex, (BippyPhosPd(Ar)OPh); due to the electron-withdrawing property of the fluoroalkyl substituent, the turnover-limiting step of the reaction is reductive elimination to form the C–N bond. PMID:26065341

  4. Catalyzed D-D stellarator reactor

    SciTech Connect

    Sheffield, John; Spong, Donald A.

    2016-05-12

    The advantages of using the catalyzed deuterium-deuterium (D-D) approach for a fusion reactor—lower and less energetic neutron flux and no need for a tritium breeding blanket—have been evaluated in previous papers, giving examples of both tokamak and stellarator reactors. This paper presents an update for the stellarator example, taking account of more recent empirical transport scaling results and design studies of lower-aspect-ratio stellarators. We use a modified version of the Generic Magnetic Fusion Reactor model to cost a stellarator-type reactor. Recently, this model has been updated to reflect the improved science and technology base and costs in the magnetic fusion program. Furthermore, it is shown that an interesting catalyzed D-D, stellarator power plant might be possible if the following parameters could be achieved: R/ ≈ 4, required improvement factor to ISS04 scaling, FR = 0.9 to 1.15, <β> ≈ 8.0% to 11.5%, Zeff ≈ 1.45 plus a relativistic temperature correction, fraction of fast ions lost ≈ 0.07, Bm ≈ 14 to 16 T, and R ≈ 18 to 24 m.

  5. Catalyzed D-D stellarator reactor

    DOE PAGES

    Sheffield, John; Spong, Donald A.

    2016-05-12

    The advantages of using the catalyzed deuterium-deuterium (D-D) approach for a fusion reactor—lower and less energetic neutron flux and no need for a tritium breeding blanket—have been evaluated in previous papers, giving examples of both tokamak and stellarator reactors. This paper presents an update for the stellarator example, taking account of more recent empirical transport scaling results and design studies of lower-aspect-ratio stellarators. We use a modified version of the Generic Magnetic Fusion Reactor model to cost a stellarator-type reactor. Recently, this model has been updated to reflect the improved science and technology base and costs in the magnetic fusionmore » program. Furthermore, it is shown that an interesting catalyzed D-D, stellarator power plant might be possible if the following parameters could be achieved: R/ ≈ 4, required improvement factor to ISS04 scaling, FR = 0.9 to 1.15, <β> ≈ 8.0% to 11.5%, Zeff ≈ 1.45 plus a relativistic temperature correction, fraction of fast ions lost ≈ 0.07, Bm ≈ 14 to 16 T, and R ≈ 18 to 24 m.« less

  6. Palladium-Catalyzed Arylation of Fluoroalkylamines.

    PubMed

    Brusoe, Andrew T; Hartwig, John F

    2015-07-08

    We report the synthesis of fluorinated anilines by palladium-catalyzed coupling of fluoroalkylamines with aryl bromides and aryl chlorides. The products of these reactions are valuable because anilines typically require the presence of an electron-withdrawing substituent on nitrogen to suppress aerobic or metabolic oxidation, and the fluoroalkyl groups have steric properties and polarity distinct from those of more common electron-withdrawing amide and sulfonamide units. The fluoroalkylaniline products are unstable under typical conditions for C-N coupling reactions (heat and strong base). However, the reactions conducted with the weaker base KOPh, which has rarely been used in cross-coupling to form C-N bonds, occurred in high yield in the presence of a catalyst derived from commercially available AdBippyPhos and [Pd(allyl)Cl]2. Under these conditions, the reactions occur with low catalyst loadings (<0.50 mol % for most substrates) and tolerate the presence of various functional groups that react with the strong bases that are typically used in Pd-catalyzed C-N cross-coupling reactions of aryl halides. The resting state of the catalyst is the phenoxide complex, (BippyPhosPd(Ar)OPh); due to the electron-withdrawing property of the fluoroalkyl substituent, the turnover-limiting step of the reaction is reductive elimination to form the C-N bond.

  7. Catalyzed D-D stellarator reactor

    SciTech Connect

    Sheffield, John; Spong, Donald A.

    2016-05-12

    The advantages of using the catalyzed deuterium-deuterium (D-D) approach for a fusion reactor—lower and less energetic neutron flux and no need for a tritium breeding blanket—have been evaluated in previous papers, giving examples of both tokamak and stellarator reactors. This paper presents an update for the stellarator example, taking account of more recent empirical transport scaling results and design studies of lower-aspect-ratio stellarators. We use a modified version of the Generic Magnetic Fusion Reactor model to cost a stellarator-type reactor. Recently, this model has been updated to reflect the improved science and technology base and costs in the magnetic fusion program. Furthermore, it is shown that an interesting catalyzed D-D, stellarator power plant might be possible if the following parameters could be achieved: R/ ≈ 4, required improvement factor to ISS04 scaling, FR = 0.9 to 1.15, <β> ≈ 8.0% to 11.5%, Zeff ≈ 1.45 plus a relativistic temperature correction, fraction of fast ions lost ≈ 0.07, Bm ≈ 14 to 16 T, and R ≈ 18 to 24 m.

  8. Antibody-catalyzed anaerobic destruction of methamphetamine

    PubMed Central

    Xu, Yang; Hixon, Mark S.; Yamamoto, Noboru; McAllister, Laura A.; Wentworth, Anita D.; Wentworth, Paul; Janda, Kim D.

    2007-01-01

    Methamphetamine [(+)-2] abuse has emerged as a fast-rising global epidemic, with immunopharmacotherapeutic approaches being sought for its treatment. Herein, we report the generation and characterization of a monoclonal antibody, YX1-40H10, that catalyzes the photooxidation of (+)-2 into the nonpsychoactive compound benzaldehyde (14) under anaerobic conditions in the presence of riboflavin (6). Studies have revealed that the antibody facilitates the conversion of (+)-2 into 14 by binding the triplet photoexcited state of 6 in proximity to (+)-2. The antibody binds riboflavin (Kd = 180 μM), although this was not programmed into hapten design, and the YX1-40H10-catalyzed reaction is inhibited by molecular oxygen via the presumed quenching of the photoexcited triplet state of 6. Given that this reaction is another highlight in the processing of reactive intermediates by antibodies, we speculate that this process may have future significance in vivo with programmed immunoglobulins that use flavins as cofactors to destroy selectable molecular targets under hypoxic or even anoxic conditions. PMID:17360412

  9. Manganese Catalyzed C-H Halogenation.

    PubMed

    Liu, Wei; Groves, John T

    2015-06-16

    The remarkable aliphatic C-H hydroxylations catalyzed by the heme-containing enzyme, cytochrome P450, have attracted sustained attention for more than four decades. The effectiveness of P450 enzymes as highly selective biocatalysts for a wide range of oxygenation reactions of complex substrates has driven chemists to develop synthetic metalloporphyrin model compounds that mimic P450 reactivity. Among various known metalloporphyrins, manganese derivatives have received considerable attention since they have been shown to be versatile and powerful mediators for alkane hydroxylation and olefin epoxidation. Mechanistic studies have shown that the key intermediates of the manganese porphyrin-catalyzed oxygenation reactions include oxo- and dioxomanganese(V) species that transfer an oxygen atom to the substrate through a hydrogen abstraction/oxygen recombination pathway known as the oxygen rebound mechanism. Application of manganese porphyrins has been largely restricted to catalysis of oxygenation reactions until recently, however, due to ultrafast oxygen transfer rates. In this Account, we discuss recently developed carbon-halogen bond formation, including fluorination reactions catalyzed by manganese porphyrins and related salen species. We found that biphasic sodium hypochlorite/manganese porphyrin systems can efficiently and selectively convert even unactivated aliphatic C-H bonds to C-Cl bonds. An understanding of this novel reactivity derived from results obtained for the oxidation of the mechanistically diagnostic substrate and radical clock, norcarane. Significantly, the oxygen rebound rate in Mn-mediated hydroxylation is highly correlated with the nature of the trans-axial ligands bound to the manganese center (L-Mn(V)═O). Based on the ability of fluoride ion to decelerate the oxygen rebound step, we envisaged that a relatively long-lived substrate radical could be trapped by a Mn-F fluorine source, effecting carbon-fluorine bond formation. Indeed, this idea

  10. Manganese Catalyzed C–H Halogenation

    SciTech Connect

    Liu, Wei; Groves, John T.

    2015-06-16

    The remarkable aliphatic C–H hydroxylations catalyzed by the heme-containing enzyme, cytochrome P450, have attracted sustained attention for more than four decades. The effectiveness of P450 enzymes as highly selective biocatalysts for a wide range of oxygenation reactions of complex substrates has driven chemists to develop synthetic metalloporphyrin model compounds that mimic P450 reactivity. Among various known metalloporphyrins, manganese derivatives have received considerable attention since they have been shown to be versatile and powerful mediators for alkane hydroxylation and olefin epoxidation. Mechanistic studies have shown that the key intermediates of the manganese porphyrin-catalyzed oxygenation reactions include oxo- and dioxomanganese(V) species that transfer an oxygen atom to the substrate through a hydrogen abstraction/oxygen recombination pathway known as the oxygen rebound mechanism. Application of manganese porphyrins has been largely restricted to catalysis of oxygenation reactions until recently, however, due to ultrafast oxygen transfer rates. In this Account, we discuss recently developed carbon–halogen bond formation, including fluorination reactions catalyzed by manganese porphyrins and related salen species. We found that biphasic sodium hypochlorite/manganese porphyrin systems can efficiently and selectively convert even unactivated aliphatic C–H bonds to C–Cl bonds. An understanding of this novel reactivity derived from results obtained for the oxidation of the mechanistically diagnostic substrate and radical clock, norcarane. Significantly, the oxygen rebound rate in Mn-mediated hydroxylation is highly correlated with the nature of the trans-axial ligands bound to the manganese center (L–MnV$=$O). Based on the ability of fluoride ion to decelerate the oxygen rebound step, we envisaged that a relatively long-lived substrate radical could be trapped by a Mn–F fluorine source, effecting carbon–fluorine bond

  11. Acid-Catalyzed Isomerization of Carvone to Carvacrol

    ERIC Educational Resources Information Center

    Kjonaas, Richard A.; Mattingly, Shawn P.

    2005-01-01

    The acid-catalyzed isomerization of carvone to carvacrol, first reported by Ritter and Ginsburg, is especially well suited with a permanent-magnet FT instrument. The acid-catalyzed isomerization of carvone to carvacrol produced a 61% yield after a three hour reflux with 30% aqueous sulfuric acid.

  12. ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT: ENVIROFUELS DIESEL FUEL CATALYZER FUEL ADDITIVE

    EPA Science Inventory

    EPA's Environmental Technology Verification Program has tested EnviroFuels diesel fuel additive, called the Diesel Fuel Catalyzer. EnviroFuels has stated that heavy-duty on and off road diesel engines are the intended market for the catalyzer. Preliminary tests conducted indicate...

  13. Representing Rate Equations for Enzyme-Catalyzed Reactions

    ERIC Educational Resources Information Center

    Ault, Addison

    2011-01-01

    Rate equations for enzyme-catalyzed reactions are derived and presented in a way that makes it easier for the nonspecialist to see how the rate of an enzyme-catalyzed reaction depends upon kinetic constants and concentrations. This is done with distribution equations that show how the rate of the reaction depends upon the relative quantities of…

  14. Representing Rate Equations for Enzyme-Catalyzed Reactions

    ERIC Educational Resources Information Center

    Ault, Addison

    2011-01-01

    Rate equations for enzyme-catalyzed reactions are derived and presented in a way that makes it easier for the nonspecialist to see how the rate of an enzyme-catalyzed reaction depends upon kinetic constants and concentrations. This is done with distribution equations that show how the rate of the reaction depends upon the relative quantities of…

  15. Acid-Catalyzed Isomerization of Carvone to Carvacrol

    ERIC Educational Resources Information Center

    Kjonaas, Richard A.; Mattingly, Shawn P.

    2005-01-01

    The acid-catalyzed isomerization of carvone to carvacrol, first reported by Ritter and Ginsburg, is especially well suited with a permanent-magnet FT instrument. The acid-catalyzed isomerization of carvone to carvacrol produced a 61% yield after a three hour reflux with 30% aqueous sulfuric acid.

  16. ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT: ENVIROFUELS DIESEL FUEL CATALYZER FUEL ADDITIVE

    EPA Science Inventory

    EPA's Environmental Technology Verification Program has tested EnviroFuels diesel fuel additive, called the Diesel Fuel Catalyzer. EnviroFuels has stated that heavy-duty on and off road diesel engines are the intended market for the catalyzer. Preliminary tests conducted indicate...

  17. RNA-Catalyzed RNA Ligation on an External RNA Template

    NASA Technical Reports Server (NTRS)

    McGinness, Kathleen E.; Joyce, Gerald F.

    2002-01-01

    Variants of the hc ligase ribozyme, which catalyzes ligation of the 3' end of an RNA substrate to the 5' end of the ribozyme, were utilized to evolve a ribozyme that catalyzes ligation reactions on an external RNA template. The evolved ribozyme catalyzes the joining of an oligonucleotide 3'-hydroxyl to the 5'-triphosphate of an RNA hairpin molecule. The ribozyme can also utilize various substrate sequences, demonstrating a largely sequence-independent mechanism for substrate recognition. The ribozyme also carries out the ligation of two oligonucleotides that are bound at adjacent positions on a complementary template. Finally, it catalyzes addition of mononucleoside '5-triphosphates onto the '3 end of an oligonucleotide primer in a template-dependent manner. The development of ribozymes that catalyze polymerase-type reactions contributes to the notion that an RNA world could have existed during the early history of life on Earth.

  18. Fabrication of catalyzed ion transport membrane systems

    DOEpatents

    Carolan, Michael Francis; Kibby, Charles Leonard

    2013-06-04

    Process for fabricating a catalyzed ion transport membrane (ITM). In one embodiment, an uncatalyzed ITM is (a) contacted with a non-reducing gaseous stream while heating to a temperature and for a time period sufficient to provide an ITM possessing anion mobility; (b) contacted with a reducing gaseous stream for a time period sufficient to provide an ITM having anion mobility and essentially constant oxygen stoichiometry; (c) cooled while contacting the ITM with the reducing gaseous stream to provide an ITM having essentially constant oxygen stoichiometry and no anion mobility; and (d) treated by applying catalyst to at least one of (1) a porous mixed conducting multicomponent metallic oxide (MCMO) layer contiguous with a first side of a dense layer of MCMO and (2) a second side of the dense MCMO layer. In another embodiment, these steps are carried out in the alternative order of (a), (d), (b), and (c).

  19. Enzyme-catalyzed, gas-phase reactions.

    PubMed

    Barzana, E; Klibanov, A M; Karel, M

    1987-06-01

    Dehydrated preparations of alcohol oxidase adsorbed on DEAE-cellulose vigorously catalyze a gas-phase oxidation of ethanol vapors with molecular oxygen. The gas-phase reaction is strongly dependent on the water activity of the system. The enzymatic activity is severely inhibited by the product hydrogen peroxide. This inhibition can be alleviated, however, by an addition of catalase or peroxidase to the dry preparation. Such dehydrated, bienzymic catalysts afford a complete and selective conversion of the substrate to acetaldehyde. Dry alcohol oxidase is much more thermostable than in aqueous solution. The results of this work suggest that dehydrated enzymes have potential applications in the analysis of gaseous compounds and in the development of novel gas-solid bioreactors.

  20. Dopant-Catalyzed Singlet Exciton Fission.

    PubMed

    Snamina, Mateusz; Petelenz, Piotr

    2017-01-04

    In acene-based molecular crystals, singlet exciton fission occurs through superexchange mediated by two virtual charge-transfer states. Hence, it is sensitive to their energies, which depend on the local environment. The crucial point is the balance between the charge-quadrupole interactions within the pair of molecules directly involved in the process and those with the surrounding crystal matrix, which are governed by local symmetry and may be influenced by breaking this symmetry. This happens, for example, in the vicinity of a vacancy or an impurity and in the latter case is complemented by polarization energy and potentially by dipolar contributions. Our model calculations indicate that the superexchange coupling is sensitive enough to these factors to enable fission to be catalyzed by judiciously designed dopant molecules. In favorable cases, dipolar dopants are expected to increase the fission rate by an order of magnitude.

  1. Rhodium-Catalyzed Alkene Difunctionalization with Nitrenes.

    PubMed

    Ciesielski, Jennifer; Dequirez, Geoffroy; Retailleau, Pascal; Gandon, Vincent; Dauban, Philippe

    2016-06-27

    The Rh(II) -catalyzed oxyamination and diamination of alkenes generate 1,2-amino alcohols and 1,2-diamines, respectively, in good to excellent yields and with complete regiocontrol. In the case of diamination, the intramolecular reaction provides an efficient method for the preparation of pyrrolidines, and the intermolecular reaction produces vicinal amines with orthogonal protecting groups. These alkene difunctionalizations proceed by aziridination followed by nucleophilic ring opening induced by an Rh-bound nitrene generated in situ, details of which were uncovered by both experimental and theoretical studies. In particular, DFT calculations show that the nitrogen atom of the putative [Rh]2 =NR metallanitrene intermediate is electrophilic and support an aziridine activation pathway by N⋅⋅⋅N=[Rh]2 bond formation, in addition to the N⋅⋅⋅[Rh]2 =NR coordination mode. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Palladium-Catalyzed Aminocarbonylation of Allylic Alcohols.

    PubMed

    Li, Haoquan; Neumann, Helfried; Beller, Matthias

    2016-07-11

    A benign and efficient palladium-catalyzed aminocarbonylation reaction of allylic alcohols is presented. The generality of this novel process is demonstrated by the synthesis of β,γ-unsaturated amides including aliphatic, cinnamyl, and terpene derivatives. The choice of ligand is crucial for optimal carbonylation processes: Whereas in most cases the combination of PdCl2 with Xantphos (L6) gave best results, sterically hindered substrates performed better in the presence of simple triphenylphosphine (L10), and primary anilines gave the best results using cataCXium® PCy (L8). The reactivity of the respective catalyst system is significantly enhanced by addition of small amounts of water. Mechanistic studies and control experiments revealed a tandem allylic alcohol amination/C-N bond carbonylation reaction sequence.

  3. Enzyme-catalyzed degradation of carbon nanomaterials

    NASA Astrophysics Data System (ADS)

    Kotchey, Gregg P.

    Carbon nanotubes and graphene, the nanoscale sp 2 allotropes of carbon, have garnered widespread attention as a result of their remarkable electrical, mechanical, and optical properties and the promise of new technologies that harness these properties. Consequently, these carbon nanomaterials (CNMs) have been employed for diverse applications such as electronics, sensors, composite materials, energy conversion devices, and nanomedicine. The manufacture and eventual disposal of these products may result in the release of CNMs into the environment and subsequent exposure to humans, animals, and vegetation. Given the possible pro-inflammatory and toxic effects of CNMs, much attention has been focused on the distribution, toxicity, and persistence of CNMs both in living systems and the environment. This dissertation will guide the reader though recent studies aimed at elucidating fundamental insight into the persistence of CNMs such as carbon nanotubes (CNTs) and graphene derivatives (i.e., graphene oxide and reduced graphene oxide). In particular, in-testtube oxidation/degradation of CNMs catalyzed by peroxidase enzymes will be examined, and the current understanding of the mechanisms underlying these processes will be discussed. Finally, an outlook of the current field including in vitro and in vivo biodegradation experiments, which have benefits in terms of human health and environmental safety, and future directions that could have implications for nanomedical applications such as imaging and drug delivery will be presented. Armed with an understanding of how and why CNMs undergo enzyme-catalyzed oxidation/biodegradation, researchers can tailor the structure of CNMs to either promote or inhibit these processes. For example, in nanomedical applications such as drug delivery, the incorporation of carboxylate functional groups could facilitate biodegradation of the nanomaterial after delivery of the cargo. Also, the incorporation of CNMs with defect sites in consumer

  4. Thermodynamic limitations on microbially catalyzed reaction rates

    NASA Astrophysics Data System (ADS)

    LaRowe, Douglas E.; Dale, Andrew W.; Amend, Jan P.; Van Cappellen, Philippe

    2012-08-01

    Quantification of global biogeochemical cycles requires knowledge of the rates at which microorganisms catalyze chemical reactions. In order for models that describe these processes to capture global patterns of change, the underlying formulations in them must account for biogeochemical transformations over seasonal and millennial time scales in environments characterized by different energy levels. Building on existing models, a new thermodynamic limiting function is introduced. With only one adjustable parameter, this function that can be used to model microbial metabolism throughout the range of conditions in which organisms are known to be active. The formulation is based on a comparison of the amount of energy available from any redox reaction to the energy required to maintain a membrane potential, a proxy for the minimum amount of energy required by an active microorganism. This function does not require species- or metabolism-specific parameters, and can be used to model metabolisms that capture any amount of energy. The utility of this new thermodynamic rate limiting term is illustrated by applying it to three low-energy processes: fermentation, methanogenesis and sulfate reduction. The model predicts that the rate of fermentation will be reduced by half once the Gibbs energy of the catalyzed reaction reaches -12 kJ (mol e-)-1, and then slowing exponentially until the energy yield approaches zero. Similarly, the new model predicts that the low energy yield of methanogenesis, -4 to -0.5 kJ (mol e-)-1, for a partial pressure of H2 between 11 and 0.6 Pa decreases the reaction rate by 95-99%. Finally, the new function's utility is illustrated through its ability to accurately model sulfate concentration data in an anoxic marine sediment.

  5. NEW CORDIERITE DIESEL PARTICULATE FILTERS FOR CATALYZED AND NON-CATALYZED APPLICATIONS

    SciTech Connect

    Merkel, G; Cutler, W; Tao, T Chiffey, A; Phillips, P; Twigg, M; Walker, A

    2003-08-24

    Cordierite diesel particulate filters provide an economical approach to diesel emissions control. However, further reduction in the pressure drop of catalyzed and non-catalyzed cordierite filters is desirable. In order to derive a fundamental understanding of the relationship between clean and sootloaded pressure drop and the pore microstructure of the ceramic, and to optimize the microstructure for filter performance, cordierite filters have been fabricated spanning an extended range in porosity, pore size distribution, and pore connectivity. Analysis of the results has been applied to the development of several new cordierite diesel particulate filters that possess a unique combination of high filtration efficiency, high strength, and very low clean and soot-loaded pressure drop. Furthermore, catalyst systems have been developed that result in a minimal pressure drop increase of the catalyzed filter. Optimization of porosity and cell geometry has enabled fabrication o f filters with either high or low thermal mass appropriate to the regeneration strategy employed for a given engine management system.

  6. Tax posttranslational modifications and interaction with calreticulin in MT-2 cells and human peripheral blood mononuclear cells of human T cell lymphotropic virus type-I-associated myelopathy/tropical spastic paraparesis patients.

    PubMed

    Medina, Fernando; Quintremil, Sebastian; Alberti, Carolina; Barriga, Andres; Cartier, Luis; Puente, Javier; Ramírez, Eugenio; Ferreira, Arturo; Tanaka, Yuetsu; Valenzuela, Maria Antonieta

    2014-04-01

    The human retrovirus human T cell lymphotropic virus type-I (HTLV-1) is the etiologic agent of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Axonal degeneration in HAM/TSP patients occurs without neuron infection, with the secreted viral Tax protein proposed to be involved. We previously found that Tax secreted into the culture medium of MT-2 cells (HTLV-1-infected cell line) produced neurite retraction in neuroblastoma cells differentiated to neuronal type. To assess the relevance of Tax posttranslational modifications on this effect, we addressed the question of whether Tax secreted by MT-2 cells and peripheral blood mononuclear cells (PBMCs) of HTLV-1-infected subjects is modified. The interaction of Tax with calreticulin (CRT) that modulates intracellular Tax localization and secretion has been described. We studied Tax localization and modifications in MT-2 cells and its interaction with CRT. Intracellular Tax in MT-2 cells was assessed by flow cytometry, corresponding mainly to a 71-kDa protein followed by western blot. This protein reported as a chimera with gp21 viral protein-confirmed by mass spectrometry-showed no ubiquitination or SUMOylation. The Tax-CRT interaction was determined by confocal microscopy and coimmunoprecipitation. Extracellular Tax from HAM/TSP PBMCs is ubiquitinated according to western blot, and its interaction with CRT was shown by coimmunoprecipitation. A positive correlation between Tax and CRT secretion was observed in HAM/TSP PBMCs and asymptomatic carriers. For both proteins inhibitors and activators of secretion showed secretion through the endoplasmic reticulum-Golgi complex. Tax, present in PBMC culture medium, produced neurite retraction in differentiated neuroblastoma cells. These results suggest that Tax, whether ubiquitinated or not, is active for neurite retraction.

  7. Tax Posttranslational Modifications and Interaction with Calreticulin in MT-2 Cells and Human Peripheral Blood Mononuclear Cells of Human T Cell Lymphotropic Virus Type-I-Associated Myelopathy/Tropical Spastic Paraparesis Patients

    PubMed Central

    Medina, Fernando; Quintremil, Sebastian; Alberti, Carolina; Barriga, Andres; Cartier, Luis; Puente, Javier; Ramírez, Eugenio; Ferreira, Arturo; Tanaka, Yuetsu

    2014-01-01

    Abstract The human retrovirus human T cell lymphotropic virus type-I (HTLV-1) is the etiologic agent of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Axonal degeneration in HAM/TSP patients occurs without neuron infection, with the secreted viral Tax protein proposed to be involved. We previously found that Tax secreted into the culture medium of MT-2 cells (HTLV-1-infected cell line) produced neurite retraction in neuroblastoma cells differentiated to neuronal type. To assess the relevance of Tax posttranslational modifications on this effect, we addressed the question of whether Tax secreted by MT-2 cells and peripheral blood mononuclear cells (PBMCs) of HTLV-1-infected subjects is modified. The interaction of Tax with calreticulin (CRT) that modulates intracellular Tax localization and secretion has been described. We studied Tax localization and modifications in MT-2 cells and its interaction with CRT. Intracellular Tax in MT-2 cells was assessed by flow cytometry, corresponding mainly to a 71-kDa protein followed by western blot. This protein reported as a chimera with gp21 viral protein—confirmed by mass spectrometry—showed no ubiquitination or SUMOylation. The Tax–CRT interaction was determined by confocal microscopy and coimmunoprecipitation. Extracellular Tax from HAM/TSP PBMCs is ubiquitinated according to western blot, and its interaction with CRT was shown by coimmunoprecipitation. A positive correlation between Tax and CRT secretion was observed in HAM/TSP PBMCs and asymptomatic carriers. For both proteins inhibitors and activators of secretion showed secretion through the endoplasmic reticulum–Golgi complex. Tax, present in PBMC culture medium, produced neurite retraction in differentiated neuroblastoma cells. These results suggest that Tax, whether ubiquitinated or not, is active for neurite retraction. PMID:24321043

  8. SidL, an Aspergillus fumigatus transacetylase involved in biosynthesis of the siderophores ferricrocin and hydroxyferricrocin.

    PubMed

    Blatzer, Michael; Schrettl, Markus; Sarg, Bettina; Lindner, Herbert H; Pfaller, Kristian; Haas, Hubertus

    2011-07-01

    The opportunistic fungal pathogen Aspergillus fumigatus produces four types of siderophores, low-molecular-mass iron chelators: it excretes fusarinine C (FsC) and triacetylfusarinine C (TAFC) for iron uptake and accumulates ferricrocin (FC) for hyphal and hydroxyferricrocin (HFC) for conidial iron distribution and storage. Siderophore biosynthesis has recently been shown to be crucial for fungal virulence. Here we identified a new component of the fungal siderophore biosynthetic machinery: AFUA_1G04450, termed SidL. SidL is conserved only in siderophore-producing ascomycetes and shows similarity to transacylases involved in bacterial siderophore biosynthesis and the N(5)-hydroxyornithine:anhydromevalonyl coenzyme A-N(5)-transacylase SidF, which is essential for TAFC biosynthesis. Inactivation of SidL in A. fumigatus decreased FC biosynthesis during iron starvation and completely blocked FC biosynthesis during iron-replete growth. In agreement with these findings, SidL deficiency blocked conidial accumulation of FC-derived HFC under iron-replete conditions, which delayed germination and decreased the size of conidia and their resistance to oxidative stress. Remarkably, the sidL gene is not clustered with other siderophore-biosynthetic genes, and its expression is not affected by iron availability. Tagging of SidL with enhanced green fluorescent protein suggested a cytosolic localization of the FC-biosynthetic machinery. Taken together, these data suggest that SidL is a constitutively active N(5)-hydroxyornithine-acetylase required for FC biosynthesis, in particular under iron-replete conditions. Moreover, this study revealed the unexpected complexity of siderophore biosynthesis, indicating the existence of an additional, iron-repressed N(5)-hydroxyornithine-acetylase.

  9. Oxygenase-catalyzed ribosome hydroxylation occurs in prokaryotes and humans.

    PubMed

    Ge, Wei; Wolf, Alexander; Feng, Tianshu; Ho, Chia-hua; Sekirnik, Rok; Zayer, Adam; Granatino, Nicolas; Cockman, Matthew E; Loenarz, Christoph; Loik, Nikita D; Hardy, Adam P; Claridge, Timothy D W; Hamed, Refaat B; Chowdhury, Rasheduzzaman; Gong, Lingzhi; Robinson, Carol V; Trudgian, David C; Jiang, Miao; Mackeen, Mukram M; McCullagh, James S; Gordiyenko, Yuliya; Thalhammer, Armin; Yamamoto, Atsushi; Yang, Ming; Liu-Yi, Phebee; Zhang, Zhihong; Schmidt-Zachmann, Marion; Kessler, Benedikt M; Ratcliffe, Peter J; Preston, Gail M; Coleman, Mathew L; Schofield, Christopher J

    2012-12-01

    The finding that oxygenase-catalyzed protein hydroxylation regulates animal transcription raises questions as to whether the translation machinery and prokaryotic proteins are analogously modified. Escherichia coli ycfD is a growth-regulating 2-oxoglutarate oxygenase catalyzing arginyl hydroxylation of the ribosomal protein Rpl16. Human ycfD homologs, Myc-induced nuclear antigen (MINA53) and NO66, are also linked to growth and catalyze histidyl hydroxylation of Rpl27a and Rpl8, respectively. This work reveals new therapeutic possibilities via oxygenase inhibition and by targeting modified over unmodified ribosomes.

  10. Peptide Bond Formation Mechanism Catalyzed by Ribosome.

    PubMed

    Świderek, Katarzyna; Marti, Sergio; Tuñón, Iñaki; Moliner, Vicent; Bertran, Juan

    2015-09-23

    In this paper we present a study of the peptide bond formation reaction catalyzed by ribosome. Different mechanistic proposals have been explored by means of Free Energy Perturbation methods within hybrid QM/MM potentials, where the chemical system has been described by the M06-2X functional and the environment by means of the AMBER force field. According to our results, the most favorable mechanism in the ribosome would proceed through an eight-membered ring transition state, involving a proton shuttle mechanism through the hydroxyl group of the sugar and a water molecule. This transition state is similar to that described for the reaction in solution (J. Am. Chem. Soc. 2013, 135, 8708-8719), but the reaction mechanisms are noticeably different. Our simulations reproduce the experimentally determined catalytic effect of ribosome that can be explained by the different behavior of the two environments. While the solvent reorganizes during the chemical process involving an entropic penalty, the ribosome is preorganized in the formation of the Michaelis complex and does not suffer important changes along the reaction, dampening the charge redistribution of the chemical system.

  11. Mechanisms of bacterially catalyzed reductive dehalogenation

    SciTech Connect

    Picardal, Flynn William

    1992-01-01

    Nine bacteria were tested for the ability to dehalogenate tetrachloromethane (CT), tetrachloroethene (PCE), and 1, 1, 1-trichloroethane (TCA) under anaerobic conditions. Three bacteria were able to reductively dehalogenate CT. Dehalogenation ability was not readily linked to a common metabolism or changes in culture redox potential. None of the bacteria tested were able to dehalogenate PCE or TCA. One of the bacteria capable of dehalogenating CT, Shewanella putrefaciens, was chosen as a model organism to study mechanisms of bacterially catalyzed reductive dehalogenation. The effect of a variety of alternate electron acceptors on CT dehalogenation ability by S. putrefaciens was determined. oxygen and nitrogen oxides were inhibitory but Fe (III), trimethylamine oxide, and fumarate were not. A model of the electron transport chain of S. putrefaciens was developed to explain inhibition patterns. A period of microaerobic growth prior to CT exposure increased the ability of S. putrefaciens to dehalogenate CT. A microaerobic growth period also increased cytochrome concentrations. A relationship between cytochrome content and dehalogenation ability was developed from studies in which cytochrome concentrations in S. putrefaciens were manipulated by changing growth conditions. Stoichiometry studies using 14C-CT suggested that CT was first reduced to form a trichloromethyl radical. Reduction of the radical to produce chloroform and reaction of the radical with cellular biochemicals explained observed product distributions. Carbon dioxide or other fully dehalogenated products were not found.

  12. Peptide Bond Formation Mechanism Catalyzed by Ribosome

    PubMed Central

    Świderek, Katarzyna; Marti, Sergio; Tuñón, Iñaki; Moliner, Vicent; Bertran, Juan

    2015-01-01

    In this paper we present a study of the peptide bond formation reaction catalyzed by ribosome. Different mechanistic proposals have been explored by means of Free Energy Perturbation methods within hybrid QM/MM potentials, where the chemical system has been described by the M06-2X functional and the environment by means of the AMBER force field. According to our results, the most favourable mechanism in the ribosome would proceed through an eight-membered ring transition state, involving a proton shuttle mechanism through the hydroxyl group of the sugar and a water molecule. This transition state is similar to that described for the reaction in solution (J. Am. Chem. Soc. 2013, 135, 8708–8719) but the reaction mechanisms are noticeable different. Our simulations reproduce the experimentally determined catalytic effect of ribosome that can be explained by the different behaviour of the two environments. While the solvent reorganizes during the chemical process involving an entropic penalty, the ribosome is preorganized in the formation of the Michaelis complex and does not suffer important changes along the reaction, dampening the charge redistribution of the chemical system. PMID:26325003

  13. Thioglycoside hydrolysis catalyzed by {beta}-glucosidase

    SciTech Connect

    Shen Hong; Byers, Larry D.

    2007-10-26

    Sweet almond {beta}-glucosidase (EC 3.2.1.21) has been shown to have significant thioglycohydrolase activity. While the K{sub m} values for the S- and O-glycosides are similar, the k{sub cat} values are about 1000-times lower for the S-glycosides. Remarkably, the pH-profile for k{sub cat}/K{sub m} for hydrolysis of p-nitrophenyl thioglucoside (pNPSG) shows the identical dependence on a deprotonated carboxylate (pK{sub a} 4.5) and a protonated group (pK{sub a} 6.7) as does the pH-profile for hydrolysis of the corresponding O-glycoside. Not surprisingly, in spite of the requirement for the presence of this protonated group in catalytically active {beta}-glucosidase, thioglucoside hydrolysis does not involve general acid catalysis. There is no solvent kinetic isotope effect on the enzyme-catalyzed hydrolysis of pNPSG.

  14. Toluene Monooxygenase-Catalyzed Epoxidation of Alkenes

    PubMed Central

    McClay, Kevin; Fox, Brian G.; Steffan, Robert J.

    2000-01-01

    Several toluene monooxygenase-producing organisms were tested for their ability to oxidize linear alkenes and chloroalkenes three to eight carbons long. Each of the wild-type organisms degraded all of the alkenes that were tested. Epoxides were produced during the oxidation of butene, butadiene, and pentene but not hexene or octadiene. A strain of Escherichia coli expressing the cloned toluene-4-monooxygenase (T4MO) of Pseudomonas mendocina KR1 was able to oxidize butene, butadiene, pentene, and hexene but not octadiene, producing epoxides from all of the substrates that were oxidized. A T4MO-deficient variant of P. mendocina KR1 oxidized alkenes that were five to eight carbons long, but no epoxides were detected, suggesting the presence of multiple alkene-degrading enzymes in this organism. The alkene oxidation rates varied widely (ranging from 0.01 to 0.33 μmol of substrate/min/mg of cell protein) and were specific for each organism-substrate pair. The enantiomeric purity of the epoxide products also varied widely, ranging from 54 to >90% of a single epoxide enantiomer. In the absence of more preferred substrates, such as toluene or alkenes, the epoxides underwent further toluene monooxygenase-catalyzed transformations, forming products that were not identified. PMID:10788354

  15. Iodide effects in transition metal catalyzed reactions.

    PubMed

    Maitlis, Peter M; Haynes, Anthony; James, Brian R; Catellani, Marta; Chiusoli, Gian Paolo

    2004-11-07

    The unique properties of I(-) allow it to be involved in several different ways in reactions catalyzed by the late transition metals: in the oxidative addition, the migration, and the coupling/reductive elimination steps, as well as in substrate activation. Most steps are accelerated by I(-)(for example through an increased nucleophilicity of the metal center), but some are retarded, because a coordination site is blocked. The "soft" iodide ligand binds more strongly to soft metals (low oxidation state, electron rich, and polarizable) such as the later and heavier transition metals, than do the other halides, or N- and O-centered ligands. Hence in a catalytic cycle that includes the metal in a formally low oxidation state there will be less tendency for the metal to precipitate (and be removed from the cycle) in the presence of I(-) than most other ligands. Iodide is a good nucleophile and is also easily and reversibly oxidized to I(2). In addition, I(-) can play key roles in purely organic reactions that occur as part of a catalytic cycle. Thus to understand the function of iodide requires careful analysis, since two or sometimes more effects occur in different steps of one single cycle. Each of these topics is illustrated with examples of the influence of iodide from homogeneous catalytic reactions in the literature: methanol carbonylation to acetic acid and related reactions; CO hydrogenation; imine hydrogenation; and C-C and C-N coupling reactions. General features are summarised in the Conclusions.

  16. Base-catalyzed and cholinesterase-catalyzed hydrolysis of acetylcholine and optically active analogs.

    PubMed

    Schowen, K B; Smissman, E E; Stephen, W F

    1975-03-01

    The base- and cholinestrase-catalyzed hydrolyses of the following optically active analogs of acetylcholine were studied: 3 (a)-trimethylammonium-2(a)-acetoxy-trans-decalin iodide, threo- and erythro-alpha, beta-dimethylacetylcholine iodide, alpha-methylacetylcholine, and beta-methylacetylcholine. Evidence that the optimum dihedral +N-C-C-O angle in the transition state for acetylcholinesterase hydrolysis of acetylcholine analogs is positive and anticlinal is given. The data obtained suggest that acetylcholine undergoes a geometrically flexible mode of attachment to the enzyme.

  17. ENVIRONMENTAL ASSESSMENT OF THE BASE CATALYZED DECOMPOSITION (BCD) PROCESS

    EPA Science Inventory

    This report summarizes laboratory-scale, pilot-scale, and field performance data on BCD (Base Catalyzed Decomposition) and technology, collected to date by various governmental, academic, and private organizations.

  18. Diastereoselective Pt catalyzed cycloisomerization of polyenes to polycycles.

    PubMed

    Geier, Michael J; Gagné, Michel R

    2014-02-26

    Application of a tridentate NHC containing pincer ligand to Pt catalyzed cascade cyclization reactions has allowed for the catalytic, diastereoselective cycloisomerization of biogenic alkene terminated substrates to the their polycyclic counterparts.

  19. ENVIRONMENTAL ASSESSMENT OF THE BASE CATALYZED DECOMPOSITION (BCD) PROCESS

    EPA Science Inventory

    This report summarizes laboratory-scale, pilot-scale, and field performance data on BCD (Base Catalyzed Decomposition) and technology, collected to date by various governmental, academic, and private organizations.

  20. Rhodium-Catalyzed Dehydrogenative Borylation of Cyclic Alkenes

    PubMed Central

    Kondoh, Azusa; Jamison, Timothy F.

    2010-01-01

    A rhodium-catalyzed dehydrogenative borylation of cyclic alkenes is described. This reaction provides direct access to cyclic 1-alkenylboronic acid pinacol esters, useful intermediates in organic synthesis. Suzuki-Miyaura cross-coupling applications are also presented. PMID:20107646

  1. Pd-catalyzed arylation of chlorotrifluoroethylene using arylboronic acids.

    PubMed

    Yamamoto, Tetsuya; Yamakawa, Tetsu

    2012-07-06

    The palladium-catalyzed cross-coupling of chlorotrifluoroethylene and arylboronic acids proceeds in the presence of a base and H(2)O to provide α,β,β-trifluorostyrene derivatives in satisfactory yields.

  2. Amino acid salt catalyzed intramolecular Robinson annulation†‡

    PubMed Central

    Li, Pingfan; Yamamoto, Hisashi

    2009-01-01

    The silica gel absorbed amino acid salt catalyzed asymmetric intramolecular Robinson annulation reaction has been developed; up to 97% ee was obtained with this readily recoverable organocatalyst. PMID:19724802

  3. The Iron-Catalyzed Oxidation of Hydrazine by Nitric Acid

    SciTech Connect

    Karraker, D.G.

    2001-07-17

    To assess the importance of iron to hydrazine stability, the study of hydrazine oxidation by nitric acid has been extended to investigate the iron-catalyzed oxidation. This report describes those results.

  4. Pd-Catalyzed Decarbonylative Cross-Couplings of Aroyl Chlorides.

    PubMed

    Malapit, Christian A; Ichiishi, Naoko; Sanford, Melanie S

    2017-08-04

    This report describes a method for Pd-catalyzed decarbonylative cross-coupling that enables the conversion of carboxylic acid derivatives to biaryls, aryl amines, aryl ethers, aryl sulfides, aryl boronate esters, and trifluoromethylated arenes. The success of this transformation leverages the Pd(0)/Brettphos-catalyzed decarbonylative chlorination of aroyl chlorides, which can then participate in diverse cross-coupling reactions in situ using the same Pd catalyst.

  5. Nickel-Catalyzed Coupling of Alkenes, Aldehydes, and Silyl Triflates

    PubMed Central

    Ng, Sze-sze; Ho, Chun-Yu; Jamison, Timothy F.

    2011-01-01

    A full account of two recently developed nickel-catalyzed coupling reactions of alkenes, aldehydes and silyl triflates is presented. These reactions provide either allylic alcohol or homoallylic alcohol derivatives selectively, depending on the ligand employed. These processes are believed to be mechanistically distinct from Lewis acid-catalyzed carbonyl-ene reactions, and several lines of evidence supporting this hypothesis are discussed. PMID:16939275

  6. New mechanistic studies on the proline-catalyzed aldol reaction

    PubMed Central

    List, Benjamin; Hoang, Linh; Martin, Harry J.

    2004-01-01

    The mechanism of the proline-catalyzed aldol reaction has stimulated considerable debate, and despite limited experimental data, at least five different mechanisms have been proposed. Complementary to recent theoretical studies we have initiated an experimental program with the goal of clarifying some of the basic mechanistic questions concerning the proline-catalyzed aldol reaction. Here we summarize our discoveries in this area and provide further evidence for the involvement of enamine intermediates. PMID:15073330

  7. Surface-catalyzed air oxidation of hydrazines: Environmental chamber studies

    NASA Technical Reports Server (NTRS)

    Kilduff, Jan E.; Davis, Dennis D.; Koontz, Steven L.

    1988-01-01

    The surface-catalyzed air oxidation reactions of fuel hydrazines were studied in a 6500-liter fluorocarbon-film chamber at 80 to 100 ppm concentrations. First-order rate constants for the reactions catalyzed by aluminum, water-damaged aluminum (Al/Al2O3), stainless steel 304L, galvanized steel and titanium plates with surface areas of 2 to 24 sq m were determined. With 23.8 sq m of Al/Al2O3 the surface-catalyzed air oxidation of hydrazine had a half-life of 2 hours, diimide (N2H2) was observed as an intermediate and traces of ammonia were present in the final product mixture. The Al/Al2O3 catalyzed oxidation of monomethylhydrazine yielded methyldiazine (HN = NCH3) as an intermediate and traces of methanol. Unsymmetrical dimethylhydrazine gave no detectable products. The relative reactivities of hydrazine, MMH and UDMH were 130 : 7.3 : 1.0, respectively. The rate constants for Al/Al2O3-catalyzed oxidation of hydrazine and MMH were proportional to the square of the surface area of the plates. Mechanisms for the surface-catalyzed oxidation of hydrazine and diimide and the formation of ammonia are proposed.

  8. Conservation Kickstart- Catalyzing Conservation Initiatives Worldwide

    NASA Astrophysics Data System (ADS)

    Treinish, G.

    2014-12-01

    Adventurers and Scientists for Conservation (ASC) is a nonprofit organization that collects environmental data to catalyze conservation initiatives worldwide. Adventure athletes have the skills and motivation to reach the most remote corners of the world. ASC utilizes those skills to provide the scientific community with data while providing the outdoor community with purpose beyond the personal high of reaching a summit or rowing across an ocean. We carefully select projects, choosing partnerships that will maximize the impact of ASC volunteers. Each project must have a clear path to a tangible conservation outcome and demonstrate a clear need for our brand of volunteers. We partner with government agencies, universities, and independant reseachers to kickstart data collection efforts around the world. Last year, through a partnership with the Olympic National Forest, 20 volunteers from the Seattle area set up and monitored camera traps in an effort to survey for costal Pacific marten. Our work led to the species' listing as "critically imperiled" with NatureServe. A partnership with the inaugural Great Pacific Race, engaging trans-Pacific rowing teams, searched for microplastics in the Pacific Ocean as part of our ongoing microplastics campaign. In a multi-year partnership with the American Prairie Reserve (APR), ASC volunteer crews live and work on the Reserve collecting wildlife data year round. The data we obtain directly informs the Reserve's wildlife management decisions. On this project, our crews have safely and effectively navigated temperature extremes from -30 degrees to 100+ degrees while traveling in a remote location. We are currently scouting projects in the Okavango Delta of Botswana and the rainforest of Suriname where we will be able to cover large amounts of area in a short periord of time. ASC is at the crossroads of the adventure and coservation science communities. Our approach of answering specific questions by using highly skilled and

  9. Base-Catalyzed Depolymerization of Biorefinery Lignins

    DOE PAGES

    Katahira, Rui; Mittal, Ashutosh; McKinney, Kellene; ...

    2016-01-12

    Lignocellulosic biorefineries will produce a substantial pool of lignin-enriched residues, which are currently slated to be burned for heat and power. Going forward, however, valorization strategies for residual solid lignin will be essential to the economic viability of modern biorefineries. To achieve these strategies, effective lignin depolymerization processes will be required that can convert specific lignin-enriched biorefinery substrates into products of sufficient value and market size. Base-catalyzed depolymerization (BCD) of lignin using sodium hydroxide and other basic media has been shown to be an effective depolymerization approach when using technical and isolated lignins relevant to the pulp and paper industry.more » Moreover, to gain insights in the application of BCD to lignin-rich, biofuels-relevant residues, here we apply BCD with sodium hydroxide at two catalyst loadings and temperatures of 270, 300, and 330 °C for 40 min to residual biomass from typical and emerging biochemical conversion processes. We obtained mass balances for each fraction from BCD, and characterized the resulting aqueous and solid residues using gel permeation chromatography, NMR, and GC–MS. When taken together, these results indicate that a significant fraction (45–78%) of the starting lignin-rich material can be depolymerized to low molecular weight, water-soluble species. The yield of the aqueous soluble fraction depends significantly on biomass processing method used prior to BCD. Namely, dilute acid pretreatment results in lower water-soluble yields compared to biomass processing that involves no acid pretreatment. We also find that the BCD product selectivity can be tuned with temperature to give higher yields of methoxyphenols at lower temperature, and a higher relative content of benzenediols with a greater extent of alkylation on the aromatic rings at higher temperature. Our study shows that residual, lignin-rich biomass produced from conventional and

  10. Cobalt-Catalyzed Alkylation of Aromatic Amines by Alcohols.

    PubMed

    Rösler, Sina; Ertl, Michael; Irrgang, Torsten; Kempe, Rhett

    2015-12-07

    The implementation of inexpensive, Earth-abundant metals in typical noble-metal-mediated chemistry is a major goal in homogeneous catalysis. A sustainable or green reaction that has received a lot of attention in recent years and is preferentially catalyzed by Ir or Ru complexes is the alkylation of amines by alcohols. It is based on the borrowing hydrogen or hydrogen autotransfer concept. Herein, we report on the Co-catalyzed alkylation of aromatic amines by alcohols. The reaction proceeds under mild conditions, and selectively generates monoalkylated amines. The observed selectivity allows the synthesis of unsymmetrically substituted diamines. A novel Co complex stabilized by a PN5 P ligand catalyzes the reactions most efficiently. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Divergent pathways lead to ESCRT-III-catalyzed membrane fission.

    PubMed

    Peel, Suman; Macheboeuf, Pauline; Martinelli, Nicolas; Weissenhorn, Winfried

    2011-04-01

    Endosomal sorting complexes required for transport (ESCRT) have been implicated in topologically similar but diverse cellular and pathological processes including multivesicular body (MVB) biogenesis, cytokinesis and enveloped virus budding. Although receptor sorting at the endosomal membrane producing MVBs employs the regulated assembly of ESCRT-0 followed by ESCRT-I, -II, -III and the vacuolar protein sorting (VPS)4 complex, other ESCRT-catalyzed processes require only a subset of complexes which commonly includes ESCRT-III and VPS4. Recent progress has shed light on the pathway of ESCRT assembly and highlights the separation of tasks of different ESCRT complexes and associated partners. The emerging picture suggests that among all ESCRT-catalyzed processes, divergent pathways lead to ESCRT-III assembly within the neck of a budding structure catalyzing membrane fission.

  12. Palladium-catalyzed modification of unprotected nucleosides, nucleotides, and oligonucleotides.

    PubMed

    Shaughnessy, Kevin H

    2015-05-22

    Synthetic modification of nucleoside structures provides access to molecules of interest as pharmaceuticals, biochemical probes, and models to study diseases. Covalent modification of the purine and pyrimidine bases is an important strategy for the synthesis of these adducts. Palladium-catalyzed cross-coupling is a powerful method to attach groups to the base heterocycles through the formation of new carbon-carbon and carbon-heteroatom bonds. In this review, approaches to palladium-catalyzed modification of unprotected nucleosides, nucleotides, and oligonucleotides are reviewed. Polar reaction media, such as water or polar aprotic solvents, allow reactions to be performed directly on the hydrophilic nucleosides and nucleotides without the need to use protecting groups. Homogeneous aqueous-phase coupling reactions catalyzed by palladium complexes of water-soluble ligands provide a general approach to the synthesis of modified nucleosides, nucleotides, and oligonucleotides.

  13. Highly efficient palladium-catalyzed hydrostannation of ethyl ethynyl ether.

    PubMed

    Andrews, Ian P; Kwon, Ohyun

    2008-12-08

    The palladium-catalyzed hydrostannation of acetylenes is widely exploited in organic synthesis as a means of forming vinyl stannanes for use in palladium-catalyzed cross-coupling reactions. Application of this methodology to ethyl ethynyl ether results in an enol ether that is challenging to isolate from the crude reaction mixture because of incompatibility with typical silica gel chromatography. Reported here is a highly efficient procedure for the palladium-catalyzed hydrostannation of ethyl ethynyl ether using 0.1% palladium(0) catalyst and 1.0 equiv of tributyltin hydride. The product obtained is a mixture of regioisomers that can be carried forward with exclusive reaction of the beta-isomer. This method is highly reproducible; relative to previously reported procedures, it is more economical and involves a more facile purification procedure.

  14. Metal-Catalyzed Asymmetric Michael Addition in Natural Product Synthesis.

    PubMed

    Hui, Chunngai; Pu, Fan; Xu, Jing

    2016-12-19

    Asymmetric catalysis for chiral compound synthesis is a rapidly growing field in modern organic chemistry. Asymmetric catalytic processes have been indispensable for the synthesis of enantioselective materials to meet demands from various fields. Michael addition has been used extensively for the construction of C-C bonds under mild conditions. With the discovery and development of organo- and metal-catalyzed asymmetric Michael additions, the synthesis of enantioselective and/or diastereoselective Michael adducts has become possible and increasingly prevalent in the literature. In particular, metal-catalyzed asymmetric Michael addition has been employed as a key reaction in natural product synthesis for the construction of contiguous quaternary stereogenic center(s), which is still a difficult task in organic synthesis. Previously reported applications of metal-catalyzed asymmetric Michael additions in natural product synthesis are presented here and discussed in depth.

  15. Stau-catalyzed big-bang nucleosynthesis reactions

    NASA Astrophysics Data System (ADS)

    Kamimura, Masayasu; Kino, Yasushi; Hiyama, Emiko

    2010-06-01

    We study the new type of big-bang nucleosynthesis (BBN) reactions that are catalyzed by a hypothetical long-lived negatively charged, massive leptonic particle (called X-) such as the supersymmetric (SUSY) particle stau, the scalar partner of the tau lepton. It is known that if the X- particle has a lifetime of τX>~103 s, it can capture a light element previously synthesized in standard BBN and form a Coulombic bound state and induces various types of reactions in which X- acts as a catalyst. Some of these X- catalyzed reactions have significantly large cross sections so that the inclusion of the reactions into the BBN network calculation can markedly change the abundances of some elements. We use a high-accuracy three-body calculation method developed by the authors and provide precise cross sections and rates of these catalyzed BBN reactions for use in the BBN network calculation.

  16. Phosphine-Catalyzed [4 + 2] Annulation: Synthesis of Cyclohexenes

    PubMed Central

    Tran, Yang S.

    2008-01-01

    Phosphine-catalyzed [4 + 2] annulations of α-alkylallenoates with activated olefins allow the efficient syntheses of cyclohexenes. Hexamethylphosphorous triamide (HMPT)-catalyzed [4 + 2] annulations of α-alkylallenoates with arylidenemalononitriles provided highly functionalized 5,5-dicyano-4,6-disubstituted cyclohex-1-enecarboxylates in excellent yields (77–98%) and moderate to high diastereoselectivities (1:2–12:1). Remarkably, the corresponding triarylphosphine-catalyzed [4 + 2] annulations of α-methylallenoate with arylidenemalononitriles manifested a polarity inversion of the 1,4-dipole synthon, providing 4,4-dicyano-5-substituted cyclohex-1-enecarboxylates in excellent yields (80–93%). The polarity inversion of α-alkylallenoates from one 1,4-dipole to another under phosphine catalysis presumably resulted from a change in the balance of the equilibrium between the phosphonium dienolate and the vinylogous phosphonium ylide intermediate. PMID:17914823

  17. Atom transfer and rearrangement reactions catalyzed by methyltrioxorhenium, MTO

    SciTech Connect

    Jacob, Josemon

    1999-05-10

    Methyltrioxorhenium (MTO) catalyzes the desulfurization of thiiranes by triphenylphosphine. Enormous enhancement in rate is observed when the catalyst is pretreated with hydrogen sulfide prior to the reaction. Using 2-mercaptomethylthiophenol as a ligand, the author synthesized several model complexes to study the mechanism of this reaction. With suitable model systems, they were able to show that the active catalyst is a Re(V) species. The reactions are highly stereospecific and very tolerant to functional groups. As part of the studies, he synthesized and crystallographically characterized the first examples of neutral terminal and bridging Re(V)sulfidocomplexes. Some of these complexes undergo fast oxygen atom transfer reactions with organic and inorganic oxidants. Studies on these model complexes led them to the discovery that MTO catalyzes the selective oxidation of thiols to disulfides. This report contains the Introduction; ``Chapter 6: Isomerization of Propargylic Alcohols to Enones and Enals Catalyzed by Methylrhenium Trioxide``; and Conclusions.

  18. Gold-Catalyzed Rearrangements and Beyond

    PubMed Central

    2013-01-01

    Cycloisomerizations of enynes are probably the most representative carbon–carbon bond forming reactions catalyzed by electrophilic metal complexes. These transformations are synthetically useful because chemists can use them to build complex architectures under mild conditions from readily assembled starting materials. However, these transformations can have complex mechanisms. In general, gold(I) activates alkynes in the presence of any other unsaturated functional group by forming an (η2-alkyne)–gold complex. This species reacts readily with nucleophiles, including electron-rich alkenes. In this case, the reaction forms cyclopropyl gold(I) carbene-like intermediates. These can come from different pathways depending on the substitution pattern of the alkyne and the alkene. In the absence of external nucleophiles, 1,n-enynes can form products of skeletal rearrangement in fully intramolecular reactions, which are mechanistically very different from metathesis reactions initiated by the [2 + 2] cycloaddition of a Grubbs-type carbene or other related metal carbenes. In this Account, we discuss how cycloisomerization and addition reactions of substituted enynes, as well as intermolecular reactions between alkynes and alkenes, are best interpreted as proceeding through discrete cationic intermediates in which gold(I) plays a significant role in the stabilization of the positive charge. The most important intermediates are highly delocalized cationic species that some chemists describe as cyclopropyl gold(I) carbenes or gold(I)-stabilized cyclopropylmethyl/cyclobutyl/homoallyl carbocations. However, we prefer the cyclopropyl gold(I) carbene formulation for its simplicity and mnemonic value, highlighting the tendency of these intermediates to undergo cyclopropanation reactions with alkenes. We can add a variety of hetero- and carbonucleophiles to the enynes in the presence of gold(I) in intra- or intermolecular reactions, leading to the corresponding adducts with

  19. Microbial-Catalyzed Biotransformation of Multifunctional Triterpenoids Derived from Phytonutrients

    PubMed Central

    Shah, Syed Adnan Ali; Tan, Huey Ling; Sultan, Sadia; Mohd Faridz, Muhammad Afifi Bin; Mohd Shah, Mohamad Azlan Bin; Nurfazilah, Sharifah; Hussain, Munawar

    2014-01-01

    Microbial-catalyzed biotransformations have considerable potential for the generation of an enormous variety of structurally diversified organic compounds, especially natural products with complex structures like triterpenoids. They offer efficient and economical ways to produce semi-synthetic analogues and novel lead molecules. Microorganisms such as bacteria and fungi could catalyze chemo-, regio- and stereospecific hydroxylations of diverse triterpenoid substrates that are extremely difficult to produce by chemical routes. During recent years, considerable research has been performed on the microbial transformation of bioactive triterpenoids, in order to obtain biologically active molecules with diverse structures features. This article reviews the microbial modifications of tetranortriterpenoids, tetracyclic triterpenoids and pentacyclic triterpenoids. PMID:25003642

  20. N-Heterocyclic-Carbene-Catalyzed Umpolung of Imines.

    PubMed

    Patra, Atanu; Mukherjee, Subrata; Das, Tamal Kanti; Jain, Shailja; Gonnade, Rajesh G; Biju, Akkattu T

    2017-03-01

    N-Heterocyclic carbene (NHC) catalysis has been widely used for the umpolung of aldehydes, and recently for the umpolung of Michael acceptors. Described herein is the umpolung of aldimines catalyzed by NHCs, and the reaction likely proceeds via aza-Breslow intermediates. The NHC-catalyzed intramolecular cyclization of aldimines bearing a Michael acceptor resulted in the formation of biologically important 2-(hetero)aryl indole 3-acetic-acid derivatives in moderate to good yields. The carbene generated from the bicyclic triazolium salt was found to be efficient for this transformation.

  1. Chromium(II)-catalyzed enantioselective arylation of ketones

    PubMed Central

    Wang, Gang; Sun, Shutao; Mao, Ying; Xie, Zhiyu

    2016-01-01

    The chromium-catalyzed enantioselective addition of carbo halides to carbonyl compounds is an important transformation in organic synthesis. However, the corresponding catalytic enantioselective arylation of ketones has not been reported to date. Herein, we report the first Cr-catalyzed enantioselective addition of aryl halides to both arylaliphatic and aliphatic ketones with high enantioselectivity in an intramolecular version, providing facile access to enantiopure tetrahydronaphthalen-1-ols and 2,3-dihydro-1H-inden-1-ols containing a tertiary alcohol. PMID:28144349

  2. Zirconium-Catalyzed Asymmetric Carboalumination of Unactivated Terminal Alkenes.

    PubMed

    Xu, Shiqing; Negishi, Ei-Ichi

    2016-10-18

    Carbometalation of alkenes with stereocontrol offers an important opportunity for asymmetric C-C bond formation. However, the scope of catalytic stereoselective carbometalation of alkenes had until recently been limited to electronically biased alkenes or those with the presence of directing groups or other auxiliary functionalities to overcome the challenge associated with regio- and stereoselectivity. Catalytic asymmetric carbometalation of unactivated alkenes on the other hand remained as a formidable challenge. To address this long-standing problem, we sought to develop Zr-catalyzed asymmetric carboalumination of alkenes (namely, ZACA reaction) encouraged by our discovery of Zr-catalyzed alkyne carboalumination in 1978. Zr-catalyzed methylalumination of alkynes (ZMA) shows high regioselectivity and nearly perfect stereoselectivity. Its mechanistic studies have revealed that the ZMA reaction involves acyclic carbometalation with "superacidic" bimetallic reagents generated by interaction between two Lewis acids, i.e., alkylalanes and 16-electron zirconocene derivatives through dynamic polarization and ate complexation, affectionately termed as the "two-is-better-than-one" principle. With the encouraging results of Zr-catalyzed carboalumination of alkynes in hand, we sought to develop its alkene version for discovering a catalytic asymmetric C-C bond-forming reaction by using alkylalanes and suitable chiral zirconocene derivatives, which would generate "superacidic" bimetallic species to promote the desired carbometalation of alkenes. However, this proved to be quite challenging. Three major competing side reactions occur, i.e., (i) β-H transfer hydrometalation, (ii) bimetallic cyclic carbometalation, and (iii) Ziegler-Natta polymerization. The ZACA reaction was finally discovered by employing Erker's (-)-(NMI)2ZrCl2 as the catalyst and chlorinated hydrocarbon as solvent to suppress the undesired side reactions mentioned above. The ZACA reaction has evolved as a

  3. Coalification by clay-catalyzed oligomerization of plant monomers

    SciTech Connect

    Orchin, M.; Wilson, R.M.

    1990-01-01

    The main objective of this research program is to devise laboratory methods to mimic the processes by which plants synthesize lignans, lignins and the processes by which these materials are transformed further by geochemical reactions catalyzed by certain clays to coal-like materials. We believe that the radical cation Diels-Alder reaction is one of the principal routes which transforms simple plant materials to coal-like substances and that such reactions may be catalyzed by clays that occur in the environment of the decaying plant materials. Progress is described.

  4. Molecular Mechanism by which One Enzyme Catalyzes Two Reactions

    NASA Astrophysics Data System (ADS)

    Nishimasu, Hiroshi; Fushinobu, Shinya; Wakagi, Takayoshi

    Unlike ordinary enzymes, fructose-1,6-bisphosphate (FBP) aldolase/phosphatase (FBPA/P) catalyzes two distinct reactions : (1) the aldol condensation of dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate to FBP, and (2) the dephosphorylation of FBP to fructose-6-phosphate. We solved the crystal structures of FBPA/P in complex with DHAP (its aldolase form) and FBP (its phosphatase form). The crystal structures revealed that FBPA/P exhibits the dual activities through a dramatic conformational change in the active-site architecture. Our findings expand the conventional concept that one enzyme catalyzes one reaction.

  5. New Palladium-Catalyzed Approaches to Heterocycles and Carbocycles

    SciTech Connect

    Huang, Qinhua

    2004-12-19

    The tert-butylimines of o-(1-alkynyl)benzaldehydes and analogous pyridinecarbaldehydes have been cyclized under very mild reaction conditions in the presence of I2, ICl, PhSeCl, PhSCl and p-O2NC6H4SCl to give the corresponding halogen-, selenium- and sulfur-containing disubstituted isoquinolines and naphthyridines, respectively. Monosubstituted isoquinolines and naphthyridines have been synthesized by the metal-catalyzed ring closure of these same iminoalkynes. This methodology accommodates a variety of iminoalkynes and affords the anticipated heterocycles in moderate to excellent yields. The Pd(II)-catalyzed cyclization of 2-(1-alkynyl)arylaldimines in the presence of various alkenes provides an efficient way to synthesize a variety of 4-(1-alkenyl)-3-arylisoquinolines in moderate to excellent yields. The introduction of an ortho-methoxy group on the arylaldimine promotes the Pd-catalyzed cyclization and stabilizes the resulting Pd(II) intermediate, improving the yields of the isoquinoline products. Highly substituted naphthalenes have been synthesized by the palladium-catalyzed annulation of a variety of internal alkynes, in which two new carbon-carbon bonds are formed in a single step under relatively mild reaction conditions. This method has also been used to synthesize carbazoles, although a higher reaction temperature is necessary. The process involves arylpalladation of the alkyne, followed by intramolecular Heck olefination and double bond isomerization. This method accommodates a variety of functional groups and affords the anticipated highly substituted naphthalenes and carbazoles in good to excellent yields. Novel palladium migratiodarylation methodology for the synthesis of complex fused polycycles has been developed, in which one or more sequential Pd-catalyzed intramolecular migration processes involving C-H activation are employed. The chemistry works best with electron-rich aromatics, which is in agreement

  6. Calreticulin mutations in Chinese with primary myelofibrosis

    PubMed Central

    Li, Bing; Xu, Junqing; Wang, Jingya; Gale, Robert Peter; Xu, Zefeng; Cui, Yajuan; Yang, Lin; Xing, Ruixian; Ai, Xiaofei; Qin, Tiejun; Zhang, Yue; Zhang, Peihong; Xiao, Zhijian

    2014-01-01

    We tested 357 Chinese with primary myelofibrosis for mutations in CALR, JAK2 and MPL. CALR mutations were detected in 76 subjects (21%). There were 24 (32%) type-1 (L367fs*46) and 49 (64%) type-2 (K385fs*47) mutations. Seventy-two of 168 subjects (43%) without a JAK2 or MPL mutation had a CALR mutation. Subjects with a type-2 CALR mutation had lower hemoglobin concentrations (P=0.001), lower WBC counts (P<0.001), a higher percentage of blood blasts (P=0.009), and higher conventional (P<0.001) and Chinese-adjusted Dynamic International Prognostic Scoring System (P<0.001) scores compared with subjects with JAK2 mutations. Subjects with a type-2 CALR mutation were also likely to have abnormal platelet levels (<100 × 109/L, P=0.01 or >450 × 109/L, P=0.042) and no splenomegaly (P=0.004). Type-2 CALR mutation or no detectable mutation was an independent high-risk factor for survival in multivariate analyses. These data suggest the ratio between type-1 and type-2 mutations is reversed in Chinese with primary myelofibrosis compared with populations of subjects with primary myelofibrosis of predominately European descent. The unfavorable prognostic impact of CALR mutations in Chinese with primary myelofibrosis is only seen in those with type-2 mutations. These data underscore the need to evaluate the prognostic impact of genetic mutations in different populations. PMID:24997152

  7. Calreticulin Mutations in Bulgarian MPN Patients.

    PubMed

    Pavlov, Ivan; Hadjiev, Evgueniy; Alaikov, Tzvetan; Spassova, Sylva; Stoimenov, Angel; Naumova, Elissaveta; Shivarov, Velizar; Ivanova, Milena

    2017-04-14

    Somatic mutations in JAK2, MPL and CALR are recurrently identified in most of the cases with Philadelphia chromosome negative myeloproliferative neoplasms (MPNs). We applied four molecular genetic methods for identification of CALR exon 9 mutations, including high resolution melt (HRM) analysis, Sanger sequencing, semiconductor target genes sequencing and whole exome sequencing. A total of 78 patients with myeloid malignancies were included in the study. We identified 14 CALR exon 9 mutated cases out of 78 studied patients with myeloid malignancies. All mutated patients were diagnosed with MPN being either PMF (n = 7) or ET (n = 7). Nine cases had type 1 mutations and 5 cases had type 2 mutations. CALR exon 9, MPL exon 10 and JAK2 p. V617F were mutually exclusive. There were no statistically significant differences in the hematological parameters between the cases with CALR and JAK2 or MPL mutations. Notably, all four techniques were fully concordant in the detection of CALR mutations. This is one of the few reports on the CALR mutations frequency in South-eastern populations. Our study shows that the frequency and patterns of these mutations is identical to those in the patients' cohorts from Western countries. Besides we demonstrated the utility of four different methods for their detection.

  8. Umpolung of Michael acceptors catalyzed by N-heterocyclic carbenes.

    PubMed

    Fischer, Christian; Smith, Sean W; Powell, David A; Fu, Gregory C

    2006-02-08

    N-Heterocyclic carbenes can catalyze beta-alkylations of a range of alpha,beta-unsaturated esters, amides, and nitriles that bear pendant leaving groups to form a variety of ring sizes. In this process, the nucleophilic catalyst transiently transforms the normally electrophilic beta carbon into a nucleophilic site through an unanticipated addition-tautomerization sequence.

  9. Rh-Catalyzed Asymmetric Hydrogenation of 1,2-Dicyanoalkenes.

    PubMed

    Li, Meina; Kong, Duanyang; Zi, Guofu; Hou, Guohua

    2017-01-06

    A highly efficient enantioselective hydrogenation of 1,2-dicyanoalkenes catalyzed by the complex of rhodium and f-spiroPhos has been developed. A series of 1,2-dicyanoalkenes were successfully hydrogenated to the corresponding chiral 1,2-dicyanoalkanes under mild conditions with excellent enantioselectivities (up to 98% ee). This methodology provides efficient access to the asymmetric synthesis of chiral diamines.

  10. Total Synthesis of Gelsenicine via a Catalyzed Cycloisomerization Strategy

    PubMed Central

    Newcomb, Eric T.; Knutson, Phil C.; Pedersen, Blaine A.; Ferreira, Eric M.

    2016-01-01

    The first total synthesis of (±)-gelsenicine is reported. The synthetic route is highly efficient (13 steps), featuring (1) a pivotal metal-catalyzed isomerization/rearrangement process that forges the central core of the molecule and (2) two facile C–N bond-forming steps that establish the flanking heterocycles. PMID:26716762

  11. Synthesis of Cyclic Guanidines via Pd-Catalyzed Alkene Carboamination

    PubMed Central

    Zavesky, Blane P.; Babij, Nicholas R.; Fritz, Jonathan A.

    2013-01-01

    A new approach to the synthesis of substituted 5-membered cyclic guanidines is described. Palladium-catalyzed alkene carboamination reactions between acyclic N-allyl guanidines and aryl or alkenyl halides provide these products in good yield. This method allows access to a number of different cyclic guanidine derivatives in only two steps from readily available allylic amines. PMID:24147839

  12. N-heterocyclic carbene catalyzed direct carbonylation of dimethylamine.

    PubMed

    Li, Xiaonian; Liu, Kun; Xu, Xiaoliang; Ma, Lei; Wang, Hong; Jiang, Dahao; Zhang, Qunfeng; Lu, Chunshan

    2011-07-21

    N-Heterocyclic carbene (NHC) catalyzed direct carbonylation of dimethylamine leading to the formation of DMF was successfully accomplished under metal-free conditions. The catalytic efficiency was investigated and the turnover numbers can reach as high as >300. The possible mechanism was also proposed.

  13. Catalyzing Graduate Teaching Assistants' Laboratory Teaching through Design Research

    ERIC Educational Resources Information Center

    Bond-Robinson, Janet; Rodriques, Romola A. Bernard

    2006-01-01

    We report on a study of a laboratory teaching apprenticeship program designed to improve graduate teaching assistant (GTA) performance. To catalyze GTAs as laboratory teachers we constructed learning goals, synthesized previous literature into a design model and a developmental path, and built two instruments to measure 12 strategic pedagogical…

  14. Nickel-catalyzed decarboxylative carboamination of alkynes with isatoic anhydrides.

    PubMed

    Yoshino, Yasufumi; Kurahashi, Takuya; Matsubara, Seijiro

    2009-06-10

    An intermolecular nickel-catalyzed addition reaction in which isatoic anhydrides react with alkynes to afford substituted quinolones has been developed. A mechanistic rationale is proposed, implying oxidative addition of Ni(0) to a carbamate, which allows intermolecular addition to alkynes via decarboxylation.

  15. Cu(I)-Catalyzed Asymmetric Diamination of Conjugated Dienes

    PubMed Central

    Du, Haifeng; Zhao, Baoguo; Yuan, Weicheng; Shi, Yian

    2009-01-01

    A Cu(I)-catalyzed asymmetric diamination for a variety of conjugated dienes and a triene with encouraging ee’s has been effectively achieved using (R)-DTBM-SEGPHOS as chiral ligand and di-tert-butyldiaziridinone as nitrogen source. PMID:18763785

  16. Development of a Lewis Base Catalyzed Selenocyclization Reaction

    ERIC Educational Resources Information Center

    Collins, William

    2009-01-01

    The concept of Lewis base activation of selenium Lewis acids has been effectively reduced to practice in the Lewis base catalyzed selenofunctionalization of unactivated olefins. In this reaction, the weakly acidic species, "N"-phenylselenyl succinimide, is cooperatively activated by the addition of a "soft" Lewis base donor (phosphine sulfides,…

  17. Palladium-Catalyzed Synthesis of 9-Fluorenylidenes through Aryne Annulation

    PubMed Central

    Worlikar, Shilpa A.; Larock, Richard C.

    2009-01-01

    The palladium-catalyzed annulation of arynes by substituted ortho-halostyrenes produces substituted 9- fluorenylidenes in good yields. This methodology provides this important carbocyclic ring system in a single step, which involves the generation of two new carbon-carbon bonds, occurs under relatively mild reaction conditions and tolerates a variety of functional groups, including cyano, ester, aldehyde and ketone groups. PMID:19413328

  18. Transition-Metal-Catalyzed Carbonylation of Methyl Acetate.

    ERIC Educational Resources Information Center

    Polichnowski, S. W.

    1986-01-01

    Presents a study of the rhodium-catalyzed, ioding-promoted carbonylation of methyl acetate. This study provides an interesting contrast between the carbonylation of methyl acetate and the carbonylation of methanol when similar rhodium/iodine catalyst systems are used. (JN)

  19. Acid-catalyzed dehydrogenation of amine-boranes

    DOEpatents

    Stephens, Frances Helen; Baker, Ralph Thomas

    2010-01-12

    A method of dehydrogenating an amine-borane using an acid-catalyzed reaction. The method generates hydrogen and produces a solid polymeric [R.sup.1R.sup.2B--NR.sup.3R.sup.4].sub.n product. The method of dehydrogenating amine-boranes may be used to generate H.sub.2 for portable power sources.

  20. Palladium-catalyzed direct arylation of indoles with cyclohexanones.

    PubMed

    Chen, Shanping; Liao, Yunfeng; Zhao, Feng; Qi, Hongrui; Liu, Saiwen; Deng, Guo-Jun

    2014-03-21

    A novel palladium catalyzed approach to 3-arylindoles was developed from indoles and cyclohexanones. Various cyclohexanones acted as aryl sources via an alkylation and dehydrogenation sequence using molecular oxygen as the hydrogen acceptor. This method showed good regioselectivity and afforded 3-arylindoles as the sole products.

  1. Palladium-catalyzed stereocontrolled vinylation of azoles and phenothiazine.

    PubMed

    Lebedev, Artyom Y; Izmer, Vyatcheslav V; Kazyul'kin, Denis N; Beletskaya, Irina P; Voskoboynikov, Alexander Z

    2002-02-21

    [reaction: see text] Vinylation of various azoles (pyrrole, indole, carbazole, and their derivatives) and phenothiazine with vinyl bromides catalyzed by palladium-phosphine complexes results in the respective N-vinylazoles in 30-99% yields. This reaction with cis- and trans-beta-bromostyrenes is stereospecific giving the respective products with full retention of configuration.

  2. Asymmetric gold-catalyzed lactonizations in water at room temperature.

    PubMed

    Handa, Sachin; Lippincott, Daniel J; Aue, Donald H; Lipshutz, Bruce H

    2014-09-26

    Asymmetric gold-catalyzed hydrocarboxylations are reported that show broad substrate scope. The hydrophobic effect associated with in situ-formed aqueous nanomicelles gives good to excellent ee's of product lactones. In-flask product isolation, along with the recycling of the catalyst and the reaction medium, are combined to arrive at an especially environmentally friendly process.

  3. Silver-catalyzed protodecarboxylation of heteroaromatic carboxylic acids.

    PubMed

    Lu, Pengfei; Sanchez, Carolina; Cornella, Josep; Larrosa, Igor

    2009-12-17

    A simple and highly efficient protodecarboxylation procedure for a variety of heteroaromatic carboxylic acids catalyzed by Ag(2)CO(3) and AcOH in DMSO is described. This methodology can also perform the selective monoprotodecarboxylation of several aromatic dicarboxylic acids.

  4. Cu-Catalyzed Fluorination of Diaryliodonium Salts with KF

    PubMed Central

    Ichiishi, Naoko; Canty, Allan J.; Yates, Brian F.

    2014-01-01

    A mild Cu-catalyzed nucleophilic fluorination of unsymmetrical diaryliodonium salts with KF is described. This protocol preferentially fluorinates less sterically hindered aromatic rings. The reaction exhibits a broad substrate scope and proceeds with high chemoselectivity and functional group tolerance. DFT calculations implicate a CuI/CuIII catalytic cycle. PMID:24063629

  5. Transition-Metal-Catalyzed Carbonylation of Methyl Acetate.

    ERIC Educational Resources Information Center

    Polichnowski, S. W.

    1986-01-01

    Presents a study of the rhodium-catalyzed, ioding-promoted carbonylation of methyl acetate. This study provides an interesting contrast between the carbonylation of methyl acetate and the carbonylation of methanol when similar rhodium/iodine catalyst systems are used. (JN)

  6. Cu(II) - Catalyzed Hydrazine Reduction of Ferrous Nitrate

    SciTech Connect

    Karraker, D.G.

    2001-10-15

    This report discusses the results of a study of catalyzed hydrazine reduction of ferrous nitrate. It is apparent that there is a substantial reaction between hydrazine and nitrate ion (or nitric acid) to produce HN3 during both the reduction of Fe(III) and during storage at room temperature.

  7. Copper-catalyzed asymmetric reduction of 3,3-diarylacrylonitriles.

    PubMed

    Lee, Daehyung; Yang, Youngmin; Yun, Jaesook

    2007-07-05

    CuH-catalyzed enantioselective conjugate reduction of 3,3-diaryl-substituted acrylonitriles is described. A range of 3-aryl-3-pyridylacrylonitriles were reduced with high levels of enantioselectivity under optimal conditions employing a copper/Josiphos complex in the presence of polymethylhydrosiloxane (PMHS).

  8. Palladium-catalyzed silylation of aryl chlorides with hexamethyldisilane.

    PubMed

    McNeill, Eric; Barder, Timothy E; Buchwald, Stephen L

    2007-09-13

    A method for the palladium-catalyzed silylation of aryl chlorides has been developed. The method affords desired product in good yield, is tolerant of a variety of functional groups, and provides access to a wide variety of aryltrimethylsilanes from commercially available aryl chlorides. Additionally, a one-pot procedure that converts aryl chlorides into aryl iodides has been developed.

  9. Copper-catalyzed radical carbooxygenation: alkylation and alkoxylation of styrenes.

    PubMed

    Liao, Zhixiong; Yi, Hong; Li, Zheng; Fan, Chao; Zhang, Xu; Liu, Jie; Deng, Zixin; Lei, Aiwen

    2015-01-01

    A simple copper-catalyzed direct radical carbooxygenation of styrenes is developed utilizing alkyl bromides as radical resources. This catalytic radical difunctionalization accomplishes both alkylation and alkoxylation of styrenes in one pot. A broad range of styrenes and alcohols are well tolerated in this transformation. The EPR experiment shows that alkyl halides could oxidize Cu(I) to Cu(II) in this transformation.

  10. Metal-Catalyzed Cleavage of tRNA[superscript Phe

    ERIC Educational Resources Information Center

    Kirk, Sarah R.; Silverstein, Todd P.; McFarlane Holman, Karen L.

    2008-01-01

    This laboratory project is one component of a semester-long advanced biochemistry laboratory course that uses several complementary techniques to study tRNA[superscript Phe] conformational changes induced by ligand binding. In this article we describe a set of experiments in which students assay metal-catalyzed hydrolysis of tRNA[superscript Phe]…

  11. Enantioselective N-heterocyclic carbene-catalyzed synthesis of trifluoromethyldihydropyridinones.

    PubMed

    Wang, Dong-Ling; Liang, Zhi-Qin; Chen, Kun-Quan; Sun, De-Qun; Ye, Song

    2015-06-05

    The enantioselective N-heterocyclic carbene-catalyzed [4 + 2] cyclocondensation of α-chloroaldehydes and trifluoromethyl N-Boc azadienes was developed, giving the corresponding 3,4-disubstituted-6-trifluoromethyldihydropyridin-2(1H)-ones in good yields with exclusive cis-selectivities and excellent enantioselectivities.

  12. Ruthenium-catalyzed C–H activation of thioxanthones

    PubMed Central

    Wagner, Danny

    2015-01-01

    Summary Thioxanthones – being readily available in one step from thiosalicylic acid and arenes – were used in ruthenium-catalyzed C–H-activation reaction to produce 1-mono- or 1,8-disubstituted thioxanthones in good to excellent yields. Scope and limitation of this reaction are presented. PMID:25977717

  13. Palladium-catalyzed synthesis of functionalized tetraarylphosphonium salts.

    PubMed

    Marcoux, David; Charette, André B

    2008-01-18

    An efficient method to synthesize functionalized tetraarylphosphonium salts is described. This palladium-catalyzed coupling reaction between aryl iodides, bromides, or triflates and triphenylphosphine generates phosphonium salts in high yields. The coupling is compatible with a variety of functional groups such as alcohols, ketones, aldehydes, phenols, and amides.

  14. Palladium(II)-catalyzed direct alkenylation of nonaromatic enamides.

    PubMed

    Gigant, Nicolas; Gillaizeau, Isabelle

    2012-07-06

    A mild and efficient method for the direct alkenylation of nonaromatic enamides was achieved through a palladium(II)-catalyzed C-H functionalization. The reaction scope includes cyclic and acyclic enamides and a range of activated alkenes. This approach represents the first successful direct C(3)-functionalization of nonaromatic cyclic enamides.

  15. Zinc-catalyzed cyclopropenation of alkynes via 2-furylcarbenoids.

    PubMed

    González, María J; López, Luis A; Vicente, Rubén

    2014-11-07

    An unprecedented cyclopropenation reaction of alkynes catalyzed by ZnCl2 is reported. While Simmons-Smith-type carbenoids failed in the [2 + 1]-cycloaddition with alkynes, the use of enynones as the carbene source enables the preparation of substituted 2-furyl cyclopropene derivatives with remarkable scope.

  16. Metal-Catalyzed Cleavage of tRNA[superscript Phe

    ERIC Educational Resources Information Center

    Kirk, Sarah R.; Silverstein, Todd P.; McFarlane Holman, Karen L.

    2008-01-01

    This laboratory project is one component of a semester-long advanced biochemistry laboratory course that uses several complementary techniques to study tRNA[superscript Phe] conformational changes induced by ligand binding. In this article we describe a set of experiments in which students assay metal-catalyzed hydrolysis of tRNA[superscript Phe]…

  17. Iron-Catalyzed Synthesis of Sulfur-Containing Heterocycles.

    PubMed

    Bosset, Cyril; Lefebvre, Gauthier; Angibaud, Patrick; Stansfield, Ian; Meerpoel, Lieven; Berthelot, Didier; Guérinot, Amandine; Cossy, Janine

    2016-10-13

    An iron-catalyzed synthesis of sulfur- and sulfone-containing heterocycles is reported. The method is based on the cyclization of readily available substrates and proceeded with high efficiency and diastereoselectivity. A variety of sulfur-containing heterocycles bearing moieties suitable for subsequent functionalization are prepared. Illustrative examples of such postcyclization modifications are also presented.

  18. Palladium-catalyzed enantioselective 1,1-fluoroarylation of aminoalkenes.

    PubMed

    He, Ying; Yang, Zhenyu; Thornbury, Richard T; Toste, F Dean

    2015-09-30

    The development of an enantioselective palladium-catalyzed 1,1-fluoroarylation of unactivated aminoalkenes is described. The reaction uses arylboronic acids as the arene source and Selectfluor as the fluorine source to generate benzylic fluorides in good yields with excellent enantioselectivities. This transformation, likely proceeding through an oxidative Heck mechanism, affords 1,1-difunctionalized alkene products.

  19. Palladium-Catalyzed Enantioselective 1,1-Fluoroarylation of Aminoalkenes

    PubMed Central

    2016-01-01

    The development of an enantioselective palladium-catalyzed 1,1-fluoroarylation of unactivated aminoalkenes is described. The reaction uses arylboronic acids as the arene source and Selectfluor as the fluorine source to generate benzylic fluorides in good yields with excellent enantioselectivities. This transformation, likely proceeding through an oxidative Heck mechanism, affords 1,1-difunctionalized alkene products. PMID:26378886

  20. Pd-catalyzed C-H fluorination with nucleophilic fluoride.

    PubMed

    McMurtrey, Kate B; Racowski, Joy M; Sanford, Melanie S

    2012-08-17

    The palladium-catalyzed C-H fluorination of 8-methylquinoline derivatives with nucleophilic fluoride is reported. This transformation involves the use of AgF as the fluoride source in combination with a hypervalent iodine oxidant. Both the scope and mechanism of the reaction are discussed.

  1. Palladium(III)-Catalyzed Fluorination of Arylboronic Acid Derivatives

    PubMed Central

    Tang, Pingping; Murphy, Jennifer M.; Ritter, Tobias

    2013-01-01

    A practical, palladium-catalyzed synthesis of aryl fluorides from arylboronic acid derivatives is presented. The reaction is operationally simple and amenable to multi-gram-scale synthesis. Evaluation of the reaction mechanism suggests a single-electron-transfer pathway, involving a Pd(III) intermediate that has been isolated and characterized. PMID:24040932

  2. Palladium(III)-catalyzed fluorination of arylboronic acid derivatives.

    PubMed

    Mazzotti, Anthony R; Campbell, Michael G; Tang, Pingping; Murphy, Jennifer M; Ritter, Tobias

    2013-09-25

    A practical, palladium-catalyzed synthesis of aryl fluorides from arylboronic acid derivatives is presented. The reaction is operationally simple and amenable to multigram-scale synthesis. Evaluation of the reaction mechanism suggests a single-electron-transfer pathway, involving a Pd(III) intermediate that has been isolated and characterized.

  3. Development of a Lewis Base Catalyzed Selenocyclization Reaction

    ERIC Educational Resources Information Center

    Collins, William

    2009-01-01

    The concept of Lewis base activation of selenium Lewis acids has been effectively reduced to practice in the Lewis base catalyzed selenofunctionalization of unactivated olefins. In this reaction, the weakly acidic species, "N"-phenylselenyl succinimide, is cooperatively activated by the addition of a "soft" Lewis base donor (phosphine sulfides,…

  4. Ruthenium-catalyzed tertiary amine formation from nitroarenes and alcohols.

    PubMed

    Feng, Chao; Liu, Yong; Peng, Shengming; Shuai, Qi; Deng, Guojun; Li, Chao-Jun

    2010-11-05

    A highly selective ruthenium-catalyzed C-N bond formation was developed by using the hydrogen-borrowing strategy. Various tertiary amines were obtained efficiently from nitroarenes and primary alcohols. The reaction tolerates a wide range of functionalities. A tentative mechanism was proposed for this direct amination reaction of alcohols with nitroarenes.

  5. Palladium catalyzed alkoxy- and aminocarbonylation of vinyl tosylates.

    PubMed

    Reeves, Diana C; Rodriguez, Sonia; Lee, Heewon; Haddad, Nizar; Krishnamurthy, Dhileepkumar; Senanayake, Chris H

    2011-05-06

    The palladium catalyzed alkoxycarbonylation and aminocarbonylation of vinyl tosylates are described. A variety of ketone and aldehyde derived vinyl tosylates may be carbonylated in the presence of primary, secondary, and tertiary alcohols, or primary and secondary amines, to provide the corresponding esters and amides in good yields. The alkoxycarbonylation was applied to a short synthesis of isoguvacine.

  6. Catalyzing Graduate Teaching Assistants' Laboratory Teaching through Design Research

    ERIC Educational Resources Information Center

    Bond-Robinson, Janet; Rodriques, Romola A. Bernard

    2006-01-01

    We report on a study of a laboratory teaching apprenticeship program designed to improve graduate teaching assistant (GTA) performance. To catalyze GTAs as laboratory teachers we constructed learning goals, synthesized previous literature into a design model and a developmental path, and built two instruments to measure 12 strategic pedagogical…

  7. N-Heterocyclic Carbene-Catalyzed Convenient Benzonitrile Assembly.

    PubMed

    Jia, Qianfa; Wang, Jian

    2016-05-06

    The benzonitrile unit is widely found in natural products, pharmaceuticals, and agrochemicals. Synthesis of benzonitriles has received considerable interests from the chemical community over the last few decades. Present synthetic protocols mainly rely on the pre-existing benzene core to install a cyano moiety. A new NHC-catalyzed [4 + 2]-benzannulation protocol is reported to assemble the benzonitrile framework.

  8. Palladium-catalyzed selective acyloxylation using sodium perborate as oxidant.

    PubMed

    Pilarski, Lukasz T; Janson, Pär G; Szabó, Kálmán J

    2011-03-04

    Sodium perborate (SPB), a principal component of washing powders, was employed as an inexpensive and eco-friendly oxidant in the palladium-catalyzed C-H acyloxylation of alkenes in excellent regio- and stereochemistry. The reactions used anhydrides as acyloxy sources. The method applies to both terminal and internal alkenes, and even benzylic C-H oxidation.

  9. Synthesis of benzimidazoles via iridium-catalyzed acceptorless dehydrogenative coupling.

    PubMed

    Sun, Xiang; Lv, Xiao-Hui; Ye, Lin-Miao; Hu, Yu; Chen, Yan-Yan; Zhang, Xue-Jing; Yan, Ming

    2015-07-21

    Iridium-catalyzed acceptorless dehydrogenative coupling of tertiary amines and arylamines has been developed. A number of benzimidazoles were prepared in good yields. An iridium-mediated C-H activation mechanism is suggested. This finding represents a novel strategy for the synthesis of benzimidazoles.

  10. Computational Studies on Cinchona Alkaloid-Catalyzed Asymmetric Organic Reactions.

    PubMed

    Tanriver, Gamze; Dedeoglu, Burcu; Catak, Saron; Aviyente, Viktorya

    2016-06-21

    Remarkable progress in the area of asymmetric organocatalysis has been achieved in the last decades. Cinchona alkaloids and their derivatives have emerged as powerful organocatalysts owing to their reactivities leading to high enantioselectivities. The widespread usage of cinchona alkaloids has been attributed to their nontoxicity, ease of use, stability, cost effectiveness, recyclability, and practical utilization in industry. The presence of tunable functional groups enables cinchona alkaloids to catalyze a broad range of reactions. Excellent experimental studies have extensively contributed to this field, and highly selective reactions were catalyzed by cinchona alkaloids and their derivatives. Computational modeling has helped elucidate the mechanistic aspects of cinchona alkaloid catalyzed reactions as well as the origins of the selectivity they induce. These studies have complemented experimental work for the design of more efficient catalysts. This Account presents recent computational studies on cinchona alkaloid catalyzed organic reactions and the theoretical rationalizations behind their effectiveness and ability to induce selectivity. Valuable efforts to investigate the mechanisms of reactions catalyzed by cinchona alkaloids and the key aspects of the catalytic activity of cinchona alkaloids in reactions ranging from pharmaceutical to industrial applications are summarized. Quantum mechanics, particularly density functional theory (DFT), and molecular mechanics, including ONIOM, were used to rationalize experimental findings by providing mechanistic insights into reaction mechanisms. B3LYP with modest basis sets has been used in most of the studies; nonetheless, the energetics have been corrected with higher basis sets as well as functionals parametrized to include dispersion M05-2X, M06-2X, and M06-L and functionals with dispersion corrections. Since cinchona alkaloids catalyze reactions by forming complexes with substrates via hydrogen bonds and long

  11. Reaction Pathway for Cocaine Hydrolase-Catalyzed Hydrolysis of (+)-Cocaine

    PubMed Central

    Yao, Yuan; Liu, Junjun; Zheng, Fang; Zhan, Chang-Guo

    2017-01-01

    A recently designed and discovered cocaine hydrolase (CocH), engineered from human butyrylcholinesterase (BChE), has been proven promising as a novel enzyme therapy for treatment of cocaine overdose and addiction because it is highly efficient in catalyzing hydrolysis of naturally occurring (−)-cocaine. It has been known that the CocH also has a high catalytic efficiency against (+)-cocaine, a synthetic enantiomer of cocaine. Reaction pathway and the corresponding free energy profile for the CocH-catalyzed hydrolysis of (+)-cocaine have been determined, in the present study, by performing first-principles pseudobond quantum mechanical/molecular mechanical (QM/MM)-free energy (FE) calculations. Acordingt to the QM/MM-FE results, the catalytic hydrolysis process is initiated by the nucleophilic attack on carbonyl carbon of (−)-cocaine benzoyl ester via hydroxyl oxygen of S198 side chain, and the second reaction step (i.e. dissociation of benzoyl ester) is rate-determining. This finding for CocH-catalyzed hydrolysis of (+)-cocaine is remarkably different from that for the (+)-cocaine hydrolysis catalyzed by bacterial cocaine esterase in which the first reaction step of the deacylation is associated with the highest free energy barrier (~17.9 kcal/mol). The overall free energy barrier (~16.0 kcal/mol) calculated for the acylation stage of CocH-catalyzed hydrolysis of (+)-cocaine is in good agreement with the experimental free energy barrier of ~14.5 kcal/mol derivated from the experimental kinetic data. PMID:28250715

  12. 4-Dimenthylaminopyridine or Acid-Catalyzed Synthesis of Esters: A Comparison

    ERIC Educational Resources Information Center

    van den Berg, Annemieke W. C.; Hanefeld, Ulf

    2006-01-01

    A set of highly atom-economic experiments was developed to highlight the differences between acid- and base-catalyzed ester syntheses and to introduce the principles of atom economy. The hydrochloric acid-catalyzed formation of an ester was compared with the 4-dimethylaminopyradine-catalyzed ester synthesis.

  13. 4-Dimenthylaminopyridine or Acid-Catalyzed Synthesis of Esters: A Comparison

    ERIC Educational Resources Information Center

    van den Berg, Annemieke W. C.; Hanefeld, Ulf

    2006-01-01

    A set of highly atom-economic experiments was developed to highlight the differences between acid- and base-catalyzed ester syntheses and to introduce the principles of atom economy. The hydrochloric acid-catalyzed formation of an ester was compared with the 4-dimethylaminopyradine-catalyzed ester synthesis.

  14. Kinetics of Imidazole Catalyzed Ester Hydrolysis: Use of Buffer Dilutions to Determine Spontaneous Rate, Catalyzed Rate, and Reaction Order.

    ERIC Educational Resources Information Center

    Lombardo, Anthony

    1982-01-01

    Described is an advanced undergraduate kinetics experiment using buffer dilutions to determine spontaneous rate, catalyzed rate, and reaction order. The reaction utilized is hydrolysis of p-nitro-phenyl acetate in presence of imidazole, which has been shown to enhance rate of the reaction. (Author/JN)

  15. Kinetics of Imidazole Catalyzed Ester Hydrolysis: Use of Buffer Dilutions to Determine Spontaneous Rate, Catalyzed Rate, and Reaction Order.

    ERIC Educational Resources Information Center

    Lombardo, Anthony

    1982-01-01

    Described is an advanced undergraduate kinetics experiment using buffer dilutions to determine spontaneous rate, catalyzed rate, and reaction order. The reaction utilized is hydrolysis of p-nitro-phenyl acetate in presence of imidazole, which has been shown to enhance rate of the reaction. (Author/JN)

  16. An optimized hydrogen target for muon catalyzed fusion

    NASA Astrophysics Data System (ADS)

    Gheisari, R.

    2011-04-01

    This paper deals with the optimization of the processes involved in muon catalyzed fusion. Muon catalyzed fusion ( μCF) is studied in all layers of the solid hydrogen structure H/0.1%T⊕D2⊕HD. The layer H/ T acts as an emitter source of energetic tμ atoms, due to the so-called Ramsauer-Townsend effect. These tμ atoms are slowed down in the second layer (degrader) and are forced to take place nuclear fusion in HD. The degrader affects time evolution of tμ atomic beam. This effect has not been considered until now in μCF-multilayered targets. Due to muon cycling and this effect, considerable reactions occur in the degrader. In our calculations, it is shown that the fusion yield equals 180±1.5. It is possible to separate events that overlap in time.

  17. Investigations into Transition Metal Catalyzed Arene Trifluoromethylation Reactions.

    PubMed

    Ye, Yingda; Sanford, Melanie S

    2012-09-01

    Trifluoromethyl-substituted arenes and heteroarenes are widely prevalent in pharmaceuticals and agrochemicals. As a result, the development of practical methods for the formation of aryl-CF3 bonds has become an active field of research. Over the past five years, transition metal catalyzed cross-coupling between aryl-X (X = halide, organometallic, or H) and various "CF3" reagents has emerged as a particularly exciting approach for generating aryl-CF3 bonds. Despite many recent advances in this area, current methods generally suffer from limitations such as poor generality, harsh reaction conditions, the requirement for stoichiometric quantities of metals, and/or the use of costly CF3 sources. This Account describes our recent efforts to address some of these challenges by: (1) developing aryl trifluoromethylation reactions involving high oxidation state Pd intermediates, (2) exploiting AgCF3 for C-H trifluoromethylation, and (3) achieving Cu-catalyzed trifluoromethylation with photogenerated CF3•.

  18. Cytochrome c catalyzes the in vitro synthesis of arachidonoyl glycine

    SciTech Connect

    McCue, Jeffrey M.; Driscoll, William J.; Mueller, Gregory P.

    2008-01-11

    Long chain fatty acyl glycines are an emerging class of biologically active molecules that occur naturally and produce a wide array of physiological effects. Their biosynthetic pathway, however, remains unknown. Here we report that cytochrome c catalyzes the synthesis of N-arachidonoyl glycine (NAGly) from arachidonoyl coenzyme A and glycine in the presence of hydrogen peroxide. The identity of the NAGly product was verified by isotope labeling and mass analysis. Other heme-containing proteins, hemoglobin and myoglobin, were considerably less effective in generating arachidonoyl glycine as compared to cytochrome c. The reaction catalyzed by cytochrome c in vitro points to its potential role in the formation of NAGly and other long chain fatty acyl glycines in vivo.

  19. Ligand development in the Ni-catalyzed hydrocyanation of alkenes.

    PubMed

    Bini, Laura; Müller, Christian; Vogt, Dieter

    2010-11-28

    The addition of HCN to alkenes is a very useful reaction for the synthesis of functional organic substrates. Industrially the nickel-catalyzed hydrocyanation has gained considerable importance mainly because of the production of adiponitrile in the DuPont process. In this process the hydrocyanation of butadiene is carried out using aryl phosphite-modified nickel catalyst. Since the performance of organo-transition metal complexes is largely determined by the ligand environment of the metal, fundamental understanding and ligand development is of pivotal importance for any progress. This feature article gives an account of the development and application of different mono- and bidentate phosphorus-based ligands in the Ni-catalyzed hydrocyanation reaction of alkenes. Special attention will be paid to the development of insight and understanding of the ligand structural and electronic properties towards the improvement of the catalyst performance in terms of stability, activity, and selectivity.

  20. Cholera toxin can catalyze ADP-ribosylation of cytoskeletal proteins

    SciTech Connect

    Kaslow, H.R.; Groppi, V.E.; Abood, M.E.; Bourne, H.R.

    1981-11-01

    Cholera toxin catalyzes transfer of radiolabel from (/sup 32/P)NAD/sup +/ to several peptides in particulate preparations of human foreskin fibroblasts. Resolution of these peptides by two-dimensional gel electrophoresis allowed identification of two peptides of M/sub r/ = 42,000 and 52,000 as peptide subunits of a regulatory component of adenylate cyclase. The radiolabeling of another group of peptides (M/sub r/ = 50,000 to 65,000) suggested that cholera toxin could catalyze ADP-ribosylation of cytoskeletal proteins. This suggestion was confirmed by showing that incubation with cholera toxin and (/sup 32/P)NAD/sup +/ caused radiolabeling of purified microtubule and intermediate filament proteins.

  1. Asymmetric oxidoreductions catalyzed by alcohol dehydrogenase in organic solvents

    SciTech Connect

    Grunwald, J.; Wirz, B.; Scollar, M.P.; Klibanov, A.M.

    1986-10-15

    A methodology is developed for the use of alcohol dehydrogenase (and other NAD/sup +//NADH-dependent enzymes) as catalysts in organic solvents. The enzyme and the cofactor are deposited onto the surface of glass beads which are then suspended in a water-immiscible organic solvent containing the substrate. Both NADH and NAD/sup +/ are efficiently regenerated in such a system with alcohol dehydrogenase-catalyzed oxidation of ethanol and reduction of isobutyraldehyde, respectively; cofactor turnover numbers of 10/sup 5/ to greater than 10/sup 6/ have been obtained. With use of asymmetric oxidoreductions catalyzed by horse liver alcohol dehydrogenase in isopropyl ether, optically active (ee of 95 to 100%) alcohols and ketones have been prepared on a 1 to 10 mmol scale.

  2. Erythrocyte enzymes catalyze 1-nitropyrene and 3-nitrofluoranthene nitroreduction.

    PubMed

    Belisario, M A; Pecce, R; Garofalo, A; Sannolo, N; Malorni, A

    1996-04-15

    Nitroarenes are environmental contaminants produced during incomplete combustion processes. Nitroreduction, the most important pathway of nitroarene toxification, occurs mainly in the liver and intestine. In the present study, we show that human red cells may also possess the metabolic competence to reduce 1-nitropyrene (NP) and 3-nitrofluoranthene (NF), the nitroarenes chosen as model compounds, to their corresponding amino derivatives, 1-aminopyrene (AP) and 3-aminofluoranthene (AF). The requirement of the cofactor couple NADH/FMN suggests that erythrocyte nitroreductase activity occurs via one electron transfer. The presence of oxygen strongly inhibited the haemolysate-catalyzed nitroarene reduction, whether measured as amine formation or nitroarene disappearance. Intermediate reactive species, that bind covalently to haemoglobin and/or other erythrocyte proteins, are formed during nitroreduction catalyzed by human haemolysate. In fact, the reduced metabolites AP and AF were released after mild acid hydrolysis of red cell proteins exposed to NP and NF, thus suggesting that sulphinamide adducts have been formed.

  3. Copper-Catalyzed Intramolecular Oxidative Amination of Unactivated Internal Alkenes.

    PubMed

    Xiong, Peng; Xu, Fan; Qian, Xiang-Yang; Yohannes, Yared; Song, Jinshuai; Lu, Xin; Xu, Hai-Chao

    2016-03-18

    A copper-catalyzed oxidative amination of unactivated internal alkenes has been developed. The Wacker-type oxidative alkene amination reaction is traditionally catalyzed by a palladium through a mechanism involving aminopalladation and β-hydride elimination. Replacing the precious and scarce palladium with a cheap and abundant copper for this transformation has been challenging because of the difficulty associated with the aminocupration of internal alkenes. The combination of a simple copper salt, without additional ligand, as the catalyst and Dess-Martin periodinane as the oxidant, promotes efficiently the oxidative amination of allylic carbamates and ureas bearing di- and trisubstituted alkenes leading to oxazolidinones and imidazolidinones. Preliminary mechanistic studies suggested a hybrid radical-organometallic mechanism involving an amidyl radical cyclization to form the key C-N bond. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Rearrangement Reactions Catalyzed by Cytochrome P450s

    PubMed Central

    Ortiz de Montellano, Paul R.; Nelson, Sidney D.

    2010-01-01

    Cytochrome P450s promote a variety of rearrangement reactions both as a consequence of the nature of the radical and other intermediates generated during catalysis, and of the neighboring structures in the substrate that can interact either with the initial radical intermediates or with further downstream products of the reactions. This article will review several kinds of previously published cytochrome P450-catalyzed rearrangement reactions, including changes in stereochemistry, radical clock reactions, allylic rearrangements, “NIH” and related shifts, ring contractions and expansions, and cyclizations that result from neighboring group interactions. Although most of these reactions can be carried out by many members of the cytochrome P450 superfamily, some have only been observed with select P450s, including some reactions that are catalyzed by specific endoperoxidases and cytochrome P450s found in plants. PMID:20971058

  5. Cross-ligation and exchange reactions catalyzed by hairpin ribozymes.

    PubMed Central

    Komatsu, Y; Koizumi, M; Sekiguchi, A; Ohtsuka, E

    1993-01-01

    The negative strand of the satellite RNA of tobacco ringspot virus (sTobRV(-)) contains a hairpin catalytic domain that shows self-cleavage and self-ligation activities in the presence of magnesium ions. We describe here that the minimal catalytic domain can catalyze a cross-ligation reaction between two kinds of substrates in trans. The cross-ligated product increased when the reaction temperature was decreased during the reaction from 37 degrees C to 4 degrees C. A two-stranded hairpin ribozyme, divided into two fragments between G45 and U46 in a hairpin loop, showed higher ligation activity than the nondivided ribozyme. The two stranded ribozyme also catalyzed an exchange reaction of the 3'-portion of the cleavage site. Images PMID:8441626

  6. Palladium-Catalyzed Arylation of Alkyl Sulfenate Anions.

    PubMed

    Jia, Tiezheng; Zhang, Mengnan; Jiang, Hui; Wang, Carol Y; Walsh, Patrick J

    2015-11-04

    A unique palladium-catalyzed arylation of alkyl sulfenate anions is introduced that affords aryl alkyl sulfoxides in high yields. Due to the base sensitivity of the starting sulfoxides, sulfenate anion intermediates, and alkyl aryl sulfoxide products, the use of a mild method to generate alkyl sulfenate anions was crucial to the success of this process. Thus, a fluoride triggered elimination strategy was employed with alkyl 2-(trimethylsilyl)ethyl sulfoxides to liberate the requisite alkyl sulfenate anion intermediates. In the presence of palladium catalysts with bulky monodentate phosphines (SPhos and Cy-CarPhos) and aryl bromides or chlorides, alkyl sulfenate anions were readily arylated. Moreover, the thermal fragmentation and the base promoted elimination of alkyl sulfoxides was overridden. The alkyl sulfenate anion arylation exhibited excellent chemoselectivity in the presence of functional groups, such as anilines and phenols, which are also known to undergo palladium catalyzed arylation reactions.

  7. Temperature dependence of the thrombin-catalyzed proteolysis of prothrombin.

    PubMed

    Shi, Fang; Winzor, Donald J; Jackson, Craig M

    2004-07-01

    Measurement of the temperature-dependence of thrombin-catalyzed cleavage of the Arg(155)-Ser(156) and Arg(284)-Thr(285) peptide bonds in prothrombin and prothrombin-derived substrates has yielded Arrhenius parameters that are far too large for classical mechanistic interpretation in terms of a simple hydrolytic reaction. Such a difference from the kinetic behavior exhibited in trypsin- and chymotrypsin-catalyzed proteolysis of peptide bonds is attributed to contributions by enzyme exosite interactions as well as enzyme conformational equilibria to the magnitudes of the experimentally determined Arrhenius parameters. Although the pre-exponential factor and the energy of activation deduced from the temperature-dependence of rate constants for proteolysis by thrombin cannot be accorded the usual mechanistic significance, their evaluation serves a valuable role by highlighting the existence of contributions other than those emanating from simple peptide hydrolysis to the kinetics of proteolysis by thrombin and presumably other enzymes of the blood coagulation system.

  8. Hairpin ribozyme-catalyzed ligation in water-alcohol solutions.

    PubMed

    Vlassov, Alexander V; Johnston, Brian H; Kazakov, Sergei A

    2005-12-01

    The hairpin ribozyme (HPR) is a naturally existing RNA that catalyzes site-specific RNA cleavage and ligation. At 37 degrees C and in the presence of divalent metal ions (M(2+)), the HPR efficiently cleaves RNA substrates in trans. Here, we show that the HPR can catalyze efficient M(2+)-independent ligation in trans in aqueous solutions containing any of several alcohols, including methanol, ethanol, and isopropanol, and millimolar concentrations of monovalent cations. Ligation proceeds most efficiently in 60% isopropanol at 37 degrees C, whereas the reverse (cleavage) reaction is negligible under these conditions. We suggest that dehydration of the RNA is the key factor promoting HPR activity in water- alcohol solutions. Alcohol-induced ribozyme ligation may have practical applications.

  9. Thermodynamics of Enzyme-Catalyzed Reactions: Part 4. Lyases

    NASA Astrophysics Data System (ADS)

    Goldberg, Robert N.; Tewari, Yadu B.

    1995-09-01

    Equilibrium constants and enthalpy changes for reactions catalyzed by the lyase class of enzymes have been compiled. For each reaction the following information is given: the reference for the data; the reaction studied; the name of the enzyme used and its Enzyme Commission number; the method of measurement; the conditions of measurement (temperature, pH, ionic strength, and the buffer(s) and cofactor(s) used); the data and an evaluation of it; and, sometimes, commentary on the data and on any corrections which have been applied to it or any calculations for which the data have been used. The data from 106 references have been examined and evaluated. Chemical Abstract Service registry numbers are given for the substances involved in these various reactions. There is a cross reference between the substances and the Enzyme Commission numbers of the enzymes used to catalyze the reactions in which the substances participate.

  10. Thermodynamics of Enzyme-Catalyzed Reactions: Part 2. Transferases

    NASA Astrophysics Data System (ADS)

    Goldberg, Robert N.; Tewari, Yadu B.

    1994-07-01

    Equilibrium constants and enthalpy changes for reactions catalyzed by the transferase class of enzymes have been compiled. For each reaction the following information is given: the reference for the data; the reaction studied; the name of the enzyme used and its Enzyme Commission number; the method of measurement; the conditions of measurement [temperature, pH, ionic strength, and the buffer(s) and cofactor(s) used]; the data and an evaluation of it; and, sometimes, commentary on the data and on any corrections which have been applied to it or any calculations for which the data have been used. The data from 285 references have been examined and evaluated. Chemical Abstract Service registry numbers are given for the substances involved in these various reactions. There is a cross reference between the substances and the Enzyme Commission numbers of the enzymes used to catalyze the reactions in which the substances participate.

  11. Thermodynamics of Enzyme-Catalyzed Reactions. Part 3. Hydrolases

    NASA Astrophysics Data System (ADS)

    Goldberg, Robert N.; Tewari, Yadu B.

    1994-11-01

    Equilibrium constants and enthalpy changes for reactions catalyzed by the hydrolase class of enzymes have been compiled. For each reaction the following information is given: The reference for the data; the reaction studied; the name of the enzyme used and its Enzyme Commission number; the method of measurement; the conditions of measurement [temperature, pH, ionic strength, and the buffer(s) and cofactor(s) used]; the data and an evaluation of it; and, sometimes, commentary on the data and on any corrections which have been applied to it or any calculations for which the data have been used. The data from 145 references have been examined and evaluated. Chemical Abstract Service registry numbers are given for the substances involved in these various reactions. There is a cross reference between the substances and the Enzyme Commission numbers of the enzymes used to catalyze the reactions in which the substances participate.

  12. Generalized rate equation for single-substrate enzyme catalyzed reactions.

    PubMed

    Kargi, Fikret

    2009-04-24

    The most widely used rate expression for single-substrate enzyme catalyzed reactions, namely the Michaelis-Menten kinetics is based upon the assumption that enzyme concentration is in excess of the substrate in the medium and the rate is mainly limited by the substrate concentration according to saturation kinetics. However, this is only a special case and the actual rate expression varies depending on the initial enzyme/substrate ratio (E(0)/S(0)). When the substrate concentration exceeds the enzyme concentration the limitation is due to low enzyme concentration and the rate increases with the enzyme concentration according to saturation kinetics. The maximum rate is obtained when the initial concentrations of the enzyme and the substrate are equal. A generalized rate equation was developed in this study and special cases were discussed for enzyme catalyzed reactions.

  13. Copper-Catalyzed Divergent Addition Reactions of Enoldiazoacetamides with Nitrones.

    PubMed

    Cheng, Qing-Qing; Yedoyan, Julietta; Arman, Hadi; Doyle, Michael P

    2016-01-13

    Catalyst-controlled divergent addition reactions of enoldiazoacetamides with nitrones have been developed. By using copper(I) tetrafluoroborate/bisoxazoline complex as the catalyst, a [3+3]-cycloaddition reaction was achieved with excellent yield and enantioselectivity under exceptionally mild conditions, which represents the first highly enantioselective base-metal-catalyzed vinylcarbene transformation. When the catalyst was changed to copper(I) triflate, Mannich addition products were formed in high yields with near exclusivity under otherwise identical conditions.

  14. Iron-Catalyzed gem-Specific Dimerization of Terminal Alkynes.

    PubMed

    Liang, Qiuming; Osten, Kimberly M; Song, Datong

    2017-03-13

    We report a gem-specific homo- and cross-dimerization of terminal alkynes catalyzed by a well-defined iron(II) complex containing Cp* and picolyl N-heterocyclic carbene (NHC) ligands, and featuring a piano-stool structure. This catalytic system requires no additives and is compatible with a broad range of substrates, including those with polar functional groups such as NH and OH.

  15. Pd-catalyzed nucleophilic fluorination of aryl bromides.

    PubMed

    Lee, Hong Geun; Milner, Phillip J; Buchwald, Stephen L

    2014-03-12

    On the basis of mechanism-driven reaction design, a Pd-catalyzed nucleophilic fluorination of aryl bromides and iodides has been developed. The method exhibits a broad substrate scope, especially with respect to nitrogen-containing heteroaryl bromides, and proceeds with minimal formation of the corresponding reduction products. A facilitated ligand modification process was shown to be critical to the success of the reaction.

  16. Pd-Catalyzed Nucleophilic Fluorination of Aryl Bromides

    PubMed Central

    2015-01-01

    On the basis of mechanism-driven reaction design, a Pd-catalyzed nucleophilic fluorination of aryl bromides and iodides has been developed. The method exhibits a broad substrate scope, especially with respect to nitrogen-containing heteroaryl bromides, and proceeds with minimal formation of the corresponding reduction products. A facilitated ligand modification process was shown to be critical to the success of the reaction. PMID:24559304

  17. Copper-catalyzed arylation of alkyl halides with arylaluminum reagents

    PubMed Central

    Shrestha, Bijay

    2015-01-01

    Summary We report a Cu-catalyzed coupling between triarylaluminum reagents and alkyl halides to form arylalkanes. The reaction proceeds in the presence of N,N,N’,N’-tetramethyl-o-phenylenediamine (NN-1) as a ligand in combination with CuI as a catalyst. This catalyst system enables the coupling of primary alkyl iodides and bromides with electron-neutral and electron-rich triarylaluminum reagents and affords the cross-coupled products in good to excellent yields. PMID:26734088

  18. Palladium-Catalyzed Synthesis of N-Aryl Carbamates

    PubMed Central

    Vinogradova, Ekaterina V.; Park, Nathaniel H.; Fors, Brett P.; Buchwald, Stephen L.

    2013-01-01

    An efficient synthesis of aryl carbamates was achieved by introducing alcohols into the reaction of palladium-catalyzed cross-coupling of ArX (X = Cl, OTf) with sodium cyanate. The use of aryl triflates as electrophilic components in this transformation allowed for an expanded substrate scope for direct synthesis of aryl isocyanates. This methodology provides direct access to major carbamate protecting groups, S-thiocarbamates, and diisocyanate precursors to polyurethane materials. PMID:23441814

  19. Biaryl Phosphine Ligands in Palladium-Catalyzed Amination

    PubMed Central

    Surry, David S.

    2012-01-01

    Palladium-catalyzed amination of aryl halides has undergone rapid development in the last 12 years. This has been largely driven by implementation of new classes of ligands. Biaryl phosphines have proven to provide especially active catalysts in this context. This review discusses the applications that these catalysts have found in C-N cross-coupling in heterocycle synthesis, pharmaceuticals, materials science and natural product synthesis. PMID:18663711

  20. Silver-Catalyzed C(sp(3))-H Chlorination.

    PubMed

    Ozawa, Jun; Kanai, Motomu

    2017-03-17

    A silver-catalyzed chlorination of benzylic, tertiary, and secondary C(sp(3))-H bonds was developed. The reaction proceeded with as low as 0.2 mol % catalyst loading at room temperature under air atmosphere with synthetically useful functional group compatibility. The regioselectivity and reactivity tendencies suggest that the chlorination proceeded through a radical pathway, but an intermediate alkylsilver species cannot be ruled out.

  1. Synthesis of Graphite Encapsulated Metal Nanoparticles and Metal Catalyzed Nanotubes

    NASA Technical Reports Server (NTRS)

    vanderWal, R. L.; Dravid, V. P.

    1999-01-01

    This work focuses on the growth and inception of graphite encapsulated metal nanoparticles and metal catalyzed nanotubes using combustion chemistry. Deciphering the inception and growth mechanism(s) for these unique nanostructures is essential for purposeful synthesis. Detailed knowledge of these mechanism(s) may yield insights into alternative synthesis pathways or provide data on unfavorable conditions. Production of these materials is highly desirable given many promising technological applications.

  2. Lactoperoxidase-catalyzed activation of carcinogenic aromatic and heterocyclic amines.

    PubMed

    Gorlewska-Roberts, Katarzyna M; Teitel, Candee H; Lay, Jackson O; Roberts, Dean W; Kadlubar, Fred F

    2004-12-01

    Lactoperoxidase, an enzyme secreted from the human mammary gland, plays a host defensive role through antimicrobial activity. It has been implicated in mutagenic and carcinogenic activation in the human mammary gland. The potential role of heterocyclic and aromatic amines in the etiology of breast cancer led us to examination of the lactoperoxidase-catalyzed activation of the most commonly studied arylamine carcinogens: 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP), benzidine, 4-aminobiphenyl (ABP), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx). In vitro activation was performed with lactoperoxidase (partially purified from bovine milk or human milk) in the presence of hydrogen peroxide and calf thymus DNA. Products formed during enzymatic activation were monitored by HPLC with ultraviolet and radiometric detection. Two of these products were characterized as hydrazo and azo derivatives by means of mass spectrometry. The DNA binding level of 3H- and 14C-radiolabeled amines after peroxidase-catalyzed activation was dependent on the hydrogen peroxide concentration, and the highest levels of carcinogen binding to DNA were observed at 100 microM H2O2. Carcinogen activation and the level of binding to DNA were in the order of benzidine > ABP > IQ > MeIQx > PhIP. One of the ABP adducts was identified, and the level at which it is formed was estimated to be six adducts/10(5) nucleotides. The susceptibility of aromatic and heterocyclic amines for lactoperoxidase-catalyzed activation and the binding levels of activated products to DNA suggest a potential role of lactoperoxidase-catalyzed activation of carcinogens in the etiology of breast cancer.

  3. Asymmetric Arylation of Imines Catalyzed by Heterogeneous Chiral Rhodium Nanoparticles.

    PubMed

    Yasukawa, Tomohiro; Kuremoto, Tatsuya; Miyamura, Hiroyuki; Kobayashi, Shu̅

    2016-06-03

    Asymmetric arylation of aldimines catalyzed by heterogeneous chiral rhodium nanoparticles has been developed. The reaction proceeded in aqueous media without significant decomposition of the imines by hydrolysis to afford chiral (diarylmethyl)amines in high yields with outstanding enantioselectivities. This catalyst system exhibited the highest turnover number (700) in heterogeneous catalysts reported to date for these reactions. The reusability of the catalyst was also demonstrated.

  4. A Simple Strategy for Glycosyltransferase-Catalyzed Aminosugar Nucleotide Synthesis

    PubMed Central

    Zhang, Jianjun; Singh, Shanteri; Hughes, Ryan R.; Zhou, Maoquan; Sunkara, Manjula; Morris, Andrew J.; Thorson, Jon S.

    2014-01-01

    A set of 2-chloro-4-nitrophenyl glucosamino/xylosaminosides were synthesized and assessed as potential substrates in the context of glycosyltransferase-catalyzed formation of the corresponding UDP/TDP-α-D-glucosamino-/xylosaminosugars and single vessel transglycosylation reactions with a model acceptor. This study highlights a robust platform for aminosugar nucleotide synthesis and reveals OleD Loki as a proficient catalyst for U/TDP-aminosugar synthesis and utilization. PMID:24677528

  5. A simple strategy for glycosyltransferase-catalyzed aminosugar nucleotide synthesis.

    PubMed

    Zhang, Jianjun; Singh, Shanteri; Hughes, Ryan R; Zhou, Maoquan; Sunkara, Manjula; Morris, Andrew J; Thorson, Jon S

    2014-03-21

    A set of 2-chloro-4-nitrophenyl glucosamino-/xylosaminosides were synthesized and assessed as potential substrates in the context of glycosyltransferase-catalyzed formation of the corresponding UDP/TDP-α-D-glucosamino-/xylosaminosugars and in single-vessel model transglycosylation reactions. This study highlights a robust platform for aminosugar nucleotide synthesis and reveals OleD Loki to be a proficient catalyst for U/TDP-aminosugar synthesis and utilization

  6. Silver-Catalyzed Decarboxylative Bromination of Aliphatic Carboxylic Acids.

    PubMed

    Tan, Xinqiang; Song, Tao; Wang, Zhentao; Chen, He; Cui, Lei; Li, Chaozhong

    2017-03-13

    The silver-catalyzed Hunsdiecker bromination of aliphatic carboxylic acids is described. With Ag(Phen)2OTf as the catalyst and dibromoisocyanuric acid as the brominating agent, various aliphatic carboxylic acids underwent decarboxylative bromination to provide the corresponding alkyl bromides under mild conditions. This method not only is efficient and general but also enjoys wide functional group compatibility. An oxidative radical mechanism involving Ag(II) intermediates is proposed.

  7. The gravitino-stau scenario after catalyzed big bang nucleosynthesis

    SciTech Connect

    Kersten, Joern; Schmidt-Hoberg, Kai E-mail: kai.schmidt-hoberg@ph.tum.de

    2008-01-15

    We consider the impact of catalyzed big bang nucleosynthesis on theories with a gravitino lightest superparticle and a charged slepton next-to-lightest superparticle. In models where the gravitino to gaugino mass ratio is bounded from below, such as gaugino-mediated supersymmetry breaking, we derive a lower bound on the gaugino mass parameter m{sub 1/2}. As a concrete example, we determine the parameter space of gaugino mediation that is compatible with all cosmological constraints.

  8. Ligand-Controlled Regiodivergent Copper-Catalyzed Alkylboration of Alkenes.

    PubMed

    Su, Wei; Gong, Tian-Jun; Lu, Xi; Xu, Meng-Yu; Yu, Chu-Guo; Xu, Zheng-Yang; Yu, Hai-Zhu; Xiao, Bin; Fu, Yao

    2015-10-26

    A novel copper-catalyzed regiodivergent alkylboration of alkenes with bis(pinacolato)diboron and alkyl halides has been developed. The regioselectivity of the alkylboration was controlled by subtle differences in the ligand structure. The reaction thus enables the practical, regiodivergent synthesis of two different alkyl boronic esters with complex structures from a single alkene. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Enantio- and Regioselective CuH-Catalyzed Hydroamination of Alkenes

    PubMed Central

    Zhu, Shaolin; Niljianskul, Nootaree; Buchwald, Stephen L.

    2013-01-01

    A highly enantio- and regioselective copper-catalyzed hydroamination reaction of alkenes has been developed using diethoxy(methyl)silane (DEMS) and esters of hydroxylamines. The process tolerates a wide variety of substituted styrenes, including trans-, cis-, and β,β-disubstituted styrenes to yield α–branched amines. In addition, aliphatic alkenes coupled to generate exclusively the anti-Markovnikov hydroamination products. PMID:24106781

  10. Ru-catalyzed stereoselective addition of imides to alkynes.

    PubMed

    Goossen, Lukas J; Blanchot, Mathieu; Brinkmann, Claus; Goossen, Käthe; Karch, Ralph; Rivas-Nass, Andreas

    2006-12-08

    A catalyst system formed in situ from bis(2-methylallyl)cycloocta-1,5-dieneruthenium(II) ((cod)Ru[met]2), a phosphine, and scandium(III) trifluoromethanesulfonate (Sc(OTf)3) was found to efficiently catalyze the anti-Markovnikov addition of imides to terminal alkynes, allowing mild and atom-economic synthesis of enimides. Depending on the phosphine employed, both the (E)- and the (Z)-isomer can be accessed stereoselectively.

  11. Cobalt-catalyzed formation of symmetrical biaryls and its mechanism.

    PubMed

    Moncomble, Aurélien; Le Floch, Pascal; Gosmini, Corinne

    2009-01-01

    Effective devotion: An efficient cobalt-catalyzed method devoted to the formation of symmetrical biaryls is described avoiding the preparation of organometallic reagents. Various aromatic halides functionalized by a variety of reactive group reagents are employed. Preliminary DFT calculations have shown that the involvement of a Co(I)/Co(III) couple is realistic at least in the case of 1,3-diazadienes as ligands (FG = functional group).

  12. Copper-catalyzed trifluoromethylation of trisubstituted allylic and homoallylic alcohols.

    PubMed

    Lei, Jian; Liu, Xiaowu; Zhang, Shaolin; Jiang, Shuang; Huang, Minhao; Wu, Xiaoxing; Zhu, Qiang

    2015-04-27

    An efficient copper-catalyzed trifluoromethylation of trisubstituted allylic and homoallylic alcohols with Togni's reagent has been developed. This strategy, accompanied by a double-bond migration, leads to various branched CF3-substituted alcohols by using readily available trisubstituted cyclic/acyclic alcohols as substrates. Moreover, for alcohols in which β-H elimination is prohibited, CF3-containing oxetanes are isolated as the sole product.

  13. Gold(I)-Catalyzed Enantioselective Ring Expansion of Allenylcyclopropanols

    PubMed Central

    Kleinbeck, Florian; Toste, F. Dean

    2009-01-01

    The asymmetric gold(I)-catalyzed ring expansion of 1-allenylcyclopropanols is described. The method provides synthetically valuable cyclobutanones with a vinyl-substituted quaternary stereogenic center in high enantioselectivities and yields. The method shows a broad substrate scope, tolerating protected alcohols and amines, alkenes, unsaturated esters and acetals. The reaction is easily adjustable to large scale synthesis, leading to product formation without significant loss of selectivity or yield with only 0.5 mol% catalyst loading. PMID:19530649

  14. Asymmetric Palladium-Catalyzed Directed Intermolecular Fluoroarylation of Styrenes

    PubMed Central

    2015-01-01

    A mild catalytic asymmetric direct fluoro-arylation of styrenes has been developed. The palladium-catalyzed three-component coupling of Selectfluor, a styrene and a boronic acid, provides chiral monofluorinated compounds in good yield and in high enantiomeric excess. A mechanism proceeding through a Pd(IV)-fluoride intermediate is proposed for the transformation and synthesis of an sp3 C–F bond. PMID:24617344

  15. Enzyme catalyzed biochemical production in a polydimethylsiloxane microreactor

    NASA Astrophysics Data System (ADS)

    Dickey, Cynthia K.; Elmore, Bill B.; Jones, Francis

    2000-08-01

    Study of an aqueous-phase reaction in an enzyme- catalyzedpolydimethylsiloxane (PDMS) microreactor is underway. In the present work, urease - an enzyme that catalyzes urea to ammonia and carbon dioxide has been immobilized within open microchannels of 450 micrometers (micrometers ) in diameter or less. Microchannels are templated within PDMS. Preliminary results demonstrate the proof of concept for conversion biochemicals via a PDMS-based microreactor system.

  16. N-heterocyclic carbene-catalyzed rearrangements of vinyl sulfones.

    PubMed

    Atienza, Roxanne L; Roth, Howard S; Scheidt, Karl A

    2011-01-01

    N-heterocyclic carbenes catalyze the rearrangement of 1,1-bis(arylsulfonyl)ethylene to the corresponding trans-1,2-bis(phenylsulfonyl) under mild conditions. Tandem rearrangement/cycloadditions have been developed to capitalize on this new process and generate highly substituted isoxazolines and additional heterocyclic compounds. Preliminary mechanistic studies support a new conjugate addition/Umpolung process involving the ejection and subsequent unusual re-addition of a sulfinate ion.

  17. Anisotropic Morphological Changes in Goethite during Fe(2+)-Catalyzed Recrystallization.

    PubMed

    Joshi, Prachi; Gorski, Christopher A

    2016-07-19

    When goethite is exposed to aqueous Fe(2+), rapid and extensive Fe atom exchange can occur between solid-phase Fe(3+) and aqueous Fe(2+) in a process referred to as Fe(2+)-catalyzed recrystallization. This process can lead to the structural incorporation or release of trace elements, which has important implications for contaminant remediation and nutrient biogeochemical cycling. Prior work found that the process did not cause major changes to the goethite structure or morphology. Here, we further investigated if and how goethite morphology and aggregation behavior changed temporally during Fe(2+)-catalyzed recrystallization. On the basis of existing literature, we hypothesized that Fe(2+)-catalyzed recrystallization of goethite would not result in changes to individual particle morphology or interparticle interactions. To test this, we reacted nanoparticulate goethite with aqueous Fe(2+) at pH 7.5 over 30 days and used transmission electron microscopy (TEM), cryogenic TEM, and (55)Fe as an isotope tracer to observe changes in particle dimensions, aggregation, and isotopic composition over time. Over the course of 30 days, the goethite particles substantially recrystallized, and the particle dimensions changed anisotropically, resulting in a preferential increase in the mean particle width. The temporal changes in goethite morphology could not be completely explained by a single mineral-transformation mechanism but rather indicated that multiple transformation mechanisms occurred concurrently. Collectively, these results demonstrate that the morphology of goethite nanoparticles does change during recrystallization, which is an important step toward identifying the driving force(s) of recrystallization.

  18. Enzyme catalyzed optofluidic biolaser for sensitive ion concentration detection

    NASA Astrophysics Data System (ADS)

    Gong, Chaoyang; Gong, Yuan; Oo, Maung Kyaw Khaing; Wu, Yu; Rao, Yunjiang; Fan, Xudong

    2016-12-01

    The enzyme horseradish peroxidase (HRP) has been extensively used in biochemistry for its ability to amplify a weak signal. By using HRP catalyzed substrate as the gain medium, we demonstrate sensitive ion concentration detection based on the optofluidic laser. The enzyme catalyzed reaction occurs in bulk solution inside a Fabry-Perot laser cavity, where the colorless, non-fluorescent 10-Acetyl-3,7-dihydroxyphenoxazine (ADHP) substrate is oxidized to produce highly fluorescent resorufin. Laser emission is achieved when pumped with the second harmonic wave of a Q-switched YAG laser. Further, we use sulfide anion (S2-) as an example to investigate the sensing performance of enzyme catalyzed optofluidic laser. The laser onset time difference between the sample to be tested and the reference is set to be the sensing output. Thanks to the amplification effects of both the enzymatic reaction and laser emission, we achieve a detection limit of 10 nM and a dynamic range of 3 orders of magnitude.

  19. Protection of Wood from Microorganisms by Laccase-Catalyzed Iodination

    PubMed Central

    Engel, J.; Thöny-Meyer, L.; Schwarze, F. W. M. R.; Ihssen, J.

    2012-01-01

    In the present work, Norway spruce wood (Picea abies L.) was reacted with a commercial Trametes versicolor laccase in the presence of potassium iodide salt or the phenolic compounds thymol and isoeugenol to impart an antimicrobial property to the wood surface. In order to assess the efficacy of the wood treatment, a leaching of the iodinated and polymerized wood and two biotests including bacteria, a yeast, blue stain fungi, and wood decay fungi were performed. After laccase-catalyzed oxidation of the phenols, the antimicrobial effect was significantly reduced. In contrast, the enzymatic oxidation of iodide (I−) to iodine (I2) in the presence of wood led to an enhanced resistance of the wood surface against all microorganisms, even after exposure to leaching. The efficiency of the enzymatic wood iodination was comparable to that of a chemical wood preservative, VP 7/260a. The modification of the lignocellulose by the laccase-catalyzed iodination was assessed by the Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) technique. The intensities of the selected lignin-associated bands and carbohydrate reference bands were analyzed, and the results indicated a structural change in the lignin matrix. The results suggest that the laccase-catalyzed iodination of the wood surface presents an efficient and ecofriendly method for wood protection. PMID:22865075

  20. Aluminum-catalyzed silicon nanowires: Growth methods, properties, and applications

    NASA Astrophysics Data System (ADS)

    Hainey, Mel F.; Redwing, Joan M.

    2016-12-01

    Metal-mediated vapor-liquid-solid (VLS) growth is a promising approach for the fabrication of silicon nanowires, although residual metal incorporation into the nanowires during growth can adversely impact electronic properties particularly when metals such as gold and copper are utilized. Aluminum, which acts as a shallow acceptor in silicon, is therefore of significant interest for the growth of p-type silicon nanowires but has presented challenges due to its propensity for oxidation. This paper summarizes the key aspects of aluminum-catalyzed nanowire growth along with wire properties and device results. In the first section, aluminum-catalyzed nanowire growth is discussed with a specific emphasis on methods to mitigate aluminum oxide formation. Next, the influence of growth parameters such as growth temperature, precursor partial pressure, and hydrogen partial pressure on nanowire morphology is discussed, followed by a brief review of the growth of templated and patterned arrays of nanowires. Aluminum incorporation into the nanowires is then discussed in detail, including measurements of the aluminum concentration within wires using atom probe tomography and assessment of electrical properties by four point resistance measurements. Finally, the use of aluminum-catalyzed VLS growth for device fabrication is reviewed including results on single-wire radial p-n junction solar cells and planar solar cells fabricated with nanowire/nanopyramid texturing.

  1. Asymmetric Stetter reactions catalyzed by thiamine diphosphate-dependent enzymes.

    PubMed

    Kasparyan, Elena; Richter, Michael; Dresen, Carola; Walter, Lydia S; Fuchs, Georg; Leeper, Finian J; Wacker, Tobias; Andrade, Susana L A; Kolter, Geraldine; Pohl, Martina; Müller, Michael

    2014-12-01

    The intermolecular asymmetric Stetter reaction is an almost unexplored transformation for biocatalysts. Previously reported thiamine diphosphate (ThDP)-dependent PigD from Serratia marcescens is the first enzyme identified to catalyze the Stetter reaction of α,β-unsaturated ketones (Michael acceptor substrates) and α-keto acids. PigD is involved in the biosynthesis of the potent cytotoxic agent prodigiosin. Here, we describe the investigation of two new ThDP-dependent enzymes, SeAAS from Saccharopolyspora erythraea and HapD from Hahella chejuensis. Both show a high degree of homology to the amino acid sequence of PigD (39 and 51 %, respectively). The new enzymes were heterologously overproduced in Escherichia coli, and the yield of soluble protein was enhanced by co-expression of the chaperone genes groEL/ES. SeAAS and HapD catalyze intermolecular Stetter reactions in vitro with high enantioselectivity. The enzymes possess a characteristic substrate range with respect to Michael acceptor substrates. This provides support for a new type of ThDP-dependent enzymatic activity, which is abundant in various species and not restricted to prodigiosin biosynthesis in different strains. Moreover, PigD, SeAAS, and HapD are also able to catalyze asymmetric carbon-carbon bond formation reactions of aldehydes and α-keto acids, resulting in 2-hydroxy ketones.

  2. Protection of wood from microorganisms by laccase-catalyzed iodination.

    PubMed

    Schubert, M; Engel, J; Thöny-Meyer, L; Schwarze, F W M R; Ihssen, J

    2012-10-01

    In the present work, Norway spruce wood (Picea abies L.) was reacted with a commercial Trametes versicolor laccase in the presence of potassium iodide salt or the phenolic compounds thymol and isoeugenol to impart an antimicrobial property to the wood surface. In order to assess the efficacy of the wood treatment, a leaching of the iodinated and polymerized wood and two biotests including bacteria, a yeast, blue stain fungi, and wood decay fungi were performed. After laccase-catalyzed oxidation of the phenols, the antimicrobial effect was significantly reduced. In contrast, the enzymatic oxidation of iodide (I(-)) to iodine (I(2)) in the presence of wood led to an enhanced resistance of the wood surface against all microorganisms, even after exposure to leaching. The efficiency of the enzymatic wood iodination was comparable to that of a chemical wood preservative, VP 7/260a. The modification of the lignocellulose by the laccase-catalyzed iodination was assessed by the Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) technique. The intensities of the selected lignin-associated bands and carbohydrate reference bands were analyzed, and the results indicated a structural change in the lignin matrix. The results suggest that the laccase-catalyzed iodination of the wood surface presents an efficient and ecofriendly method for wood protection.

  3. Aluminum-catalyzed silicon nanowires: Growth methods, properties, and applications

    SciTech Connect

    Hainey, Mel F.; Redwing, Joan M.

    2016-12-15

    Metal-mediated vapor-liquid-solid (VLS) growth is a promising approach for the fabrication of silicon nanowires, although residual metal incorporation into the nanowires during growth can adversely impact electronic properties particularly when metals such as gold and copper are utilized. Aluminum, which acts as a shallow acceptor in silicon, is therefore of significant interest for the growth of p-type silicon nanowires but has presented challenges due to its propensity for oxidation. This paper summarizes the key aspects of aluminum-catalyzed nanowire growth along with wire properties and device results. In the first section, aluminum-catalyzed nanowire growth is discussed with a specific emphasis on methods to mitigate aluminum oxide formation. Next, the influence of growth parameters such as growth temperature, precursor partial pressure, and hydrogen partial pressure on nanowire morphology is discussed, followed by a brief review of the growth of templated and patterned arrays of nanowires. Aluminum incorporation into the nanowires is then discussed in detail, including measurements of the aluminum concentration within wires using atom probe tomography and assessment of electrical properties by four point resistance measurements. Finally, the use of aluminum-catalyzed VLS growth for device fabrication is reviewed including results on single-wire radial p-n junction solar cells and planar solar cells fabricated with nanowire/nanopyramid texturing.

  4. Enzyme-catalyzed biocathode in a photoelectrochemical biofuel cell

    NASA Astrophysics Data System (ADS)

    Yang, Jing; Hu, Donghua; Zhang, Xiaohuan; Wang, Kunqi; Wang, Bin; Sun, Bo; Qiu, Zhidong

    2014-12-01

    A novel double-enzyme photoelectrochemical biofuel cell (PEBFC) has been developed by taking glucose dehydrogenase (GDH) and horseradish peroxidase (HRP) as the enzyme of the photoanode and biocathode to catalyze the oxidation of glucose and the reduction of oxygen. A H2-mesoporphyrin IX is used as a dye for a TiO2 film electrode to fabricate a photoanode. The horseradish peroxidase (HRP) is immobilized on a glassy carbon (GC) electrode to construct a biocathode which is used to catalyze the reduction of oxygen in the PEBFC for the first time. The biocathode exhibits excellent electrocatalytic activity in the presence of O2. The performances of the PEBFC are obtained by current-voltage and power-voltage curves. The short-circuit current density (Isc), the open-circuit voltage (Voc), maximum power density (Pmax), fill factor (FF) and energy conversion efficiency (η) are 439 μA cm-2, 678 mV, 79 μW cm-2, 0.39 and 0.016%, respectively, and the incident photon-to-collected electron conversion efficiency (IPCE) is 32% at 350 nm. The Isc is higher than that of the PEBFC with Pt cathode, and the Voc is higher than that of the dye-sensitized solar cell or the enzyme-catalyzed biofuel cell operating individually, which demonstrates that the HRP is an efficient catalyst for the biocathode in the PEBFC.

  5. Stau-catalyzed big-bang nucleosynthesis reactions

    SciTech Connect

    Kamimura, Masayasu; Kino, Yasushi; Hiyama, Emiko

    2010-06-01

    We study the new type of big-bang nucleosynthesis (BBN) reactions that are catalyzed by a hypothetical long-lived negatively charged, massive leptonic particle (called X{sup -}) such as the supersymmetric (SUSY) particle stau, the scalar partner of the tau lepton. It is known that if the X{sup -} particle has a lifetime of tau{sub X} > or approx. 10{sup 3} s, it can capture a light element previously synthesized in standard BBN and form a Coulombic bound state and induces various types of reactions in which X{sup -} acts as a catalyst. Some of these X{sup -} catalyzed reactions have significantly large cross sections so that the inclusion of the reactions into the BBN network calculation can markedly change the abundances of some elements. We use a high-accuracy three-body calculation method developed by the authors and provide precise cross sections and rates of these catalyzed BBN reactions for use in the BBN network calculation.

  6. Acid-Catalyzed Preparation of Biodiesel from Waste Vegetable Oil: An Experiment for the Undergraduate Organic Chemistry Laboratory

    ERIC Educational Resources Information Center

    Bladt, Don; Murray, Steve; Gitch, Brittany; Trout, Haylee; Liberko, Charles

    2011-01-01

    This undergraduate organic laboratory exercise involves the sulfuric acid-catalyzed conversion of waste vegetable oil into biodiesel. The acid-catalyzed method, although inherently slower than the base-catalyzed methods, does not suffer from the loss of product or the creation of emulsion producing soap that plagues the base-catalyzed methods when…

  7. Acid-Catalyzed Preparation of Biodiesel from Waste Vegetable Oil: An Experiment for the Undergraduate Organic Chemistry Laboratory

    ERIC Educational Resources Information Center

    Bladt, Don; Murray, Steve; Gitch, Brittany; Trout, Haylee; Liberko, Charles

    2011-01-01

    This undergraduate organic laboratory exercise involves the sulfuric acid-catalyzed conversion of waste vegetable oil into biodiesel. The acid-catalyzed method, although inherently slower than the base-catalyzed methods, does not suffer from the loss of product or the creation of emulsion producing soap that plagues the base-catalyzed methods when…

  8. Synthetic Study of Dragmacidin E: Construction of the Core Structure Using Pd-Catalyzed Cascade Cyclization and Rh-Catalyzed Aminoacetoxylation.

    PubMed

    Inoue, Naoya; Nakano, Shun-Ichi; Harada, Shingo; Hamada, Yasumasa; Nemoto, Tetsuhiro

    2017-03-03

    We developed a novel synthetic method of the core structure of dragmacidin E bearing a 7-membered ring-fused bis(indolyl)pyrazinone skeleton. Formation of the 7-membered ring-fused tricyclic indole skeleton was accomplished using a palladium-catalyzed Heck insertion-allylic amination cascade. Vicinal difunctionalization of the 7-membered ring was realized via a rhodium-catalyzed aminoacetoxylation.

  9. Efficient and selective synthesis of 6,7-Dehydrostipiamide via Zr-catalyzed asymmetric carboalumination and Pd-catalyzed cross-coupling of organozincs.

    PubMed

    Zeng, Xingzhong; Zeng, Fanxing; Negishi, Ei-ichi

    2004-09-16

    [structure: see text] 6,7-Dehydrostipiamide has been synthesized in 23% yield in 15 steps in the longest linear sequence through the application of the Zr-catalyzed asymmetric carboalumination and the Pd-catalyzed organozinc cross-coupling in addition to the Brown crotylboration, the Corey-Peterson olefination, and the Corey-Fuchs reaction for carbon-carbon bond formation.

  10. Asymmetric synthesis of dihydropyranones from ynones by sequential copper(I)-catalyzed direct aldol and silver(I)-catalyzed oxy-Michael reactions.

    PubMed

    Shi, Shi-Liang; Kanai, Motomu; Shibasaki, Masakatsu

    2012-04-16

    Ynones as diene surrogates: the asymmetric synthesis of enantiomerically enriched substituted dihydropyranones is described. The products are obtained in two steps by a copper(I)-catalyzed direct aldol reaction of ynones followed by a silver-catalyzed oxy-Michael reaction. This easy method is compatible with both aromatic and aliphatic substrates, and provides excellent chemoselectivity under mild reaction conditions.

  11. Ammonia and hydrazine. Transition-metal-catalyzed hydroamination and metal-free catalyzed functionalization

    SciTech Connect

    Bertrand, Guy

    2012-06-29

    high temperatures and long reaction times. To address this issue, we have developed several new families of carbon- and boron-based ligands, which are even better donors. The corresponding metal complexes (particularly gold, rhodium, iridium, and ruthenium) of all these species will be tested in the Markovnikov and anti-Markovnikov hydroamination of alkynes, allenes, and also alkenes with ammonia and hydrazine. We will also develop metal-free catalytic processes for the functionalization of ammonia and hydrazine. By possessing both a lone pair of electrons and an accessible vacant orbital, singlet carbenes resemble and can mimic the chemical behavior of transition metals. Our preliminary results demonstrate that specially designed carbenes can split the N–H bond of ammonia by an initial nucleophilic activation that prevents the formation of Lewis acid-base adducts, which is the major hurdle for the transition metal catalyzed functionalization of NH3. The use of purely organic compounds as catalysts will eliminate the major drawbacks of transition-metal-catalysis technology, which are the excessive cost of metal complexes (metal + ligands) and in many cases the toxicity of the metal.

  12. Iridium-Catalyzed Asymmetric Hydrogenation of Unsaturated Carboxylic Acids.

    PubMed

    Zhu, Shou-Fei; Zhou, Qi-Lin

    2017-04-04

    Chiral carboxylic acid moieties are widely found in pharmaceuticals, agrochemicals, flavors, fragrances, and health supplements. Although they can be synthesized straightforwardly by transition-metal-catalyzed enantioselective hydrogenation of unsaturated carboxylic acids, because the existing chiral catalysts have various disadvantages, the development of new chiral catalysts with high activity and enantioselectivity is an important, long-standing challenge. Ruthenium complexes with chiral diphosphine ligands and rhodium complexes with chiral monodentate or bidentate phosphorus ligands have been the predominant catalysts for asymmetric hydrogenation of unsaturated acids. However, the efficiency of these catalysts is highly substrate-dependent, and most of the reported catalysts require a high loading, high hydrogen pressure, or long reaction time for satisfactory results. Our recent studies have revealed that chiral iridium complexes with chiral spiro-phosphine-oxazoline ligands and chiral spiro-phosphine-benzylamine ligands exhibit excellent activity and enantioselectivity in the hydrogenation of α,β-unsaturated carboxylic acids, including α,β-disubstituted acrylic acids, trisubstituted acrylic acids, α-substituted acrylic acids, and heterocyclic α,β-unsaturated acids. On the basis of an understanding of the role of the carboxy group in iridium-catalyzed asymmetric hydrogenation reactions, we developed a carboxy-group-directed strategy for asymmetric hydrogenation of olefins. Using this strategy, we hydrogenated several challenging olefin substrates, such as β,γ-unsaturated carboxylic acids, 1,1-diarylethenes, 1,1-dialkylethenes, and 1-alkyl styrenes in high yield and with excellent enantioselectivity. All these iridium-catalyzed asymmetric hydrogenation reactions feature high turnover numbers (up to 10000) and turnover frequencies (up to 6000 h(-1)), excellent enantioselectivities (greater than 95% ee with few exceptions), low hydrogen pressure (<12 atm

  13. Energy harvesting by implantable abiotically catalyzed glucose fuel cells

    NASA Astrophysics Data System (ADS)

    Kerzenmacher, S.; Ducrée, J.; Zengerle, R.; von Stetten, F.

    Implantable glucose fuel cells are a promising approach to realize an autonomous energy supply for medical implants that solely relies on the electrochemical reaction of oxygen and glucose. Key advantage over conventional batteries is the abundant availability of both reactants in body fluids, rendering the need for regular replacement or external recharging mechanisms obsolete. Implantable glucose fuel cells, based on abiotic catalysts such as noble metals and activated carbon, have already been developed as power supply for cardiac pacemakers in the late-1960s. Whereas, in vitro and preliminary in vivo studies demonstrated their long-term stability, the performance of these fuel cells is limited to the μW-range. Consequently, no further developments have been reported since high-capacity lithium iodine batteries for cardiac pacemakers became available in the mid-1970s. In recent years research has been focused on enzymatically catalyzed glucose fuel cells. They offer higher power densities than their abiotically catalyzed counterparts, but the limited enzyme stability impedes long-term application. In this context, the trend towards increasingly energy-efficient low power MEMS (micro-electro-mechanical systems) implants has revived the interest in abiotic catalysts as a long-term stable alternative. This review covers the state-of-the-art in implantable abiotically catalyzed glucose fuel cells and their development since the 1960s. Different embodiment concepts are presented and the historical achievements of academic and industrial research groups are critically reviewed. Special regard is given to the applicability of the concept as sustainable micro-power generator for implantable devices.

  14. Molecular mechanism of Ca(2+)-catalyzed fusion of phospholipid micelles.

    PubMed

    Tsai, Hui-Hsu Gavin; Juang, Wei-Fu; Chang, Che-Ming; Hou, Tsai-Yi; Lee, Jian-Bin

    2013-11-01

    Although membrane fusion plays key roles in intracellular trafficking, neurotransmitter release, and viral infection, its underlying molecular mechanism and its energy landscape are not well understood. In this study, we employed all-atom molecular dynamics simulations to investigate the fusion mechanism, catalyzed by Ca(2+) ions, of two highly hydrated 1-palmitoyl-2-oleoyl-sn-3-phosphoethanolamine (POPE) micelles. This simulation system mimics the small contact zone between two large vesicles at which the fusion is initiated. Our simulations revealed that Ca(2+) ions are capable of catalyzing the fusion of POPE micelles; in contrast, we did not observe close contact of the two micelles in the presence of only Na(+) or Mg(2+) ions. Determining the free energy landscape of fusion allowed us to characterize the underlying molecular mechanism. The Ca(2+) ions play a key role in catalyzing the micelle fusion in three aspects: creating a more-hydrophobic surface on the micelles, binding two micelles together, and enhancing the formation of the pre-stalk state. In contrast, Na(+) or Mg(2+) ions have relatively limited effects. Effective fusion proceeds through sequential formation of pre-stalk, stalk, hemifused-like, and fused states. The pre-stalk state is the state featuring lipid tails exposed to the inter-micellar space; its formation is the rate-limiting step. The stalk state is the state where a localized hydrophobic core is formed connecting two micelles; its formation occurs in conjunction with water expulsion from the inter-micellar space. This study provides insight into the molecular mechanism of fusion from the points of view of energetics, structure, and dynamics. © 2013 Elsevier B.V. All rights reserved.

  15. A SABATH Methyltransferase from the moss Physcomitrella patens catalyzes

    SciTech Connect

    Zhao, Nan; Ferrer, Jean-Luc; Moon, Hong S; Kapteyn, Jeremy; Zhuang, Xiaofeng; Hasebe, Mitsuyasu; Stewart, Neal C.; Gang, David R.; Chen, Feng

    2012-01-01

    Known SABATH methyltransferases, all of which were identified from seed plants, catalyze methylation of either the carboxyl group of a variety of low molecular weight metabolites or the nitrogen moiety of precursors of caffeine. In this study, the SABATH family from the bryophyte Physcomitrella patens was identified and characterized. Four SABATH-like sequences (PpSABATH1, PpSABATH2, PpSABATH3, and PpSABATH4) were identified from the P. patens genome. Only PpSABATH1 and PpSABATH2 showed expression in the leafy gametophyte of P. patens. Full-length cDNAs of PpSABATH1 and PpSABATH2 were cloned and expressed in soluble form in Escherichia coli. Recombinant PpSABATH1 and PpSABATH2 were tested for methyltransferase activity with a total of 75 compounds. While showing no activity with carboxylic acids or nitrogen-containing compounds, PpSABATH1 displayed methyltransferase activity with a number of thiols. PpSABATH2 did not show activity with any of the compounds tested. Among the thiols analyzed, PpSABATH1 showed the highest level of activity with thiobenzoic acid with an apparent Km value of 95.5 lM, which is comparable to those of known SABATHs. Using thiobenzoic acid as substrate, GC MS analysis indicated that the methylation catalyzed by PpSABATH1 is on the sulfur atom. The mechanism for S-methylation of thiols catalyzed by PpSABATH1 was partially revealed by homology-based structural modeling. The expression of PpSABATH1 was induced by the treatment of thiobenzoic acid. Further transgenic studies showed that tobacco plants overexpressing PpSABATH1 exhibited enhanced tolerance to thiobenzoic acid, suggesting that PpSABATH1 have a role in the detoxification of xenobiotic thiols.

  16. [Novel L-amino acid ligases catalyzing oligopeptide synthesis].

    PubMed

    Kino, Kuniki

    2010-11-01

    L-Amino acid ligase (EC 6.3.2.28) is a microbial enzyme catalyzing formation of an alpha-peptide bond from unprotected L-amino acids in an ATP-dependent manner. The YwfE protein from Bacillus subtilis 168 was the first reported L-amino acid ligase, and it synthesizes various dipeptides. Thereafter, several L-amino acid ligases were newly obtained by in silico analysis using the ATP-grasp motif. But these L-amino acid ligases synthesize only dipeptide and no longer peptide. A novel L-amino acid ligase capable of catalyzing oligopeptide synthesis is required to increase the variety of peptides. We have previously found a new member of L-amino acid ligase, RizA, from B. subtilis NBRC3134, a microorganism that produces the peptide-antibiotic rhizocticin. We newly found that a gene at approximately 9 kbp upstream of rizA encoded a novel L-amino acid ligase RizB. Recombinant RizB synthesized homo-oligomers of branched-chain amino acids consisting of 2 to 5 amino acids, and also synthesized various heteropeptides. RizB is the first reported L-amino acid ligase that catalyzes oligopeptide synthesis. In addition, we obtained L-amino acid ligases showing oligopeptide synthesis activities by in silico analysis using BLAST, which is a set of similarity search programs. These L-amino acid ligases showed low similarity in amino acid sequence, but commonly used branched-chain amino acids, such as RizB, as substrates. Furthermore, the spr0969 protein of Streptococcus pneumoniae synthesized longer peptides than those synthesized by RizB, and the BAD_1200 protein of Bifidobacteria adolescentis showed higher activity toward aromatic amino acids than toward branched-chain ones.

  17. On the Temperature Dependence of Enzyme-Catalyzed Rates.

    PubMed

    Arcus, Vickery L; Prentice, Erica J; Hobbs, Joanne K; Mulholland, Adrian J; Van der Kamp, Marc W; Pudney, Christopher R; Parker, Emily J; Schipper, Louis A

    2016-03-29

    One of the critical variables that determine the rate of any reaction is temperature. For biological systems, the effects of temperature are convoluted with myriad (and often opposing) contributions from enzyme catalysis, protein stability, and temperature-dependent regulation, for example. We have coined the phrase "macromolecular rate theory (MMRT)" to describe the temperature dependence of enzyme-catalyzed rates independent of stability or regulatory processes. Central to MMRT is the observation that enzyme-catalyzed reactions occur with significant values of ΔCp(‡) that are in general negative. That is, the heat capacity (Cp) for the enzyme-substrate complex is generally larger than the Cp for the enzyme-transition state complex. Consistent with a classical description of enzyme catalysis, a negative value for ΔCp(‡) is the result of the enzyme binding relatively weakly to the substrate and very tightly to the transition state. This observation of negative ΔCp(‡) has important implications for the temperature dependence of enzyme-catalyzed rates. Here, we lay out the fundamentals of MMRT. We present a number of hypotheses that arise directly from MMRT including a theoretical justification for the large size of enzymes and the basis for their optimum temperatures. We rationalize the behavior of psychrophilic enzymes and describe a "psychrophilic trap" which places limits on the evolution of enzymes in low temperature environments. One of the defining characteristics of biology is catalysis of chemical reactions by enzymes, and enzymes drive much of metabolism. Therefore, we also expect to see characteristics of MMRT at the level of cells, whole organisms, and even ecosystems.

  18. A Link between Protein Structure and Enzyme Catalyzed Hydrogen Tunneling

    NASA Astrophysics Data System (ADS)

    Bahnson, Brian J.; Colby, Thomas D.; Chin, Jodie K.; Goldstein, Barry M.; Klinman, Judith P.

    1997-11-01

    We present evidence that the size of an active site side chain may modulate the degree of hydrogen tunneling in an enzyme-catalyzed reaction. Primary and secondary kH/kT and kD/kT kinetic isotope effects have been measured for the oxidation of benzyl alcohol catalyzed by horse liver alcohol dehydrogenase at 25 degrees C. As reported in earlier studies, the relationship between secondary kH/kT and kD/kT isotope effects provides a sensitive probe for deviations from classical behavior. In the present work, catalytic efficiency and the extent of hydrogen tunneling have been correlated for the alcohol dehydrogenase-catalyzed hydride transfer among a group of site-directed mutants at position 203. Val-203 interacts with the opposite face of the cofactor NAD+ from the alcohol substrate. The reduction in size of this residue is correlated with diminished tunneling and a two orders of magnitude decrease in catalytic efficiency. Comparison of the x-ray crystal structures of a ternary complex of a high-tunneling (Phe-93 --> Trp) and a low-tunneling (Val-203 --> Ala) mutant provides a structural basis for the observed effects, demonstrating an increase in the hydrogen transfer distance for the low-tunneling mutant. The Val-203 --> Ala ternary complex crystal structure also shows a hyperclosed interdomain geometry relative to the wild-type and the Phe-93 --> Trp mutant ternary complex structures. This demonstrates a flexibility in interdomain movement that could potentially narrow the distance between the donor and acceptor carbons in the native enzyme and may enhance the role of tunneling in the hydride transfer reaction.

  19. Pd-catalyzed decarboxylative cross coupling of potassium polyfluorobenzoates with aryl bromides, chlorides, and triflates.

    PubMed

    Shang, Rui; Xu, Qing; Jiang, Yuan-Ye; Wang, Yan; Liu, Lei

    2010-03-05

    Pd-catalyzed decarboxylative cross coupling of potassium polyfluorobenzoates with aryl bromides, chlorides, and triflates is achieved by using diglyme as the solvent. The reaction is useful for synthesis of polyfluorobiaryls from readily accessible and nonvolatile polyfluorobenzoate salts. Unlike the Cu-catalyzed decarboxylation cross coupling where oxidative addition is the rate-limiting step, in the Pd-catalyzed version decarboxylation is the rate-limiting step.

  20. Gold/acid-co-catalyzed direct microwave-assisted synthesis of fused azaheterocycles from propargylic hydroperoxides.

    PubMed

    Alcaide, Benito; Almendros, Pedro; Quirós, M Teresa

    2014-03-17

    The gold-acid-co-catalyzed synthesis of nine series of fused azaheterocycles with structural diversity starting from the same synthons as readily available propargylic hydroperoxides and aromatic amines has been achieved. The overall tandem process consists in a gold-catalyzed hydroperoxide rearrangement/Michael reaction followed by a final acid-catalyzed cyclization. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Facile Rh(III)-Catalyzed Synthesis of Fluorinated Pyridines

    PubMed Central

    Chen, Shuming; Bergman, Robert G.; Ellman, Jonathan A.

    2015-01-01

    A Rh(III)-catalyzed C–H functionalization approach was developed for the preparation of multi-substituted 3-fluoropyridines from α-fluoro-α,β-unsaturated oximes and alkynes. Oximes substituted with aryl, heteroaryl and alkyl β-substituents were effective coupling partners, as were symmetrical and unsymmetrical alkynes with aryl and alkyl substituents. The first examples of coupling α,β-unsaturated oximes with terminal alkynes was also demonstrated and proceeded with uniformly high regioselectivity to provide single 3-fluoropyridine regioisomers. Reactions were also conveniently set up in air on the bench top. PMID:25992591

  2. Rhodium(NHC)-catalyzed O-arylation of aryl bromides.

    PubMed

    Kim, Hyun Jin; Kim, Min; Chang, Sukbok

    2011-05-06

    The first example of the rhodium-catalyzed O-arylation of aryl bromides is reported. While the right combination of rhodium species and N-heterocyclic carbene (NHC) offered an effective catalytic system enabling the arylation to proceed, the choice of NHC was determined to be most important. The developed O-arylation protocol has a wide range of substrate scope, high functional group tolerance, and flexibility allowing a complementary route to either N- or O-arylation depending on the choice of NHC.

  3. Synthesis of Dihydrobenzofurans via Palladium-Catalyzed Heteroannulations

    SciTech Connect

    Rozhkov, Roman Vladimirovich

    2004-01-01

    Palladium-catalyzed heteroannulation of 1,3-dienes with 3-iodo-2-alkenols, and 2-iodo-2-alkenols, as well as their amino analogs, affords the corresponding cyclic ethers and amines respectively. The presence of a β-hydrogen in the vinylic halide results in β-hydride elimination giving the corresponding alkyne. The presence of a bulky group in the α-position of the vinylic halide results in failure or reduced amounts of annulation products. A chloride source, pyridine base and electron-rich phosphine are essential for this reaction.

  4. Complex Biotransformations Catalyzed by Radical S-Adenosylmethionine Enzymes*

    PubMed Central

    Zhang, Qi; Liu, Wen

    2011-01-01

    The radical S-adenosylmethionine (AdoMet) superfamily currently comprises thousands of proteins that participate in numerous biochemical processes across all kingdoms of life. These proteins share a common mechanism to generate a powerful 5′-deoxyadenosyl radical, which initiates a highly diverse array of biotransformations. Recent studies are beginning to reveal the role of radical AdoMet proteins in the catalysis of highly complex and chemically unusual transformations, e.g. the ThiC-catalyzed complex rearrangement reaction. The unique features and intriguing chemistries of these proteins thus demonstrate the remarkable versatility and sophistication of radical enzymology. PMID:21771780

  5. Some thoughts on the muon catalyzed fusion reactor

    SciTech Connect

    Takahashi, H.

    1986-01-01

    The design of the muon catalyzed fusion reactor is discussed. Some of the engineering challenges and critical research areas such as ..pi../sup -/ meson transport, beam entry single crystal window and coherent x-ray for stripping the muon from ..cap alpha.. particle, are considered. In order to reduce the tritium inventory and neutron wall loading, use of the laser technique for manipulating the d-t mixture is considered. The heterogeneous d-t mixture using the droplet or jet is discussed. 39 refs., 6 figs.

  6. Can Chlorine Anion Catalyze the Reaction fo HOCl with HCl?

    NASA Technical Reports Server (NTRS)

    Richardson, S. L.; Francisco, J. S.; Mebel, A. M.; Morokuma, K.

    1997-01-01

    The reaction of HOCl + HCl -> Cl2 + H20 in the presence of Cl has been studied using ab initio methods. This reaction has been shown to have a high activation barrier of 46.5 kcal/mol. The chlorine anion, Cl- is found to catalyze the reaction, viz. two mechanisms. The first involves Cl- interacting through the concerted four-center transition state of the neutral reaction. The other mechanism involves the formation of a HCl-HOCl-Cl- intermediate which dissociates into Cl2 + Cl- + H20. The steps are found to have no barriers. The overall exothermicity is 15.5 kcal/mol.

  7. Iridium-Catalyzed Kinetic Asymmetric Transformations of Racemic Allylic Benzoates

    PubMed Central

    Stanley, Levi M.; Bai, Chen; Ueda, Mitsuhiro; Hartwig, John F.

    2010-01-01

    Versatile methods for iridium-catalyzed, kinetic asymmetric substitution of racemic, branched allylic esters are reported. These reactions occur with a variety of aliphatic, aryl, and heteroaryl allylic benzoates to form the corresponding allylic substitution products in high yields (74–96%) with good to excellent enantioselectivity (84–98% ee) with a scope that encompasses a range of anionic carbon and heteroatom nucleophiles. These kinetic asymmetric processes occur with distinct stereochemical courses for racemic aliphatic and aromatic allylic benzoates, and the high reactivity of branched allylic benzoates enables enantioselective allylic substitutions that are slow or poorly selective with linear allylic electrophiles. PMID:20552969

  8. Rhodium-catalyzed enantioselective cyclopropanation of electron deficient alkenes

    PubMed Central

    Wang, Hengbin; Guptill, David M.; Alvarez, Adrian Varela

    2013-01-01

    The rhodium-catalyzed reaction of electron-deficient alkenes with substituted aryldiazoacetates and vinyldiazoacetates results in highly stereoselective cyclopropanations. With adamantylglycine derived catalyst Rh2(S-TCPTAD)4, high asymmetric induction (up to 98% ee) can be obtained with a range of substrates. Computational studies suggest that the reaction is facilitated by weak interaction between the carbenoid and the substrate carbonyl but subsequently proceeds via different pathways depending on the nature of the carbonyl.. Acrylates and acrylamides result in the formation of cyclopropanation products while the use of unsaturated aldehydes and ketones results in the formation of epoxides. PMID:24049630

  9. Kinetics of acid-catalyzed cleavage of cumene hydroperoxide.

    PubMed

    Levin, M E; Gonzales, N O; Zimmerman, L W; Yang, J

    2006-03-17

    The cleavage of cumene hydroperoxide, in the presence of sulfuric acid, to form phenol and acetone has been examined by adiabatic calorimetry. As expected, acid can catalyze cumene hydroperoxide reaction at temperatures below that of thermally-induced decomposition. At elevated acid concentrations, reactivity is also observed at or below room temperature. The exhibited reactivity behavior is complex and is significantly affected by the presence of other species (including the products). Several reaction models have been explored to explain the behavior and these are discussed.

  10. Palladium-Catalyzed Carbonylation of sec- and tert-Alcohols.

    PubMed

    Dong, Kaiwu; Sang, Rui; Liu, Jie; Razzaq, Rauf; Franke, Robert; Jackstell, Ralf; Beller, Matthias

    2017-05-22

    A general palladium-catalyzed synthesis of linear esters directly from sec- and tert-alcohols is described. Compared to the classic Koch-Haaf reaction, which leads to branched products, this new transformation gives the corresponding linear esters in high yields and selectivity. Key for this protocol is the use of an advanced palladium catalyst system with L2 (py(t) bpx) as the ligand. A variety of aliphatic and benzylic alcohols can be directly used and the catalyst efficiency for the benchmark reaction is outstanding (turnover number up to 89 000). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Lipase-catalyzed aza-Michael reaction on acrylate derivatives.

    PubMed

    Steunenberg, Peter; Sijm, Maarten; Zuilhof, Han; Sanders, Johan P M; Scott, Elinor L; Franssen, Maurice C R

    2013-04-19

    A methodology has been developed for an efficient and selective lipase-catalyzed aza-Michael reaction of various amines (primary and secondary) with a series of acrylates and alkylacrylates. Reaction parameters were tuned, and under the optimal conditions it was found that Pseudomonas stutzeri lipase and Chromobacterium viscosum lipase showed the highest selectivity for the aza-Michael addition to substituted alkyl acrylates. For the first time also, some CLEAs were examined that showed a comparable or higher selectivity and yield than the free enzymes and other formulations.

  12. Iron-Catalyzed Cross-Coupling of Alkenyl Acetates.

    PubMed

    Gärtner, Dominik; Stein, André Luiz; Grupe, Sabine; Arp, Johannes; Jacobi von Wangelin, Axel

    2015-09-01

    Stable C-O linkages are generally unreactive in cross-coupling reactions which mostly employ more electrophilic halides or activated esters (triflates, tosylates). Acetates are cheap and easily accessible electrophiles but have not been used in cross-couplings because the strong C-O bond and high propensity to engage in unwanted acetylation and deprotonation. Reported herein is a selective iron-catalyzed cross-coupling of diverse alkenyl acetates, and it operates under mild reaction conditions (0 °C, 2 h) with a ligand-free catalyst (1-2 mol%).

  13. Cooperative Catalysis: Calcium and Camphorsulfonic Acid Catalyzed Cycloisomerization of Diynols.

    PubMed

    Rauser, Marian; Schroeder, Sebastian; Niggemann, Meike

    2015-11-02

    The first transition metal-free cycloisomerization of easily accessible diynols is presented as a novel approach to bicyclic 2H-pyrans. As a one-step protocol, the reaction proceeds in a single reaction cascade by intertwining mechanistic fragments borrowed from transition metal-catalyzed Claisen rearrangment of vinyl ethers with our own work on allenyl/propargyl cation rearrangements and a 6π-oxo-electrocylization. It is enabled by a new cooperative catalytic system that combines a simple Ca(2+) catalyst with camphorsulfonic acid. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Lipase-catalyzed synthesis of monoacylglycerol in a homogeneous system.

    PubMed

    Monteiro, Julieta B; Nascimento, Maria G; Ninow, Jorge L

    2003-04-01

    The 1,3-regiospecifique lipase, Lipozyme IM, catalyzed the esterification of lauric acid and glycerol in a homogeneous system. To overcome the drawback of the insolubility of glycerol in hexane, which is extensively used in enzymatic synthesis, a mixture of n-hexane/tert-butanol (1:1, v/v) was used leading to a monophasic system. The conversion of lauric acid into monolaurin was 65% in 8 h, when a molar ratio of glycerol to fatty acid (5:1) was used with the fatty acid at 0.1 M, and the phenomenon of acyl migration was minimized.

  15. Iridium(I)-Catalyzed Regio- and Enantioselective Allylic Amidation

    PubMed Central

    Singh, Om V.; Han, Hyunsoo

    2009-01-01

    Ir(I)-catalyzed intermolecular allylic amidation of ethyl allylic carbonates with soft nitrogen nucleophiles under completely “salt-free” conditions is described. A combination of [Ir(COD)Cl]2, a chiral phosphoramidite ligand L*, and DBU as a base in THF effects the reaction. The reaction appears to be quite general, accommodating a wide variety of R-groups and soft nitrogen nucleophiles, and proceeds with excellent regio- and enantioselectivities to afford the branched N-protected allylic amines. The developed reaction was conveniently utilized in the asymmetric synthesis of Boc protected α- and β-amino acids as well as (−)-cytoxazone. PMID:19554202

  16. Iridium-Catalyzed (Z)-Trialkylsilylation of Terminal Olefins

    PubMed Central

    Lu, Biao; Falck, J. R.

    2010-01-01

    A complex of commercial [Ir(OMe)(cod)]2 and 4,4-di-tert-butyl-2,2-bipyridine (dtbpy) catalyzes the Z-selective, dehydrative silylation of terminal alkenes, but not 1,2-disubstituted alkenes, with triethylsilane or benzyldimethylsilane in THF at 40 °C. Yields and Z-stereoselectivity were significantly improved by 2-norbornene, in contrast with other sacrificial alkenes. The reaction is compatible with many functional groups including epoxides, ketones, amides, alcohols, esters, halides, ketals and silanes. a,b-Unsaturated esters were unreactive. The reaction probably proceeds through a Heck-type mechanism. PMID:20136153

  17. Base-Catalyzed Depolymerization of Lignin: Separation of Monomers

    SciTech Connect

    Vigneault, A.; Johnson, D. K.; Chornet, E.

    2007-12-01

    In our quest for fractionating lignocellulosic biomass and valorizing specific constitutive fractions, we have developed a strategy for the separation of 12 added value monomers generated during the hydrolytic based-catalyzed depolymerization of a Steam Exploded Aspen Lignin. The separation strategy combines liquid-liquid-extraction (LLE), followed by vacuum distillation, liquid chromatography (LC) and crystallization. LLE, vacuum distillation and flash LC were tested experimentally. Batch vacuum distillation produced up to 4 fractions. Process simulation confirmed that a series of 4 vacuum distillation columns could produce 5 distinct monomer streams, 3 of which require further chromatography and crystallization for purification.

  18. Aminoacyl-RNA synthesis catalyzed by an RNA.

    PubMed

    Illangasekare, M; Sanchez, G; Nickles, T; Yarus, M

    1995-02-03

    An RNA has been selected that rapidly aminoacylates its 2'(3') terminus when provided with phenylalanyl-adenosine monophosphate. That is, the RNA accelerates the same aminoacyl group transfer catalyzed by protein aminoacyl-transfer RNA synthetases. The best characterized RNA reaction requires both Mg2+ and Ca2+. These results confirm a necessary prediction of the RNA world hypothesis and represent efficient RNA reaction (> or = 10(5) times accelerated) at a carbonyl carbon, exemplifying a little explored type of RNA catalysis.

  19. New modes for the osmium-catalyzed oxidative cyclization.

    PubMed

    Donohoe, Timothy J; Lindsay-Scott, Peter J; Parker, Jeremy S; Callens, Cedric K A

    2010-03-05

    The osmium-catalyzed oxidative cyclization of amino alcohol initiators formally derived from 1,4-dienes is an effective method for the construction of pyrrolidines, utilizing a novel reoxidant (4-nitropyridine N-oxide = NPNO). The cyclization of enantiopure syn- and anti-amino alcohols gives rise to enantiopure cis- and trans-2,5-disubstituted pyrrolidines, respectively. Moreover, the cyclization of bis-homoallylic amines bearing an exocyclic chelating group is shown to be a complementary method for trans-pyrrolidine formation.

  20. Synthesis of Optically Active Polystyrene Catalyzed by Monophosphine Pd Complexes.

    PubMed

    Jouffroy, Matthieu; Armspach, Dominique; Matt, Dominique; Osakada, Kohtaro; Takeuchi, Daisuke

    2016-07-11

    Cationic Pd(II) monophosphine complexes derived from α- and β-cyclodextrins (CDs) promote the homopolymerization of styrene under carbon monoxide pressure. Although reversible CO coordination takes place under catalytic conditions according to (13) C NMR studies with (13) C-enriched CO, both complexes catalyze the formation of CO-free styrene polymers. These macromolecules display optical activity as a result of the presence of stereoregular sequences within the overall atactic polymer. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Palladium-Catalyzed Enantioselective Decarboxylative Allylic Alkylation of Cyclopentanones.

    PubMed

    Craig, Robert A; Loskot, Steven A; Mohr, Justin T; Behenna, Douglas C; Harned, Andrew M; Stoltz, Brian M

    2015-11-06

    The first general method for the enantioselective construction of all-carbon quaternary centers on cyclopentanones by enantioselective palladium-catalyzed decarboxylative allylic alkylation is described. Employing the electronically modified (S)-(p-CF3)3-t-BuPHOX ligand, α-quaternary cyclopentanones were isolated in yields up to >99% with ee's up to 94%. Additionally, in order to facilitate large-scale application of this method, a low catalyst loading protocol was employed, using as little as 0.15 mol % Pd, furnishing the product without any loss in ee.

  2. Iridium-catalyzed (Z)-trialkylsilylation of terminal olefins.

    PubMed

    Lu, Biao; Falck, J R

    2010-03-05

    A complex of commercial [Ir(OMe)(cod)](2) and 4,4-di-tert-butyl-2,2-bipyridine (dtbpy) catalyzes the Z-selective, dehydrative silylation of terminal alkenes, but not 1,2-disubstituted alkenes, with triethylsilane or benzyldimethylsilane in THF at 40 degrees C. Yields and Z-stereoselectivity were significantly improved by 2-norbornene, in contrast with other sacrificial alkenes. The reaction is compatible with many functional groups including epoxides, ketones, amides, alcohols, esters, halides, ketals, and silanes. alpha,beta-Unsaturated esters were unreactive. The reaction probably proceeds through a Heck-type mechanism.

  3. Nickel-Catalyzed Allylic Substitution of Simple Alkenes

    PubMed Central

    Matsubara, Ryosuke; Jamison, Timothy F.

    2011-01-01

    This report describes a nickel-catalyzed allylic substitution process of simple alkenes whereby an important structural motif, a 1,4-diene, was prepared. A key for this success is the use of an appropriate Ni-phosphine complex and a stoichiometric amount of silyl triflate. Reactions of 1-alkyl-substituted alkenes consistently provided 1,1-disubstituted alkenes with high selectivity. Insight into the reaction mechanism as well as miscellaneous application of the developed catalytic process is also documented. PMID:21387565

  4. Palladium-Catalyzed Fluoroarylation of gem-Difluoroalkenes.

    PubMed

    Tang, Hai-Jun; Lin, Ling-Zhi; Feng, Chao; Loh, Teck-Peng

    2017-08-07

    A Pd-catalyzed fluoroarylation of gem-difluoroalkenes with aryl halides is reported. By taking advantage of the in situ generated α-CF3 -benzylsilver intermediates derived from the nucleophilic addition of silver fluoride to gem-difluoroalkenes, this strategy bypasses the use of a strong base, thus enabling a mild and general synthetic method for ready access to non-symmetric α,α-disubstituted trifluoroethane derivatives. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Direct metal-catalyzed regioselective functionalization of enamides.

    PubMed

    Gigant, Nicolas; Chausset-Boissarie, Laëtitia; Gillaizeau, Isabelle

    2014-06-16

    Enamides are stable enamine surrogates and provide key intermediates for the synthesis of small but complex nitrogen-containing compounds. Metal-catalyzed regioselective functionalization of enamides provides a rapid method to synthesize useful nitrogen containing heterocycles. This review discloses the recent progress made in the development of the C-H functionalization of enamides involving efficient and atom-economical routes. Syntheses of different heterocycles are classified based on the site reactivity of enamides and key mechanistic insights are given for each transformation.

  6. Copper-Catalyzed Azide–Alkyne Click Chemistry for Bioconjugation

    PubMed Central

    Presolski, Stanislav I.; Hong, Vu Phong; Finn, M.G.

    2012-01-01

    The copper-catalyzed azide-alkyne cycloaddition reaction is widely used for the connection of molecular entities of all sizes. A protocol is provided here for the process with biomolecules. Ascorbate is used as reducing agent to maintain the required cuprous oxidation state. Since these convenient conditions produce reactive oxygen species, five equivalents of a copper-binding ligand is used with respect to metal. The ligand both accelerates the reaction and serves as a sacrificial reductant, protecting the biomolecules from oxidation. A procedure is also described for testing the efficiency of the reaction under desired conditions for purposes of optimization, before expensive biological reagents are used. PMID:22844652

  7. Cobalt-Catalyzed Z-Selective Hydrosilylation of Terminal Alkynes.

    PubMed

    Teo, Wei Jie; Wang, Chao; Tan, Ye Wei; Ge, Shaozhong

    2017-03-07

    A cobalt-catalyzed Z-selective hydrosilylation of alkynes has been developed relying on catalysts generated from bench-stable Co(OAc)2 and pyridine-2,6-diimine (PDI) ligands. A variety of functionalized aromatic and aliphatic alkynes undergo this transformation, yielding Z-vinylsilanes in high yields with excellent selectivities (Z/E ratio ranges from 90:10 to >99:1). The addition of a catalytic amount of phenol effectively suppressed the Z/E-isomerization of the Z-vinylsilanes that formed under catalytic conditions.

  8. Ruthenium-Catalyzed meta-Selective C—H Bromination

    PubMed Central

    Teskey, Christopher J; Lui, Andrew Y W; Greaney, Michael F

    2015-01-01

    The first example of a transition-metal-catalyzed, meta-selective C–H bromination procedure is reported. In the presence of catalytic [{Ru(p-cymene)Cl2}2], tetrabutylammonium tribromide can be used to functionalize the meta C–H bond of 2-phenylpyridine derivatives, thus affording difficult to access products which are highly predisposed to further derivatization. We demonstrate this utility with one-pot bromination/arylation and bromination/alkenylation procedures to deliver meta-arylated and meta-alkenylated products, respectively, in a single step. PMID:26288217

  9. Transition-metal-catalyzed asymmetric allylic dearomatization reactions.

    PubMed

    Zhuo, Chun-Xiang; Zheng, Chao; You, Shu-Li

    2014-08-19

    Dearomatization reactions serve as powerful methods for the synthesis of highly functionalized, three-dimensional structures starting with simple planar aromatic compounds. Among processes of this type, catalytic asymmetric dearomatization (CADA) reactions are attractive owing to the large number of aromatic compounds that are readily available and the fact that they enable direct access to enantiopure polycycles and spirocycles, which frequently are key structural motifs in biologically active natural products and pharmaceuticals. However, as a consequence of their high stabilities, arenes only difficultly participate in dearomatization reactions that take place with high levels of enantioselectivity. Transition-metal-catalyzed asymmetric allylic substitution reactions have been demonstrated to be powerful methods for enantioselective formation of C-C and C-X (X = O, N, S, etc.) bonds. However, the scope of these processes has been explored mainly using soft carbon nucleophiles, some hard carbon nucleophiles such as enolates and preformed organometallic reagents, and heteroatom nucleophiles. Readily accessible aromatic compounds have been only rarely used directly as nucleophiles in these reactions. In this Account, we present the results of studies we have conducted aimed at the development of transition-metal-catalyzed asymmetric allylic dearomatization reactions. By utilizing this general process, we have devised methods for direct dearomatization of indoles, pyrroles, phenols, naphthols, pyridines, and pyrazines, which produce various highly functionalized structural motifs bearing all-carbon quaternary stereogenic centers in a straightforward manner. In mechanistic investigations of the dearomatization process, we found that the five-membered spiroindolenines serve as intermediates, which readily undergo stereospecific allylic migration to form corresponding tetrahydro-1H-carbazoles upon treatment with a catalytic amount of TsOH. It is worth noting that no

  10. Fe-catalyzed etching of exfoliated graphite through carbon hydrogenation

    PubMed Central

    Cheng, Guangjun; Calizo, Irene; Hacker, Christina A.; Richter, Curt A.; Hight Walker, Angela R.

    2016-01-01

    We present an investigation on Fe-catalyzed etching of graphite by dewetting Fe thin films on graphite in forming gas. Raman mapping of the etched graphite shows thickness variation in the etched channels and reveals that the edges are predominately terminated in zigzag configuration. X-ray diffraction and photoelectron spectroscopy measurements identify that the catalytic particles are Fe with the presence of iron carbide and iron oxides. The existence of iron carbide indicates that, in additional to carbon hydrogenation, carbon dissolution into Fe is also involved during etching. Furthermore, the catalytic particles can be re-activated upon a second annealing in forming gas. PMID:27840449

  11. Coalification by clay-catalyzed oligomerization of plant monomers

    SciTech Connect

    Orchin, M.; Wilson, R.M.

    1991-01-01

    The chemical structure'' of coal, if indeed there is one, remains an enigma. Over the years numerous chemists have integrated a host of experimental observations to generate various average'' structures which differ greatly. Our approach is to regard the structural question of coal as a problem in natural product chemistry. Our model is that of a macromolecular polymer initially synthesized from monomeric naturally-occuring hydroxy and methoxy substituted propenylbenzenes (C{sub 6}-C{sub 3} units), properly aligned to undergo oligomerization reactions via conventional organic reaction mechanisms, specifically Diels-Alder radical cation condensations, phenolic coupling, and proton-catalyzed isomerization and cyclization.

  12. Enantioselective palladium(0)-catalyzed Nazarov-type cyclization.

    PubMed

    Kitamura, Kei; Shimada, Naoyuki; Stewart, Craig; Atesin, Abdurrahman C; Ateşin, Tülay A; Tius, Marcus A

    2015-05-18

    A Pd(0)-catalyzed asymmetric Nazarov-type cyclization is described. The optimized ligand for the reaction incorporates a weakly coordinating pyridine ring into a TADDOL-derived phosphoramidite (TADDOL=α,α,α,α-tetraaryl-1,3-dioxolane-4,5-dimethanol). The reaction leads to the formation of cyclopentenones as single diastereoisomers that incorporate two contiguous asymmetric centers, one tertiary and one an all-carbon-atom quaternary stereocenter, in high yield and optical purity. It is noteworthy that the reaction does not require that substrates should be activated by aryl substituents. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Stereoselective synthesis of cyclohexanones via phase transfer catalyzed double addition of nucleophiles to divinyl ketones.

    PubMed

    Silvanus, Andrew C; Groombridge, Benjamin J; Andrews, Benjamin I; Kociok-Köhn, Gabriele; Carbery, David R

    2010-11-05

    Functionalized cyclohexanones are formed in excellent yield and diastereoselectivity from a phase transfer catalyzed double addition of active methylene pronucleophiles to nonsymmetrical divinyl ketones.

  14. Solid oxide fuel cell with internal reforming, catalyzed interconnect for use therewith, and methods

    SciTech Connect

    Liu, Di-Jia; Guan, Jie; Minh, Nguyen

    2010-06-08

    A catalyzed interconnect for an SOFC electrically connects an anode and an anodic current collector and comprises a metallic substrate, which provides space between the anode and anodic current collector for fuel gas flow over at least a portion of the anode, and a catalytic coating on the metallic substrate comprising a catalyst for catalyzing hydrocarbon fuel in the fuel gas to hydrogen rich reformate. An SOFC including the catalyzed anodic inter-connect, a method for operating an SOFC, and a method for making a catalyzed anodic interconnect are also disclosed.

  15. Recent Developments in Metal-Catalyzed Additions of Oxygen Nucleophiles to Alkenes and Alkynes

    NASA Astrophysics Data System (ADS)

    Hintermann, Lukas

    Progress in the field of metal-catalyzed redox-neutral additions of oxygen nucleophiles (water, alcohols, carboxylic acids, and others) to alkenes, alkynes, and allenes between 2001 and 2009 is critically reviewed. Major advances in reaction chemistry include development of chiral Lewis acid catalyzed asymmetric oxa-Michael additions and Lewis-acid catalyzed hydro-alkoxylations of nonactivated olefins, as well as further development of Markovnikov-selective cationic gold complex-catalyzed additions of alcohols or water to alkynes and allenes.

  16. Enhancement of photosensitivity in the alcohol-added ferroin-catalyzed Belousov-Zhabotinsky reaction system

    NASA Astrophysics Data System (ADS)

    Jiro, Abe; Kazuhisa, Matsuda; Masakazu, Taka; Yasuo, Shirai

    1995-10-01

    The observation of photoinduced image formation in the alcohol-added ferroin-catalyzed Belousov-Zhabotinsky (BZ) reaction is reported. It is found that alcohol acts as a reagent that reduces the activation energy both of the ferroin-catalyzed and the Ce-catalyzed BZ reaction system and enhances the photosensitivity. By comparing the photosensitivity and photoinduced image formation for the ferroin-catalyzed BZ system with and without alcohol, we concluded that the photosensitivity of this alcohol-added BZ reaction system is enhanced by the presence of alcohol. This enhancement of the photosensitivity was confirmed in other alcohols such as ethanol, 1-propanol and 2-propanol.

  17. SidL, an Aspergillus fumigatus Transacetylase Involved in Biosynthesis of the Siderophores Ferricrocin and Hydroxyferricrocin ▿ † ‡

    PubMed Central

    Blatzer, Michael; Schrettl, Markus; Sarg, Bettina; Lindner, Herbert H.; Pfaller, Kristian; Haas, Hubertus

    2011-01-01

    The opportunistic fungal pathogen Aspergillus fumigatus produces four types of siderophores, low-molecular-mass iron chelators: it excretes fusarinine C (FsC) and triacetylfusarinine C (TAFC) for iron uptake and accumulates ferricrocin (FC) for hyphal and hydroxyferricrocin (HFC) for conidial iron distribution and storage. Siderophore biosynthesis has recently been shown to be crucial for fungal virulence. Here we identified a new component of the fungal siderophore biosynthetic machinery: AFUA_1G04450, termed SidL. SidL is conserved only in siderophore-producing ascomycetes and shows similarity to transacylases involved in bacterial siderophore biosynthesis and the N5-hydroxyornithine:anhydromevalonyl coenzyme A-N5-transacylase SidF, which is essential for TAFC biosynthesis. Inactivation of SidL in A. fumigatus decreased FC biosynthesis during iron starvation and completely blocked FC biosynthesis during iron-replete growth. In agreement with these findings, SidL deficiency blocked conidial accumulation of FC-derived HFC under iron-replete conditions, which delayed germination and decreased the size of conidia and their resistance to oxidative stress. Remarkably, the sidL gene is not clustered with other siderophore-biosynthetic genes, and its expression is not affected by iron availability. Tagging of SidL with enhanced green fluorescent protein suggested a cytosolic localization of the FC-biosynthetic machinery. Taken together, these data suggest that SidL is a constitutively active N5-hydroxyornithine-acetylase required for FC biosynthesis, in particular under iron-replete conditions. Moreover, this study revealed the unexpected complexity of siderophore biosynthesis, indicating the existence of an additional, iron-repressed N5-hydroxyornithine-acetylase. PMID:21622789

  18. Search for muon catalyzed d 3He-fusion

    NASA Astrophysics Data System (ADS)

    Maev, E. M.; Balin, D. V.; Case, T.; Crowe, K. M.; Del Rosso, A.; Ganzha, V. A.; Hartmann, F. J.; Kozlov, S. M.; Lauss, B.; Maev, O. E.; Mühlbauer, M.; Mulhauser, F.; Petitjean, C.; Petrov, G. E.; Sadetsky, S. M.; Schapkin, G. N.; Schott, W.; Semenchuk, G. G.; Smirenin, Yu. V.; Soroka, M. A.; Vasiliev, A. A.; Vorobyov, A. A.; Voropaev, N. I.; Zmeskal, J.

    1999-06-01

    We report on the results of an experiment aimed at observing muon-catalyzed d 3He-fusion with a setup previously used for studies of the muon-catalyzed dd-fusion. The basic element of the setup is a high pressure ionization chamber operating as an active target. In this experiment the chamber was filled with an HD + 3He (5.6%) gas mixture at 13.2 bar pressure and 50 K temperature. These conditions were chosen as optimal for formation of the 3Heμd-molecules with a low level of background from the d-μ-d fusion. The chamber was exposed to the negative muon beam at PSI. During a 3-week data-taking period, 9.7 × 108 muon stops have been selected. The analysis of the data was able to determine a new upper limit for the d 3He-fusion rate in the 3Heμd-molecule (λf≤ 6× 104 s-1), which is more than three orders of magnitude lower than the previously existed limit.

  19. Laccase catalyzed covalent coupling of fluorophenols increases lignocellulose surface hydrophobicity.

    PubMed

    Kudanga, Tukayi; Prasetyo, Endry Nugroho; Widsten, Petri; Kandelbauer, Andreas; Jury, Sandra; Heathcote, Carol; Sipilä, Jussi; Weber, Hansjoerg; Nyanhongo, Gibson S; Guebitz, Georg M

    2010-04-01

    This work presents for the first time the mechanistic evidence of a laccase-catalyzed method of covalently grafting hydrophobicity enhancing fluorophenols onto Fagus sylvatica veneers. Coupling of fluorophenols onto complex lignin model compounds guaiacylglycerol beta-guaiacyl ether and syringylglycerol beta-guaiacyl ether was demonstrated by LC-MS and NMR. Laccase-mediated coupling increased binding of 4-[4-(trifluoromethyl)phenoxy]phenol (4,4-F3MPP) and 4-(trifluoromethoxy)phenol (4-F3MP) to veneers by 77.1% and 39.2%, respectively. XPS studies showed that laccase-catalyzed grafting of fluorophenols resulted in a fluorine content of 6.39% for 4,4-F3MPP, 3.01% for 4-F3MP and 0.26% for 4-fluoro-2-methylphenol (4,2-FMP). Grafting of the fluorophenols 4,2-FMP, 4-F3MP and 4,4-F3MPP led to a 9.6%, 28.6% and 65.5% increase in hydrophobicity, respectively, when compared to treatments with the respective fluorophenols in the absence of laccase, in good agreement with XPS data. Copyright 2009 Elsevier Ltd. All rights reserved.

  20. Chloride-catalyzed corrosion of plutonium in glovebox atmospheres

    SciTech Connect

    Burgess, M.; Haschke, J.M.; Allen, T.H.; Morales, L.A.; Jarboe, D.M.; Puglisi, C.V.

    1998-04-01

    Characterization of glovebox atmospheres and the black reaction product formed on plutonium surfaces shows that the abnormally rapid corrosion of components in the fabrication line is consistent with a complex salt-catalyzed reaction involving gaseous hydrogen chloride (HCl) and water. Analytical data verify that chlorocarbon and HCl vapors are presented in stagnant glovebox atmospheres. Hydrogen chloride concentrations approach 7 ppm at some locations in the glovebox line. The black corrosion product is identified as plutonium monoxide monohydride (PuOH), a product formed by hydrolysis of plutonium in liquid water and salt solutions at room temperature. Plutonium trichloride (PuCl{sub 3}) produced by reaction of HCl at the metal surface is deliquescent and apparently forms a highly concentrated salt solution by absorbing moisture from the glovebox atmosphere. Rapid corrosion is attributed to the ensuing salt-catalyzed reaction between plutonium and water. Experimental results are discussed, possible involvement of hydrogen fluoride (HF) is examined, and methods of corrective action are presented in this report.

  1. Mechanism of Water Oxidation Catalyzed by a Mononuclear Manganese Complex.

    PubMed

    Li, Ying-Ying; Ye, Ke; Siegbahn, Per E M; Liao, Rong-Zhen

    2016-12-07

    The design and synthesis of biomimetic Mn complexes to catalyze oxygen evolution is a very appealing goal because water oxidation in nature employs a Mn complex. Recently, the mononuclear Mn complex [LMn(II) (H2 O)2 ](2+) [1, L=Py2 N(tBu)2 , Py=pyridyl] was reported to catalyze water oxidation electrochemically at an applied potential of 1.23 V at pH 12.2 in aqueous solution. Density functional calculations were performed to elucidate the mechanism of water oxidation promoted by this catalyst. The calculations showed that 1 can lose two protons and one electron readily to produce [LMn(III) (OH)2 ](+) (2), which then undergoes two sequential proton-coupled electron-transfer processes to afford [LMn(V) OO](+) (4). The O-O bond formation can occur through direct coupling of the two oxido ligands or through nucleophilic attack of water. These two mechanisms have similar barriers of approximately 17 kcal mol(-1) . The further oxidation of 4 to generate [LMn(VI) OO](2+) (5), which enables O-O bond formation, has a much higher barrier. In addition, ligand degradation by C-H activation has a similar barrier to that for the O-O bond formation, and this explains the relatively low turnover number of this catalyst.

  2. Can proteins and crystals self-catalyze methyl rotations?

    SciTech Connect

    Smith, Jeremy C; Baudry, Jerome

    2005-10-01

    The {chi} (C{sub {alpha}}-C{sub {beta}}) torsional barrier in the dipeptide alanine (N-methyl-l-alanyl-N-methylamide) crystal was investigated using ab initio calculations at various levels of theory, molecular mechanics, and molecular dynamics. For one of the two molecules in the asymmetric unit the calculations suggest that rotation around the ? dihedral angle is catalyzed by the crystal environment, reducing by up to 2kT the torsional barrier in the crystal with respect to that in the gas phase. This catalytic effect is present at both low and room temperature and originates from a van der Waals destabilization of the minima in the methyl dihedral potential coming from the nonbonded environment of the side chain. Screening of a subset of the Protein Data Bank with a pharmacophore model reproducing the crystal environment around this side chain methyl identified a protein containing an alanine residue with an environment similar to that in the crystal. Calculations indicate that this ? torsional barrier is also reduced in the protein at low temperature but not at room temperature. This suggests that environment-catalyzed rotation of methyl groups can occur both in the solid phase and in native biological structures, though this effect might be temperature-dependent. The relevance of this catalytic effect is discussed in terms of its natural occurrence and its possible contribution to the low-frequency vibrational modes of molecules.

  3. Mechanistic Elucidation of Zirconium-Catalyzed Direct Amidation.

    PubMed

    Lundberg, Helena; Tinnis, Fredrik; Zhang, Jiji; Algarra, Andrés G; Himo, Fahmi; Adolfsson, Hans

    2017-02-15

    The mechanism of the zirconium-catalyzed condensation of carboxylic acids and amines for direct formation of amides was studied using kinetics, NMR spectroscopy, and DFT calculations. The reaction is found to be first order with respect to the catalyst and has a positive rate dependence on amine concentration. A negative rate dependence on carboxylic acid concentration is observed along with S-shaped kinetic profiles under certain conditions, which is consistent with the formation of reversible off-cycle species. Kinetic experiments using reaction progress kinetic analysis protocols demonstrate that inhibition of the catalyst by the amide product can be avoided using a high amine concentration. These insights led to the design of a reaction protocol with improved yields and a decrease in catalyst loading. NMR spectroscopy provides important details of the nature of the zirconium catalyst and serves as the starting point for a theoretical study of the catalytic cycle using DFT calculations. These studies indicate that a dinuclear zirconium species can catalyze the reaction with feasible energy barriers. The amine is proposed to perform a nucleophilic attack at a terminal η(2)-carboxylate ligand of the zirconium catalyst, followed by a C-O bond cleavage step, with an intermediate proton transfer from nitrogen to oxygen facilitated by an additional equivalent of amine. In addition, the DFT calculations reproduce experimentally observed effects on reaction rate, induced by electronically different substituents on the carboxylic acid.

  4. RNA catalyzes nuclear pre-mRNA splicing

    PubMed Central

    Fica, Sebastian M.; Tuttle, Nicole; Novak, Thaddeus; Li, Nan-Sheng; Lu, Jun; Koodathingal, Prakash; Dai, Qing; Staley, Jonathan P.; Piccirilli, Joseph A.

    2014-01-01

    SUMMARY In nuclear pre-messenger RNA splicing, introns are excised by the spliceosome, a multi-megadalton machine composed of both proteins and small nuclear RNAs (snRNAs). Over thirty years ago, following the discovery of self-splicing group II intron RNAs, the snRNAs were hypothesized to catalyze splicing. However, no definitive evidence for a role of either RNA or protein in catalysis by the spliceosome has been reported to date. By using metal rescue strategies, here we show that the U6 snRNA catalyzes both splicing reactions by positioning divalent metals that stabilize the leaving groups during each reaction. Strikingly, all of the U6 catalytic metal ligands we identified correspond to the ligands observed to position catalytic, divalent metals in crystal structures of a group II intron RNA. These findings indicate that group II introns and the spliceosome share common catalytic mechanisms, and likely common evolutionary origins. Our results demonstrate that RNA mediates catalysis within the spliceosome. PMID:24196718

  5. Firefly bioluminescence: a mechanistic approach of luciferase catalyzed reactions.

    PubMed

    Marques, Simone M; Esteves da Silva, Joaquim C G

    2009-01-01

    Luciferase is a general term for enzymes catalyzing visible light emission by living organisms (bioluminescence). The studies carried out with Photinus pyralis (firefly) luciferase allowed the discovery of the reaction leading to light production. It can be regarded as a two-step process: the first corresponds to the reaction of luciferase's substrate, luciferin (LH(2)), with ATP-Mg(2+) generating inorganic pyrophosphate and an intermediate luciferyl-adenylate (LH(2)-AMP); the second is the oxidation and decarboxylation of LH(2)-AMP to oxyluciferin, the light emitter, producing CO(2), AMP, and photons of yellow-green light (550- 570 nm). In a dark reaction LH(2)-AMP is oxidized to dehydroluciferyl-adenylate (L-AMP). Luciferase also shows acyl-coenzyme A synthetase activity, which leads to the formation of dehydroluciferyl-coenzyme A (L-CoA), luciferyl-coenzyme A (LH(2)-CoA), and fatty acyl-CoAs. Moreover luciferase catalyzes the synthesis of dinucleoside polyphosphates from nucleosides with at least a 3'-phosphate chain plus an intact terminal pyrophosphate moiety. The LH(2) stereospecificity is a particular feature of the bioluminescent reaction where each isomer, D-LH(2) or L-LH(2), has a specific function. Practical applications of the luciferase system, either in its native form or with engineered proteins, encloses the analytical assay of metabolites like ATP and molecular biology studies with luc as a reporter gene, including the most recent and increasing field of bioimaging.

  6. Catalyzed Synthesis of Zinc Clays by Prebiotic Central Metabolites.

    PubMed

    Zhou, Ruixin; Basu, Kaustuv; Hartman, Hyman; Matocha, Christopher J; Sears, S Kelly; Vali, Hojatollah; Guzman, Marcelo I

    2017-04-03

    How primordial metabolic networks such as the reverse tricarboxylic acid (rTCA) cycle and clay mineral catalysts coevolved remains a mystery in the puzzle to understand the origin of life. While prebiotic reactions from the rTCA cycle were accomplished via photochemistry on semiconductor minerals, the synthesis of clays was demonstrated at low temperature and ambient pressure catalyzed by oxalate. Herein, the crystallization of clay minerals is catalyzed by succinate, an example of a photoproduced intermediate from central metabolism. The experiments connect the synthesis of sauconite, a model for clay minerals, to prebiotic photochemistry. We report the temperature, pH, and concentration dependence on succinate for the synthesis of sauconite identifying new mechanisms of clay formation in surface environments of rocky planets. The work demonstrates that seeding induces nucleation at low temperatures accelerating the crystallization process. Cryogenic and conventional transmission electron microscopies, X-ray diffraction, diffuse reflectance Fourier transformed infrared spectroscopy, and measurements of total surface area are used to build a three-dimensional representation of the clay. These results suggest the coevolution of clay minerals and early metabolites in our planet could have been facilitated by sunlight photochemistry, which played a significant role in the complex interplay between rocks and life over geological time.

  7. Mechanism of methane formation in potassium catalyzed carbon gasification

    SciTech Connect

    Mims, C.A.; Krajewski, J.J.

    1986-11-01

    The authors have performed a kinetics and isotope tracer study of the mechanism of CH/sub 4/ formation from a potassium catalyzed carbon during gasification in atmospheres containing H/sub 2/O, H/sub 2/, CO/sub 2/, and CO Temperatures from 925 to 1025 K and pressures up to 8 atm were studied. The authors found that although potassium salts catalyze the formation of CH/sub 4/, there is not a one-to-one correspondence between CH/sub 4/ and CO formation rates implying different sites for generation of the two products. At low gas phase carbon activity the CH/sub 4/ product is formed by direct hydrogenation of substrate carbon and not by secondary reaction of gas phase CO or CO/sub 2/. At higher gas phase carbon activities some CH/sub 4/ is produced from gas phase carbon oxides as a result of carbon deposition. In some cases the deposited carbon shows higher reactivity than the original carbon substrate so that this can be legitimately viewed as a secondary pathway.

  8. An antibody-catalyzed bimolecular Diels-Alder reaction

    SciTech Connect

    Braisted, A.C.; Schultz, P.G. )

    1990-09-26

    There exist over 1,500 known enzymes which carry out a vast array of chemical reactions with remarkable specificity and reaction rates. It is surprising then that there are no documented examples of enzyme-catalyzed pericyclic cycloaddition reactions, yet there are among the most powerful and commonly used reactions in synthetic organic chemistry. The most important of these is the Diels-Alder reaction of a diene with a dienophile, which provides a straightforward and highly stereospecific route to cyclohexene derivatives. Given the importance of this reaction in organic chemistry and its novel mechanism, it was of interest to ask whether a Diels-Alderase enzymatic catalyst could be evolved from an antibody combining site. Generation of antibodies to a structure that mimics the pericyclic transition state for a Diels-Alder reaction should result in an antibody combining site that lowers the entropy of activation {Delta}S{sup {double dagger}} by binding both the diene and the dienophile in a reactive conformation. The authors approach toward the design of a transition-state analogue involves incorporation of an ethano bridge, which locks the cyclohexene ring of hapten in a conformation that resembles the proposed pericyclic transition state for the Diels-Alder reaction of cisoid diene with dienophile. The authors now report that antibodies generated to the transition-state analogue catalyze the addition of the acyclic water-soluble diene to the maleimide derivative to give the cyclohexene product.

  9. Solution-solid-solid mechanism: superionic conductors catalyze nanowire growth.

    PubMed

    Wang, Junli; Chen, Kangmin; Gong, Ming; Xu, Bin; Yang, Qing

    2013-09-11

    The catalytic mechanism offers an efficient tool to produce crystalline semiconductor nanowires, in which the choice, state, and structure of catalysts are active research issues of much interest. Here we report a novel solution-solid-solid (SSS) mechanism for nanowire growth catalyzed by solid-phase superionic conductor nanocrystals in low-temperature solution. The preparation of Ag2Se-catalyzed ZnSe nanowires at 100-210 °C is exampled to elucidate the SSS model, which can be extendable to grow other II-VI semiconductor (e.g., CdSe, ZnS, and CdS) nanowires by the catalysis of nanoscale superionic-phase silver or copper(I) chalcogenides (Ag2Se, Ag2S, and Cu2S). The exceptional catalytic ability of these superionic conductors originates from their structure characteristics, known for high-density vacancies and fast mobility of silver or copper(I) cations in the rigid sublattice of Se(2-) or S(2-) ions. Insights into the SSS mechanism are provided based on the formation of solid solution and the solid-state ion diffusion/transport at solid-solid interface between catalyst and nanowire.

  10. Metal-Catalyzed Oxidation and Photo-oxidation of Glucagon.

    PubMed

    Zhang, Jian

    2016-08-01

    The oxidation of glucagon by the H2O2/Cu(2+) system and by simulated sunlight was studied using HPLC-MS methodologies. It was found that copper ion-catalyzed oxidation is much faster in the residue 1-12 region than in photo-oxidation, but it is slower than photo-oxidation in the residue 18-29 region. This difference is due to the unique feature of the primary sequence of glucagon. The residue 1-12 region contains His-1 and Asp-9 that can bind to Cu(2+) ions and catalyze the oxidation of His-1 and Tyr-10, while the residue 18-29 region lacks these charged residues near the liable Met-27 and Trp-25 and hence no catalysis by the neighboring groups occurs. Fragment (residue 13-17) was more stable than the other regions of the peptide toward photo-oxidation because it contains only one oxidizable residue, Tyr-13. These findings may help explain the mechanism of action of glucagon and provide some hints for the development of effective anti-diabetic drug molecules and stable glucagon formulations.

  11. Aldose Reductase-catalyzed Reduction of Aldehyde Phospholipids

    PubMed Central

    Srivastava, Sanjay; Spite, Matthew; Trent, John O.; West, Matthew B.; Ahmed, Yonis; Bhatnagar, Aruni

    2012-01-01

    SUMMARY Oxidation of unsaturated phospholipids results in the generation of aldehyde side chains that remain esterified to the phospholipid backbone. Such “core” aldehydes elicit immune responses and promote inflammation. However, the biochemical mechanisms by which phospholipid aldehydes are metabolized or detoxified are not well understood. In the studies reported here, we examined whether aldose reductase (AR), which reduces hydrophobic aldehydes, metabolizes phospholipid aldehydes. Incubation with AR led to the reduction of 5-oxovaleroyl, 7-oxo-5-heptenoyl, 5-hydroxy-6-oxo-caproyl, and 5-hydroxy-8-oxo-6-octenoyl phospholipids generated upon oxidation of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (PAPC). The enzyme also catalyzed the reduction of phospholipid aldehydes generated from the oxidation of 1-alkyl, and 1-alkenyl analogs of PAPC, and 1-palmitoyl-2-arachidonoyl phosphatidic acid or phosphoglycerol. Aldose reductase catalyzed the reduction of chemically synthesized 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphatidylcholine (POVPC) with a Km of 10 μM. Addition of POVPC to the culture medium led to incorporation and reduction of the aldehyde in COS-7 and THP-1 cells. Reduction of POVPC in these cells was prevented by the AR inhibitors sorbinil and tolrestat and was increased in COS-7 cells overexpressing AR. Together, these observations suggest that AR may be a significant participant in the metabolism of several structurally diverse phospholipid aldehydes. This metabolism may be a critical regulator of the pro-inflammatory and immunogenic effects of oxidized phospholipids. PMID:15465833

  12. Cu-Catalyzed Click Reaction in Carbohydrate Chemistry.

    PubMed

    Tiwari, Vinod K; Mishra, Bhuwan B; Mishra, Kunj B; Mishra, Nidhi; Singh, Anoop S; Chen, Xi

    2016-03-09

    Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC), popularly known as the "click reaction", serves as the most potent and highly dependable tool for facile construction of simple to complex architectures at the molecular level. Click-knitted threads of two exclusively different molecular entities have created some really interesting structures for more than 15 years with a broad spectrum of applicability, including in the fascinating fields of synthetic chemistry, medicinal science, biochemistry, pharmacology, material science, and catalysis. The unique properties of the carbohydrate moiety and the advantages of highly chemo- and regioselective click chemistry, such as mild reaction conditions, efficient performance with a wide range of solvents, and compatibility with different functionalities, together produce miraculous neoglycoconjugates and neoglycopolymers with various synthetic, biological, and pharmaceutical applications. In this review we highlight the successful advancement of Cu(I)-catalyzed click chemistry in glycoscience and its applications as well as future scope in different streams of applied sciences.

  13. Titanium-Catalyzed Silicon Nanostructures Grown by APCVD

    NASA Astrophysics Data System (ADS)

    Usman, Mohammad A. U.; Smith, Brady J.; Jackson, Justin B.; De Long, Matthew C.; Miller, Mark S.

    2015-01-01

    We report on growth of Ti-catalyzed silicon nanostructures (SNCs) through atmospheric-pressure chemical vapor deposition. An extensive growth study relating the growth condition parameters, including the partial pressure of SiCl4 gas, reaction temperature, and reaction time, was carried out to obtain insight into the growth regimes for the observed SNCs. Based on phase diagram analysis of Ti-Si alloy and growth rate analysis of the silicon nanowires (SNWs) and silicon nanoplatelets, we believe the growth mechanism to be strongly dependent on the thermodynamics of the system, exhibiting a delicate balance that can easily tip between the growth and etching regimes of the system. Three types of SNCs were observed frequently throughout the study: nanowires, nanoplatelets, and balls. Regimes for highly etched growth were also noted through growth conditions plots. Ti-catalyzed SNWs grown using SiCl4 gas strongly suggest growth occurring through a type of vapor-solid-solid (VSS) mechanism that is limited by diffusion through the solid-catalyst interface. On the other hand, the two-dimensional SNP morphologies suggest growth occurring through the twin-plane mechanism at the edges, at 10 nm to 100 nm scales, also through a similar, VSS mechanism.

  14. Lipase-catalyzed polyester synthesis – A green polymer chemistry

    PubMed Central

    Kobayashi, Shiro

    2010-01-01

    This article is a short comprehensive review describing in vitro polyester synthesis catalyzed by a hydrolysis enzyme of lipase, most of which has been developed for these two decades. Polyesters are prepared by repeated ester bond-formation reactions; they include two major modes, ring-opening polymerization (ROP) of cyclic monomers such as cyclic esters (lactones) and condensation polymerization via the reaction between a carboxylic acid or its ester group and an alcohol group. Polyester synthesis is, therefore, a reaction in reverse way of in vivo lipase catalysis of ester bond-cleavage with hydrolysis. The lipase-catalyzed polymerizations show very high chemo-, regio-, and enantio-selectivities and involve various advantageous characteristics. Lipase is robust and compatible with other chemical catalysts, which allows novel chemo-enzymatic processes. New syntheses of a variety of functional polyesters and a plausible reaction mechanism of lipase catalysis are mentioned. The polymerization characteristics are of green nature currently demanded for sustainable society, and hence, desirable for conducting ‘green polymer chemistry’. PMID:20431260

  15. Subtilisin-catalyzed resolution of N-acyl arylsulfinamides.

    PubMed

    Savile, Christopher K; Magloire, Vladimir P; Kazlauskas, Romas J

    2005-02-23

    We report the first biocatalytic route to sulfinamides (R-S(O)-NH2), whose sulfur stereocenter makes them important chiral auxiliaries for the asymmetric synthesis of amines. Subtilisin E did not catalyze hydrolysis of N-acetyl or N-butanoyl arylsulfinamides, but did catalyze a highly enantioselective (E > 150 favoring the (R)-enantiomer) hydrolysis of N-chloroacetyl and N-dihydrocinnamoyl arylsulfinamides. Gram-scale resolutions using subtilisin E overexpressed in Bacillus subtilis yielded, after recrystallization, three synthetically useful auxiliaries: (R)-p-toluenesulfinamide (42% yield, 95% ee), (R)-p-chlorobenzenesulfinamide (30% yield, 97% ee), and (R)-2,4,6-trimethylbenzenesulfinamide (30% yield, 99% ee). Molecular modeling suggests that the N-chloroacetyl and N-dihydrocinnamoyl groups mimic a phenylalanine moiety and thus bind the sulfinamide to the active site. Molecular modeling further suggests that enantioselectivity stems from a favorable hydrophobic interaction between the aryl group of the fast-reacting (R)-arylsulfinamide and the S1' leaving group pocket in subtilisin E.

  16. Study of microwave effects on the lipase-catalyzed hydrolysis.

    PubMed

    Chen, Chia-Chen; Reddy, P Muralidhar; Devi, C Shobha; Chang, Po-Chi; Ho, Yen-Peng

    2016-01-01

    The effect of microwave heating on lipase-catalyzed reaction remains controversial. It is not clear whether the reaction rate enhancements are purely due to thermal/heating effects or to non-thermal effects. Therefore, quantitative mass spectrometry was used to conduct accurate kinetic analysis of lipase-catalyzed hydrolysis of triolein by microwave and conventional heating. Commercial lipases from Candida rugosa (CRL), Porcine Pancreas (PPL), and Burkholderia cepacia (BCL) were used. Hydrolysis reactions were performed at various temperatures and pH levels, along with various amounts of buffer and enzymes. Hydrolysis product yields at each time point using an internal-standard method showed no significant difference between microwave and conventional heating conditions when the reaction was carried out at the same temperature. CRL showed optimum catalytic activity at 37 °C, while PPL and BCL had better activities at 50 °C. The phosphate buffer was found to give a better hydrolysis yield than the Tris-HCl buffer. Overall results prove that a non-thermal effect does not exist in microwave-assisted lipase hydrolysis of triolein. Therefore, conventional heating at high temperatures (e.g., 50 °C) can be also used to accelerate hydrolysis reactions.

  17. Thermodynamics of Enzyme-Catalyzed Reactions: Part 1. Oxidoreductases

    NASA Astrophysics Data System (ADS)

    Goldberg, Robert N.; Tewari, Yadu B.; Bell, Donna; Fazio, Kari; Anderson, Ellen

    1993-03-01

    Equilibrium constants and enthalpy changes for reactions catalyzed by oxidoreductases have been compiled. For each reaction the following information is given: the reference for the data; the reaction studied; the name of the enzyme used and its Enzyme Commission number; the method of measurement; the conditions of measurement (temperature, pH, ionic strength, and the buffer(s) and cofactor(s) used); the data and an evaluation of it; and, sometimes, commentary on the data and on any corrections which have been applied to it. The thermodynamic conventions pertinent to the tabulation of equilibrium data are discussed. A distinction is made between those thermodynamic quantities which pertain to the overall biochemical reaction and those which pertain to a reference reaction that involves specific species. The data from 205 references have been examined and evaluated. Chemical Abstract Service Registry Numbers have been assigned to the substances involved in these various reactions. There is a cross reference between the substances and the Enzyme Commission numbers of the enzymes used to catalyze the reactions in which the substances participated.

  18. Enzyme catalyzed electricity-driven water softening system.

    PubMed

    Arugula, Mary A; Brastad, Kristen S; Minteer, Shelley D; He, Zhen

    2012-12-10

    Hardness in water, which is caused by divalent cations such as calcium and magnesium ions, presents a major water quality problem. Because hard water must be softened before use in residential applications, there is great interest in the saltless water softening process because, unlike ion exchange softeners, it does not introduce additional ions into water. In this study, a saltless hardness removal driven by bioelectrochemical energy produced through enzymatic oxidation of glucose was proposed and investigated. Glucose dehydrogenase was coated on a carbon electrode to catalyze glucose oxidation in the presence of NAD⁺ as a cofactor/mediator and methylene green as an electrocatalyst. The results showed that electricity generation stimulated hardness removal compared with non-electricity conditions. The enzymatic water softener worked upon a 6h batch operation per day for eight days, and achieved an average hardness removal of 46% at a high initial concentration of 800 mg/L as CaCO₃. More hardness was removed at a lower initial concentration. For instance, at 200mg/L as CaCO₃ the enzymatic water softener removed 76.4±4.6% of total hardness. The presence of magnesium ions decreased hardness removal because of its larger hydrated radius than calcium ions. The enzymatic water softener removed 70-80% of total hardness from three actual hard water samples. These results demonstrated a proof-of-concept that enzyme catalyzed electricity generation can be used to soften hard water. Copyright © 2012 Elsevier Inc. All rights reserved.

  19. A comparative study of ozonation, iron coated zeolite catalyzed ozonation and granular activated carbon catalyzed ozonation of humic acid.

    PubMed

    Gümüş, Dilek; Akbal, Feryal

    2017-05-01

    This study compares ozonation (O3), iron coated zeolite catalyzed ozonation (ICZ-O3) and granular activated carbon catalyzed ozonation (GAC-O3) for removal of humic acid from an aqueous solution. The results were evaluated by the removal of DOC that specifies organic matter, UV254 absorbance, SUVA (Specific Ultraviolet Absorbance at 254 nm) and absorbance at 436 nm. When ozonation was used alone, DOC removal was 21.4% at an ozone concentration of 10 mg/L, pH 6.50 and oxidation time of 60 min. The results showed that the use of ICZ or GAC as a catalyst increased the decomposition of humic acid compared to ozonation alone. DOC removal efficiencies were 62% and 48.1% at pH 6.5, at a catalyst loading of 0.75 g/L, and oxidation time of 60 min for ICZ and GAC, respectively. The oxidation experiments were also carried out using <100 kDa and <50 kDa molecular size fractions of humic acid in the presence of ICZ or GAC. Catalytic ozonation also yielded better DOC and UV254 reduction in both <50 kDa and <100 kDa fractions of HA compared to ozonation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Metabolism of Monoterpenes

    PubMed Central

    Croteau, Rodney; Hooper, Caroline Lee

    1978-01-01

    The essential oil from mature leaves of flowering peppermint (Mentha piperita L.) contains up to 15% (—)-menthyl acetate, and leaf discs converted exogenous (—)-[G-3H]menthol into this ester in approximately 15% yield of the incorporated precursor. Leaf extracts catalyzed the acetyl coenzyme A-dependent acetylation of (—)-[G-3H]menthol and the product of this transacetylase reaction was identified by radiochromatographic techniques. Transacetylase activity was located mainly in the 100,000g supernatant fraction, and the preparation was partially purified by combination of Sephadex G-100 gel filtration and chromatography on O-diethylaminoethyl-cellulose. The transacetylase had a molecular weight of about 37,000 as judged by Sephadex G-150 gel filtration, and a pH optimum near 9. The apparent Km and velocity for (—)-menthol were 0.3 mm and 16 nmol/hr· mg of protein, respectively. The saturation curve for acetyl coenzyme A was sigmoidal, showing apparent saturation near 0.1 mm. Dithioerythritol was required for maximum activity and stability of the enzyme, and the enzyme was inhibited by thiol directed reagents such as p-hydroxymercuribenzoate. Diisopropylfluorophosphate also inhibited transacylation suggesting the involvement of a serine residue in catalysis. The transacylase was highly specific for acetyl coenzyme A; propionyl coenzyme A and butyryl coenzyme A were not nearly as efficient as acyl donors (11% and 2%, respectively). However, the enzyme was much less selective with regard to the alcohol substrate, suggesting that the nature of the acetate ester synthesized in mint is more dependent on the type of alcohol available than on the specificity of the transacetylase. This is the first report on an enzyme involved in monoterpenol acetylation in plants. A very similar enzyme, catalyzing this key reaction in the metabolism of menthol, was also isolated from the flowers of peppermint. PMID:16660375

  1. Enantioselective Total Synthesis of (−)-Nardoaristolone B via a Gold(I)-Catalyzed Oxidative Cyclization

    PubMed Central

    2015-01-01

    The first enantioselective total synthesis of (−)-nardoaristolone B is accomplished by the implementation of an enantio- and diastereoselective copper(I)-catalyzed conjugate addition/enolate trapping sequence and a gold(I)-catalyzed oxidative cyclization (intermolecular oxidant), employed for the first time in total synthesis. PMID:25563976

  2. Palladium-catalyzed carbonylation of o-iodoanilines for synthesis of isatoic anhydrides.

    PubMed

    Gao, Sha; Chen, Ming; Zhao, Mi-Na; Du, Wei; Ren, Zhi-Hui; Wang, Yao-Yu; Guan, Zheng-Hui

    2014-05-02

    A novel palladium-catalyzed oxidative double carbonylation of o-iodoanilines for the synthesis of isatoic anhydrides has been developed. The reaction employs readily available o-iodoanilines as the starting materials and proceeds under mild conditions. For extension, palladium-catalyzed oxidative carbonylation of anthranilic acids was developed for the synthesis of substituted isatoic anhydrides in high to excellent yields.

  3. Recent advances in chiral imino-containing ligands for metal-catalyzed asymmetric transformations.

    PubMed

    Chen, Xu; Lu, Zhan

    2017-03-21

    In this review, the recent applications of a variety of chiral imino-containing ligands classified by different types of metal-catalyzed asymmetric reactions are summarized. The progress made in this area would encourage us to design and synthesize more novel chiral imino-containing ligands, and explore their applications in metal-catalyzed asymmetric transformations.

  4. Copper-catalyzed aerobic oxidative synthesis of aryl nitriles from benzylic alcohols and aqueous ammonia.

    PubMed

    Tao, Chuanzhou; Liu, Feng; Zhu, Youmin; Liu, Weiwei; Cao, Zhiling

    2013-05-28

    Copper-catalyzed direct conversion of benzylic alcohols to aryl nitriles was realized using NH3(aq.) as the nitrogen source, O2 as the oxidant and TEMPO as the co-catalyst. Furthermore, copper-catalyzed one-pot synthesis of primary aryl amides from alcohols was also achieved.

  5. Oxygenase-Catalyzed Desymmetrization of N,N-Dialkyl-piperidine-4-carboxylic Acids**

    PubMed Central

    Rydzik, Anna M; Leung, Ivanhoe K H; Kochan, Grazyna T; McDonough, Michael A; Claridge, Timothy D W; Schofield, Christopher J

    2014-01-01

    γ-Butyrobetaine hydroxylase (BBOX) is a 2-oxoglutarate dependent oxygenase that catalyzes the final hydroxylation step in the biosynthesis of carnitine. BBOX was shown to catalyze the oxidative desymmetrization of achiral N,N-dialkyl piperidine-4-carboxylates to give products with two or three stereogenic centers. PMID:25164544

  6. Copper-catalyzed cascade reactions of α,β-unsaturated esters with keto esters

    PubMed Central

    Wang, Chongnian; Li, Zengchang

    2015-01-01

    Summary A copper-catalyzed cascade reaction of α,β-unsaturated esters with keto esters is reported. It features a copper-catalyzed reductive aldolization followed by a lactonization. This method provides a facile approach to prepare γ-carboxymethyl-γ-lactones and δ-carboxymethyl-δ-lactones under mild reaction conditions. PMID:25815072

  7. Regioselective hydrothiolation of alkenes bearing heteroatoms with thiols catalyzed by palladium diacetate.

    PubMed

    Tamai, Taichi; Ogawa, Akiya

    2014-06-06

    In sharp contrast to many examples of transition-metal-catalyzed hydrothiolation of alkynes, the corresponding catalytic addition of thiols to alkenes has remained undeveloped. However, a novel Pd-catalyzed addition of thiols to alkenes bearing a heteroatom, such as oxygen and nitrogen, is found to proceed under mild conditions to give the corresponding Markovnikov adducts, regioselectively, in good yields.

  8. ROLE OF COPPER,ZINC-SUPEROXIDE DISMUTASE IN CATALYZING NITROTYROSINE FORMATION IN MURINE LIVER

    USDA-ARS?s Scientific Manuscript database

    The solely known function of Cu,Zn-superoxide dismutase (SOD1) is to catalyze the dismutation of superoxide anion into hydrogen peroxide. Our objective was to determine if SOD1 catalyzed murine liver protein nitration induced by acetaminophen (APAP) and lipopolysaccharide (LPS). Liver and plasma ...

  9. Gold-catalyzed cyclizations of alkynol-based compounds: synthesis of natural products and derivatives.

    PubMed

    Alcaide, Benito; Almendros, Pedro; Alonso, José M

    2011-09-13

    The last decade has witnessed dramatic growth in the number of reactions catalyzed by gold complexes because of their powerful soft Lewis acid nature. In particular, the gold-catalyzed activation of propargylic compounds has progressively emerged in recent years. Some of these gold-catalyzed reactions in alkynes have been optimized and show significant utility in organic synthesis. Thus, apart from significant methodology work, in the meantime gold-catalyzed cyclizations in alkynol derivatives have become an efficient tool in total synthesis. However, there is a lack of specific review articles covering the joined importance of both gold salts and alkynol-based compounds for the synthesis of natural products and derivatives. The aim of this Review is to survey the chemistry of alkynol derivatives under gold-catalyzed cyclization conditions and its utility in total synthesis, concentrating on the advances that have been made in the last decade, and in particular in the last quinquennium.

  10. Degradation and transformation of atrazine under catalyzed ozonation process with TiO2 as catalyst.

    PubMed

    Yang, Yixin; Cao, Hongbin; Peng, Pai; Bo, Hongmiao

    2014-08-30

    Degradation of atrazine by heterogeneously catalyzed ozonation was carried out with TiO2 in the form of rutile as the catalyst. Some experimental factors such as catalyst dose, ozone dose and initial concentration of atrazine were investigated for their influence on catalyzed ozonation process. Although atrazine was effectively removed from aqueous solution by catalyzed ozonation process, the mineralization degree only reached 56% at the experimental conditions. Five transformation products were identified by GC/MS analysis. The degradation of atrazine involved de-alkylation, de-chlorination and de-amination. Diaminotriazine and 5-azauracil were the de-chlorinated and de-aminated products, respectively. The evolution of concentration of transformation products during catalyzed ozonation process was compared with uncatalyzed ozonation to show the degradation pathway. Toxicity tests based on the inhibition of the luminescence emitted by Vibrio fisheri indicated the detoxification of atrazine by catalyzed ozonation.

  11. Rh(II)-catalyzed Reactions of Diazoesters with Organozinc Reagents

    PubMed Central

    Panish, Robert; Selvaraj, Ramajeyam; Fox, Joseph M.

    2015-01-01

    Rh(II)-catalyzed reactions of diazoesters with organozinc reagents are described. Diorganozinc reagents participate in reactions with diazo compounds by two distinct, catalyst-dependent mechanisms. With bulky diisopropylethylacetate ligands, the reaction mechanism is proposed to involve initial formation of a Rh-carbene and subsequent carbozincation to give a zinc enolate. With Rh2(OAc)4, it is proposed that initial formation of an azine precedes 1,2-addition by an organozinc reagent. This straightforward route to the hydrazone products provides a useful method for preparing chiral quaternary α-aminoesters or pyrazoles via the Paul-Knorr condensation with 1,3-diketones. Crossover and deuterium labeling experiments provide evidence for the mechanisms proposed. PMID:26241081

  12. Transition-metal-catalyzed synthesis of phenols and aryl thiols

    PubMed Central

    Liu, Shasha

    2017-01-01

    Phenols and aryl thiols are fundamental building blocks in organic synthesis and final products with interesting biological activities. Over the past decades, substantial progress has been made in transition-metal-catalyzed coupling reactions, which resulted in the emergence of new methods for the synthesis of phenols and aryl thiols. Aryl halides have been extensively studied as substrates for the synthesis of phenols and aryl thiols. In very recent years, C–H activation represents a powerful strategy for the construction of functionalized phenols directly from various arenes. However, the synthesis of aryl thiols through C–H activation has not been reported. In this review, a brief overview is given of the recent advances in synthetic strategies for both phenols and aryl thiols. PMID:28405239

  13. The role of fluoride in montmorillonite-catalyzed RNA synthesis.

    PubMed

    Aldersley, Michael F; Joshi, Prakash C

    2014-05-01

    The montmorillonite-catalyzed reactions of the 5'-phosphorimidazolide of adenosine in the presence of fluoride were investigated to complete our study on the effect of salts on this type of reaction. Both anions and cations have been found to influence the oligomerization reactions of the activated nucleotides, being used here as a model system for pre-biotic RNA synthesis. However, in total contrast to the behavior of the activated nucleotides in the presence of montmorillonite and other salts, alkali metal fluorides did not yield any detectable oligomerization products except in very dilute (<0.005 M) solutions of fluoride. Instead, 5'-phosphorofluoridates were formed. Their identity was confirmed by a combination of HPLC, mass spectrometry, synthesis, and NMR.

  14. Palladium(II)-Catalyzed Enantioselective Reactions Using COP Catalysts.

    PubMed

    Cannon, Jeffrey S; Overman, Larry E

    2016-10-18

    Allylic amides, amines, and esters are key synthetic building blocks. Their enantioselective syntheses under mild conditions is a continuing pursuit of organic synthesis methods development. One opportunity for the synthesis of these building blocks is by functionalization of prochiral double bonds using palladium(II) catalysis. In these reactions, nucleopalladation mediated by a chiral palladium(II) catalyst generates a new heteroatom-substituted chiral center. However, reactions where nucleopalladation occurs with antarafacial stereoselectivity are difficult to render enantioselective because of the challenge of transferring chiral ligand information across the square-planar palladium complex to the incoming nucleophile. In this Account, we describe the development and use of enantiopure palladium(II) catalysts of the COP (chiral cobalt oxazoline palladacyclic) family for the synthesis of enantioenriched products from starting materials derived from prochiral allylic alcohols. We begin with initial studies aimed at rendering catalyzed [3,3]-sigmatropic rearrangements of allylic imidates enantioselective, which ultimately led to the identification of the significant utility of the COP family of Pd(II) catalysts. The first use of an enantioselective COP catalyst was reported by Richards' and our laboratories in 2003 for the enantioselective rearrangement of allylic N-arylimidates. Shortly thereafter, we discovered that the chloride-bridged COP dimer, [COP-Cl]2, was an excellent enantioselective catalyst for the rearrangement of (E)-allylic trichloroacetimidates to enantioenriched allylic trichloroacetamides, this conversion being the most widely used of the allylic imidate rearrangements. We then turn to discuss SN2' reactions catalyzed by the acetate-bridged COP dimer, [COP-OAc]2, which proceed by a unique mechanism to provide branched allylic esters and allylic phenyl ethers in high enantioselectivity. Furthermore, because of the unique nucleopalladation

  15. Measurements of muon-catalyzed dt fusion in solid HD

    NASA Astrophysics Data System (ADS)

    Porcelli, Tracy Ann

    1999-12-01

    The first measurement of muon catalyzed dt fusion ( dtm--> 4He + n + m- ) in solid HD at ~ 3 K has been performed. The theory describing the formation of the [(dtm)pe e] muonic molecule from the resonant reaction tm+HD-->[(dtm) pee] , a key process in the dt fusion cycle, can now be tested against the experimental results. Using an experimental technique which employs solid layers of hydrogen isotopes, the energy of molecular formation is determined via time of flight, and dt fusion time spectra in solid HD have been measured. The theory describing the resonant formation of the dtm muonic molecule is compared to the experimental results through Monte Carlo simulations. The energy dependent molecular formation rates calculated for HD at 3 K have been employed in the Monte Carlo with the resultant simulated fusion time spectra in fair agreement with the experimental results.

  16. Measurements of Muon Catalyzed dt Fusion in Solid HD

    NASA Astrophysics Data System (ADS)

    Porcelli, Tracy

    1999-05-01

    The first measurement of muon catalyzed dt fusion (dtμ arrow ^4He + n + μ^-) in solid HD at ~ 3 K has been performed. The theory describing the formation of the [(dtμ)pee)] muonic molecule from the resonant reaction tμ + HD arrow [(dtμ)pee], a key process in the dt fusion cycle, can now be tested against experimental results. Using an experimental technique which employs solid layers of hydrogen isotopes, the energy of molecular formation is determined via time of flight, and dt fusion time spectra in solid HD have been measured. The theory describing the resonant formation of the dtμ muonic molecule is compared to the experimental results through Monte Carlo simulations. The energy dependent molecular formation rates calculated for HD at 3 K have been employed in the Monte Carlo with the resultant fusion time spectra in fair agreement with the experimental results.

  17. Field Emission from Self-Catalyzed GaAs Nanowires.

    PubMed

    Giubileo, Filippo; Di Bartolomeo, Antonio; Iemmo, Laura; Luongo, Giuseppe; Passacantando, Maurizio; Koivusalo, Eero; Hakkarainen, Teemu V; Guina, Mircea

    2017-09-16

    We report observations of field emission from self-catalyzed GaAs nanowires grown on Si (111). The measurements were taken inside a scanning electron microscope chamber with a nano-controlled tungsten tip functioning as anode. Experimental data were analyzed in the framework of the Fowler-Nordheim theory. We demonstrate stable current up to 10(-7) A emitted from the tip of single nanowire, with a field enhancement factor β of up to 112 at anode-cathode distance d = 350 nm. A linear dependence of β on the anode-cathode distance was found. We also show that the presence of a Ga catalyst droplet suppresses the emission of current from the nanowire tip. This allowed for the detection of field emission from the nanowire sidewalls, which occurred with a reduced field enhancement factor and stability. This study further extends GaAs technology to vacuum electronics applications.

  18. Quinone-Catalyzed Selective Oxidation of Organic Molecules

    PubMed Central

    Wendlandt, Alison E.

    2016-01-01

    Lead In Quinones are common stoichiometric reagents in organic chemistry. High potential para-quinones, such as DDQ and chloranil, are widely used and typically promote hydride abstraction. In recent years, many catalytic applications of these methods have been achieved by using transition metals, electrochemistry or O2 to regenerate the oxidized quinone in situ. Complementary studies have led to the development of a different class of quinones that resemble the ortho-quinone cofactors in Copper Amine Oxidases and mediate efficient and selective aerobic and/or electrochemical dehydrogenation of amines. The latter reactions typically proceed via electrophilic transamination and/or addition-elimination reaction mechanisms, rather than hydride abstraction pathways. The collective observations show that the quinone structure has a significant influence on the reaction mechanism and have important implications for the development of new quinone reagents and quinone-catalyzed transformations. PMID:26530485

  19. Site-specific DNA transesterification catalyzed by a restriction enzyme

    PubMed Central

    Sasnauskas, Giedrius; Connolly, Bernard A.; Halford, Stephen E.; Siksnys, Virginijus

    2007-01-01

    Most restriction endonucleases use Mg2+ to hydrolyze phosphodiester bonds at specific DNA sites. We show here that BfiI, a metal-independent restriction enzyme from the phospholipase D superfamily, catalyzes both DNA hydrolysis and transesterification reactions at its recognition site. In the presence of alcohols such as ethanol or glycerol, it attaches the alcohol covalently to the 5′ terminus of the cleaved DNA. Under certain conditions, the terminal 3′-OH of one DNA strand can attack the target phosphodiester bond in the other strand to create a DNA hairpin. Transesterification reactions on DNA with phosphorothioate linkages at the target bond proceed with retention of stereoconfiguration at the phosphorus, indicating, uniquely for a restriction enzyme, a two-step mechanism. We propose that BfiI first makes a covalent enzyme–DNA intermediate, and then it resolves it by a nucleophilic attack of water or an alcohol, to yield hydrolysis or transesterification products, respectively. PMID:17267608

  20. Dirhodium Catalyzed C-H Arene Amination using Hydroxylamines

    PubMed Central

    Paudyal, Mahesh P.; Adebesin, Adeniyi Michael; Burt, Scott R.; Ess, Daniel H.; Ma, Zhiwei; Kürti, László; Falck, John R.

    2016-01-01

    Primary and N-alkyl arylamine motifs are key functional groups in pharmaceuticals, agrochemicals and functional materials as well as in bioactive natural products. However, there is a dearth of generally applicable methods for the direct replacement of aryl hydrogens with –NH2/-NH-alkyl moieties. Here, we present a mild dirhodium-catalyzed C-H amination for conversion of structurally diverse monocyclic and fused aromatics to the corresponding primary and N-alkyl arylamines using either NH2/NHalkyl-O-(sulfonyl)hydroxylamines as aminating agents; the relatively weak RSO2O-N bond functions as an internal oxidant. The methodology is operationally simple, scalable, and fast at or below ambient temperature, furnishing arylamines in moderate-to-good yields and with good regioselectivity. It can be readily extended to the synthesis of fused N-heterocycles. PMID:27609890

  1. Manganese-Catalyzed Upgrading of Ethanol into 1-Butanol.

    PubMed

    Fu, Shaomin; Shao, Zhihui; Wang, Yujie; Liu, Qiang

    2017-08-30

    Biomass-derived ethanol is an important renewable feedstock. Its conversion into high-quality biofuels is a promising route to replace fossil resources. Herein, an efficient manganese-catalyzed Guerbet-type condensation reaction of ethanol to form 1-butanol was explored. This is the first example of upgrading ethanol into higher alcohols using a homogeneous non-noble-metal catalyst. This process proceeded selectively in the presence of a well-defined manganese pincer complex at the parts per million (ppm) level. The developed reaction represents a sustainable synthesis of 1-butanol with excellent turnover number (>110 000) and turnover frequency (>3000 h(-1)). Moreover, mechanistic studies including control experiments, NMR spectroscopy, and X-ray crystallography identified the essential role of the "N-H moiety" of the manganese catalysts and the major reaction intermediates related to the catalytic cycle.

  2. Site-specific DNA transesterification catalyzed by a restriction enzyme.

    PubMed

    Sasnauskas, Giedrius; Connolly, Bernard A; Halford, Stephen E; Siksnys, Virginijus

    2007-02-13

    Most restriction endonucleases use Mg2+ to hydrolyze phosphodiester bonds at specific DNA sites. We show here that BfiI, a metal-independent restriction enzyme from the phospholipase D superfamily, catalyzes both DNA hydrolysis and transesterification reactions at its recognition site. In the presence of alcohols such as ethanol or glycerol, it attaches the alcohol covalently to the 5' terminus of the cleaved DNA. Under certain conditions, the terminal 3'-OH of one DNA strand can attack the target phosphodiester bond in the other strand to create a DNA hairpin. Transesterification reactions on DNA with phosphorothioate linkages at the target bond proceed with retention of stereoconfiguration at the phosphorus, indicating, uniquely for a restriction enzyme, a two-step mechanism. We propose that BfiI first makes a covalent enzyme-DNA intermediate, and then it resolves it by a nucleophilic attack of water or an alcohol, to yield hydrolysis or transesterification products, respectively.

  3. Trypsin-catalyzed oxygen-18 labeling for quantitative proteomics

    SciTech Connect

    Qian, Weijun; Petritis, Brianne O.; Nicora, Carrie D.; Smith, Richard D.

    2011-07-01

    Stable isotope labeling based on relative peptide/protein abundance measurements is commonly applied for quantitative proteomics. Recently, trypsin-catalyzed oxygen-18 labeling has grown in popularity due to its simplicity, cost-effectiveness, and its ability to universally label peptides with high sample recovery. In (18)O labeling, both C-terminal carboxyl group atoms of tryptic peptides can be enzymatically exchanged with (18)O, thus providing the labeled peptide with a 4 Da mass shift from the (16)O-labeled sample. Peptide (18)O labeling is ideally suited for generating a labeled "universal" reference sample used for obtaining accurate and reproducible quantitative measurements across large number of samples in quantitative discovery proteomics.

  4. Mg-catalyzed autoclave synthesis of aligned silicon carbide nanostructures.

    PubMed

    Xi, Guangcheng; Liu, Yankuan; Liu, Xiaoyan; Wang, Xiaoqing; Qian, Yitai

    2006-07-27

    In this article, a novel magnesium-catalyzed co-reduction route was developed for the large-scale synthesis of aligned beta-SiC one-dimensional (1D) nanostructures at relative lower temperature (600 degrees C). By carefully controlling the reagent concentrations, we could synthesize beta-SiC rodlike and needlelike nanostructures. The possible growth mechanism of the as-synthesized beta-SiC 1D nanostructures has been investigated. The structure and morphology of the as-synthesized beta-SiC nanostructures are characterized using X-ray diffraction, Fourier transform infrared absorption, and scanning and transmission electron microscopes. Raman and photoluminescence properties are also investigated at room temperature. The as-synthesized beta-SiC nanostructures exhibit strong shape-dependent field emission properties. Corresponding to their shapes, the as-synthesized nanorods and nanoneedles display the turn-on fields of 12, 8.4, and 1.8 V/microm, respectively.

  5. Pd-Catalyzed Heterocycle Synthesis in Ionic Liquids

    NASA Astrophysics Data System (ADS)

    Li, Jianxiao; Jiang, Huanfeng

    Heterocyclic and fused heterocyclic compounds are ubiquitously found in natural products and biologically interesting molecules, and many currently marketed drugs hold heterocycles as their core structure. In this chapter, recent advances on Pd-catalyzed synthesis of heterocycles in ionic liquids (ILs) are reviewed. In palladium catalysis, ILs with different cations and anions are investigated as an alternative recyclable and environmentally benign reaction medium, and a variety of heterocyclic compounds including cyclic ketals, quinolones, quinolinones, isoindolinones, and lactones are conveniently constructed. Compared to the traditional methods, these new approaches have many advantages, such as environmentally friendly synthetic procedure, easy product and catalyst separation, recyclable medium, which make them have the potential applications in industry.

  6. Calcium-catalyzed pyrolysis of lignocellulosic biomass components.

    PubMed

    Case, Paige A; Truong, Chi; Wheeler, M Clayton; DeSisto, William J

    2015-09-01

    The present study examines the effect of calcium pretreatment on pyrolysis of individual lignocellulosic compounds. Previous work has demonstrated that the incorporation of calcium compounds with the feedstock prior to pyrolysis has a significant effect on the oxygen content and stability of the resulting oil. The aim of this work was to further explore the chemistry of calcium-catalyzed pyrolysis. Bench-scale pyrolysis of biomass constituents, including lignin, cellulose and xylan is performed and compared to the oils produced from pyrolysis of the same components after calcium pretreatment. The resulting oils were analyzed by quantitative GC-MS and SEC. These analyses, together with data collected from previous work provide evidence which was used to develop proposed reaction pathways for pyrolysis of calcium-pretreatment biomass. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Asymmetric Allylboration of Acyl Imines Catalyzed by Chiral Diols

    PubMed Central

    Lou, Sha; Moquist, Philip N.; Schaus, Scott E.

    2008-01-01

    Chiral BINOL-derived diols catalyze the enantioselective asymmetric allylboration of acyl imines. The reaction requires 15 mol% of (S)-3,3′-Ph2-BINOL as the catalyst and allyldiisopropoxyborane as the nucleophile. The reaction products are obtained in good yields (75 – 94%) and high enantiomeric ratios (95:5 – 99.5:0.5) for aromatic and aliphatic imines. High diastereoselectivities (dr > 98:2) and enantioselectivities (er > 98:2) are obtained in the reactions of acyl imines with crotyldiisopropoxyboranes. This asymmetric transformation is directly applied to the synthesis of maraviroc, the selective CCR5 antagonist with potent activity against HIV-1 infection. Mechanistic investigations of the allylboration reaction including IR, NMR, and mass spectrometry study indicate that acyclic boronates are activated by chiral diols via exchange of one of the boronate alkoxy groups with activation of the acyl imine via hydrogen bonding. PMID:18020334

  8. Degradation of Akt using protein-catalyzed capture agents.

    PubMed

    Henning, Ryan K; Varghese, Joseph O; Das, Samir; Nag, Arundhati; Tang, Grace; Tang, Kevin; Sutherland, Alexander M; Heath, James R

    2016-04-01

    Abnormal signaling of the protein kinase Akt has been shown to contribute to human diseases such as diabetes and cancer, but Akt has proven to be a challenging target for drugging. Using iterative in situ click chemistry, we recently developed multiple protein-catalyzed capture (PCC) agents that allosterically modulate Akt enzymatic activity in a protein-based assay. Here, we utilize similar PCCs to exploit endogenous protein degradation pathways. We use the modularity of the anti-Akt PCCs to prepare proteolysis targeting chimeric molecules that are shown to promote the rapid degradation of Akt in live cancer cells. These novel proteolysis targeting chimeric molecules demonstrate that the epitope targeting selectivity of PCCs can be coupled with non-traditional drugging moieties to inhibit challenging targets. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

  9. Guide to Enantioselective Dirhodium(II)-Catalyzed Cyclopropanation with Aryldiazoacetates

    PubMed Central

    Chepiga, Kathryn M.; Qin, Changming; Alford, Joshua S.; Chennamadhavuni, Spandan; Gregg, Timothy M.; Olson, Jeremy P.

    2013-01-01

    Catalytic enantioselective methods for the generation of cyclopropanes has been of longstanding pharmaceutical interest. Chiral dirhodium(II) catalysts prove to be an effective means for the generation of diverse cyclopropane libraries. Rh2(R-DOSP)4 is generaally the most effective catalyst for asymmetric intermolecular cyclopropanation of methyl aryldiazoacetates with styrene. Rh2(S-PTAD)4 provides high levels of enantioinduction with ortho-substituted aryldiazoacetates. The less-established Rh2(R-BNP)4 plays a complementary role to Rh2(R-DOSP)4 and Rh2(S-PTAD)4 in catalyzing highly enantioselective cyclopropanation of 3- methoxy-substituted aryldiazoacetates. Substitution on the styrene has only moderate influence on the asymmetric induction of the cyclopropanation. PMID:24273349

  10. Guide to Enantioselective Dirhodium(II)-Catalyzed Cyclopropanation with Aryldiazoacetates.

    PubMed

    Chepiga, Kathryn M; Qin, Changming; Alford, Joshua S; Chennamadhavuni, Spandan; Gregg, Timothy M; Olson, Jeremy P; Davies, Huw M L

    2013-07-08

    Catalytic enantioselective methods for the generation of cyclopropanes has been of longstanding pharmaceutical interest. Chiral dirhodium(II) catalysts prove to be an effective means for the generation of diverse cyclopropane libraries. Rh2(R-DOSP)4 is generaally the most effective catalyst for asymmetric intermolecular cyclopropanation of methyl aryldiazoacetates with styrene. Rh2(S-PTAD)4 provides high levels of enantioinduction with ortho-substituted aryldiazoacetates. The less-established Rh2(R-BNP)4 plays a complementary role to Rh2(R-DOSP)4 and Rh2(S-PTAD)4 in catalyzing highly enantioselective cyclopropanation of 3- methoxy-substituted aryldiazoacetates. Substitution on the styrene has only moderate influence on the asymmetric induction of the cyclopropanation.

  11. Experimental investigation of muon-catalyzed t + t fusion

    SciTech Connect

    Bogdanova, L. N.; Bom, V. R.; Demin, A. M.; Demin, D. L.; Eijk, C. W. E. van; Filchagin, S. V.; Filchenkov, V. V.; Grafov, N. N. Grishechkin, S. K.; Gritsaj, K. I.; Konin, A. D.; Kuryakin, A. V.; Medved', S. V.; Musyaev, R. K.; Rudenko, A. I.; Tumkin, D. P.; Vinogradov, Yu. I.; Yukhimchuk, A. A.; Yukhimchuk, S. A.; Zinov, V. G.

    2009-02-15

    The muon-catalyzed fusion ({mu}CF) process in tritium was studied by the {mu}CF collaboration on the muon beam of the JINR Phasotron. The measurements were carried out with a liquid tritium target at the temperature 22 K and density approximately 1.25 of the liquid hydrogen density (LHD). Parameters of the {mu}CF cycle were determined: the tt{mu} muonic molecule formation rate {lambda}{sub tt{mu}} = 2.84(0.32) {mu}s{sup -1}, the tt{mu} fusion reaction rate {lambda}{sub f} = 15.6(2.0) {mu}s{sup -1}, and the probability of muon sticking to helium {omega}{sub tt}= 13.9(1.5)%. The results agree with those obtained earlier by other groups, but better accuracy was achieved due to our unique experimental method.

  12. Rhenium-catalyzed deoxydehydration of diols and polyols.

    PubMed

    Dethlefsen, Johannes R; Fristrup, Peter

    2015-03-01

    The substitution of platform chemicals of fossil origin by biomass-derived analogues requires the development of chemical transformations capable of reducing the very high oxygen content of biomass. One such reaction, which has received increasing attention within the past five years, is the rhenium-catalyzed deoxydehydration (DODH) of a vicinal diol into an alkene; this is a model system for abundant polyols like glycerol and sugar alcohols. The present contribution includes a review of early investigations of stoichiometric reactions involving rhenium, diols, and alkenes followed by a discussion of the various catalytic systems that have been developed with emphasis on the nature of the reductant, the substrate scope, and mechanistic investigations. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Rh(II)-Catalyzed Reactions of Diazoesters with Organozinc Reagents.

    PubMed

    Panish, Robert; Selvaraj, Ramajeyam; Fox, Joseph M

    2015-08-21

    Rh(II)-catalyzed reactions of diazoesters with organozinc reagents are described. Diorganozinc reagents participate in reactions with diazo compounds by two distinct, catalyst-dependent mechanisms. With bulky diisopropylethyl acetate ligands, the reaction mechanism is proposed to involve initial formation of a Rh-carbene and subsequent carbozincation to give a zinc enolate. With Rh2(OAc)4, it is proposed that initial formation of an azine precedes 1,2-addition by an organozinc reagent. This straightforward route to the hydrazone products provides a useful method for preparing chiral quaternary α-aminoesters or pyrazoles via the Paul-Knorr condensation with 1,3-diketones. Crossover and deuterium labeling experiments provide evidence for the mechanisms proposed.

  14. WILDCAT: a catalyzed D-D tokamak reactor

    SciTech Connect

    Evans, K. Jr.; Baker, C.C.; Brooks, J.N.

    1981-11-01

    WILDCAT is a conceptual design of a catalyzed D-D, tokamak, commercial, fusion reactor. WILDCAT utilizes the beneficial features of no tritium breeding, while not extrapolating unnecessarily from existing D-T designs. The reactor is larger and has higher magnetic fields and plasma pressures than typical D-T devices. It is more costly, but eliminates problems associated with tritium breeding and has tritium inventories and throughputs approximately two orders of magnitude less than typical D-T reactors. There are both a steady-state version with Alfven-wave current drive and a pulsed version. Extensive comparison with D-T devices has been made, and cost and safety analyses have been included. All of the major reactor systems have been worked out to a level of detail appropriate to a complete, conceptual design.

  15. Homogeneously catalyzed oxidation for the destruction of aqueous organic wastes

    SciTech Connect

    Leavitt, D.D.; Horbath, J.S.; Abraham, M.A. )

    1990-11-01

    Several organic species, specifically atrazine, 2,4-dichlorophenozyacetic acid, and biphenyl, were converted to CO{sub 2} and other non-harmful gases through oxidation catalyzed by inorganic acid. Nearly complete conversion was obtained through homogeneous liquid-phase oxidation with ammonium nitrate. The kinetics of reaction have been investigated and indicate parallel oxidation and thermal degradation of the oxidant. This results in a maximum conversion at an intermediate temperature. Increasing oxidant concentration accelerates the rate of conversion and shifts the location of the optimum temperature. Reaction at varying acid concentration revealed that conversion increased with an approximately linear relationship as the pH of the solution was increased. Conversion was increased to greater than 99% through the addition of small amounts of transition metal salts demonstrating the suitability of a treatment process based on this technology for wastestreams containing small quantities of heavy metals.

  16. Transition Metals Catalyzed Element-Cyano Bonds Activations

    PubMed Central

    Wang, Rui; Falck, John R.

    2014-01-01

    Cyano group as a versatile functionalized intermediate has been explored for several decades, as it readily transfers to many useful functionalization groups such as amine, amide, acid, etc., which make it possess high popularization and use value in organic synthesis. Reactions involved with element-cyano bond cleavage can provide not only a new cyano group but also a freshly functionalized skeleton in one-pot, consequently making it of high importance. The highlights reviewed herein include H-CN, Si-CN, C-CN, B-CN, Sn-CN, Ge-CN, S-CN, Halo-CN, N-CN, and O-CN bonds cleavages and will summarize progress in such an important research area. This review article will focus on transition metal catalyzed reactions involving element-cyano bond activation. PMID:25558119

  17. Lipase-catalyzed ethanolysis of borage oil: a kinetic study.

    PubMed

    Torres, Carlos F; Hill, Charles G; Otero, Cristina

    2004-01-01

    Ethanolysis of borage oil catalyzed by two commercial lipases (from Pseudomonas cepacia and Candida antarctica) was studied using two different methodologies. Multiresponse models derived from a generalized Michaelis-Menten mechanism were utilized to describe the rates of formation of ethyl esters of the primary fatty acids present in the precursor oil. The relative rate constants determined for each of the fatty acid residues indicated that both lipases discriminate against release of gamma-linolenic acid residues under the reaction conditions studied. However, both lipases also released some of the residues located at the sn-2 position, indicating that for the experimental conditions studied, both lipases are nonspecific. Moreover, inactivation of Novozym 435 was rapid. Because the half-life of this enzyme (ca. 2.2 h) is comparable to the half-life of the reaction, the intrinsic reaction rate and enzyme deactivation must both be considered in modeling the kinetics.

  18. Urea- and Thiourea-Catalyzed Aminolysis of Carbonates.

    PubMed

    Blain, Marine; Yau, Honman; Jean-Gérard, Ludivine; Auvergne, Rémi; Benazet, Dominique; Schreiner, Peter R; Caillol, Sylvain; Andrioletti, Bruno

    2016-08-23

    The aminolysis of (poly)carbonates by (poly)amines provides access to non-isocyanate polyurethanes (NIPUs) that are toxic-reagent-free analogues of polyurethanes (PUs). Owing to their low reactivity, the ring opening of cyclic carbonates requires the use of a catalyst. Herein, we report that the more available and cheaper ureas could advantageously be used for catalyzing the formation of NIPUs at the expense of the thiourea analogues. In addition, we demonstrate a medium-range pKa of the (thio)urea and an unqeual substitution pattern is critical for controlling the efficiency of the carbonate opening. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Secondary kinase reactions catalyzed by yeast pyruvate kinase.

    PubMed

    Leblond, D J; Robinson, J L

    1976-06-07

    1. Yeast pyruvate kinase (EC 2.7.1.40) catalyzes, in addition to the primary, physiologically important reaction, three secondary kinase reactions, the ATP-dependent phosphorylations of fluoride (fluorokinase), hydroxylamine (hydroxylamine kinase) and glycolate (glycolate kinase). 2. These reactions are accelerated by fructose-1,6-bisphosphate, the allosteric activator of the primary reaction. Wth Mg2+ as the required divalent cation, none of these reactions are observed in the absence of fructose-biphosphate. With Mn2+, fructose-bisphosphate is required for the glycolate kinase reaction, but merely stimulates the other reactions. 3. The effect of other divalent cations and pH on three secondary kinase reactions was also examined. 4. Results are compared with those obtained from muscle pyruvate kinase and the implications of the results for the mechanism of the yeast enzyme are discussed.

  20. Enantioselective copper-catalyzed carboetherification of unactivated alkenes.

    PubMed

    Bovino, Michael T; Liwosz, Timothy W; Kendel, Nicole E; Miller, Yan; Tyminska, Nina; Zurek, Eva; Chemler, Sherry R

    2014-06-16

    Chiral saturated oxygen heterocycles are important components of bioactive compounds. Cyclization of alcohols onto pendant alkenes is a direct route to their synthesis, but few catalytic enantioselective methods enabling cyclization onto unactivated alkenes exist. Herein reported is a highly efficient copper-catalyzed cyclization of γ-unsaturated pentenols which terminates in C-C bond formation, a net alkene carboetherification. Both intra- and intermolecular C-C bond formations are demonstrated, thus yielding functionalized chiral tetrahydrofurans as well as fused-ring and bridged-ring oxabicyclic products. Transition-state calculations support a cis-oxycupration stereochemistry-determining step. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.