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Sample records for abeta oligomers show

  1. Alzheimer's-associated A{beta} oligomers show altered structure, immunoreactivity and synaptotoxicity with low doses of oleocanthal

    SciTech Connect

    Pitt, Jason Roth, William; Lacor, Pascale; Smith, Amos B.; Blankenship, Matthew; Velasco, Pauline; De Felice, Fernanda; Breslin, Paul Klein, William L.

    2009-10-15

    It now appears likely that soluble oligomers of amyloid-{beta}{sub 1-42} peptide, rather than insoluble fibrils, act as the primary neurotoxin in Alzheimer's disease (AD). Consequently, compounds capable of altering the assembly state of these oligomers (referred to as ADDLs) may have potential for AD therapeutics. Phenolic compounds are of particular interest for their ability to disrupt A{beta} oligomerization and reduce pathogenicity. This study has focused on oleocanthal (OC), a naturally-occurring phenolic compound found in extra-virgin olive oil. OC increased the immunoreactivity of soluble A{beta} species, when assayed with both sequence- and conformation-specific A{beta} antibodies, indicating changes in oligomer structure. Analysis of oligomers in the presence of OC showed an upward shift in MW and a ladder-like distribution of SDS-stable ADDL subspecies. In comparison with control ADDLs, oligomers formed in the presence of OC (A{beta}-OC) showed equivalent colocalization at synapses but exhibited greater immunofluorescence as a result of increased antibody recognition. The enhanced signal at synapses was not due to increased synaptic binding, as direct detection of fluorescently-labeled ADDLs showed an overall reduction in ADDL signal in the presence of OC. Decreased binding to synapses was accompanied by significantly less synaptic deterioration assayed by drebrin loss. Additionally, treatment with OC improved antibody clearance of ADDLs. These results indicate oleocanthal is capable of altering the oligomerization state of ADDLs while protecting neurons from the synaptopathological effects of ADDLs and suggest OC as a lead compound for development in AD therapeutics.

  2. Polyalanine and Abeta Aggregation Kinetics: Probing Intermediate Oligomer Formation and Structure Using Computer Simulations

    NASA Astrophysics Data System (ADS)

    Phelps, Erin Melissa

    2011-12-01

    The aggregation of proteins into stable, well-ordered structures known as amyloid fibrils has been associated with many neurodegenerative diseases. Amyloid fibrils are long straight, and un-branched structures containing several proto-filaments, each of which exhibits "cross beta structure," -- ribbon-like layers of large beta sheets whose strands run perpendicular to the fibril axis. It has been suggested in the literature that the pathway to fibril formation has the following steps: unfolded monomers associate into transient unstable oligomers, the oligomers undergo a rearrangement into the cross-beta structure and form into proto-filaments, these proto-filaments then associate and grow into fully formed fibrils. Recent experimental studies have determined that the unstable intermediate structures are toxic to cells and that their presence may play a key role in the pathogenesis of the amyloid diseases. Many efforts have been made to determine the structure of intermediate oligomer aggregates that form during the fibrillization process. The goal of this work is to provide details about the structure and formation kinetics of the unstable oligomers that appear in the fibril formation pathway. The specific aims of this work are to determine the steps in the fibril formation pathway and how the kinetics of fibrillization changes with variations in temperature and concentration. The method used is the application of discontinuous molecular dynamics to large systems of peptides represented with an intermediate resolution model, PRIME, that was previously developed in our group. Three different peptide sequences are simulated: polyalanine (KA14K), Abeta17-40, and Abeta17-42; the latter two are truncated sequences of the Alzheimer's peptide. We simulate the spontaneous assembly of these peptide chains from a random initial configuration of random coils. We investigate aggregation kinetics and oligomer formation of a system of 192 polyalanine (KA14K) chains over a

  3. Ellagic acid promotes A{beta}42 fibrillization and inhibits A{beta}42-induced neurotoxicity

    SciTech Connect

    Feng, Ying; Yang, Shi-gao; Du, Xue-ting; Zhang, Xi; Sun, Xiao-xia; Zhao, Min; Sun, Gui-yuan; Liu, Rui-tian

    2009-12-25

    Smaller, soluble oligomers of {beta}-amyloid (A{beta}) play a critical role in the pathogenesis of Alzheimer's disease (AD). Selective inhibition of A{beta} oligomer formation provides an optimum target for AD therapy. Some polyphenols have potent anti-amyloidogenic activities and protect against A{beta} neurotoxicity. Here, we tested the effects of ellagic acid (EA), a polyphenolic compound, on A{beta}42 aggregation and neurotoxicity in vitro. EA promoted A{beta} fibril formation and significant oligomer loss, contrary to previous results that polyphenols inhibited A{beta} aggregation. The results of transmission electron microscopy (TEM) and Western blot displayed more fibrils in A{beta}42 samples co-incubated with EA in earlier phases of aggregation. Consistent with the hypothesis that plaque formation may represent a protective mechanism in which the body sequesters toxic A{beta} aggregates to render them harmless, our MTT results showed that EA could significantly reduce A{beta}42-induced neurotoxicity toward SH-SY5Y cells. Taken together, our results suggest that EA, an active ingredient in many fruits and nuts, may have therapeutic potential in AD.

  4. Spontaneous Formation of Oligomers and Fibrils in Large-Scale Molecular Dynamics Simulations of A-beta Peptides

    NASA Astrophysics Data System (ADS)

    Hall, Carol

    2013-03-01

    Protein aggregation is associated with serious and eventually-fatal neurodegenerative diseases including Alzheimer's and Parkinson's. While atomic resolution molecular dynamics simulations have been useful in this regard, they are limited to examination of either oligomer formation by a small number of peptides or analysis of the stability of a moderate number of peptides placed in trial or known experimental structures. We describe large scale intermediate-resolution molecular dynamics simulations of the spontaneous formation of fibrils by systems containing large numbers (48) of peptides including A-beta (16-22), and A-beta (17-42) peptides. We trace out the aggregation process from an initial configuration of random coils to proto-filaments with cross- β structures and demonstrate how kinetics dictates the structural details of the fully formed fibril. Fibrillization kinetics depends strongly on the temperature. Nucleation and templated growth via monomer addition occur at and near a transition temperature above which fibrils are unlikely to form. Oligomeric merging and structural rearrangement are observed at lower temperatures. In collaboration with Mookyung Cheon, Iksoo Chang, Pusan University; and David Latshaw, North Carolina State University.

  5. Stability and structure of oligomers of the Alzheimer peptide Abeta16-22: from the dimer to the 32-mer.

    PubMed

    Röhrig, Ute F; Laio, Alessandro; Tantalo, Nazario; Parrinello, Michele; Petronzio, Roberto

    2006-11-01

    Several neurodegenerative diseases such as Alzheimer's, Parkinson's, and Huntington's diseases are associated with amyloid fibrils formed by different polypeptides. We probe the structure and stability of oligomers of different sizes of the fragment Abeta(16-22) of the Alzheimer beta-amyloid peptide using atomic-detail molecular dynamics simulations with explicit solvent. We find that only large oligomers form a stable beta-sheet aggregate, the minimum nucleus size being of the order of 8-16 peptides. This effect is attributed to better hydrophobic contacts and a better shielding of backbone-backbone hydrogen bonds from the solvent in bigger assemblies. Moreover, the observed stability of beta-sheet aggregates with a different number of layers can be explained on the basis of their solvent-accessible surface area. Depending on the stacking interface between the sheets, we observe straight or twisted structures, which could be linked to the experimentally observed polymorphism of amyloid fibrils. To compare our 32-mer structure to experimental data, we calculate its x-ray diffraction pattern. Good agreement is found between experimentally and theoretically determined reflections, suggesting that our model indeed closely resembles the structures found in vitro. PMID:16920832

  6. Key residues for the oligomerization of A{beta}42 protein in Alzheimer's disease

    SciTech Connect

    Ngo, Sam; Guo, Zhefeng

    2011-10-28

    Highlights: Black-Right-Pointing-Pointer A{beta} oligomers are neurotoxins and likely the causing agents for Alzheimer's disease. Black-Right-Pointing-Pointer A{beta}42 fusion protein form globular oligomers. Black-Right-Pointing-Pointer A{beta}42 fusion protein oligomers contain SDS-resistant tetramers and hexamers. Black-Right-Pointing-Pointer Cysteine substitutions at residues 31, 32, 34, 39-41 disrupt A{beta}42 oligomerization. -- Abstract: Deposition of amyloid fibrils consisting of amyloid {beta} (A{beta}) protein as senile plaques in the brain is a pathological hallmark of Alzheimer's disease. However, a growing body of evidence shows that soluble A{beta} oligomers correlate better with dementia than fibrils, suggesting that A{beta} oligomers may be the primary toxic species. The structure and oligomerization mechanism of these A{beta} oligomers are crucial for developing effective therapeutics. Here we investigated the oligomerization of A{beta}42 in the context of a fusion protein containing GroES and ubiquitin fused to the N-terminus of A{beta} sequence. The presence of fusion protein partners, in combination with a denaturing buffer containing 8 M urea at pH 10, is unfavorable for A{beta}42 aggregation, thus allowing only the most stable structures to be observed. Transmission electron microscopy showed that A{beta}42 fusion protein formed globular oligomers, which bound weakly to thioflavin T and Congo red. SDS-PAGE shows that A{beta}42 fusion protein formed SDS-resistant hexamers and tetramers. In contrast, A{beta}40 fusion protein remained as monomers on SDS gel, suggesting that the oligomerization of A{beta}42 fusion protein is not due to the fusion protein partners. Cysteine scanning mutagenesis at 22 residue positions further revealed that single cysteine substitutions of the C-terminal hydrophobic residues (I31, I32, L34, V39, V40, and I41) led to disruption of hexamer and tetramer formation, suggesting that hydrophobic interactions between these

  7. Microwave-assisted click polymerization for the synthesis of Abeta(16-22) cyclic oligomers and their self-assembly into polymorphous aggregates.

    PubMed

    Elgersma, Ronald C; van Dijk, Maarten; Dechesne, Annemarie C; van Nostrum, Cornelus F; Hennink, Wim E; Rijkers, Dirk T S; Liskamp, Rob M J

    2009-11-01

    We report on the design, synthesis, and structural analysis of cyclic oligomers with an amyloidogenic peptide sequence as the repeating unit to obtain novel self-assembling bionanomaterials. The peptide was derived from the Alzheimer Abeta(16-22) sequence since its strong tendency to form antiparallel beta-sheets ensured the formation of intermolecular hydrogen bridges on which the supramolecular assembly of the individual cyclic oligomers was based. The synthesis of the cyclic oligomers was performed via a microwave-assisted Cu(I)-catalyzed 1,3-dipolar cycloaddition reaction of azido-Lys-Leu-Val-Phe-Phe-Ala-Glu-propargyl amide as the monomer. The formation of cyclic oligomers, up to pentamers (35 amino acid residues), was verified by MALDI-TOF analysis and the individual cyclic monomer and dimer could be isolated by HPLC. Gelation behavior and the self-assembly of the linear monomer and the cyclic monomer and dimer were studied by TEM, FTIR and CD. Significant differences were observed in the morphology of the supramolecular aggregates of these three peptides that could be explained by alterations of the hydrogen bond network. PMID:19830304

  8. Unique physicochemical profile of beta-amyloid peptide variant Abeta1-40E22G protofibrils: conceivable neuropathogen in arctic mutant carriers.

    PubMed

    Päiviö, A; Jarvet, J; Gräslund, A; Lannfelt, L; Westlind-Danielsson, A

    2004-05-21

    A new early-onset form of Alzheimer's disease (AD) was described recently where a point mutation was discovered in codon 693 of the beta-amyloid (Abeta) precursor protein gene, the Arctic mutation. The mutation translates into a single amino acid substitution, glutamic acid-->glycine, in position 22 of the Abeta peptide. The mutation carriers have lower plasma levels of Abeta than normal, while in vitro studies show that Abeta1-40E22G protofibril formation is significantly enhanced. We have explored the nature of the Abeta1-40E22G peptide in more detail, in particular the protofibrils. Using size-exclusion chromatography (SEC) and circular dichroism spectroscopy (CD) kinetic and secondary structural characteristics were compared with other Abeta1-40 peptides and the Abeta12-28 fragment, all having single amino acid substitutions in position 22. We have found that Abeta1-40E22G protofibrils are a group of comparatively stabile beta-sheet-containing oligomers with a heterogeneous size distribution, ranging from >100 kDa to >3000 kDa. Small Abeta1-40E22G protofibrils are generated about 400 times faster than large ones. Salt promotes their formation, which significantly exceeds all the other peptides studied here, including the Dutch mutation Abeta1-40E22Q. Position 22 substitutions had significant effects on aggregation kinetics of Abeta1-40 and in Abeta12-28, although the qualitative aspects of the effects differed between the native peptide and the fragment, as no protofibrils were formed by the fragments. The rank order of protofibril formation of Abeta1-40 and its variants was the same as the rank order of the length of the nucleation/lag phase of the Abeta12-28 fragments, E22V>E22A?E22G>E22Q?E22, and correlated with the degree of hydrophobicity of the position 22 substituent. The molecular mass of peptide monomers and protofibrils were estimated better in SEC studies using linear rather than globular calibration standards. The characteristics of the Abeta1-40E22

  9. Overcoming synthetic Abeta peptide aging: a new approach to an age-old problem.

    PubMed

    Manzoni, Claudia; Colombo, Laura; Messa, Massimo; Cagnotto, Alfredo; Cantù, Laura; Del Favero, Elena; Salmona, Mario

    2009-01-01

    Investigations of amyloidogenic diseases use synthetic peptides for cell-free and in vitro studies. However, amyloidogenic peptides often show intrinsic variability that markedly affects the reproducibility of experiments. Proof of physicochemical and biological variability with different batches of amyloidogenic peptides have been reported in literature. Here, we show that differences can be observed even within the same batch of Abeta1-42 peptide after storing lyophilised samples at -20 degrees C. This change (referred to as 'peptide aging') was reproduced with Abeta1-40 peptide samples by using a series of lyophilisation cycles, showing that lyophilisation, rather than preserving the physicochemical and biological features of Abeta peptides, introduces wide variability. To counteract synthetic peptide aging, we set up a procedure involving the sequential use of trifluoroacetic acid, formic acid and sodium hydroxide solutions that disaggregate preformed seeds and enriched Abeta peptide solutions into monomers and low-molecular-weight oligomers. This procedure enabled us to obtain reproducible physicochemical and biological features of Abeta peptides, irrespective of their age. PMID:20536398

  10. Stability of the transthyretin molecule as a key factor in the interaction with a-beta peptide--relevance in Alzheimer's disease.

    PubMed

    Ribeiro, Carlos A; Saraiva, Maria João; Cardoso, Isabel

    2012-01-01

    Transthyretin (TTR) protects against A-Beta toxicity by binding the peptide thus inhibiting its aggregation. Previous work showed different TTR mutations interact differently with A-Beta, with increasing affinities correlating with decreasing amyloidogenecity of the TTR mutant; this did not impact on the levels of inhibition of A-Beta aggregation, as assessed by transmission electron microscopy. Our work aimed at probing differences in binding to A-Beta by WT, T119M and L55P TTR using quantitative assays, and at identifying factors affecting this interaction. We addressed the impact of such factors in TTR ability to degrade A-Beta. Using a dot blot approach with the anti-oligomeric antibody A11, we showed that A-Beta formed oligomers transiently, indicating aggregation and fibril formation, whereas in the presence of WT and T119M TTR the oligomers persisted longer, indicative that these variants avoided further aggregation into fibrils. In contrast, L55PTTR was not able to inhibit oligomerization or to prevent evolution to aggregates and fibrils. Furthermore, apoptosis assessment showed WT and T119M TTR were able to protect against A-Beta toxicity. Because the amyloidogenic potential of TTR is inversely correlated with its stability, the use of drugs able to stabilize TTR tetrameric fold could result in increased TTR/A-Beta binding. Here we showed that iododiflunisal, 3-dinitrophenol, resveratrol, [2-(3,5-dichlorophenyl)amino] (DCPA) and [4-(3,5-difluorophenyl)] (DFPB) were able to increase TTR binding to A-Beta; however only DCPA and DFPB improved TTR proteolytic activity. Thyroxine, a TTR ligand, did not influence TTR/A-Beta interaction and A-Beta degradation by TTR, whereas RBP, another TTR ligand, not only obstructed the interaction but also inhibited TTR proteolytic activity. Our results showed differences between WT and T119M TTR, and L55PTTR mutant regarding their interaction with A-Beta and prompt the stability of TTR as a key factor in this interaction

  11. Human plasma contains cross-reactive Abeta conformer-specific IgG antibodies.

    PubMed

    O'Nuallain, Brian; Acero, Luis; Williams, Angela D; Koeppen, Helen P McWilliams; Weber, Alfred; Schwarz, Hans P; Wall, Jonathan S; Weiss, Deborah T; Solomon, Alan

    2008-11-25

    Two conformers of aggregated Abeta, i.e., fibrils and oligomers, have been deemed important in the pathogenesis of Alzheimer's disease. We now report that intravenous immune globulin (IVIG) derived from pools of human plasma contains IgGs that recognize conformational epitopes present on fibrils and oligomers, but not their soluble monomeric precursor. We have used affinity chromatography to isolate these antibodies and have shown that they cross-reacted with comparable nanomolar avidity with both types of Abeta aggregates; notably, binding was not inhibited by soluble Abeta monomers. Our studies provide further support for investigating the therapeutic use of IVIG in Alzheimer's disease. PMID:18956886

  12. Immunodominant epitope and properties of pyroglutamate-modified Abeta-specific antibodies produced in rabbits.

    PubMed

    Acero, G; Manoutcharian, K; Vasilevko, V; Munguia, M E; Govezensky, T; Coronas, G; Luz-Madrigal, A; Cribbs, D H; Gevorkian, G

    2009-08-18

    N-truncated and N-modified forms of amyloid beta (Abeta) peptide are found in diffused and dense core plaques in Alzheimer's disease (AD) and Down's syndrome patients as well as transgenic mouse models of AD. Although the pathological significance of these shortened forms Abeta is not completely understood, previous studies have demonstrated that these peptides are significantly more resistant to degradation, aggregate more rapidly in vitro and exhibit similar or, in some cases, increased toxicity in hippocampal neuronal cultures compared to the full length peptides. In the present study we further investigated the mechanisms of toxicity of one of the most abundant N-truncated/modified Abeta peptide bearing amino-terminal pyroglutamate at position 3 (AbetaN3(pE)). We demonstrated that AbetaN3(pE) oligomers induce phosphatidyl serine externalization and membrane damage in SH-SY5Y cells. Also, we produced AbetaN3(pE)-specific polyclonal antibodies in rabbit and identified an immunodominant epitope recognized by anti-AbetaN3(pE) antibodies. Our results are important for developing new immunotherapeutic compounds specifically targeting AbetaN3(pE) aggregates since the most commonly used immunogens in the majority of vaccines for AD have been shown to induce antibodies that recognize the N-terminal immunodominant epitope (EFRH) of the full length Abeta, which is absent in N-amino truncated peptides. PMID:19545911

  13. Synthetic amyloid-beta oligomers impair long-term memory independently of cellular prion protein.

    PubMed

    Balducci, Claudia; Beeg, Marten; Stravalaci, Matteo; Bastone, Antonio; Sclip, Alessandra; Biasini, Emiliano; Tapella, Laura; Colombo, Laura; Manzoni, Claudia; Borsello, Tiziana; Chiesa, Roberto; Gobbi, Marco; Salmona, Mario; Forloni, Gianluigi

    2010-02-01

    Inability to form new memories is an early clinical sign of Alzheimer's disease (AD). There is ample evidence that the amyloid-beta (Abeta) peptide plays a key role in the pathogenesis of this disorder. Soluble, bio-derived oligomers of Abeta are proposed as the key mediators of synaptic and cognitive dysfunction, but more tractable models of Abeta-mediated cognitive impairment are needed. Here we report that, in mice, acute intracerebroventricular injections of synthetic Abeta(1-42) oligomers impaired consolidation of the long-term recognition memory, whereas mature Abeta(1-42) fibrils and freshly dissolved peptide did not. The deficit induced by oligomers was reversible and was prevented by an anti-Abeta antibody. It has been suggested that the cellular prion protein (PrP(C)) mediates the impairment of synaptic plasticity induced by Abeta. We confirmed that Abeta(1-42) oligomers interact with PrP(C), with nanomolar affinity. However, PrP-expressing and PrP knock-out mice were equally susceptible to this impairment. These data suggest that Abeta(1-42) oligomers are responsible for cognitive impairment in AD and that PrP(C) is not required. PMID:20133875

  14. Dopamine-induced α-synuclein oligomers show self- and cross-propagation properties

    PubMed Central

    Planchard, Matthew S; Exley, Sarah E; Morgan, Sarah E; Rangachari, Vijayaraghavan

    2014-01-01

    Amyloid aggregates of α-synuclein (αS) protein are the predominant species present within the intracellular inclusions called Lewy bodies in Parkinson’s disease (PD) patients. Among various aggregates, the low-molecular weight ones broadly ranging between 2 and 30 mers are known to be the primary neurotoxic agents responsible for the impairment of neuronal function. Recent research has indicated that the neurotransmitter dopamine (DA) is one of the key physiological agents promoting and augmenting αS aggregation, which is thought to be a significant event in PD pathologenesis. Specifically, DA is known to induce the formation of soluble oligomers of αS, which in turn are responsible for inducing several important cellular changes leading to cellular toxicity. In this report, we present the generation, isolation, and biophysical characterization of five different dopamine-derived αS oligomers (DSOs) ranging between 3 and 15 mers, corroborating previously published reports. More importantly, we establish that these DSOs are also capable of replication by self-propagation, which leads to the replication of DSOs upon interaction with αS monomers, a process similar to that observed in mammilian prions. In addition, DSOs are also able to cross-propagate amyloid-β (Aβ) aggregates involved in Alzheimer’s disease (AD). Interestingly, while self-propagation of DSOs occur with no net gain in protein structure, cross-propagation proceeds with an overall gain in β-sheet conformation. These results implicate the involvement of DSOs in the progression of PD, and, in part, provide a molecular basis for the observed co-existence of AD-like pathology among PD patients. PMID:25044276

  15. Oligomerization and toxicity of A{beta} fusion proteins

    SciTech Connect

    Caine, Joanne M.; Bharadwaj, Prashant R.; Sankovich, Sonia E.; Ciccotosto, Giuseppe D.; Streltsov, Victor A.; Varghese, Jose

    2011-06-10

    Highlights: {yields} We expressed amyloid-{beta} (A{beta}) peptide as a soluble maltose binding protein fusion (MBP-A{beta}42 and MBP-A{beta}16). {yields} The full length A{beta} peptide fusion, MBP-A{beta}42, forms oligomeric species as determined by SDS-PAGE gels, gel filtration and DLS. {yields} The MBP-A{beta}42, but not MBP-A{beta}16 or MBP alone, is toxic to both yeast and mammalian cells as determined by toxicity assays. -- Abstract: This study has found that the Maltose binding protein A{beta}42 fusion protein (MBP-A{beta}42) forms soluble oligomers while the shorter MBP-A{beta}16 fusion and control MBP did not. MBP-A{beta}42, but neither MBP-A{beta}16 nor control MBP, was toxic in a dose-dependent manner in both yeast and primary cortical neuronal cells. This study demonstrates the potential utility of MBP-A{beta}42 as a reagent for drug screening assays in yeast and neuronal cell cultures and as a candidate for further A{beta}42 characterization.

  16. The tumor suppressor PP2A Abeta regulates the RalA GTPase.

    PubMed

    Sablina, Anna A; Chen, Wen; Arroyo, Jason D; Corral, Laura; Hector, Melissa; Bulmer, Sara E; DeCaprio, James A; Hahn, William C

    2007-06-01

    The serine-threonine protein phosphatase 2A (PP2A) is a heterotrimeric enzyme family that regulates numerous signaling pathways. Biallelic mutations of the structural PP2A Abeta subunit occur in several types of human tumors; however, the functional consequences of these cancer-associated PP2A Abeta mutations in cell transformation remain undefined. Here we show that suppression of PP2A Abeta expression permits immortalized human cells to achieve a tumorigenic state. Cancer-associated Abeta mutants fail to reverse tumorigenic phenotype induced by PP2A Abeta suppression, indicating that these mutants function as null alleles. Wild-type PP2A Abeta but not cancer-derived Abeta mutants form a complex with the small GTPase RalA. PP2A Abeta-containing complexes dephosphorylate RalA at Ser183 and Ser194, inactivating RalA and abolishing its transforming function. These observations identify PP2A Abeta as a tumor suppressor gene that transforms immortalized human cells by regulating the function of RalA. PMID:17540176

  17. Pretargeting in tumored mice with radiolabeled morpholino oligomer showing low kidney uptake.

    PubMed

    Liu, Guozheng; He, Jiang; Dou, Shuping; Gupta, Suresh; Vanderheyden, Jean-Luc; Rusckowski, Mary; Hnatowich, Donald J

    2004-03-01

    We have recently shown that accumulation in mouse kidneys of technetium-99m labeled phosphorodiamidate morpholinos (MORFs) increases with the number of cytosines in the base sequence. To improve tumor/kidney ratios in tumored mice, pretargeting studies were performed with a cytosine-free MORF. An 18-mer MORF (5'-TCTTCTACTTCACAACTA) was conjugated to the anti-CEA antibody MN14 (Immunomedics) and administered to nude mice bearing LS174T tumors. Thereafter, the (99m)Tc-labeled cytosine-free cMORF (5'-TAGTTGTGAAGTAGAAGA-amide-MAG(3)) was administered. For comparison, the identical study was repeated but with our original pair of 18-mer MORFs (5'-GGGTGTACGTCACAACTA-conjugated MN14 and (99m)Tc-labeled 5'-TAGTTGTGACGTACACCC-amide-MAG(3)). Surface plasmon resonance was used to show that the hybridization affinities of the original and the modified pair of MORFs were essentially equal. Hybridization of the cytosine-free cMORF-(99m)Tc to MN14-MORF was demonstrated in vitro by size-exclusion high-performance liquid chromatography. At 3 h, kidney levels in normal mice were 2.0%ID/organ for the modified cMORF vs. 4.1%ID/organ for the original cMORF sequence, while at 24 h, these values were 0.9% vs 1.8%ID/organ. Pretargeting studies in tumored mice receiving 25 microg of conjugated antibody, 0.5 microg of labeled cMORF 48 h later, followed by imaging and sacrifice at 3 h showed that kidney levels were reduced using the cytosine-free cMORF. Moreover, tumor accumulation was about 3.6%ID/g and was independent of sequence. The whole-body images clearly reflected the improved tumor to kidney ratios. By choosing a cytosine-free base sequence for pretargeting studies, kidney accumulation of cMORF-(99m)Tc was reduced without adversely influencing tumor accumulation. The lowering of kidney radioactivity levels in this way may be important to reduce toxicity to this organ in connection with pretargeting radiotherapy studies. PMID:14691611

  18. Plasma antibodies to Abeta40 and Abeta42 in patients with Alzheimer's disease and normal controls.

    PubMed

    Xu, Wuhua; Kawarabayashi, Takeshi; Matsubara, Etsuro; Deguchi, Kentaro; Murakami, Tetsuro; Harigaya, Yasuo; Ikeda, Masaki; Amari, Masakuni; Kuwano, Ryozo; Abe, Koji; Shoji, Mikio

    2008-07-11

    Antibodies to amyloid beta protein (Abeta) are present naturally or after Abeta vaccine therapy in human plasma. To clarify their clinical role, we examined plasma samples from 113 patients with Alzheimer's disease (AD) and 205 normal controls using the tissue amyloid plaque immunoreactivity (TAPIR) assay. A high positive rate of TAPIR was revealed in AD (45.1%) and age-matched controls (41.2%), however, no significance was observed. No significant difference was observed in the MMS score or disease duration between TAPIR-positive and negative samples. TAPIR-positive plasma reacted with the Abeta40 monomer and dimer, and the Abeta42 monomer weakly, but not with the Abeta42 dimer. TAPIR was even detected in samples from young normal subjects and young Tg2576 transgenic mice. Although the Abeta40 level and Abeta40/42 ratio increased, and Abeta42 was significantly decreased in plasma from AD groups when compared to controls, no significant correlations were revealed between plasma Abeta levels and TAPIR grading. Thus an immune response to Abeta40 and immune tolerance to Abeta42 occurred naturally in humans without a close relationship to the Abeta burden in the brain. Clarification of the mechanism of the immune response to Abeta42 is necessary for realization of an immunotherapy for AD. PMID:18534566

  19. High throughput screens for the identification of compounds that alter the accumulation of the Alzheimer's amyloid beta peptide (Abeta).

    PubMed

    Haugabook, S J; Yager, D M; Eckman, E A; Golde, T E; Younkin, S G; Eckman, C B

    2001-07-30

    Evidence gathered over the last two decades suggests that beta amyloid (Abeta), the predominant proteinaceous component of senile plaques, plays an early and critical role in the etiology and pathogenesis of Alzheimer's disease (AD). Thus, it is reasonable to hypothesize that compounds capable of reducing the accumulation of Abeta may be of value therapeutically. Additionally, compounds that influence Abeta accumulation may be useful as tools to further dissect the cellular pathways that regulate Abeta production and accumulation. To screen for compounds that affect Abeta levels, we have established high throughput, cell-based assays capable of the sensitive and selective detection of Abeta40 in parallel with the more amyloidogenic form of the peptide, Abeta42. To validate the approach, we examined the effects of several compounds previously identified to influence Abeta accumulation. Analysis of peptide accumulation following treatment with these compounds showed results similar to those previously published. Currently, we are using this assay to screen drugs that have already received FDA approval for the treatment of other diseases and over-the-counter natural product extracts. If compounds such as these can be identified that lower Abeta in the brain, they may represent one of the fastest and most cost effective methods to therapy. PMID:11478976

  20. Abeta42 gene vaccine prevents Abeta42 deposition in brain of double transgenic mice.

    PubMed

    Qu, Bao-Xi; Xiang, Qun; Li, Liping; Johnston, Stephen Albert; Hynan, Linda S; Rosenberg, Roger N

    2007-09-15

    Abeta42 peptide aggregation and deposition is an important component of the neuropathology of Alzheimer's disease (AD). Gene-gun mediated gene vaccination targeting Abeta42 is a potential method to prevent and treat AD. APPswe/PS1DeltaE9 transgenic (Tg) mice were immunized with an Abeta42 gene construct delivered by the gene gun. The vaccinated mice developed Th2 antibodies (IgG1) against Abeta42. The Abeta42 levels in brain were decreased by 41% and increased in plasma 43% in the vaccinated compared with control mice as assessed by ELISA analysis. Abeta42 plaque deposits in cerebral cortex and hippocampus were reduced by 51% and 52%, respectively, as shown by quantitative immunolabeling. Glial cell activation was also significantly attenuated in vaccinated compared with control mice. One rhesus monkey was vaccinated and developed anti-Abeta42 antibody. These new findings advance significantly our knowledge that gene-gun mediated Abeta42 gene immunization effectively induces a Th2 immune response and reduces the Abeta42 levels in brain in APPswe/PS1DeltaE9 mice. Abeta42 gene vaccination may be safe and efficient immunotherapy for AD. PMID:17574274

  1. A[Beta] Deposits in Older Non-Demented Individuals with Cognitive Decline Are Indicative of Preclinical Alzheimer's Disease

    ERIC Educational Resources Information Center

    Villemagne, V. L.; Pike, K. E.; Darby, D.; Maruff, P.; Savage, G.; Ng, S.; Ackermann, U.; Cowie, T. F.; Currie, J.; Chan, S. G.; Jones, G.; Tochon-Danguy, H.; O'Keefe, G.; Masters, C. L.; Rowe, C. C.

    2008-01-01

    Approximately 30% of healthy persons aged over 75 years show A[beta] deposition at autopsy. It is postulated that this represents preclinical Alzheimer's disease (AD). We evaluated the relationship between A[beta] burden as assessed by PiB PET and cognitive decline in a well-characterized, non-demented, elderly cohort. PiB PET studies and…

  2. Conversion of non-fibrillar {beta}-sheet oligomers into amyloid fibrils in Alzheimer's disease amyloid peptide aggregation

    SciTech Connect

    Benseny-Cases, Nuria; Cocera, Mercedes; Cladera, Josep

    2007-10-05

    A{beta}(1-40) is one of the main components of the fibrils found in amyloid plaques, a hallmark of brains affected by Alzheimer's disease. It is known that prior to the formation of amyloid fibrils in which the peptide adopts a well-ordered intermolecular {beta}-sheet structure, peptide monomers associate forming low and high molecular weight oligomers. These oligomers have been previously described in electron microscopy, AFM, and exclusion chromatography studies. Their specific secondary structures however, have not yet been well established. A major problem when comparing aggregation and secondary structure determinations in concentration-dependent processes such as amyloid aggregation is the different concentration range required in each type of experiment. In the present study we used the dye Thioflavin T (ThT), Fourier-transform infrared spectroscopy, and electron microscopy in order to structurally characterize the different aggregated species which form during the A{beta}(1-40) fibril formation process. A unique sample containing 90 {mu}M peptide was used. The results show that oligomeric species which form during the lag phase of the aggregation kinetics are a mixture of unordered, helical, and intermolecular non-fibrillar {beta}-structures. The number of oligomers and the amount of non-fibrillar {beta}-structures grows throughout the lag phase and during the elongation phase these non-fibrillar {beta}-structures are transformed into fibrillar (amyloid) {beta}-structures, formed by association of high molecular weight intermediates.

  3. Identification of distinct physiochemical properties of toxic prefibrillar species formed by A{beta} peptide variants

    SciTech Connect

    Goeransson, Anna-Lena; Nilsson, K. Peter R.; Kagedal, Katarina; Brorsson, Ann-Christin

    2012-04-20

    Highlights: Black-Right-Pointing-Pointer Identification of toxic prefibrillar A{beta} species. Black-Right-Pointing-Pointer Fluorescence measurements using a combined set of fluorophores. Black-Right-Pointing-Pointer Morphology studies using transmission electron microscopy. -- Abstract: The formation of amyloid-{beta} peptide (A{beta}) aggregates at an early stage during the self-assembly process is an important factor in the development of Alzheimer's disease. The toxic effect is believed to be exerted by prefibrillar species of A{beta}. It is therefore important to identify which prefibrillar species are toxic and characterize their distinct properties. In the present study, we investigated the in vitro aggregation behavior of A{beta}-derived peptides possessing different levels of neurotoxic activity, using fluorescence spectroscopy in combination with transmission electron microscopy. The toxicity of various A{beta} aggregates was assessed by using cultures of human neuroblastoma cells. Through combined use of the fluorescence probe 8-anilino-1-napthalenesulfonate (ANS) and the novel luminescent probe pentamer formyl thiophene acetic acid (p-FTAA), we were able to identify those A{beta} peptide-derived prefibrillar species which exhibited cellular toxicity. In particular, species, which formed early during the aggregation process and showed strong p-FTAA and ANS fluorescence, were the species that possessed toxic activities. Moreover, by manipulating the aggregation conditions, it was possible to change the capacity of the A{beta} peptide to form nontoxic versus toxic species.

  4. GluN2B subunit-containing NMDA receptor antagonists prevent Abeta-mediated synaptic plasticity disruption in vivo.

    PubMed

    Hu, Neng-Wei; Klyubin, Igor; Anwyl, Roger; Anwy, Roger; Rowan, Michael J

    2009-12-01

    Currently, treatment with the relatively low-affinity NMDA receptor antagonist memantine provides limited benefit in Alzheimer's disease (AD). One probable dose-limiting factor in the use of memantine is the inhibition of NMDA receptor-dependent synaptic plasticity mechanisms believed to underlie certain forms of memory. Moreover, amyloid-beta protein (Abeta) oligomers that are implicated in causing the cognitive deficits of AD potently inhibit this form of plasticity. Here we examined if subtype-preferring NMDA receptor antagonists could preferentially protect against the inhibition of NMDA receptor-dependent plasticity of excitatory synaptic transmission by Abeta in the hippocampus in vivo. Using doses that did not affect control plasticity, antagonists selective for NMDA receptors containing GluN2B but not other GluN2 subunits prevented Abeta(1-42) -mediated inhibition of plasticity. Evidence that the proinflammatory cytokine TNFalpha mediates this deleterious action of Ass was provided by the ability of TNFalpha antagonists to prevent Abeta(1-42) inhibition of plasticity and the abrogation of a similar disruptive effect of TNFalpha using a GluN2B-selective antagonist. Moreover, at nearby synapses that were resistant to the inhibitory effect of TNFalpha, Abeta(1-42) did not significantly affect plasticity. These findings suggest that preferentially targeting GluN2B subunit-containing NMDARs may provide an effective means of preventing cognitive deficits in early Alzheimer's disease. PMID:19918059

  5. Atomic View of a Toxic Amyloid Small Oligomer

    PubMed Central

    Laganowsky, Arthur; Liu, Cong; Sawaya, Michael R.; Whitelegge, Julian P.; Park, Jiyong; Zhao, Minglei; Pensalfini, Anna; Soriaga, Angela; Landau, Meytal; Teng, Poh K.; Cascio, Duilio; Glabe, Charles; Eisenberg, David

    2014-01-01

    Amyloid diseases, including Alzheimer's, Parkinson's, and the prion conditions, are each associated with a particular protein in fibrillar form. These amyloid fibrils were long suspected to be the disease agents, but evidence suggests that smaller, often transient and polymorphic oligomers are the toxic entities. Here we identify a segment of the amyloid-forming protein, alphaB crystallin, which forms an oligomeric complex exhibiting properties of other amyloid oligomers: beta-sheet-rich structure, cytotoxicity, and recognition by an anti-oligomer antibody. The X-ray-derived atomic structure of the oligomer reveals a cylindrical barrel, formed from six anti-parallel, protein strands, which we term a cylindrin. The cylindrin structure is compatible with a sequence segment from the Abeta protein of Alzheimer's disease. Cylindrins offer models for the hitherto elusive structures of amyloid oligomers. PMID:22403391

  6. Disruption of corticocortical connections ameliorates amyloid burden in terminal fields in a transgenic model of Abeta amyloidosis.

    PubMed

    Sheng, Jin G; Price, Donald L; Koliatsos, Vassilis E

    2002-11-15

    We demonstrated previously that amyloid precursor protein (APP) is anterogradely transported from the entorhinal cortex (ERC) to the dentate gyrus via axons of the perforant pathway. In the terminal fields of these inputs, APP undergoes proteolysis to generate C-terminal fragments containing the entire amyloid beta peptide (Abeta) domain. The present study was designed to test the hypothesis that APP derived from ERC neurons is the source of the Abeta peptide deposited in the hippocampal dentate gyrus in Alzheimer's disease (AD) and in transgenic mice with Abeta amyloidosis. We used mice harboring two familial AD-linked genes (human APP Swedish and presenilin1-DeltaE9), in which levels of Abeta (especially Abeta(42)) are elevated, leading to the formation of amyloid plaques, and lesioned the ERC to interrupt the transport of APP from ERC to hippocampus. Our results show that, on the side of ERC lesion, numbers of APP-immunoreactive dystrophic neurites and Abeta burden were significantly reduced by approximately 40 and 45%, respectively, in the dentate gyrus compared with the contralateral side. Reductions in APP and Abeta were more substantial in the molecular layer of the dentate, i.e., a region that contains the ERC terminals, and were associated with a parallel decrease in total APP and Abeta measured by Western blot and ProteinChip immunoassays. Silver and thioflavine staining confirmed the reduction of amyloid plaques on the side of deafferentation. These results are consistent with the hypothesis that ERC may be the primary source of amyloidogenic Abeta in the dentate gyrus, and they suggest an important role of corticocortical and corticolimbic forward connections in determining patterns of amyloid deposition in AD. PMID:12427835

  7. Disruption of Amyloid Plaques Integrity Affects the Soluble Oligomers Content from Alzheimer Disease Brains

    PubMed Central

    Moyano, Javier; Sanchez-Mico, María; Torres, Manuel; Davila, Jose Carlos; Vizuete, Marisa; Gutierrez, Antonia; Vitorica, Javier

    2014-01-01

    The implication of soluble Abeta in the Alzheimer’s disease (AD) pathology is currently accepted. In fact, the content of soluble extracellular Abeta species, such as monomeric and/or oligomeric Abeta, seems to correlate with the clinico-pathological dysfunction observed in AD patients. However, the nature (monomeric, dimeric or other oligomers), the relative abundance, and the origin (extra-/intraneuronal or plaque-associated), of these soluble species are actually under debate. In this work we have characterized the soluble (defined as soluble in Tris-buffered saline after ultracentrifugation) Abeta, obtained from hippocampal samples of Braak II, Braak III–IV and Braak V–VI patients. Although the content of both Abeta40 and Abeta42 peptides displayed significant increase with pathology progression, our results demonstrated the presence of low, pg/µg protein, amount of both peptides. This low content could explain the absence (or below detection limits) of soluble Abeta peptides detected by western blots or by immunoprecipitation-western blot analysis. These data were in clear contrast to those published recently by different groups. Aiming to explain the reasons that determine these substantial differences, we also investigated whether the initial homogenization could mobilize Abeta from plaques, using 12-month-old PS1xAPP cortical samples. Our data demonstrated that manual homogenization (using Dounce) preserved the integrity of Abeta plaques whereas strong homogenization procedures (such as sonication) produced a vast redistribution of the Abeta species in all soluble and insoluble fractions. This artifact could explain the dissimilar and somehow controversial data between different groups analyzing human AD samples. PMID:25485545

  8. NMR reveals anomalous copper(II) binding to the amyloid Abeta peptide of Alzheimer's disease.

    PubMed

    Hou, Liming; Zagorski, Michael G

    2006-07-26

    The Abeta peptide is the major protein component of amyloid deposits in Alzheimer's disease (AD). Age-related microenvironmental changes in the AD brain promote amyloid formation that leads to cell injury and death. Altered levels of metals (such as Cu and Zn) exist in the AD brain, and because Cu and Zn can be bound to the Abeta in the amyloid plaques, it is thought that these binding events in vivo may trigger or prevent Abeta amyloid formation in the AD brain. Although several structural models have been proposed, all of these are undefined due to the lack of definitive structural data. The present NMR studies utilized uniformly 15N-labeled Abeta(1-40) peptide and 1H-15N HSQC experiments and demonstrate for the first time that the Abeta binds Cu and Zn in a distinct manner. The binding promotes NH signal disappearance of E3-V18, which was not due to the paramagnetic effect of Cu2+, as identical NMR studies were seen with Zn2+, which is diamagnetic. NMR titration experiments showed that the amide NH peak intensities of R5-L17 showed the most pronounced intensity reduction, and that the 1H signals for the side chain aromatic signals of the three histidines shift upfield (H6, H13, and H14). We propose that initially Cu2+ is anchored to the Abeta monomer (fast exchange rate) and is followed by deprotonation and/or severe line broadening of the backbone amide NH for E3-V18 (intermediate exchange rate). By contrast, Cu2+ binding to soluble Abeta aggregates leads to rapid aggregation and nonfibrillar amorphous structures, and without metal, the Abeta can undergo the normal time-dependent aggregation, eventually producing more ordered, late-stage parallel beta-sheet structures. These anomalous (rare) binding events may account for some of the unique properties associated with the Abeta, such as its proposed "dual role", where sequestration of metal ions by the monomer is neuroprotective, while that by beta-aggregates generates oxygen radicals and causes neuronal death

  9. Blocking Abeta42 accumulation delays the onset and progression of tau pathology via the C terminus of heat shock protein70-interacting protein: a mechanistic link between Abeta and tau pathology.

    PubMed

    Oddo, Salvatore; Caccamo, Antonella; Tseng, Bert; Cheng, David; Vasilevko, Vitaly; Cribbs, David H; LaFerla, Frank M

    2008-11-19

    The molecular alterations that induce tau pathology in Alzheimer disease (AD) are not known, particularly whether this is an amyloid-beta (Abeta)-dependent or -independent event. We addressed this issue in the 3xTg-AD mice using both genetic and immunological approaches and show that a selective decrease in Abeta(42) markedly delays the progression of tau pathology. The mechanism underlying this effect involves alterations in the levels of C terminus of heat shock protein70-interacting protein (CHIP) as we show that Abeta accumulation decreases CHIP expression and increases tau levels. We show that the Abeta-induced effects on tau were rescued by restoring CHIP levels. Our findings have profound clinical implications as they indicate that preventing Abeta accumulation will significantly alter AD progression. These data highlight the critical role CHIP plays as a link between Abeta and tau and identify CHIP as a new potential target not only for AD but for other neurodegenerative disorders characterized by tau accumulation. PMID:19020010

  10. Phosphate and HEPES buffers potently affect the fibrillation and oligomerization mechanism of Alzheimer's A{beta} peptide

    SciTech Connect

    Garvey, Megan; Tepper, Katharina; Haupt, Caroline; Knuepfer, Uwe; Klement, Karolin; Meinhardt, Jessica; Horn, Uwe; Balbach, Jochen; Faendrich, Marcus

    2011-06-10

    Highlights: {yields} Sodium phosphate buffer accelerated A{beta}(1-40) nucleation relative to HEPES. {yields} A{beta}(1-40) fibrils formed in the two buffers show only minor structural differences. {yields} NMR revealed that A{beta}(1-40) histidine residues mediate buffer dependent changes. -- Abstract: The oligomerization of A{beta} peptide into amyloid fibrils is a hallmark of Alzheimer's disease. Due to its biological relevance, phosphate is the most commonly used buffer system for studying the formation of A{beta} and other amyloid fibrils. Investigation into the characteristics and formation of amyloid fibrils frequently relies upon material formed in vitro, predominantly in phosphate buffers. Herein, we examine the effects on the fibrillation and oligomerization mechanism of A{beta} peptide that occur due solely to the influence of phosphate buffer. We reveal that significant differences in amyloid fibrillation are observed due to fibrillation being initiated in phosphate or HEPES buffer (at physiological pH and temperature). Except for the differing buffer ions, all experimental parameters were kept constant. Fibril formation was assessed using fluorescently monitored kinetic studies, microscopy, X-ray fiber diffraction and infrared and nuclear magnetic resonance spectroscopies. Based on this set up, we herein reveal profound effects on the mechanism and speed of A{beta} fibrillation. The three histidine residues at positions 6, 13 and 14 of A{beta}(1-40) are instrumental in these mechanistic changes. We conclude that buffer plays a more significant role in fibril formation than has been generally acknowledged.

  11. Proteomic identification of less oxidized brain proteins in aged senescence-accelerated mice following administration of antisense oligonucleotide directed at the Abeta region of amyloid precursor protein.

    PubMed

    Poon, H Fai; Farr, Susan A; Banks, William A; Pierce, William M; Klein, Jon B; Morley, John E; Butterfield, D Allan

    2005-07-29

    Amyloid beta-peptide (Abeta) is the major constituent of senile plaques, a pathological hallmark of Alzheimer's disease (AD) brain. It is generally accepted that Abeta plays a central role in the pathophysiology of AD. Abeta is released from cells under entirely normal cellular conditions during the internalization and endosomal processing of amyloid precursor protein (APP). However, accumulation of Abeta can induce neurotoxicity. Our previous reports showed that decreasing the production of Abeta by giving an intracerebroventricular injection of a 42-mer phosphorothiolated antisense oligonucleotide (AO) directed at the Abeta region of the APP gene reduces lipid peroxidation and protein oxidation and improves cognitive deficits in aged senescence-accelerated mice prone 8 (SAMP8) mice. In order to investigate how Abeta level reduction improves learning and memory performance of SAMP8 mice through reduction of oxidative stress in brains, we used proteomics to identify the proteins that are less oxidized in 12-month-old SAMP8 mice brains treated with AO against the Abeta region of APP (12 mA) compared to that of the age-control SAMP8 mice. We found that the specific protein carbonyl levels of aldoase 3 (Aldo3), coronin 1a (Coro1a) and peroxiredoxin 2 (Prdx2) are significantly decreased in the brains of 12 mA SAMP8 mice compared to the age-controlled SAMP8 treated with random AO (12 mR). We also found that the expression level of alpha-ATP synthase (Atp5a1) was significantly decreased, whereas the expression of profilin 2 (Pro-2) was significantly increased in brains from 12 mA SAMP8 mice. Our results suggest that decreasing Abeta levels in aged brain in aged accelerated mice may contribute to the mechanism of restoring the learning and memory improvement in aged SAMP8 mice and may provide insight into the role of Abeta in the memory and cognitive deficits in AD. PMID:15932783

  12. Binding of an oxindole alkaloid from Uncaria tomentosa to amyloid protein (Abeta1-40).

    PubMed

    Frackowiak, Teresa; Baczek, Tomasz; Roman, Kaliszana; Zbikowska, Beata; Gleńsk, Michał; Fecka, Izabela; Cisowski, Wojciech

    2006-01-01

    The primary aim of this work was to determine the interactions of an oxindole alkaloid (mitraphylline) isolated from Uncaria tomentosa with beta-amyloid 1-40 (Abeta1-40 protein) applying the capillary electrophoresis (CE) method. Specifically the Hummel-Dreyer method and Scatchard analysis were performed to study the binding of oxindole alkaloids with Abeta1-40 protein. Prior to these studies extraction of the alkaloid of interest was carried out. Identification of the isolated alkaloid was performed by the use of thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) combined with electrospray ionization mass spectrometry (ESI-MS). The proposed approach was proved to be an efficient and accurate method for specific compound isolation and identification purposes. Moreover, analytical information from the CE approach can be considered as the valuable tool for binding constant determination. The binding constant of mitraphylline with Abeta1-40 protein determined by the Hummel-Dreyer method and Scatchard analysis equals K = 9.95 x 10(5) M(-1). The results obtained showed the significant binding of the tested compound with Abeta1-40 protein. These results are discussed and interpreted in the view of developing a strategy for identification of novel compounds of great importance in Alzheimer disease therapy. PMID:17294693

  13. Validation of Abeta1-40 administration into mouse cerebroventricles as an animal model for Alzheimer disease.

    PubMed

    Takeda, Shuko; Sato, Naoyuki; Niisato, Kazue; Takeuchi, Daisuke; Kurinami, Hitomi; Shinohara, Mitsuru; Rakugi, Hiromi; Kano, Masanobu; Morishita, Ryuichi

    2009-07-14

    Valid animal models for a specific human disease are indispensable for development of new therapeutic agents. The conclusions drawn from animal models largely depend on the validity of the model. Several studies have shown that administration of Abeta into the brain causes some of the pathological events observed in Alzheimer disease (AD). However, the validity of these models has not fully been examined. In this present study, we further characterized and validated Abeta1-40 injected mice as an animal model for AD, based on three major criteria: face, construct and predictive validity. Intracerebroventricular (i.c.v.) injection of Abeta1-40 into mice significantly impaired memory acquisition, but not memory retrieval, which implies similarity to the episodic anterograde memory deficit observed in the early stage of AD. Electrophysiological assessment showed that i.c.v. administration of Abeta1-40 significantly attenuated hippocampal long-term potentiation. Treatment with galantamine, a drug currently in clinical use for AD, significantly improved cognitive dysfunction in this model. These results demonstrate that i.c.v. injection of Abeta1-40 caused specific dysfunction of memory processes, which at least partly fulfills three validity criteria for AD. Symptomatic and pathophysiological similarities of this model to AD are quite important in considering the usefulness of this animal model. This validated animal model could be useful to develop and evaluate potential new drugs for AD. PMID:19464276

  14. Cu K-edge X-ray Absorption Spectroscopy Reveals Differential Copper Coordimation Within Amyloid-beta Oligomers Compared to Amyloid-beta Monomers

    SciTech Connect

    J Shearer; P Callan; T Tran; V Szalai

    2011-12-31

    The fatal neurodegenerative disorder Alzheimer's disease (AD) has been linked to the formation of soluble neurotoxic oligomers of amyloid-{beta} (A{beta}) peptides. These peptides have high affinities for copper cations. Despite their potential importance in AD neurodegeneration few studies have focused on probing the Cu{sup 2+/1+} coordination environment within A{beta} oligomers. Herein we present a Cu K-edge X-ray absorption spectroscopic study probing the copper-coordination environment within oligomers of A{beta}(42) (sequence: DAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIA). We find that the Cu{sup 2+} cation is contained within a square planar mixed N/O ligand environment within A{beta}(42) oligomers, which is similar to the copper coordination environment of the monomeric forms of {l_brace}Cu{sup II}A{beta}(40){r_brace} and {l_brace}Cu{sup II}A{beta}(16){r_brace}. Reduction of the Cu{sup 2+} cation within the A{beta}(42) oligomers to Cu{sup 1+} yields a highly dioxygen sensitive copper-species that contains Cu{sup 1+} in a tetrahedral coordination geometry. This can be contrasted with monomers of {l_brace}Cu{sup I}A{beta}(40){r_brace} and {l_brace}Cu{sup I}A{beta}(16){r_brace}, which contain copper in a dioxygen inert linear bis-histidine ligand environment [Shearer and Szalai, J. Am. Chem. Soc., 2008, 130, 17826]. The biological implications of these findings are discussed.

  15. Phenylethynyl terminated imide oligomers

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (Inventor); Bryant, Robert G. (Inventor); Jensen, Brian J. (Inventor); Havens, Stephen J. (Inventor)

    1995-01-01

    Four phenylethynyl amine compounds - 3 and 4-aminophenoxy-4'-phenylethynylbenzophenone, and 3 and 4-amino-4'-phenylethynylbenzophenone - were readily prepared and were used to endcap imide oligomers. Phenylethynyl-terminated amide acid oligomers and phenylethynyl-terminated imide oligomers with various molecular weights and compositions were prepared and characterized. These oligomers were cured at 300 to 400 C to provide crosslinked polyimides with excellent solvent resistance, high strength and modulus, and good high temperature properties. Adhesive panels, composites, films, and moldings from these phenylethynyl terminated imide oligomers gave excellent mechanical performance.

  16. Pathogenesis of A-beta+ ketosis-prone diabetes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A-beta+ ketosis-prone diabetes (KPD) is an emerging syndrome of obesity, unprovoked ketoacidosis, reversible beta-cell dysfunction, and near-normoglycemic remission. We combined metabolomics with targeted kinetic measurements to investigate its pathophysiology. Fasting plasma fatty acids, acylcarnit...

  17. Computational selection of inhibitors of Abeta aggregation and neuronal toxicity.

    PubMed

    Chen, Deliang; Martin, Zane S; Soto, Claudio; Schein, Catherine H

    2009-07-15

    Alzheimer's disease (AD) is characterized by the cerebral accumulation of misfolded and aggregated amyloid-beta protein (Abeta). Disease symptoms can be alleviated, in vitro and in vivo, by 'beta-sheet breaker' pentapeptides that reduce plaque load. However the peptide nature of these compounds, made them biologically unstable and unable to penetrate membranes with high efficiency. The main goal of this study was to use computational methods to identify small molecule mimetics with better drug-like properties. For this purpose, the docked conformations of the active peptides were used to identify compounds with similar activities. A series of related beta-sheet breaker peptides were docked to solid state NMR structures of a fibrillar form of Abeta. The lowest energy conformations of the active peptides were used to design three dimensional (3D)-pharmacophores, suitable for screening the NCI database with Unity. Small molecular weight compounds with physicochemical features and a conformation similar to the active peptides were selected, ranked by docking and biochemical parameters. Of 16 diverse compounds selected for experimental screening, 2 prevented and reversed Abeta aggregation at 2-3microM concentration, as measured by Thioflavin T (ThT) fluorescence and ELISA assays. They also prevented the toxic effects of aggregated Abeta on neuroblastoma cells. Their low molecular weight and aqueous solubility makes them promising lead compounds for treating AD. PMID:19540126

  18. Characteristics of Amyloid-Related Oligomers Revealed by Crystal Structures of Macrocyclic [beta]-Sheet Mimics

    SciTech Connect

    Liu, Cong; Sawaya, Michael R.; Cheng, Pin-Nan; Zheng, Jing; Nowick, James S.; Eisenberg, David

    2011-09-20

    Protein amyloid oligomers have been strongly linked to amyloid diseases and can be intermediates to amyloid fibers. {beta}-Sheets have been identified in amyloid oligomers. However, because of their transient and highly polymorphic properties, the details of their self-association remain elusive. Here we explore oligomer structure using a model system: macrocyclic peptides. Key amyloidogenic sequences from A{beta} and tau were incorporated into macrocycles, thereby restraining them to {beta}-strands, but limiting the growth of the oligomers so they may crystallize and cannot fibrillate. We determined the atomic structures for four such oligomers, and all four reveal tetrameric interfaces in which {beta}-sheet dimers pair together by highly complementary, dry interfaces, analogous to steric zippers found in fibers, suggesting a common structure for amyloid oligomers and fibers. In amyloid fibers, the axes of the paired sheets are either parallel or antiparallel, whereas the oligomeric interfaces display a variety of sheet-to-sheet pairing angles, offering a structural explanation for the heterogeneity of amyloid oligomers.

  19. Zinc and copper modulate Alzheimer Abeta levels in human cerebrospinal fluid.

    PubMed

    Strozyk, Dorothea; Launer, Lenore J; Adlard, Paul A; Cherny, Robert A; Tsatsanis, Andrew; Volitakis, Irene; Blennow, Kaj; Petrovitch, Helen; White, Lon R; Bush, Ashley I

    2009-07-01

    Abnormal interaction of beta-amyloid 42 (Abeta42) with copper, zinc and iron induce peptide aggregation and oxidation in Alzheimer's disease (AD). However, in health, Abeta degradation is mediated by extracellular metalloproteinases, neprilysin, insulin degrading enzyme (IDE) and matrix metalloproteinases. We investigated the relationship between levels of Abeta and biological metals in CSF. We assayed CSF copper, zinc, other metals and Abeta42 in ventricular autopsy samples of Japanese American men (N=131) from the population-based Honolulu Asia Aging Study. There was a significant inverse correlation of CSF Abeta42 with copper, zinc, iron, manganese and chromium. The association was particularly strong in the subgroup with high levels of both zinc and copper. Selenium and aluminum levels were not associated to CSF Abeta42. In vitro, the degradation of synthetic Abeta substrate added to CSF was markedly accelerated by low levels (2microM) of exogenous zinc and copper. While excessive interaction with copper and zinc may induce neocortical Abeta precipitation in AD, soluble Abeta degradation is normally promoted by physiological copper and zinc concentrations. PMID:18068270

  20. The iA{beta}5p {beta}-breaker peptide regulates the A{beta}(25-35) interaction with lipid bilayers through a cholesterol-mediated mechanism

    SciTech Connect

    Vitiello, Giuseppe; Grimaldi, Manuela; D'Ursi, Anna Maria; D'Errico, Gerardino

    2012-01-06

    Highlights: Black-Right-Pointing-Pointer iA{beta}5p shows a significant tendency to deeply penetrates the hydrophobic core of lipid membrane. Black-Right-Pointing-Pointer A{beta}(25-35) locates in the external region of the membrane causing a re-positioning of CHOL. Black-Right-Pointing-Pointer iA{beta}5p withholds cholesterol in the inner hydrophobic core of the lipid membrane. Black-Right-Pointing-Pointer iA{beta}5p prevents the A{beta}(25-35) release from the lipid membrane. -- Abstract: Alzheimer's disease is characterized by the deposition of aggregates of the {beta}-amyloid peptide (A{beta}) in the brain. A potential therapeutic strategy for Alzheimer's disease is the use of synthetic {beta}-sheet breaker peptides, which are capable of binding A{beta} but unable to become part of a {beta}-sheet structure, thus inhibiting the peptide aggregation. Many studies suggest that membranes play a key role in the A{beta} aggregation; consequently, it is strategic to investigate the interplay between {beta}-sheet breaker peptides and A{beta} in the presence of lipid bilayers. In this work, we focused on the effect of the {beta}-sheet breaker peptide acetyl-LPFFD-amide, iA{beta}5p, on the interaction of the A{beta}(25-35) fragment with lipid membranes, studied by Electron Spin Resonance spectroscopy, using spin-labeled membrane components (either phospholipids or cholesterol). The ESR results show that iA{beta}5p influences the A{beta}(25-35) interaction with the bilayer through a cholesterol-mediated mechanism: iA{beta}5p withholds cholesterol in the inner hydrophobic core of the bilayer, making the interfacial region more fluid and capable to accommodate A{beta}(25-35). As a consequence, iA{beta}5p prevents the A{beta}(25-35) release from the lipid membrane, which is the first step of the {beta}-amyloid aggregation process.

  1. Erratum: Intracellular amyloid β oligomers impair organelle transport and induce dendritic spine loss in primary neurons.

    PubMed

    Umeda, T; Ramser, E M; Yamashita, M; Nakajima, K; Mori, H; Silverman, M A; Tomiyama, T

    2016-01-01

    The original version of this article unfortunately contained a mistake in the presentation of Fig. 1 in both the PDF and HTML versions of this manuscript [1]. In the right panel of the corrected Fig. 1d, the images of Mock cells, which were visualized with GFP and stained with Abeta oligomer-specific antibody 11A1, were replaced with those of APPWT cells, and instead the images of APPWT cells were replaced with those of Mock cells. These images had been incorrectly placed in the original Fig. 1. The correct version of Fig. 1 is presented below. PMID:26822851

  2. Dynamics of Asp23-Lys28 salt-bridge formation in Abeta10-35 monomers.

    PubMed

    Tarus, Bogdan; Straub, John E; Thirumalai, D

    2006-12-20

    In the amyloid fibrils formed from long fragments of the amyloid beta-protein (Abeta-protein), the monomers are arranged in parallel and lie perpendicular to the fibril axis. The structure of the monomers satisfies the amyloid self-organization principle; namely, the low free energy state of the monomer maximizes the number of intra- and interpeptide contacts and salt bridges. The formation of the intramolecular salt bridge between Asp(D)23 and Lys(K)28 ensures that unpaired charges are not buried in the low-dielectric interior. We have investigated, using all-atom molecular dynamics simulations in explicit water, whether the D23-K28 interaction forms spontaneously in the isolated Abeta10-35 monomer. To validate the simulation protocol, we show, using five independent trajectories spanning a total of 100 ns, that the pKa values of the titratable groups are in good agreement with experimental measurements. The computed free energy disconnectvity graph shows that broadly the ensemble of compact random coil conformations can be clustered into four basins that are separated by free energy barriers ranging from 0.3 to 2.7 kcal/mol. There is significant residual structure in the conformation of the peptide in each of the basins. Due to the desolvation penalty, the structural motif with a stable turn involving the residues VGSN and a preformed D23-K28 contact is a minor component of the simulated structures. The extent of solvation of the peptides in the four basins varies greatly, which underscores the dynamical fluctuations in the monomer. Our results suggest that the early event in the oligomerization process must be the expulsion of discrete water molecules that facilitates the formation of interpeptide-interaction-driven stable structures with an intramolecular D23-K28 salt bridge and an intact VGSN turn. PMID:17165769

  3. Probing the stability of insulin oligomers using electrospray ionization ion mobility mass spectrometry.

    PubMed

    Boga Raja, Uday Kumar; Injeti, Srilakshmi; Culver, Tiffany; McCabe, Jacob W; Angel, Laurence A

    2015-01-01

    The peptide hormone insulin is central to regulating carbohydrate and fat metabolism in the body by controlling blood sugar levels. Insulin's most active form is the monomer and the extent of insulin oligomerization is related to insulin's activity of controlling blood sugar levels. Electrospray ionization (ESI) of human insulin produced a series of oligomers from the monomer to the undecamer identified using quadrupole ion mobility time-of-flight mass spectrometry. Previous research suggested that only the monomer, dimer and hexamer are native forms of insulin in solution and the range of oligomers observed in the gas-phase are ESI artifacts. Here the properties of three distinct oligomer bands I, II and III, where both the charge state and number of insulin units of the oligomer increase incrementally, were investigated. When Zn(ii) was added to the insulin sample the same oligomers were observed but with 0-6 Zn(ii) ions bound to each of the oligomers. The oligomers of bands I, II and III were characterized by comparing their drift times, collision cross- sections, relative intensities, collision-induced dissociation (CID) patterns and relative breakdown energies. Insulin oligomers of band I dissociated primarily by releasing either the 2+ or 3+ monomer accompanied by an oligomer that conserved the mass, charge and Zn(ii) of the precursor. Insulin oligomers of bands II and III dissociated primarily by releasing the 2+ monomer accompanied by an oligomer which conserved the mass, charge and Zn(ii) of the precursor. Comparison of CID patterns and breakdown energies showed all the oligomers in band II required higher collision energies to dissociate than the oligomers in band I, and the oligomers of band III required higher energies to dissociate than oligomers of band II. These results show that the amount of excess charge on the oligomer in respect to the number of insulin monomers in the oligomer affects their stability. PMID:26764306

  4. Phenylethynyl terminated reactive oligomer

    NASA Technical Reports Server (NTRS)

    Bryant, Robert G. (Inventor); Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor)

    1995-01-01

    A composition of matter having the general structure: ##STR1## (wherein X is F, Cl, or NO.sub.2, and Y is CO, SO.sub.2 or C(CF.sub.3).sub.2) is employed to terminate a nucleophilic reagent, resulting in the exclusive production of phenylethynyl terminated reactive oligomers which display unique thermal characteristics. A reactive diluent having the general structure: ##STR2## (wherein R is any aliphatic or aromatic moiety) is employed to decrease the melt viscosity of a phenylethynyl terminated reactive oligomer and to subsequently react therewith to provide a thermosetting material of enhanced density. These materials have features which make them attractive candidates for use as composite matrices and adhesives.

  5. SDS-PAGE/immunoblot detection of Abeta multimers in human cortical tissue homogenates using antigen-epitope retrieval.

    PubMed

    Rosen, Rebecca F; Tomidokoro, Yasushi; Ghiso, Jorge A; Walker, Lary C

    2010-01-01

    The anomalous folding and polymerization of the beta-amyloid (Abeta) peptide is thought to initiate the neurodegenerative cascade in Alzheimer's disease pathogenesis(1). Abeta is predominantly a 40- or 42-amino acid peptide that is prone to self-aggregation into beta-sheet-rich amyloid fibrils that are found in the cores of cerebral senile plaques in Alzheimer's disease. Increasing evidence suggests that low molecular weight, soluble Abeta multimers are more toxic than fibrillar Abeta amyloid(2). The identification and quantification of low- and high-molecular weight multimeric Abeta species in brain tissue is an essential objective in Alzheimer's disease research, and the methods employed also can be applied to the identification and characterization of toxic multimers in other proteopathies(3). Naturally occurring Abeta multimers can be detected by SDS-polyacrylamide gel electrophoresis followed by immunoblotting with Abeta-specific antibodies. However, the separation and detection of multimeric Abeta requires the use of highly concentrated cortical homogenates and antigen retrieval in small pore-size nitrocellulose membranes. Here we describe a technique for the preparation of clarified human cortical homogenates, separation of proteins by SDS-PAGE, and antigen-epitope retrieval/Western blotting with antibody 6E10 to the N-terminal region of the Abeta peptide. Using this protocol, we consistently detect Abeta monomers, dimers, trimers, tetramers, and higher molecular weight multimers in cortical tissue from humans with Alzheimer's pathology. PMID:20418805

  6. Transthyretin Val122Ile, accumulated Abeta, and inclusion-body myositis aspects in cultured muscle.

    PubMed

    Askanas, Valerie; Engel, W King; McFerrin, Janis; Vattemi, Gaetano

    2003-07-22

    Cultured muscle fibers (CMF) from a patient with inclusion-body myositis (IBM) and cardiac amyloidosis associated with the transthyretin (TTR) Val122Ile mutation contained aspects of the IBM phenotype: vacuolation, congophilic inclusions, and clusters of immunocolocalizing amyloid beta-peptide (Abeta) and TTR accumulations. These abnormalities are never present in normal human CMF. These perturbations were greatly increased after Abeta precursor protein gene transfer. The TTR mutation may be a genetic predisposition factor for the patient's IBM. PMID:12874414

  7. In vivo demonstration that α-synuclein oligomers are toxic

    PubMed Central

    Winner, Beate; Jappelli, Roberto; Maji, Samir K.; Desplats, Paula A.; Boyer, Leah; Aigner, Stefan; Hetzer, Claudia; Loher, Thomas; Vilar, Marçal; Campioni, Silvia; Tzitzilonis, Christos; Soragni, Alice; Jessberger, Sebastian; Mira, Helena; Consiglio, Antonella; Pham, Emiley; Masliah, Eliezer; Gage, Fred H.; Riek, Roland

    2011-01-01

    The aggregation of proteins into oligomers and amyloid fibrils is characteristic of several neurodegenerative diseases, including Parkinson disease (PD). In PD, the process of aggregation of α-synuclein (α-syn) from monomers, via oligomeric intermediates, into amyloid fibrils is considered the disease-causative toxic mechanism. We developed α-syn mutants that promote oligomer or fibril formation and tested the toxicity of these mutants by using a rat lentivirus system to investigate loss of dopaminergic neurons in the substantia nigra. The most severe dopaminergic loss in the substantia nigra is observed in animals with the α-syn variants that form oligomers (i.e., E57K and E35K), whereas the α-syn variants that form fibrils very quickly are less toxic. We show that α-syn oligomers are toxic in vivo and that α-syn oligomers might interact with and potentially disrupt membranes. PMID:21325059

  8. Characterization of the Aalpha and Abeta subunit isoforms of protein phosphatase 2A: differences in expression, subunit interaction, and evolution.

    PubMed Central

    Zhou, Jin; Pham, Huong T; Ruediger, Ralf; Walter, Gernot

    2003-01-01

    Protein phosphatase 2A (PP2A) is very versatile owing to a large number of regulatory subunits and its ability to interact with numerous other proteins. The regulatory A subunit exists as two closely related isoforms designated Aalpha and Abeta. Mutations have been found in both isoforms in a variety of human cancers. Although Aalpha has been intensely studied, little is known about Abeta. We generated Abeta-specific antibodies and determined the cell cycle expression, subcellular distribution, and metabolic stability of Abeta in comparison with Aalpha. Both forms were expressed at constant levels throughout the cell cycle, but Aalpha was expressed at a much higher level than Abeta. Both forms were found predominantly in the cytoplasm, and both had a half-life of approx. 10 h. However, Aalpha and Abeta differed substantially in their expression patterns in normal tissues and in tumour cell lines. Whereas Aalpha was expressed at similarly high levels in all tissues and cell lines, Abeta expression varied greatly. In addition, in vivo studies with epitope-tagged Aalpha and Abeta subunits demonstrated that Abeta is a markedly weaker binder of regulatory B and catalytic C subunits than Aalpha. Construction of phylogenetic trees revealed that the conservation of Aalpha during the evolution of mammals is extraordinarily high in comparison with both Abeta and cytochrome c, suggesting that Aalpha is involved in more protein-protein interactions than Abeta. We also measured the binding of polyoma virus middle tumour antigen and simian virus 40 (SV40) small tumour antigen to Aalpha and Abeta. Whereas both isoforms bound polyoma virus middle tumour antigen equally well, only Aalpha bound SV40 small tumour antigen. PMID:12370081

  9. Increased expression of PAD2 after repeated intracerebroventricular infusions of soluble Abeta(25-35) in the Alzheimer's disease model rat brain: effect of memantine.

    PubMed

    Arif, Mohammad; Kato, Takeshi

    2009-01-01

    Peptidylarginine deiminases (PADs) convert the arginine residues in proteins into citrulline residues in a Ca(2+)-dependent manner. We previously showed that a bilateral injection of ibotenic acid into the rat nucleus basalis magnocellularis elevated the PAD2 activity in the hippocampus and striatum. In this study, we examined whether repeated intracerebroventricular infusions of soluble Abeta25-35 would affect the PAD2 expression in any regions of the rat brain. We also assessed the protective effect of memantine on Abeta-induced PAD2 alterations. The infusion of Abeta(25-35) increased the activity and protein level of PAD2 in the hippocampus, and co-treatment with memantine suppressed these changes. An immunohistochemical analysis showed that an increased level of PAD2 was coincident with GFAP-positive astrocytes and CD11b-positive microglia. In addition, immunofluoresecence staining revealed that citrullinepostive immunoreactivity coincided with the occurrence of GFAP-positive astrocytes. Co-treatment with memantine reversed the activation of the astrocytes and microglia, thus attenuating the PAD2 increment. These biochemical and immunohistochemical results suggest that PAD2 might play an important role in the pathology of early Alzheimer's disease, and may correlate with the changes in glial cells that are recovered by memantine treatment. PMID:19641855

  10. Brain trauma in aged transgenic mice induces regression of established abeta deposits.

    PubMed

    Nakagawa, Y; Reed, L; Nakamura, M; McIntosh, T K; Smith, D H; Saatman, K E; Raghupathi, R; Clemens, J; Saido, T C; Lee, V M; Trojanowski, J Q

    2000-05-01

    Traumatic brain injury (TBI) increases susceptibility to Alzheimer's disease (AD), but it is not known if TBI affects the progression of AD. To address this question, we studied the neuropathological consequences of TBI in transgenic (TG) mice with a mutant human Abeta precursor protein (APP) mini-gene driven by a platelet-derived (PD) growth factor promoter resulting in overexpression of mutant APP (V717F), elevated brain Abeta levels, and AD-like amyloidosis. Since brain Abeta deposits first appear in 6-month-old TG (PDAPP) mice and accumulate with age, 2-year-old PDAPP and wild-type (WT) mice were subjected to controlled cortical impact (CCI) TBI or sham treatment. At 1, 9, and 16 weeks after TBI, neuron loss, gliosis, and atrophy were most prominent near the CCI site in PDAPP and WT mice. However, there also was a remarkable regression in the Abeta amyloid plaque burden in the hippocampus ipsilateral to TBI compared to the contralateral hippocampus of the PDAPP mice by 16 weeks postinjury. Thus, these data suggest that previously accumulated Abeta plaques resulting from progressive amyloidosis in the AD brain also may be reversible. PMID:10785464

  11. Elucidating molecular mass and shape of a neurotoxic Aβ oligomer.

    PubMed

    Sebollela, Adriano; Mustata, Gina-Mirela; Luo, Kevin; Velasco, Pauline T; Viola, Kirsten L; Cline, Erika N; Shekhawat, Gajendra S; Wilcox, Kyle C; Dravid, Vinayak P; Klein, William L

    2014-12-17

    Alzheimer's disease (AD), the most prevalent type of dementia, has been associated with the accumulation of amyloid β oligomers (AβOs) in the central nervous system. AβOs vary widely in size, ranging from dimers to larger than 100 kDa. Evidence indicates that not all oligomers are toxic, and there is yet no consensus on the size of the actual toxic oligomer. Here we used NU4, a conformation-dependent anti-AβO monoclonal antibody, to investigate size and shape of a toxic AβO assembly. By using size-exclusion chromatography and immuno-based detection, we isolated an AβO-NU4 complex amenable for biochemical and morphological studies. The apparent molecular mass of the NU4-targeted oligomer was 80 kDa. Atomic force microscopy imaging of the AβO-NU4 complex showed a size distribution centered at 5.37 nm, an increment of 1.5 nm compared to the size of AβOs (3.85 nm). This increment was compatible with the size of NU4 (1.3 nm), suggesting a 1:1 oligomer to NU4 ratio. NU4-reactive oligomers extracted from AD human brain concentrated in a molecular mass range similar to that found for in vitro prepared oligomers, supporting the relevance of the species herein studied. These results represent an important step toward understanding the connection between AβO size and toxicity. PMID:25343357

  12. Elucidating Molecular Mass and Shape of a Neurotoxic Aβ Oligomer

    PubMed Central

    2015-01-01

    Alzheimer's disease (AD), the most prevalent type of dementia, has been associated with the accumulation of amyloid β oligomers (AβOs) in the central nervous system. AβOs vary widely in size, ranging from dimers to larger than 100 kDa. Evidence indicates that not all oligomers are toxic, and there is yet no consensus on the size of the actual toxic oligomer. Here we used NU4, a conformation-dependent anti-AβO monoclonal antibody, to investigate size and shape of a toxic AβO assembly. By using size-exclusion chromatography and immuno-based detection, we isolated an AβO-NU4 complex amenable for biochemical and morphological studies. The apparent molecular mass of the NU4-targeted oligomer was 80 kDa. Atomic force microscopy imaging of the AβO-NU4 complex showed a size distribution centered at 5.37 nm, an increment of 1.5 nm compared to the size of AβOs (3.85 nm). This increment was compatible with the size of NU4 (1.3 nm), suggesting a 1:1 oligomer to NU4 ratio. NU4-reactive oligomers extracted from AD human brain concentrated in a molecular mass range similar to that found for in vitro prepared oligomers, supporting the relevance of the species herein studied. These results represent an important step toward understanding the connection between AβO size and toxicity. PMID:25343357

  13. Structural and functional properties of prefibrillar α-synuclein oligomers

    PubMed Central

    Pieri, Laura; Madiona, Karine; Melki, Ronald

    2016-01-01

    The deposition of fibrillar alpha-synuclein (α-syn) within inclusions (Lewy bodies and Lewy neurites) in neurons and glial cells is a hallmark of synucleinopathies. α-syn populates a variety of assemblies ranging from prefibrillar oligomeric species to fibrils whose specific contribution to neurodegeneration is still unclear. Here, we compare the specific structural and biological properties of distinct soluble prefibrillar α-syn oligomers formed either spontaneously or in the presence of dopamine and glutaraldehyde. We show that both on-fibrillar assembly pathway and distinct dopamine-mediated and glutaraldehyde-cross-linked α-syn oligomers are only slightly effective in perturbing cell membrane integrity and inducing cytotoxicity, while mature fibrils exhibit the highest toxicity. In contrast to low-molecular weight and unstable oligomers, large stable α-syn oligomers seed the aggregation of soluble α-syn within reporter cells although to a lesser extent than mature α-syn fibrils. These oligomers appear elongated in shape. Our findings suggest that α-syn oligomers represent a continuum of species ranging from unstable low molecular weight particles to mature fibrils via stable elongated oligomers composed of more than 15 α-syn monomers that possess seeding capacity. PMID:27075649

  14. Antiparallel Triple-strand Architecture for Prefibrillar Aβ42 Oligomers*

    PubMed Central

    Gu, Lei; Liu, Cong; Stroud, James C.; Ngo, Sam; Jiang, Lin; Guo, Zhefeng

    2014-01-01

    Aβ42 oligomers play key roles in the pathogenesis of Alzheimer disease, but their structures remain elusive partly due to their transient nature. Here, we show that Aβ42 in a fusion construct can be trapped in a stable oligomer state, which recapitulates characteristics of prefibrillar Aβ42 oligomers and enables us to establish their detailed structures. Site-directed spin labeling and electron paramagnetic resonance studies provide structural restraints in terms of side chain mobility and intermolecular distances at all 42 residue positions. Using these restraints and other biophysical data, we present a novel atomic-level oligomer model. In our model, each Aβ42 protein forms a single β-sheet with three β-strands in an antiparallel arrangement. Each β-sheet consists of four Aβ42 molecules in a head-to-tail arrangement. Four β-sheets are packed together in a face-to-back fashion. The stacking of identical segments between different β-sheets within an oligomer suggests that prefibrillar oligomers may interconvert with fibrils via strand rotation, wherein β-strands undergo an ∼90° rotation along the strand direction. This work provides insights into rational design of therapeutics targeting the process of interconversion between toxic oligomers and non-toxic fibrils. PMID:25118290

  15. Toxic species in amyloid disorders: Oligomers or mature fibrils

    PubMed Central

    Verma, Meenakshi; Vats, Abhishek; Taneja, Vibha

    2015-01-01

    Protein aggregation is the hallmark of several neurodegenerative disorders. These protein aggregation (fibrillization) disorders are also known as amyloid disorders. The mechanism of protein aggregation involves conformation switch of the native protein, oligomer formation leading to protofibrils and finally mature fibrils. Mature fibrils have long been considered as the cause of disease pathogenesis; however, recent evidences suggest oligomeric intermediates formed during fibrillization to be toxic. In this review, we have tried to address the ongoing debate for these toxic amyloid species. We did an extensive literature search and collated information from Pubmed (http://www.ncbi.nlm.nih.gov) and Google search using various permutations and combinations of the following keywords: Neurodegeneration, amyloid disorders, protein aggregation, fibrils, oligomers, toxicity, Alzheimer's Disease, Parkinson's Disease. We describe different instances showing the toxicity of mature fibrils as well as oligomers in Alzheimer's Disease and Parkinson's Disease. Distinct structural framework and morphology of amyloid oligomers suggests difference in toxic effect between oligomers and fibrils. We highlight the difference in structure and proposed toxicity pathways for fibrils and oligomers. We also highlight the evidences indicating that intermediary oligomeric species can act as potential diagnostic biomarker. Since the formation of these toxic species follow a common structural switch among various amyloid disorders, the protein aggregation events can be targeted for developing broad-range therapeutics. The therapeutic trials based on the understanding of different protein conformers (monomers, oligomers, protofibrils and fibrils) in amyloid cascade are also described. PMID:26019408

  16. Quaternary structure defines a large class of amyloid-β oligomers neutralized by sequestration

    PubMed Central

    Liu, Peng; Reed, Miranda N.; Kotilinek, Linda A.; Grant, Marianne K.O.; Forster, Colleen L.; Qiang, Wei; Shapiro, Samantha L.; Reichl, John H.; Chiang, Angie C.A.; Jankowsky, Joanna L.; Wilmot, Carrie M.; Cleary, James P.; Zahs, Kathleen R.; Ashe, Karen H.

    2015-01-01

    Summary The accumulation of amyloid-β (Aβ) as amyloid fibrils and toxic oligomers is an important step in the development of Alzheimer's disease (AD). However, there are numerous potentially toxic oligomers and little is known about their neurological effects when generated in the living brain. Here, we show that Aβ oligomers can be assigned to one of at least two classes (Type 1 and Type 2) based on their temporal, spatial and structural relationships to amyloid fibrils. The Type 2 oligomers are related to amyloid fibrils and represent the majority of oligomers generated in vivo, but remain confined to the vicinity of amyloid plaques and do not impair cognition at levels relevant to AD. Type 1 oligomers are unrelated to amyloid fibrils and may have greater potential to cause global neural dysfunction in AD because they are dispersed. These results refine our understanding of the pathogenicity of Aβ oligomers in vivo. PMID:26051935

  17. Lower levels of cerebrospinal fluid amyloid beta (Abeta) in non-demented Indian controls.

    PubMed

    Subramanian, Sarada; Sandhyarani, Boya; Shree, A N Divya; Murthy, K Krishna; Kalyani, K; Kumar, S Praveen; Pradeep; Noone, Mohin Jeslie; Taly, A B

    2006-10-23

    Prevalence of Alzheimer's disease in Indian population is lower than in developed countries. To determine whether limitation of amyloid beta (Abeta) concentration may be responsible for lower rate of incidence, we measured the levels of Abeta in cerebrospinal fluid (CSF) collected from 72 non-demented individuals ranging in the age from 20 years to 65 years. These samples were segregated into three groups ranging from 20-35 years, 36-50 years and 51-65 years of age. Levels of Abeta could be detected in all the age groups and they were much lower than the values reported in literature from the developed countries. No significant difference in the average level of Ass was observed with increase in age. PMID:16978775

  18. Structural differences between amyloid beta oligomers.

    PubMed

    Breydo, Leonid; Kurouski, Dmitry; Rasool, Suhail; Milton, Saskia; Wu, Jessica W; Uversky, Vladimir N; Lednev, Igor K; Glabe, Charles G

    2016-09-01

    In Alzheimer's disease, soluble Aβ oligomers are believed to play important roles in the disease pathogenesis, and their levels correlate with cognitive impairment. We have previously shown that Aβ oligomers can be categorized into multiple structural classes based on their reactivity with conformation-dependent antibodies. In this study, we analyzed the structures of Aβ40 oligomers belonging to two of these classes: fibrillar and prefibrillar oligomers. We found that fibrillar oligomers were similar in structure to fibrils but were less stable towards denaturation while prefibrillar oligomers were found to be partially disordered. These results are consistent with previously proposed structures for both oligomer classes while providing additional structural information. PMID:27363332

  19. Hydrogen sulfide prevents Abeta-induced neuronal apoptosis by attenuating mitochondrial translocation of PTEN.

    PubMed

    Cui, Weigang; Zhang, Yinghua; Yang, Chenxi; Sun, Yiyuan; Zhang, Min; Wang, Songtao

    2016-06-14

    Neuronal cell apoptosis is an important pathological change in Alzheimer's disease (AD). Hydrogen sulfide (H(2)S) is known to be a novel gaseous signaling molecule and a cytoprotectant in many diseases including AD. However, the molecular mechanism of the antiapoptosis activity of H(2)S in AD is not yet fully understood. The aim of the present study is to evaluate the inhibitory effects of H(2)S on Abeta (Aβ)-induced apoptosis and the molecular mechanisms underlying primary neuron cells. Our results showed that sodium hydrosulfide (NaHS), a donor of H(2)S, significantly ameliorated Aβ-induced cell apoptosis. NaHS also reversed the Aβ-induced translocation of the phosphatase and tensin homologs deleted on chromosome 10 (PTEN) from the cytosol to the mitochondria. Furthermore, H(2)S increased the level of p-AKT/AKT significantly. Interestingly, the antiapoptosis effects of H(2)S were blocked down by specific PI3K/AKT inhibitor wortmannin. In conclusion, these data indicate that H(2)S inhibits Aβ-induced neuronal apoptosis by attenuating mitochondrial translocation of PTEN and that activation of PI3K/AKT signaling pathway plays a critical role in H(2)S-mediated neuronal protection. Our findings provide a novel route into the molecular mechanisms of neuronal apoptosis in AD. PMID:27026591

  20. Chemical Fluorescent Probe for Detection of Aβ Oligomers.

    PubMed

    Teoh, Chai Lean; Su, Dongdong; Sahu, Srikanta; Yun, Seong-Wook; Drummond, Eleanor; Prelli, Frances; Lim, Sulgi; Cho, Sunhee; Ham, Sihyun; Wisniewski, Thomas; Chang, Young-Tae

    2015-10-28

    Aggregation of amyloid β-peptide (Aβ) is implicated in the pathology of Alzheimer's disease (AD), with the soluble, Aβ oligomeric species thought to be the critical pathological species. Identification and characterization of intermediate species formed during the aggregation process is crucial to the understanding of the mechanisms by which oligomeric species mediate neuronal toxicity and following disease progression. Probing these species proved to be extremely challenging, as evident by the lack of reliable sensors, due to their heterogeneous and transient nature. We describe here an oligomer-specific fluorescent chemical probe, BoDipy-Oligomer (BD-Oligo), developed through the use of the diversity-oriented fluorescent library approach (DOFLA) and high-content, imaging-based screening. This probe enables dynamic oligomer monitoring during fibrillogenesis in vitro and shows in vivo Aβ oligomers staining possibility in the AD mice model. PMID:26218347

  1. Targeting Cancer with Antisense Oligomers

    SciTech Connect

    Hnatowich, DJ

    2008-10-28

    With financial assistance from the Department of Energy, we have shown definitively that radiolabeled antisense DNAs and other oligomers will accumulate in target cancer cells in vitro and in vivo by an antisense mechanism. We have also shown that the number of mRNA targets for our antisense oligomers in the cancer cell types that we have investigated so far is sufficient to provide and antisense image and/or radiotherapy of cancer in mice. These studies have been reported in about 10 publications. However our observation over the past several years has shown that radiolabeled antisense oligomers administered intravenously in their native and naked form will accumulate and be retained in target xenografts by an antisense mechanism but will also accumulate at high levels in normal organs such as liver, spleen and kidneys. We have investigated unsuccessfully several commercially available vectors. Thus the use of radiolabeled antisense oligomers for the imaging of cancer must await novel approaches to delivery. This laboratory has therefore pursued two new paths, optical imaging of tumor and Auger radiotherapy. We are developing a novel method of optical imaging tumor using antisense oligomers with a fluorophore is administered while hybridized with a shorter complementary oligomer with an inhibitor. In culture and in tumored mice that the duplex remains intact and thus nonfluorescent until it encounters its target mRNA at which time it dissociates and the antisense oligomer binds along with its fluorophore to the target. Simultaneous with the above, we have also observed, as have others, that antisense oligomers migrate rapidly and quantitatively to the nucleus upon crossing cell membranes. The Auger electron radiotherapy path results from this observation since the nuclear migration properties could be used effectively to bring and to retain in the nucleus an Auger emitting radionuclide such as 111In or 125I bound to the antisense oligomer. Since the object becomes

  2. Interaction of arginine oligomer with model membrane

    SciTech Connect

    Yi, Dandan . E-mail: yi_dandan@yahoo.com.cn; Guoming, Li; Gao, Li; Wei, Liang

    2007-08-10

    Short oligomers of arginine (R8) have been shown to cross readily a variety of biological barriers. A hypothesis was put forward that inverted micelles form in biological membranes in the presence of arginine oligomer peptides, facilitating their transfer through the membranes. In order to define the role of peptide-lipid interaction in this mechanism, we prepared liposomes as the model membrane to study the ability of R8 inducing calcein release from liposomes, the fusion of liposomes, R8 binding to liposomes and membrane disturbing activity of the bound R8. The results show that R8 binding to liposome membrane depends on lipid compositions, negative surface charge density and interior water phase pH values of liposomes. R8 has no activity to induce the leakage of calcein from liposomes or improve liposome fusion. R8 does not permeabilize through the membrane spontaneously. These peptides delivering drugs through membranes may depend on receptors and energy.

  3. Retardation of Abeta fibril formation by phospholipid vesicles depends on membrane phase behavior.

    PubMed

    Hellstrand, Erik; Sparr, Emma; Linse, Sara

    2010-05-19

    An increasing amount of evidence suggests that in several amyloid diseases, the fibril formation in vivo and the mechanism of toxicity both involve membrane interactions. We have studied Alzheimer's disease related amyloid beta peptide (Abeta). Recombinant Abeta(M1-40) and Abeta(M1-42) produced in Escherichia coli, allows us to carry out large scale kinetics assays with good statistics. The amyloid formation process is followed in means of thioflavin T fluorescence at relatively low (down to 380 nM) peptide concentration approaching the physiological range. The lipid membranes are introduced in the system as large and small unilamellar vesicles. The aggregation lagtime increases in the presence of lipid vesicles for all situations investigated and the phase behavior of the membrane in the vesicles has a large effect on the aggregation kinetics. By comparing vesicles with different membrane phase behavior we see that the solid gel phase dipalmitoylphosphatidylcholine bilayers cause the largest retardation of Abeta fibril formation. The membrane-induced retardation reaches saturation and is present when the vesicles are added during the lag time up to the nucleation point. No significant difference is detected in lag time when increasing amount of negative charge is incorporated into the membrane. PMID:20483329

  4. The Alzheimer's beta amyloid (Abeta1-39) monomer in an implicit solvent.

    PubMed

    Anand, Priya; Nandel, F S; Hansmann, Ulrich H E

    2008-04-28

    Results from replica-exchange and regular room temperature molecular dynamics simulations of the Alzheimer's beta amyloid (Abeta(1-39)) monomer in an implicit solvent are reported. Our data indicate that at room temperature, the monomer assumes random-coil and soluble conformations. No beta content is observed which therefore seems to be a product of oligomerization and aggregation of monomers. PMID:18447506

  5. Structural Insight into Proteorhodopsin Oligomers

    PubMed Central

    Stone, Katherine M.; Voska, Jeda; Kinnebrew, Maia; Pavlova, Anna; Junk, Matthias J.N.; Han, Songi

    2013-01-01

    Oligomerization has important functional implications for many membrane proteins. However, obtaining structural insight into oligomeric assemblies is challenging, as they are large and resist crystallization. We focus on proteorhodopsin (PR), a protein with seven transmembrane α-helices that was found to assemble to hexamers in densely packed lipid membrane, or detergent-solubilized environments. Yet, the structural organization and the subunit interface of these PR oligomers were unknown. We used site-directed spin-labeling together with electron spin-resonance lineshape and Overhauser dynamic nuclear polarization analysis to construct a model for the specific orientation of PR subunits within the hexameric complex. We found intersubunit distances to average 16 Å between neighboring 55 residues and that residues 177 are >20 Å apart from each other. These distance constraints show that PR has a defined and radial orientation within a hexamer, with the 55-site of the A-B loop facing the hexamer core and the 177-site of the E-F loop facing the hexamer exterior. Dynamic nuclear polarization measurements of the local solvent dynamics complement the electron spin-resonance-based distance analysis, by resolving whether protein surfaces at positions 55, 58, and 177 are exposed to solvent, or covered by protein-protein or protein-detergent contacts. PMID:23442869

  6. [Peoniflorin activates Nrf2/ARE pathway to alleviate the Abeta(1-42)-induced hippocampal neuron injury in rats].

    PubMed

    Zhong, Shu-Zhi; ma, Shi-Ping; Hong, Zong-Yuan

    2013-08-01

    This study was to investigate the effect of peoniflorin on the expressions of nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream signal molecules in the hippocampus of Alzheimer's disease (AD) rats for exploring the mechanism of peoniflorin protecting hippocampal neurons. AD model rats were established by bilateral intrahippocampal injection of beta-amyloid(1-42) (Abeta(1-42)) and divided randomly into 3 groups: AD model group, peoniflorin low-dose (15 mg x kg(-1)) group and peoniflorin high-dose (30 mg x kg(-1)) group. The vehicle control rats were given bilateral intrahippocampal injection of solvent with the same volume. After peoniflorin or saline was administered (ip) once daily for 14 days, the hippocampuses of all animals were taken out for measuring the expressions of Nrf2, heme oxygenase-1 (HO-1) and gamma-glutamylcysteine synthethase (gamma-GCS) mRNA by reverse transcription PCR, determining the contents of glutathione (GSH), malondialdehyde (MDA) and carbonyl protein (CP) using colorimetric method, and for assaying the expressions of neuronal apoptosis inhibitory protein (NAIP) and Caspase-3 by immunohistochemical staining method. The results showed that peoniflorin markedly increased the expressions of Nrf2, HO-1 and gamma-GCS mRNA, enhanced the level of GSH and decreased the contents of MDA and CP in the hippocampus, as compared with the model group. Peoniflorin also improved the NAIP expression and reduced the Caspase-3 expression in the hippocampus neurons. In conclusion, peoniflorin protects against the Abeta(1-42)-mediated oxidative stress and hippocampal neuron injury in AD rats by activating the Nrf2/ARE pathway. PMID:24187848

  7. Soluble state high resolution atomic force microscopy study of Alzheimer’s β-amyloid oligomers

    PubMed Central

    Shekhawat, Gajendra S.; Lambert, Mary P.; Sharma, Saurabh; Velasco, Pauline T.; Viola, Kirsten L.; Klein, William L.; Dravid, Vinayak P.

    2009-01-01

    We report here the direct observation of high resolution structures of assemblies of Alzheimer β-amyloid oligomers and monomers using liquid atomic force microscopy (AFM). Visualization of nanoscale features of Aβ oligomers (also known as ADDLs) was carried out in tapping mode AFM in F12 solution. Our results indicate that ADDL preparations exist in solution primarily as a mixture of monomeric peptides and higher molecular mass oligomers. Our study clearly reveals that the size and shape of these oligomer aggregates exhibit a pronounced dependence on concentration. These studies show that wet AFM enables direct assessment of oligomers in physiological fluids and suggests that this method may be developed to visualize Aβ oligomers from human fluids. PMID:19997583

  8. Soluble state high resolution atomic force microscopy study of Alzheimer's β-amyloid oligomers

    NASA Astrophysics Data System (ADS)

    Shekhawat, Gajendra S.; Lambert, Mary P.; Sharma, Saurabh; Velasco, Pauline T.; Viola, Kirsten L.; Klein, William L.; Dravid, Vinayak P.

    2009-11-01

    We report here the direct observation of high resolution structures of assemblies of Alzheimer β-amyloid oligomers and monomers using liquid atomic force microscopy (AFM). Visualization of nanoscale features of Aβ oligomers (also known as ADDLs) was carried out in tapping mode AFM in F12 solution. Our results indicate that ADDL preparations exist in solution primarily as a mixture of monomeric peptides and higher molecular mass oligomers. Our study clearly reveals that the size and shape of these oligomer aggregates exhibit a pronounced dependence on concentration. These studies show that wet AFM enables direct assessment of oligomers in physiological fluids and suggests that this method may be developed to visualize Aβ oligomers from human fluids.

  9. An infrared sensor analysing label-free the secondary structure of the Abeta peptide in presence of complex fluids.

    PubMed

    Nabers, Andreas; Ollesch, Julian; Schartner, Jonas; Kötting, Carsten; Genius, Just; Haußmann, Ute; Klafki, Hans; Wiltfang, Jens; Gerwert, Klaus

    2016-03-01

    The secondary structure change of the Abeta peptide to beta-sheet was proposed as an early event in Alzheimer's disease. The transition may be used for diagnostics of this disease in an early state. We present an Attenuated Total Reflection (ATR) sensor modified with a specific antibody to extract minute amounts of Abeta peptide out of a complex fluid. Thereby, the Abeta peptide secondary structure was determined in its physiological aqueous environment by FTIR-difference-spectroscopy. The presented results open the door for label-free Alzheimer diagnostics in cerebrospinal fluid or blood. It can be extended to further neurodegenerative diseases. An immunologic ATR-FTIR sensor for Abeta peptide secondary structure analysis in complex fluids is presented. PMID:25808829

  10. Neuroprotection and neurorescue against Abeta toxicity and PKC-dependent release of nonamyloidogenic soluble precursor protein by green tea polyphenol (-)-epigallocatechin-3-gallate.

    PubMed

    Levites, Yona; Amit, Tamar; Mandel, Silvia; Youdim, Moussa B H

    2003-05-01

    Green tea extract and its main polyphenol constituent (-)-epigallocatechin-3-gallate (EGCG) possess potent neuroprotective activity in cell culture and mice model of Parkinson's disease. The central hypothesis guiding this study is that EGCG may play an important role in amyloid precursor protein (APP) secretion and protection against toxicity induced by beta-amyloid (Abeta). The present study shows that EGCG enhances (approximately 6-fold) the release of the non-amyloidogenic soluble form of the amyloid precursor protein (sAPPalpha) into the conditioned media of human SH-SY5Y neuroblastoma and rat pheochromocytoma PC12 cells. sAPPalpha release was blocked by the hydroxamic acid-based metalloprotease inhibitor Ro31-9790, which indicated mediation via alpha-secretase activity. Inhibition of protein kinase C (PKC) with the inhibitor GF109203X, or by down-regulation of PKC, blocked the EGCG-induced sAPPalpha secretion, suggesting the involvement of PKC. Indeed, EGCG induced the phosphorylation of PKC, thus identifying a novel PKC-dependent mechanism of EGCG action by activation of the non-amyloidogenic pathway. EGCG is not only able to protect, but it can rescue PC12 cells against the beta-amyloid (Abeta) toxicity in a dose-dependent manner. In addition, administration of EGCG (2 mg/kg) to mice for 7 or 14 days significantly decreased membrane-bound holoprotein APP levels, with a concomitant increase in sAPPalpha levels in the hippocampus. Consistently, EGCG markedly increased PKCalpha and PKC in the membrane and the cytosolic fractions of mice hippocampus. Thus, EGCG has protective effects against Abeta-induced neurotoxicity and regulates secretory processing of non-amyloidogenic APP via PKC pathway. PMID:12670874

  11. Density functional theory study of neutral and oxidized thiophene oligomers

    NASA Astrophysics Data System (ADS)

    Dai, Yafei; Wei, Chengwei; Blaisten-Barojas, Estela

    2013-11-01

    The effect of oxidation on the energetics and structure of thiophene (Th) oligomers is studied with density functional theory at the B3PW91/6-311++G(d,p) level. Neutral n-Th oligomers (2 < n < 13) are gently curved planar chains. Ionization potential and electron affinity results show that n-Th oligomers are easier to be oxidized as their chain length increases. Oxidation states +2, +4, +6, and +8 are energetically stable in 12-Th. Upon oxidation the conjugated backbone of 12-Th switches from extended benzenoid phase to quinoid phase localized on groups of monomers regularly spaced along the chain. Oxidized states +2, +4, +6, and +8 of 12-Th display two +1e localized at the ends of their chains only because of the finite size of the chains. In 12-Th this end-effect extends over the two terminal monomers forming a positive-negative charge duet. This peculiar charge localization makes n-Th oligomers different from other conducting polymers with similar structure, such as polypyrrole. The spectrum of single-electron molecular states of oxidized 12-Th displays two localized single-electron states in the HOMO-LUMO energy gap per +2 oxidation state. Oligothiophene 12-Th doped with F atoms at 1:2 concentration presents a charge transfer of 3.4 e from oligomer to dopants that increases to 4.8 e in the presence of solvent. The charge distribution in these F-doped oligomers is similar to the +4 oxidation state of 12-Th. It is predicted that dopants produce an enhanced charge transfer localized in the proximity of their locations enhancing the formation of bipolarons in the central part of the oligomer chain.

  12. A Mechanism of Subunit Recruitment in Human Small Heat Shock Protein Oligomers

    PubMed Central

    2016-01-01

    Small heat shock proteins (sHSPs) make up a class of molecular chaperones broadly observed across organisms. Many sHSPs form large oligomers that undergo dynamic subunit exchange that is thought to play a role in chaperone function. Though remarkably heterogeneous, sHSP oligomers share three types of intermolecular interactions that involve all three defined regions of a sHSP: the N-terminal region (NTR), the conserved α-crystallin domain (ACD), and a C-terminal region (CTR). Here we define the structural interactions involved in incorporation of a subunit into a sHSP oligomer. We demonstrate that a minimal ACD dimer of the human sHSP, HSPB5, interacts with an HSPB5 oligomer through two types of interactions: (1) interactions with CTRs in the oligomer and (2) via exchange into and out of the dimer interface composed of two ACDs. Unexpectedly, although dimers are thought to be the fundamental building block for sHSP oligomers, our results clearly indicate that subunit exchange into and out of oligomers occurs via monomers. Using structure-based mutants, we show that incorporation of a subunit into an oligomer is predicated on recruitment of the subunit via its interaction with CTRs on an oligomer. Both the rate and extent of subunit incorporation depend on the accessibility of CTRs within an HSPB5 oligomer. We show that this mechanism also applies to formation of heterooligomeric sHSP species composed of HSPB5 and HSPB6 and is likely general among sHSPs. Finally, our observations highlight the importance of NTRs in the thermodynamic stability of sHSP oligomers. PMID:26098708

  13. Heat Resistant Characteristics of Major Royal Jelly Protein 1 (MRJP1) Oligomer

    PubMed Central

    Moriyama, Takanori; Ito, Aimi; Omote, Sumire; Miura, Yuri; Tsumoto, Hiroki

    2015-01-01

    Soluble royal jelly protein is a candidate factor responsible for mammiferous cell proliferation. Major royal jelly protein 1 (MRJP1), which consists of oligomeric and monomeric forms, is an abundant proliferative protein in royal jelly. We previously reported that MRJP1 oligomer has biochemical heat resistance. Therefore, in the present study, we investigated the effects of several heat treatments (56, 65 and 96°C) on the proliferative activity of MRJP1 oligomer. Heat resistance studies showed that the oligomer molecular forms were slightly maintained until 56℃, but the molecular forms were converted to macromolecular heat-aggregated MRJP1 oligomer at 65℃ and 96℃. But, the growth activity of MRJP1 oligomer treated with 96°C was slightly attenuated when compared to unheated MRJP1 oligomer. On the other hand, the cell proliferation activity was preserved until 96℃ by the cell culture analysis of Jurkat cells. In contrast, those of IEC-6 cells were not preserved even at 56°C. The present observations suggest that the bioactive heat-resistance properties were different by the origin of the cells. The cell proliferation analysis showed that MRJP1 oligomer, but not MRJP2 and MRJP3, significantly increased cell numbers, suggesting that MRJP1 oligomer is the predominant proliferation factor for mammiferous cells. PMID:26020775

  14. Solvent induced track sensitization. Extraction of oligomers

    NASA Astrophysics Data System (ADS)

    Apel, P.; Angert, N.; Brüchle, W.; Hermann, H.; Kampschulte, U.; Klein, P.; Kravets, L. I.; Oganessian, Yu. Ts.; Remmert, G.; Spohr, R.; Steckenreiter, T.; Trautmann, C.; Vetter, J.

    1994-04-01

    Oligomer extraction from polyethylene terephthalate (PET) irradiated by xenon ions of 11.4 MeV/u is investigated using UV spectrophotometry and gel permeation chromatography (GPC). The cyclic trimer is identified as the predominant diffusing species removed during extraction by dimethyl formamide (DMF). Extraction dynamics is modeled by a rapid (time constant ≈ 2 min) and a slow (time constant ≈ 100 min) diffusion process attributed to the latent ion tracks and to the virgin material, respectively. Thereby latent tracks act simultaneously as irrigation and drainage pipes for the transfer of the solvent into and the extraction of oligomers from the polymer matrix. Thus tracks help to release osmotic pressure differences and to avoid blistering of the unirradiated polymer during solvent exchange. The total extracted mass per track shows a characteristic decrease with increasing ion fluence interpreted as oxygen effect, due to the decreasing supply of oxygen in the sample during irradiation. The extractable mass corresponds to an equivalent track diameter of initially around 10 nm contracting with increasing ion fluence to an asymptotic value around 3 nm.

  15. Amplified spontaneous emission from a new 4-triarylamine substituted 1,8-naphthalimide semiconductor oligomer

    NASA Astrophysics Data System (ADS)

    Lu, Wu; Tu, Guoli; Zhong, Bo; Ma, Dongge; Wang, Lixiang; Jing, Xiabin; Wang, Fosong

    2005-06-01

    Amplified spontaneous emission has been observed in a new semiconductor oligomer of 2-decyl-6-{[4'-(naphthalene-1-yl-phenyl-amino)-biphenyl-4-yl]-[4-(naphthalene-1-yl-phenyl-amino)-phenyl]-amino}-benzo[ de]isoquinoline-1,3-dione (4-triarylamine substituted 1,8-naphthalimide TAANPI) doped polymer films pumped by the second harmonic of a Nd:YAG laser. The dependence of the threshold and gain on the oligomer concentration in polymer was studied in detail. It was found that the semiconductor oligomer shows low threshold, high gain and low loss even though the doped oligomer concentration is up to 60%, indicating a low concentration quenching effect. This demonstrates that the oligomer could be a promising candidate as gain medium for organic diode lasers.

  16. Peripheral inflammation facilitates Abeta fiber-mediated synaptic input to the substantia gelatinosa of the adult rat spinal cord.

    PubMed

    Baba, H; Doubell, T P; Woolf, C J

    1999-01-15

    Whole-cell patch-clamp recordings were made from substantia gelatinosa (SG) neurons in thick adult rat transverse spinal cord slices with attached dorsal roots to study changes in fast synaptic transmission induced by peripheral inflammation. In slices from naive rats, primary afferent stimulation at Abeta fiber intensity elicited polysynaptic EPSCs in only 14 of 57 (25%) SG neurons. In contrast, Abeta fiber stimulation evoked polysynaptic EPSCs in 39 of 62 (63%) SG neurons recorded in slices from rats inflamed by an intraplantar injection of complete Freund's adjuvant (CFA) 48 hr earlier (p < 0.001). Although the peripheral inflammation had no significant effect on the threshold and conduction velocities of Abeta, Adelta, and C fibers recorded in dorsal roots, the mean threshold intensity for eliciting EPSCs was significantly lower in cells recorded from rats with inflammation (naive: 33.2 +/- 15.1 microA, n = 57; inflamed: 22.8 +/- 11.3 microA, n = 62, p < 0.001), and the mean latency of EPSCs elicited by Abeta fiber stimulation in CFA-treated rats was significantly shorter than that recorded from naive rats (3.3 +/- 1.8 msec, n = 36 vs 6.0 +/- 3.5 msec, n = 12; p = 0.010). Abeta fiber stimulation evoked polysynaptic IPSCs in 4 of 25 (16%) cells recorded from naive rat preparations and 14 of 26 (54%) SG neurons from CFA-treated rats (p < 0.001). The mean threshold intensity for IPSCs was also significantly lower in CFA-treated rats (naive: 32.5 +/- 15.7 microA, n = 25; inflamed: 21. 9 +/- 9.9 microA, n = 26, p = 0.013). The facilitation of Abeta fiber-mediated input into the substantia gelatinosa after peripheral inflammation may contribute to altered sensory processing. PMID:9880605

  17. Small Glycosylated Lignin Oligomers Are Stored in Arabidopsis Leaf Vacuoles

    PubMed Central

    Dima, Oana; Morreel, Kris; Vanholme, Bartel; Kim, Hoon; Ralph, John; Boerjan, Wout

    2015-01-01

    Lignin is an aromatic polymer derived from the combinatorial coupling of monolignol radicals in the cell wall. Recently, various glycosylated lignin oligomers have been revealed in Arabidopsis thaliana. Given that monolignol oxidation and monolignol radical coupling are known to occur in the apoplast, and glycosylation in the cytoplasm, it raises questions about the subcellular localization of glycosylated lignin oligomer biosynthesis and their storage. By metabolite profiling of Arabidopsis leaf vacuoles, we show that the leaf vacuole stores a large number of these small glycosylated lignin oligomers. Their structural variety and the incorporation of alternative monomers, as observed in Arabidopsis mutants with altered monolignol biosynthesis, indicate that they are all formed by combinatorial radical coupling. In contrast to the common believe that combinatorial coupling is restricted to the apoplast, we hypothesized that the aglycones of these compounds are made within the cell. To investigate this, leaf protoplast cultures were cofed with 13C6-labeled coniferyl alcohol and a 13C4-labeled dimer of coniferyl alcohol. Metabolite profiling of the cofed protoplasts provided strong support for the occurrence of intracellular monolignol coupling. We therefore propose a metabolic pathway involving intracellular combinatorial coupling of monolignol radicals, followed by oligomer glycosylation and vacuolar import, which shares characteristics with both lignin and lignan biosynthesis. PMID:25700483

  18. Rectification mechanism in diblock oligomer molecular diodes.

    PubMed

    Oleynik, I I; Kozhushner, M A; Posvyanskii, V S; Yu, L

    2006-03-10

    We investigated a mechanism of rectification in diblock oligomer diode molecules that have recently been synthesized and showed a pronounced asymmetry in the measured I-V spectrum. The observed rectification effect is due to the resonant nature of electron transfer in the system and the localization properties of bound state wave functions of resonant states of the tunneling electron interacting with an asymmetric molecule in an electric field. The asymmetry of the tunneling wave function is enhanced or weakened depending on the polarity of the applied bias. The conceptually new theoretical approach, the Green's function theory of sub-barrier scattering, is able to provide a physically transparent explanation of this rectification effect based on the concept of the bound state spectrum of a tunneling electron. The theory predicts the characteristic features of the I-V spectrum in qualitative agreement with experiment. PMID:16606295

  19. Enzymatic hydrolysis of PTT polymers and oligomers.

    PubMed

    Eberl, A; Heumann, S; Kotek, R; Kaufmann, F; Mitsche, S; Cavaco-Paulo, A; Gübitz, G M

    2008-05-20

    Oligomers and polymers (film, fabrics) of the linear aromatic polyester poly(trimethylene terephthalate) (PTT) were treated with polyesterases from Thermomyces lanuginosus, Penicillium citrinum, Thermobifida fusca and Fusarium solani pisi. The cutinase from T. fusca was found to release the highest amounts of hydrolysis products from PTT materials and was able to open and hydrolyse a cyclic PTT dimer according to RP-HPLC-UV detection. In contrast, the lipase from T. lanuginosus also showed activity on the PTT fibres and on bis(3-hydroxypropyl) terephthalate (BHPT) but was not able to hydrolyse the polymer film, mono(3-hydroxypropyl) terephthalate (MHPT) nor the cyclic dimer of PTT. As control enzymes inhibited with mercury chloride were used. Surface hydrophilicity changes were investigated with contact angle measurements and the degree of crystallinity changes were determined with DSC. PMID:18405994

  20. Tetracycline prevents Aβ oligomer toxicity through an atypical supramolecular interaction.

    PubMed

    Airoldi, Cristina; Colombo, Laura; Manzoni, Claudia; Sironi, Erika; Natalello, Antonino; Doglia, Silvia Maria; Forloni, Gianluigi; Tagliavini, Fabrizio; Del Favero, Elena; Cantù, Laura; Nicotra, Francesco; Salmona, Mario

    2011-01-21

    The antibiotic tetracycline was reported to possess an anti-amyloidogenic activity on a variety of amyloidogenic proteins both in in vitro and in vivo models. To unveil the mechanism of action of tetracycline on Aβ1-40 and Aβ1-42 at both molecular and supramolecular levels, we carried out a series of experiments using NMR spectroscopy, FTIR spectroscopy, dynamic laser light-scattering (DLS) and atomic force microscopy (AFM). Firstly we showed that the co-incubation of Aβ1-42 oligomers with tetracycline hinders the toxicity towards N2a cell lines in a dose-dependent manner. Therefore, the nature of the interaction between the drug and Aβ oligomers was investigated. To carry out NMR and FTIR studies we have prepared Aβ peptide solutions containing assemblies ranging from monomers to large oligomers. Saturation transfer difference (STD) NMR experiments have shown that tetracycline did not interact with monomers at variance with oligomers. Noteworthy, in this latter case we observed that this interaction was very peculiar since the transfer of magnetization from Aβ oligomers to tetracycline involved all drug protons. In addition, intermolecular cross-peaks between tetracycline and Aβ were not observed in NOESY spectra, indicating the absence of a specific binding site and suggesting the occurrence of a supramolecular interaction. DLS and AFM studies supported this hypothesis since the co-dissolution of Aβ peptides and tetracycline triggered the immediate formation of new aggregates that improved the solubility of Aβ peptides, preventing in this way the progression of the amyloid cascade. Moreover, competitive NMR binding experiments showed for the first time that tetracycline competes with thioflavin T (ThT) in the binding to Aβ peptides. Our data shed light on a novel mechanism of anti-amyloidogenic activity displayed by tetracycline, governed by hydrophobic and charge multiparticle interactions. PMID:21063627

  1. Rescue from tau-induced neuronal dysfunction produces insoluble tau oligomers

    PubMed Central

    Cowan, Catherine M.; Quraishe, Shmma; Hands, Sarah; Sealey, Megan; Mahajan, Sumeet; Allan, Douglas W.; Mudher, Amritpal

    2015-01-01

    Aggregation of highly phosphorylated tau is a hallmark of Alzheimer’s disease and other tauopathies. Nevertheless, animal models demonstrate that tau-mediated dysfunction/toxicity may not require large tau aggregates but instead may be caused by soluble hyper-phosphorylated tau or by small tau oligomers. Challenging this widely held view, we use multiple techniques to show that insoluble tau oligomers form in conditions where tau-mediated dysfunction is rescued in vivo. This shows that tau oligomers are not necessarily always toxic. Furthermore, their formation correlates with increased tau levels, caused intriguingly, by either pharmacological or genetic inhibition of tau kinase glycogen-synthase-kinase-3beta (GSK-3β). Moreover, contrary to common belief, these tau oligomers were neither highly phosphorylated, and nor did they contain beta-pleated sheet structure. This may explain their lack of toxicity. Our study makes the novel observation that tau also forms non-toxic insoluble oligomers in vivo in addition to toxic oligomers, which have been reported by others. Whether these are inert or actively protective remains to be established. Nevertheless, this has wide implications for emerging therapeutic strategies such as those that target dissolution of tau oligomers as they may be ineffective or even counterproductive unless they act on the relevant toxic oligomeric tau species. PMID:26608845

  2. A thermodynamic study of Abeta(16-21) dissociation from a fibril using computer simulations

    NASA Astrophysics Data System (ADS)

    Dias, Cristiano; Mahmoudinobar, Farbod; Su, Zhaoqian

    Here, I will discuss recent all-atom molecular dynamics simulations with explicit water in which we studied the thermodynamic properties of Abeta(16-21) dissociation from an amyloid fibril. Changes in thermodynamics quantities, e.g., entropy, enthalpy, and volume, are computed from the temperature dependence of the free-energy computed using the umbrella sampling method. We find similarities and differences between the thermodynamics of peptide dissociation and protein unfolding. Similarly to protein unfolding, Abeta(16-21) dissociation is characterized by an unfavorable change in enthalpy, a favorable change in the entropic energy, and an increase in the heat capacity. A main difference is that peptide dissociation is characterized by a weak enthalpy-entropy compensation. We characterize dock and lock states of the peptide based on the solvent accessible surface area. The Lennard-Jones energy of the system is observed to increase continuously in lock and dock states as the peptide dissociates. The electrostatic energy increases in the lock state and it decreases in the dock state as the peptide dissociates. These results will be discussed as well as their implication for fibril growth.

  3. Montmorillonite Clay-Catalyzed Synthesis of RNA Oligomers

    NASA Astrophysics Data System (ADS)

    Ferris, J. P.; Miyakawa, S.; Huang, W.; Joshi, P.

    2005-12-01

    It is proposed that catalysis had a central role in the origins of life. This will be illustrated using the montmorillonite clay-catalyzed synthesis of oligomers of RNA from activated monomers, (Ferris and Ertem, 1993) a possible step in the origin of the RNA world (Ferris, 2005). Structural analysis of oligomers formed in the reaction of the activated monomer of 5'-AMP with that of 5'-CMP demonstrated that the oligomers formed were not produced by random synthesis but rather the sequences observed were directed by the montmorillonite catalyst (Miyakawa and Ferris, 2003). RNA oligomers containing up to 40 mers have been synthesized in reactions performed in water at 25 oC in the presence of montmorillonite (Huang and Ferris, 2003). Analysis of the structure elements in these oligomers from the 7 to 39 mers showed that they did not vary. Reaction of D, L-mixtures of the activated monomers of A and U resulted in the formation of greater amounts of the homochiral amounts of dimers and trimers of A than would be expected if there was no selectivity in the reaction. A limited number of the dimers and trimers of U were also formed but here the selectivity was for the formation of an excess of heterochiral products (Joshi et al., 2000). A postulate that explains why homochiral trimers of U are not formed and the significance of catalysis in prebiotic synthesis will be discussed. Ferris, J.P. (2005) Origins of life, molecular basis of. In R.A. Meyers, Ed. Encyclopedia of Molecular Cell Biology and Molecular Medicine, 10. Wiley-VCH Verlag, Weinheim, Germany. Ferris, J.P., and Ertem, G. (1993) Montmorillonite catalysis of RNA oligomer formation in aqueous solution. A model for the prebiotic formation of RNA. J. Am. Chem. Soc., 115, 12270-12275. Huang, W., and Ferris, J.P. (2003) Synthesis of 35-40 mers of RNA oligomers from unblocked monomers. A simple approach to the RNA world. Chem. Commun., 1458-1459. Joshi, P.C., Pitsch, S., and Ferris, J.P. (2000) Homochiral selection

  4. Development of Tc-99m Imaging Agents for Abeta Plaques

    SciTech Connect

    Zhi-Ping, Zhuang; Mei-Ping Kung; Catherihne Hou; Hank F. Kung

    2008-09-26

    Development of SPECT imaging agents based on Tc-99m targeting Aβ plaques is useful for diagnosis of Alzheimer’s disease (AD). A stilbene derivative, [11C]SB-13, showing promise in detecting senile plaques present in AD patients has been reported previously1,2. Based on the 4’-amino-stilbene core structure we have added substituted groups through which a chelating group, N2S2, was conjugated. We report herein a series of Tc-99m labeled stilbene derivative conjugated with a TcO[N2S2] core. The syntheses of stilbenes containing a N2S2 chelating ligand are achieved by a scheme shown. Lipophilic 99mTc stilbene complexes were successfully prepared and purified through HPLC. Preliminary results of in vitro labeling of brain sections from transgenic mice showed very promising plaque labeling. These 99mTc stilbene derivatives are warranted for further evaluations as potential imaging agents targeting amyloid plaques.

  5. Unique Properties of the Rabbit Prion Protein Oligomer.

    PubMed

    Yu, Ziyao; Huang, Pei; Yu, Yuanhui; Zheng, Zhen; Huang, Zicheng; Guo, Chenyun; Lin, Donghai

    2016-01-01

    Prion diseases, also known as transmissible spongiform encephalopathies (TSEs), are a group of fatal neurodegenerative disorders infecting both humans and animals. Recent works have demonstrated that the soluble prion protein oligomer (PrPO), the intermediate of the conformational transformation from the host-derived cellular form (PrPC) to the disease-associated Scrapie form (PrPSc), exerts the major neurotoxicity in vitro and in vivo. Rabbits show strong resistance to TSEs, the underlying mechanism is unclear to date. It is expected that the relative TSEs-resistance of rabbits is closely associated with the unique properties of rabbit prion protein oligomer which remain to be addressed in detail. In the present work, we prepared rabbit prion protein oligomer (recRaPrPO) and human prion protein oligomer (recHuPrPO) under varied conditions, analyzed the effects of pH, NaCl concentration and incubation temperature on the oligomerization, and compared the properties of recRaPrPO and recHuPrPO. We found that several factors facilitated the formation of prion protein oligomers, including low pH, high NaCl concentration, high incubation temperature and low conformational stability of monomeric prion protein. RecRaPrPO was formed more slowly than recHuPrPO at physiological-like conditions (< 57°C, < 150 mM NaCl). Furthermore, recRaPrPO possessed higher susceptibility to proteinase K and lower cytotoxicity in vitro than recHuPrPO. These unique properties of recRaPrPO might substantially contribute to the TSEs-resistance of rabbits. Our work sheds light on the oligomerization of prion proteins and is of benefit to mechanistic understanding of TSEs-resistance of rabbits. PMID:27529173

  6. Unique Properties of the Rabbit Prion Protein Oligomer

    PubMed Central

    Yu, Ziyao; Huang, Pei; Yu, Yuanhui; Zheng, Zhen; Huang, Zicheng; Guo, Chenyun; Lin, Donghai

    2016-01-01

    Prion diseases, also known as transmissible spongiform encephalopathies (TSEs), are a group of fatal neurodegenerative disorders infecting both humans and animals. Recent works have demonstrated that the soluble prion protein oligomer (PrPO), the intermediate of the conformational transformation from the host-derived cellular form (PrPC) to the disease-associated Scrapie form (PrPSc), exerts the major neurotoxicity in vitro and in vivo. Rabbits show strong resistance to TSEs, the underlying mechanism is unclear to date. It is expected that the relative TSEs-resistance of rabbits is closely associated with the unique properties of rabbit prion protein oligomer which remain to be addressed in detail. In the present work, we prepared rabbit prion protein oligomer (recRaPrPO) and human prion protein oligomer (recHuPrPO) under varied conditions, analyzed the effects of pH, NaCl concentration and incubation temperature on the oligomerization, and compared the properties of recRaPrPO and recHuPrPO. We found that several factors facilitated the formation of prion protein oligomers, including low pH, high NaCl concentration, high incubation temperature and low conformational stability of monomeric prion protein. RecRaPrPO was formed more slowly than recHuPrPO at physiological-like conditions (< 57°C, < 150 mM NaCl). Furthermore, recRaPrPO possessed higher susceptibility to proteinase K and lower cytotoxicity in vitro than recHuPrPO. These unique properties of recRaPrPO might substantially contribute to the TSEs-resistance of rabbits. Our work sheds light on the oligomerization of prion proteins and is of benefit to mechanistic understanding of TSEs-resistance of rabbits. PMID:27529173

  7. Self-assembly of 33-mer gliadin peptide oligomers.

    PubMed

    Herrera, M G; Benedini, L A; Lonez, C; Schilardi, P L; Hellweg, T; Ruysschaert, J-M; Dodero, V I

    2015-11-28

    The 33-mer gliadin peptide, LQLQPF(PQPQLPY)3PQPQPF, is a highly immunogenic peptide involved in celiac disease and probably in other immunopathologies associated with gliadin. Herein, dynamic light scattering measurements showed that 33-mer, in the micromolar concentration range, forms polydisperse nano- and micrometer range particles in aqueous media. This behaviour is reminiscent of classical association of colloids and we hypothesized that the 33-mer peptide self-assembles into micelles that could be the precursors of 33-mer oligomers in water. Deposition of 33-mer peptide aqueous solution on bare mica generated nano- and microstructures with different morphologies as revealed by atomic force microscopy. At 6 μM, the 33-mer is organised in isolated and clusters of spherical nanostructures. In the 60 to 250 μM concentration range, the spherical oligomers associated mainly in linear and annular arrangements and structures adopting a "sheet" type morphology appeared. At higher concentrations (610 μM), mainly filaments and plaques immersed in a background of nanospherical structures were detected. The occurrence of different morphologies of oligomers and finally the filaments suggests that the unique specific geometry of the 33-mer oligomers has a crucial role in the subsequent condensation and organization of their fractal structures into the final filaments. The self-assembly process on mica is described qualitatively and quantitatively by a fractal diffusion limited aggregation (DLA) behaviour with the fractal dimension in the range of 1.62 ± 0.02 to 1.73 ± 0.03. Secondary structure evaluation of the oligomers by Attenuated Total Reflection FTIR spectroscopy (ATR-FTIR) revealed the existence of a conformational equilibrium of self-assembled structures, from an extended conformation to a more folded parallel beta elongated structures. Altogether, these findings provide structural and morphological information about supramolecular organization of the 33-mer

  8. Ballistic Energy Transport in Oligomers.

    PubMed

    Rubtsova, Natalia I; Qasim, Layla N; Kurnosov, Arkady A; Burin, Alexander L; Rubtsov, Igor V

    2015-09-15

    The development of nanocomposite materials with desired heat management properties, including nanowires, layered semiconductor structures, and self-assembled monolayer (SAM) junctions, attracts broad interest. Such materials often involve polymeric/oligomeric components and can feature high or low thermal conductivity, depending on their design. For example, in SAM junctions made of alkane chains sandwiched between metal layers, the thermal conductivity can be very low, whereas the fibers of ordered polyethylene chains feature high thermal conductivity, exceeding that of many pure metals. The thermal conductivity of nanostructured materials is determined by the energy transport between and within each component of the material, which all need to be understood for optimizing the properties. For example, in the SAM junctions, the energy transport across the metal-chain interface as well as the transport through the chains both determine the overall heat conductivity, however, to separate these contributions is difficult. Recently developed relaxation-assisted two-dimensional infrared (RA 2DIR) spectroscopy is capable of studying energy transport in individual molecules in the time domain. The transport in a molecule is initiated by exciting an IR-active group (a tag); the method records the influence of the excess energy on another mode in the molecule (a reporter). The energy transport time can be measured for different reporters, and the transport speed through the molecule is evaluated. Various molecules were interrogated by RA 2DIR: in molecules without repeating units (disordered), the transport mechanism was expected and found to be diffusive. The transport via an oligomer backbone can potentially be ballistic, as the chain offers delocalized vibrational states. Indeed, the transport regime via three tested types of oligomers, alkanes, polyethyleneglycols, and perfluoroalkanes was found to be ballistic, whereas the transport within the end groups was diffusive

  9. Alzheimer's amyloid-β oligomers rescue cellular prion protein induced tau reduction via the Fyn pathway.

    PubMed

    Chen, Rong-Jie; Chang, Wei-Wei; Lin, Yu-Chun; Cheng, Pei-Lin; Chen, Yun-Ru

    2013-09-18

    Amyloid-β (Aβ) and tau are the pathogenic hallmarks in Alzheimer's disease (AD). Aβ oligomers are considered the actual toxic entities, and the toxicity relies on the presence of tau. Recently, Aβ oligomers have been shown to specifically interact with cellular prion protein (PrP(C)) where the role of PrP(C) in AD is still not fully understood. To investigate the downstream mechanism of PrP(C) and Aβ oligomer interaction and their possible relationships to tau, we examined tau expression in human neuroblastoma BE(2)-C cells transfected with murine PrP(C) and studied the effect under Aβ oligomer treatment. By Western blotting, we found that PrP(C) overexpression down-regulated tau protein and Aβ oligomer binding alleviated the tau reduction induced by wild type but not M128V PrP(C), the high AD risk polymorphic allele in human prion gene. PrP(C) lacking the Aβ oligomer binding site was incapable of rescuing the level of tau reduction. Quantitative RT-PCR showed the PrP(C) effect was attributed to tau reduction at the transcription level. Treatment with Fyn pathway inhibitors, Fyn kinase inhibitor PP2 and MEK inhibitor U0126, reversed the PrP(C)-induced tau reduction and Aβ oligomer treatment modulated Fyn kinase activity. The results suggested Fyn pathway regulated Aβ-PrP(C)-tau signaling. Overall, our results demonstrated that PrP(C) down-regulated tau via the Fyn pathway and the effect can be regulated by Aβ oligomers. Our study facilitated the understanding of molecular mechanisms among PrP(C), tau, and Aβ oligomers. PMID:23805846

  10. Aggregation of amyloid Abeta((1-40)) peptide in perdeuterated 2,2,2-trifluoroethanol caused by ultrasound sonication.

    PubMed

    Filippov, Andrei V; Gröbner, Gerhard; Antzutkin, Oleg N

    2010-06-01

    Ultrasound sonication of protein and peptide solutions is routinely used in biochemical, biophysical, pharmaceutical and medical sciences to facilitate and accelerate dissolution of macromolecules in both aqueous and organic solvents. However, the impact of ultrasound waves on folding/unfolding of treated proteins, in particular, on aggregation kinetics of amyloidogenic peptides and proteins is not understood. In this work, effects of ultrasound sonication on the misfolding and aggregation behavior of the Alzheimer's Abeta((1-40))-peptide is studied by pulsed-field gradient (PFG) spin-echo diffusion NMR and UV circular dichroism (CD) spectroscopy. Upon simple dissolution of Abeta((1-40)) in perdeuterated trifluoroethanol, CF(3)-CD(2)-OD (TFE-d(3)), the peptide is present in the solution as a stable monomer adopting alpha-helical secondary structural motifs. The self-diffusion coefficient of Abeta((1-40)) monomers in TFE-d(3) was measured as 1.35 x 10(-10) m(2) s(-1), reflecting its monomeric character. However, upon ultrasonic sonication for less than 5 min, considerable populations of Abeta molecules (ca 40%) form large aggregates as reflected in diffusion coefficients smaller than 4.0 x 10(-13) m(2) s(-1). Sonication for longer times (up to 40 min in total) effectively reduces the fraction of these aggregates in (1)H PFG NMR spectra to ca 25%. Additionally, absorption below 230 nm increased significantly upon sonication treatment, an observation, which also clearly confirms the ongoing aggregation process of Abeta((1-40)) in TFE-d(3). Surprisingly, upon ultrasound sonication only small changes in the peptide secondary structure were detected by CD: the peptide molecules mainly adopt alpha-helical motifs in both monomers and aggregates formed upon sonication. PMID:20474020

  11. An electric nose based on arylenevinylene polymers and oligomers

    NASA Astrophysics Data System (ADS)

    de Wit, Michael

    An electronic nose is an instrument, which comprises an array of electronic chemical sensors with partial specificity and an appropriate pattern-recognition system, capable of recognising simple or complex odours. Our efforts are centred around the sensors part of the nose. In fact, we applied a number of polymeric and oligomeric members of the arylenevinylene group of molecules as the active layer for conductimetric sensors (chemiresistors). The electric resistance of the active layer changes when it is exposed to vapors. The response of the sensor on a vapour is defined as the fractional, percentual change of the resistance compared to that in clean air. We made the sensors by depositing the organic layers on a substrate containing pre-printed gold contacts. At first we tested poly(2,5-thienylene vinylene) (PTV). A synthetic method was employed in which a soluble methoxy-precursor polymer of PTV was isolated, which was then spin-coated onto the substrate, and after being converted thermally to PTV, subsequently doped by iodine. The values of the responses of the PTV sensors are comparable to those sensors based on other conducting polymers, but the (partial) selectivity for the vapors is different. The responses of the PTV sensor are linearly related to the concentration. Incomplete conversion of the precursor polymer to the final PTV leads to copolymers of methoxy-PTV and PTV itself varying inter alia in the degree of conjugation. Chemiresistors based on these new materials show an affinity to vapors differing from that of PTV. We discovered that the arylenevinylenes need not to be of polymeric nature for this application. In fact, the arylenevinylene oligomers perform better. The oligomers are easier to modify and to process than polymers. We tested 2,5-dimethoxy-1,4-bis(3,4,5-trimethoxystyrylbenzene) (OMT) in its pure form and in blends with polycarbonate. The responses of these oligomeric sensors are on the average five times higher than those of the

  12. Alzheimer therapy with an antibody against N-terminal Abeta 4-X and pyroglutamate Abeta 3-X

    PubMed Central

    Antonios, Gregory; Borgers, Henning; Richard, Bernhard C.; Brauß, Andreas; Meißner, Julius; Weggen, Sascha; Pena, Vladimir; Pillot, Thierry; Davies, Sarah L.; Bakrania, Preeti; Matthews, David; Brownlees, Janet; Bouter, Yvonne; Bayer, Thomas A.

    2015-01-01

    Full-length Aβ1-42 and Aβ1-40, N-truncated pyroglutamate Aβ3-42 and Aβ4-42 are major variants in the Alzheimer brain. Aβ4-42 has not been considered as a therapeutic target yet. We demonstrate that the antibody NT4X and its Fab fragment reacting with both the free N-terminus of Aβ4-x and pyroglutamate Aβ3-X mitigated neuron loss in Tg4-42 mice expressing Aβ4-42 and completely rescued spatial reference memory deficits after passive immunization. NT4X and its Fab fragment also rescued working memory deficits in wild type mice induced by intraventricular injection of Aβ4-42. NT4X reduced pyroglutamate Aβ3-x, Aβx-40 and Thioflavin-S positive plaque load after passive immunization of 5XFAD mice. Aβ1-x and Aβx-42 plaque deposits were unchanged. Importantly, for the first time, we demonstrate that passive immunization using the antibody NT4X is therapeutically beneficial in Alzheimer mouse models showing that N-truncated Aβ starting with position four in addition to pyroglutamate Aβ3-x is a relevant target to fight Alzheimer’s disease. PMID:26626428

  13. Circular dichroism from Fano resonances in planar chiral oligomers

    NASA Astrophysics Data System (ADS)

    Hopkins, Ben; Poddubny, Alexander N.; Miroshnichenko, Andrey E.; Kivshar, Yuri S.

    2015-05-01

    Here we present a general approach for describing the physics of Fano resonances in nanoparticle oligomers. It is shown that the interference of nonorthogonal collective eigenmodes is a sufficient condition to produce Fano resonances. We then show that such nonorthogonality between eigenmodes also permits the existence of a new form circular dichroism in the absorption and scattering cross-sections, even when circular dichroism is forbidden in the extinction cross-section.

  14. Redox effects on the excited-state lifetime in chlorosomes and bacteriochlorophyll c oligomers.

    PubMed Central

    van Noort, P I; Zhu, Y; LoBrutto, R; Blankenship, R E

    1997-01-01

    Oligomers of [E,E] BChl CF (8, 12-diethyl bacteriochlorophyll c esterified with farnesol (F)) and [Pr,E] BChl CF (analogously, M methyl, Pr propyl) in hexane and aqueous detergent or lipid micelles were studied by means of steady-state absorption, time-resolved fluorescence, and electron spin resonance spectroscopy. The maximum absorption wavelength, excited-state dynamics, and electron spin resonance (EPR) linewidths are similar to those of native and reconstituted chlorosomes of Chlorobium tepidum. The maximum absorption wavelength of oligomers of [E,E] BChl CF was consistently blue-shifted as compared to that of [Pr,E] BChl CF oligomers, which is ascribed to the formation of smaller oligomers with [E,E] BChl CF than [Pr,E] BChl CF. Time-resolved fluorescence measurements show an excited-state lifetime of 10 ps or less in nonreduced samples of native and reconstituted chlorosomes of Chlorobium tepidum. Under reduced conditions the excited-state lifetime increased to tens of picoseconds, and energy transfer to BChl a or long-wavelength absorbing BChl c was observed. Oligomers of [E,E] BChl CF and [Pr,E] BChl CF in aqueous detergent or lipid micelles show a similar short excited-state lifetime under nonreduced conditions and an increase up to several tens of picoseconds upon reduction. These results indicate rapid quenching of excitation energy in nonreduced samples of chlorosomes and aqueous BChl c oligomers. EPR spectroscopy shows that traces of oxidized BChl c radicals are present in nonreduced and absent in reduced samples of chlorosomes and BChl c oligomers. This suggests that the observed short excited-state lifetimes in nonreduced samples of chlorosomes and BChl c oligomers may be ascribed to excited-state quenching by BChl c radicals. The narrow EPR linewidth suggests that the BChl c are arranged in clusters of 16 and 6 molecules in chlorosomes of Chlorobium tepidum and Chloroflexus aurantiacus, respectively. PMID:8994616

  15. In Vitro and In Vivo Neurotoxicity of Prion Protein Oligomers

    PubMed Central

    Simoneau, Steve; Rezaei, Human; Salès, Nicole; Kaiser-Schulz, Gunnar; Lefebvre-Roque, Maxime; Vidal, Catherine; Fournier, Jean-Guy; Comte, Julien; Wopfner, Franziska; Grosclaude, Jeanne; Schätzl, Hermann; Lasmézas, Corinne Ida

    2007-01-01

    The mechanisms underlying prion-linked neurodegeneration remain to be elucidated, despite several recent advances in this field. Herein, we show that soluble, low molecular weight oligomers of the full-length prion protein (PrP), which possess characteristics of PrP to PrPsc conversion intermediates such as partial protease resistance, are neurotoxic in vitro on primary cultures of neurons and in vivo after subcortical stereotaxic injection. Monomeric PrP was not toxic. Insoluble, fibrillar forms of PrP exhibited no toxicity in vitro and were less toxic than their oligomeric counterparts in vivo. The toxicity was independent of PrP expression in the neurons both in vitro and in vivo for the PrP oligomers and in vivo for the PrP fibrils. Rescue experiments with antibodies showed that the exposure of the hydrophobic stretch of PrP at the oligomeric surface was necessary for toxicity. This study identifies toxic PrP species in vivo. It shows that PrP-induced neurodegeneration shares common mechanisms with other brain amyloidoses like Alzheimer disease and opens new avenues for neuroprotective intervention strategies of prion diseases targeting PrP oligomers. PMID:17784787

  16. A HRMS study of oligomer formation through aqueous phase photooxidation of methylvinyl-ketone and methacrolein

    NASA Astrophysics Data System (ADS)

    Salque-moreton, G.; Liu, Y.; Voisin, D.; Siekmann, F.; Renard, P.; Monod, A.; Thissen, R.

    2012-04-01

    Global estimates of secondary organic aerosol (SOA) formation flux show that the current descriptions miss a large fraction of the sources. Aqueous phase photochemistry in cloud droplets and deliquescent aerosol may provide some of this missing flux. Organic reactions in those media, particularly leading to higher molecular weight products thus need better understanding. Here, we investigated the aqueous phase photooxidation of methacrolein (MACR) and methylvinyl-ketone (MVK), which are the two main oxidation products of isoprene, the volatile organic compound (VOC) that is mostly emitted on the global scale. In our experiments, photolysis of H2O2 provided OH radicals whose reaction with MACR or MVK produced oligomers. Firstly, oligomers were analyzed using electrospray ionization coupled with high-resolution linear ion trap Orbitrap™ (Thermo Corp.) mass spectrometer (HRMS). This technique enabled to propose the unambiguous elemental composition of the produced compounds as data were collected for a mass range of m/z 50-2000 amu. The mass of oligomers increased strongly in positive and negative ionization modes when initial concentrations of MACR and MVK were increased from 2 to 20 mM. Typical regular patterns of oligomer formation were observed for both precursors, and extended up to 1400 amu. These patterns were very different from each other for the two precursors although both showed regular mass differences of 70 amu. In addition, we used a Kendrick analysis and identified more than 20 distinct chemical oligomer series produced by photooxidation of both MACR and MVK, some of which reaching more than 1400 amu. The HRMS investigations allowed us to propose a mechanism of production of oligomers. Upon nebulization, both oligomer systems produce SOA with a mass yield of 2-12%. This mass yield increases with reaction time and precursor concentration. Moreover, time evolution of the oligomer systems observed with the Orbitrap will be compared to HR

  17. Sub-cellular temporal and spatial distribution of electrotransferred LNA/DNA oligomer.

    PubMed

    Orio, Julie; Bellard, Elisabeth; Baaziz, Houda; Pichon, Chantal; Mouritzen, Peter; Rols, Marie-Pierre; Teissié, Justin; Golzio, Muriel; Chabot, Sophie

    2013-01-01

    Low biological activity and inefficient targeted delivery in vivo have hindered RNA interference (RNAi)-based therapy from realising its full clinical potential. To overcome these hurdles, progresses have been made to develop new technologies optimizing oligonucleotides chemistry on one hand and achieving its effective delivery on the other hand. In this report, we achieved, by using the electropulsation technique (EP), efficient cellular delivery of chemically-modified oligonucleotide: The locked nucleic acid (LNA)/DNA oligomer. We used single cell level confocal fluorescence microscopy to follow the spatial and temporal distribution of electrotransferred cyanine 5 (Cy5)-labeled LNA/DNA oligomer. We observed that EP allowed LNA/DNA oligomer cellular uptake providing the oligomer a rapid access to the cytoplasm of HeLa cells. Within a few minutes after electrotransfer, Cy5-LNA/DNA oligomers shuttle from cytoplasm to nucleus whereas in absence of pulses application, Cy5-LNA/DNA oligomers were not detected. We then observed a redistribution of the Cy5 fluorescence that accumulated over time into cytoplasmic organelles. To go further and to identify these compartments, we used the HeLa GFP-Rab7 cell line to visualise late endosomes, and lysosomal or mitochondrial specific markers. Our results showed that the EP technique allowed direct entry into the cytoplasm of the Cy5-LNA/DNA oligomer bypassing the endocytosic pathway. However, in absence of pulses application, Cy5-LNA/DNA oligomer were able to enter cells through the endocytosic pathway. We demonstrated that EP is an efficient technique for LNA-based oligonucleotides delivery offering strong advantages by avoiding the endolysosomal compartmentalization, giving a rapid and free access to the cytoplasm and the nucleus where they can find their targets. PMID:23946765

  18. Familial Alzheimer's disease-linked presenilin 1 variants elevate Abeta1-42/1-40 ratio in vitro and in vivo.

    PubMed

    Borchelt, D R; Thinakaran, G; Eckman, C B; Lee, M K; Davenport, F; Ratovitsky, T; Prada, C M; Kim, G; Seekins, S; Yager, D; Slunt, H H; Wang, R; Seeger, M; Levey, A I; Gandy, S E; Copeland, N G; Jenkins, N A; Price, D L; Younkin, S G; Sisodia, S S

    1996-11-01

    Mutations in the presenilin 1 (PS1) and presenilin 2 genes cosegregate with the majority of early-onset familial Alzheimer's disease (FAD) pedigrees. We now document that the Abeta1-42(43)/Abeta1-40 ratio in the conditioned media of independent N2a cell lines expressing three FAD-linked PS1 variants is uniformly elevated relative to cells expressing similar levels of wild-type PS1. Similarly, the Abeta1-42(43)/Abeta1-40 ratio is elevated in the brains of young transgenic animals coexpressing a chimeric amyloid precursor protein (APP) and an FAD-linked PS1 variant compared with brains of transgenic mice expressing APP alone or transgenic mice coexpressing wild-type human PS1 and APP. These studies provide compelling support for the view that one mechanism by which these mutant PS1 cause AD is by increasing the extracellular concentration of Abeta peptides terminating at 42(43), species that foster Abeta deposition. PMID:8938131

  19. Low Molecular Weight Oligomers with Aromatic Backbone as Efficient Nonviral Gene Vectors.

    PubMed

    Luan, Chao-Ran; Liu, Yan-Hong; Zhang, Ji; Yu, Qing-Ying; Huang, Zheng; Wang, Bing; Yu, Xiao-Qi

    2016-05-01

    A series of oligomers were synthesized via ring-opening polymerization. Although the molecular weights of these oligomers are only ∼2.5 kDa, they could efficiently bind and condense DNA into nanoparticles. These oligomers gave comparable transfection efficiency (TE) to PEI 25 kDa, while their TE could even increase with the presence of serum, and up to 65 times higher TE than PEI was obtained. The excellent serum tolerance was also confirmed by TEM, flow cytometry, and BSA adsorption assay. Moreover, structure-activity relationship studies revealed some interesting factors. First, oligomers containing aromatic rings in the backbone showed better DNA binding ability. These materials could bring more DNA cargo into the cells, leading to much better TE. Second, the isomerism of the disubstituted phenyl group on the oligomer backbone has large effect on the transfection. The ortho-disubstituted ones gave at least 1 order of magnitude higher TE than meta- or para-disubstituted oligomers. Gel electrophoresis involving DNase and heparin indicated that the difficulty to release DNA might contribute to the lower TE of the latter. Such clues may help us to design novel nonviral gene vectors with high efficiency and biocompatibility. PMID:27077449

  20. Application of an Amyloid Beta Oligomer Standard in the sFIDA Assay.

    PubMed

    Kühbach, Katja; Hülsemann, Maren; Herrmann, Yvonne; Kravchenko, Kateryna; Kulawik, Andreas; Linnartz, Christina; Peters, Luriano; Wang, Kun; Willbold, Johannes; Willbold, Dieter; Bannach, Oliver

    2016-01-01

    Still, there is need for significant improvements in reliable and accurate diagnosis for Alzheimer's disease (AD) at early stages. It is widely accepted that changes in the concentration and conformation of amyloid-β (Aβ) appear several years before the onset of first symptoms of cognitive impairment in AD patients. Because Aβ oligomers are possibly the major toxic species in AD, they are a promising biomarker candidate for the early diagnosis of the disease. To date, a variety of oligomer-specific assays have been developed, many of them ELISAs. Here, we demonstrate the sFIDA assay, a technology highly specific for Aβ oligomers developed toward single particle sensitivity. By spiking stabilized Aβ oligomers to buffer and to body fluids from control donors, we show that the sFIDA readout correlates with the applied concentration of stabilized oligomers diluted in buffer, cerebrospinal fluid (CSF), and blood plasma over several orders of magnitude. The lower limit of detection was calculated to be 22 fM of stabilized oligomers diluted in PBS, 18 fM in CSF, and 14 fM in blood plasma. PMID:26858588

  1. Surface-enhanced spectroscopy on plasmonic oligomers assembled by AFM nanoxerography

    NASA Astrophysics Data System (ADS)

    Moutet, Pierre; Sangeetha, Neralagatta M.; Ressier, Laurence; Vilar-Vidal, Noelia; Comesaña-Hermo, Miguel; Ravaine, Serge; Vallée, Renaud A. L.; Gabudean, Ana Maria; Astilean, Simion; Farcau, Cosmin

    2015-01-01

    Surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF) from individual plasmonic oligomers are investigated by confocal Raman micro-spectroscopy and time-resolved fluorescence microscopy coupled to steady state micro-spectroscopy. The nanoparticle (NP) oligomers are made of either ligand protected Au or Au@SiO2 core-shell colloidal NPs, which were assembled into ordered arrays by atomic force microscopy (AFM) nanoxerography. A strong dependence of the SERS emission on the polarization of incident light relative to the specific geometry of the plasmonic oligomer was observed. The SEF studies, performed on a large collection of NP oligomers of various known configurations showed interesting fluorophore decay rate modification and red-shift of the emission spectra. The experimental results are analyzed theoretically by employing finite-difference time-domain (FDTD) simulations on equivalent realistic structures, within the local density of optical states (LDOS) framework. The presented results, together with the proven potential of the LDOS approach as a useful common tool for analyzing both SERS and SEF effects further the general understanding of plasmon-related phenomena in nanoparticle oligomers.Surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF) from individual plasmonic oligomers are investigated by confocal Raman micro-spectroscopy and time-resolved fluorescence microscopy coupled to steady state micro-spectroscopy. The nanoparticle (NP) oligomers are made of either ligand protected Au or Au@SiO2 core-shell colloidal NPs, which were assembled into ordered arrays by atomic force microscopy (AFM) nanoxerography. A strong dependence of the SERS emission on the polarization of incident light relative to the specific geometry of the plasmonic oligomer was observed. The SEF studies, performed on a large collection of NP oligomers of various known configurations showed interesting fluorophore decay rate

  2. Hypoglycemic activities of A- and B-type procyanidin oligomer-rich extracts from different Cinnamon barks.

    PubMed

    Lu, Zhaolian; Jia, Qi; Wang, Rui; Wu, Ximin; Wu, Yingchun; Huang, Caiguo; Li, Yiming

    2011-02-15

    Procyanidin oligomers in Cinnamon are thought to be responsible for the biological activity in the treatment of diabetes mellitus (DM). To clarify types of procyanidin oligomers in different Cinnamon species and investigate their different effects, the present study investigated procyanidin oligomers in polyphenolic oligomer-rich extracts of three Cinnamon samples by LC-MS methods, and their hypoglycemic activities were detected in vivo and in vitro. The results showed that two of the three samples from Cinnamomum cassia were rich in B-type procyanidin oligomers, and the other sample was rich in A-type procyanidin oligomers. The Cinnamon extracts were administered at doses of 200 and 300 mg/kg body wt. in high-fat diet-fed and low-dose streptozotocin (STZ)-induced diabetic mice for 14 days. The results showed that blood glucose concentrations were significantly decreased in all Cinnamon extract groups compared with the control group (p<0.05). Administration of the Cinnamon extracts significantly increased the consumption of extracellular glucose in insulin-resistant HepG2 cells and normal HepG2 cells compared with the control group. These results suggest that both A- and B-type procyanidin oligomers in different Cinnamon species have hypoglycemic activities and may improve insulin sensitivity in type 2 DM. PMID:20851586

  3. Incomplete pneumolysin oligomers form membrane pores.

    PubMed

    Sonnen, Andreas F-P; Plitzko, Jürgen M; Gilbert, Robert J C

    2014-01-01

    Pneumolysin is a member of the cholesterol-dependent cytolysin (CDC) family of pore-forming proteins that are produced as water-soluble monomers or dimers, bind to target membranes and oligomerize into large ring-shaped assemblies comprising approximately 40 subunits and approximately 30 nm across. This pre-pore assembly then refolds to punch a large hole in the lipid bilayer. However, in addition to forming large pores, pneumolysin and other CDCs form smaller lesions characterized by low electrical conductance. Owing to the observation of arc-like (rather than full-ring) oligomers by electron microscopy, it has been hypothesized that smaller oligomers explain smaller functional pores. To investigate whether this is the case, we performed cryo-electron tomography of pneumolysin oligomers on model lipid membranes. We then used sub-tomogram classification and averaging to determine representative membrane-bound low-resolution structures and identified pre-pores versus pores by the presence of membrane within the oligomeric curve. We found pre-pore and pore forms of both complete (ring) and incomplete (arc) oligomers and conclude that arc-shaped oligomeric assemblies of pneumolysin can form pores. As the CDCs are evolutionarily related to the membrane attack complex/perforin family of proteins, which also form variably sized pores, our findings are of relevance to that class of proteins as well. PMID:24759615

  4. Amyloid β oligomers elicit mitochondrial transport defects and fragmentation in a time-dependent and pathway-specific manner.

    PubMed

    Rui, Yanfang; Zheng, James Q

    2016-01-01

    Small oligomeric forms of amyloid-β (Aβ) are believed to be the culprit for declined brain functions in AD in part through their impairment of neuronal trafficking and synaptic functions. However, the precise cellular actions of Aβ oligomers and underlying mechanisms in neurons remain to be fully defined. Previous studies have identified mitochondria as a major target of Aβ toxicity contributing to early cognitive decline and memory loss in neurodegenerative diseases including Alzheimer's disease (AD). In this study, we report that Aβ oligomers acutely elicit distinct effects on the transport and integrity of mitochondria. We found that acute exposure of hippocampal neurons to Aβ oligomers from either synthetic peptides or AD brain homogenates selectively impaired fast transport of mitochondria without affecting the movement of late endosomes and lysosomes. Extended exposure of hipoocampal neurons to Aβ oligomers was found to result in mitochondrial fragmentation. While both mitochondrial effects induced by Aβ oligomers can be abolished by the inhibition of GSK3β, they appear to be independent from each other. Aβ oligomers impaired mitochondrial transport through HDAC6 activation whereas the fragmentation involved the GTPase Drp-1. These results show that Aβ oligomers can acutely disrupt mitochondrial transport and integrity in a time-dependent and pathway-specific manner. These findings thus provide new insights into Aβ-induced mitochondrial defects that may contribute to neuronal dysfunction and AD pathogenesis. PMID:27535553

  5. Temperature sensitivity trends and multi-stimuli sensitive behavior in amphiphilic oligomers.

    PubMed

    Wang, Feng; Klaikherd, Akamol; Thayumanavan, S

    2011-08-31

    A series of oligomers, containing oligo(ethylene glycol) (OEG) moieties, with the same composition of amphiphilic functionalities has been designed, synthesized, and characterized on the basis of their temperature-sensitive behavior. The non-covalent amphiphilic aggregates, formed from these molecules, influence their temperature sensitivity. Covalent tethering of the amphiphilic units also has a significant influence on their temperature sensitivity. The lower critical solution temperatures of these oligomers show increasingly sharp transitions with increasing numbers of OEG functional groups, indicating enhanced cooperativity in dehydration of the OEG moieties when they are covalently tethered. These molecules were also engineered to be concurrently sensitive to enzymatic reaction and pH. This possibility was investigated using porcine liver esterase as the enzyme; we show that enzymatic action on the pentamer lowers its temperature sensitivity. The product moiety from the enzymatic reaction also gives the amphiphilic oligomer a pH-dependent temperature sensitivity. PMID:21739959

  6. Rad54 oligomers translocate and cross-bridge double-stranded DNA to stimulate synapsis

    PubMed Central

    Bianco, Piero R.; Bradfield, Justin J.; Castanza, Lauren R.; Donnelly, Andrea N.

    2007-01-01

    Rad54 is a key component of the eukaryotic recombination machinery. Its presence in DNA strand exchange reactions in vitro results in a significant stimulation in the overall reaction rate. Using untagged Rad54, we show that this stimulation can be attributed to enhancement of the formation of a key reaction intermediate known as DNA networks. Using a novel, single DNA molecule, dual-optical tweezers approach we show how Rad54 stimulates DNA network formation. We discovered that Rad54 oligomers possess a unique ability to cross-bridge or bind dsDNA molecules positioned in close proximity. Further, Rad54 oligomers rapidly translocate dsDNA while simultaneously inducing topological loops in the DNA at the locus of the oligomer. The combination of the cross-bridging and dsDNA translocation activities of Rad54 stimulates the formation of DNA networks, leading to rapid and efficient DNA strand exchange by Rad51. PMID:17949748

  7. Synthesis and g-quadruplex-binding properties of defined acridine oligomers.

    PubMed

    Ferreira, Rubén; Aviñó, Anna; Pérez-Tomás, Ricardo; Gargallo, Raimundo; Eritja, Ramon

    2010-01-01

    The synthesis of oligomers containing two or three acridine units linked through 2-aminoethylglycine using solid-phase methodology is described. Subsequent studies on cell viability showed that these compounds are not cytotoxic. Binding to several DNA structures was studied by competitive dialysis, which showed a clear affinity for DNA sequences that form G-quadruplexes and parallel triplexes. The fluorescence spectra of acridine oligomers were affected strongly upon binding to DNA. These spectral changes were used to calculate the binding constants (K). Log K were found to be in the order of 4-6. PMID:20725626

  8. Surface-enhanced spectroscopy on plasmonic oligomers assembled by AFM nanoxerography.

    PubMed

    Moutet, Pierre; Sangeetha, Neralagatta M; Ressier, Laurence; Vilar-Vidal, Noelia; Comesaña-Hermo, Miguel; Ravaine, Serge; Vallée, Renaud A L; Gabudean, Ana Maria; Astilean, Simion; Farcau, Cosmin

    2015-02-01

    Surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF) from individual plasmonic oligomers are investigated by confocal Raman micro-spectroscopy and time-resolved fluorescence microscopy coupled to steady state micro-spectroscopy. The nanoparticle (NP) oligomers are made of either ligand protected Au or Au@SiO2 core-shell colloidal NPs, which were assembled into ordered arrays by atomic force microscopy (AFM) nanoxerography. A strong dependence of the SERS emission on the polarization of incident light relative to the specific geometry of the plasmonic oligomer was observed. The SEF studies, performed on a large collection of NP oligomers of various known configurations showed interesting fluorophore decay rate modification and red-shift of the emission spectra. The experimental results are analyzed theoretically by employing finite-difference time-domain (FDTD) simulations on equivalent realistic structures, within the local density of optical states (LDOS) framework. The presented results, together with the proven potential of the LDOS approach as a useful common tool for analyzing both SERS and SEF effects further the general understanding of plasmon-related phenomena in nanoparticle oligomers. PMID:25553777

  9. Early vitamin E supplementation in young but not aged mice reduces Abeta levels and amyloid deposition in a transgenic model of Alzheimer's disease.

    PubMed

    Sung, Syuan; Yao, Yuemang; Uryu, Kunihiro; Yang, Hengxuan; Lee, Virginia M-Y; Trojanowski, John Q; Praticò, Domenico

    2004-02-01

    Increased brain oxidative stress is a key feature of Alzheimer's disease (AD) and manifests predominantly as lipid peroxidation. However, clinical evidence that antioxidants can affect the clinical course of the disease is limited. In the present study, we investigated the effect of the antioxidant Vitamin E on the AD-like phenotype when given to a transgenic mouse model (Tg2576) of the disease before or after the amyloid plaques are deposited. One group of Tg2576 received Vitamin E starting at 5 months of age until they were 13 months old, the second group started at 14 months of age until they were 20 months old. Brain levels of 8,12-iso-iPF2alpha-VI, a specific marker of lipid peroxidation, were significantly reduced in both groups of mice receiving Vitamin E compared with placebo. Tg2576 administered with Vitamin E at a younger age showed a significant reduction in Abeta levels and amyloid deposition. By contrast, mice receiving the diet supplemented with Vitamin E at a later age did not show any significant difference in either marker when compared with placebo. These results support the hypothesis that oxidative stress is an important early event in AD pathogenesis, and antioxidant therapy may be beneficial only if given at this stage of the disease process. PMID:14656990

  10. Cure Chemistry of Phenylethynyl Terminated Oligomers

    NASA Technical Reports Server (NTRS)

    Wood, Karen H.; Orwoll, Robert A.; Young, Philip R.; Jensen, Brian J.; McNair, Harold M.

    1997-01-01

    The ability to process high performance polymers into quality, void-free composites has been significantly advanced using oligomers terminated with reactive groups which cure or crosslink at elevated temperature without the evolution of volatile byproducts. Several matrix resin systems of considerable interest to the aerospace community utilize phenylethynyl-terminated imide (PETI) technology to achieve this advantage. The present paper addresses the cure chemistry of PETI oligomers. The thermal cure of a low molecular weight model compound was studied using a variety of analytical techniques including differential scanning calorimetry, Fourier transform infrared spectroscopy, and liquid chromatography-mass spectroscopy. The studies indicate an extremely complex cure process. Many stable products were isolated and this paper reports current work on identification of those products. The intent of this research is to provide fundamental insight into the molecular structure of the cured PETI engineering materials so that performance and durability can be more fully assessed.

  11. Oligomer functionalized nanotubes and composites formed therewith

    DOEpatents

    Zettl, Alexander K; Sainsbury, Toby; Frechet, Jean M.J.

    2014-03-18

    Disclosed herein is a sequential functionalization methodology for the covalent modification of nanotubes with between one and four repeat units of a polymer. Covalent attachment of oligomer units to the surface of nanotubes results in oligomer units forming an organic sheath around the nanotubes, polymer-functionalized-nanotubes (P-NTs). P-NTs possess chemical functionality identical to that of the functionalizing polymer, and thus provide nanoscale scaffolds which may be readily dispersed within a monomer solution and participate in the polymerization reaction to form a polymer-nanotube/polymer composite. Formation of polymer in the presence of P-NTs leads to a uniform dispersion of nanotubes within the polymer matrix, in contrast to aggregated masses of nanotubes in the case of pristine-NTs. The covalent attachment of oligomeric units to the surface of nanotubes represents the formation of a functional nanoscale building block which can be readily dispersed and integrated within the polymer to form a novel composite material.

  12. Hydrolysis of GTP associated with the formation of tubulin oligomers is involved in microtubule nucleation.

    PubMed Central

    Carlier, M F; Didry, D; Pantaloni, D

    1997-01-01

    Hydrolysis of GTP is known to accompany microtubule assembly. Here we show that hydrolysis of GTP is also associated with the formation of linear oligomers of tubulin, which are precursors (prenuclei) in microtubule assembly. The hydrolysis of GTP on these linear oligomers inhibits the lateral association of GTP-tubulin that leads to the formation of a bidimensional lattice. Therefore GTP hydrolysis interferes with the nucleation of microtubules. Linear oligomers are also formed in mixtures of GTP-tubulin and GDP-tubulin. The hydrolysis of GTP associated with heterologous interactions between GTP-tubulin and GDP-tubulin in the cooligomer takes place at a threefold faster rate than upon homologous interactions between GTP-tubulins. The implication of these results in a model of vectorial GTP hydrolysis in microtubule assembly is discussed. Images FIGURE 7 PMID:9199805

  13. Ethynyl terminated ester oligomers and polymers therefrom

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (Inventor); hesives and composite matrices. (Inventor)

    1987-01-01

    A new class of ethynyl-terminated oligomers and the process for preparing same are disclosed. Upon the application of heat, with or without a catalyst, the ethynyl groups react to provide crosslinking and chain extension to increase the polymer use temperature and improve the polymer solvent resistance. These improved polyesters are potentially useful in packaging, magnetic tapes, capacitors, industrial belting, protective coatings, structural adhesives and composite matrices.

  14. A Rat Model of Alzheimer’s Disease Based on Abeta42 and Pro-oxidative Substances Exhibits Cognitive Deficit and Alterations in Glutamatergic and Cholinergic Neurotransmitter Systems

    PubMed Central

    Petrasek, Tomas; Skurlova, Martina; Maleninska, Kristyna; Vojtechova, Iveta; Kristofikova, Zdena; Matuskova, Hana; Sirova, Jana; Vales, Karel; Ripova, Daniela; Stuchlik, Ales

    2016-01-01

    Alzheimer’s disease (AD) is one of the most serious human, medical, and socioeconomic burdens. Here we tested the hypothesis that a rat model of AD (Samaritan; Taconic Pharmaceuticals, USA) based on the application of amyloid beta42 (Abeta42) and the pro-oxidative substances ferrous sulfate heptahydrate and L-buthionine-(S, R)-sulfoximine, will exhibit cognitive deficits and disruption of the glutamatergic and cholinergic systems in the brain. Behavioral methods included the Morris water maze (MWM; long-term memory version) and the active allothetic place avoidance (AAPA) task (acquisition and reversal), testing spatial memory and different aspects of hippocampal function. Neurochemical methods included testing of the NR1/NR2A/NR2B subunits of NMDA receptors in the frontal cortex and CHT1 transporters in the hippocampus, in both cases in the right and left hemisphere separately. Our results show that Samaritan rats™ exhibit marked impairment in both the MWM and active place avoidance tasks, suggesting a deficit of spatial learning and memory. Moreover, Samaritan rats exhibited significant changes in NR2A expression and CHT1 activity compared to controls rats, mimicking the situation in patients with early stage AD. Taken together, our results corroborate the hypothesis that Samaritan rats are a promising model of AD in its early stages. PMID:27148049

  15. Formation of domain-swapped oligomer of cytochrome C from its molten globule state oligomer.

    PubMed

    Deshpande, Megha Subhash; Parui, Partha Pratim; Kamikubo, Hironari; Yamanaka, Masaru; Nagao, Satoshi; Komori, Hirofumi; Kataoka, Mikio; Higuchi, Yoshiki; Hirota, Shun

    2014-07-22

    Many proteins, including cytochrome c (cyt c), have been shown to form domain-swapped oligomers, but the factors governing the oligomerization process remain unrevealed. We obtained oligomers of cyt c by refolding cyt c from its acid molten globule state to neutral pH state under high protein and ion concentrations. The amount of oligomeric cyt c obtained depended on the nature of the anion (chaotropic or kosmotropic) in the solution: ClO4(-) (oligomers, 11% ± 2% (heme unit)), SCN(-) (10% ± 2%), I(-) (6% ± 2%), NO3(-) (3% ± 1%), Br(-) (2% ± 1%), Cl(-) (2% ± 1%), and SO4(2-) (3% ± 1%) for refolding of 2 mM cyt c (anion concentration 125 mM). Dimeric cyt c obtained by refolding from the molten globule state exhibited a domain-swapped structure, in which the C-terminal α-helices were exchanged between protomers. According to small-angle X-ray scattering measurements, approximately 25% of the cyt c molecules were dimerized in the molten globule state containing 125 mM ClO4(-). These results indicate that a certain amount of molten globule state oligomers of cyt c convert to domain-swapped oligomers during refolding and that the intermolecular interactions necessary for domain swapping are present in the molten globule state. PMID:24981551

  16. Kinetics of ligation of fibrin oligomers.

    PubMed

    Nelb, G W; Kamykowski, G W; Ferry, J D

    1980-07-10

    Human fibrinogen was treated with thrombin in the presence of fibrinoligase and calcium ion at pH 8.5, ionic strength 0.45, and the ensuring polymerization was interrupted at various time intervals (t) both before and after the clotting time (tc) by solubilization with a solution of sodium dodecyl sulfate and urea. Aliquots of the solubilized protein were subjected to gel electrophoresis on polyacrylamide gels after disulfide reduction by dithiothreitol and on agarose gels without reduction. The degree of gamma-gamma ligation was determined from the former and the size distribution of ligated oligomers, for degree of polymerization x from 1 to 10, from the latter. The degree of gamma-gamma ligation was calculated independently from the size distribution with the assumption that every junction between two fibrin monomers remaining intact after solubilization is ligated, and this agreed well with the direct determination. The size distribution at t/tc = 1.3 to 1.6 differed somewhat from that calculated by the classical theory of linear polycondensation on the assumption that all reactive sites react with equal probability and rate. Analysis of the difference suggests that ligation of a fibrin digomer is not a random process; the probability of ligation of a given junction between two monomers increases with the oligomer length. The number-average degree of polymerization, xn, of ligated oligomers increases approximately linearly with time up to a value of 1.6. PMID:7391026

  17. Charge transfer interactions in oligomer coated gold nanoclusters

    NASA Astrophysics Data System (ADS)

    Newmai, M. Boazbou; Kumar, Pandian Senthil

    2016-05-01

    Gold nanoclusters were synthesized by a bottom-up synergistic approach of in-situ oligomerization of the monomer, N-vinyl pyrrolidone (NVP) and simultaneous weak reduction of Au-NVP complexes in the absence of any other external energy sources, thereby making these tiny gold clusters as the most elemental building blocks to construct further novel nano/microstructures with application potentials. It is well-known that metal clusters with less than 2 nm size do not show the usual surface plasmon band, because of the presence of a band-gap at the fermi level. Nevertheless, our present oligomer coated gold clusters show a discrete intense band at around 630 nm, which could very well be attributed to the charge transfer between the oligomer chain and the surface Au atoms. Such kind of sacrificial plasmon induced charge transfer interaction, observed for the very first time to the best of our knowledge, were also strongly corroborated through the enhancement / shifting of specific vibrational / rotational peaks as observed from the FTIR and Raman measurements as a function of the metal oxidation states, thus representing a new prototype for an efficient solar energy conversion probe.

  18. Structure of amyloid oligomers and their mechanisms of toxicities: Targeting amyloid oligomers using novel therapeutic approaches.

    PubMed

    Salahuddin, Parveen; Fatima, Munazza Tamkeen; Abdelhameed, Ali Saber; Nusrat, Saima; Khan, Rizwan Hasan

    2016-05-23

    Protein misfolding is one of the leading causes of amyloidoses. Protein misfolding occurs from changes in environmental conditions and host of other factors, including errors in post-translational modifications, increase in the rate of degradation, error in trafficking, loss of binding partners and oxidative damage. Misfolding gives rise to the formation of partially unfolded or misfolded intermediates, which have exposed hydrophobic residues and interact with complementary intermediates to form oligomers and consequently protofibrils and fibrils. The amyloid fibrils accumulate as amyloid deposits in the brain and central nervous system in Alzheimer's disease (AD), Prion disease and Parkinson's disease (PD). Initial studies have shown that amyloid fibrils were the main culprit behind toxicity that cause neurodegenerative diseases. However, attention shifted to the cytotoxicity of amyloid fibril precursors, notably amyloid oligomers, which are the major cause of toxicity. The mechanism of toxicity triggered by amyloid oligomers remains elusive. In this review, we have focused on the current knowledge of the structures of different aggregated states, including amyloid fibril, protofibrils, annular aggregates and oligomers. Based on the studies on the mechanism of toxicities, we hypothesize two major possible mechanisms of toxicities instigated by oligomers of Aβ (amyloid beta), PrP (prion protein) (106-126), and α-Syn (alpha-synuclein) including direct formation of ion channels and neuron membrane disruption by the increase in membrane conductance or leakage in the presence of small globulomers to large prefibrillar assemblies. Finally, we have discussed various novel innovative approaches that target amyloid oligomers in Alzheimer's diseases, Prion disease and Parkinson's disease. PMID:26974374

  19. Laccase-gum Arabic conjugate for preparation of water-soluble oligomer of catechin with enhanced antioxidant activity.

    PubMed

    Jadhav, Swati B; Singhal, Rekha S

    2014-05-01

    Catechin was oligomerized using free laccase and laccase-gum Arabic conjugate. The process of oligomerization was optimized with respect to solvent, ratio of solvent to buffer (0.2:10 to 1:10), pH of buffer (3-10), enzyme (575-18,400 U/mg) and substrate concentration (1-7mM). Maximum production of oligomer was observed in methanol at ratio 0.6:10 of methanol:buffer of pH 5 using 2300 U/mg of laccase and 5mM of catechin. The laccase-gum Arabic conjugate showed lower activity but higher stability than free laccase in methanol. Free laccase produced cross linked water-insoluble oligomer, whereas conjugated laccase produced linear water-soluble oligomer. The linear water-soluble oligomer showed higher antioxidant activity, as determined by the DPPH assay, and reducing power as compared to monomer making it suitable for biological applications. The molecular weight of the linear oligomer was found to be 13.14kDa, which suggested it to be composed of 45 monomer units. Further characterizations of linear and cross linked oligomer were done using FTIR and differential scanning calorimetry. PMID:24360412

  20. Structural studies on HCN oligomers. [catalysts for prebiotic processes

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Edelson, E. H.; Auyeung, J. M.; Joshi, P. C.

    1981-01-01

    NMR spectral studies on the HCN oligomers suggest the presence of carboxamide and urea groupings. The release of CO2, H2O, HCN, CH3CN, HCONH2 and pyridine on pyrolysis is consistent with the presence of these groupings as well as carboxylic acid groups. No basic primary amine groupings could be detected with fluorescamine. Hydrazinolysis of the HCN oligomers releases 10% of the amino acids normally released by acid hydrolysis. The oligomers give a positive biuret test but this is not due to the presence of peptide bonds. There is no conclusive evidence for the presence of peptide bonds in the HCN oligomers. No diglycine was detected on partial hydrolysis of the HCN oligomers at pH 8.5 suggesting that HCN oligomers were not a source of prebiotic peptides.

  1. A covalent homodimer probing early oligomers along amyloid aggregation.

    PubMed

    Halabelian, Levon; Relini, Annalisa; Barbiroli, Alberto; Penco, Amanda; Bolognesi, Martino; Ricagno, Stefano

    2015-01-01

    Early oligomers are crucial in amyloid aggregation; however, due to their transient nature they are among the least structurally characterized species. We focused on the amyloidogenic protein beta2-microglobulin (β2m) whose early oligomers are still a matter of debate. An intermolecular interaction between D strands of facing β2m molecules was repeatedly observed, suggesting that such interface may be relevant for β2m dimerization. In this study, by mutating Ser33 to Cys, and assembling the disulphide-stabilized β2m homodimer (DimC33), such DD strand interface was locked. Although the isolated DimC33 display a stability similar to wt β2m under native conditions, it shows enhanced amyloid aggregation propensity. Three distinct crystal structures of DimC33 suggest that dimerization through the DD interface is instrumental for enhancing DimC33 aggregation propensity. Furthermore, the crystal structure of DimC33 in complex with the amyloid-specific dye Thioflavin-T pinpoints a second interface, which likely participates in the first steps of β2m aggregation. The present data provide new insight into β2m early steps of amyloid aggregation. PMID:26420657

  2. A covalent homodimer probing early oligomers along amyloid aggregation

    PubMed Central

    Halabelian, Levon; Relini, Annalisa; Barbiroli, Alberto; Penco, Amanda; Bolognesi, Martino; Ricagno, Stefano

    2015-01-01

    Early oligomers are crucial in amyloid aggregation; however, due to their transient nature they are among the least structurally characterized species. We focused on the amyloidogenic protein beta2-microglobulin (β2m) whose early oligomers are still a matter of debate. An intermolecular interaction between D strands of facing β2m molecules was repeatedly observed, suggesting that such interface may be relevant for β2m dimerization. In this study, by mutating Ser33 to Cys, and assembling the disulphide-stabilized β2m homodimer (DimC33), such DD strand interface was locked. Although the isolated DimC33 display a stability similar to wt β2m under native conditions, it shows enhanced amyloid aggregation propensity. Three distinct crystal structures of DimC33 suggest that dimerization through the DD interface is instrumental for enhancing DimC33 aggregation propensity. Furthermore, the crystal structure of DimC33 in complex with the amyloid-specific dye Thioflavin-T pinpoints a second interface, which likely participates in the first steps of β2m aggregation. The present data provide new insight into β2m early steps of amyloid aggregation. PMID:26420657

  3. DNA sequence similarity recognition by hybridization to short oligomers

    DOEpatents

    Milosavljevic, Aleksandar

    1999-01-01

    Methods are disclosed for the comparison of nucleic acid sequences. Data is generated by hybridizing sets of oligomers with target nucleic acids. The data thus generated is manipulated simultaneously with respect to both (i) matching between oligomers and (ii) matching between oligomers and putative reference sequences available in databases. Using data compression methods to manipulate this mutual information, sequences for the target can be constructed.

  4. Diverse mechanisms of antidiabetic effects of the different procyanidin oligomer types of two different cinnamon species on db/db mice.

    PubMed

    Chen, Liang; Sun, Peng; Wang, Ting; Chen, Kaixian; Jia, Qi; Wang, Heyao; Li, Yiming

    2012-09-12

    The procyanidin oligomers are thought to be responsible for the antidiabetic activity of cinnamon. To investigate the hypoglycemic effects of different procyanidin oligomer types, the procyanidin oligomer-rich extracts were prepared from two different cinnamon species. Using high-performance liquid chromatography with purified procyanidin oligomers as reference compounds, we found that the Cinnamomum cassia extract (CC-E) and Cinnamomum tamala extract (CT-E) were rich in B- and A-type procyanidin oligomers, respectively. In the experiment, 8-week-old diabetic (db/db) mice were gavaged with CC-E and CT-E (both 200 mg/kg per day) for 4 weeks. Both CC-E and CT-E exhibited antidiabetic effects. Moreover, histopathological studies of the pancreas, liver, and adipose tissue showed that CC-E promoted lipid accumulation in the adipose tissue and liver, whereas CT-E mainly improved the insulin concentration in the blood and pancreas. PMID:22920511

  5. Polyetherurethane oligomers with aldehyde groups as additives for lubricating oils

    SciTech Connect

    Nikolaev, V.N.; Abramov, E.G.; Tenyushev, A.I.

    1995-01-01

    Polyetherurethane oligomers with aldehyde groups, which we synthesized from polyoxypropylene diols (molecular weight 500, 1000, 1500, 2000, or 3000) with toluene diisocyanate and salicylaldehyde, are of interest as additives for lubricating oils. The effects of these oligomers on the service properties and physicochemical characteristics of lubricating oils were investigated by methods prreviously described. As the lube base stocks we used castor oil, a polyoxypropylene diol and a polyethoxysiloxane. The oligomers are readily soluble in organic solvents and in the lube base stocks, and their solutions are stable during storage and use. We found that the optimal concentration of oligomers is 5%, providing the best lubricating properties, in particular the best antiwear properties.

  6. Aβ42-oligomer Interacting Peptide (AIP) neutralizes toxic amyloid-β42 species and protects synaptic structure and function

    NASA Astrophysics Data System (ADS)

    Barucker, Christian; Bittner, Heiko J.; Chang, Philip K.-Y.; Cameron, Scott; Hancock, Mark A.; Liebsch, Filip; Hossain, Shireen; Harmeier, Anja; Shaw, Hunter; Charron, François M.; Gensler, Manuel; Dembny, Paul; Zhuang, Wei; Schmitz, Dietmar; Rabe, Jürgen P.; Rao, Yong; Lurz, Rudi; Hildebrand, Peter W.; McKinney, R. Anne; Multhaup, Gerhard

    2015-10-01

    The amyloid-β42 (Aβ42) peptide is believed to be the main culprit in the pathogenesis of Alzheimer disease (AD), impairing synaptic function and initiating neuronal degeneration. Soluble Aβ42 oligomers are highly toxic and contribute to progressive neuronal dysfunction, loss of synaptic spine density, and affect long-term potentiation (LTP). We have characterized a short, L-amino acid Aβ-oligomer Interacting Peptide (AIP) that targets a relatively well-defined population of low-n Aβ42 oligomers, rather than simply inhibiting the aggregation of Aβ monomers into oligomers. Our data show that AIP diminishes the loss of Aβ42-induced synaptic spine density and rescues LTP in organotypic hippocampal slice cultures. Notably, the AIP enantiomer (comprised of D-amino acids) attenuated the rough-eye phenotype in a transgenic Aβ42 fly model and significantly improved the function of photoreceptors of these flies in electroretinography tests. Overall, our results indicate that specifically “trapping” low-n oligomers provides a novel strategy for toxic Aβ42-oligomer recognition and removal.

  7. Aβ42-oligomer Interacting Peptide (AIP) neutralizes toxic amyloid-β42 species and protects synaptic structure and function

    PubMed Central

    Barucker, Christian; Bittner, Heiko J.; Chang, Philip K.-Y.; Cameron, Scott; Hancock, Mark A.; Liebsch, Filip; Hossain, Shireen; Harmeier, Anja; Shaw, Hunter; Charron, François M.; Gensler, Manuel; Dembny, Paul; Zhuang, Wei; Schmitz, Dietmar; Rabe, Jürgen P.; Rao, Yong; Lurz, Rudi; Hildebrand, Peter W.; McKinney, R. Anne; Multhaup, Gerhard

    2015-01-01

    The amyloid-β42 (Aβ42) peptide is believed to be the main culprit in the pathogenesis of Alzheimer disease (AD), impairing synaptic function and initiating neuronal degeneration. Soluble Aβ42 oligomers are highly toxic and contribute to progressive neuronal dysfunction, loss of synaptic spine density, and affect long-term potentiation (LTP). We have characterized a short, L-amino acid Aβ-oligomer Interacting Peptide (AIP) that targets a relatively well-defined population of low-n Aβ42 oligomers, rather than simply inhibiting the aggregation of Aβ monomers into oligomers. Our data show that AIP diminishes the loss of Aβ42-induced synaptic spine density and rescues LTP in organotypic hippocampal slice cultures. Notably, the AIP enantiomer (comprised of D-amino acids) attenuated the rough-eye phenotype in a transgenic Aβ42 fly model and significantly improved the function of photoreceptors of these flies in electroretinography tests. Overall, our results indicate that specifically “trapping” low-n oligomers provides a novel strategy for toxic Aβ42-oligomer recognition and removal. PMID:26510576

  8. Aβ42-oligomer Interacting Peptide (AIP) neutralizes toxic amyloid-β42 species and protects synaptic structure and function.

    PubMed

    Barucker, Christian; Bittner, Heiko J; Chang, Philip K-Y; Cameron, Scott; Hancock, Mark A; Liebsch, Filip; Hossain, Shireen; Harmeier, Anja; Shaw, Hunter; Charron, François M; Gensler, Manuel; Dembny, Paul; Zhuang, Wei; Schmitz, Dietmar; Rabe, Jürgen P; Rao, Yong; Lurz, Rudi; Hildebrand, Peter W; McKinney, R Anne; Multhaup, Gerhard

    2015-01-01

    The amyloid-β42 (Aβ42) peptide is believed to be the main culprit in the pathogenesis of Alzheimer disease (AD), impairing synaptic function and initiating neuronal degeneration. Soluble Aβ42 oligomers are highly toxic and contribute to progressive neuronal dysfunction, loss of synaptic spine density, and affect long-term potentiation (LTP). We have characterized a short, L-amino acid Aβ-oligomer Interacting Peptide (AIP) that targets a relatively well-defined population of low-n Aβ42 oligomers, rather than simply inhibiting the aggregation of Aβ monomers into oligomers. Our data show that AIP diminishes the loss of Aβ42-induced synaptic spine density and rescues LTP in organotypic hippocampal slice cultures. Notably, the AIP enantiomer (comprised of D-amino acids) attenuated the rough-eye phenotype in a transgenic Aβ42 fly model and significantly improved the function of photoreceptors of these flies in electroretinography tests. Overall, our results indicate that specifically "trapping" low-n oligomers provides a novel strategy for toxic Aβ42-oligomer recognition and removal. PMID:26510576

  9. Mx oligomer: a novel capsid pattern sensor?

    PubMed

    Kong, Jia; Ma, Min; He, Shuangyi; Qin, Xiaohong

    2016-08-01

    Myxovirus resistance proteins represent a family of interferon-induced restriction factors of the innate and adaptive immune system. Human MxB acts as a novel restriction factor with antiviral activity against a range of HIV-1 and other retroviruses mainly by inhibiting the uncoating process after reverse transcription but prior to integration. Based on published data and conservation analysis, we propose a novel hypothesis, in which MxB dimers form higher order oligomers that restrict retroviral replication by binding to the viral capsid. Insights into the mechanistic basis of structural and functional characteristics of MxB will greatly advance our understanding of MxB. PMID:27492442

  10. Anharmonic Vibrational Dynamics of DNA Oligomers

    NASA Astrophysics Data System (ADS)

    Kühn, O.; Došlić, N.; Krishnan, G. M.; Fidder, H.; Heyne, K.

    Combining two-color infared pump-probe spectroscopy and anharmonic force field calculations we characterize the anharmonic coupling patterns between fingerprint modes and the hydrogen-bonded symmetric vNH2 stretching vibration in adenine-thymine dA20-dT20 DNA oligomers. Specifically, it is shown that the anharmonic coupling between the δNH2 bending and the vC4=O4 stretching vibration, both absorbing around 1665 cm-1, can be used to assign the vNH2 fundamental transition at 3215 cm-1 despite the broad background absorption of water.

  11. Aqueous-phase oligomerization of methyl vinyl ketone through photooxidation - Part 1: Aging processes of oligomers

    NASA Astrophysics Data System (ADS)

    Renard, P.; Siekmann, F.; Salque, G.; Demelas, C.; Coulomb, B.; Vassalo, L.; Ravier, S.; Temime-Roussel, B.; Voisin, D.; Monod, A.

    2015-01-01

    It has recently been established that unsaturated water-soluble organic compounds (UWSOCs) might efficiently form oligomers in polluted fogs and wet aerosol particles, even for weakly soluble ones like methyl vinyl ketone (MVK). The atmospheric relevance of these processes is explored by means of multiphase process model studies in a companion paper. In the present study, we investigate the aging of these aqueous-phase MVK oligomers formed via •OH oxidation, as well as their ability to form secondary organic aerosol (SOA) upon water evaporation. The comparison between aqueous-phase composition and aerosol composition after nebulization of the corresponding solutions shows similar trends for oligomer formation and aging. The measurements reveal that oligomer aging leads to the formation of organic diacids. Quantification of the SOA mass formed after nebulization is performed, and the obtained SOA mass yields seem to depend on the spectral irradiance of the light used to initiate the photochemistry. Investigating a large range of initial MVK concentrations (0.2-20 mM), the results show that their •OH oxidation undergoes competition between functionalization and oligomerization that is dependent on the precursor concentration. At high initial MVK concentrations (≥ 2 mM), oligomerization prevails over functionalization, while at lower initial concentrations, oligomerization is not the major process, and functionalization dominates, resulting in small carbonyls, dicarbonyls and monoacids. The atmospheric implications of these processes are discussed.

  12. Methyl-esterified 3-hydroxybutyrate oligomers protect bacteria from hydroxyl radicals.

    PubMed

    Koskimäki, Janne J; Kajula, Marena; Hokkanen, Juho; Ihantola, Emmi-Leena; Kim, Jong H; Hautajärvi, Heidi; Hankala, Elina; Suokas, Marko; Pohjanen, Johanna; Podolich, Olga; Kozyrovska, Natalia; Turpeinen, Ari; Pääkkönen, Mirva; Mattila, Sampo; Campbell, Bruce C; Pirttilä, Anna Maria

    2016-05-01

    Bacteria rely mainly on enzymes, glutathione and other low-molecular weight thiols to overcome oxidative stress. However, hydroxyl radicals are the most cytotoxic reactive oxygen species, and no known enzymatic system exists for their detoxification. We now show that methyl-esterified dimers and trimers of 3-hydroxybutyrate (ME-3HB), produced by bacteria capable of polyhydroxybutyrate biosynthesis, have 3-fold greater hydroxyl radical-scavenging activity than glutathione and 11-fold higher activity than vitamin C or the monomer 3-hydroxybutyric acid. We found that ME-3HB oligomers protect hypersensitive yeast deletion mutants lacking oxidative stress-response genes from hydroxyl radical stress. Our results show that phaC and phaZ, encoding polymerase and depolymerase, respectively, are activated and polyhydroxybutyrate reserves are degraded for production of ME-3HB oligomers in bacteria infecting plant cells and exposed to hydroxyl radical stress. We found that ME-3HB oligomer production is widespread, especially in bacteria adapted to stressful environments. We discuss how ME-3HB oligomers could provide opportunities for numerous applications in human health. PMID:26974813

  13. Cooperative Switching in Nanofibers of Azobenzene Oligomers.

    PubMed

    Weber, Christopher; Liebig, Tobias; Gensler, Manuel; Zykov, Anton; Pithan, Linus; Rabe, Jürgen P; Hecht, Stefan; Bléger, David; Kowarik, Stefan

    2016-01-01

    Next-generation molecular devices and machines demand the integration of molecular switches into hierarchical assemblies to amplify the response of the system from the molecular level to the meso- or macro-scale. Here, we demonstrate that multi-azobenzene oligomers can assemble to form robust supramolecular nanofibers in which they can be switched repeatedly between the E- and Z-configuration. While in isolated oligomers the azobenzene units undergo reversible photoisomerization independently, in the nanofibers they are coupled via intermolecular interactions and switch cooperatively as evidenced by unusual thermal and kinetic behavior. We find that the photoisomerization rate from the Z-isomer to the E-isomer depends on the fraction of Z-azobenzene in the nanofibers, and is increased by more than a factor of 4 in Z-rich fibers when compared to E-rich fibers. This demonstrates the great potential of coupling individual photochromic units for increasing their quantum efficiency in the solid state with potential relevance for actuation and sensing. PMID:27161608

  14. Liquid Crystal Ordering of Random DNA Oligomers

    NASA Astrophysics Data System (ADS)

    Bellini, Tommaso; Zanchetta, Giuliano; Fraccia, Tommaso; Cerbino, Roberto; Tsai, Ethan; Moran, Mark; Smith, Gregory; Walba, David; Clark, Noel

    2012-02-01

    Concentrated solutions of DNA oligomers (6 to 20 base pairs) organize into chiral nematic (NEM) and columnar (COL) liquid crystal (LC) phases. When the oligomer duplexes are mixed with single strands, LC phase formation proceeds through macroscopic phase separation, as a consequence of the combination of various self-assembly processes including strand pairing, reversible linear aggregation, demixing and LC ordering. We extended our investigation to the case of LC ordering in oligonucleotides whose sequences are partially or entirely randomly chosen, and we observed LC phases even in entirely random 20mers, corresponding to a family of 4^20 10^12 different sequences. We have tracked the origin of this behaviour: random sequences pair into generally defected duplexes, a large fraction of them terminating with stretches of unpaired bases (overhangs); overhangs promote linear aggregation of duplexes, with a mean strength depending on the overhang length; LC formation is accompanied by a phase separation where the duplexes with longer overhangs aggregate to form COL LC domains that coexist with an isotropic fluid rich in duplexes whose structure cannot aggregate.

  15. Cooperative Switching in Nanofibers of Azobenzene Oligomers

    NASA Astrophysics Data System (ADS)

    Weber, Christopher; Liebig, Tobias; Gensler, Manuel; Zykov, Anton; Pithan, Linus; Rabe, Jürgen P.; Hecht, Stefan; Bléger, David; Kowarik, Stefan

    2016-05-01

    Next-generation molecular devices and machines demand the integration of molecular switches into hierarchical assemblies to amplify the response of the system from the molecular level to the meso- or macro-scale. Here, we demonstrate that multi-azobenzene oligomers can assemble to form robust supramolecular nanofibers in which they can be switched repeatedly between the E- and Z-configuration. While in isolated oligomers the azobenzene units undergo reversible photoisomerization independently, in the nanofibers they are coupled via intermolecular interactions and switch cooperatively as evidenced by unusual thermal and kinetic behavior. We find that the photoisomerization rate from the Z-isomer to the E-isomer depends on the fraction of Z-azobenzene in the nanofibers, and is increased by more than a factor of 4 in Z-rich fibers when compared to E-rich fibers. This demonstrates the great potential of coupling individual photochromic units for increasing their quantum efficiency in the solid state with potential relevance for actuation and sensing.

  16. SAXS fingerprints of aldehyde dehydrogenase oligomers.

    PubMed

    Tanner, John J

    2015-12-01

    Enzymes of the aldehyde dehydrogenase (ALDH) superfamily catalyze the nicotinamide adenine dinucleotide-dependent oxidation of aldehydes to carboxylic acids. ALDHs are important in detoxification of aldehydes, amino acid metabolism, embryogenesis and development, neurotransmission, oxidative stress, and cancer. Mutations in genes encoding ALDHs cause metabolic disorders, including alcohol flush reaction (ALDH2), Sjögren-Larsson syndrome (ALDH3A2), hyperprolinemia type II (ALDH4A1), γ-hydroxybutyric aciduria (ALDH5A1), methylmalonic aciduria (ALDH6A1), pyridoxine dependent epilepsy (ALDH7A1), and hyperammonemia (ALDH18A1). We previously reported crystal structures and small-angle X-ray scattering (SAXS) analyses of ALDHs exhibiting dimeric, tetrameric, and hexameric oligomeric states (Luo et al., Biochemistry 54 (2015) 5513-5522; Luo et al., J. Mol. Biol. 425 (2013) 3106-3120). Herein I provide the SAXS curves, radii of gyration, and distance distribution functions for the three types of ALDH oligomer. The SAXS curves and associated analysis provide diagnostic fingerprints that allow rapid identification of the type of ALDH oligomer that is present in solution. The data sets provided here serve as a benchmark for characterizing oligomerization of ALDHs. PMID:26693506

  17. Cooperative Switching in Nanofibers of Azobenzene Oligomers

    PubMed Central

    Weber, Christopher; Liebig, Tobias; Gensler, Manuel; Zykov, Anton; Pithan, Linus; Rabe, Jürgen P.; Hecht, Stefan; Bléger, David; Kowarik, Stefan

    2016-01-01

    Next-generation molecular devices and machines demand the integration of molecular switches into hierarchical assemblies to amplify the response of the system from the molecular level to the meso- or macro-scale. Here, we demonstrate that multi-azobenzene oligomers can assemble to form robust supramolecular nanofibers in which they can be switched repeatedly between the E- and Z-configuration. While in isolated oligomers the azobenzene units undergo reversible photoisomerization independently, in the nanofibers they are coupled via intermolecular interactions and switch cooperatively as evidenced by unusual thermal and kinetic behavior. We find that the photoisomerization rate from the Z-isomer to the E-isomer depends on the fraction of Z-azobenzene in the nanofibers, and is increased by more than a factor of 4 in Z-rich fibers when compared to E-rich fibers. This demonstrates the great potential of coupling individual photochromic units for increasing their quantum efficiency in the solid state with potential relevance for actuation and sensing. PMID:27161608

  18. Amyloid β peptide oligomers directly activate NMDA receptors.

    PubMed

    Texidó, Laura; Martín-Satué, Mireia; Alberdi, Elena; Solsona, Carles; Matute, Carlos

    2011-03-01

    Amyloid beta (Aβ) oligomers accumulate in the brain tissue of Alzheimer disease patients and are related to disease pathogenesis. The precise mechanisms by which Aβ oligomers cause neurotoxicity remain unknown. We recently reported that Aβ oligomers cause intracellular Ca(2+) overload and neuronal death that can be prevented by NMDA receptor antagonists. This study investigated whether Aβ oligomers directly activated NMDA receptors (NMDARs) using NR1/NR2A and NR1/NR2B receptors that were heterologously expressed in Xenopus laevis oocytes. Indeed, Aβ oligomers induced inward non-desensitizing currents that were blocked in the presence of the NMDA receptor antagonists memantine, APV, and MK-801. Intriguingly, the amplitude of the responses to Aβ oligomers was greater for NR1/NR2A heteromers than for NR1/NR2B heteromers expressed in oocytes. Consistent with these findings, we observed that the increase in the cytosolic concentration of Ca(2+) induced by Aβ oligomers in cortical neurons is prevented by AP5, a broad spectrum NMDA receptor antagonist, but slightly attenuated by ifenprodil which blocks receptors with the NR2B subunit. Together, these results indicate that Aβ oligomers directly activate NMDA receptors, particularly those with the NR2A subunit, and further suggest that drugs that attenuate the activity of such receptors may prevent Aβ damage to neurons in Alzheimeŕs disease. PMID:21349580

  19. Hybrid conjugated organic oligomers consisting of oligodiacetylene and thiophene units: synthesis and optical properties.

    PubMed

    Pilzak, Gregor S; van Gruijthuijsen, Kitty; van Doorn, Reindert H; van Lagen, Barend; Sudhölter, Ernst J R; Zuilhof, Han

    2009-09-14

    Novel and highly soluble hybrid conjugated organic oligomers consisting of oligodiacetylene and thiophene units have been synthesized in high purity through iterative and divergent approaches based on a sequence of Sonogashira reactions. The series of thiophene-containing oligodiacetylenes (ThODAs) and homocoupled ThODAs (HThODAs) show--both in solution and in the solid state--a strong optical absorption, which is progressively red shifted with increasing chain length. The linear correlation of the absorption maximum (lambda(A)(max)) with the inverse of conjugation length (CL = number of double and triple bonds) shows that the effective conjugation length of this system is extended up to at least CL = 20. Furthermore, absorption measurements of dropcast thin films display not only a bathochromic shift of the absorption maxima but also a higher wavelength absorption, which is attributed to increased pi-pi interactions. The wavelength of the maximum fluorescence emission (lambda(E)(max)) also increases with CL, and emission is maximal for oligomers with CL=7-12 (fluorescence quantum yield Phi(F) = approximately 0.2). Both longer and shorter oligomers display marginal emission. The calculated Stokes shifts of these planar materials are relatively large (0.4 eV) for all oligomers, and likely due to excitation to the S(2) state, thus suggesting that the presence of enyne moieties dominates the ordering of the lowest excited states. The fluorescence lifetimes (tau(F)) are short (tau(F,max) = <1 ns) and closely follow the tendency obtained for the fluorescence quantum yield. The anisotropy lifetimes show a near-linear increase with CL, in line with highly rigid oligomers. PMID:19637259

  20. High-resolution NMR characterization of low abundance oligomers of amyloid-β without purification

    PubMed Central

    Kotler, Samuel A.; Brender, Jeffrey R.; Vivekanandan, Subramanian; Suzuki, Yuta; Yamamoto, Kazutoshi; Monette, Martine; Krishnamoorthy, Janarthanan; Walsh, Patrick; Cauble, Meagan; Holl, Mark M. Banaszak; Marsh, E. Neil. G.; Ramamoorthy, Ayyalusamy

    2015-01-01

    Alzheimer’s disease is characterized by the misfolding and self-assembly of the amyloidogenic protein amyloid-β (Aβ). The aggregation of Aβ leads to diverse oligomeric states, each of which may be potential targets for intervention. Obtaining insight into Aβ oligomers at the atomic level has been a major challenge to most techniques. Here, we use magic angle spinning recoupling 1H-1H NMR experiments to overcome many of these limitations. Using 1H-1H dipolar couplings as a NMR spectral filter to remove both high and low molecular weight species, we provide atomic-level characterization of a non-fibrillar aggregation product of the Aβ1-40 peptide using non-frozen samples without isotopic labeling. Importantly, this spectral filter allows the detection of the specific oligomer signal without a separate purification procedure. In comparison to other solid-state NMR techniques, the experiment is extraordinarily selective and sensitive. A resolved 2D spectra could be acquired of a small population of oligomers (6 micrograms, 7% of the total) amongst a much larger population of monomers and fibers (93% of the total). By coupling real-time 1H-1H NMR experiments with other biophysical measurements, we show that a stable, primarily disordered Aβ1-40 oligomer 5–15 nm in diameter can form and coexist in parallel with the well-known cross-β-sheet fibrils. PMID:26138908

  1. Cytotoxic Helix-Rich Oligomer Formation by Melittin and Pancreatic Polypeptide

    PubMed Central

    Singh, Pradeep K.; Ghosh, Dhiman; Tewari, Debanjan; Mohite, Ganesh M.; Carvalho, Edmund; Jha, Narendra Nath; Jacob, Reeba S.; Sahay, Shruti; Banerjee, Rinti; Bera, Amal K.; Maji, Samir K.

    2015-01-01

    Conversion of amyloid fibrils by many peptides/proteins involves cytotoxic helix-rich oligomers. However, their toxicity and biophysical studies remain largely unknown due to their highly dynamic nature. To address this, we chose two helical peptides (melittin, Mel and pancreatic polypeptide, PP) and studied their aggregation and toxicity. Mel converted its random coil structure to oligomeric helical structure upon binding to heparin; however, PP remained as helix after oligomerization. Interestingly, similar to Parkinson’s associated α-synuclein (AS) oligomers, Mel and PP also showed tinctorial properties, higher hydrophobic surface exposure, cellular toxicity and membrane pore formation after oligomerization in the presence of heparin. We suggest that helix-rich oligomers with exposed hydrophobic surface are highly cytotoxic to cells irrespective of their disease association. Moreover as Mel and PP (in the presence of heparin) instantly self-assemble into stable helix-rich amyloidogenic oligomers; they could be represented as models for understanding the biophysical and cytotoxic properties of helix-rich intermediates in detail. PMID:25803428

  2. High-resolution NMR characterization of low abundance oligomers of amyloid-β without purification

    NASA Astrophysics Data System (ADS)

    Kotler, Samuel A.; Brender, Jeffrey R.; Vivekanandan, Subramanian; Suzuki, Yuta; Yamamoto, Kazutoshi; Monette, Martine; Krishnamoorthy, Janarthanan; Walsh, Patrick; Cauble, Meagan; Holl, Mark M. Banaszak; Marsh, E. Neil. G.; Ramamoorthy, Ayyalusamy

    2015-07-01

    Alzheimer’s disease is characterized by the misfolding and self-assembly of the amyloidogenic protein amyloid-β (Aβ). The aggregation of Aβ leads to diverse oligomeric states, each of which may be potential targets for intervention. Obtaining insight into Aβ oligomers at the atomic level has been a major challenge to most techniques. Here, we use magic angle spinning recoupling 1H-1H NMR experiments to overcome many of these limitations. Using 1H-1H dipolar couplings as a NMR spectral filter to remove both high and low molecular weight species, we provide atomic-level characterization of a non-fibrillar aggregation product of the Aβ1-40 peptide using non-frozen samples without isotopic labeling. Importantly, this spectral filter allows the detection of the specific oligomer signal without a separate purification procedure. In comparison to other solid-state NMR techniques, the experiment is extraordinarily selective and sensitive. A resolved 2D spectra could be acquired of a small population of oligomers (6 micrograms, 7% of the total) amongst a much larger population of monomers and fibers (93% of the total). By coupling real-time 1H-1H NMR experiments with other biophysical measurements, we show that a stable, primarily disordered Aβ1-40 oligomer 5-15 nm in diameter can form and coexist in parallel with the well-known cross-β-sheet fibrils.

  3. High-resolution NMR characterization of low abundance oligomers of amyloid-β without purification.

    PubMed

    Kotler, Samuel A; Brender, Jeffrey R; Vivekanandan, Subramanian; Suzuki, Yuta; Yamamoto, Kazutoshi; Monette, Martine; Krishnamoorthy, Janarthanan; Walsh, Patrick; Cauble, Meagan; Holl, Mark M Banaszak; Marsh, E Neil G; Ramamoorthy, Ayyalusamy

    2015-01-01

    Alzheimer's disease is characterized by the misfolding and self-assembly of the amyloidogenic protein amyloid-β (Aβ). The aggregation of Aβ leads to diverse oligomeric states, each of which may be potential targets for intervention. Obtaining insight into Aβ oligomers at the atomic level has been a major challenge to most techniques. Here, we use magic angle spinning recoupling (1)H-(1)H NMR experiments to overcome many of these limitations. Using (1)H-(1)H dipolar couplings as a NMR spectral filter to remove both high and low molecular weight species, we provide atomic-level characterization of a non-fibrillar aggregation product of the Aβ1-40 peptide using non-frozen samples without isotopic labeling. Importantly, this spectral filter allows the detection of the specific oligomer signal without a separate purification procedure. In comparison to other solid-state NMR techniques, the experiment is extraordinarily selective and sensitive. A resolved 2D spectra could be acquired of a small population of oligomers (6 micrograms, 7% of the total) amongst a much larger population of monomers and fibers (93% of the total). By coupling real-time (1)H-(1)H NMR experiments with other biophysical measurements, we show that a stable, primarily disordered Aβ1-40 oligomer 5-15 nm in diameter can form and coexist in parallel with the well-known cross-β-sheet fibrils. PMID:26138908

  4. Optimization of the All-D Peptide D3 for Aβ Oligomer Elimination

    PubMed Central

    Klein, Antonia Nicole; Ziehm, Tamar; Tusche, Markus; Buitenhuis, Johan; Bartnik, Dirk; Boeddrich, Annett; Wiglenda, Thomas; Wanker, Erich; Funke, Susanne Aileen; Brener, Oleksandr; Gremer, Lothar; Kutzsche, Janine; Willbold, Dieter

    2016-01-01

    The aggregation of amyloid-β (Aβ) is postulated to be the crucial event in Alzheimer’s disease (AD). In particular, small neurotoxic Aβ oligomers are considered to be responsible for the development and progression of AD. Therefore, elimination of thesis oligomers represents a potential causal therapy of AD. Starting from the well-characterized d-enantiomeric peptide D3, we identified D3 derivatives that bind monomeric Aβ. The underlying hypothesis is that ligands bind monomeric Aβ and stabilize these species within the various equilibria with Aβ assemblies, leading ultimately to the elimination of Aβ oligomers. One of the hereby identified d-peptides, DB3, and a head-to-tail tandem of DB3, DB3DB3, were studied in detail. Both peptides were found to: (i) inhibit the formation of Thioflavin T-positive fibrils; (ii) bind to Aβ monomers with micromolar affinities; (iii) eliminate Aβ oligomers; (iv) reduce Aβ-induced cytotoxicity; and (v) disassemble preformed Aβ aggregates. The beneficial effects of DB3 were improved by DB3DB3, which showed highly enhanced efficacy. Our approach yielded Aβ monomer-stabilizing ligands that can be investigated as a suitable therapeutic strategy against AD. PMID:27105346

  5. High-Capacity Conductive Nanocellulose Paper Sheets for Electrochemically Controlled Extraction of DNA Oligomers

    PubMed Central

    Razaq, Aamir; Nyström, Gustav; Strømme, Maria; Mihranyan, Albert; Nyholm, Leif

    2011-01-01

    Highly porous polypyrrole (PPy)-nanocellulose paper sheets have been evaluated as inexpensive and disposable electrochemically controlled three-dimensional solid phase extraction materials. The composites, which had a total anion exchange capacity of about 1.1 mol kg−1, were used for extraction and subsequent release of negatively charged fluorophore tagged DNA oligomers via galvanostatic oxidation and reduction of a 30–50 nm conformal PPy layer on the cellulose substrate. The ion exchange capacity, which was, at least, two orders of magnitude higher than those previously reached in electrochemically controlled extraction, originated from the high surface area (i.e. 80 m2 g−1) of the porous composites and the thin PPy layer which ensured excellent access to the ion exchange material. This enabled the extractions to be carried out faster and with better control of the PPy charge than with previously employed approaches. Experiments in equimolar mixtures of (dT)6, (dT)20, and (dT)40 DNA oligomers showed that all oligomers could be extracted, and that the smallest oligomer was preferentially released with an efficiency of up to 40% during the reduction of the PPy layer. These results indicate that the present material is very promising for the development of inexpensive and efficient electrochemically controlled ion-exchange membranes for batch-wise extraction of biomolecules. PMID:22195031

  6. The Volumetric Diversity of Misfolded Prion Protein Oligomers Revealed by Pressure Dissociation*

    PubMed Central

    Torrent, Joan; Lange, Reinhard; Rezaei, Human

    2015-01-01

    Protein oligomerization has been associated with a wide range of diseases. High pressure approaches offer a powerful tool for deciphering the underlying molecular mechanisms by revealing volume changes associated with the misfolding and assembly reactions. We applied high pressure to induce conformational changes in three distinct β-sheet-rich oligomers of the prion protein PrP, a protein characterized by a variety of infectious quaternary structures that can propagate stably and faithfully and cause diseases with specific phenotypic traits. We show that pressure induces dissociation of the oligomers and leads to a lower volume monomeric PrP state that refolds into the native conformation after pressure release. By measuring the different pressure and temperature sensitivity of the tested PrP oligomers, we demonstrate significantly different void volumes in their quaternary structure. In addition, by focusing on the kinetic and energetic behavior of the pressure-induced dissociation of one specific PrP oligomer, we reveal a large negative activation volume and an increase in both apparent activation enthalpy and entropy. This suggests a transition state ensemble that is less structured and significantly more hydrated than the oligomeric state. Finally, we found that site-specific fluorescent labeling allows monitoring of the transient population of a kinetic intermediate in the dissociation reaction. Our results indicate that defects in atomic packing may deserve consideration as a new factor that influences differences between PrP assemblies and that could be relevant also for explaining the origin of prion strains. PMID:26126829

  7. Atomic View of a Toxic Amyloid Small Oligomer

    SciTech Connect

    Laganowsky, Arthur; Liu, Cong; Sawaya, Michael R.; Whitelegge, Julian P.; Park, Jiyong; Zhao, Minglei; Pensalfini, Anna; Soriaga, Angela B.; Landau, Meytal; Teng, Poh K.; Cascio, Duilio; Glabe, Charles; Eisenberg, David

    2012-04-30

    Amyloid diseases, including Alzheimer's, Parkinson's, and the prion conditions, are each associated with a particular protein in fibrillar form. These amyloid fibrils were long suspected to be the disease agents, but evidence suggests that smaller, often transient and polymorphic oligomers are the toxic entities. Here, we identify a segment of the amyloid-forming protein {alpha}{beta} crystallin, which forms an oligomeric complex exhibiting properties of other amyloid oligomers: {beta}-sheet-rich structure, cytotoxicity, and recognition by an oligomer-specific antibody. The x-ray-derived atomic structure of the oligomer reveals a cylindrical barrel, formed from six antiparallel protein strands, that we term a cylindrin. The cylindrin structure is compatible with a sequence segment from the {beta}-amyloid protein of Alzheimer's disease. Cylindrins offer models for the hitherto elusive structures of amyloid oligomers.

  8. Vibronic line shapes of PTCDA oligomers in helium nanodroplets.

    PubMed

    Roden, Jan; Eisfeld, Alexander; Dvořák, Matthieu; Bünermann, Oliver; Stienkemeier, Frank

    2011-02-01

    Oligomers of the organic semiconductor 3,4,9,10-perylene-tetracarboxylic-dianhydride, C(24)H(8)O(6) (PTCDA) are studied by means of helium nanodroplet isolation spectroscopy. In contrast to the monomer absorption spectrum, which exhibits clearly separated, very sharp absorption lines, it is found that the oligomer spectrum consists of three main peaks having an apparent width orders of magnitude larger than the width of the monomer lines. Using a simple theoretical model for the oligomer, in which a Frenkel exciton couples to internal vibrational modes of the monomers, these experimental findings are nicely reproduced. The three peaks present in the oligomer spectrum can already be obtained taking only one effective vibrational mode of the PTCDA molecule into account. The inclusion of more vibrational modes leads to quasicontinuous spectra, resembling the broad oligomer spectra. PMID:21303160

  9. Mitigation of copper toxicity by DNA oligomers in green paramecia

    PubMed Central

    Takaichi, Hiroshi; Comparini, Diego; Iwase, Junichiro; Bouteau, François; Mancuso, Stefano; Kawano, Tomonori

    2015-01-01

    Impact of transition metals which catalyze the generation of reactive oxygen species (ROS), on activation of cell death signaling in plant cells have been documented to date. Similarly in green paramecia (Paramecium bursaria), an aquatic protozoan species harboring symbiotic green algae in the cytoplasm, toxicities of various metallic ions have been documented. We have recently examined the effects of double-stranded GC-rich DNA fragments with copper-binding nature and ROS removal catalytic activity as novel plant cell-protecting agents, using the suspension-cultured tobacco cells. Here, we show that above DNA oligomers protect the cells of green paramecia from copper-induced cell death, suggesting that the phenomenon firstly observed in tobacco cells is not limited only within higher plants but it could be universally observable in wider range of organisms. PMID:26418558

  10. Mitigation of copper toxicity by DNA oligomers in green paramecia.

    PubMed

    Takaichi, Hiroshi; Comparini, Diego; Iwase, Junichiro; Bouteau, François; Mancuso, Stefano; Kawano, Tomonori

    2015-01-01

    Impact of transition metals which catalyze the generation of reactive oxygen species (ROS), on activation of cell death signaling in plant cells have been documented to date. Similarly in green paramecia (Paramecium bursaria), an aquatic protozoan species harboring symbiotic green algae in the cytoplasm, toxicities of various metallic ions have been documented. We have recently examined the effects of double-stranded GC-rich DNA fragments with copper-binding nature and ROS removal catalytic activity as novel plant cell-protecting agents, using the suspension-cultured tobacco cells. Here, we show that above DNA oligomers protect the cells of green paramecia from copper-induced cell death, suggesting that the phenomenon firstly observed in tobacco cells is not limited only within higher plants but it could be universally observable in wider range of organisms. PMID:26418558

  11. First-principles simulations of thiophene oligomers

    NASA Astrophysics Data System (ADS)

    Scherlis, Damian; Marzari, Nicola

    2003-03-01

    Conducting polymers, extensively investigated for their use in electronic and nanotechnology applications, have recently gained prominence for their possible use as molecular actuators in mechanical and bioengineering devices. We have focused our efforts on thiophene-based compounds, a class of materials that can be designed for high stress generation and large linear displacement (actuation strain), ideally outperforming mammalian muscle. Key features for the development of these materials are the microscopic binding properties of thiophene and thiophene oligomers stacks, where applied electric fields lead to oxidation and enhanced pi-pi bonding. We have completed the structural studies of neutral and charged oligothiophene dimers, in the search for efficient dimerization mechanisms. A comparison between different density-functional and quantum-chemistry approaches is critically presented, as are solvation effects, described in this work with a combination of first-principles molecular dynamics and a QM/MM approach for the solvating medium.

  12. Transthyretin as both Sensor and Scavenger of Aβ Oligomers

    PubMed Central

    Yang, Dennis T.; Joshi, Gururaj; Cho, Patricia Y.; Johnson, Jeffrey A.; Murphy, Regina M.

    2013-01-01

    Transthyretin (TTR) is a homotetrameric transport protein, assembled from monomers that each contains two four-stranded β-sheets and a short α-helix and loop. In the tetramer, the ‘inner’ β-sheet forms a hydrophobic pocket while the helix and loop are solvent-exposed. Beta-amyloid (Aβ) aggregates bind to TTR, and the binding is significantly reduced in mutants L82A (on the loop) and L110A (on the inner β-sheet). Protection against Aβ toxicity was demonstrated for wild-type TTR but not L82A or L110A, providing a direct link between TTR-Aβ binding, and TTR-mediated cytoprotection. Protection is afforded at substoichiometric (1:100) TTR:Aβ molar ratios, and binding of Aβ to TTR is highest for partially aggregated materials and decreased for freshly-prepared or heavily aggregated Aβ, suggesting that TTR binds selectively to soluble toxic Aβ aggregates. A novel technique, nanoparticle tracking, is used to show that TTR arrests Aβ aggregation by both preventing formation of new aggregates and inhibiting growth of existing aggregates. TTR tetramers are normally quite stable; tetrameric structure is necessary for the protein’s transport functions, and mutations that decrease tetramer stability have been linked to TTR amyloid diseases. However, TTR monomers bind more Aβ than do tetramers, presumably because the hydrophobic ‘inner’ sheet is solvent-exposed upon tetramer disassembly. Wild-type and L110A tetramers, but not L82A, were destabilized when co-incubated with Aβ, suggesting that Aβ binding to L82 triggers tetramer dissociation. Taken together, these results suggest a novel mechanism of action for TTR: the EF helix/loop ‘senses’ the presence of soluble toxic Aβ oligomers, triggering destabilization of TTR tetramers and exposure of the hydrophobic inner sheet, which then ‘scavenges’ these toxic oligomers and prevents them from causing cell death PMID:23570378

  13. Effect of Oligomer Length on Photophysical Properties of Platinum Acetylide Donor-Acceptor-Donor Oligomers.

    PubMed

    Cekli, Seda; Winkel, Russell W; Schanze, Kirk S

    2016-07-21

    We report a systematic study that explores how the triplet excited state is influenced by conjugation length in a series of benzothiadiazole units containing donor-acceptor-donor (DAD)-type platinum acetylide oligomers and polymer. The singlet and triplet excited states for the series were characterized by an array of photophysical methods including steady-state luminescence spectroscopy and femtosecond-nanosecond transient absorption spectroscopy. In addition to the experimental work, a computational study using density functional theory was conducted to gain more information about the structure, composition, and energies of the frontier molecular orbitals. It is observed that both the singlet and triplet excited states are mainly localized on a single donor-acceptor-donor unit in the oligomers. Interestingly, it is discovered that the intersystem crossing efficiency increases dramatically in the longer oligomers. The effect is attributed to an enhanced contribution of the heavy metal platinum in the frontier orbitals (HOMO and LUMO), an effect that leads to enhanced spin-orbit coupling. PMID:27291712

  14. The nonconserved hydrophilic loop domain of presenilin (PS) is not required for PS endoproteolysis or enhanced abeta 42 production mediated by familial early onset Alzheimer's disease-linked PS variants.

    PubMed

    Saura, C A; Tomita, T; Soriano, S; Takahashi, M; Leem, J Y; Honda, T; Koo, E H; Iwatsubo, T; Thinakaran, G

    2000-06-01

    Presenilin 1 (PS1) and presenilin 2 (PS2) are polytopic membrane proteins that are mutated in the majority of early onset familial Alzheimer's disease (FAD) cases. Two lines of evidence establish a critical role for PS in the production of beta-amyloid peptides (Abeta). FAD-linked PS mutations elevate the levels of highly amyloidogenic Abeta ending at residue 42 (Abeta42), and cells with ablated PS1 alleles secrete low levels of Abeta. Several recent reports have shown that the hydrophilic loop (HL) domain, located between transmembrane domains 6 and 7, contains sites for phosphorylation, caspase cleavage, and sequences that bind several PS-interacting proteins. In the present report, we examined the metabolism of PS polypeptides lacking the HL domain and the influence of these molecules on Abeta production. We report that the deletion of the HL domain does not have a deleterious effect on the regulated endoproteolysis of PS, saturable accumulation of PS fragments, or the self-association of PS fragments. Abeta production was not significantly altered in cells expressing HL-deleted PS polypeptides compared with cells expressing full-length PS. Importantly, deletion of the HL domain did not affect FAD mutation-mediated elevation in the production of Abeta42. Furthermore, the deletion of the HL domain did not impair the role of PS1 or PS2 in facilitating Notch processing. Thus, our results argue against a biologically or pathologically relevant role for the HL domain phosphorylation and caspase cleavage and the association of PS HL domain-interacting proteins, in amyloid precursor protein metabolism and Abeta production or Notch cleavage. PMID:10748144

  15. A Versatile and Scalable Strategy to Discrete Oligomers.

    PubMed

    Lawrence, Jimmy; Lee, Sang-Ho; Abdilla, Allison; Nothling, Mitchell D; Ren, Jing M; Knight, Abigail S; Fleischmann, Carolin; Li, Youli; Abrams, Austin S; Schmidt, Bernhard V K J; Hawker, Michael C; Connal, Luke A; McGrath, Alaina J; Clark, Paul G; Gutekunst, Will R; Hawker, Craig J

    2016-05-18

    A versatile strategy is reported for the multigram synthesis of discrete oligomers from commercially available monomer families, e.g., acrylates, styrenics, and siloxanes. Central to this strategy is the identification of reproducible procedures for the separation of oligomer mixtures using automated flash chromatography systems with the effectiveness of this approach demonstrated through the multigram preparation of discrete oligomer libraries (Đ = 1.0). Synthetic availability, coupled with accurate structural control, allows these functional building blocks to be harnessed for both fundamental studies as well as targeted technological applications. PMID:27152711

  16. Investigation of intermolecular interactions between single walled nanotubes and conjugated oligomers using the dispersion-corrected DFT methods

    NASA Astrophysics Data System (ADS)

    Lagowski, Jolanta B.; Aljohani, Suad; Khan, M. Zahidul H.; Zhao, Yuming

    The area of carbon nanotubes (CNT)-polymer composites has been progressing rapidly in recent years. Pure CNT and CNT-polymer composites have many useful (industry related) properties: ranging from electronic electrical conductivity to superior strength. However the full potential of using CNTs as reinforcements (in say a polymer matrix) has been severely limited because of complications associated with the dispersion of CNTs. CNTs tend to entangle with each other forming materials that have properties that fall short of the expectations. The goal of this work is to identify the type of conjugated oligomers that are best suited for the dispersion of single walled CNT (SWCNT). For this purpose, various methods of dispersion corrected density functional theory (DFT-D/B97D, /WB97XD, /CAM-B3LYP) have been used to investigate the interaction between the SWCNT and the organic conjugated oligomers with different end groups (aldehyde (ALD) and dithiafulvenyl (DTF)). We investigate the effect of intermolecular interactions on the structure, polarity and energetics of the oligomers and SWCNT combinations. The comparison of results obtained using different DFT approximations is made. Our results show that DFT-endcapped oligomer interact more strongly with CNT than ALD-endcapped oligomer. The financial support from NSERC, SACBC and Memorial University and the computational resources from Compute Canada were received.

  17. Selective amyloid β oligomer assay based on abasic site-containing molecular beacon and enzyme-free amplification.

    PubMed

    Zhu, Linling; Zhang, Junying; Wang, Fengyang; Wang, Ya; Lu, Linlin; Feng, Chongchong; Xu, Zhiai; Zhang, Wen

    2016-04-15

    Amyloid-beta (Aβ) oligomers are highly toxic species in the process of Aβ aggregation and are regarded as potent therapeutic targets and diagnostic markers for Alzheimer's disease (AD). Herein, a label-free molecular beacon (MB) system integrated with enzyme-free amplification strategy was developed for simple and highly selective assay of Aβ oligomers. The MB system was constructed with abasic site (AP site)-containing stem-loop DNA and a fluorescent ligand 2-amino-5,6,7-trimethyl-1,8-naphyridine (ATMND), of which the fluorescence was quenched upon binding to the AP site in DNA stem. Enzyme-free amplification was realized by target-triggered continuous opening of two delicately designed MBs (MB1 and MB2). Target DNA hybridization with MB1 and then MB2 resulted in the release of two ATMND molecules in one binding event. Subsequent target recycling could greatly amplify the detection sensitivity due to the greatly enhanced turn-on emission of ATMND fluorescence. Combining with Aβ oligomers aptamers, the strategy was applied to analyze Aβ oligomers and the results showed that it could quantify Aβ oligomers with high selectivity and monitor the Aβ aggregation process. This novel method may be conducive to improve the diagnosis and pathogenic study of Alzheimer's disease. PMID:26613510

  18. Esculin and its oligomer fractions inhibit adhesion and migration of U87 glioblastoma cells and in vitro angiogenesis.

    PubMed

    Mokdad-Bzeouich, Imen; Kovacic, Hervé; Ghedira, Kamel; Chebil, Latifa; Ghoul, Mohamed; Chekir-Ghedira, Leila; Luis, José

    2016-03-01

    Cancer metastasis is the major cause of cancer-related death. Chemoprevention is defined as the use of natural or synthetic substances to prevent cancer formation or cancer progress. In the present study, we investigate the antitumor activity of esculin and its oligomer fractions in U87 glioblastoma cells. We showed that esculin and its oligomers reduced U87 cell growth in a dose dependent manner. They also inhibited cell adhesion to collagen IV and vitronectin by interfering with the function of their respective receptors α2β1 and αvβ5 integrins. Furthermore, the tested samples were able to reduce migration of U87 cells towards another extracellular matrix fibronectin. Moreover, esculin and its oligomer fractions inhibited in vitro angiogenesis of endothelial cells (HMEC-1). In summary, our data provide the first evidence that esculin and its oligomer fractions are able to reduce adhesion, migration of glioblastoma cells and in vitro angiogenesis. Esculin and its oligomers may thus exert multi-target functions against cancer cells. PMID:26459313

  19. In vivo modification of Abeta plaque toxicity as a novel neuroprotective lithium-mediated therapy for Alzheimer’s disease pathology

    PubMed Central

    2013-01-01

    Background Alzheimer’s disease (AD) is characterized by the abnormal accumulation of extracellular beta-amyloid (Abeta) plaques, intracellular hyperphosphorylated tau, progressive synaptic alterations, axonal dystrophies, neuronal loss and the deterioration of cognitive capabilities of patients. However, no effective disease-modifying treatment has been yet developed. In this work we have evaluated whether chronic lithium treatment could ameliorate the neuropathology evolution of our well characterized PS1M146LxAPPSwe-London mice model. Results Though beneficial effects of lithium have been previously described in different AD models, here we report a novel in vivo action of this compound that efficiently ameliorated AD-like pathology progression and rescued memory impairments by reducing the toxicity of Abeta plaques. Transgenic PS1M146LxAPPSwe-London mice, treated before the pathology onset, developed smaller plaques characterized by higher Abeta compaction, reduced oligomeric-positive halo and therefore with attenuated capacity to induce neuronal damage. Importantly, neuronal loss in hippocampus and entorhinal cortex was fully prevented. Our data also demonstrated that the axonal dystrophic area associated with lithium-modified plaques was highly reduced. Moreover, a significant lower accumulation of phospho-tau, LC3-II and ubiquitinated proteins was detected in treated mice. Our study highlights that this switch of plaque quality by lithium could be mediated by astrocyte activation and the release of heat shock proteins, which concentrate in the core of the plaques. Conclusions Our data demonstrate that the pharmacological in vivo modulation of the extracellular Abeta plaque compaction/toxicity is indeed possible and, in addition, might constitute a novel promising and innovative approach to develop a disease-modifying therapeutic intervention against AD. PMID:24252759

  20. Effects of increased iron intake during the neonatal period on the brain of adult AbetaPP/PS1 transgenic mice.

    PubMed

    Fernandez, Liana Lisboa; Carmona, Marga; Portero-Otin, Manuel; Naudi, Alba; Pamplona, Reinald; Schröder, Nadja; Ferrer, Isidro

    2010-01-01

    The present study was aimed to investigate neuropathological changes in AbetaPP/PS1 transgenic mice (Tg), as a model of Alzheimer's disease, subjected to supplementary iron administration in a critical postnatal period, in order to reveal the interaction of genetic and environmental risk factors in the pathogenesis of the disease. Twelve Tg and 10 wild-type (Wt) littermates were administered iron between the 12th and 14th post-natal days (TgFe, WtFe); 11 Tg and 15 Wt received vehicle (sorbitol 5%) alone in the same period (TgSb, WtSb). Mice were killed at the age of six months and processed for morphological and biochemical studies. No modifications in amyloid-beta burden were seen in iron-treated and non-iron-treated AbetaPP/PS1 mice. No differences in microglial reactions were observed when comparing the four groups of mice. Yet increased astrocytosis, as revealed by densitometry of GFAP-immunoreactive astrocytes, and increased expression levels of GFAP, as revealed by gel electrophoresis and western blotting, were found in iron-treated mice (both Tg and Wt) when compared with TgSb and WtSb. This was accompanied by significant changes in brain fatty acid composition in AbetaPP/PS1 mice that led to a lower membrane peroxidizability index and to reduced protein oxidative damage, as revealed by reduced percentages of the oxidative stress markers: glutamic semialdehyde, aminoadipic semialdehyde, Nepsilon-carboxymethyl-lysine, Nepsilon-carboxyethyl-lysine, and Nepsilon-malondialdehyde-lysine. These findings demonstrate that transient dietary iron supplementation during the neonatal period is associated with cellular and metabolic imprinting in the brain in adult life, but it does not interfere with the appearance of amyloid plaques in AbetaPP/PS1 transgenic mice. PMID:20157260

  1. Toxic tau oligomer formation blocked by capping of cysteine residues with 1,2-dihydroxybenzene groups

    PubMed Central

    Soeda, Yoshiyuki; Yoshikawa, Misato; Almeida, Osborne F. X.; Sumioka, Akio; Maeda, Sumihiro; Osada, Hiroyuki; Kondoh, Yasumitsu; Saito, Akiko; Miyasaka, Tomohiro; Kimura, Tetsuya; Suzuki, Masaaki; Koyama, Hiroko; Yoshiike, Yuji; Sugimoto, Hachiro; Ihara, Yasuo; Takashima, Akihiko

    2015-01-01

    Neurofibrillary tangles, composed of hyperphosphorylated tau fibrils, are a pathological hallmark of Alzheimer's disease; the neurofibrillary tangle load correlates strongly with clinical progression of the disease. A growing body of evidence indicates that tau oligomer formation precedes the appearance of neurofibrillary tangles and contributes to neuronal loss. Here we show that tau oligomer formation can be inhibited by compounds whose chemical backbone includes 1,2-dihydroxybenzene. Specifically, we demonstrate that 1,2-dihydroxybenzene-containing compounds bind to and cap cysteine residues of tau and prevent its aggregation by hindering interactions between tau molecules. Further, we show that orally administered DL-isoproterenol, an adrenergic receptor agonist whose skeleton includes 1,2-dihydroxybenzene and which penetrates the brain, reduces the levels of detergent-insoluble tau, neuronal loss and reverses neurofibrillary tangle-associated brain dysfunction. Thus, compounds that target the cysteine residues of tau may prove useful in halting the progression of Alzheimer's disease and other tauopathies. PMID:26671725

  2. Synthesis and evaluation of novel bifunctional oligomer-based composites for dental applications.

    PubMed

    Xie, Dong; Chung, Il-Doo; Wang, Guigui; Mays, Jimmy

    2006-01-01

    Five novel bifunctional oligomers containing both carboxylic acid and methacrylate groups are synthesized, characterized, and used to formulate compomers by mixing with strontium fluoroaluminosilicate glass powder at a filler level of 75% (by weight). Compressive strength (CS) of the cements and viscosity of the resin liquids are used as screening tools to find the optimal formulation. Diametral tensile (DTS) and flexural strengths (FS) are also determined. Results show that the oligomers derivatized with glycerol dimethacrylate exhibit higher CS than those with 2-hydroxyethyl methacrylate. The CS increases with increasing diluent content, filler level, and light-exposure time. During aging, the cement shows an increase of strength over 24 h and then remains unaltered for up to 3 months. The experimental compomer is 45 and 69% higher in CS, 35 and 174% higher in DTS, and 39 and 170% higher in FS, respectively, as compared to Dyract and Fuji II LC. PMID:16364963

  3. Toxic tau oligomer formation blocked by capping of cysteine residues with 1,2-dihydroxybenzene groups.

    PubMed

    Soeda, Yoshiyuki; Yoshikawa, Misato; Almeida, Osborne F X; Sumioka, Akio; Maeda, Sumihiro; Osada, Hiroyuki; Kondoh, Yasumitsu; Saito, Akiko; Miyasaka, Tomohiro; Kimura, Tetsuya; Suzuki, Masaaki; Koyama, Hiroko; Yoshiike, Yuji; Sugimoto, Hachiro; Ihara, Yasuo; Takashima, Akihiko

    2015-01-01

    Neurofibrillary tangles, composed of hyperphosphorylated tau fibrils, are a pathological hallmark of Alzheimer's disease; the neurofibrillary tangle load correlates strongly with clinical progression of the disease. A growing body of evidence indicates that tau oligomer formation precedes the appearance of neurofibrillary tangles and contributes to neuronal loss. Here we show that tau oligomer formation can be inhibited by compounds whose chemical backbone includes 1,2-dihydroxybenzene. Specifically, we demonstrate that 1,2-dihydroxybenzene-containing compounds bind to and cap cysteine residues of tau and prevent its aggregation by hindering interactions between tau molecules. Further, we show that orally administered DL-isoproterenol, an adrenergic receptor agonist whose skeleton includes 1,2-dihydroxybenzene and which penetrates the brain, reduces the levels of detergent-insoluble tau, neuronal loss and reverses neurofibrillary tangle-associated brain dysfunction. Thus, compounds that target the cysteine residues of tau may prove useful in halting the progression of Alzheimer's disease and other tauopathies. PMID:26671725

  4. Biomimetic peptoid oligomers as dual-action antifreeze agents.

    PubMed

    Huang, Mia L; Ehre, David; Jiang, Qi; Hu, Chunhua; Kirshenbaum, Kent; Ward, Michael D

    2012-12-01

    The ability of natural peptides and proteins to influence the formation of inorganic crystalline materials has prompted the design of synthetic compounds for the regulation of crystal growth, including the freezing of water and growth of ice crystals. Despite their versatility and ease of structural modification, peptidomimetic oligomers have not yet been explored extensively as crystallization modulators. This report describes a library of synthetic N-substituted glycine peptoid oligomers that possess "dual-action" antifreeze activity as exemplified by ice crystal growth inhibition concomitant with melting temperature reduction. We investigated the structural features responsible for these phenomena and observed that peptoid antifreeze activities depend both on oligomer backbone structure and side chain chemical composition. These studies reveal the capability of peptoids to act as ice crystallization regulators, enabling the discovery of a unique and diverse family of synthetic oligomers with potential as antifreeze agents in food production and biomedicine. PMID:23169638

  5. Exosomal cell-to-cell transmission of alpha synuclein oligomers

    PubMed Central

    2012-01-01

    Background Aggregation of alpha-synuclein (αsyn) and resulting cytotoxicity is a hallmark of sporadic and familial Parkinson’s disease (PD) as well as dementia with Lewy bodies, with recent evidence implicating oligomeric and pre-fibrillar forms of αsyn as the pathogenic species. Recent in vitro studies support the idea of transcellular spread of extracellular, secreted αsyn across membranes. The aim of this study is to characterize the transcellular spread of αsyn oligomers and determine their extracellular location. Results Using a novel protein fragment complementation assay where αsyn is fused to non-bioluminescent amino-or carboxy-terminus fragments of humanized Gaussia Luciferase we demonstrate here that αsyn oligomers can be found in at least two extracellular fractions: either associated with exosomes or free. Exosome-associated αsyn oligomers are more likely to be taken up by recipient cells and can induce more toxicity compared to free αsyn oligomers. Specifically, we determine that αsyn oligomers are present on both the outside as well as inside of exosomes. Notably, the pathway of secretion of αsyn oligomers is strongly influenced by autophagic activity. Conclusions Our data suggest that αsyn may be secreted via different secretory pathways. We hypothesize that exosome-mediated release of αsyn oligomers is a mechanism whereby cells clear toxic αsyn oligomers when autophagic mechanisms fail to be sufficient. Preventing the early events in αsyn exosomal release and uptake by inducing autophagy may be a novel approach to halt disease spreading in PD and other synucleinopathies. PMID:22920859

  6. DNA-Grafted Supramolecular Polymers: Helical Ribbon Structures Formed by Self-Assembly of Pyrene-DNA Chimeric Oligomers.

    PubMed

    Vyborna, Yuliia; Vybornyi, Mykhailo; Rudnev, Alexander V; Häner, Robert

    2015-06-26

    The controlled arraying of DNA strands on adaptive polymeric platforms remains a challenge. Here, the noncovalent synthesis of DNA-grafted supramolecular polymers from short chimeric oligomers is presented. The oligomers are composed of an oligopyrenotide strand attached to the 5'-end of an oligodeoxynucleotide. The supramolecular polymerization of these oligomers in an aqueous medium leads to the formation of one-dimensional (1D) helical ribbon structures. Atomic force and transmission electron microscopy show rod-like polymers of several hundred nanometers in length. DNA-grafted polymers of the type described herein will serve as models for the development of structurally and functionally diverse supramolecular platforms with applications in materials science and diagnostics. PMID:25960306

  7. Purified high-dose anthocyanoside oligomer administration improves nocturnal vision and clinical symptoms in myopia subjects.

    PubMed

    Lee, Jonghyun; Lee, Hyung K; Kim, Chan Y; Hong, Young J; Choe, Chul M; You, Tae W; Seong, Gong J

    2005-06-01

    The aim of the present study was to determine the effect of purified high-dose anthocyanoside oligomer administration on nocturnal visual function and clinical symptoms in low-to-moderate myopia subjects. The study was a randomized, double-blind, placebo-controlled trial and involved sixty subjects with asthenopia and refractive errors between -1.00 and -8.00 diopters in both eyes. Thirty subjects were administered a purified high-dose anthocyanoside oligomer (100 mg tablet comprising 85 % anthocyanoside oligomer), and thirty were given a placebo in tablet form twice daily for 4 weeks. Prior to the treatment, the placebo and anthocyanoside groups were similar in terms of age and contrast sensitivity. Before and after treatment, subjects completed a questionnaire to determine their clinical symptoms and were also assessed for nocturnal visual function using contrast sensitivity testing. Questionnaire data analysis showed that, following treatment, twenty-two (73.3 %) anthocyanoside subjects showed improved symptoms, whereas only one placebo subject showed an improvement (Fisher's exact test, P<0.0001). Contrast sensitivity levels according to each cycle per degree significantly improved in the anthocyanoside group and remained stable in the placebo group. The mean contrast sensitivity change in the anthocyanoside group was 2.41 (SD) 1.91, compared with -0.66 (SD) 2.66 dB for the placebo group (unpaired Student's t test, P<0.0001). At all cycle per degree levels, contrast sensitivity changes in the anthocyanoside group were better than in the placebo group (unpaired Student's t test, P<0.05). The present data show that the administration of anthocyanoside oligomer appears to improve subjective symptoms and objective contrast sensitivity in myopia subjects with asthenopia. PMID:16022759

  8. Detection of oligomers and fibrils of α-synuclein by AIEgen with strong fluorescence.

    PubMed

    Leung, Chris Wai Tung; Guo, Feng; Hong, Yuning; Zhao, Engui; Kwok, Ryan Tsz Kin; Leung, Nelson Lik Ching; Chen, Sijie; Vaikath, Nishant N; El-Agnaf, Omar Mukhtar; Tang, Youhong; Gai, Wei-Ping; Tang, Ben Zhong

    2015-02-01

    We report a fluorophore, TPE-TPP, with AIE characteristics which is utilized as a fluorescence probe to monitor the α-synuclein (α-Syn) fibrillation process. Compared with ThT, TPE-TPP shows a higher sensitivity in the detection of α-Syn oligomers as well as fibrils with a stronger fluorescence. The performance of TPE-TPP was evaluated using fluorescence, AFM, dot blot, and SEC. PMID:25526628

  9. Rifampicin is a candidate preventive medicine against amyloid-β and tau oligomers.

    PubMed

    Umeda, Tomohiro; Ono, Kenjiro; Sakai, Ayumi; Yamashita, Minato; Mizuguchi, Mineyuki; Klein, William L; Yamada, Masahito; Mori, Hiroshi; Tomiyama, Takami

    2016-05-01

    Amyloid-β, tau, and α-synuclein, or more specifically their soluble oligomers, are the aetiologic molecules in Alzheimer's disease, tauopathies, and α-synucleinopathies, respectively. These proteins have been shown to interact to accelerate each other's pathology. Clinical studies of amyloid-β-targeting therapies in Alzheimer's disease have revealed that the treatments after disease onset have little benefit on patient cognition. These findings prompted us to explore a preventive medicine which is orally available, has few adverse effects, and is effective at reducing neurotoxic oligomers with a broad spectrum. We initially tested five candidate compounds: rifampicin, curcumin, epigallocatechin-3-gallate, myricetin, and scyllo-inositol, in cells expressing amyloid precursor protein (APP) with the Osaka (E693Δ) mutation, which promotes amyloid-β oligomerization. Among these compounds, rifampicin, a well-known antibiotic, showed the strongest activities against the accumulation and toxicity (i.e. cytochrome c release from mitochondria) of intracellular amyloid-β oligomers. Under cell-free conditions, rifampicin inhibited oligomer formation of amyloid-β, tau, and α-synuclein, indicating its broad spectrum. The inhibitory effects of rifampicin against amyloid-β and tau oligomers were evaluated in APPOSK mice (amyloid-β oligomer model), Tg2576 mice (Alzheimer's disease model), and tau609 mice (tauopathy model). When orally administered to 17-month-old APPOSK mice at 0.5 and 1 mg/day for 1 month, rifampicin reduced the accumulation of amyloid-β oligomers as well as tau hyperphosphorylation, synapse loss, and microglial activation in a dose-dependent manner. In the Morris water maze, rifampicin at 1 mg/day improved memory of the mice to a level similar to that in non-transgenic littermates. Rifampicin also inhibited cytochrome c release from the mitochondria and caspase 3 activation in the hippocampus. In 13-month-old Tg2576 mice, oral rifampicin at 0.5 mg

  10. Accumulation of oligomer-prone α-synuclein exacerbates synaptic and neuronal degeneration in vivo

    PubMed Central

    Rockenstein, Edward; Nuber, Silke; Overk, Cassia R.; Ubhi, Kiren; Mante, Michael; Patrick, Christina; Adame, Anthony; Trejo-Morales, Margarita; Gerez, Juan; Picotti, Paola; Jensen, Poul H.; Campioni, Silvia; Riek, Roland; Winkler, Jürgen; Gage, Fred H.; Winner, Beate

    2014-01-01

    In Parkinson’s disease and dementia with Lewy bodies, α-synuclein aggregates to form oligomers and fibrils; however, the precise nature of the toxic α-synuclein species remains unclear. A number of synthetic α-synuclein mutations were recently created (E57K and E35K) that produce species of α-synuclein that preferentially form oligomers and increase α-synuclein-mediated toxicity. We have shown that acute lentiviral expression of α-synuclein E57K leads to the degeneration of dopaminergic neurons; however, the effects of chronic expression of oligomer-prone α-synuclein in synapses throughout the brain have not been investigated. Such a study could provide insight into the possible mechanism(s) through which accumulation of α-synuclein oligomers in the synapse leads to neurodegeneration. For this purpose, we compared the patterns of neurodegeneration and synaptic damage between a newly generated mThy-1 α-synuclein E57K transgenic mouse model that is prone to forming oligomers and the mThy-1 α-synuclein wild-type mouse model (Line 61), which accumulates various forms of α-synuclein. Three lines of α-synuclein E57K (Lines 9, 16 and 54) were generated and compared with the wild-type. The α-synuclein E57K Lines 9 and 16 were higher expressings of α-synuclein, similar to α-synuclein wild-type Line 61, and Line 54 was a low expressing of α-synuclein compared to Line 61. By immunoblot analysis, the higher-expressing α-synuclein E57K transgenic mice showed abundant oligomeric, but not fibrillar, α-synuclein whereas lower-expressing mice accumulated monomeric α-synuclein. Monomers, oligomers, and fibrils were present in α-synuclein wild-type Line 61. Immunohistochemical and ultrastructural analyses demonstrated that α-synuclein accumulated in the synapses but not in the neuronal cells bodies, which was different from the α-synuclein wild-type Line 61, which accumulates α-synuclein in the soma. Compared to non-transgenic and lower-expressing mice, the

  11. Accumulation of oligomer-prone α-synuclein exacerbates synaptic and neuronal degeneration in vivo.

    PubMed

    Rockenstein, Edward; Nuber, Silke; Overk, Cassia R; Ubhi, Kiren; Mante, Michael; Patrick, Christina; Adame, Anthony; Trejo-Morales, Margarita; Gerez, Juan; Picotti, Paola; Jensen, Poul H; Campioni, Silvia; Riek, Roland; Winkler, Jürgen; Gage, Fred H; Winner, Beate; Masliah, Eliezer

    2014-05-01

    In Parkinson's disease and dementia with Lewy bodies, α-synuclein aggregates to form oligomers and fibrils; however, the precise nature of the toxic α-synuclein species remains unclear. A number of synthetic α-synuclein mutations were recently created (E57K and E35K) that produce species of α-synuclein that preferentially form oligomers and increase α-synuclein-mediated toxicity. We have shown that acute lentiviral expression of α-synuclein E57K leads to the degeneration of dopaminergic neurons; however, the effects of chronic expression of oligomer-prone α-synuclein in synapses throughout the brain have not been investigated. Such a study could provide insight into the possible mechanism(s) through which accumulation of α-synuclein oligomers in the synapse leads to neurodegeneration. For this purpose, we compared the patterns of neurodegeneration and synaptic damage between a newly generated mThy-1 α-synuclein E57K transgenic mouse model that is prone to forming oligomers and the mThy-1 α-synuclein wild-type mouse model (Line 61), which accumulates various forms of α-synuclein. Three lines of α-synuclein E57K (Lines 9, 16 and 54) were generated and compared with the wild-type. The α-synuclein E57K Lines 9 and 16 were higher expressings of α-synuclein, similar to α-synuclein wild-type Line 61, and Line 54 was a low expressing of α-synuclein compared to Line 61. By immunoblot analysis, the higher-expressing α-synuclein E57K transgenic mice showed abundant oligomeric, but not fibrillar, α-synuclein whereas lower-expressing mice accumulated monomeric α-synuclein. Monomers, oligomers, and fibrils were present in α-synuclein wild-type Line 61. Immunohistochemical and ultrastructural analyses demonstrated that α-synuclein accumulated in the synapses but not in the neuronal cells bodies, which was different from the α-synuclein wild-type Line 61, which accumulates α-synuclein in the soma. Compared to non-transgenic and lower-expressing mice, the

  12. Optimizing antisense oligonucleotides using phosphorodiamidate morpholino oligomers.

    PubMed

    Popplewell, Linda J; Malerba, Alberto; Dickson, George

    2012-01-01

    Duchenne muscular dystrophy (DMD) is caused by mutations that disrupt the reading frame of the human DMD gene. Selective removal of exons flanking an out-of-frame DMD mutation can result in an in-frame mRNA transcript that may be translated into an internally deleted Becker muscular dystrophy-like functionally active dystrophin protein with therapeutic activity. Antisense oligonucleotides (AOs) can be designed to bind to complementary sequences in the targeted mRNA and modify pre-mRNA splicing to correct the reading frame of a mutated transcript. AO-induced exon skipping resulting in functional truncated dystrophin has been demonstrated in animal models of DMD both in vitro and in vivo, in DMD patient cells in vitro in culture, and in DMD muscle explants. The recent advances made in this field suggest that it is likely that AO-induced exon skipping will be the first gene therapy for DMD to reach the clinic. However, it should be noted that personalized molecular medicine may be necessary, since the various reading frame-disrupting mutations are spread across the DMD gene. The different deletions that cause DMD would require skipping of different exons, which would require the optimization and clinical trial workup of many specific AOs. This chapter describes the methodologies available for the optimization of AOs, in particular phosphorodiamidate morpholino oligomers, for the targeted skipping of specific exons on the DMD gene. PMID:22454060

  13. Alpha-Synuclein Oligomers Interact with Metal Ions to Induce Oxidative Stress and Neuronal Death in Parkinson's Disease

    PubMed Central

    Deas, Emma; Cremades, Nunilo; Angelova, Plamena R.; Ludtmann, Marthe H.R.; Yao, Zhi; Chen, Serene; Horrocks, Mathew H.; Banushi, Blerida; Little, Daniel; Devine, Michael J.; Gissen, Paul; Klenerman, David; Dobson, Christopher M.; Wood, Nicholas W.

    2016-01-01

    Abstract Aims: Protein aggregation and oxidative stress are both key pathogenic processes in Parkinson's disease, although the mechanism by which misfolded proteins induce oxidative stress and neuronal death remains unknown. In this study, we describe how aggregation of alpha-synuclein (α-S) from its monomeric form to its soluble oligomeric state results in aberrant free radical production and neuronal toxicity. Results: We first demonstrate excessive free radical production in a human induced pluripotent stem-derived α-S triplication model at basal levels and on application of picomolar doses of β-sheet-rich α-S oligomers. We probed the effects of different structural species of α-S in wild-type rat neuronal cultures and show that both oligomeric and fibrillar forms of α-S are capable of generating free radical production, but that only the oligomeric form results in reduction of endogenous glutathione and subsequent neuronal toxicity. We dissected the mechanism of oligomer-induced free radical production and found that it was interestingly independent of several known cellular enzymatic sources. Innovation: The oligomer-induced reactive oxygen species (ROS) production was entirely dependent on the presence of free metal ions as addition of metal chelators was able to block oligomer-induced ROS production and prevent oligomer-induced neuronal death. Conclusion: Our findings further support the causative role of soluble amyloid oligomers in triggering neurodegeneration and shed light into the mechanisms by which these species cause neuronal damage, which, we show here, can be amenable to modulation through the use of metal chelation. Antioxid. Redox Signal. 24, 376–391. PMID:26564470

  14. Abeta targets of the biosimilar antibodies of Bapineuzumab, Crenezumab, Solanezumab in comparison to an antibody against N‑truncated Abeta in sporadic Alzheimer disease cases and mouse models.

    PubMed

    Bouter, Yvonne; Lopez Noguerola, Jose Socrates; Tucholla, Petra; Crespi, Gabriela A N; Parker, Michael W; Wiltfang, Jens; Miles, Luke A; Bayer, Thomas A

    2015-11-01

    Solanezumab and Crenezumab are two humanized antibodies targeting Amyloid-β (Aβ) which are currently tested in multiple clinical trials for the prevention of Alzheimer's disease. However, there is a scientific discussion ongoing about the target engagement of these antibodies. Here, we report the immunohistochemical staining profiles of biosimilar antibodies of Solanezumab, Crenezumab and Bapineuzumab in human formalin-fixed, paraffin-embedded tissue and human fresh frozen tissue. Furthermore, we performed a direct comparative immunohistochemistry analysis of the biosimilar versions of the humanized antibodies in different mouse models including 5XFAD, Tg4-42, TBA42, APP/PS1KI, 3xTg. The staining pattern with these humanized antibodies revealed a surprisingly similar profile. All three antibodies detected plaques, cerebral amyloid angiopathy and intraneuronal Aβ in a similar fashion. Remarkably, Solanezumab showed a strong binding affinity to plaques. We also reaffirmed that Bapineuzumab does not recognize N-truncated or modified Aβ, while Solanezumab and Crenezumab do detect N-terminally modified Aβ peptides Aβ4-42 and pyroglutamate Aβ3-42. In addition, we compared the results with the staining pattern of the mouse NT4X antibody that recognizes specifically Aβ4-42 and pyroglutamate Aβ3-42, but not full-length Aβ1-42. In contrast to the biosimilar antibodies of Solanezumab, Crenezumab and Bapineuzumab, the murine NT4X antibody shows a unique target engagement. NT4X does barely cross-react with amyloid plaques in human tissue. It does, however, detect cerebral amyloid angiopathy in human tissue. In Alzheimer mouse models, NT4X detects intraneuronal Aβ and plaques comparable to the humanized antibodies. In conclusion, the biosimilar antibodies Solanezumab, Crenezumab and Bapineuzumab strongly react with amyloid plaques, which are in contrast to the NT4X antibody that hardly recognizes plaques in human tissue. Therefore, NT4X is the first of a new class of

  15. Differential effects of co-chaperonin homologs on cpn60 oligomers

    PubMed Central

    Bonshtien, Anat L.; Parnas, Avital; Sharkia, Rajach; Niv, Adina; Mizrahi, Itzhak; Weiss, Celeste

    2009-01-01

    In this study, we have investigated the relationship between chaperonin/co-chaperonin binding, ATP hydrolysis, and protein refolding in heterologous chaperonin systems from bacteria, chloroplast, and mitochondria. We characterized two types of chloroplast cpn60 oligomers, ch-cpn60 composed of α and β subunits (α7β7 ch-cpn60) and one composed of all β subunits (β14 ch-cpn60). In terms of ATPase activity, the rate of ATP hydrolysis increased with protein concentration up to 60 μM, reflecting a concentration at which the oligomers are stable. At high concentrations of cpn60, all cpn10 homologs inhibited ATPase activity of α7β7 ch-cpn60. In contrast, ATPase of β14 ch-cpn60 was inhibited only by mitochondrial cpn10, supporting previous reports showing that β14 is functional only with mitochondrial cpn10 and not with other cpn10 homologs. Surprisingly, direct binding assays showed that both ch-cpn60 oligomer types bind to bacterial, mitochondrial, and chloroplast cpn10 homologs with an equal apparent affinity. Moreover, mitochondrial cpn60 binds chloroplast cpn20 with which it is not able to refold denatured proteins. Protein refolding experiments showed that in such instances, the bound protein is released in a conformation that is not able to refold. The presence of glycerol, or subsequent addition of mitochondrial cpn10, allows us to recover enzymatic activity of the substrate protein. Thus, in our systems, the formation of co-chaperonin/chaperonin complexes does not necessarily lead to protein folding. By using heterologous oligomer systems, we are able to separate the functions of binding and refolding in order to better understand the chaperonin mechanism. PMID:19224397

  16. Differential effects of co-chaperonin homologs on cpn60 oligomers.

    PubMed

    Bonshtien, Anat L; Parnas, Avital; Sharkia, Rajach; Niv, Adina; Mizrahi, Itzhak; Azem, Abdussalam; Weiss, Celeste

    2009-09-01

    In this study, we have investigated the relationship between chaperonin/co-chaperonin binding, ATP hydrolysis, and protein refolding in heterologous chaperonin systems from bacteria, chloroplast, and mitochondria. We characterized two types of chloroplast cpn60 oligomers, ch-cpn60 composed of alpha and beta subunits (alpha(7)beta(7) ch-cpn60) and one composed of all beta subunits (beta(14) ch-cpn60). In terms of ATPase activity, the rate of ATP hydrolysis increased with protein concentration up to 60 microM, reflecting a concentration at which the oligomers are stable. At high concentrations of cpn60, all cpn10 homologs inhibited ATPase activity of alpha(7)beta(7) ch-cpn60. In contrast, ATPase of beta(14) ch-cpn60 was inhibited only by mitochondrial cpn10, supporting previous reports showing that beta(14) is functional only with mitochondrial cpn10 and not with other cpn10 homologs. Surprisingly, direct binding assays showed that both ch-cpn60 oligomer types bind to bacterial, mitochondrial, and chloroplast cpn10 homologs with an equal apparent affinity. Moreover, mitochondrial cpn60 binds chloroplast cpn20 with which it is not able to refold denatured proteins. Protein refolding experiments showed that in such instances, the bound protein is released in a conformation that is not able to refold. The presence of glycerol, or subsequent addition of mitochondrial cpn10, allows us to recover enzymatic activity of the substrate protein. Thus, in our systems, the formation of co-chaperonin/chaperonin complexes does not necessarily lead to protein folding. By using heterologous oligomer systems, we are able to separate the functions of binding and refolding in order to better understand the chaperonin mechanism. PMID:19224397

  17. Rapamycin-induced oligomer formation system of FRB-FKBP fusion proteins.

    PubMed

    Inobe, Tomonao; Nukina, Nobuyuki

    2016-07-01

    Most proteins form larger protein complexes and perform multiple functions in the cell. Thus, artificial regulation of protein complex formation controls the cellular functions that involve protein complexes. Although several artificial dimerization systems have already been used for numerous applications in biomedical research, cellular protein complexes form not only simple dimers but also larger oligomers. In this study, we showed that fusion proteins comprising the induced heterodimer formation proteins FRB and FKBP formed various oligomers upon addition of rapamycin. By adjusting the configuration of fusion proteins, we succeeded in generating an inducible tetramer formation system. Proteins of interest also formed tetramers by fusing to the inducible tetramer formation system, which exhibits its utility in a broad range of biological applications. PMID:26777239

  18. Relaxation behavior of polymers through the study of oligomer model compounds

    NASA Astrophysics Data System (ADS)

    Ezquerra, T. A.

    2000-06-01

    The relaxation behavior of a series of ether-ketone oligomers was studied by means of dielectric spectroscopy. In order to isolate chain stiffness from other intermolecular factors, we studied chemically homogeneous, strictly monodisperse, low molecular weight ether-ketone model compounds. The dynamics of the α relaxation of ether-ketone model compounds as compared with that of the homologous polymer PEKK (50/50), shows up differences which can be attributed to the variation of inter and intra molecular correlations with the chain length. Model compounds exhibit a nearly similar degree of cooperativity regardless the differences in Tg values. The PEKK(50/50) polymer exhibits stronger cooperativity than the oligomers suggesting that in poly(ether-ketone-ketone)s molecular motions above Tg extend to more than one monomeric unit. .

  19. Soybean Ferritin Forms an Iron-Containing Oligomer in Tofu Even after Heat Treatment.

    PubMed

    Masuda, Taro

    2015-10-14

    Ferritin, a multimeric iron storage protein distributed in almost all living kingdoms, has been highlighted recently as a nutritional iron source in plant-derived foodstuffs, because ferritin iron is suggested to have high bioavailability. In soybean seeds, ferritin contributes largely to the net iron contents. Here, the oligomeric states and iron contents of soybean ferritin during food processing (especially tofu gel formation) were analyzed. Ferritin was purified from tofu gel as an iron-containing oligomer (approximately 1000 Fe atoms per oligomer), which was composed of two types of subunits similar to the native soybean seed ferritin. Circular dichroism spectra also showed no differences in α-helical structure between native soybean ferritin and tofu ferritin. The present data demonstrate that ferritin was stable during the heat treatment (boiling procedure) in food processing, although partial denaturation was observed at temperatures higher than 80 °C. PMID:26390371

  20. An N-terminal Fragment of the Prion Protein Binds to Amyloid-β Oligomers and Inhibits Their Neurotoxicity in Vivo*

    PubMed Central

    Fluharty, Brian R.; Biasini, Emiliano; Stravalaci, Matteo; Sclip, Alessandra; Diomede, Luisa; Balducci, Claudia; La Vitola, Pietro; Messa, Massimo; Colombo, Laura; Forloni, Gianluigi; Borsello, Tiziana; Gobbi, Marco; Harris, David A.

    2013-01-01

    A hallmark of Alzheimer disease (AD) is the accumulation of the amyloid-β (Aβ) peptide in the brain. Considerable evidence suggests that soluble Aβ oligomers are responsible for the synaptic dysfunction and cognitive deficit observed in AD. However, the mechanism by which these oligomers exert their neurotoxic effect remains unknown. Recently, it was reported that Aβ oligomers bind to the cellular prion protein with high affinity. Here, we show that N1, the main physiological cleavage fragment of the cellular prion protein, is necessary and sufficient for binding early oligomeric intermediates during Aβ polymerization into amyloid fibrils. The ability of N1 to bind Aβ oligomers is influenced by positively charged residues in two sites (positions 23–31 and 95–105) and is dependent on the length of the sequence between them. Importantly, we also show that N1 strongly suppresses Aβ oligomer toxicity in cultured murine hippocampal neurons, in a Caenorhabditis elegans-based assay, and in vivo in a mouse model of Aβ-induced memory dysfunction. These data suggest that N1, or small peptides derived from it, could be potent inhibitors of Aβ oligomer toxicity and represent an entirely new class of therapeutic agents for AD. PMID:23362282

  1. Self-assembly of phosphorous containing oligomers: morphological features and pH-sensitiveness in suspension.

    PubMed

    Travelet, Christophe; Bouilhac, Cécile; Robin, Jean-Jacques; Borsali, Redouane

    2014-10-14

    Methacrylamide-based oligomers bearing phosphonate pending groups at the end of a long alkyl chain and originating from undecylenic acid synthons were subjected to direct oligomer dissolution. Size improvement towards much smaller objects was reached using the nanoprecipitation method: the oligomers were first dissolved in an organic solvent, and then precipitated in water using a syringe pump. Dynamic light scattering (DLS) showed phosphorous containing monomodal and quite narrow-sized self-assemblies in water with hydrodynamic diameters (DH) ranging from 80 to 280 nm (depending on the oligomer system). Direct visualization using transmission electron microscopy (TEM) and atomic force microscopy (AFM) showed filled and almost individual particles with spherical shape. They were considerably shrunk, suggesting the highly swollen character of the self-assemblies in suspension. Morphological information on the multi-scale self-assembled structures was complementarily obtained using static light scattering (SLS). Thus, at a low length-scale, highly segregated sub-units having sharp boundaries surrounded by water (Porod behaviour) were observed, whereas at a high length-scale random non-compact organization of these sub-units via weak interactions was found, forming a chaplet-like structure (Gaussian behaviour). Furthermore, the pH-sensitiveness of the suspensions obtained after the nanoprecipitation method was studied. Particularly, at pH = 12, the characteristic size drastically increased within few hours from typically ∼280 nm to 2 μm due to electrostatic repulsion between deprotonated hydroxyl groups. At longer times, the observed peculiar behaviour corresponded to the model of diffusion-limited cluster aggregation (DLCA) where the particles stuck easily together upon contact [continuation of the article by C. Bouilhac, C. Travelet, A. Graillot, S. Monge, R. Borsali and J.-J. Robin, Polym. Chem., 2014, 5, 2756-2767]. PMID:25109365

  2. Induction of Covalently Crosslinked p62 Oligomers with Reduced Binding to Polyubiquitinated Proteins by the Autophagy Inhibitor Verteporfin

    PubMed Central

    Donohue, Elizabeth; Balgi, Aruna D.; Komatsu, Masaaki; Roberge, Michel

    2014-01-01

    Autophagy is a cellular catabolic process responsible for the degradation of cytoplasmic constituents, including organelles and long-lived proteins, that helps maintain cellular homeostasis and protect against various cellular stresses. Verteporfin is a benzoporphyrin derivative used clinically in photodynamic therapy to treat macular degeneration. Verteporfin was recently found to inhibit autophagosome formation by an unknown mechanism that does not require exposure to light. We report that verteporfin directly targets and modifies p62, a scaffold and adaptor protein that binds both polyubiquitinated proteins destined for degradation and LC3 on autophagosomal membranes. Western blotting experiments revealed that exposure of cells or purified p62 to verteporfin causes the formation of covalently crosslinked p62 oligomers by a mechanism involving low-level singlet oxygen production. Rose bengal, a singlet oxygen producer structurally unrelated to verteporfin, also produced crosslinked p62 oligomers and inhibited autophagosome formation. Co-immunoprecipitation experiments demonstrated that crosslinked p62 oligomers retain their ability to bind to LC3 but show defective binding to polyubiquitinated proteins. Mutations in the p62 PB1 domain that abolish self-oligomerization also abolished crosslinked oligomer formation. Interestingly, small amounts of crosslinked p62 oligomers were detected in untreated cells, and other groups noted the accumulation of p62 forms with reduced SDS-PAGE mobility in cellular and animal models of oxidative stress and aging. These data indicate that p62 is particularly susceptible to oxidative crosslinking and lead us to propose a model whereby oxidized crosslinked p62 oligomers generated rapidly by drugs like verteporfin or over time during the aging process interfere with autophagy. PMID:25494214

  3. Structural fingerprints and their evolution during oligomeric vs. oligomer-free amyloid fibril growth

    NASA Astrophysics Data System (ADS)

    Foley, Joseph; Hill, Shannon E.; Miti, Tatiana; Mulaj, Mentor; Ciesla, Marissa; Robeel, Rhonda; Persichilli, Christopher; Raynes, Rachel; Westerheide, Sandy; Muschol, Martin

    2013-09-01

    Deposits of fibrils formed by disease-specific proteins are the molecular hallmark of such diverse human disorders as Alzheimer's disease, type II diabetes, or rheumatoid arthritis. Amyloid fibril formation by structurally and functionally unrelated proteins exhibits many generic characteristics, most prominently the cross β-sheet structure of their mature fibrils. At the same time, amyloid formation tends to proceed along one of two separate assembly pathways yielding either stiff monomeric filaments or globular oligomers and curvilinear protofibrils. Given the focus on oligomers as major toxic species, the very existence of an oligomer-free assembly pathway is significant. Little is known, though, about the structure of the various intermediates emerging along different pathways and whether the pathways converge towards a common or distinct fibril structures. Using infrared spectroscopy we probed the structural evolution of intermediates and late-stage fibrils formed during in vitro lysozyme amyloid assembly along an oligomeric and oligomer-free pathway. Infrared spectroscopy confirmed that both pathways produced amyloid-specific β-sheet peaks, but at pathway-specific wavenumbers. We further found that the amyloid-specific dye thioflavin T responded to all intermediates along either pathway. The relative amplitudes of thioflavin T fluorescence responses displayed pathway-specific differences and could be utilized for monitoring the structural evolution of intermediates. Pathway-specific structural features obtained from infrared spectroscopy and Thioflavin T responses were identical for fibrils grown at highly acidic or at physiological pH values and showed no discernible effects of protein hydrolysis. Our results suggest that late-stage fibrils formed along either pathway are amyloidogenic in nature, but have distinguishable structural fingerprints. These pathway-specific fingerprints emerge during the earliest aggregation events and persist throughout the

  4. Structural fingerprints and their evolution during oligomeric vs. oligomer-free amyloid fibril growth

    PubMed Central

    Foley, Joseph; Hill, Shannon E.; Miti, Tatiana; Mulaj, Mentor; Ciesla, Marissa; Robeel, Rhonda; Persichilli, Christopher; Raynes, Rachel; Westerheide, Sandy; Muschol, Martin

    2013-01-01

    Deposits of fibrils formed by disease-specific proteins are the molecular hallmark of such diverse human disorders as Alzheimer's disease, type II diabetes, or rheumatoid arthritis. Amyloid fibril formation by structurally and functionally unrelated proteins exhibits many generic characteristics, most prominently the cross β-sheet structure of their mature fibrils. At the same time, amyloid formation tends to proceed along one of two separate assembly pathways yielding either stiff monomeric filaments or globular oligomers and curvilinear protofibrils. Given the focus on oligomers as major toxic species, the very existence of an oligomer-free assembly pathway is significant. Little is known, though, about the structure of the various intermediates emerging along different pathways and whether the pathways converge towards a common or distinct fibril structures. Using infrared spectroscopy we probed the structural evolution of intermediates and late-stage fibrils formed during in vitro lysozyme amyloid assembly along an oligomeric and oligomer-free pathway. Infrared spectroscopy confirmed that both pathways produced amyloid-specific β-sheet peaks, but at pathway-specific wavenumbers. We further found that the amyloid-specific dye thioflavin T responded to all intermediates along either pathway. The relative amplitudes of thioflavin T fluorescence responses displayed pathway-specific differences and could be utilized for monitoring the structural evolution of intermediates. Pathway-specific structural features obtained from infrared spectroscopy and Thioflavin T responses were identical for fibrils grown at highly acidic or at physiological pH values and showed no discernible effects of protein hydrolysis. Our results suggest that late-stage fibrils formed along either pathway are amyloidogenic in nature, but have distinguishable structural fingerprints. These pathway-specific fingerprints emerge during the earliest aggregation events and persist throughout the

  5. Luminescent Quadrupolar Borazine Oligomers: Synthesis, Photophysics, and Two-Photon Absorption Properties.

    PubMed

    Chen, Pangkuan; Marshall, Ariel S; Chi, San-Hui; Yin, Xiaodong; Perry, Joseph W; Jäkle, Frieder

    2015-12-01

    A set of monodisperse bent donor-acceptor-donor-type conjugated borazine oligomers, BnNn+1 (n=1-4), incorporating electron-rich triarylamine donor and electron-deficient triarylborane acceptor units has been prepared through an iterative synthetic approach that takes advantage of highly selective silicon-boron and tin-boron exchange reactions. The effect of chain elongation on the electrochemical, one- and two-photon properties and excited-state photodynamics has been investigated. Strong intramolecular charge transfer (ICT) from the arylamine donors to boryl-centered acceptor sites results in emissions with high quantum yields (Φfl >0.5) in the range of 400-500 nm. Solvatochromic effects lead to solvent shifts as large as ∼70 nm for the shortest member (n=1) and gradually decrease with chain elongation. The oligomers exhibit strong two-photon absorption (2PA) in the visible spectral region with 2PA cross sections as large as 1410 GM (n=4), and broadband excited-state absorption (ESA) attributed to long-lived singlet-singlet and radical cation/anion absorption. The excited-state dynamics also show sensitivity to the solvent environment. Electrochemical observations and DFT calculations (B3LYP/6-31G*) reveal spatially separated HOMO and LUMO levels resulting in highly fluorescent oligomers with strong ICT character. The BnNn+1 oligomers have been used to demonstrate the detection of cyanide anions with association constants of log K>7. PMID:26514664

  6. Enhanced in Vitro Mineralization and in Vivo Osteogenesis of Composite Scaffolds through Controlled Surface Grafting of L-Lactic Acid Oligomer on Nanohydroxyapatite.

    PubMed

    Wang, Zongliang; Xu, Yang; Wang, Yu; Ito, Yoshihiro; Zhang, Peibiao; Chen, Xuesi

    2016-03-14

    Nanocomposite of hydroxyapatite (HA) surface grafted with L-lactic acid oligomer (LAc oligomer) (op-HA) showed improved interface compatibility, mechanical property, and biocompatibility in our previous study. In this paper, composite scaffolds of op-HA with controlled grafting different amounts of LAc oligomer (1.1, 5.2, and 9.1 wt %) were fabricated and implanted to repair rabbit radius defects. The dispersion of op-HA nanoparticles was more uniform than n-HA in chloroform and nanocomposites scaffold. Calcium and phosphorus exposure, in vitro biomineralization ability, and cell proliferation were much higher in the op-HA1.1 wt %/PLGA scaffolds than the other groups. The osteodifferentiation and bone fusion in animal tests were significantly enhanced for op-HA5.2 wt %/PLGA scaffolds. The results indicated that the grafted LAc oligomer of 5.2 or 9.1 wt %, which formed a barrier layer on the HA surface, prevented the exposure of nucleation sites. The shielded nucleation sites of op-HA particles (5.2 wt %) might be easily exposed as the grafted LAc oligomer was decomposed easily by enzyme systems in vivo. Findings from this study have revealed that grafting 1.1 wt % amount of LAc oligomer on hydroxyapatite could improve in vitro mineralization, and 5.2 wt % could promote in vivo osteogenesis capacity of composite scaffolds. PMID:26821731

  7. Structure of beta-glucan oligomer from laminarin and its effect on human monocytes to inhibit the proliferation of U937 cells.

    PubMed

    Pang, Zhongcun; Otaka, Kodo; Maoka, Takashi; Hidaka, Kumi; Ishijima, Sumio; Oda, Masayuki; Ohnishi, Masatake

    2005-03-01

    We analyzed the human monocyte-stimulating ability of laminarin from Eisenia bicyclis, lichenan from Cetraria islandica, and their oligomers depolymerized with endo-1,3-beta-glucanase from Arthrobacter sp. The respective beta-glucan oligomers with different degrees of polymerization (DP) were fractionated from hydrolytic products of laminarin and lichenan using gel-filtration chromatography. The monocyte-conditioned medium pre-cultured in the presence of a fraction of beta-glucan oligomer (DP>/=8) from laminarin exhibited inhibitory activity against the proliferation of human myeloid leukemia U937 cells, while those pre-cultured with other beta-glucan oligomers and the original laminarin and lichenan showed little or no activity. NMR analysis indicated that the beta-glucan oligomer (DP>/=8) has an average DP value of 13, and its ratio of beta-1,3- to beta-1,6-linkages in glucopyranose units was estimated to be 1.3:1. These results indicate that the beta-1,3-glucan oligomer with a higher content of beta-1,6-linkage stimulates monocytes to inhibit the proliferation of U937 cells. PMID:15784984

  8. LptA Assembles into Rod-Like Oligomers Involving Disorder-to-Order Transitions

    NASA Astrophysics Data System (ADS)

    Santambrogio, Carlo; Sperandeo, Paola; Villa, Riccardo; Sobott, Frank; Polissi, Alessandra; Grandori, Rita

    2013-10-01

    LptA is a periplasmic protein involved in the transport of lipopolysaccharide (LPS) from the inner membrane (IM) to the outer membrane (OM) of Gram-negative bacteria. Growing evidence supports a model in which LptA assembles into oligomers, forming a physical bridge connecting IM and OM. This work investigates assembly and architecture of LptA oligomers. Circular dichroism and "native" electrospray-ionization ion-mobility mass spectrometry (ESI-IM-MS) are employed to test concentration dependence of LptA structural features and to analyze the morphology of higher-order aggregates. The results show that LptA progressively assembles into rod-like oligomers without fixed stoichiometry, and grows by an n + 1 mechanism up to at least the pentamer. The oligomerization process induces disorder-to-order transitions in the polypeptide chain. Comparison with crystallographic and computational data suggests that these conformational changes likely involve short disordered regions at the N- and C-termini of monomeric LptA. The protein response to thermal denaturation displays strong concentration dependence, indicating that oligomerization increases protein stability. LptA conformational stability can also be enhanced by in vitro LPS binding. The genesis of these fibrillar structures could be relevant for the correct transport of LPS across the bacterial periplasm.

  9. Panchromatic Light Capture and Efficient Excitation Transfer Leading to Near-IR Emission of BODIPY Oligomers.

    PubMed

    Sharma, Ritambhara; Gobeze, Habtom B; D'Souza, Francis; Ravikanth, Mangalampalli

    2016-08-18

    All-BODIPY-based (BODIPY=boron-dipyrromethene) donor-acceptor systems capable of wide-band absorbance leading to efficient energy transfer in the near-IR region are reported. A covalently linked 3-pyrrolyl BODIPY-BODIPY dimer building block bearing an ethynyl group at the meso-aryl position is synthesized and coupled with three different monomeric BODIPY/pyrrolyl BODIPY building blocks with a bromo/iodo group under Pd(0) coupling conditions to obtain three covalently linked 3-pyrrolyl-BODIPY-based donor-acceptor oligomers in 19-29 % yield. The oligomers are characterized in detail by 1D and 2D NMR spectroscopy, high-resolution mass spectrometry, and optical spectroscopy. Due to the presence of different functionalized BODIPY derivatives in the oligomers, panchromatic light capture (300-725 nm) is witnessed. Fluorescence studies reveal singlet-singlet energy transfer from BODIPY monomer to BODIPY dimer leading to emission in the 700-800 nm range. Theoretical modeling according to the Förster mechanism predicts ultrafast energy transfer due to good spectral overlap of the donor and acceptor entities. Femtosecond transient absorption studies confirm this to be the case and thus show the relevance of the currently developed all-BODIPY-based energy-funneling supramolecular sytems with near-IR emission to solar-energy harvesting applications. PMID:27168532

  10. "The Show"

    ERIC Educational Resources Information Center

    Gehring, John

    2004-01-01

    For the past 16 years, the blue-collar city of Huntington, West Virginia, has rolled out the red carpet to welcome young wrestlers and their families as old friends. They have come to town chasing the same dream for a spot in what many of them call "The Show". For three days, under the lights of an arena packed with 5,000 fans, the state's best…

  11. Degradation of a Sodium Acrylate Oligomer by an Arthrobacter sp

    PubMed Central

    Hayashi, Takaya; Mukouyama, Masaharu; Sakano, Kouichi; Tani, Yoshiki

    1993-01-01

    Arthrobacter sp. strain NO-18 was first isolated from soil as a bacterium which could degrade the sodium acrylate oligomer and utilize it as the sole source of carbon. When 0.2% (wt/wt) oligomer was added to the culture medium, the acrylate oligomer was found to be degraded by 70 to 80% in 2 weeks, using gel permeation chromatography. To determine the maximum molecular weight for biodegradation, the degradation test was done with the hexamer, heptamer, and octamer, which were separated from the oligomer mixture by fractional gel permeation chromatography. The hexamer and heptamer were consumed to the extents of 58 and 36%, respectively, in 2 weeks, but the octamer was not degraded. Oligomers with three different terminal groups were synthesized to examine the effect of the different terminal groups on biodegradation, but few differences were found. Arthrobacter sp. NO-18 assimilated acrylic acid, propionic acid, glutaric acid, 2-methylglutaric acid, and 1,3,5-pentanetricarboxylic acid. Degradation of the acrylic unit structure by this strain is discussed. PMID:8517751

  12. Imide Oligomers Endcapped with Phenylethynl Phthalic Anhydrides and Polymers Therefrom

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (Inventor); Smith, Joseph G., Jr. (Inventor)

    1998-01-01

    Controlled molecular weight phenylethynyl terminated imide oligomers (PETIs) have been prepared by the cyclodehydration of precursor phenylethynyl terminated amic acid oligomers. Amino terminated amic acid oligomers are prepared from the reaction of dianhydride(s) with an excess of diamine(s) and subsequently endcapped with phenylethynyl phthalic anhydride(s) (PEPA). The polymerizations are carried out in polar aprotic solvents such as N-methyl-2-pyrrolidinone or N.N-dimethylacetamide under nitrogen at room temperature. The amic acid oligomers are subsequently cyclodehydrated either thermally or cheznicauy to the corresponding imide oligomers. Direct preparation of PETIs from the reaction of dianhydxide(s) with an excess of diamine(s) and endcapped with phenylethynyl phthalic anhydride(s) has been performed in m-cresol. Phenylethynyl phthalic anhydrides are synthesized by the palladium catalyzed reaction of phenylacetylene with bromo substituted phthalic anhydrides in triethylamine. These new materials exhibit excellent properties and are potentially useful as adhesives, coatings, films, moldings and composite matrices.

  13. Observation of Fano resonances in all-dielectric nanoparticle oligomers.

    PubMed

    Chong, Katie E; Hopkins, Ben; Staude, Isabelle; Miroshnichenko, Andrey E; Dominguez, Jason; Decker, Manuel; Neshev, Dragomir N; Brener, Igal; Kivshar, Yuri S

    2014-05-28

    It is well-known that oligomers made of metallic nanoparticles are able to support sharp Fano resonances originating from the interference of two plasmonic resonant modes with different spectral width. While such plasmonic oligomers suffer from high dissipative losses, a new route for achieving Fano resonances in nanoparticle oligomers has opened up after the recent experimental observations of electric and magnetic resonances in low-loss dielectric nanoparticles. Here, light scattering by all-dielectric oligomers composed of silicon nanoparticles is studied experimentally for the first time. Pronounced Fano resonances are observed for a variety of lithographically-fabricated heptamer nanostructures consisting of a central particle of varying size, encircled by six nanoparticles of constant size. Based on a full collective mode analysis, the origin of the observed Fano resonances is revealed as a result of interference of the optically-induced magnetic dipole mode of the central particle with the collective mode of the nanoparticle structure. This allows for effective tuning of the Fano resonance to a desired spectral position by a controlled size variation of the central particle. Such optically-induced magnetic Fano resonances in all-dielectric oligomers offer new opportunities for sensing and nonlinear applications. PMID:24616191

  14. Imide oligomers endcapped with phenylethynyl phthalic anhydrides and polymers therefrom

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (Inventor); Smith, Jr., Joseph G. (Inventor)

    1996-01-01

    Controlled molecular weight phenylethynyl terminated imide oligomers (PETIs) have been prepared by the cyclodehydration of precursor phenylethynyl terminated amic acid oligomers. Amino terminated amic acid oligomers are prepared from the reaction of dianhydride(s) with an excess of diamine(s) and subsequently endcapped with phenylethynyl phthalic anhydride(s) (PEPA). The polymerizations are carried out in polar aprotic solvents such as N-methyl-2-pyrrolidinone or N,N-dimethylacetamide under nitrogen at room temperature. The amic acid oligomers are subsequently cyclodehydrated either thermally or chemically to the corresponding imide oligomers. Direct preparation of PETIs from the reaction of dianhydride(s) with an excess of diamine(s) and endcapped with phenylethynyl phthalic anhydride(s) has been performed in m-cresol. Phenylethynyl phthalic anhydrides are synthesized by the palladium catalyzed reaction of phenylacetylene with bromo substituted phthalic anhydrides in triethylamine. These new materials exhibit excellent properties and are potentially useful as adhesives, coatings, films, moldings and composite matrices.

  15. Deciphering aggregates, prefibrillar oligomers and protofibrils of cytochrome c.

    PubMed

    Amani, Samreen; Naeem, Aabgeena

    2014-08-01

    Aggregation of protein into insoluble intracellular complexes and inclusion bodies underlies the pathogenesis of human neurodegenerative diseases. Importance of cytochrome c (cyt c) arises from its involvement in apoptosis, sequence homology and for studying molecular evolution. A systemic investigation of polyethylene glycol (PEG) and trifluoroethanol (TFE) on the conformational stability of cyt c as a model hemeprotein was made using multi-methodological approach. Cyt c exists as molten globule (MG) at 60% PEG-400 and 40% TFE as confirmed by far-UV CD, attenuated total reflection Fourier transform infrared spectroscopy, Trp environment, 8-anilino-1-naphthalene-sulfonic acid (ANS) binding and blue shift in the soret band. Q-band splitting in MG states specifies conformational changes in the hydrophobic heme-binding pocket. Aggregates were detected at 90% PEG-400 and 50% TFE as confirmed by increase thioflavin T and ANS fluorescence and shift in Congo red absorbance. Detection of prefibrils and protofibrils at 90% PEG-400 and 50% TFE was possible after 72-h incubation. Single cell gel electrophoresis of prefibrils and protofibrils showed DNA damage confirming their toxicity and potential health hazards. Scanning electron microscopy and XRD analysis confirmed prefibrillar oligomers and protofibrils of cyt c. PMID:24729012

  16. Mapping eGFP Oligomer Mobility in Living Cell Nuclei

    PubMed Central

    Zwerger, Monika; Müller, Gabriele; Waldeck, Waldemar; Langowski, Jörg

    2009-01-01

    Movement of particles in cell nuclei can be affected by viscosity, directed flows, active transport, or the presence of obstacles such as the chromatin network. Here we investigate whether the mobility of small fluorescent proteins is affected by the chromatin density. Diffusion of inert fluorescent proteins was studied in living cell nuclei using fluorescence correlation spectroscopy (FCS) with a two-color confocal scanning detection system. We first present experiments exposing FCS-specific artifacts encountered in live cell studies as well as strategies to prevent them, in particular those arising from the choice of the fluorophore used for calibration of the focal volume, as well as temperature and acquisition conditions used for fluorescence fluctuation measurements. After defining the best acquisition conditions, we show for various human cell lines that the mobility of GFP varies significantly within the cell nucleus, but does not correlate with chromatin density. The intranuclear diffusional mobility strongly depends on protein size: in a series of GFP-oligomers, used as free inert fluorescent tracers, the diffusion coefficient decreased from the monomer to the tetramer much more than expected for molecules free in aqueous solution. Still, the entire intranuclear chromatin network is freely accessible for small proteins up to the size of eGFP-tetramers, regardless of the chromatin density or cell line. Even the densest chromatin regions do not exclude free eGFP-monomers or multimers. PMID:19347038

  17. Synthesis and Characterization of Poly (Arylene Ether Benzimidazole) Oligomers

    NASA Technical Reports Server (NTRS)

    Leonard, Michael J.

    1995-01-01

    Several poly(arylene ether benzimidazole) oligomers were prepared by the nucleophilic aromatic substitution reaction of a bisphenol benzimidazole and various alkyl-substituted aromatic bisphenols with an activated aromatic dihalide in N, N-dimethylacetarnide. Moderate to high molecular weight terpolymers were obtained in all cases, as shown by their inherent viscosities, which ranged from 0.50 to 0.87 dL g(sup -1). Glass transition temperatures (T(sub g)s) of polymer powders ranged from 267-280 C. Air-dried unoriented thin film T(sub g)s were markedly lower than those of the powders, whereas T(sub g)s of films dried in a nitrogen atmosphere were identical to those of the corresponding powders. In addition, air-dried films were dark amber and brittle, whereas nitrogen-dried films were yellow and creasable. Nitrogen-dried films showed slightly higher thin-film tensile properties than the air-dried films, as well.

  18. α-Synuclein Oligomers Impair Neuronal Microtubule-Kinesin Interplay*

    PubMed Central

    Prots, Iryna; Veber, Vanesa; Brey, Stefanie; Campioni, Silvia; Buder, Katrin; Riek, Roland; Böhm, Konrad J.; Winner, Beate

    2013-01-01

    Early α-synuclein (α-Syn)-induced alterations are neurite pathologies resulting in Lewy neurites. α-Syn oligomers are a toxic species in synucleinopathies and are suspected to cause neuritic pathology. To investigate how α-Syn oligomers may be linked to aberrant neurite pathology, we modeled different stages of α-Syn aggregation in vitro and investigated the interplay of α-Syn aggregates with proteins involved in axonal transport. The interaction of wild type α-Syn (WTS) and α-Syn variants (E57K, A30P, and aSyn(30–110)) with kinesin, tubulin, and the microtubule (MT)-associated proteins, MAP2 and Tau, is stronger for multimers than for monomers. WTS seeds but not α-Syn oligomers significantly and dose-dependently reduced Tau-promoted MT assembly in vitro. In contrast, MT gliding velocity across kinesin-coated surfaces was significantly decreased in the presence of α-Syn oligomers but not WTS seeds or fibrils (aSyn(30–110) multimers). In a human dopaminergic neuronal cell line, mild overexpression of the oligomerizing E57K α-Syn variant significantly impaired neurite network morphology without causing profound cell death. In accordance with these findings, MT stability, neuritic kinesin, and neuritic kinesin-dependent cargoes were significantly reduced by the presence of α-Syn oligomers. In summary, different α-Syn species act divergently on the axonal transport machinery. These findings provide new insights into α-Syn oligomer-driven neuritic pathology as one of the earliest events in synucleinopathies. PMID:23744071

  19. Tau oligomers as potential targets for early diagnosis of tauopathy.

    PubMed

    Sahara, Naruhiko; Ren, Yan; Ward, Sarah; Binder, Lester I; Suhara, Tetsuya; Higuchi, Makoto

    2014-01-01

    The discovery of tau mutations in frontotemporal dementia has been a key event in neurodegenerative disease research. The rTg4510 mouse line expressing human tau with P301L FTDP-17-tau mutation has been established to understand the role of tau in neurodegeneration. Our histological analyses with tau antibodies and fluorescent tau ligands on rTg4510 mice revealed that tau oligomer formation was distinct from tangle formation. While in vivo imaging of mature tangles is now available, imaging biomarkers for tau oligomers would be useful for clarifying their roles in neurotoxicity and for diagnosing early-stage tau pathology. PMID:24595194

  20. Oligomer-assisted synthesis of chiral polyaniline nanofibers.

    PubMed

    Li, Wenguang; Wang, Hsing-Lin

    2004-03-01

    We report here a novel approach to synthesize chiral PANI nanofibers in an aqueous solution. This new approach requires the following conditions: (1) Polymerization was carried out in concentrated camphor sulfonic acid solutions. (2) Aniline oligomers were used to accelerate the polymerization reaction. (3) Ammonium persulfate (oxidant) was added incrementally to the aniline solution. The high anisotropy factor of these PANI nanofibers is likely due to the "autocatalytic effect" resulting from lower oxidation potentials of aniline oligomers. Our chemical synthesis of the chiral PANI nanofibers is enantioselective and, under the optimized conditions, has an anisotropy factor (g = Deltaepsilon/epsilon) of 2.3 x 10-2. PMID:14982411

  1. Femtosecond spectroscopy of a thiophene oligomer with a photoswitch

    NASA Astrophysics Data System (ADS)

    Tamai, N.; Saika, T.

    1996-04-01

    Femtosecond transient absorption spectroscopy was applied to analyze the mechanism of optical switch of an endo-capped thiophene oligomer with a diarylethene structure as a new class of multimode chemical transducers. The rate of the optical switch of the proconductivity was estimated to be 1.1 ps, corresponding to the formation time of the closed-ring form of thiophene oligomer. From the direct observation of the precursor of closed-ring form, the mechanism of photochromic ring-closure reaction was discussed.

  2. Comprehensive analysis of fragment orbital interactions to build highly π-conjugated thienylene-substituted phenylene oligomers.

    PubMed

    Florès, Jean-Charles; Lacour, Marie-Agnès; Sallenave, Xavier; Serein-Spirau, Françoise; Lère-Porte, Jean-Pierre; Moreau, Joël J E; Miqueu, Karinne; Sotiropoulos, Jean-Marc; Flot, David

    2013-06-01

    π-Conjugated thienylene-phenylene oligomers with fluorinated and dialkoxylated phenylene fragments have been designed and prepared to understand the interactions in fragment orbitals, the influence of the substituents (F, OMe) on the HOMO-LUMO gap, and the role of intramolecular non-covalent cumulative interactions in the construction of π-conjugated nanostructures. Their strong conjugation was also evidenced in the gas phase by UV photoelectron spectroscopy and theoretical calculations. These results can be explained by the crucial role of the relative energetic positions of the π orbitals of the dimethoxyphenylene, which was used to model the dialkoxyphenylene entity, in determining the π/π(*) orbital levels of the fluorinated phenylene entity. Dialkoxyphenylenes raise the HOMO orbitals, whereas fluorinated phenylenes lower the LUMO orbitals in the oligomers. In addition, the presence of S⋅⋅⋅F and H⋅⋅⋅F interactions in the fluorinated phenylene-thienylene compounds add to the S⋅⋅⋅O interactions in the mixed targets and contribute to the full conjugation in the oligomer, inducing weak inter-ring angles between the involved aromatic cycles. These results, which showed extended conjugation of the π system, were corroborated by a narrow HOMO-LUMO gap (according to DFT calculations) and by a relatively strong maximum wavelength (as obtained by TD-DFT calculations and experimental UV/Vis measurements). The crystallographic data of two mixed thienylene-(fluorinated and dialkoxylated phenylene) five-ring oligomers agree with the above results and show the formation of quasi-planar conformations with non-covalent S⋅⋅⋅O, H⋅⋅⋅F, and S⋅⋅⋅F interactions. These studies in the solid and gas phases show the relevance of associating dialkoxyphenylene and fluorinated phenylene fragments with thiophene to lead to oligomers with improved electronic delocalization for electronic or optoelectronic devices. PMID:23576222

  3. Tailored covalent grafting of hexafluoropropylene oxide oligomers onto silica nanoparticles: toward thermally stable, hydrophobic, and oleophobic nanocomposites.

    PubMed

    Durand, Nelly; Mariot, David; Améduri, Bruno; Boutevin, Bernard; Ganachaud, François

    2011-04-01

    The modification of silica nanoparticles with hexafluoropropylene oxide (HFPO) oligomers has been investigated. HFPO oligomers with two different average degrees of polymerization (DPn = 8 and 15) were first prepared by anionic ring-opening polymerization, deactivated by methanol, and in some cases postfunctionalized by aminopropyl(tri)ethoxysilane or allylamine. The "grafting onto" reactions of these oligomers were then carried out either on bare silica (reaction between a silanol surface and ethoxy-silanized HFPO) or on silica functionalized by amino groups (in an amidation reaction with methyl ester-ended HFPO) or mercapto groups (via the radical addition of allyl-functionalized HFPO). Hybrid nanoparticles thus obtained were characterized by solid-state (29)Si NMR and FTIR spectroscopies as well as elemental and thermogravimetric analyses. The results assessed a significant yield of covalent grafting of HFPO oligomers when performing the hydrolysis-condensation of ethoxylated HFPO on the bare silica surface, compared to the other two methods that merely led to physically adsorbed HFPO chains. Chemically grafted nanohybrids showed a high thermal stability (up to 400 °C) as well as a very low surface tension (typically 5 mN/m) compared to physisorbed complexes. PMID:21391662

  4. Binding affinity of amyloid oligomers to cellular membranes is a generic indicator of cellular dysfunction in protein misfolding diseases.

    PubMed

    Evangelisti, Elisa; Cascella, Roberta; Becatti, Matteo; Marrazza, Giovanna; Dobson, Christopher M; Chiti, Fabrizio; Stefani, Massimo; Cecchi, Cristina

    2016-01-01

    The conversion of peptides or proteins from their soluble native states into intractable amyloid deposits is associated with a wide range of human disorders. Misfolded protein oligomers formed during the process of aggregation have been identified as the primary pathogenic agents in many such conditions. Here, we show the existence of a quantitative relationship between the degree of binding to neuronal cells of different types of oligomers formed from a model protein, HypF-N, and the GM1 content of the plasma membranes. In addition, remarkably similar behavior is observed for oligomers of the Aβ42 peptide associated with Alzheimer's disease. Further analysis has revealed the existence of a linear correlation between the level of the influx of Ca(2+) across neuronal membranes that triggers cellular damage, and the fraction of oligomeric species bound to the membrane. Our findings indicate that the susceptibility of neuronal cells to different types of misfolded oligomeric assemblies is directly related to the extent of binding of such oligomers to the cellular membrane. PMID:27619987

  5. Biophysical characterization data on Aβ soluble oligomers produced through a method enabling prolonged oligomer stability and biological buffer conditions

    PubMed Central

    Crisostomo, Amanda C.; Dang, Loan; Digambaranath, Jyothi L.; Klaver, Andrea C.; Loeffler, David A.; Payne, Jeremiah J.; Smith, Lynnae M.; Yokom, Adam L.; Finke, John M.

    2015-01-01

    The data here consists of time-dependent experimental parameters from chemical and biophysical methods used to characterize Aβ monomeric reactants as well as soluble oligomer and amyloid fibril products from a slow (3–4 week) assembly reaction under biologically-relevant solvent conditions. The data of this reaction are both of a qualitative and quantitative nature, including gel images from chemical cross-linking and Western blots, fractional solubility, thioflavin T binding, size exclusion chromatograms, transmission electron microscopy images, circular dichroism spectra, and fluorescence resonance energy transfer efficiencies of donor–acceptor pair labels in the Aβ chain. This data enables future efforts to produce the initial monomer and eventual soluble oligomer and amyloid fibril states by providing reference benchmarks of these states pertaining to physical properties (solubility), ligand-binding (thioflavin T binding), mesoscopic structure (electron microscopy, size exclusion chromatography, cross-linking products, SDS and native gels) and molecular structure (circular dichroism, FRET donor-acceptor distance). Aβ1-40 soluble oligomers are produced that are suitable for biophysical studies requiring sufficient transient stability to exist in their “native” conformation in biological phosphate-saline buffers for extended periods of time. The production involves an initial preparation of highly monomeric Aβ in a phosphate saline buffer that transitions to fibrils and oligomers through time incubation alone, without added detergents or non-aqueous chemicals. This criteria ensures that the only difference between initial monomeric Aβ reactant and subsequent Aβ oligomer products is their degree of peptide assembly. A number of chemical and biophysical methods were used to characterize the monomeric reactants and soluble oligomer and amyloid fibril products, including chemical cross-linking, Western blots, fraction solubility, thioflvain T binding

  6. The effect of polar end of long-chain fluorocarbon oligomers in promoting the superamphiphobic property over multi-scale rough Al alloy surfaces

    NASA Astrophysics Data System (ADS)

    Saifaldeen, Zubayda S.; Khedir, Khedir R.; Camci, Merve T.; Ucar, Ahmet; Suzer, Sefik; Karabacak, Tansel

    2016-08-01

    Rough structures with re-entrant property and their subsequent surface energy reduction with long-chain fluorocarbon oligomers are both critical in developing superamphiphobic (SAP, i.e. both super hydrophobic and superoleophobic) surfaces. However, morphology of the low-surface energy layer on a rough re-entrant substrate can strongly depend on the fluorocarbon oligomers used. In this study, the effect of polar end of different kinds of long-chain fluorocarbon oligomers in promoting a self-assembled monolayer with close packed molecules and robust adhesion on multi-scale rough Al alloy surfaces was investigated. Hierarchical Al alloy surfaces with microgrooves and nanograss structures were developed by a simple combination of one-directional mechanical sanding and post treatment in boiling de-ionized water (DIW). Three types of long-chain fluorocarbon oligomers of 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDTS), 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane (PFDCS), and perfluorooctanoic acid (PFOA) were chemically vaporized onto these rough Al alloy surfaces. The PFDCS exhibited the lowest surface free energy of less than 10 mN/m. The contact angle and sliding angle measurements for water, ethylene glycol, and peanut oil verified the SAP property of hierarchical rough Al alloy surfaces treated with alkylsilane oligomers (PFDTS, PFDCS). However, the hierarchical surfaces treated with fluorocarbon oligomer with polar acidic tail (PFOA) showed highly amphiphobic properties but could not reach the threshold for SAP. Chemical stability of the hierarchical Al alloy surfaces treated with the fluorocarbon oligomers was tested under the harsh conditions of ultra-sonication in acetone and annealing at high temperature after different treatment times. Contact angle measurements revealed the robustness of the alkylsilane oligomers and deterioration of the PFOA coating particularly for low surface tension liquids. The robust adhesion and close-packing of the alkylsilane

  7. Oligomer Molecules for Efficient Organic Photovoltaics.

    PubMed

    Lin, Yuze; Zhan, Xiaowei

    2016-02-16

    Solar cells, a renewable, clean energy technology that efficiently converts sunlight into electricity, are a promising long-term solution for energy and environmental problems caused by a mass of production and the use of fossil fuels. Solution-processed organic solar cells (OSCs) have attracted much attention in the past few years because of several advantages, including easy fabrication, low cost, lightweight, and flexibility. Now, OSCs exhibit power conversion efficiencies (PCEs) of over 10%. In the early stage of OSCs, vapor-deposited organic dye materials were first used in bilayer heterojunction devices in the 1980s, and then, solution-processed polymers were introduced in bulk heterojunction (BHJ) devices. Relative to polymers, vapor-deposited small molecules offer potential advantages, such as a defined molecular structure, definite molecular weight, easy purification, mass-scale production, and good batch-to-batch reproducibility. However, the limited solubility and high crystallinity of vapor-deposited small molecules are unfavorable for use in solution-processed BHJ OSCs. Conversely, polymers have good solution-processing and film-forming properties and are easily processed into flexible devices, whereas their polydispersity of molecular weights and difficulty in purification results in batch to batch variation, which may hamper performance reproducibility and commercialization. Oligomer molecules (OMs) are monodisperse big molecules with intermediate molecular weights (generally in the thousands), and their sizes are between those of small molecules (generally with molecular weights <1000) and polymers (generally with molecular weights >10000). OMs not only overcome shortcomings of both vapor-deposited small molecules and solution-processed polymers, but also combine their advantages, such as defined molecular structure, definite molecular weight, easy purification, mass-scale production, good batch-to-batch reproducibility, good solution processability

  8. [Antibody therapy for Alzheimer's disease].

    PubMed

    Tabira, Takeshi; Matsumoto, Shin-Ei; Jin, Haifeng

    2011-11-01

    In order to avoid Abeta-induced autoimmune encephalitis, several monoclonal and polyclonal antibodies are in clinical trials. These are bapineuzumab, solanezumab, ponezumab, gantenerumab, BAN2401, gammaguard and octagam. Since each antibody has a different antigen epitope of Abeta, anti-amyloid activities are different. It is unknown which antibody is effective for Alzheimer disease, and we must wait for the result of clinical trials. Some patients who developed tissue amyloid plaque immuno-reactive (TAPIR) antibody showed slower decline after AN-1792 vaccination. We developed TAPIR-like monoclonal antibody, which was found to react with Abeta oligomers preferentially. PMID:22277519

  9. Structure and topochemistry of azodioxide oligomers in solid state

    NASA Astrophysics Data System (ADS)

    Bibulić, Petar; Rončević, Igor; Varga, Katarina; Mihalić, Zlatko; Vančik, Hrvoj

    2016-01-01

    The structure of oligomers constructed from 1,4-dinitrosobenzene was studied computationally by DFT methods for shorter oligomers, and by the FMO approach for longer ones. It was demonstrated that the oligomers have helical structure. Formation of 1,4-dinitrosobenzene azodioxides from the corresponding nitroso monomers in solid state was examined by studying the kinetics of their oligomerization under cryogenic conditions. Dissociation of azodioxide bonds to nitroso groups was induced either by UV irradiation at cryogenic temperatures or by sublimation followed by cryogenic deposition. While warming the monomers prepared by UV photodissociation to 150 K gave E-polymers, oligomerization or polymerization of monomers prepared by cryogenic vapor deposition was less pronounced, giving Z-forms. Above 150 K, Z-dimers or short oligomers isomerized, probably by the dissociation-dimerization mechanism, to more stable E-forms. Fast formation of azodioxide bonds and the high stability of corresponding polymers can be ascribed to the strong topochemical effect in the solid state.

  10. Ferroelectric and dielectric properties of electroactive oligomers and nanocomposites

    NASA Astrophysics Data System (ADS)

    Kraemer, Kristin L.

    Polyvinylidene fluoride (PVDF) and its copolymers have been well established as ferroelectric polymers. The dielectric and ferroelectric properties for vinylidene fluoride (VDF) oligomer thin films were investigated. By synthesizing oligomers instead of long polymer chains, films with higher crystalinity can be formed and the locations of oligomers can be controlled for applications such as molecular electronics. Evidence of ferroelectricity was observed in oligomer thin films evaporated onto room temperature substrates and by Langmuir-Blodgett (LB) deposition. Voltage and frequency dependence of the capacitance was measured. Oligomers functionalized with phosphonic acid formed self-assembled monolayers (SAM) on aluminum and mica substrates. Film thickness was measured by ellipsometry and atomic force microscopy (AFM). The time dependence on film growth was measured for SAMs on mica substrates by AFM. The islands had already formed by 1 minute, and by 1 hour film was continuous. Additionally, studies were performed on composite dielectric systems with the goal of fabricating high energy density dielectrics containing nanoparticles with an organic shell. The first two types of samples had barium titante nanoparticles coated with functionalized alkanes or VDF oligomers. The first sample type consisted of coated nanoparticles embedded in a PVDF copolymer or terpolymer spin-coated film. At low particle concentrations, the matrix properties dominated the electrical measurements while at high concentrations, the samples were electrically fragile. The second sample type consisted of alternating layers of LB terpolymer and LB nanoparticles. These samples allowed for high particle concentrations while maintaining the high breakdown strength of the polymer layers. The final type of sample was titanium dioxide nanoparticles formed by cluster deposition and coated with an evaporated paraffin or VDF oligomer. These samples tended to have low breakdown strengths and poor

  11. Transient EPR Reveals Triplet State Delocalization in a Series of Cyclic and Linear π-Conjugated Porphyrin Oligomers.

    PubMed

    Tait, Claudia E; Neuhaus, Patrik; Peeks, Martin D; Anderson, Harry L; Timmel, Christiane R

    2015-07-01

    The photoexcited triplet states of a series of linear and cyclic butadiyne-linked porphyrin oligomers were investigated by transient Electron Paramagnetic Resonance (EPR) and Electron Nuclear DOuble Resonance (ENDOR). The spatial delocalization of the triplet state wave function in systems with different numbers of porphyrin units and different geometries was analyzed in terms of zero-field splitting parameters and proton hyperfine couplings. Even though no significant change in the zero-field splitting parameters (D and E) is observed for linear oligomers with two to six porphyrin units, the spin polarization of the transient EPR spectra is particularly sensitive to the number of porphyrin units, implying a change of the mechanism of intersystem crossing. Analysis of the proton hyperfine couplings in linear oligomers with more than two porphyrin units, in combination with density functional theory calculations, indicates that the spin density is localized mainly on two to three porphyrin units rather than being distributed evenly over the whole π-system. The sensitivity of the zero-field splitting parameters to changes in geometry was investigated by comparing free linear oligomers with oligomers bound to a hexapyridyl template. Significant changes in the zero-field splitting parameter D were observed, while the proton hyperfine couplings show no change in the extent of triplet state delocalization. The triplet state of the cyclic porphyrin hexamer has a much decreased zero-field splitting parameter D and much smaller proton hyperfine couplings with respect to the monomeric unit, indicating complete delocalization over six porphyrin units in this symmetric system. This surprising result provides the first evidence for extensive triplet state delocalization in an artificial supramolecular assembly of porphyrins. PMID:26035477

  12. Transient EPR Reveals Triplet State Delocalization in a Series of Cyclic and Linear π-Conjugated Porphyrin Oligomers

    PubMed Central

    2015-01-01

    The photoexcited triplet states of a series of linear and cyclic butadiyne-linked porphyrin oligomers were investigated by transient Electron Paramagnetic Resonance (EPR) and Electron Nuclear DOuble Resonance (ENDOR). The spatial delocalization of the triplet state wave function in systems with different numbers of porphyrin units and different geometries was analyzed in terms of zero-field splitting parameters and proton hyperfine couplings. Even though no significant change in the zero-field splitting parameters (D and E) is observed for linear oligomers with two to six porphyrin units, the spin polarization of the transient EPR spectra is particularly sensitive to the number of porphyrin units, implying a change of the mechanism of intersystem crossing. Analysis of the proton hyperfine couplings in linear oligomers with more than two porphyrin units, in combination with density functional theory calculations, indicates that the spin density is localized mainly on two to three porphyrin units rather than being distributed evenly over the whole π-system. The sensitivity of the zero-field splitting parameters to changes in geometry was investigated by comparing free linear oligomers with oligomers bound to a hexapyridyl template. Significant changes in the zero-field splitting parameter D were observed, while the proton hyperfine couplings show no change in the extent of triplet state delocalization. The triplet state of the cyclic porphyrin hexamer has a much decreased zero-field splitting parameter D and much smaller proton hyperfine couplings with respect to the monomeric unit, indicating complete delocalization over six porphyrin units in this symmetric system. This surprising result provides the first evidence for extensive triplet state delocalization in an artificial supramolecular assembly of porphyrins. PMID:26035477

  13. Prestin forms oligomer with four mechanically independent subunits

    PubMed Central

    Wang, Xiang; Yang, Shiming; Jia, Shuping; He, David Z.Z.

    2010-01-01

    Prestin is the motor protein of cochlear outer hair cells (OHCs) with the unique capability of performing direct, rapid and reciprocal electromechanical conversion. Prestin consists of 744 amino acids with a molecular mass of ~81.4 kDa. The predicted membrane topology and molecular mass of a single prestin molecule appear inadequate to account for the size of intramembrane particles (IMPs) expressed in the OHC membrane. Although recent biochemical evidence suggests that prestin forms homo-oligomers, most likely as a tetramer, the oligomeric structure of prestin in OHCs remains unclear. We obtained the charge density of prestin in the gerbil OHCs by measuring their nonlinear capacitance (NLC). The average charge density (22,608 μm−2) measured was four times the average IMP density (5,686 μm−2) reported in the freeze-fracture study. This suggests that each IMP contains four prestin molecules, based on the general notion that each prestin transfers a single elementary charge. We subsequently compared the voltage dependency and the values of slope factor of NLC and somatic motility simultaneously measured from the same OHCs to determine whether NLC and motility are fully coupled and how prestin subunits function within the tetramer. We showed that the voltage dependency and slope factors of NLC and motility were not statistically different, suggesting that NLC and motility are fully coupled. The fact that the slope factor is the same between NLC and motility suggests that each prestin monomer in the tetramer is in parallel, each interacting independently with cytoplasmic or other partners to facilitate the mechanical response. PMID:20347723

  14. Dietary deficiency increases presenilin expression, gamma-secretase activity, and Abeta levels: potentiation by ApoE genotype and alleviation by S-adenosyl methionine.

    PubMed

    Chan, Amy; Tchantchou, Flaubert; Rogers, Eugene J; Shea, Thomas B

    2009-08-01

    Apolipoprotein E4 (ApoE4) is a risk factor for Alzheimer's disease (AD). Whether this risk arises from a deficient function of E4 or the lack of protection provided by E2 or E3 is unclear. Previous studies demonstrate that deprivation of folate and vitamin E, coupled with dietary iron as a pro-oxidant, for 1 month displayed increased presenilin 1 (PS-1) expression, gamma-secretase, and Abeta generation in mice lacking ApoE (ApoE-/- mice). While ApoE-/- mice are a model for ApoE deficiency, they may not reflect the entire range of consequences of E4 expression. We therefore compared herein the impact of the above deficient diet on mice expressing human E2, E3, or E4. As folate deficiency is accompanied by a decrease in the major methyl donor, S-adenosyl methionine (SAM), additional mice received the deficient diet plus SAM. E2 was more protective than murine ApoE or E3 and E4. Surprisingly, PS-1 and gamma-secretase were over-expressed in E3 to the same extent as in E4 even under a complete diet, and were not alleviated by SAM supplementation. Abeta increased only in E4 mice maintained under the complete diet, and was alleviated by SAM supplementation. These findings suggest dietary compromise can potentiate latent risk factors for AD. PMID:19457069

  15. Amphiphilic oligomer-based micelles as cisplatin nanocarriers for cancer therapy

    NASA Astrophysics Data System (ADS)

    Qi, Xiuxiu; Li, Najun; Gu, Hongwei; Xu, Yujie; Xu, Ying; Jiao, Yang; Xu, Qingfeng; Li, Hua; Lu, Jianmei

    2013-09-01

    Polymeric micelles (~10 nm) have been prepared from the amphiphilic oligomer comprising oligomeric polystyrene as the hydrophobic inner core and half of EDTA (-N(CH2COOH)2) as the hydrophilic outermost shell. After chelating cisplatin with -N(CH2COOH)2 in water, polymeric micelles containing Pt on the spherical surface have been easily obtained. Since the chelate group is introduced into the amphiphilic oligomer as the terminal group by a RAFT agent, the chelation of cisplatin with PS(COOH)2 is almost stoichiometric. The drug carrier based on PS(COOH)2 showed a high loading efficiency (>70%) towards cisplatin. The release of the therapeutic Pt from the cisplatin-loaded composites (PS(COOH)2-Pt) triggered under weak acidic conditions resulted in good Pt-release and accumulation in tumor cells. Both in vitro and in vivo, the chelated cisplatin inhibited Sk-Br3 cancer more effectively than the intact cisplatin does. Furthermore, neither PS(COOH)2 nor PS(COOH)2-Pt showed obvious systematic toxicity.Polymeric micelles (~10 nm) have been prepared from the amphiphilic oligomer comprising oligomeric polystyrene as the hydrophobic inner core and half of EDTA (-N(CH2COOH)2) as the hydrophilic outermost shell. After chelating cisplatin with -N(CH2COOH)2 in water, polymeric micelles containing Pt on the spherical surface have been easily obtained. Since the chelate group is introduced into the amphiphilic oligomer as the terminal group by a RAFT agent, the chelation of cisplatin with PS(COOH)2 is almost stoichiometric. The drug carrier based on PS(COOH)2 showed a high loading efficiency (>70%) towards cisplatin. The release of the therapeutic Pt from the cisplatin-loaded composites (PS(COOH)2-Pt) triggered under weak acidic conditions resulted in good Pt-release and accumulation in tumor cells. Both in vitro and in vivo, the chelated cisplatin inhibited Sk-Br3 cancer more effectively than the intact cisplatin does. Furthermore, neither PS(COOH)2 nor PS(COOH)2-Pt showed obvious

  16. Dynamic imaging by fluorescence correlation spectroscopy identifies diverse populations of polyglutamine oligomers formed in vivo.

    PubMed

    Beam, Monica; Silva, M Catarina; Morimoto, Richard I

    2012-07-27

    Protein misfolding and aggregation are exacerbated by aging and diseases of protein conformation including neurodegeneration, metabolic diseases, and cancer. In the cellular environment, aggregates can exist as discrete entities, or heterogeneous complexes of diverse solubility and conformational state. In this study, we have examined the in vivo dynamics of aggregation using imaging methods including fluorescence microscopy, fluorescence recovery after photobleaching (FRAP), and fluorescence correlation spectroscopy (FCS), to monitor the diverse biophysical states of expanded polyglutamine (polyQ) proteins expressed in Caenorhabditis elegans. We show that monomers, oligomers and aggregates co-exist at different concentrations in young and aged animals expressing different polyQ-lengths. During aging, when aggregation and toxicity are exacerbated, FCS-based burst analysis and purified single molecule FCS detected a populational shift toward an increase in the frequency of brighter and larger oligomeric species. Regardless of age or polyQ-length, oligomers were maintained in a heterogeneous distribution that spans multiple orders of magnitude in brightness. We employed genetic suppressors that prevent polyQ aggregation and observed a reduction in visible immobile species with the persistence of heterogeneous oligomers, yet our analysis did not detect the appearance of any discrete oligomeric states associated with toxicity. These studies reveal that the reversible transition from monomers to immobile aggregates is not represented by discrete oligomeric states, but rather suggests that the process of aggregation involves a more complex pattern of molecular interactions of diverse intermediate species that can appear in vivo and contribute to aggregate formation and toxicity. PMID:22669943

  17. Ligation of RNA Oligomers by the Schistosoma mansoni Hammerhead Ribozyme in Frozen Solution.

    PubMed

    Lie, Lively; Biliya, Shweta; Vannberg, Fredrik; Wartell, Roger M

    2016-03-01

    The interstitial liquid phase within frozen aqueous solutions is an environment that minimizes RNA degradation and facilitates reactions that may have relevance to the RNA World hypothesis. Previous work has shown that frozen solutions support condensation of activated nucleotides into RNA oligomers, RNA ligation by the hairpin ribozyme, and RNA synthesis by a RNA polymerase ribozyme. In the current study, we examined the activity of a hammerhead ribozyme (HHR) in frozen solution. The Schistosoma mansoni hammerhead ribozyme, which predominantly cleaves RNA, can ligate its cleaved products (P1 and P2) with yields up to ~23 % in single turnover experiments at 25 °C in the presence of Mg(2+). Our studies show that this HHR ligates RNA oligomers in frozen solution in the absence of divalent cations. Citrate and other anions that exhibit strong ion-water affinity enhanced ligation. Yields up to 43 % were observed in one freeze-thaw cycle and a maximum of 60 % was obtained after several freeze-thaw cycles using wild-type P1 and P2. Truncated and mutated P1 substrates were ligated to P2 with yields of 14-24 % in one freeze-thaw cycle. A pool of P2 substrates with mixtures of all four bases at five positions were ligated with P1 in frozen solution. High-throughput sequencing indicated that 70 of the 1024 possible P2 sequences were represented in ligated products at 1000 or more read counts per million reads. The results indicate that the HHR can ligate a range of short RNA oligomers into an ensemble of diverse sequences in ice. PMID:26897022

  18. Efficient near-infrared organic light-emitting devices based on low-gap fluorescent oligomers

    NASA Astrophysics Data System (ADS)

    Yang, Yixing; Farley, Richard T.; Steckler, Timothy T.; Eom, Sang-Hyun; Reynolds, John R.; Schanze, Kirk S.; Xue, Jiangeng

    2009-08-01

    We report efficient near-infrared (NIR) organic light-emitting devices (OLEDs) based on fluorescent donor-acceptor-donor conjugated oligomers. The energies of the highest occupied and lowest unoccupied molecular orbitals of these oligomers are controlled by the donor and acceptor components, respectively; hence the energy gap and therefore the emission wavelength can be tuned by changing the strengths of the donor and acceptor components. External quantum efficiencies (EQEs) up to 1.6% and power efficiencies up to 7.0 mW/W are achieved in NIR OLEDs based on 4,9-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-6,7-dimethyl-[1,2,5]thiadiazolo[3,4-g]-quinoxaline (BEDOT-TQMe2), in which the electroluminescence peaks at a wavelength of 692 nm but extends to well above 800 nm. With a stronger acceptor in the oligomer, 4,8-bis(2,3-dihydrothieno-[3,4-b][1,4]dioxin-5-yl)benzo[1,2-c;4,5-c']bis [1,2,5]thiadiazole (BEDOT-BBT) based devices show longer wavelength emission peaked at 815 nm, although the maximum EQE is reduced to 0.51% due to the lower fluorescent quantum yield of the NIR emitter. The efficiencies of these NIR OLEDs are further increased by two to three times by using the sensitized fluorescent device structure, leading to a maximum EQE of 3.1% for BEDOT-TQMe2 and 1.6% for BEDOT-BBT based devices.

  19. Heteroatom-containing organic electronic oligomers and polymers: Electron paramagnetic resonance studies

    NASA Astrophysics Data System (ADS)

    Brenneman, Keith Richard

    Conjugated conducting polymers are organic materials which can be chemically modified or "doped" to exhibit the property of electrical conduction normally seen only in inorganic materials such as metals. Polyaniline (PAN) is of interest due to the fact that it can be switched between conducting and non-conducting forms without changing its oxidation state. Polythiophene (PT) and polypyrrole (PPy) have a conjugated structure, only the heteroatom (sulfur (S) or nitrogen (N)) is not part of the conducting backbone. However, the morphology and optimal chain length of these polymers are still matters of controversy. In order to explore these issues, X-band (9.5 GHz) electron paramagnetic resonance (EPR) susceptibility (X) and linewidth measurements of the undoped and aqueously camphor sulfonic acid (HCSA)-doped tetramer, octamer, and hexadecamer (oligomers) of aniline, the hexafluorophosphate (PF 6)- and trifluoromethylsulfonate (CF3SO3)-doped polymers of 3,4-ethylenedioxy-thiophene (EDOT) and 3,4-propylenedioxythiophene (ProDOT), and the PF6-doped polymer of 3,4-propylenedioxypyrrole (ProDOP) were undertaken. The undoped oligomer systems exhibit a spin density of ˜1 spin per 500 2-ring repeat units. The doped systems have both Pauli- and Curie-like susceptibility with chiPauli ˜ 40 x 10-6 emu/mole 2-ring repeat units and a localized spin density (nCurie) of ˜1 spin per 50 2-ring repeat units. It also is observed that both the undoped and doped oligomer samples exhibit a decreasing EPR DeltaHPP linewidth with increasing temperature and length, implying increasing delocalization with increasing temperature (intrachain motion) and oligomer length (interchain motion). The aniline oligomer data are compared to results for the undoped and the doped state of PAN. The PT and PPy systems also exhibit both Pauli- and Curie-like susceptibilities. In contrast to the aniline oligomers, it also is observed that both the PT and PPy samples exhibit an increasing EPR Delta

  20. Wnt-related SynGAP1 is a neuroprotective factor of glutamatergic synapses against Aβ oligomers.

    PubMed

    Codocedo, Juan F; Montecinos-Oliva, Carla; Inestrosa, Nibaldo C

    2015-01-01

    Wnt-5a is a synaptogenic factor that modulates glutamatergic synapses and generates neuroprotection against Aβ oligomers. It is known that Wnt-5a plays a key role in the adult nervous system and synaptic plasticity. Emerging evidence indicates that miRNAs are actively involved in the regulation of synaptic plasticity. Recently, we showed that Wnt-5a is able to control the expression of several miRNAs including miR-101b, which has been extensively studied in carcinogenesis. However, its role in brain is just beginning to be explored. That is why we aim to study the relationship between Wnt-5a and miRNAs in glutamatergic synapses. We performed in silico analysis which predicted that miR-101b may inhibit the expression of synaptic GTPase-Activating Protein (SynGAP1), a Ras GTPase-activating protein critical for the development of cognition and proper synaptic function. Through overexpression of miR-101b, we showed that miR-101b is able to regulate the expression of SynGAP1 in an hippocampal cell line. Moreover and consistent with a decrease of miR-101b, Wnt-5a enhances SynGAP expression in cultured hippocampal neurons. Additionally, Wnt-5a increases the activity of SynGAP in a time-dependent manner, with a similar kinetic to CaMKII phosphorylation. This also, correlates with a modulation in the SynGAP clusters density. On the other hand, Aβ oligomers permanently decrease the number of SynGAP clusters. Interestingly, when neurons are co-incubated with Wnt-5a and Aβ oligomers, we do not observe the detrimental effect of Aβ oligomers, indicating that, Wnt-5a protects neurons from the synaptic failure triggered by Aβ oligomers. Overall, our findings suggest that SynGAP1 is part of the signaling pathways induced by Wnt-5a. Therefore, possibility exists that SynGAP is involved in the synaptic protection against Aβ oligomers. PMID:26124704

  1. Wnt-related SynGAP1 is a neuroprotective factor of glutamatergic synapses against Aβ oligomers

    PubMed Central

    Codocedo, Juan F.; Montecinos-Oliva, Carla; Inestrosa, Nibaldo C.

    2015-01-01

    Wnt-5a is a synaptogenic factor that modulates glutamatergic synapses and generates neuroprotection against Aβ oligomers. It is known that Wnt-5a plays a key role in the adult nervous system and synaptic plasticity. Emerging evidence indicates that miRNAs are actively involved in the regulation of synaptic plasticity. Recently, we showed that Wnt-5a is able to control the expression of several miRNAs including miR-101b, which has been extensively studied in carcinogenesis. However, its role in brain is just beginning to be explored. That is why we aim to study the relationship between Wnt-5a and miRNAs in glutamatergic synapses. We performed in silico analysis which predicted that miR-101b may inhibit the expression of synaptic GTPase-Activating Protein (SynGAP1), a Ras GTPase-activating protein critical for the development of cognition and proper synaptic function. Through overexpression of miR-101b, we showed that miR-101b is able to regulate the expression of SynGAP1 in an hippocampal cell line. Moreover and consistent with a decrease of miR-101b, Wnt-5a enhances SynGAP expression in cultured hippocampal neurons. Additionally, Wnt-5a increases the activity of SynGAP in a time-dependent manner, with a similar kinetic to CaMKII phosphorylation. This also, correlates with a modulation in the SynGAP clusters density. On the other hand, Aβ oligomers permanently decrease the number of SynGAP clusters. Interestingly, when neurons are co-incubated with Wnt-5a and Aβ oligomers, we do not observe the detrimental effect of Aβ oligomers, indicating that, Wnt-5a protects neurons from the synaptic failure triggered by Aβ oligomers. Overall, our findings suggest that SynGAP1 is part of the signaling pathways induced by Wnt-5a. Therefore, possibility exists that SynGAP is involved in the synaptic protection against Aβ oligomers. PMID:26124704

  2. Synthesis of long Prebiotic Oligomers on Mineral Surfaces

    NASA Technical Reports Server (NTRS)

    Ferris, James P.; Hill, Aubrey R., Jr.; Liu, Rihe; Orgel, Leslie E.

    1996-01-01

    Most theories of the origin of biological organization assume that polymers with lengths in the range of 30-60 monomers are needed to make a genetic system viable. But it has not proved possible to synthesize plausibly prebiotic polymers this long by condensation in aqueous solution, because hydrolysis competes with polymerization. The potential of mineral surfaces to facilitate prebiotic polymerization was pointed out long ago. Here we describe a system that models prebiotic polymerization by the oligomerization of activated monomers -both nucleotides and amino acids. We find that whereas the reactions in solution produce only short oligomers (the longest typically being a 10-mer), the presence of mineral surfaces (montmorillonite for nucleotides, illite and hydroxylapatite for amino adds) induces the formation of oligomers up to 55 monomers long. These are formed by successive "feedings" with the monomers; polymerization takes place on the mineral surfaces in a manner akin to solid-phase synthesis of biopolymers.

  3. Phase transition in conjugated oligomers suspended in chloroform

    NASA Astrophysics Data System (ADS)

    Dwivedi, Shikha; Kumar, Anupam; Yadav, S. N. S.; Mishra, Pankaj

    2015-08-01

    Density functional theory (DFT) has been used to investigate the isotropic-nematic (I-N) phase transition in a system of high aspect ratio conjugated oligomers suspended in chloroform. The interaction between the oligomers is modeled using Gay-Berne potential in which effect of solvent is implicit. Percus-Yevick integral equation theory has been used to evaluate the pair correlation functions of the fluid phase at several temperatures and densities. These pair correlation function has been used in the DFT to evaluate the I-N freezing parameters. Highly oriented nematic is found to stabilize at low density. The results obtained are in qualitative agreement with the simulation and are verifiable.

  4. Pigment oligomers as natural and artificial photosynthetic antennas

    SciTech Connect

    Blankenship, R.E.

    1996-12-31

    Green photosynthetic bacteria contain antenna complexes known as chlorosomes. These complexes are appressed to the cytoplasmic side of the inner cell membrane and function to absorb light and transfer the energy to the photochemical reaction center, where photochemical energy storage takes place. Chlorosomes differ from all other known photosynthetic antenna complexes in that the geometrical arrangement of pigments is determined primarily by pigment-pigment interactions instead of pigment-protein interactions. The bacteriochlorophyll c, d or e pigments found in chlorosomes form large oligomers with characteristic spectral properties significantly perturbed from those exhibited by monomeric pigments. Because of their close spatial interaction, the pigments are thought to be strongly coupled electronically, and many of the optical properties result from exciton interactions. This presentation will summarize existing knowledge on the chemical composition and properties of chlorosomes, the evidence for the oligomeric nature of chlorosome pigment organization and proposed structures for the oligomers, and the kinetics and mechanisms of energy transfer in chlorosomes.

  5. Ethynyl-terminated ester oligomers and polymers therefrom

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (Inventor); Havens, Stephen J. (Inventor)

    1986-01-01

    A class of ethynyl terminated oligomers and the process for preparing the same are disclosed. Upon the application of heat, with or without a catalyst, the ethynyl groups react to provide crosslinking and chain extension to increase the polymer use temperature and improve the polymer solvent resistance. These polyesters are potentially useful in packaging, magnetic tapes, capacitors, industrial belting, protective coatings, structural adhesives and composite matrices.

  6. Aβ42 oligomers selectively disrupt neuronal calcium release.

    PubMed

    Lazzari, Cristian; Kipanyula, Maulilio J; Agostini, Mario; Pozzan, Tullio; Fasolato, Cristina

    2015-02-01

    Accumulation of amyloid-β (Aβ) peptides correlates with aging and progression of Alzheimer's disease (AD). Aβ peptides, which cause early synaptic dysfunctions, spine loss, and memory deficits, also disturb intracellular Ca(2+) homeostasis. By cytosolic and endoplasmic reticulum Ca(2+) measurements, we here define the short-term effects of synthetic Aβ42 on neuronal Ca(2+) dynamics. When applied acutely at submicromolar concentration, as either oligomers or monomers, Aβ42 did not cause Ca(2+) release or Ca(2+) influx. Similarly, 1-hour treatment with Aβ42 modified neither the resting cytosolic Ca(2+) level nor the long-lasting Ca(2+) influx caused by KCl-induced depolarization. In contrast, Aβ42 oligomers, but not monomers, significantly altered Ca(2+) release from stores with opposite effects on inositol 1,4,5-trisphosphate (IP3)- and caffeine-induced Ca(2+) mobilization without alteration of the total store Ca(2+) content. Ca(2+) dysregulation by Aβ42 oligomers involves metabotropic glutamate receptor 5 and requires network activity and the intact exo-endocytotic machinery, being prevented by tetrodotoxin and tetanus toxin. These findings support the idea that Ca(2+) store dysfunction is directly involved in Aβ42 neurotoxicity and represents a potential therapeutic target in AD-like dementia. PMID:25453559

  7. The Viscoelastic Behavior of Polymer/Oligomer Blends

    NASA Astrophysics Data System (ADS)

    Zheng, Wei; McKenna, Gregory; Simon, Sindee

    2009-03-01

    The dynamics in athermal blends of poly(α-methyl styrene) (PaMS) and its short chain oligomer are investigated using rheometry and differential scanning calorimetry (DSC). Master curves for the dynamic shear responses, G' and G", are successfully constructed for both the pure materials and the blends, indicating the validity of the time-temperature superposition principle. The temperature dependence of the shift factor follows the WLF (Williams-Landel-Ferry) behavior over the temperature range studied, and for the blends, the dependence is dominated by the high mobility oligomer. The discrete relaxation spectra of the materials are calculated and are found to be broader for the blends than for the pure materials. A similar domination of the dynamics by the oligomer is observed in DSC enthalpy recovery studies and in the broadened glass transition from DSC. The ability to predict the dynamic responses of the blends from the responses of the neat materials is examined, and whether this prediction needs to incorporate the self-concentration idea as described in Colmenero's model will be discussed.

  8. Oligomers, organosulfates, and nitroxy organosulfates identified in rainwater

    NASA Astrophysics Data System (ADS)

    Altieri, K. E.; Turpin, B. J.; Seitzinger, S. P.

    2008-12-01

    Wet deposition is an important removal mechanism for atmospheric organic matter, and a potentially important input for receiving ecosystems, yet less than 50 percent of rainwater organic matter is considered chemically characterized. Precipitation samples collected in New Jersey, USA, were analyzed by negative ion ultra-high resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). We document the presence of 552 unique compounds in the rainwater over a mass range of 50-500 Da, in four compound classes (i.e., CHO, CHOS, CHON, and CHONS). The presence of oligomers, organosulfates, nitroxy organosulfates, organic acids, and linear alkylbenzene sulfonates is reported. Some compounds detected have distinct primary sources; however, the composition of the bulk of this material suggests it is formed in the atmosphere and composed of known contributors to secondary organic aerosol. For example, eight oligomer series known to form through aqueous photooxidation of methylglyoxal and organosulfate compounds known to form from 4 precursors in smog chamber experiments were identified in the rainwater samples. The oligomers, organosulfates, and nitroxy organosulfates detected in the rainwater could all contribute to the HULIS fraction of atmospheric organic matter.

  9. Synthesis of novel polyfluorinated acrylic monomers and oligomers

    SciTech Connect

    Antonucci, J.M.; Stansbury, J.W.

    1993-12-31

    An unhindered tertiary amine catalyzed reaction of monofunctional and difunctional hydrocarbon acrylates with paraformaldehyde under neat conditions yields unique difunctional acrylic monomers and oligomers, respectively. These multifunctional vinyl products have a predominantly 1,6-diene structure which favors cyclopolymerization. This reaction has been extended to the synthesis of similar polyfluorinated aliphatic monomers arrangements are determined by the nature of their fluoroester groups, e.g.-CF{sub 2}CH{sub 2}O{sub 2}C- favors a 1,4-diene rather than a 1,6-diene structure. In the present study the scope of this novel formaldehyde/acrylate insertion condensation reaction was further extended to include the synthesis of polyfluorinated aryl difunctional monomers and oligomers, e.g. from 2,3,4,5,6-pentafluorobenzyl acrylate and hexafluorobisphenol A diacrylate. The former did not require DMSO and yielded 1,6-, 1,8- and 1,10-dienes whereas the latter required DMSO and yielded oligomers mainly with 1,4-diene linkages.

  10. Size-dependent neurotoxicity of β-amyloid oligomers

    PubMed Central

    Cizas, Paulius; Budvytyte, Rima; Morkuniene, Ramune; Moldovan, Radu; Broccio, Matteo; Lösche, Mathias; Niaura, Gediminas; Valincius, Gintaras; Borutaite, Vilmante

    2010-01-01

    The link between the size of soluble amyloid β (Aβ) oligomers and their toxicity to rat cerebellar granule cells (CGC) was investigated. Variation in conditions during in vitro oligomerization of Aβ1-42 resulted in peptide assemblies with different particle size as measured by atomic force microscopy and confirmed by the dynamic light scattering and fluorescence correlation spectroscopy. Small oligomers of Aβ1-42 with a mean particle z-height of 1-2 nm exhibited propensity to bind to the phospholipid vesicles and they were the most toxic species that induced rapid neuronal necrosis at submicromolar concentrations whereas the bigger aggregates (z-height above 4-5 nm) did not bind vesicles and did not cause detectable neuronal death. Similar neurotoxic pattern was also observed in primary cultures of cortex neurons whereas Aβ1–42 oligomers, monomers and fibrils were non-toxic to glial cells in CGC cultures or macrophage J774 cells. However, both oligomeric forms of Aβ1-42 induced reduction of neuronal cell densities in the CGC cultures. PMID:20153288

  11. Automated fluorous-assisted solution-phase synthesis of β-1,2-, 1,3-, and 1,6-mannan oligomers.

    PubMed

    Tang, Shu-Lun; Pohl, Nicola L B

    2016-07-22

    Automated solution-phase syntheses of β-1,2-, 1,3-, and 1,6-mannan oligomers have been accomplished by applying a β-directing C-5 carboxylate strategy. Fluorous-tag-assisted purification after each reaction cycle allowed the synthesis of short β-mannan oligomers with limited loading of glycosyl donor-as low as 3.0 equivalents for each glycosylation cycle. This study showed the capability of the automated solution-phase synthesis protocol for synthesizing various challenging glycosides, including use of a C-5 ester as a protecting group that could be converted under reductive conditions to a hydroxymethyl group for chain extension. PMID:27155895

  12. Oligomer formation in the troposphere: from experimental knowledge to 3-D modeling

    NASA Astrophysics Data System (ADS)

    Lemaire, V.; Coll, I.; Couvidat, F.; Mouchel-Vallon, C.; Seigneur, C.; Siour, G.

    2015-10-01

    The organic fraction of atmospheric aerosols has proven to be a critical element of air quality and climate issues. However, its composition and the aging processes it undergoes remain insufficiently understood. This work builds on laboratory knowledge to simulate the formation of oligomers from biogenic secondary organic aerosol (BSOA) in the troposphere at the continental scale. We compare the results of two different modeling approaches, a 1st-order kinetic process and a pH-dependent parameterization, both implemented in the CHIMERE air quality model (AQM), to simulate the spatial and temporal distribution of oligomerized SOA over western Europe. Our results show that there is a strong dependence of the results on the selected modeling approach: while the irreversible kinetic process leads to the oligomerization of about 50 % of the total BSOA mass, the pH-dependent approach shows a broader range of impacts, with a strong dependency on environmental parameters (pH and nature of aerosol) and the possibility for the process to be reversible. In parallel, we investigated the sensitivity of each modeling approach to the representation of SOA precursor solubility (Henry's law constant values). Finally, the pros and cons of each approach for the representation of SOA aging are discussed and recommendations are provided to improve current representations of oligomer formation in AQMs.

  13. Direct visualization of alpha-synuclein oligomers reveals previously undetected pathology in Parkinson’s disease brain

    PubMed Central

    Roberts, Rosalind F.

    2015-01-01

    Oligomeric forms of alpha-synuclein are emerging as key mediators of pathogenesis in Parkinson’s disease. Our understanding of the exact contribution of alpha-synuclein oligomers to disease is limited by the lack of a technique for their specific detection. We describe a novel method, the alpha-synuclein proximity ligation assay, which specifically recognizes alpha-synuclein oligomers. In a blinded study with post-mortem brain tissue from patients with Parkinson’s disease (n = 8, age range 73–92 years, four males and four females) and age- and sex-matched controls (n = 8), we show that the alpha-synuclein proximity ligation assay reveals previously unrecognized pathology in the form of extensive diffuse deposition of alpha-synuclein oligomers. These oligomers are often localized, in the absence of Lewy bodies, to neuroanatomical regions mildly affected in Parkinson’s disease. Diffuse alpha-synuclein proximity ligation assay signal is significantly more abundant in patients compared to controls in regions including the cingulate cortex (1.6-fold increase) and the reticular formation of the medulla (6.5-fold increase). In addition, the alpha-synuclein proximity ligation assay labels very early perikaryal aggregates in morphologically intact neurons that may precede the development of classical Parkinson’s disease lesions, such as pale bodies or Lewy bodies. Furthermore, the alpha-synuclein proximity ligation assay preferentially detects early-stage, loosely compacted lesions such as pale bodies in patient tissue, whereas Lewy bodies, considered heavily compacted late lesions are only very exceptionally stained. The alpha-synuclein proximity ligation assay preferentially labels alpha-synuclein oligomers produced in vitro compared to monomers and fibrils, while stained oligomers in human brain display a distinct intermediate proteinase K resistance, suggesting the detection of a conformer that is different from both physiological, presynaptic alpha

  14. Folic acid-polydopamine nanofibers show enhanced ordered-stacking via π-π interactions.

    PubMed

    Fan, Hailong; Yu, Xiang; Liu, Yang; Shi, Zujin; Liu, Huihui; Nie, Zongxiu; Wu, Decheng; Jin, Zhaoxia

    2015-06-21

    Recent research has indicated that polydopamine and synthetic eumelanins are optoelectronic biomaterials in which one-dimensional aggregates composed of ordered-stacking oligomers have been proposed as unique organic semiconductors. However, improving the ordered-stacking of oligomers in polydopamine nanostructures is a big challenge. Herein, we first demonstrate how folic acid molecules influence the morphology and nanostructure of polydopamine via tuning the π-π interactions of oligomers. MALDI-TOF mass spectrometry reveals that porphyrin-like tetramers are characteristic of folic acid-polydopamine (FA-PDA) nanofibers. X-ray diffraction combined with simulation studies indicate that these oligomers favour aggregation into graphite-like ordered nanostructures via strong π-π interactions. High-resolution TEM characterization of carbonized FA-PDA hybrids show that in FA-PDA nanofibers the size of the graphite-like domains is over 100 nm. The addition of folic acid in polydopamine enhances the ordered stacking of oligomers in its nanostructure. Our study steps forward to discover the mystery of the structure-property relationship of FA-PDA hybrids. It paves a way to optimize the properties of PDA through the design and selection of oligomer structures. PMID:25959650

  15. Crystallization and preliminary X-ray diffraction analysis of the Fab fragment of WO2, an antibody specific for the A[beta] peptides associated with Alzheimer's disease

    SciTech Connect

    Wun, Kwok S.; Miles, Luke A.; Crespi, Gabriela A.N.; Wycherley, Kaye; Ascher, David B.; Barnham, Kevin J.; Cappai, Roberto; Beyreuther, Konrad; Masters, Colin L.; Parker, Michael W.; McKinstry, William J.

    2008-05-28

    The murine monoclonal antibody WO2 specifically binds the N-terminal region of the amyloid {beta} peptide (A{beta}) associated with Alzheimer's disease. This region of A{beta} has been shown to be the immunodominant B-cell epitope of the peptide and hence is considered to be a basis for the development of immunotherapeutic strategies against this prevalent cause of dementia. Structural studies have been undertaken in order to characterize the molecular basis for antibody recognition of this important epitope. Here, details of the crystallization and X-ray analysis of the Fab fragment of the unliganded WO2 antibody in two crystal forms and of the complexes that it forms with the truncated Az{beta} peptides A{beta}{sub 1-16} and A{beta}{sub 1-28} are presented. These crystals were all obtained using the hanging-drop vapour-diffusion method at 295 K. Crystals of WO2 Fab were grown in polyethylene glycol solutions containing ZnSO{sub 4}; they belonged to the orthorhombic space group P2{sub 1}2{sub 1}2{sub 1} and diffracted to 1.6 {angstrom} resolution. The complexes of WO2 Fab with either A{beta}{sub 1-16} or A{beta}{sub 1-28} were cocrystallized from polyethylene glycol solutions. These two complex crystals grew in the same space group, P2{sub 1}2{sub 1}2{sub 1}, and diffracted to 1.6 {angstrom} resolution. A second crystal form of WO2 Fab was grown in the presence of the sparingly soluble A{beta}{sub 1-42} in PEG 550 MME. This second form belonged to space group P2{sub 1} and diffracted to 1.9 {angstrom} resolution.

  16. A Versatile Method for the Preparation of Ferroelectric Supramolecular Materials via Radical End-Functionalization of Vinylidene Fluoride Oligomers.

    PubMed

    García-Iglesias, Miguel; de Waal, Bas F M; Gorbunov, Andrey V; Palmans, Anja R A; Kemerink, Martijn; Meijer, E W

    2016-05-18

    A synthetic method for the end-functionalization of vinylidene fluoride oligomers (OVDF) via a radical reaction between terminal olefins and I-OVDF is described. The method shows a wide substrate scope and excellent conversions, and permits the preparation of different disc-shaped cores such as benzene-1,3,5-tricarboxamides (BTAs), perylenes bisimide (PBI), and phthalocyanines (Pc) bearing three to eight ferroelectric oligomers at their periphery. The formation, purity, OVDF conformation, and morphology of the final adducts has been assessed by a combination of techniques, such as NMR, size exclusion chromatography, differential scanning calorimetry, polarized optical microscopy, and atomic force microscopy. Finally, PBI-OVDF and Pc-OVDF materials show ferroelectric hysteresis behavior together with high remnant polarizations, with values as high as Pr ≈ 37 mC/m(2) for Pc-OVDF. This work demonstrates the potential of preparing a new set of ferroelectric materials simply by attaching OVDF oligomers to different small molecules. The use of carefully chosen small molecules paves the way to new functional materials in which ferroelectricity and electrical conductivity or light-harvesting properties coexist in a single compound. PMID:27119732

  17. Radiative decay of excitons in model aggregates of {pi}-conjugated oligomers

    SciTech Connect

    Manas, E.S.; Spano, F.C.

    1998-07-01

    Spontaneous emission from exciton states in an aggregate of {pi}-conjugated oligomers is studied theoretically. Each oligomer is taken as a ring of N carbon atoms and is treated using a PPP Hamiltonian. Coulombic interactions between rings are treated to first order. The radiative decay rate {gamma} from an exciton state in an aggregate of M aligned oligomers is superradiant, being M times faster than the decay rate of an isolated oligomer exciton. Inter-oligomer interactions have little effect on the exciton size and energy when the oligomer size N is large compared to the interoligomer spacing. However, when N is small, both the exciton size and energy are strongly affected by these interactions, leading to a markedly different N dependence for {gamma}.

  18. Intrinsic versus imposed curvature in cyclical oligomers: the portal protein of bacteriophage SPP1.

    PubMed Central

    van Heel, M; Orlova, E V; Dube, P; Tavares, P

    1996-01-01

    Large cyclical oligomers may be formed by (curvi-) linear polymerization of monomers until the n(th) monomer locks in with the first member of the chain. The subunits in incomplete structures exhibit a natural curvature with respect to each other which can be perturbed when the oligomer closes cyclically. Using cryo-electron microscopy and multivariate statistical image processing we report herein a direct structural observation of this effect. A sub-population (approximately 15%) of incomplete oligomers was found within a sample of SPP1 bacteriophage portal proteins embedded in vitreous ice. Whereas the curvature between adjacent subunits of the closed circular 13-fold symmetric oligomer is 27.7 degrees, in these incomplete oligomers the angle is only 25.8 degrees, a value which almost allows for a 14-subunit cyclical arrangement. A simple model for the association of large cyclical oligomers is suggested by our data. Images PMID:8890151

  19. Apoptosis induced by islet amyloid polypeptide soluble oligomers is neutralized by diabetes-associated specific antibodies

    PubMed Central

    Bram, Yaron; Frydman-Marom, Anat; Yanai, Inbal; Gilead, Sharon; Shaltiel-Karyo, Ronit; Amdursky, Nadav; Gazit, Ehud

    2014-01-01

    Soluble oligomeric assemblies of amyloidal proteins appear to act as major pathological agents in several degenerative disorders. Isolation and characterization of these oligomers is a pivotal step towards determination of their pathological relevance. Here we describe the isolation of Type 2 diabetes-associated islet amyloid polypeptide soluble cytotoxic oligomers; these oligomers induced apoptosis in cultured pancreatic cells, permeated model lipid vesicles and interacted with cell membranes following complete internalization. Moreover, antibodies which specifically recognized these assemblies, but not monomers or amyloid fibrils, were exclusively identified in diabetic patients and were shown to neutralize the apoptotic effect induced by these oligomers. Our findings support the notion that human IAPP peptide can form highly toxic oligomers. The presence of antibodies identified in the serum of diabetic patients confirms the pathological relevance of the oligomers. In addition, the newly identified structural epitopes may also provide new mechanistic insights and a molecular target for future therapy. PMID:24589570

  20. Soluble prion protein and its N-terminal fragment prevent impairment of synaptic plasticity by Aβ oligomers: Implications for novel therapeutic strategy in Alzheimer's disease.

    PubMed

    Scott-McKean, Jonah J; Surewicz, Krystyna; Choi, Jin-Kyu; Ruffin, Vernon A; Salameh, Ahlam I; Nieznanski, Krzysztof; Costa, Alberto C S; Surewicz, Witold K

    2016-07-01

    The pathogenic process in Alzheimer's disease (AD) appears to be closely linked to the neurotoxic action of amyloid-β (Aβ) oligomers. Recent studies have shown that these oligomers bind with high affinity to the membrane-anchored cellular prion protein (PrP(C)). It has also been proposed that this binding might mediate some of the toxic effects of the oligomers. Here, we show that the soluble (membrane anchor-free) recombinant human prion protein (rPrP) and its N-terminal fragment N1 block Aβ oligomers-induced inhibition of long-term potentiation (LTP) in hippocampal slices, an important surrogate marker of cognitive deficit associated with AD. rPrP and N1 are also strikingly potent inhibitors of Aβ cytotoxicity in primary hippocampal neurons. Furthermore, experiments using hippocampal slices and neurons from wild-type and PrP(C) null mice (as well as rat neurons in which PrP(C) expression was greatly reduced by gene silencing) indicate that, in contrast to the impairment of synaptic plasticity by Aβ oligomers, the cytotoxic effects of these oligomers, and the inhibition of these effects by rPrP and N1, are independent of the presence of endogenous PrP(C). This suggests fundamentally different mechanisms by which soluble rPrP and its fragments inhibit these two toxic responses to Aβ. Overall, these findings provide strong support to recent suggestions that PrP-based compounds may offer new avenues for pharmacological intervention in AD. PMID:26949218

  1. Perforin oligomers form arcs in cellular membranes: a locus for intracellular delivery of granzymes

    PubMed Central

    Metkar, S S; Marchioretto, M; Antonini, V; Lunelli, L; Wang, B; Gilbert, R JC; Anderluh, G; Roth, R; Pooga, M; Pardo, J; Heuser, J E; Serra, M D; Froelich, C J

    2015-01-01

    Perforin-mediated cytotoxicity is an essential host defense, in which defects contribute to tumor development and pathogenic disorders including autoimmunity and autoinflammation. How perforin (PFN) facilitates intracellular delivery of pro-apoptotic and inflammatory granzymes across the bilayer of targets remains unresolved. Here we show that cellular susceptibility to granzyme B (GzmB) correlates with rapid PFN-induced phosphatidylserine externalization, suggesting that pores are formed at a protein-lipid interface by incomplete membrane oligomers (or arcs). Supporting a role for these oligomers in protease delivery, an anti-PFN antibody (pf-80) suppresses necrosis but increases phosphatidylserine flip-flop and GzmB-induced apoptosis. As shown by atomic force microscopy on planar bilayers and deep-etch electron microscopy on mammalian cells, pf-80 increases the proportion of arcs which correlates with the presence of smaller electrical conductances, while large cylindrical pores decline. PFN appears to form arc structures on target membranes that serve as minimally disrupting conduits for GzmB translocation. The role of these arcs in PFN-mediated pathology warrants evaluation where they may serve as novel therapeutic targets. PMID:25146929

  2. Extracellular Tau Oligomers Produce An Immediate Impairment of LTP and Memory

    PubMed Central

    Fá, M.; Puzzo, D.; Piacentini, R.; Staniszewski, A.; Zhang, H.; Baltrons, M. A.; Li Puma, D. D.; Chatterjee, I.; Li, J.; Saeed, F.; Berman, H. L.; Ripoli, C.; Gulisano, W.; Gonzalez, J.; Tian, H.; Costa, J. A.; Lopez, P.; Davidowitz, E.; Yu, W. H.; Haroutunian, V.; Brown, L. M.; Palmeri, A.; Sigurdsson, E. M.; Duff, K. E.; Teich, A. F.; Honig, L. S.; Sierks, M.; Moe, J. G.; D’Adamio, L.; Grassi, C.; Kanaan, N. M.; Fraser, P. E.; Arancio, O.

    2016-01-01

    Non-fibrillar soluble oligomeric forms of amyloid-β peptide (oAβ) and tau proteins are likely to play a major role in Alzheimer’s disease (AD). The prevailing hypothesis on the disease etiopathogenesis is that oAβ initiates tau pathology that slowly spreads throughout the medial temporal cortex and neocortices independently of Aβ, eventually leading to memory loss. Here we show that a brief exposure to extracellular recombinant human tau oligomers (oTau), but not monomers, produces an impairment of long-term potentiation (LTP) and memory, independent of the presence of high oAβ levels. The impairment is immediate as it raises as soon as 20 min after exposure to the oligomers. These effects are reproduced either by oTau extracted from AD human specimens, or naturally produced in mice overexpressing human tau. Finally, we found that oTau could also act in combination with oAβ to produce these effects, as sub-toxic doses of the two peptides combined lead to LTP and memory impairment. These findings provide a novel view of the effects of tau and Aβ on memory loss, offering new therapeutic opportunities in the therapy of AD and other neurodegenerative diseases associated with Aβ and tau pathology. PMID:26786552

  3. Preparation of crystalline and solvent resistant polycarbonates via ring-opening polymerization of cyclic oligomers

    SciTech Connect

    Brunelle, D.J.; Krabbenhoft, H.O.; Bonauto, D.K.

    1993-12-31

    Development of efficient methods for the preparation and polymerization of cyclic oligomeric aromatic carbonates has allowed the facile preparation of a variety of polycarbonates. Because the cyclic oligomers can be converted directly into high molecular weight polycarbonates in the absence of solvent, and without formation of by-products, this route is especially attractive for the fabrication of composite structures. This paper reports that crystalline and/or solvent-resistant polycarbonates can be prepared via the intermediacy of cyclic oligomers. Copolycarbonates of bisphenol A with hydroquinone, resorcinol, or methylhydroquinone were insoluble in CH{sub 2}Cl{sub 2}, and showed crystalline melting points in some cases. For example, a 60/40 HQ/BPA polycarbonate had a glass transition temperature of 154{degrees}C, and a melting point of 313{degrees}C, with a heat of melting of 11.0 J/g, while a 100% methylhydroquinone polycarbonate had a Tg of 155{degrees}C and a melting point of 289{degrees}C, with a heat of melting of 31.0 J/g.

  4. Perforin oligomers form arcs in cellular membranes: a locus for intracellular delivery of granzymes.

    PubMed

    Metkar, S S; Marchioretto, M; Antonini, V; Lunelli, L; Wang, B; Gilbert, R J C; Anderluh, G; Roth, R; Pooga, M; Pardo, J; Heuser, J E; Serra, M D; Froelich, C J

    2015-01-01

    Perforin-mediated cytotoxicity is an essential host defense, in which defects contribute to tumor development and pathogenic disorders including autoimmunity and autoinflammation. How perforin (PFN) facilitates intracellular delivery of pro-apoptotic and inflammatory granzymes across the bilayer of targets remains unresolved. Here we show that cellular susceptibility to granzyme B (GzmB) correlates with rapid PFN-induced phosphatidylserine externalization, suggesting that pores are formed at a protein-lipid interface by incomplete membrane oligomers (or arcs). Supporting a role for these oligomers in protease delivery, an anti-PFN antibody (pf-80) suppresses necrosis but increases phosphatidylserine flip-flop and GzmB-induced apoptosis. As shown by atomic force microscopy on planar bilayers and deep-etch electron microscopy on mammalian cells, pf-80 increases the proportion of arcs which correlates with the presence of smaller electrical conductances, while large cylindrical pores decline. PFN appears to form arc structures on target membranes that serve as minimally disrupting conduits for GzmB translocation. The role of these arcs in PFN-mediated pathology warrants evaluation where they may serve as novel therapeutic targets. PMID:25146929

  5. Molecular dynamics simulations of silica nanoparticles grafted with poly(ethylene oxide) oligomer chains.

    PubMed

    Hong, Bingbing; Panagiotopoulos, Athanassios Z

    2012-03-01

    A molecular model of silica nanoparticles grafted with poly(ethylene oxide) oligomers has been developed for predicting the transport properties of nanoparticle organic-hybrid materials (NOHMs). Ungrafted silica nanoparticles in a medium of poly(ethylene oxide) oligomers were also simulated to clarify the effect of grafting on the dynamics of nanoparticles and chains. The model approximates nanoparticles as solid spheres and uses a united-atom representation for chains, including torsional and bond-bending interactions. The calculated viscosities from Green-Kubo relationships and temperature extrapolation are of the same order of magnitude as experimental data but show a smaller activation energy relative to real NOHMs systems. Grafted systems have higher viscosities, smaller diffusion coefficients, and slower chain dynamics than the ungrafted ones at high temperatures. At lower temperatures, grafted systems exhibit faster dynamics for both nanoparticles and chains relative to ungrafted systems, because of lower aggregation of particles and enhanced correlations between nanoparticles and chains. This agrees with the experimental observation that NOHMs have liquidlike behavior in the absence of a solvent. For both grafted and ungrafted systems at low temperatures, increasing chain length reduces the volume fraction of nanoparticles and accelerates the dynamics. However, at high temperatures, longer chains slow down nanoparticle diffusion. From the Stokes-Einstein relationship, it was determined that the coarse-grained treatment of nanoparticles leads to slip on the nanoparticle surfaces. Grafted systems obey the Stokes-Einstein relationship over the temperature range simulated, but ungrafted systems display deviations from it. PMID:22243140

  6. Annotation of Different Dehydrocatechin Oligomers by MS/MS and Their Occurrence in Black Tea.

    PubMed

    Verloop, Annewieke J W; Gruppen, Harry; Vincken, Jean-Paul

    2016-08-01

    Dehydrocatechins (DhC's), oligomeric oxidation products of (epi)catechins, were formed in model incubations of epicatechin with mushroom tyrosinase. DhC oligomers up to tetramers were detected by reversed-phase ultrahigh-performance liquid chromatography mass spectrometry (RP-UHPLC-MS) analysis. Measurements with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) showed formation of oligomers up to at least 15 catechin subunits. Isomeric DhC's were obtained, and a method based on MS(2) fragment ratios was set up to distinguish between the different interflavanic configurations of the isomers. In the model incubation, 8 dehydrodicatechins (DhC2's) and 22 dehydrotricatechins (DhC3's) were tentatively annotated by their MS(2) signature fragments. Three different interflavanic configuration types were determined for the DhC2's. DhC2's and DhC3's were shown to occur in a black tea extract for the first time. For the DhC2's, at least two isomeric types, i.e., DhC β and DhC ε, could be annotated in black tea. PMID:27380714

  7. The effects of soluble Aβ oligomers on neurodegeneration in Alzheimer's disease.

    PubMed

    Brouillette, Jonathan

    2014-01-01

    The neurodegenerative process that defines Alzheimer''s disease (AD) is initially characterized by synaptic alterations followed by synapse loss and ultimately cell death. Decreased synaptic density that precedes neuronal death is the strongest pathological correlate of cognitive deficits observed in AD. Substantial synapse and neuron loss occur early in disease progression in the entorhinal cortex (EC) and the CA1 region of the hippocampus, when memory deficits become clinically detectable. Mounting evidence suggests that soluble amyloid-β (Aβ) oligomers trigger synapse dysfunction both in vitro and in vivo. However, the neurodegenerative effect of Aβ species observed on neuronal culture or organotypic brain slice culture has been more challenging to mimic in animal models. While most of the transgenic mice that overexpress Aβ show abundant amyloid plaque pathology and early synaptic alterations, these models have been less successful in recapitulating the spatiotemporal pattern of cell loss observed in AD. Recently we developed a novel animal model that revealed the neurodegenerative effect of soluble low-molecular-weight Aβ oligomers in vivo. This new approach may now serve to determine the molecular and cellular mechanisms linking soluble Aβ species to neurodegeneration in animals. In light of the low efficiency of AD therapies based on the amyloid cascade hypothesis, a novel framework, the aging factor cascade hypothesis, is proposed in an attempt to integrate the new data and concepts that emerged from recent research to develop disease modifying therapies. PMID:23859546

  8. Extracellular Tau Oligomers Produce An Immediate Impairment of LTP and Memory.

    PubMed

    Fá, M; Puzzo, D; Piacentini, R; Staniszewski, A; Zhang, H; Baltrons, M A; Li Puma, D D; Chatterjee, I; Li, J; Saeed, F; Berman, H L; Ripoli, C; Gulisano, W; Gonzalez, J; Tian, H; Costa, J A; Lopez, P; Davidowitz, E; Yu, W H; Haroutunian, V; Brown, L M; Palmeri, A; Sigurdsson, E M; Duff, K E; Teich, A F; Honig, L S; Sierks, M; Moe, J G; D'Adamio, L; Grassi, C; Kanaan, N M; Fraser, P E; Arancio, O

    2016-01-01

    Non-fibrillar soluble oligomeric forms of amyloid-β peptide (oAβ) and tau proteins are likely to play a major role in Alzheimer's disease (AD). The prevailing hypothesis on the disease etiopathogenesis is that oAβ initiates tau pathology that slowly spreads throughout the medial temporal cortex and neocortices independently of Aβ, eventually leading to memory loss. Here we show that a brief exposure to extracellular recombinant human tau oligomers (oTau), but not monomers, produces an impairment of long-term potentiation (LTP) and memory, independent of the presence of high oAβ levels. The impairment is immediate as it raises as soon as 20 min after exposure to the oligomers. These effects are reproduced either by oTau extracted from AD human specimens, or naturally produced in mice overexpressing human tau. Finally, we found that oTau could also act in combination with oAβ to produce these effects, as sub-toxic doses of the two peptides combined lead to LTP and memory impairment. These findings provide a novel view of the effects of tau and Aβ on memory loss, offering new therapeutic opportunities in the therapy of AD and other neurodegenerative diseases associated with Aβ and tau pathology. PMID:26786552

  9. Ring-like oligomers of Synaptotagmins and related C2 domain proteins

    PubMed Central

    Zanetti, Maria N; Bello, Oscar D; Wang, Jing; Coleman, Jeff; Cai, Yiying; Sindelar, Charles V; Rothman, James E; Krishnakumar, Shyam S

    2016-01-01

    We recently reported that the C2AB portion of Synaptotagmin 1 (Syt1) could self-assemble into Ca2+-sensitive ring-like oligomers on membranes, which could potentially regulate neurotransmitter release. Here we report that analogous ring-like oligomers assemble from the C2AB domains of other Syt isoforms (Syt2, Syt7, Syt9) as well as related C2 domain containing protein, Doc2B and extended Synaptotagmins (E-Syts). Evidently, circular oligomerization is a general and conserved structural aspect of many C2 domain proteins, including Synaptotagmins. Further, using electron microscopy combined with targeted mutations, we show that under physiologically relevant conditions, both the Syt1 ring assembly and its rapid disruption by Ca2+ involve the well-established functional surfaces on the C2B domain that are important for synaptic transmission. Our data suggests that ring formation may be triggered at an early step in synaptic vesicle docking and positions Syt1 to synchronize neurotransmitter release to Ca2+ influx. DOI: http://dx.doi.org/10.7554/eLife.17262.001 PMID:27434670

  10. Nanoparticle for delivery of antisense γPNA oligomers targeting CCR5

    PubMed Central

    Bahal, Raman; McNeer, Nicole Ali; Ly, Danith H.; Saltzman, W. Mark; Glazer, Peter M.

    2013-01-01

    The development of a new class of peptide nucleic acids (PNAs), i.e., gamma PNAs (γPNAs), creates the need for a general and effective method for its delivery into cells for regulating gene expression in mammalian cells. Here we report the antisense activity of a recently developed hydrophilic and biocompatible diethylene glycol (miniPEG)-based gamma peptide nucleic acid called MPγPNAs via its delivery by poly(lactide-co-glycolide) (PLGA)-based nanoparticle system. We show that MPγPNA oligomers designed to bind to the selective region of Chemokine Receptor 5 (CCR5) transcript, induce potent and sequence-specific antisense effects as compared with regular PNA oligomers. In addition, PLGA nanoparticle delivery of MPγPNAs is not toxic to the cells. The findings reported in this study provide a combination of γPNA technology and PLGA-based nanoparticle delivery method for regulating gene expression in live cells via the antisense mechanism. PMID:23954968

  11. Synthesis of RNA oligomers on heterogeneous templates

    NASA Technical Reports Server (NTRS)

    Ertem, G.; Ferris, J. P.

    1996-01-01

    The concept of an RNA world in the chemical origin of life is appealing, as nucleic acids are capable of both information storage and acting as templates that catalyse the synthesis of complementary molecules. Template-directed synthesis has been demonstrated for homogeneous oligonucleotides that, like natural nucleic acids, have 3',5' linkages between the nucleotide monomers. But it seems likely that prebiotic routes to RNA-like molecules would have produced heterogeneous molecules with various kinds of phosphodiester linkages and both linear and cyclic nucleotide chains. Here we show that such heterogeneity need be no obstacle to the templating of complementary molecules. Specifically, we show that heterogeneous oligocytidylates, formed by the montmorillonite clay-catalysed condensation of actuated monomers, can serve as templates for the synthesis of oligoguanylates. Furthermore, we show that oligocytidylates that are exclusively 2',5'-linked can also direct synthesis of oligoguanylates. Such heterogeneous templating reactions could have increased the diversity of the pool of protonucleic acids from which life ultimately emerged.

  12. Pyridine-containing m-phenylene ethynylene oligomers having tunable basicities.

    PubMed

    Heemstra, Jennifer M; Moore, Jeffrey S

    2004-03-01

    Incorporation of a pyridine monomer into the backbone of a m-phenylene ethynylene oligomer allows functionalization of the interior binding cavity of the folded oligomer. The basicity of the inwardly directed pyridine moiety was modulated by changing the substituents on the pyridine ring and through oligomer folding, granting access to a pK(a) range of 5-14 in acetonitrile. [reaction: see text] PMID:14986943

  13. Case study on the evolution of hetero-oligomer interfaces based on the differences in paralogous proteins

    PubMed Central

    Aoto, Saki; Yura, Kei

    2015-01-01

    We addressed the evolutionary trace of hetero-oligomer interfaces by comparing the structures of paralogous proteins; one of them is a monomer or homo-oligomer and the other is a hetero-oligomer. We found different trends in amino acid conservation pattern and hydrophobicity between homo-oligomer and hetero-oligomer. The degree of amino acid conservation in the interface of homo-oligomer has no obvious difference from that in the surface, whereas the degree of conservation is much higher in the interface of hetero-oligomer. The interface of homo-oligomer has a few very conserved residue positions, whereas the residue conservation in the interface of hetero-oligomer tends to be higher. In addition, the interface of hetero-oligomer has a tendency of being more hydrophobic compared with the one in homo-oligomer. We conjecture that these differences are related to the inherent symmetry in homo-oligomers that cannot exist in hetero-oligomers. Paucity of the structural data precludes statistical tests of these tendencies, yet the trend can be applied to the prediction of the interface of hetero-oligomer. We obtained putative interfaces of the subunits in CPSF (cleavage and polyadenylation specificity factor), one of the human pre-mRNA 3′-processing complexes. The locations of predicted interface residues were consistent with the known experimental data. PMID:27493859

  14. Quantitative analysis of co-oligomer formation by amyloid-beta peptide isoforms

    NASA Astrophysics Data System (ADS)

    Iljina, Marija; Garcia, Gonzalo A.; Dear, Alexander J.; Flint, Jennie; Narayan, Priyanka; Michaels, Thomas C. T.; Dobson, Christopher M.; Frenkel, Daan; Knowles, Tuomas P. J.; Klenerman, David

    2016-06-01

    Multiple isoforms of aggregation-prone proteins are present under physiological conditions and have the propensity to assemble into co-oligomers with different properties from self-oligomers, but this process has not been quantitatively studied to date. We have investigated the amyloid-β (Aβ) peptide, associated with Alzheimer’s disease, and the aggregation of its two major isoforms, Aβ40 and Aβ42, using a statistical mechanical modelling approach in combination with in vitro single-molecule fluorescence measurements. We find that at low concentrations of Aβ, corresponding to its physiological abundance, there is little free energy penalty in forming co-oligomers, suggesting that the formation of both self-oligomers and co-oligomers is possible under these conditions. Our model is used to predict the oligomer concentration and size at physiological concentrations of Aβ and suggests the mechanisms by which the ratio of Aβ42 to Aβ40 can affect cell toxicity. An increased ratio of Aβ42 to Aβ40 raises the fraction of oligomers containing Aβ42, which can increase the hydrophobicity of the oligomers and thus promote deleterious binding to the cell membrane and increase neuronal damage. Our results suggest that co-oligomers are a common form of aggregate when Aβ isoforms are present in solution and may potentially play a significant role in Alzheimer’s disease.

  15. Quantitative analysis of co-oligomer formation by amyloid-beta peptide isoforms

    PubMed Central

    Iljina, Marija; Garcia, Gonzalo A.; Dear, Alexander J.; Flint, Jennie; Narayan, Priyanka; Michaels, Thomas C. T.; Dobson, Christopher M.; Frenkel, Daan; Knowles, Tuomas P. J.; Klenerman, David

    2016-01-01

    Multiple isoforms of aggregation-prone proteins are present under physiological conditions and have the propensity to assemble into co-oligomers with different properties from self-oligomers, but this process has not been quantitatively studied to date. We have investigated the amyloid-β (Aβ) peptide, associated with Alzheimer’s disease, and the aggregation of its two major isoforms, Aβ40 and Aβ42, using a statistical mechanical modelling approach in combination with in vitro single-molecule fluorescence measurements. We find that at low concentrations of Aβ, corresponding to its physiological abundance, there is little free energy penalty in forming co-oligomers, suggesting that the formation of both self-oligomers and co-oligomers is possible under these conditions. Our model is used to predict the oligomer concentration and size at physiological concentrations of Aβ and suggests the mechanisms by which the ratio of Aβ42 to Aβ40 can affect cell toxicity. An increased ratio of Aβ42 to Aβ40 raises the fraction of oligomers containing Aβ42, which can increase the hydrophobicity of the oligomers and thus promote deleterious binding to the cell membrane and increase neuronal damage. Our results suggest that co-oligomers are a common form of aggregate when Aβ isoforms are present in solution and may potentially play a significant role in Alzheimer’s disease. PMID:27346247

  16. Quantitative analysis of co-oligomer formation by amyloid-beta peptide isoforms.

    PubMed

    Iljina, Marija; Garcia, Gonzalo A; Dear, Alexander J; Flint, Jennie; Narayan, Priyanka; Michaels, Thomas C T; Dobson, Christopher M; Frenkel, Daan; Knowles, Tuomas P J; Klenerman, David

    2016-01-01

    Multiple isoforms of aggregation-prone proteins are present under physiological conditions and have the propensity to assemble into co-oligomers with different properties from self-oligomers, but this process has not been quantitatively studied to date. We have investigated the amyloid-β (Aβ) peptide, associated with Alzheimer's disease, and the aggregation of its two major isoforms, Aβ40 and Aβ42, using a statistical mechanical modelling approach in combination with in vitro single-molecule fluorescence measurements. We find that at low concentrations of Aβ, corresponding to its physiological abundance, there is little free energy penalty in forming co-oligomers, suggesting that the formation of both self-oligomers and co-oligomers is possible under these conditions. Our model is used to predict the oligomer concentration and size at physiological concentrations of Aβ and suggests the mechanisms by which the ratio of Aβ42 to Aβ40 can affect cell toxicity. An increased ratio of Aβ42 to Aβ40 raises the fraction of oligomers containing Aβ42, which can increase the hydrophobicity of the oligomers and thus promote deleterious binding to the cell membrane and increase neuronal damage. Our results suggest that co-oligomers are a common form of aggregate when Aβ isoforms are present in solution and may potentially play a significant role in Alzheimer's disease. PMID:27346247

  17. In vitro synthesis and purification of PhIP-deoxyguanosine and PhIP-DNA oligomer covalent complexes

    SciTech Connect

    Freeman, J.

    1994-12-01

    2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a heterocyclic amine compound formed when meats are cooked at high temperatures. PhIP damages DNA by forming covalent complexes with DNA carcinogen. In an effort to understand how the binding of PhIP to DNA may cause cancer, it is important to characterize the structures of PhIP-damaged DNA molecules. Our HPLC data support fluorescence and {sup 32}P Post-labeling studies which indicate the formation of several species of 2{prime}deoxyguanosine-(dG) or oligodeoxynucleotide-PhIP adducts. The reaction of PhIP with dG resulted in a reddish precipitate that was likely the major adduct, N-(deoxyguanosin-8-yl)-PhIP (dG-C8-PhIP) adduct, with a more polar adduct fraction remaining in the supernatant. Reversed-phase HPLC analysis of the adducts in the supernatant revealed the existence of species of much shorter retention times than the dG-C8-PhIP adduct, confirming that these species are more polar than dG-C8-PhIP. At least four adducts were formed in the reaction of PhIP with DNA oligomer. HPLC analysis of the PhIP-DNA oligomer supernatant after butanol extractions revealed four unresolved peaks which spectra had maximum wavelengths between 340 and 360 nm. Though adduct peaks were not completely resolved, there was {approximately}3 minutes interval between the DNA oligomer peak and the adduct peaks. Furthermore, fluorescence emission data of the DNA oligomer-PhIP adduct solution show heterogeneous binding. The more polar PhIP adducts were fraction-collected and their structures will be solved by nuclear magnetic resonance or x-ray crystallography.

  18. Induction of TNF-alpha production from human peripheral blood monocytes with beta-1,3-glucan oligomer prepared from laminarin with beta-1,3-glucanase from Bacillus clausii NM-1.

    PubMed

    Miyanishi, Nobumitsu; Iwamoto, Yoshiko; Watanabe, Etsuo; Odaz, Tatsuya

    2003-01-01

    We prepared a beta-1,3-glucan oligomer (DP> or = 4) from laminarin (DP: 25-30) derived from Laminaria digitata with beta-1,3-glucanase, and examined its effect on human peripheral blood monocytes. Conditioned medium prepared by incubating monocytes (MC-CM) with the beta-1,3-glucan oligomer showed strong inhibitory activity against the proliferation of human leukemic U937 cells. Since the beta-1,3-glucan oligomer had no direct cytotoxic effect on U937 cells up to 1000 microg/ml, the cytotoxicity of the MC-CM may be due to cytotoxic cytokines produced from monocytes stimulated by the beta-1,3-glucan oligomer. On the other hand, the MC-CM prepared with original laminarin had little effect on the growth of U937 cells. The cytotoxicity of the MC-CM prepared with the beta-1,3-glucan oligomer was significantly reduced by an anti-TNF-alpha antibody, but the anti-TNF-beta antibody had no effect. Our results suggest that the enzymatically depolymerized beta-1,3-glucan oligomer induces TNF-alpha production from human monocytes. PMID:16233391

  19. Disrupting self-assembly and toxicity of amyloidogenic protein oligomers by "molecular tweezers" - from the test tube to animal models.

    PubMed

    Attar, Aida; Bitan, Gal

    2014-01-01

    Despite decades of research, therapy for diseases caused by abnormal protein folding and aggregation (amyloidoses) is limited to treatment of symptoms and provides only temporary and moderate relief to sufferers. The failure in developing successful disease-modifying drugs for amyloidoses stems from the nature of the targets for such drugs - primarily oligomers of amyloidogenic proteins, which are distinct from traditional targets, such as enzymes or receptors. The oligomers are metastable, do not have well-defined structures, and exist in dynamically changing mixtures. Therefore, inhibiting the formation and toxicity of these oligomers likely will require out-of-the-box thinking and novel strategies. We review here the development of a strategy based on targeting the combination of hydrophobic and electrostatic interactions that are key to the assembly and toxicity of amyloidogenic proteins using lysine (K)-specific "molecular tweezers" (MTs). Our discussion includes a survey of the literature demonstrating the important role of K residues in the assembly and toxicity of amyloidogenic proteins and the development of a lead MT derivative called CLR01, from an inhibitor of protein aggregation in vitro to a drug candidate showing effective amelioration of disease symptoms in animal models of Alzheimer's and Parkinson's diseases. PMID:23859557

  20. Structure of Yin Yang 1 Oligomers That Cooperate with RuvBL1-RuvBL2 ATPases*

    PubMed Central

    López-Perrote, Andrés; Alatwi, Hanan E.; Torreira, Eva; Ismail, Amani; Ayora, Silvia; Downs, Jessica A.; Llorca, Oscar

    2014-01-01

    Yin Yang 1 (YY1) is a transcription factor regulating proliferation and differentiation and is involved in cancer development. Oligomers of recombinant YY1 have been observed before, but their structure and DNA binding properties are not well understood. Here we find that YY1 assembles several homo-oligomeric species built from the association of a bell-shaped dimer, a process we characterized by electron microscopy. Moreover, we find that YY1 self-association also occurs in vivo using bimolecular fluorescence complementation. Unexpectedly, these oligomers recognize several DNA substrates without the consensus sequence for YY1 in vitro, and DNA binding is enhanced in the presence of RuvBL1-RuvBL2, two essential AAA+ ATPases. YY1 oligomers bind RuvBL1-RuvBL2 hetero-oligomeric complexes, but YY1 interacts preferentially with RuvBL1. Collectively, these findings suggest that YY1-RuvBL1-RuvBL2 complexes could contribute to functions beyond transcription, and we show that YY1 and the ATPase activity of RuvBL2 are required for RAD51 foci formation during homologous recombination. PMID:24990942

  1. Towards vast libraries of scaffold-diverse, conformationally constrained oligomers.

    PubMed

    Kodadek, Thomas; McEnaney, Patrick J

    2016-05-01

    There is great interest in the development of probe molecules and drug leads that would bind tightly and selectively to protein surfaces that are difficult to target with traditional molecules, such as those involved in protein-protein interactions. The currently available evidence suggests that this will require molecules that are larger and have quite different chemical properties than typical Lipinski-compliant molecules that target enzyme active sites. We describe here efforts to develop vast libraries of conformationally constrained oligomers as a potentially rich source of these molecules. PMID:26996593

  2. Rare Individual Amyloid-β Oligomers Act on Astrocytes to Initiate Neuronal Damage

    PubMed Central

    2014-01-01

    Oligomers of the amyloid-β (Aβ) peptide have been implicated in the neurotoxicity associated with Alzheimer’s disease. We have used single-molecule techniques to examine quantitatively the cellular effects of adding well characterized Aβ oligomers to primary hippocampal cells and hence determine the initial pathway of damage. We found that even picomolar concentrations of Aβ (1–40) and Aβ (1–42) oligomers can, within minutes of addition, increase the levels of intracellular calcium in astrocytes but not in neurons, and this effect is saturated at a concentration of about 10 nM of oligomers. Both Aβ (1–40) and Aβ (1–42) oligomers have comparable effects. The rise in intracellular calcium is followed by an increase in the rate of ROS production by NADPH oxidase in both neurons and astrocytes. The increase in ROS production then triggers caspase-3 activation resulting in the inhibition of long-term potentiation. Our quantitative approach also reveals that only a small fraction of the oligomers are damaging and that an individual rare oligomer binding to an astrocyte can initiate the aforementioned cascade of responses, making it unlikely to be due to any specific interaction. Preincubating the Aβ oligomers with an extracellular chaperone, clusterin, sequesters the oligomers in long-lived complexes and inhibits all of the physiological damage, even at a ratio of 100:1, total Aβ to clusterin. To explain how Aβ oligomers are so damaging but that it takes decades to develop Alzheimer’s disease, we suggest a model for disease progression where small amounts of neuronal damage from individual unsequestered oligomers can accumulate over time leading to widespread tissue-level dysfunction. PMID:24717093

  3. Long-term electromagnetic pulse exposure induces Abeta deposition and cognitive dysfunction through oxidative stress and overexpression of APP and BACE1.

    PubMed

    Jiang, Da-Peng; Li, Jin-Hui; Zhang, Jie; Xu, Sheng-Long; Kuang, Fang; Lang, Hai-Yang; Wang, Ya-Feng; An, Guang-Zhou; Li, Jing; Guo, Guo-Zhen

    2016-07-01

    A progressively expanded literature has been devoted in the past years to the noxious or beneficial effects of electromagnetic field (EMF) to Alzheimer׳s disease (AD). This study concerns the relationship between electromagnetic pulse (EMP) exposure and the occurrence of AD in rats and the underlying mechanisms, focusing on the role of oxidative stress (OS). 55 healthy male Sprague Dawley (SD) rats were used and received continuous exposure for 8 months. Morris water maze (MWM) test was conducted to test the ability of cognitive and memory. The level of OS was detected by superoxide dismutase (SOD) activity and glutathione (GSH) content. We found that long-term EMP exposure induced cognitive damage in rats. The content of β-amyloid (Aβ) protein in hippocampus was increased after long-term EMP exposure. OS of hippocampal neuron was detected. Western blotting and immunohistochemistry (IHC) assay showed that the content of Aβ protein and its oligomers in EMP-exposed rats were higher than that of sham-exposed rats. The content of Beta Site App Cleaving Enzyme (BACE1) and microtubule-associated protein 1 light chain 3-II (LC3-II) in EMP-exposed rats hippocampus were also higher than that of sham-exposed rats. SOD activity and GSH content in EMP-exposed rats were lower than sham-exposed rats (p<0.05). Several mechanisms were proposed based on EMP exposure-induced OS, including increased amyloid precursor protein (APP) aberrant cleavage. Although further study is needed, the present results suggest that long-term EMP exposure is harmful to cognitive ability in rats and could induce AD-like pathological manifestation. PMID:26972535

  4. Polycaprolactone/oligomer compound scaffolds for cardiac tissue engineering.

    PubMed

    Reddy, Chaganti Srinivasa; Venugopal, Jayarama Reddy; Ramakrishna, Seeram; Zussman, Eyal

    2014-10-01

    Polycaprolactone (PCL), a synthetic biocompatible and biodegradable polymer generally used as a scaffold material for tissue engineering applications. The high stiffness and hydrophobicity of the PCL fiber mesh does not provide significant cell attachment and proliferation in cardiac tissue engineering. Towards this goal, the study focused on a compound of PCL and oligomer hydrogel [Bisphenol A ethoxylated dimethacrylate (BPAEDMA)] processed into electrospun nanofibrous scaffolds. The composition, morphology and mechanical properties of the compound scaffolds, composed of varying ratios of PCL and hydrogel were characterized by scanning electron microscopy, infrared spectroscopy and dynamic mechanical analyzer. The elastic modulus of PCL/BPAEDMA nanofibrous scaffolds was shown to be varying the BPAEDMA weight fraction and was decreased by increasing the BPAEDMA weight fraction. Compound fiber meshes containing 75 wt % BPAEDMA oligomer hydrogel exhibited lower modulus (3.55 MPa) and contact angle of 25(o) . Rabbit cardiac cells cultured for 10 days on these PCL/BPAEDMA compound nanofibrous scaffolds remained viable and expressed cardiac troponin and alpha-actinin proteins for the normal functioning of myocardium. Cell adhesion and proliferations were significantly increased on compound fiber meshes containing 75 wt % BPAEDMA, when compared with other nanofibrous scaffolds. The results observed that the produced PCL/BPAEDMA compound nanofibrous scaffolds promote cell adhesion, proliferation and normal functioning of cardiac cells to clinically beneficial levels, relevant for cardiac tissue engineering. PMID:24288184

  5. Amyloid oligomer structure characterization from simulations: A general method

    SciTech Connect

    Nguyen, Phuong H.; Li, Mai Suan

    2014-03-07

    Amyloid oligomers and plaques are composed of multiple chemically identical proteins. Therefore, one of the first fundamental problems in the characterization of structures from simulations is the treatment of the degeneracy, i.e., the permutation of the molecules. Second, the intramolecular and intermolecular degrees of freedom of the various molecules must be taken into account. Currently, the well-known dihedral principal component analysis method only considers the intramolecular degrees of freedom, and other methods employing collective variables can only describe intermolecular degrees of freedom at the global level. With this in mind, we propose a general method that identifies all the structures accurately. The basis idea is that the intramolecular and intermolecular states are described in terms of combinations of single-molecule and double-molecule states, respectively, and the overall structures of oligomers are the product basis of the intramolecular and intermolecular states. This way, the degeneracy is automatically avoided. The method is illustrated on the conformational ensemble of the tetramer of the Alzheimer's peptide Aβ{sub 9−40}, resulting from two atomistic molecular dynamics simulations in explicit solvent, each of 200 ns, starting from two distinct structures.

  6. CHIP targets toxic alpha-Synuclein oligomers for degradation.

    PubMed

    Tetzlaff, Julie E; Putcha, Preeti; Outeiro, Tiago F; Ivanov, Alexander; Berezovska, Oksana; Hyman, Bradley T; McLean, Pamela J

    2008-06-27

    alpha-Synuclein (alphaSyn) can self-associate, forming oligomers, fibrils, and Lewy bodies, the pathological hallmark of Parkinson disease. Current dogma suggests that oligomeric alphaSyn intermediates may represent the most toxic alphaSyn species. Here, we studied the effect of a potent molecular chaperone, CHIP (carboxyl terminus of Hsp70-interacting protein), on alphaSyn oligomerization using a novel bimolecular fluorescence complementation assay. CHIP is a multidomain chaperone, utilizing both a tetratricopeptide/Hsp70 binding domain and a U-box/ubiquitin ligase domain to differentially impact the fate of misfolded proteins. In the current study, we found that co-expression of CHIP selectively reduced alphaSyn oligomerization and toxicity in a tetratricopeptide domain-dependent, U-box-independent manner by specifically degrading toxic alphaSyn oligomers. We conclude that CHIP preferentially recognizes and mediates degradation of toxic, oligomeric forms of alphaSyn. Further elucidation of the mechanisms of CHIP-induced degradation of oligomeric alphaSyn may contribute to the successful development of drug therapies that target oligomeric alphaSyn by mimicking or enhancing the powerful effects of CHIP. PMID:18436529

  7. EGFP oligomers as natural fluorescence and hydrodynamic standards.

    PubMed

    Vámosi, György; Mücke, Norbert; Müller, Gabriele; Krieger, Jan Wolfgang; Curth, Ute; Langowski, Jörg; Tóth, Katalin

    2016-01-01

    EGFP oligomers are convenient standards for experiments on fluorescent protein-tagged biomolecules. In this study, we characterized their hydrodynamic and fluorescence properties. Diffusion coefficients D of EGFP1-4 were determined by analytical ultracentrifugation with fluorescence detection and by fluorescence correlation spectroscopy (FCS), yielding 83.4…48.2 μm(2)/s and 97.3…54.8 μm(2)/s from monomer to tetramer. A "barrels standing in a row" model agreed best with the sedimentation data. Oligomerization red-shifted EGFP emission spectra without any shift in absorption. Fluorescence anisotropy decreased, indicating homoFRET between the subunits. Fluorescence lifetime decreased only slightly (4%) indicating insignificant quenching by FRET to subunits in non-emitting states. FCS-measured D, particle number and molecular brightness depended on dark states and light-induced processes in distinct subunits, resulting in a dependence on illumination power different for monomers and oligomers. Since subunits may be in "on" (bright) or "off" (dark) states, FCS-determined apparent brightness is not proportional to that of the monomer. From its dependence on the number of subunits, the probability of the "on" state for a subunit was determined to be 96% at pH 8 and 77% at pH 6.38, i.e., protonation increases the dark state. These fluorescence properties of EGFP oligomeric standards can assist interpreting results from oligomerized EGFP fusion proteins of biological interest. PMID:27622431

  8. In vivo resolution of oligomers with fluorescence photobleaching recovery histograms

    PubMed Central

    Youn, B.S.; Lepock, J.R.; Borrelli, M.J.; Jervis, E.J.

    2006-01-01

    Simple independent enzyme-catalyzed reactions distributed homogeneously throughout an aqueous environment cannot adequately explain the regulation of metabolic and other cellular processes in vivo. Such an unstructured system results in unacceptably slow substrate turnover rates and consumes inordinate amounts of cellular energy. Current approaches to resolving compartmentalization in living cells requires the partitioning of the molecular species in question such that its localization can be resolved with fluorescence microscopy. Standard imaging approaches will not resolve localization of protein activity for proteins that are ubiquitously distributed, but whose function requires a change in state of the protein. The small heat shock protein sHSP27 exists as both dimers and large multimers and is distributed homogeneously throughout the cytoplasm. A fusion of the green fluorescent protein variant S65T and sHSP27 is used to assess the ability of diffusion rate histograms to resolve compartmentalization of the 2 dominant oligomeric species of sHSP27. Diffusion rates were measured by multiphoton fluorescence photobleaching recovery. Under physiologic conditions, diffusion rate histograms resolved at least 2 diffusive transport rates within a living cell potentially corresponding to the large and small oligomers of sHSP27. Given that oligomerization is often a means of regulation, compartmentalization of different oligomer species could provide a means for efficient regulation and localization of sHsp27 activity. PMID:16817323

  9. How Epigallocatechin Gallate Can Inhibit α-Synuclein Oligomer Toxicity in Vitro♦

    PubMed Central

    Lorenzen, Nikolai; Nielsen, Søren B.; Yoshimura, Yuichi; Vad, Brian S.; Andersen, Camilla Bertel; Betzer, Cristine; Kaspersen, Jørn D.; Christiansen, Gunna; Pedersen, Jan S.; Jensen, Poul Henning; Mulder, Frans A. A.; Otzen, Daniel E.

    2014-01-01

    Oligomeric species of various proteins are linked to the pathogenesis of different neurodegenerative disorders. Consequently, there is intense focus on the discovery of novel inhibitors, e.g. small molecules and antibodies, to inhibit the formation and block the toxicity of oligomers. In Parkinson disease, the protein α-synuclein (αSN) forms cytotoxic oligomers. The flavonoid epigallocatechin gallate (EGCG) has previously been shown to redirect the aggregation of αSN monomers and remodel αSN amyloid fibrils into disordered oligomers. Here, we dissect EGCG's mechanism of action. EGCG inhibits the ability of preformed oligomers to permeabilize vesicles and induce cytotoxicity in a rat brain cell line. However, EGCG does not affect oligomer size distribution or secondary structure. Rather, EGCG immobilizes the C-terminal region and moderately reduces the degree of binding of oligomers to membranes. We interpret our data to mean that the oligomer acts by destabilizing the membrane rather than by direct pore formation. This suggests that reduction (but not complete abolition) of the membrane affinity of the oligomer is sufficient to prevent cytotoxicity. PMID:24907278

  10. β-to-β 2,5-Pyrrolylene-Linked Cyclic Porphyrin Oligomers.

    PubMed

    Rao, Yutao; Kim, Jun Oh; Kim, Woojae; Zhong, Guangming; Yin, Bangshao; Zhou, Mingbo; Shinokubo, Hiroshi; Aratani, Naoki; Tanaka, Takayuki; Liu, Shubin; Osuka, Atsuhiro; Kim, Dongho; Song, Jianxin

    2016-06-20

    β-to-β 2,5-Pyrrolylene linked cyclic porphyrin oligomers have been synthesized by Suzuki-Miyaura coupling of 2,5-diborylpyrrole and 3,7-dibromoporphyrin. The cyclic porphyrin oligomers exhibit roughly coplanar structures, strong excitonic coupling, small electrochemical HOMO-LUMO gaps, and ultrafast excitation energy transfer between the neighboring porphyrins via the pyrrolylene bridge. PMID:27124728

  11. Fibrillogenic oligomers of human cystatin C are formed by propagated domain swapping.

    PubMed

    Wahlbom, Maria; Wang, Xin; Lindström, Veronica; Carlemalm, Eric; Jaskolski, Mariusz; Grubb, Anders

    2007-06-22

    Cystatin C and the prion protein have been shown to form dimers via three-dimensional domain swapping, and this process has also been hypothesized to be involved in amyloidogenesis. Production of oligomers of other amyloidogenic proteins has been reported to precede fibril formation, suggesting oligomers as intermediates in fibrillogenesis. A variant of cystatin C, with a Leu68-->Gln substitution, is highly amyloidogenic, and carriers of this mutation suffer from massive cerebral amyloidosis leading to brain hemorrhage and death in early adulthood. This work describes doughnut-shaped oligomers formed by wild type and L68Q cystatin C upon incubation of the monomeric proteins. Purified oligomers of cystatin C are shown to fibrillize faster and at a lower concentration than the monomeric protein, indicating a role of the oligomers as fibril-assembly intermediates. Moreover, the present work demonstrates that three-dimensional domain swapping is involved in the formation of the oligomers, because variants of monomeric cystatin C, stabilized against three-dimensional domain swapping by engineered disulfide bonds, do not produce oligomers upon incubation under non-reducing conditions. Redox experiments using wild type and stabilized cystatin C strongly suggest that the oligomers, and thus probably the fibrils as well, are formed by propagated domain swapping rather than by assembly of domain-swapped cystatin C dimers. PMID:17470433

  12. The Mechanism of Membrane Disruption by Cytotoxic Amyloid Oligomers Formed by Prion Protein(106–126) Is Dependent on Bilayer Composition*

    PubMed Central

    Walsh, Patrick; Vanderlee, Gillian; Yau, Jason; Campeau, Jody; Sim, Valerie L.; Yip, Christopher M.; Sharpe, Simon

    2014-01-01

    The formation of fibrillar aggregates has long been associated with neurodegenerative disorders such as Alzheimer and Parkinson diseases. Although fibrils are still considered important to the pathology of these disorders, it is now widely understood that smaller amyloid oligomers are the toxic entities along the misfolding pathway. One characteristic shared by the majority of amyloid oligomers is the ability to disrupt membranes, a commonality proposed to be responsible for their toxicity, although the mechanisms linking this to cell death are poorly understood. Here, we describe the physical basis for the cytotoxicity of oligomers formed by the prion protein (PrP)-derived amyloid peptide PrP(106–126). We show that oligomers of this peptide kill several mammalian cells lines, as well as mouse cerebellar organotypic cultures, and we also show that they exhibit antimicrobial activity. Physical perturbation of model membranes mimicking bacterial or mammalian cells was investigated using atomic force microscopy, polarized total internal reflection fluorescence microscopy, and NMR spectroscopy. Disruption of anionic membranes proceeds through a carpet or detergent model as proposed for other antimicrobial peptides. By contrast, when added to zwitterionic membranes containing cholesterol-rich ordered domains, PrP(106–126) oligomers induce a loss of domain separation and decreased membrane disorder. Loss of raft-like domains may lead to activation of apoptotic pathways, resulting in cell death. This work sheds new light on the physical mechanisms of amyloid cytotoxicity and is the first to clearly show membrane type-specific modes of action for a cytotoxic peptide. PMID:24554723

  13. Probing the Run-On Oligomer of Activated SgrAI Bound to DNA

    PubMed Central

    Shah, Santosh; Sanchez, Jonathan; Stewart, Andrew; Piperakis, Michael M.; Cosstick, Richard; Nichols, Claire; Park, Chad K.; Ma, Xin; Wysocki, Vicki; Bitinaite, Jurate; Horton, Nancy C.

    2015-01-01

    SgrAI is a type II restriction endonuclease with an unusual mechanism of activation involving run-on oligomerization. The run-on oligomer is formed from complexes of SgrAI bound to DNA containing its 8 bp primary recognition sequence (uncleaved or cleaved), and also binds (and thereby activates for DNA cleavage) complexes of SgrAI bound to secondary site DNA sequences which contain a single base substitution in either the 1st/8th or the 2nd/7th position of the primary recognition sequence. This modulation of enzyme activity via run-on oligomerization is a newly appreciated phenomenon that has been shown for a small but increasing number of enzymes. One outstanding question regarding the mechanistic model for SgrAI is whether or not the activating primary site DNA must be cleaved by SgrAI prior to inducing activation. Herein we show that an uncleavable primary site DNA containing a 3’-S-phosphorothiolate is in fact able to induce activation. In addition, we now show that cleavage of secondary site DNA can be activated to nearly the same degree as primary, provided a sufficient number of flanking base pairs are present. We also show differences in activation and cleavage of the two types of secondary site, and that effects of selected single site substitutions in SgrAI, as well as measured collisional cross-sections from previous work, are consistent with the cryo-electron microscopy model for the run-on activated oligomer of SgrAI bound to DNA. PMID:25880668

  14. Low molecular weight oligomers of amyloid peptides display β-barrel conformations: A replica exchange molecular dynamics study in explicit solvent

    NASA Astrophysics Data System (ADS)

    De Simone, Alfonso; Derreumaux, Philippe

    2010-04-01

    The self-assembly of proteins and peptides into amyloid fibrils is connected to over 40 pathological conditions including neurodegenerative diseases and systemic amyloidosis. Diffusible, low molecular weight protein and peptide oligomers that form in the early steps of aggregation appear to be the harmful cytotoxic species in the molecular etiology of these diseases. So far, the structural characterization of these oligomers has remained elusive owing to their transient and dynamic features. We here address, by means of full atomistic replica exchange molecular dynamics simulations, the energy landscape of heptamers of the amyloidogenic peptide NHVTLSQ from the beta-2 microglobulin protein. The simulations totaling 5 μs show that low molecular weight oligomers in explicit solvent consist of β-barrels in equilibrium with amorphous states and fibril-like assemblies. The results, also accounting for the influence of the pH on the conformational properties, provide a strong evidence of the formation of transient β-barrel assemblies in the early aggregation steps of amyloid-forming systems. Our findings are discussed in terms of oligomers cytotoxicity.

  15. Supramolecular aggregates with distinct optical properties from PDI oligomers of similar structures.

    PubMed

    Yan, Qifan; Cai, Kang; Zhao, Dahui

    2016-01-21

    The self-assembly behaviors of two series of monodispersed oligomers consisting of perylenediimide (PDI) linked by ethynylene and butadiynylene spacers are investigated in solutions. In spite of the very similar chemical structures, the two sets of oligomers manifest completely different optical properties upon self-aggregation, implying differed aggregate structures. While the oligomers containing butadiynylene spacers form H-aggregates, those featuring ethynylene linkers display J-aggregation characteristics. Thermodynamic analysis revealed that the self-association constants of both series of oligomers increase with the number of PDI units in the backbones. Oligomers containing the same number of PDI units but different spacers display nearly identical enthalpy changes. According to the molecular exciton theory, the observed H- and J-aggregates are suggested to comprise similar packing motifs with slightly varied slipping angles, giving rise to greatly disparate optical properties. PMID:26686554

  16. Preparation of Chito-Oligomers by Hydrolysis of Chitosan in the Presence of Zeolite as Adsorbent

    PubMed Central

    Ibrahim, Khalid A.; El-Eswed, Bassam I.; Abu-Sbeih, Khaleel A.; Arafat, Tawfeeq A.; Al Omari, Mahmoud M. H.; Darras, Fouad H.; Badwan, Adnan A.

    2016-01-01

    An increasing interest has recently been shown to use chitin/chitosan oligomers (chito-oligomers) in medicine and food fields because they are not only water-soluble, nontoxic, and biocompatible materials, but they also exhibit numerous biological properties, including antibacterial, antifungal, and antitumor activities, as well as immuno-enhancing effects on animals. Conventional depolymerization methods of chitosan to chito-oligomers are either chemical by acid-hydrolysis under harsh conditions or by enzymatic degradation. In this work, hydrolysis of chitosan to chito-oligomers has been achieved by applying adsorption-separation technique using diluted HCl in the presence of different types of zeolite as adsorbents. The chito-oligomers were retrieved from adsorbents and characterized by differential scanning calorimetry (DSC), liquid chromatography/mass spectroscopy (LC/MS), and ninhydrin test. PMID:27455287

  17. Star-shaped tetrathiafulvalene oligomers towards the construction of conducting supramolecular assembly

    PubMed Central

    Hasegawa, Masashi

    2015-01-01

    Summary The construction of redox-active supramolecular assemblies based on star-shaped and radially expanded tetrathiafulvalene (TTF) oligomers with divergent and extended conjugation is summarized. Star-shaped TTF oligomers easily self-aggregate with a nanophase separation to produce supramolecular structures, and their TTF units stack face-to-face to form columnar structures using the fastener effect. Based on redox-active self-organizing supramolecular structures, conducting nanoobjects are constructed by doping of TTF oligomers with oxidants after the formation of such nanostructures. Although radical cations derived from TTF oligomers strongly interact in solution to produce a mixed-valence dimer and π-dimer, it seems to be difficult to produce nanoobjects of radical cations different from those of neutral TTF oligomers. In some cases, however, radical cations form nanostructured fibers and rods by controlling the supramolecular assembly, oxidation states, and counter anions employed. PMID:26664579

  18. The Role of Amyloid-β Oligomers in Toxicity, Propagation, and Immunotherapy

    PubMed Central

    Sengupta, Urmi; Nilson, Ashley N.; Kayed, Rakez

    2016-01-01

    The incidence of Alzheimer's disease (AD) is growing every day and finding an effective treatment is becoming more vital. Amyloid-β (Aβ) has been the focus of research for several decades. The recent shift in the Aβ cascade hypothesis from all Aβ to small soluble oligomeric intermediates is directing the search for therapeutics towards the toxic mediators of the disease. Targeting the most toxic oligomers may prove to be an effective treatment by preventing their spread. Specific targeting of oligomers has been shown to protect cognition in rodent models. Additionally, the heterogeneity of research on Aβ oligomers may seem contradictory until size and conformation are taken into account. In this review, we will discuss Aβ oligomers and their toxicity in relation to size and conformation as well as their influence on inflammation and the potential of Aβ oligomer immunotherapy. PMID:27211547

  19. Preparation of Chito-Oligomers by Hydrolysis of Chitosan in the Presence of Zeolite as Adsorbent.

    PubMed

    Ibrahim, Khalid A; El-Eswed, Bassam I; Abu-Sbeih, Khaleel A; Arafat, Tawfeeq A; Al Omari, Mahmoud M H; Darras, Fouad H; Badwan, Adnan A

    2016-01-01

    An increasing interest has recently been shown to use chitin/chitosan oligomers (chito-oligomers) in medicine and food fields because they are not only water-soluble, nontoxic, and biocompatible materials, but they also exhibit numerous biological properties, including antibacterial, antifungal, and antitumor activities, as well as immuno-enhancing effects on animals. Conventional depolymerization methods of chitosan to chito-oligomers are either chemical by acid-hydrolysis under harsh conditions or by enzymatic degradation. In this work, hydrolysis of chitosan to chito-oligomers has been achieved by applying adsorption-separation technique using diluted HCl in the presence of different types of zeolite as adsorbents. The chito-oligomers were retrieved from adsorbents and characterized by differential scanning calorimetry (DSC), liquid chromatography/mass spectroscopy (LC/MS), and ninhydrin test. PMID:27455287

  20. On the effect of electron correlation on the static second hyperpolarizability of π conjugated oligomer chains.

    PubMed

    Limacher, Peter A; Li, Qingxu; Lüthi, Hans P

    2011-07-01

    In this article, we report on the ab initio calculation of the static longitudinal second hyperpolarizability (γ) of π conjugated unsaturated oligomer chains using polyacetylene and polyyne as model compounds. The common observation is that the electron correlation enhances γ in these systems. The present study reveals that for extended chain lengths the opposite appears to be true: Electron correlation may have a damping effect on this property. For double-zeta basis sets, a negative contribution from electron correlation to γ is found within the range of chain lengths investigated. For triple-zeta basis sets, the same behavior must be anticipated at larger chain lengths based on extrapolation schemes. The analysis of the excitation energies and transition moments shows that transition moments between excited states as predicted by the Hartree-Fock and coupled cluster methods have a different response to chain length extension. There also are indications that higher order correlation effects will enhance γ. PMID:21744892

  1. Structural properties of polystyrene oligomers in different environments: a molecular dynamics study.

    PubMed

    Bayramoglu, Beste; Faller, Roland

    2011-10-28

    We have performed detailed molecular dynamics simulations to investigate the effects of solvation and confinement on the structure of polystyrene (PS) oligomers in four different environments, melt, concentrated solution, dilute solution and confined concentrated solution at 450 K and 1 bar, respectively. Local packing of the monomers and the solvent (toluene, good solvent) molecules were monitored by means of radial distribution functions (RDFs). We have also investigated bond, angle, and dihedral angle distributions of the monomers. End-to-end distances, radii of gyration and persistence lengths were calculated to characterize the static properties. The chain in the dilute solution was found to exhibit more stretched conformations. Dilution effect of the solvent was observed in the RDFs between the monomer centers. Only slight conformational changes in the polymers were observed by solvation. The effect of confinement was mainly seen in the density profiles, which showed an oscillatory behavior in the confined system. PMID:21909555

  2. The Pilus Usher Controls Protein Interactions via Domain Masking and is Functional as an Oligomer

    PubMed Central

    Werneburg, Glenn T.; Henderson, Nadine S.; Portnoy, Erica B.; Sarowar, Samema; Hultgren, Scott J.; Li, Huilin; Thanassi, David G.

    2015-01-01

    The chaperone-usher (CU) pathway assembles organelles termed pili or fimbriae in Gram-negative bacteria. Type 1 pili expressed by uropathogenic Escherichia coli are prototypical structures assembled by the CU pathway. Biogenesis of pili by the CU pathway requires a periplasmic chaperone and an outer membrane protein termed the usher (FimD). We show that the FimD C-terminal domains provide the high-affinity substrate binding site, but that these domains are masked in the resting usher. Domain masking requires the FimD plug domain, which serves as a switch controlling usher activation. We demonstrate that usher molecules can act in trans for pilus biogenesis, providing conclusive evidence for a functional usher oligomer. These results reveal mechanisms by which molecular machines such as the usher regulate and harness protein-protein interactions, and suggest that ushers may interact in a cooperative manner during pilus assembly in bacteria. PMID:26052892

  3. Membrane-mediated interactions and the dynamics of dynamin oligomers on membrane tubes

    NASA Astrophysics Data System (ADS)

    Shlomovitz, R.; Gov, N. S.; Roux, A.

    2011-06-01

    Dynamin is a protein that plays a key role in the transport and recycling of membrane tubes and vesicles within a living cell. This protein adsorbs from solution to PIP2-containing membranes, and on these tubes it forms curved oligomers that condense into tight helical domains of uniform radius. The dynamics of this process is treated here in terms of the linear stability of a continuum model, whereby membrane-mediated interactions are shown to drive the spontaneous nucleation of condensed dynamin domains. We furthermore show that the deformation of the membrane outside the dynamin domains induces an energy barrier that can hinder the full coalescence of neighboring growing domains. We compare these calculations to experimental observations on dynamin dynamics in vitro.

  4. Investigation of ferroelectric domains in thin films of vinylidene fluoride oligomers

    SciTech Connect

    Sharma, Pankaj Poddar, Shashi; Ducharme, Stephen; Gruverman, Alexei; Korlacki, Rafal

    2014-07-14

    High-resolution vector piezoresponse force microscopy (PFM) has been used to investigate ferroelectric domains in thin vinylidene fluoride oligomer films fabricated by the Langmuir-Blodgett deposition technique. Molecular chains are found to be preferentially oriented normal to the substrate, and PFM imaging shows that the films are in ferroelectric β-phase with a predominantly in-plane polarization, in agreement with infrared spectroscopic ellipsometry and X-ray diffraction measurements. The fractal analysis of domain structure has yielded the Hausdorff dimension (D) in the range of ∼1.3–1.5 indicating a random-bond nature of the disorder potential, with domain size exhibiting Landau-Lifshitz-Kittel scaling.

  5. Anti-HIV-1 activity of a tripodal receptor that recognizes mannose oligomers.

    PubMed

    Rivero-Buceta, Eva; Carrero, Paula; Casanova, Elena; Doyagüez, Elisa G; Madrona, Andrés; Quesada, Ernesto; Peréz-Pérez, María Jesús; Mateos, Raquel; Bravo, Laura; Mathys, Leen; Noppen, Sam; Kiselev, Evgeny; Marchand, Christophe; Pommier, Yves; Liekens, Sandra; Balzarini, Jan; Camarasa, María José; San-Félix, Ana

    2015-12-01

    The glycoprotein gp120 of the HIV-1 viral envelope has a high content in mannose residues, particularly α-1,2-mannose oligomers. Compounds that interact with these high-mannose type glycans may disturb the interaction between gp120 and its (co)receptors and are considered potential anti-HIV agents. Previously, we demonstrated that a tripodal receptor (1), with a central scaffold of 1,3,5-triethylbenzene substituted with three 2,3,4-trihydroxybenzoyl groups, selectively recognizes α-1,2-mannose polysaccharides. Here we present additional studies to determine the anti-HIV-1 activity and the mechanism of antiviral activity of this compound. Our studies indicate that 1 shows anti-HIV-1 activity in the low micromolar range and has pronounced gp120 binding and HIV-1 integrase inhibitory capacity. However, gp120 binding rather than integrase inhibition seems to be the primary mechanism of antiviral activity of 1. PMID:26540494

  6. Vibrational properties of ferroelectric {beta}-vinylidene fluoride polymers and oligomers.

    SciTech Connect

    Nakhmanson, S. M.; Korlacki, R.; Johnson, J. T.; Ducharme, S.; Ge, Z.; Takacs, J. M.; Materials Science Division; Univ.of Nebraska at Lincoln

    2010-01-01

    We utilize a plane-wave density-functional theory approach to investigate the vibrational properties of the all-trans ferroelectric phase of poly(vinylidene fluoride) ({beta}-PVDF) showing that its stable state corresponds to the Ama2 structure with ordered dihedral tilting of the VDF monomers along the polymer chains. We then combine our theoretical analysis with IR spectroscopy to examine vibrations in oligomer crystals that are structurally related to the {beta}-PVDF phase. We demonstrate that these materials - which can be grown in a highly crystalline form - exhibit IR activity similar to that of {beta}-PVDF, making them an attractive choice for the studies of electroactive phenomena and phase transitions in polymer ferroelectrics.

  7. Oligomer-coated carbon nanotube chemiresistive sensors for selective detection of nitroaromatic explosives.

    PubMed

    Zhang, Yaqiong; Xu, Miao; Bunes, Benjamin R; Wu, Na; Gross, Dustin E; Moore, Jeffrey S; Zang, Ling

    2015-04-15

    High-performance chemiresistive sensors were made using a porous thin film of single-walled carbon nanotubes (CNTs) coated with a carbazolylethynylene (Tg-Car) oligomer for trace vapor detection of nitroaromatic explosives. The sensors detect low concentrations of 4-nitrotoluene (NT), 2,4,6-trinitrotoluene (TNT), and 2,4-dinitrotoluene (DNT) vapors at ppb to ppt levels. The sensors also show high selectivity to NT from other common organic reagents at significantly higher vapor concentrations. Furthermore, by using Tg-Car/CNT sensors and uncoated CNT sensors in parallel, differential sensing of NT, TNT, and DNT vapors was achieved. This work provides a methodology to create selective CNT-based sensors and sensor arrays. PMID:25823968

  8. In vivo determination of the structure of oligomers of a G protein-coupled receptor

    NASA Astrophysics Data System (ADS)

    Rath, Sasmita; Raicu, Valerica

    2009-03-01

    Resonance Energy Transfer (RET) is a process of nonradiative energy transfer between a donor and an acceptor molecule, which is widely used for studies of protein-protein interactions in living cells. Here we report on the results of a spectrally-resolved two-photon microscopy study of image pixel-level RET in yeast cells (S. cerevisiae) expressing a G-protein-coupled receptor called Sterile 2 α factor protein (Ste2P). The number of pixels showing RET were plotted against the RET efficiency to obtain distributions of RET efficiency in the cells. These distributions were simulated with models for plausible geometries and sizes of protein complexes (V. Raicu, 2007, J. Biol. Phys. 33:109--127). From all the models tested we found that a parallelogram-shaped tetramer is the most likely structure for the Ste2p oligomers.

  9. The molecular chaperone Brichos breaks the catalytic cycle that generates toxic Aβ oligomers

    PubMed Central

    Kurudenkandy, Firoz Roshan; Biverstal, Henrik; Dolfe, Lisa; Dunning, Christopher; Yang, Xiaoting; Frohm, Birgitta; Vendruscolo, Michele; Johansson, Jan; Dobson, Christopher M.; Fisahn, André; Knowles, Tuomas P. J.; Linse, Sara

    2015-01-01

    Alzheimer’s disease is an increasingly prevalent neurodegenerative disorder whose pathogenesis has been associated with aggregation of the amyloid-β peptide (Aβ42). Recent studies have revealed that once Aβ42 fibrils are generated, their surfaces strongly catalyse the formation of neurotoxic oligomers. Here we show that a molecular chaperone, a Brichos domain, can specifically inhibit this catalytic cycle and limit Aβ42 toxicity. We demonstrate in vitro that Brichos achieves this inhibition by binding to the surfaces of fibrils, thereby redirecting the aggregation reaction to a pathway that involves minimal formation of toxic oligomeric intermediates. We verify that this mechanism occurs in living brain tissue by means of cytotoxicity and electrophysiology experiments. These results reveal that molecular chaperones can help maintain protein homeostasis by selectively suppressing critical microscopic steps within the complex reaction pathways responsible for the toxic effects of protein misfolding and aggregation. PMID:25686087

  10. Understanding amyloid fibril nucleation and aβ oligomer/drug interactions from computer simulations.

    PubMed

    Nguyen, Phuong; Derreumaux, Philippe

    2014-02-18

    Evolution has fine-tuned proteins to accomplish a variety of tasks. Yet, with aging, some proteins assemble into harmful amyloid aggregates associated with neurodegenerative diseases, such as Alzheimer's disease (AD), which presents a complex and costly challenge to our society. Thus, far, drug after drug has failed to slow the progression of AD, characterized by the self-assembly of the 39-43 amino acid β-amyloid (Aβ) protein into extracellular senile plaques that form a cross-β structure. While there is experimental evidence that the Aβ small oligomers are the primary toxic species, standard tools of biology have failed to provide structures of these transient, inhomogeneous assemblies. Despite extensive experimental studies, researchers have not successfully characterized the nucleus ensemble, the starting point for rapid fibril formation. Similarly scientists do not have atomic data to show how the compounds that reduce both fibril formation and toxicity in cells bind to Aβ42 oligomers. In this context, computer simulations are important tools for gaining insights into the self-assembly of amyloid peptides and the molecular mechanism of inhibitors. This Account reviews what analytical models and simulations at different time and length scales tell us about the dynamics, kinetics, and thermodynamics of amyloid fibril formation and, notably, the nucleation process. Though coarse-grained and mesoscopic protein models approximate atomistic details by averaging out unimportant degrees of freedom, they provide generic features of amyloid formation and insights into mechanistic details of the self-assembly process. The thermodynamics and kinetics vary from linear peptides adopting straight β-strands in fibrils to longer peptides adopting in parallel U shaped conformations in fibrils. In addition, these properties change with the balance between electrostatic and hydrophobic interactions and the intrinsic disorder of the system. However, simulations suggest that

  11. Structural Characteristics of the Alpha-Synuclein Oligomers Stabilized By the Flavonoid Baicalein

    SciTech Connect

    Hong, D.-P.; Fink, A.L.; Uversky, V.N.

    2009-05-18

    The flavonoid baicalein inhibits fibrillation of alpha-synuclein, which is a major component of Lewy bodies in Parkinson's disease. It has been known that baicalein induces the formation of alpha-synuclein oligomers and consequently prevents their fibrillation. In order to evaluate the structural properties of baicalein-stabilized oligomers, we purified oligomer species by HPLC and examined their stability and structure by CD, Fourier transform infrared spectroscopy, size exclusion chromatography HPLC, small-angle X-ray scattering, and atomic force microscopy. Baicalein-stabilized oligomers are beta-sheet-enriched according to CD and Fourier transform infrared spectroscopy analyses. They did not form fibrils even after very prolonged incubation. From small-angle X-ray scattering data and atomic force microscopy images, the oligomers were characterized as quite compact globular species. Oligomers were extremely stable, with a GdmCl C(m)=3.3 M. This high stability explains the previously observed inhibition properties of baicalein against alpha-synuclein fibrillation. These baicalein-stabilized oligomers, added to the solution of aggregating alpha-synuclein, were able to noticeably inhibit its fibrillation. After prolonged coincubation, short fibrils were formed, suggesting an effective interaction of oligomers with monomeric alpha-synuclein. Membrane permeability tests suggested that the baicalein-stabilized oligomers had a mild effect on the integrity of the membrane surface. This effect was rather similar to that of the monomeric protein, suggesting that targeted stabilization of certain alpha-synuclein oligomers might offer a potential strategy for the development of novel Parkinson's disease therapies.

  12. Conformation of chromatin oligomers. A new argument for a change with the hexanucleosome.

    PubMed

    Marion, C; Bezot, P; Hesse-Bezot, C; Roux, B; Bernengo, J C

    1981-11-01

    Quasielastic laser light scattering measurements have been made on chromatin oligomers to obtain information on the transition in their electrooptical properties, previously observed for the hexameric structures [Marion, C. and Roux, B. (1978) Nucleic Acids Res. 5, 4431-4449]. Translational diffusion coefficients were determined for mononucleosomes to octanucleosomes containing histone H1 over a range of ionic strength. At high ionic strength, oligomers show a linear dependence of the logarithm of diffusion coefficient upon the logarithm of number of nucleosomes. At low ionic strength a change occurs between hexamer and heptamer. Our results agree well with the recent sedimentation data of Osipova et al. [Eur. J. Biochem. (1980) 113, 183-188] and of Butler and Thomas [J. Mol. Biol. (1980) 140, 505-529] showing a change in stability with hexamer. Various models for the arrangements of nucleosomes in the superstructure of chromatin are discussed. All calculations clearly indicate a conformational change with the hexanucleosome and the results suggest that, at low ionic strength, the chromatin adopts a loosely helical structure of 28-nm diameter and 22-nm pitch. These results are also consistent with a discontinuity every sixth nucleosome, corresponding to a turn of the helix. This discontinuity may explain the recent electric dichroism data of Lee et al. [Biochemistry (1981) 20, 1438-1445]. The hexanucleosome structure which we have previously suggested, with the faces of nucleosomes arranged radially to the helical axis has been recently confirmed by Mc Ghee et al. [Cell (1980) 22, 87-96]. With an increase of ionic strength, the helix becomes more regular and compact with a slightly reduced outer diameter and a decreased pitch, the dimensions resembling those proposed for solenoid models. PMID:7308214

  13. Nonoxynol-9: in vivo disposition, metabolism and in vitro spermicidal assessment of selected oligomers

    SciTech Connect

    Walter, B.A.

    1988-01-01

    The disposition of nonoxynol-9 labelled with carbon-14 at the ethylene oxide units was studied following an i.v. or vaginal administration to female Sprague Dawley rats. The results from the vaginal administration studies indicate 12.8% absorption of (C-14) radioactivity in 6.0h and 37.7% in 24 h. Tissue distribution studies showed that the small and large intestines, including their contents, had the highest C-14 activity by either route of administration. Radiomonitored HPLC of bile collected at 6.0h and urine at 6.0, 24.0 and 48.0h following an i.v. injection of (C-14) nonoxynol-9 showed that the compound was completely metabolized in the body of the rat. Pharmacokinetics of the most abundant oligomer (E.O.8) following an i.v. administration indicated a rapid distribution to a peripheral compartment followed by a slower elimination (half-life = 196min) of the E.O.8 from the plasma. The in vitro spermicidal activity of various molecular weight N-9 oligomers was compared to N-9 with rabbit spermatozoa. When HPLC purified fractions of N-9 were formulated with PVP and evaluated in equimolar concentrations the order of spermicidal activity was: middle MW fraction (E.O. = 6-8) > N-9 > high MW fraction (E.O. = 11-13) > low MW fraction (E.O. = 1-4). Also the N-9 - PVP complex was more effective in immobilizing spermatozoa than N-9 alone.

  14. Oligomer formation in the troposphere: from experimental knowledge to 3-D modeling

    NASA Astrophysics Data System (ADS)

    Lemaire, Vincent; Coll, Isabelle; Couvidat, Florian; Mouchel-Vallon, Camille; Seigneur, Christian; Siour, Guillaume

    2016-04-01

    The organic fraction of atmospheric aerosols has proven to be a critical element of air quality and climate issues. However, its composition and the aging processes it undergoes remain insufficiently understood. This work builds on laboratory knowledge to simulate the formation of oligomers from biogenic secondary organic aerosol (BSOA) in the troposphere at the continental scale. We compare the results of two different modeling approaches, a first-order kinetic process and a pH-dependent parameterization, both implemented in the CHIMERE air quality model (AQM) (www.lmd.polytechnique.fr/chimere), to simulate the spatial and temporal distribution of oligomerized secondary organic aerosol (SOA) over western Europe. We also included a comparison of organic carbon (OC) concentrations at two EMEP (European Monitoring and Evaluation Programme) stations. Our results show that there is a strong dependence of the results on the selected modeling approach: while the irreversible kinetic process leads to the oligomerization of about 50 % of the total BSOA mass, the pH-dependent approach shows a broader range of impacts, with a strong dependency on environmental parameters (pH and nature of aerosol) and the possibility for the process to be reversible. In parallel, we investigated the sensitivity of each modeling approach to the representation of SOA precursor solubility (Henry's law constant values). Finally, the pros and cons of each approach for the representation of SOA aging are discussed and recommendations are provided to improve current representations of oligomer formation in AQMs.

  15. Calcium flux-independent NMDA receptor activity is required for Aβ oligomer-induced synaptic loss

    PubMed Central

    Birnbaum, J H; Bali, J; Rajendran, L; Nitsch, R M; Tackenberg, C

    2015-01-01

    Synaptic loss is one of the major features of Alzheimer's disease (AD) and correlates with the degree of dementia. N-methyl-d-aspartate receptors (NMDARs) have been shown to mediate downstream effects of the β-amyloid peptide (Aβ) in AD models. NMDARs can trigger intracellular cascades via Ca2+ entry, however, also Ca2+-independent (metabotropic) functions of NMDARs have been described. We aimed to determine whether ionotropic or metabotropic NMDAR signaling is required for the induction of synaptic loss by Aβ. We show that endogenous Aβ as well as exogenously added synthetic Aβ oligomers induced dendritic spine loss and reductions in pre- and postsynaptic protein levels in hippocampal slice cultures. Synaptic alterations were mitigated by blocking glutamate binding to NMDARs using NMDAR antagonist APV, but not by preventing ion flux with Ca2+ chelator BAPTA or open-channel blockers MK-801 or memantine. Aβ increased the activity of p38 MAPK, a kinase involved in long-term depression and inhibition of p38 MAPK abolished the loss of dendritic spines. Aβ-induced increase of p38 MAPK activity was prevented by APV but not by BAPTA, MK-801 or memantine treatment highlighting the role of glutamate binding to NMDARs but not Ca2+ flux for synaptic degeneration by Aβ. We further show that treatment with the G protein inhibitor pertussis toxin (PTX) did not prevent dendritic spine loss in the presence of Aβ oligomers. Our data suggest that Aβ induces the activation of p38 MAPK and subsequent synaptic loss through Ca2+ flux- and G protein-independent mechanisms. PMID:26086964

  16. Calcium flux-independent NMDA receptor activity is required for Aβ oligomer-induced synaptic loss.

    PubMed

    Birnbaum, J H; Bali, J; Rajendran, L; Nitsch, R M; Tackenberg, C

    2015-01-01

    Synaptic loss is one of the major features of Alzheimer's disease (AD) and correlates with the degree of dementia. N-methyl-D-aspartate receptors (NMDARs) have been shown to mediate downstream effects of the β-amyloid peptide (Aβ) in AD models. NMDARs can trigger intracellular cascades via Ca(2+) entry, however, also Ca(2+)-independent (metabotropic) functions of NMDARs have been described. We aimed to determine whether ionotropic or metabotropic NMDAR signaling is required for the induction of synaptic loss by Aβ. We show that endogenous Aβ as well as exogenously added synthetic Aβ oligomers induced dendritic spine loss and reductions in pre- and postsynaptic protein levels in hippocampal slice cultures. Synaptic alterations were mitigated by blocking glutamate binding to NMDARs using NMDAR antagonist APV, but not by preventing ion flux with Ca(2+) chelator BAPTA or open-channel blockers MK-801 or memantine. Aβ increased the activity of p38 MAPK, a kinase involved in long-term depression and inhibition of p38 MAPK abolished the loss of dendritic spines. Aβ-induced increase of p38 MAPK activity was prevented by APV but not by BAPTA, MK-801 or memantine treatment highlighting the role of glutamate binding to NMDARs but not Ca(2+) flux for synaptic degeneration by Aβ. We further show that treatment with the G protein inhibitor pertussis toxin (PTX) did not prevent dendritic spine loss in the presence of Aβ oligomers. Our data suggest that Aβ induces the activation of p38 MAPK and subsequent synaptic loss through Ca(2+) flux- and G protein-independent mechanisms. PMID:26086964

  17. Series of Multifluorine Substituted Oligomers for Organic Solar Cells with Efficiency over 9% and Fill Factor of 0.77 by Combination Thermal and Solvent Vapor Annealing.

    PubMed

    Wang, Jin-Liang; Liu, Kai-Kai; Yan, Jun; Wu, Zhuo; Liu, Feng; Xiao, Fei; Chang, Zheng-Feng; Wu, Hong-Bin; Cao, Yong; Russell, Thomas P

    2016-06-22

    We report the synthesis of a family of multifluorine substituted oligomers and the corresponding polymer that have the same backbones but different conjugation lengths and amounts of fluorine atoms on the backbone. The physical properties and photovoltaic performances of these materials were systematically investigated using optical absorption, charge mobility, atomic force microscopy, transmission electron microscopy, grazing incidence X-ray diffraction, resonant soft X-ray scattering methods, and photovoltaic devices. The power conversion efficiencies (PCEs) based on oligomers were much higher than that in the polymer. Moreover, the devices based on BIT6F and BIT10F, which have an axisymmetric electron-deficient difluorobenzothiadiazole as the central unit, gave slightly higher PCEs than those with centrosymmetric electron-rich indacenodithiophene (IDT) as the central unit (BIT4F or BIT8F). Using proper solvent vapor annealing (SVA), particularly using thermal annealing (TA) followed by SVA, the device performance could be significantly improved. Notably, the best PCE of 9.1% with a very high FF of 0.76 was achieved using the medium-sized oligomer BIT6F with the optimized film morphology. This efficiency is the highest value reported for organic solar cells from small-molecules without rhodanine terminal group. More excitingly, devices from the shortest oligomer BIT4F showed an impressively high FF of 0.77 (the highest FF value reported for solution-processed small-molecule organic solar cells). These results indicate that photovoltaic performances of oligomers can be modulated through successive change in chain-length and fluorine atoms, alternating spatial symmetric core, and combined post-treatments. PMID:27225322

  18. Absence of amyloid β oligomers at the postsynapse and regulated synaptic Zn2+ in cognitively intact aged individuals with Alzheimer’s disease neuropathology

    PubMed Central

    2012-01-01

    Background Early cognitive impairment in Alzheimer Disease (AD) is thought to result from the dysfunctional effect of amyloid beta (Aβ) oligomers targeting the synapses. Some individuals, however, escape cognitive decline despite the presence of the neuropathologic features of AD (Aβ plaques and neurofibrillary tangles). We term this group Non-Demented with AD Neuropathology or NDAN. The present study illustrates one putative resistance mechanism involved in NDAN cases which may suggest targets for the effective treatment of AD. Results Here we describe the localization of Aβ oligomers at the postsynapse in hippocampi from AD cases. Notably, however, we also found that while present in soluble fractions, Aβ oligomers are absent from hippocampal postsynapses in NDAN cases. In addition, levels of phosphorylated (active) CREB, a transcription factor important for synaptic plasticity, are normal in NDAN individuals, suggesting that their synapses are functionally intact. Analysis of Zn2+ showed that levels were increased in both soluble fractions and synaptic vesicles in AD hippocampi, paralleled by a decrease of expression of the synaptic vesicle Zn2+ transporter, ZnT3. Conversely, in NDAN individuals, levels of Zn2+ in soluble fractions were significantly lower than in AD, whereas in synaptic vesicles the levels of Zn2+ were similar to AD, but accompanied by preserved expression of the ZnT3. Conclusions Taken together, these data illustrate that despite substantial AD neuropathology, Aβ oligomers, and increased synaptic vesicle Zn2+, susceptible brain tissue in these aged NDAN individuals features, as compared to symptomatic AD subjects, significantly lower total Zn2+ levels and no association of Aβ oligomers with the postsynapse, which collectively may promote the maintenance of intact cognitive function. PMID:22640423

  19. Opposite translocation of long and short oligomers through a nanopore

    NASA Astrophysics Data System (ADS)

    Getfert, Sebastian; Töws, Thomas; Reimann, Peter

    2013-06-01

    We consider elongated cylindrical particles, modeling, e.g., DNA fragments or nanorods, while they translocate under the action of an externally applied voltage through a solid state nanopore. Particular emphasis is put on the concomitant potential energy landscape encountered by the particle on its passage through the pore due to the complex interplay of various electrohydrodynamic effects beyond the realm of small Debye lengths. We find that the net potential energy difference across the membrane may be of opposite sign for short and long particles of equal diameters and charge densities (e.g., oligomers). Thermal noise thus leads to biased diffusion through the pore in opposite directions. By means of an additional membrane gate electrode it is even possible to control the specific particle length at which this transport inversion occurs.

  20. Formation of RNA oligomers on montmorillonite: site of catalysis

    NASA Technical Reports Server (NTRS)

    Ertem, G.; Ferris, J. P.

    1998-01-01

    Certain montmorillonites catalyze the self condensation of the 5'-phosphorimidazolide of nucleosides in pH 8 aqueous electrolyte solutions at ambient temperatures leading to formation of RNA oligomers. In order to establish the nature of the sites on montmorillonite responsible for this catalytic activity, oligomerization reactions were run with montmorillonites which had been selectively modified (I) at the edges by (a) fluoride treatment, (b) silylation, (c) metaphosphate treatment of the anion exchange sites (II) in the interlayer by (a) saturation with quaternary alkylammonium ions of increasing size, (b) aluminum polyoxo cations. High pressure liquid chromatography, HPLC, analysis of condensation products for their chain lengths and yields indicated that modification at the edges did not affect the catalytic activity to a significant extent, while blocking the interlayer strongly inhibited product formation.

  1. Electronic properties of acenes: Oligomer to polymer structure

    NASA Astrophysics Data System (ADS)

    Dos Santos, M. C.

    2006-07-01

    The conformations and electronic structures of long oligoacenes [ C2H2(C4H2)n , 20⩽n⩽23 ] and polyacene [(C8H4)x] were theoretically investigated through density functional theory adopting the hybrid B3LYP/6-31G(d) functional. The long oligoacenes present a cis conformation and solitonlike distortions along the chain. The defective regions having uniform bond lengths produce localized states on the top of the oligomer valence band. The spontaneous creation of bond alternation defects leads to high-spin magnetic ground states. The nonmagnetic state of polyacene presents a Peierls-distorted trans conformation which is lower in energy by a few meV per unit cell from the symmetric (nonalternating) state. The lowest-energy structure is predicted to present a cis pattern of bonds with alternation defects and a triplet state per unit cell.

  2. Characterization of glycidyl methacrylate – Crosslinked hyaluronan hydrogel scaffolds incorporating elastogenic hyaluronan oligomers

    PubMed Central

    Ibrahim, S.; Kothapalli, C.R.; Kang, Q.K.; Ramamurthi, A.

    2013-01-01

    Prior studies on two-dimensional cell cultures suggest that hyaluronic acid (HA) stimulates cell-mediated regeneration of extracellular matrix structures, specifically those containing elastin, though such biologic effects are dependent on HA fragment size. Towards being able to regenerate three-dimensional (3-D) elastic tissue constructs, the present paper studies photo-crosslinked hydrogels containing glycidyl methacrylate (GM)-derivatized bio-inert high molecular weight(HMW)HA (1 × 106 Da) and a bioactive HA oligomer mixture (HA-o: MW ~0.75 kDa). The mechanical (rheology, degradation) and physical (apparent crosslinking density, swelling ratio) properties of the gels varied as a function of incorporated HA oligomer content; however, overall, the mechanics of these hydrogels were too weak for vascular applications as stand-alone materials. Upon in vivo subcutaneous implantation, only a few inflammatory cells were evident around GM–HA gels, however their number increased as HA-o content within the gels increased, and the collagen I distribution was uniform. Smooth muscle cells (SMC) were encapsulated into GM hydrogels, and calcein acetoxymethyl detection revealed that the cells were able to endure twofold the level of UV exposure used to crosslink the gels. After 21 days of culture, SMC elastin production, measured by immunofluorescence quantification, showed HA-o to increase cellular deposition of elastic matrix twofold relative to HA-o-free GM–HAgels. These results demonstrate that cell response to HA/HA-o is not altered by their methacrylation and photo-crosslinking into a hydrogel, and that HA-o incorporation into cell-encapsulating hydrogel scaffolds can be useful for enhancing their production of elastic matrix structures in a 3-D space, important for regenerating elastic tissues. PMID:20709199

  3. Species Specific Differences of CD1d Oligomer Loading In Vitro

    PubMed Central

    Paletta, Daniel; Fichtner, Alina Suzann; Starick, Lisa; Porcelli, Steven A.; Savage, Paul B.; Herrmann, Thomas

    2015-01-01

    CD1d molecules are MHC class I-like molecules that present glycolipids to iNKT cells. The highly conserved interaction between CD1d:α-Galactosylceramide (αGC) complexes and the iNKT TCR not only defines this population of αβ T cells but can also be used for its direct identification. Therefore, CD1d oligomers are a widely used tool for iNKT cell related investigations. To this end, the lipid chains of the antigen have to be inserted into the hydrophobic pockets of the CD1d binding cleft, often with help of surfactants. In this study, we investigated the influence of different surfactants (Triton X-100, Tween 20, Tyloxapol) on in vitro loading of CD1d molecules derived from four different species (human, mouse, rat and cotton rat) with αGC and derivatives carrying modifications of the acyl-chain (DB01-1, PBS44) and a 6-acetamido-6-deoxy-addition at the galactosyl head group (PBS57). We also compared rat CD1d dimers with tetramers and staining of an iNKT TCR transductant was used as readout for loading efficacy. The results underlined the importance of CD1d loading efficacy for proper analysis of iNKT TCR binding and demonstrated the necessity to adjust loading conditions for each oligomer/glycolipid combination. The efficient usage of surfactants as a tool for CD1d loading was revealed to be species-specific and depending on the origin of the CD1d producing cells. Additional variation of surfactant-dependent loading efficacy between tested glycolipids was influenced by the acyl-chain length and the modification of the galactosyl head group with PBS57 showing the least dependence on surfactants and the lowest degree of species-dependent differences. PMID:26599805

  4. Characterization of glycidyl methacrylate - crosslinked hyaluronan hydrogel scaffolds incorporating elastogenic hyaluronan oligomers.

    PubMed

    Ibrahim, S; Kothapalli, C R; Kang, Q K; Ramamurthi, A

    2011-02-01

    Prior studies on two-dimensional cell cultures suggest that hyaluronic acid (HA) stimulates cell-mediated regeneration of extracellular matrix structures, specifically those containing elastin, though such biologic effects are dependent on HA fragment size. Towards being able to regenerate three-dimensional (3-D) elastic tissue constructs, the present paper studies photo-crosslinked hydrogels containing glycidyl methacrylate (GM)-derivatized bio-inert high molecular weight (HMW) HA (1 × 10(6)Da) and a bioactive HA oligomer mixture (HA-o: MW ∼0.75 kDa). The mechanical (rheology, degradation) and physical (apparent crosslinking density, swelling ratio) properties of the gels varied as a function of incorporated HA oligomer content; however, overall, the mechanics of these hydrogels were too weak for vascular applications as stand-alone materials. Upon in vivo subcutaneous implantation, only a few inflammatory cells were evident around GM-HA gels, however their number increased as HA-o content within the gels increased, and the collagen I distribution was uniform. Smooth muscle cells (SMC) were encapsulated into GM hydrogels, and calcein acetoxymethyl detection revealed that the cells were able to endure twofold the level of UV exposure used to crosslink the gels. After 21 days of culture, SMC elastin production, measured by immunofluorescence quantification, showed HA-o to increase cellular deposition of elastic matrix twofold relative to HA-o-free GM-HA gels. These results demonstrate that cell response to HA/HA-o is not altered by their methacrylation and photo-crosslinking into a hydrogel, and that HA-o incorporation into cell-encapsulating hydrogel scaffolds can be useful for enhancing their production of elastic matrix structures in a 3-D space, important for regenerating elastic tissues. PMID:20709199

  5. Synthetic oligomer analysis using atmospheric pressure photoionization mass spectrometry at different photon energies.

    PubMed

    Desmazières, Bernard; Legros, Véronique; Giuliani, Alexandre; Buchmann, William

    2014-01-15

    Atmospheric pressure photoionization (APPI) followed by mass spectrometric detection was used to ionize a variety of polymers: polyethylene glycol, polymethyl methacrylate, polystyrene, and polysiloxane. In most cases, whatever the polymer or the solvent used (dichloromethane, tetrahydrofuran, hexane, acetone or toluene), only negative ion mode produced intact ions such as chlorinated adducts, with no or few fragmentations, in contrast to the positive ion mode that frequently led to important in-source fragmentations. In addition, it was shown that optimal detection of polymer distributions require a fine tuning of other source parameters such as temperature and ion transfer voltage. Series of mass spectra were recorded in the negative mode, in various solvents (dichloromethane, tetrahydrofuran, hexane, toluene, and acetone), by varying the photon energy from 8eV up to 10.6eV using synchrotron radiation. To these solvents, addition of a classical APPI dopant (toluene or acetone) was not necessary. Courtesy of the synchrotron radiation, it was demonstrated that the photon energy required for an efficient ionization of the polymer was correlated to the ionization energy of the solvent. As commercial APPI sources typically use krypton lamps with energy fixed at 10eV and 10.6eV, the study of the ionization of polymers over a wavelength range allowed to confirm and refine the previously proposed ionization mechanisms. Moreover, the APPI source can efficiently be used as an interface between size exclusion chromatography or reverse phase liquid chromatography and MS for the study of synthetic oligomers. However, the photoionization at fixed wavelength of polymer standards with different molecular weights showed that it was difficult to obtain intact ionized oligomers with molecular weights above a few thousands. PMID:24370106

  6. Transthyretin as both a sensor and a scavenger of β-amyloid oligomers.

    PubMed

    Yang, Dennis T; Joshi, Gururaj; Cho, Patricia Y; Johnson, Jeffrey A; Murphy, Regina M

    2013-04-30

    Transthyretin (TTR) is a homotetrameric transport protein, assembled from monomers that each contain two four-stranded β-sheets and a short α-helix and loop. In the tetramer, the "inner" β-sheet forms a hydrophobic pocket while the helix and loop are solvent-exposed. β-Amyloid (Aβ) aggregates bind to TTR, and the level of binding is significantly reduced in mutants L82A (on the loop) and L110A (on the inner β-sheet). Protection against Aβ toxicity was demonstrated for wild-type TTR but not L82A or L110A, providing a direct link between TTR-Aβ binding and TTR-mediated cytoprotection. Protection is afforded at substoichiometric (1:100) TTR:Aβ molar ratios, and the level of binding of Aβ to TTR is highest for partially aggregated materials and decreased for freshly prepared or heavily aggregated Aβ, suggesting that TTR binds selectively to soluble toxic Aβ aggregates. A novel technique, nanoparticle tracking, is used to show that TTR arrests Aβ aggregation by both preventing formation of new aggregates and inhibiting growth of existing aggregates. TTR tetramers are normally quite stable; tetrameric structure is necessary for the protein's transport functions, and mutations that decrease tetramer stability have been linked to TTR amyloid diseases. However, TTR monomers bind more Aβ than do tetramers, presumably because the hydrophobic inner sheet is solvent-exposed upon tetramer disassembly. Wild-type and L110A tetramers, but not L82A, were destabilized upon being co-incubated with Aβ, suggesting that binding of Aβ to L82 triggers tetramer dissociation. Taken together, these results suggest a novel mechanism of action for TTR: the EF helix/loop "senses" the presence of soluble toxic Aβ oligomers, triggering destabilization of TTR tetramers and exposure of the hydrophobic inner sheet, which then "scavenges" these toxic oligomers and prevents them from causing cell death. PMID:23570378

  7. Plasma Membrane Calcium ATPase Activity Is Regulated by Actin Oligomers through Direct Interaction*

    PubMed Central

    Dalghi, Marianela G.; Fernández, Marisa M.; Ferreira-Gomes, Mariela; Mangialavori, Irene C.; Malchiodi, Emilio L.; Strehler, Emanuel E.; Rossi, Juan Pablo F. C.

    2013-01-01

    As recently described by our group, plasma membrane calcium ATPase (PMCA) activity can be regulated by the actin cytoskeleton. In this study, we characterize the interaction of purified G-actin with isolated PMCA and examine the effect of G-actin during the first polymerization steps. As measured by surface plasmon resonance, G-actin directly interacts with PMCA with an apparent 1:1 stoichiometry in the presence of Ca2+ with an apparent affinity in the micromolar range. As assessed by the photoactivatable probe 1-O-hexadecanoyl-2-O-[9-[[[2-[125I]iodo-4-(trifluoromethyl-3H-diazirin-3-yl)benzyl]oxy]carbonyl]nonanoyl]-sn-glycero-3-phosphocholine, the association of PMCA to actin produced a shift in the distribution of the conformers of the pump toward a calmodulin-activated conformation. G-actin stimulates Ca2+-ATPase activity of the enzyme when incubated under polymerizing conditions, displaying a cooperative behavior. The increase in the Ca2+-ATPase activity was related to an increase in the apparent affinity for Ca2+ and an increase in the phosphoenzyme levels at steady state. Although surface plasmon resonance experiments revealed only one binding site for G-actin, results clearly indicate that more than one molecule of G-actin was needed for a regulatory effect on the pump. Polymerization studies showed that the experimental conditions are compatible with the presence of actin in the first stages of assembly. Altogether, these observations suggest that the stimulatory effect is exerted by short oligomers of actin. The functional interaction between actin oligomers and PMCA represents a novel regulatory pathway by which the cortical actin cytoskeleton participates in the regulation of cytosolic Ca2+ homeostasis. PMID:23803603

  8. Fluorene- and benzofluorene-cored oligomers as low threshold and high gain amplifying media

    NASA Astrophysics Data System (ADS)

    Kazlauskas, Karolis; Kreiza, Gediminas; Bobrovas, Olegas; AdomÄ--nienÄ--, Ona; AdomÄ--nas, Povilas; Jankauskas, Vygintas; JuršÄ--nas, Saulius

    2015-07-01

    Deliberate control of intermolecular interactions in fluorene- and benzofluorene-cored oligomers was attempted via introduction of different-length alkyl moieties to attain high emission amplification and low amplified spontaneous emission (ASE) threshold at high oligomer concentrations. Containing fluorenyl peripheral groups decorated with different-length alkyl moieties, the oligomers were found to express weak concentration quenching of emission, yet excellent carrier drift mobilities (close to 10-2 cm2/V/s) in the amorphous films. Owing to the larger radiative decay rates (>1.0 × 109 s-1) and smaller concentration quenching, fluorene-cored oligomers exhibited down to one order of magnitude lower ASE thresholds at higher concentrations as compared to those of benzofluorene counterparts. The lowest threshold (300 W/cm2) obtained for the fluorene-cored oligomers at the concentration of 50 wt % in polymer matrix is among the lowest reported for solution-processed amorphous films in ambient conditions, what makes the oligomers promising for lasing application. Great potential in emission amplification was confirmed by high maximum net gain (77 cm-1) revealed for these compounds. Although the photostability of the oligomers was affected by photo-oxidation, it was found to be comparable to that of various organic lasing materials including some commercial laser dyes evaluated under similar excitation conditions.

  9. Fluorene- and benzofluorene-cored oligomers as low threshold and high gain amplifying media

    SciTech Connect

    Kazlauskas, Karolis Kreiza, Gediminas; Bobrovas, Olegas; Adomėnienė, Ona; Adomėnas, Povilas; Juršėnas, Saulius; Jankauskas, Vygintas

    2015-07-27

    Deliberate control of intermolecular interactions in fluorene- and benzofluorene-cored oligomers was attempted via introduction of different-length alkyl moieties to attain high emission amplification and low amplified spontaneous emission (ASE) threshold at high oligomer concentrations. Containing fluorenyl peripheral groups decorated with different-length alkyl moieties, the oligomers were found to express weak concentration quenching of emission, yet excellent carrier drift mobilities (close to 10{sup −2} cm{sup 2}/V/s) in the amorphous films. Owing to the larger radiative decay rates (>1.0 × 10{sup 9 }s{sup −1}) and smaller concentration quenching, fluorene-cored oligomers exhibited down to one order of magnitude lower ASE thresholds at higher concentrations as compared to those of benzofluorene counterparts. The lowest threshold (300 W/cm{sup 2}) obtained for the fluorene-cored oligomers at the concentration of 50 wt % in polymer matrix is among the lowest reported for solution-processed amorphous films in ambient conditions, what makes the oligomers promising for lasing application. Great potential in emission amplification was confirmed by high maximum net gain (77 cm{sup −1}) revealed for these compounds. Although the photostability of the oligomers was affected by photo-oxidation, it was found to be comparable to that of various organic lasing materials including some commercial laser dyes evaluated under similar excitation conditions.

  10. The case for soluble Aβ oligomers as a drug target in Alzheimer's disease.

    PubMed

    Hefti, Franz; Goure, William F; Jerecic, Jasna; Iverson, Kent S; Walicke, Patricia A; Krafft, Grant A

    2013-05-01

    Soluble Aβ oligomers are now widely recognized as key pathogenic structures in Alzheimer's disease. They inhibit synaptic function, leading to early memory deficits and synaptic degeneration, and they trigger the downstream neuronal signaling responsible for phospho-tau Alzheimer's pathology. The marginal effects observed in recent clinical studies of solanezumab, targeting monomeric Aβ, and bapineuzumab, targeting amyloid plaques, prompted expert comments that drug discovery efforts in Alzheimer's disease should focus on soluble forms of Aβ rather than fibrillar Aβ deposits found in amyloid plaques. Accumulating scientific data suggest that soluble Aβ oligomers represent the optimal intervention target within the amyloid manifold. Active drug discovery approaches include antibodies that selectively capture soluble Aβ oligomers, selective modifiers of oligomer assembly, and receptor antagonists. The onset of symptomatic clinical benefit is expected to be rapid for such agents, because neuronal memory signaling should normalize on blockage of soluble Aβ oligomers. This key feature is not shared by amyloid-lowering therapeutics, and it should translate into streamlined clinical development for oligomer-targeting drugs. Oligomer-targeting drugs should also confer long-term disease modification and slowing of disease progression, because they prevent the downstream signaling responsible for phospho-tau mediated cytoskeletal degeneration. PMID:23582316

  11. Synthesis and Optoelectronic Properties of Thiophene Donor and Thiazole Acceptor Based Blue Fluorescent Conjugated Oligomers.

    PubMed

    Mahesh, K; Karpagam, S

    2016-07-01

    We report on the synthesis and characterization of low band gap, blue light emitting and thermal stable conjugated oligomer by Wittig condensation. Thiophene and thiazole type of donor-acceptor based series of conjugated oligomers, Oligo-4,5-bis-[2-[5-[2-thiophene-2-yl-vinyl]thiophene-2-yl]-vinyl]-thiazole (OBTV-TZ) and Oligo-2,4,5-Tris-[2-[5-[2-thiophene-2-yl-vinyl]thiophene-2-yl]-vinyl]-thiazole (OTTV-TZ) were synthesized. These oligomers were confirmed by FT-IR and (1)H-NMR and LC/MS analysis. The effect of the number of thiophene rings on the optical, electrochemical, thermal and morphological properties of the oligomers were systematically investigated. Both oligomers were exhibited almost same absorption wavelength in methanol solution (λmax = 365 nm and 369 nm) which indicates both oligomers illustrate similar intra molecular charge transfer (ICT). In solid state, the oligomers were exhibited broadening peaks with higher onset absorptions (λmax = 600 nm and 580 nm). The photoluminescence absorption spectrum of the oligomers was observed at 433 nm and 434 nm respectively in methanol solution with blue emission. The electrochemical band gap ([Formula: see text]) of the OBTV-TZ was 1.55 eV (low band gap) and OTTV-TZ was exhibited greater highest occupied molecular orbital (HOMO) value (E HOMO = -6.6 eV). Moreover morphological parameters of both oligomer film of 2D and 3D diagrams were observed by using AFM studies. PMID:27256285

  12. Modelling Ser129 Phosphorylation Inhibits Membrane Binding of Pore-Forming Alpha-Synuclein Oligomers

    PubMed Central

    Nübling, Georg Sebastian; Levin, Johannes; Bader, Benedikt; Lorenzl, Stefan; Hillmer, Andreas; Högen, Tobias; Kamp, Frits; Giese, Armin

    2014-01-01

    Background In several neurodegenerative diseases, hyperphosphorylation at position Ser129 is found in fibrillar deposits of alpha-synuclein (asyn), implying a pathophysiological role of asyn phosphorylation in neurodegeneration. However, recent animal models applying asyn phosphorylation mimics demonstrated a protective effect of phosphorylation. Since metal-ion induced asyn oligomers were identified as a potential neurotoxic aggregate species with membrane pore-forming abilities, the current study was undertaken to determine effects of asyn phosphorylation on oligomer membrane binding. Methods We investigated the influence of S129 phosphorylation on interactions of metal-ion induced asyn oligomers with small unilamellar lipid vesicles (SUV) composed of POPC and DPPC applying the phosphorylation mimic asyn129E. Confocal single-particle fluorescence techniques were used to monitor membrane binding at the single-particle level. Results Binding of asyn129E monomers to gel-state membranes (DPPC-SUV) is slightly reduced compared to wild-type asyn, while no interactions with membranes in the liquid-crystalline state (POPC-SUV) are seen for both asyn and asyn129E. Conversely, metal-ion induced oligomer formation is markedly increased in asyn129E. Surprisingly, membrane binding to POPC-SUV is nearly absent in Fe3+ induced asyn129E oligomers and markedly reduced in Al3+ induced oligomers. Conclusion The protective effect of pseudophosphorylation seen in animal models may be due to impeded oligomer membrane binding. Phosphorylation at Ser129 may thus have a protective effect against neurotoxic asyn oligomers by preventing oligomer membrane binding and disruption of the cellular electrophysiological equilibrium. Importantly, these findings put a new complexion on experimental pharmaceutical interventions against POLO-2 kinase. PMID:24911099

  13. Red-emitting π-conjugated oligomers infused single-wall carbon nanotube sheets

    NASA Astrophysics Data System (ADS)

    Fujimori, Toshihiko; Urita, Koki

    2016-04-01

    We demonstrate the one-step thermal fusion and infusion of pyrene molecules inside single-wall carbon nanotubes (SWCNTs). Despite the presence of metallic-SWCNTs, which behave as a quencher due to gapless electronic states, the nanohybrids consisting of pyrene and/or azupyrene oligomers infused SWCNT sheets exhibit red fluorescence by the ultraviolet, blue, and green light excitations. The wavelength-independent light-emitting behavior is explained by (1) infused PAH oligomers inside semiconducting-SWCNTs and (2) the peculiar π-π interaction through mixed π-conjugated state between the π-conjugated oligomers and non-armchair metallic-SWCNTs.

  14. Phenylethynyl Terminated Arylene Ether Oxadiazole and Triazole Oligomers and Their Cured Polymers

    NASA Technical Reports Server (NTRS)

    Thompson, C. M.; Hergenrother, P. M.

    2001-01-01

    Several novel phenylethynyl terminated arylene ether oligomers containing oxadiazole and triazole rings were prepared as part of an effort to develop high performance polymers with an attractive combination of properties (e.g. processability and mechanical performance) for future NASA applications. The oligomers displayed low melt viscosities and good solubilities. Thin films cast from solutions of the oligomers and cured for one hour at 350 C in air gave good tensile properties. Titanium to titanium (6Al-4V) tensile shear specimens were readily fabricated and provided moderate strengths. The chemistry and properties of these new materials are discussed.

  15. ACD toxin-produced actin oligomers poison formin-controlled actin polymerization

    PubMed Central

    Heisler, David B.; Kudryashova, Elena; Grinevich, Dmitry O.; Suarez, Cristian; Winkelman, Jonathan D.; Birukov, Konstantin G.; Kotha, Sainath R.; Parinandi, Narasimham L.; Vavylonis, Dimitrios; Kovar, David R.; Kudryashov, Dmitri S.

    2015-01-01

    The actin crosslinking domain (ACD) is an actin-specific toxin produced by several pathogens, including life-threatening spp. of Vibrio cholerae, Vibrio vulnificus, and Aeromonas hydrophila. Actin crosslinking by ACD is thought to lead to slow cytoskeleton failure owing to a gradual sequestration of actin in the form of nonfunctional oligomers. Here we found that ACD converted cytoplasmic actin into highly toxic oligomers that potently “poisoned” the ability of major actin assembly proteins, formins, to sustain actin polymerization. Thus, ACD can target the most abundant cellular protein by employing actin oligomers as secondary toxins to efficiently subvert cellular functions of actin while functioning at very low doses. PMID:26228148

  16. Migration into food of polyethylene terephthalate (PET) cyclic oligomers from PET microwave susceptor packaging.

    PubMed

    Begley, T H; Dennison, J L; Hollifield, H C

    1990-01-01

    A quantitative method has been developed to measure the migration of polyethylene terephthalate (PET) cyclic oligomers from aluminized PET susceptor film-type food packaging into several food types. Microwaveable French fries, popcorn, fish sticks, waffles and pizza sold in susceptor-type packaging were purchased in local markets, cooked according to package instructions and analysed for PET oligomers. Appropriate food blanks were cooked in glass containers. Quantities of PET oligomers found in the foods ranged from less than 0.012 micrograms/g to approximately 7 micrograms/g. PMID:2150379

  17. The N-methylated peptide SEN304 powerfully inhibits Aβ(1-42) toxicity by perturbing oligomer formation.

    PubMed

    Amijee, Hozefa; Bate, Clive; Williams, Alun; Virdee, Jasmeet; Jeggo, Ross; Spanswick, David; Scopes, David I C; Treherne, J Mark; Mazzitelli, Sonia; Chawner, Ross; Eyers, Claire E; Doig, Andrew J

    2012-10-23

    Oligomeric forms of β-amyloid (Aβ) have potent neurotoxic activity and are the primary cause of neuronal injury and cell death in Alzheimer's disease (AD). Compounds that perturb oligomer formation or structure may therefore be therapeutic for AD. We previously reported that d-[(chGly)-(Tyr)-(chGly)-(chGly)-(mLeu)]-NH(2) (SEN304) is able to inhibit Aβ aggregation and toxicity, shown primarily by thioflavin T fluorescence and MTT (Kokkoni, N. et al. (2006) N-Methylated peptide inhibitors of β-amyloid aggregation and toxicity. Optimisation of inhibitor structure. Biochemistry 45, 9906-9918). Here we extensively characterize how SEN304 affects Aβ(1-42) aggregation and toxicity, using biophysical assays (thioflavin T, circular dichroism, SDS-PAGE, size exclusion chromatography, surface plasmon resonance, traveling wave ion mobility mass spectrometry, electron microscopy, ELISA), toxicity assays in cell culture (MTT and lactate dehydrogenase in human SH-SHY5Y cells, mouse neuronal cell death and synaptophysin) and long-term potentiation in a rat hippocampal brain slice. These data, with dose response curves, show that SEN304 is a powerful inhibitor of Aβ(1-42) toxicity, particularly effective at preventing Aβ inhibition of long-term potentiation. It can bind directly to Aβ(1-42), delay β-sheet formation and promote aggregation of toxic oligomers into a nontoxic form, with a different morphology that cannot bind thioflavin T. SEN304 appears to work by inducing aggregation, and hence removal, of Aβ oligomers. It is therefore a promising lead compound for Alzheimer's disease. PMID:23025847

  18. Transforming growth factor beta 1 and hyaluronan oligomers synergistically enhance elastin matrix regeneration by vascular smooth muscle cells.

    PubMed

    Kothapalli, Chandrasekhar R; Taylor, Patricia M; Smolenski, Ryszard T; Yacoub, Magdi H; Ramamurthi, Anand

    2009-03-01

    Elastin is a vital structural and regulatory matrix protein that plays an important role in conferring elasticity to blood vessel wall. Previous tissue engineering approaches to regenerate elastin in situ or within tissue engineering constructs are curtailed by innate poor elastin synthesis potential by adult vascular smooth muscle cells (SMCs). Currently, we seek to develop cellular cues to enhance tropoelastin synthesis and improve elastin matrix yield, stability, and ultrastructure. Our earlier studies attest to the elastogenic utility of hyaluronan (HA)-based cellular cues, though their effects are fragment size dependent and dose dependent, with HA oligomers deemed most elastogenic. We presently show transforming growth factor beta 1 (TGF-beta1) and HA oligomers, when provided concurrently, to synergistically and dramatically improve elastin matrix regeneration by adult vascular SMCs. Together, these cues suppress SMC proliferation, enhance synthesis of tropoelastin (8-fold) and matrix elastin protein (5.5-fold), and also improve matrix elastin yield (45% of total elastin vs. 10% for nonadditive controls), possibly by more efficient recruitment of tropoelastin for crosslinking. The density of desmosine crosslinks within the elastin matrix was itself attenuated, although the cues together modestly increased production and activity of the elastin crosslinking enzyme, lysyl oxidase. TGF-beta1 and HA oligomers together induced much greater assembly of mature elastin fibers than they did separately, and did not induce matrix calcification. The present outcomes might be great utility to therapeutic regeneration of elastin matrix networks in situ within elastin-compromised vessels, and within tissue-engineered vascular graft replacements. PMID:18847364

  19. Dependence of tunneling current through a single molecule of phenylene oligomers on the molecular length.

    PubMed

    Wakamatsu, Satoshi; Fujii, Shintaro; Akiba, Uichi; Fujihira, Masamichi

    2003-01-01

    The electrical properties of single phenylene oligomers were studied in terms of the dependence of the tunneling current on the length of the oligomers using self-assembling techniques and scanning tunneling microscopy (STM). It is important to isolate single molecules in an insulating matrix for the measurement of the conductivity of the single molecule. We demonstrate here a novel self-assembled monolayer (SAM) matrix appropriate for isolation of the single molecules. A bicyclo[2.2.2]octane derivative was used for a SAM matrix, in which the single molecules were inserted at molecular lattice defects. The isolated single molecules of phenylene oligomers inserted in the SAM matrix were observed as protrusions in STM topography using a constant current mode. We measured the topographic heights of the molecular protrusions using STM and estimated the decay constant, beta, of the tunneling current through the single phenylene oligomers using a bilayer tunnel junction model. PMID:12801653

  20. The Anti-Prion Antibody 15B3 Detects Toxic Amyloid-β Oligomers.

    PubMed

    Stravalaci, Matteo; Tapella, Laura; Beeg, Marten; Rossi, Alessandro; Joshi, Pooja; Pizzi, Erika; Mazzanti, Michele; Balducci, Claudia; Forloni, Gianluigi; Biasini, Emiliano; Salmona, Mario; Diomede, Luisa; Chiesa, Roberto; Gobbi, Marco

    2016-07-01

    15B3 is a monoclonal IgM antibody that selectively detects pathological aggregates of the prion protein (PrP). We report the unexpected finding that 15B3 also recognizes oligomeric but not monomeric forms of amyloid-β (Aβ)42, an aggregating peptide implicated in the pathogenesis of Alzheimer's disease (AD). The 15B3 antibody: i) inhibits the binding of synthetic Aβ42 oligomers to recombinant PrP and neuronal membranes; ii) prevents oligomer-induced membrane depolarization; iii) antagonizes the inhibitory effects of oligomers on the physiological pharyngeal contractions of the nematode Caenorhabditis elegans; and iv) counteracts the memory deficits induced by intracerebroventricular injection of Aβ42 oligomers in mice. Thus this antibody binds to pathologically relevant forms of Aβ, and offers a potential research, diagnostic, and therapeutic tool for AD. PMID:27392850

  1. Beta-Amyloid Oligomers Activate Apoptotic BAK Pore for Cytochrome c Release

    PubMed Central

    Kim, Jaewook; Yang, Yoosoo; Song, Seung Soo; Na, Jung-Hyun; Oh, Kyoung Joon; Jeong, Cherlhyun; Yu, Yeon Gyu; Shin, Yeon-Kyun

    2014-01-01

    In Alzheimer’s disease, cytochrome c-dependent apoptosis is a crucial pathway in neuronal cell death. Although beta-amyloid (Aβ) oligomers are known to be the neurotoxins responsible for neuronal cell death, the underlying mechanisms remain largely elusive. Here, we report that the oligomeric form of synthetic Aβ of 42 amino acids elicits death of HT-22 cells. But, when expression of a bcl-2 family protein BAK is suppressed by siRNA, Aβ oligomer-induced cell death was reduced. Furthermore, significant reduction of cytochrome c release was observed with mitochondria isolated from BAK siRNA-treated HT-22 cells. Our in vitro experiments demonstrate that Aβ oligomers bind to BAK on the membrane and induce apoptotic BAK pores and cytochrome c release. Thus, the results suggest that Aβ oligomers function as apoptotic ligands and hijack the intrinsic apoptotic pathway to cause unintended neuronal cell death. PMID:25296312

  2. Preparative production of colominic acid oligomers via a facile microwave hydrolysis

    PubMed Central

    Patane, Jonathan; Trapani, Vincent; Villavert, Janice; McReynolds, Katherine Dawn

    2009-01-01

    The hydrolysis of colominic acid via microwave irradiation was studied for the production of short chain oligomers with a degree of polymerization (DP) of 1–6. This method was compared to the traditional acid hydrolytic method for the production of preparative quantities of short colominic acid oligomers. The oligomers were purified by size exclusion chromatography and characterized by 1H NMR. Optimal conditions for producing the dimer were found to be 12 minutes at 10% power in a 1000 Watt domestic microwave. This method is advantageous over the traditional technique in that the hydrolysis can be completed in just a few minutes, rather than hours, it is reproducible, and yields large quantities of the desirable short chain oligomers of colominic acid. PMID:19281967

  3. A semiempirical study of heterocycle oligomers and polymers in different dielectric media

    SciTech Connect

    Juerimaee, T.; Strandberg, M.; Karelson, M.

    1995-06-15

    Four common five-membered heterocycles-pyrrole, phosphole, thiophene, and furan- and their oligomers with the chain length of 2, 4, 6, and 10 units have been studied quantum chemically using the semiempirical PM3 parameterization. The oligomers of pyrrole and phosphole with the homolytically dissociated N-H bond and P-H bond, respectively, and oligomers of thiophene and furan with one electron removed per monomer unit (4n + 2 {pi}-electron bipolaron systems) have also been studied. The electronic properties of the respective polymers were extrapolated from the oligomer data. Bulk polymer effects on the electronic structure were modeled using the self-consistent reaction field theory in the multicavity approximation (MCa SCRF). 48 refs., 3 figs., 6 tabs.

  4. Development and characterization of a TAPIR-like mouse monoclonal antibody to amyloid-beta.

    PubMed

    Wang, Jun; Hara, Hideo; Makifuchi, Takao; Tabira, Takeshi

    2008-06-01

    Tissue amyloid plaque immuno-reactive (TAPIR) antibody was better related to the effect of immunotherapy in Alzheimer's disease (AD) than ELISA antibody. Here we used a hybridoma technique to develop a TAPIR-like anti-human amyloid-beta (Abeta) mouse monoclonal antibody. The obtained monoclonal antibody, 3.4A10, was an IgG2b isotype and recognized N-terminal portion of Abeta1-42 without binding denatured or native amyloid-beta protein precursor. It had higher affinity to Abeta1-42 than to Abeta1-40 by Biacore affinity analysis and stained preferably the peripheral part of senile plaques and recognized the plaque core less than 4G8. It inhibited the Abeta1-42 fibril formation as well as degraded pre-aggregated Abeta1-42 peptide in a thioflavin T fluorescence spectrophotometry assay. The in vivo studies showed that 3.4A10 treatment decreased amyloid burden compared to the control group and significantly reduced Abeta42 levels rather than Abeta40 levels in brain lysates as well as the Abeta*56 oligomer (12mer) in TBS fraction of the brain lysates. 3.4A10 entered brain and decorated some plaques, which is surrounded by more Iba1-positive microglia. 3.4A10 therapy did not induce lymphocytic infiltration and obvious increase in microhemorrhage. We conclude that 3.4A10 is a TAPIR-like anti-human amyloid monoclonal antibody, and has a potential of therapeutic application for AD. PMID:18560128

  5. Simulation Study of the Contribution of Oligomer/Oligomer Binding to Capsid Assembly Kinetics

    PubMed Central

    Zhang, Tiequan; Schwartz, Russell

    2006-01-01

    The process by which hundreds of identical capsid proteins self-assemble into icosahedral structures is complex and poorly understood. Establishing constraints on the assembly pathways is crucial to building reliable theoretical models. For example, it is currently an open question to what degree overall assembly kinetics are dominated by one or a few most efficient pathways versus the enormous number theoretically possible. The importance of this question, however, is often overlooked due to the difficulties of addressing it in either theoretical or experimental practice. We apply a computer model based on a discrete-event simulation method to evaluate the contributions of nondominant pathways to overall assembly kinetics. This is accomplished by comparing two possible assembly models: one allowing growth to proceed only by the accretion of individual assembly subunits and the other allowing the binding of sterically compatible assembly intermediates any sizes. Simulations show that the two models perform almost identically under low binding rate conditions, where growth is strongly nucleation-limited, but sharply diverge under conditions of higher association rates or coat protein concentrations. The results suggest the importance of identifying the actual binding pattern if one is to build reliable models of capsid assembly or other complex self-assembly processes. PMID:16214864

  6. Cofilin Oligomer Formation Occurs In Vivo and Is Regulated by Cofilin Phosphorylation

    PubMed Central

    Goyal, Pankaj; Pandey, Dharmendra; Brünnert, Daniela; Hammer, Elke; Zygmunt, Marek; Siess, Wolfgang

    2013-01-01

    Background ADF/cofilin proteins are key regulators of actin dynamics. Their function is inhibited by LIMK-mediated phosphorylation at Ser-3. Previous in vitro studies have shown that dependent on its concentration, cofilin either depolymerizes F-actin (at low cofilin concentrations) or promotes actin polymerization (at high cofilin concentrations). Methodology/Principal Findings We found that after in vivo cross-linking with different probes, a cofilin oligomer (65 kDa) could be detected in platelets and endothelial cells. The cofilin oligomer did not contain actin. Notably, ADF that only depolymerizes F-actin was present mainly in monomeric form. Furthermore, we found that formation of the cofilin oligomer is regulated by Ser-3 cofilin phosphorylation. Cofilin but not phosphorylated cofilin was present in the endogenous cofilin oligomer. In vitro, formation of cofilin oligomers was drastically reduced after phosphorylation by LIMK2. In endothelial cells, LIMK-mediated cofilin phosphorylation after thrombin-stimulation of EGFP- or DsRed2-tagged cofilin transfected cells reduced cofilin aggregate formation, whereas inhibition of cofilin phosphorylation after Rho-kinase inhibitor (Y27632) treatment of endothelial cells promoted formation of cofilin aggregates. In platelets, cofilin dephosphorylation after thrombin-stimulation and Y27632 treatment led to an increased formation of the cofilin oligomer. Conclusion/Significance Based on our results, we propose that an equilibrium exists between the monomeric and oligomeric forms of cofilin in intact cells that is regulated by cofilin phosphorylation. Cofilin phosphorylation at Ser-3 may induce conformational changes on the protein-protein interacting surface of the cofilin oligomer, thereby preventing and/or disrupting cofilin oligomer formation. Cofilin oligomerization might explain the dual action of cofilin on actin dynamics in vivo. PMID:23951242

  7. Structure and properties of binary polystyrene-epoxy acrylate oligomer mixtures irradiated by electron beams

    SciTech Connect

    Lomonosova, N.V.

    1995-03-01

    The change in the structure of oriented polymer-oligomer systems based on polystyrene (PS) with M > 10{sup 6} and epoxy acrylate oligomers (aliphatic and aromatic) under irradiation by accelerated electrons was studied using birefringence, isometric heating, IR dichroism, and thermooptical analysis. Mechanical properties of these systems were investigated. It was found that, by adding aliphatic epoxy acrylate to PS and further irradiating this mixture, one can obtain both isotropic and oriented composites with higher strengths, elasticity moduli, and glass transition temperatures.

  8. Computer simulations and theoretical aspects of the depletion interaction in protein-oligomer mixtures

    NASA Astrophysics Data System (ADS)

    Bončina, M.; Reščič, J.; Kalyuzhnyi, Yu. V.; Vlachy, V.

    2007-07-01

    The depletion interaction between proteins caused by addition of either uncharged or partially charged oligomers was studied using the canonical Monte Carlo simulation technique and the integral equation theory. A protein molecule was modeled in two different ways: either as (i) a hard sphere of diameter 30.0Å with net charge 0, or +5, or (ii) as a hard sphere with discrete charges (depending on the pH of solution) of diameter 45.4Å. The oligomers were pictured as tangentially jointed, uncharged, or partially charged, hard spheres. The ions of a simple electrolyte present in solution were represented by charged hard spheres distributed in the dielectric continuum. In this study we were particularly interested in changes of the protein-protein pair-distribution function, caused by addition of the oligomer component. In agreement with previous studies we found that addition of a nonadsorbing oligomer reduces the phase stability of solution, which is reflected in the shape of the protein-protein pair-distribution function. The value of this function in protein-protein contact increases with increasing oligomer concentration, and is larger for charged oligomers. The range of the depletion interaction and its strength also depend on the length (number of monomer units) of the oligomer chain. The integral equation theory, based on the Wertheim Ornstein-Zernike approach applied in this study, was found to be in fair agreement with Monte Carlo results only for very short oligomers. The computer simulations for a model mimicking the lysozyme molecule (ii) are in qualitative agreement with small-angle neutron experiments for lysozyme-dextran mixtures.

  9. Styrene-terminated polysulfone oligomers as matrix material for graphite reinforced composites: An initial study

    NASA Technical Reports Server (NTRS)

    Garcia, Dana; Bowles, Kenneth J.; Vannucci, Raymond D.

    1987-01-01

    Styrene terminated polysulfone oligomers are part of an oligomeric class of compounds with end groups capable of thermal polymerization. These materials can be used as matrices for graphite reinforced composites. The initial evaluation of styrene terminated polysulfone oligomer based composites are summarized in terms of fabrication methods, and mechanical and environmental properties. In addition, a description and evaluation is provided of the NASA/Industry Fellowship Program for Technology Transfer.

  10. Transthyretin suppresses the toxicity of oligomers formed by misfolded proteins in vitro.

    PubMed

    Cascella, Roberta; Conti, Simona; Mannini, Benedetta; Li, Xinyi; Buxbaum, Joel N; Tiribilli, Bruno; Chiti, Fabrizio; Cecchi, Cristina

    2013-12-01

    Although human transthyretin (TTR) is associated with systemic amyloidoses, an anti-amyloidogenic effect that prevents Aβ fibril formation in vitro and in animal models has been observed. Here we studied the ability of three different types of TTR, namely human tetramers (hTTR), mouse tetramers (muTTR) and an engineered monomer of the human protein (M-TTR), to suppress the toxicity of oligomers formed by two different amyloidogenic peptides/proteins (HypF-N and Aβ42). muTTR is the most stable homotetramer, hTTR can dissociate into partially unfolded monomers, whereas M-TTR maintains a monomeric state. Preformed toxic HypF-N and Aβ42 oligomers were incubated in the presence of each TTR then added to cell culture media. hTTR, and to a greater extent M-TTR, were found to protect human neuroblastoma cells and rat primary neurons against oligomer-induced toxicity, whereas muTTR had no protective effect. The thioflavin T assay and site-directed labeling experiments using pyrene ruled out disaggregation and structural reorganization within the discrete oligomers following incubation with TTRs, while confocal microscopy, SDS-PAGE, and intrinsic fluorescence measurements indicated tight binding between oligomers and hTTR, particularly M-TTR. Moreover, atomic force microscopy (AFM), light scattering and turbidimetry analyses indicated that larger assemblies of oligomers are formed in the presence of M-TTR and, to a lesser extent, with hTTR. Overall, the data suggest a generic capacity of TTR to efficiently neutralize the toxicity of oligomers formed by misfolded proteins and reveal that such neutralization occurs through a mechanism of TTR-mediated assembly of protein oligomers into larger species, with an efficiency that correlates inversely with TTR tetramer stability. PMID:24075940

  11. Causative factors for formation of toxic islet amyloid polypeptide oligomer in type 2 diabetes mellitus

    PubMed Central

    Jeong, Hye Rin; An, Seong Soo A

    2015-01-01

    Human islet amyloid polypeptide (h-IAPP) is a peptide hormone that is synthesized and cosecreted with insulin from insulin-secreting pancreatic β-cells. Recently, h-IAPP was proposed to be the main component responsible for the cytotoxic pancreatic amyloid deposits in patients with type 2 diabetes mellitus (T2DM). Since the causative factors of IAPP (or amylin) oligomer aggregation are not fully understood, this review will discuss the various forms of h-IAPP aggregation. Not all forms of IAPP aggregates trigger the destruction of β-cell function and loss of β-cell mass; however, toxic oligomers do trigger these events. Once these toxic oligomers form under abnormal metabolic conditions in T2DM, they can lead to cell disruption by inducing cell membrane destabilization. In this review, the various factors that have been shown to induce toxic IAPP oligomer formation will be presented, as well as the potential mechanism of oligomer and fibril formation from pro-IAPPs. Initially, pro-IAPPs undergo enzymatic reactions to produce the IAPP monomers, which can then develop into oligomers and fibrils. By this mechanism, toxic oligomers could be generated by diverse pathway components. Thus, the interconnections between factors that influence amyloid aggregation (eg, absence of PC2 enzyme, deamidation, reduction of disulfide bonds, environmental factors in the cell, genetic mutations, copper metal ions, and heparin) will be presented. Hence, this review will aid in understanding the fundamental causative factors contributing to IAPP oligomer formation and support studies for investigating novel T2DM therapeutic approaches, such as the development of inhibitory agents for preventing oligomerization at the early stages of diabetic pathology. PMID:26604727

  12. Causative factors for formation of toxic islet amyloid polypeptide oligomer in type 2 diabetes mellitus.

    PubMed

    Jeong, Hye Rin; An, Seong Soo A

    2015-01-01

    Human islet amyloid polypeptide (h-IAPP) is a peptide hormone that is synthesized and cosecreted with insulin from insulin-secreting pancreatic β-cells. Recently, h-IAPP was proposed to be the main component responsible for the cytotoxic pancreatic amyloid deposits in patients with type 2 diabetes mellitus (T2DM). Since the causative factors of IAPP (or amylin) oligomer aggregation are not fully understood, this review will discuss the various forms of h-IAPP aggregation. Not all forms of IAPP aggregates trigger the destruction of β-cell function and loss of β-cell mass; however, toxic oligomers do trigger these events. Once these toxic oligomers form under abnormal metabolic conditions in T2DM, they can lead to cell disruption by inducing cell membrane destabilization. In this review, the various factors that have been shown to induce toxic IAPP oligomer formation will be presented, as well as the potential mechanism of oligomer and fibril formation from pro-IAPPs. Initially, pro-IAPPs undergo enzymatic reactions to produce the IAPP monomers, which can then develop into oligomers and fibrils. By this mechanism, toxic oligomers could be generated by diverse pathway components. Thus, the interconnections between factors that influence amyloid aggregation (eg, absence of PC2 enzyme, deamidation, reduction of disulfide bonds, environmental factors in the cell, genetic mutations, copper metal ions, and heparin) will be presented. Hence, this review will aid in understanding the fundamental causative factors contributing to IAPP oligomer formation and support studies for investigating novel T2DM therapeutic approaches, such as the development of inhibitory agents for preventing oligomerization at the early stages of diabetic pathology. PMID:26604727

  13. Ultrarobust Thin-Film Devices from Self-Assembled Metal-Terpyridine Oligomers.

    PubMed

    Karipidou, Zoi; Branchi, Barbara; Sarpasan, Mustafa; Knorr, Nikolaus; Rodin, Vadim; Friederich, Pascal; Neumann, Tobias; Meded, Velimir; Rosselli, Silvia; Nelles, Gabriele; Wenzel, Wolfgang; Rampi, Maria Anita; von Wrochem, Florian

    2016-05-01

    Ultrathin molecular layers of Fe(II) -terpyridine oligomers allow the fabrication of large-area crossbar junctions by conventional electrode vapor deposition. The junctions are electrically stable for over 2.5 years and operate over a wide range of temperatures (150-360 K) and voltages (±3 V) due to the high cohesive energy and packing density of the oligomer layer. Electrical measurements reveal ideal Richardson-Shottky emission in surprising agreement with electrochemical, optical, and photoemission data. PMID:26970207

  14. Monodisperse poly(triacetylene) oligomers extending from monomer to hexadecamer: joint experimental and theoretical investigation of physical properties

    PubMed

    Martin; Gubler; Cornil; Balakina; Boudon; Bosshard; Gisselbrecht; Diederich; Gunter; Gross; Bredas

    2000-10-01

    A series of monodisperse Et3-Si-end-capped poly(triacetylene) (PTA) oligomers ranging from monomer to hexadecamer was prepared by a fast and efficient statistical deprotection-oxidative Hay oligomerization protocol. The PTA oligomers exhibit an increasingly deep-yellow color with lengthening of the pi-conjugated backbone, feature excellent solubility in aprotic solvents, and exhibit melting points up to > 22 degrees C for the hexadecameric rod. This new dramatically extended oligo(enediyne) series now enables to investigate the evolution of the physico-chemical effects in PTAs beyond the linear 1/n versus property regime into the higher oligomer region where saturation becomes apparent. We report the results of joint experimental and theoretical studies, including analysis of the 13C NMR spectra, evaluation of the linear (UV/ Vis) and nonlinear [third-harmonic generation (THG) and degenerate four-wave mixing (DFWM)] optical properties, and characterization of the redox properties with cyclic and steady-state voltammetry. Up to the hexadecameric rod, an increasingly facile one-electron reduction step is observed, showing at the stage of the dodecamer, a leveling off tendency from the linear correlation between the inverse number of monomer units and the first reduction potential. The effective conjugation length (ECL) determined by means of UV/Vis spectroscopy revealed a pi-electron-delocalization length of about n = 10 monomeric units, which corroborates well with the oligomeric length for which in the 13C NMR spectrum C(sp2) and C(sp) resonances start to overlap. Third-harmonic generation (THG) and degenerate four-wave mixing (DFWM) measurements revealed for the second-order hyperpolarizability gamma a power law increase gammma-alpha-n(a) for oligomers up to the octamer with exponential factors a= 2.46+/-0.10 and a=2.64+/-0.20, respectively, followed by a smooth saturation around n = 10 repeating units. The power law coefficient a calculated with the help of the

  15. Liquid Crystalline Thermosets from Ester, Ester-Imide, and Ester-Amide Oligomers

    NASA Technical Reports Server (NTRS)

    Dingemans, Theodornus J. (Inventor); Weiser, Erik S. (Inventor); SaintClair, Terry L. (Inventor)

    2005-01-01

    Main chain thermotropic liquid crystal esters, ester-imides, and ester-amides were prepared from AA, BB, and AB type monomeric materials and were end-capped with phenylacetylene, phenylmaleimide, or nadimide reactive end-groups. The resulting reactive end-capped liquid crystal oligomers exhibit a variety of improved and preferred physical properties. The end-capped liquid crystal oligomers are thermotropic and have, preferably, molecular weights in the range of approximately 1000-15,OOO grams per mole. The end-capped liquid crystal oligomers have broad liquid crystalline melting ranges and exhibit high melt stability and very low melt viscosities at accessible temperatures. The end-capped liquid crystal oligomers are stable for up to an hour in the melt phase. These properties make the end-capped liquid crystal oligomers highly processable by a variety of melt process shape forming and blending techniques including film extrusion, fiber spinning, reactive injection molding (RIM), resin transfer molding (RTM), resin film injection (RFI), powder molding, pultrusion, injection molding, blow molding, plasma spraying and thermo-forming. Once processed and shaped, the end- capped liquid crystal oligomers were heated to further polymerize and form liquid crystalline thermosets (LCT). The fully cured products are rubbers above their glass transition temperatures. The resulting thermosets display many properties that are superior to their non-end-capped high molecular weight analogs.

  16. Effect of Zn(2+) ions on the assembly of amylin oligomers: insight into the molecular mechanisms.

    PubMed

    Wineman-Fisher, Vered; Miller, Yifat

    2016-08-01

    Amylin is an endocrine hormone and is a member of the family of amyloid peptides and proteins that emerge as potential scaffolds by self-assembly processes. Zn(2+) ions can bind to amylin peptides to form self-assembled Zn(2+)-amylin oligomers. In the current work the binding sites of Zn(2+) ions in the self-assembled amylin oligomers at various concentrations of zinc have been investigated. Our results yield two conclusions. First, in the absence of Zn(2+) ions polymorphic states (i.e. various classes of amylin oligomers) are obtained, but when Zn(2+) ions bind to amylin peptides to form Zn(2+)-amylin oligomers, the polymorphism is decreased, i.e. Zn(2+) ions bind only to specific classes of amylin. At low concentrations of Zn(2+) ions the polymorphism is smaller than at high concentrations. Second, the structural features of the self-assembled amylin oligomers are not affected by the presence of Zn(2+) ions. This study proposes new molecular mechanisms of the self-assembly of Zn(2+)-amylin oligomers. PMID:27425207

  17. Cellulose oligomers production and separation for the synthesis of new fully bio-based amphiphilic compounds.

    PubMed

    Billès, Elise; Onwukamike, Kelechukwu N; Coma, Véronique; Grelier, Stéphane; Peruch, Frédéric

    2016-12-10

    Cellulose oligomers are water-soluble, on the contrary to cellulose, which greatly increase their application range. In this study, cellulose oligomers were obtained from the acidic hydrolysis of cellulose with phosphoric acid. The global yield in water-soluble oligomers was around 23% with polymerization degree (DP) ranging from 1 to 12. The cellulose oligomers DP distribution was successfully reduced by differential solubilisation in methanol as one of the goals of this work was to avoid the use of a time-consuming full chromatographic separation. The methanol-soluble oligomers were mainly low DP (≤3). The oligomers of higher molar mass, composed of 42% of cellotetraose and 36% of cellopentaose, were then functionalized and coupled with stearic acid through azide-alkyne click chemistry to obtain amphiphilic compounds. The self-assembly of these new bio-based compounds was finally investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM) and their critical micellar concentration (CMC) was found to be in the same range as alkylmaltosides and alkylglucosides. PMID:27577903

  18. Liquid crystalline thermosets from ester, ester-imide, and ester-amide oligomers

    NASA Technical Reports Server (NTRS)

    Dingemans, Theodorous J. (Inventor); Weiser, Erik S. (Inventor); St. Clair, Terry L. (Inventor)

    2005-01-01

    Main chain thermotropic liquid crystal esters, ester-imides, and ester-amides were prepared from AA, BB, and AB type monomeric materials and were end-capped with phenylacetylene, phenylmaleimide, or nadimide reactive end-groups. The resulting reactive end-capped liquid crystal oligomers exhibit a variety of improved and preferred physical properties. The end-capped liquid crystal oligomers are thermotropic and have, preferably, molecular weights in the range of approximately 1000-15,000 grams per mole. The end-capped liquid crystal oligomers have broad liquid crystalline melting ranges and exhibit high melt stability and very low melt viscosities at accessible temperatures. The end-capped liquid crystal oligomers are stable for up to an hour in the melt phase. These properties make the end-capped liquid crystal oligomers highly processable by a variety of melt process shape forming and blending techniques including film extrusion, fiber spinning, reactive injection molding (RIM), resin transfer molding (RTM), resin film injection (RFI), powder molding, pultrusion, injection molding, blow molding, plasma spraying and thermo-forming. Once processed and shaped, the end-capped liquid crystal oligomers were heated to further polymerize and form liquid crystalline thermosets (LCT). The fully cured products are rubbers above their glass transition temperatures. The resulting thermosets display many properties that are superior to their non-end-capped high molecular weight analogs.

  19. mTOR/p70S6k signalling alteration by Abeta exposure as well as in APP-PS1 transgenic models and in patients with Alzheimer's disease.

    PubMed

    Lafay-Chebassier, Claire; Paccalin, Marc; Page, Guylène; Barc-Pain, Stéphanie; Perault-Pochat, Marie Christine; Gil, Roger; Pradier, Laurent; Hugon, Jacques

    2005-07-01

    In Alzheimer's disease, neuropathological hallmarks include the accumulation of beta-amyloid peptides (Abeta) in senile plaques, phosphorylated tau in neurofibrillary tangles and neuronal death. Abeta is the major aetiological agent according to the amyloid cascade hypothesis. Translational control includes phosphorylation of the kinases mammalian target of rapamycin (mTOR) and p70S6k which modulate cell growth, proliferation and autophagy. It is mainly part of an anti-apoptotic cellular signalling. In this study, we analysed modifications of mTOR/p70S6k signalling in cellular and transgenic models of Alzheimer's disease, as well as in lymphocytes of patients and control individuals. Abeta 1-42 produced a rapid and persistent down-regulation of mTOR/p70S6k phosphorylation in murine neuroblastoma cells associated with caspase 3 activation. Using western blottings, we found that phosphorylated forms of mTOR and p70S6k are decreased in the cortex but not in the cerebellum (devoid of plaques) of double APP/PS1 transgenic mice compared with control mice. These results were confirmed by immunohistochemical methods. Finally, the expression of phosphorylated p70S6k was significantly reduced in lymphocytes of Alzheimer's patients, and levels of phosphorylated p70S6k were statistically correlated with Mini Mental Status Examination (MMSE) scores. Taken together, these findings demonstrate that the mainly anti-apoptotic mTOR/p70S6k signalling is altered in cellular and transgenic models of Alzheimer's disease and in peripheral cells of patients, and could contribute to the pathogenesis of the disease. PMID:15953364

  20. Selection of a potential diagnostic biomarker for HIV infection from a random library of non-biological synthetic peptoid oligomers.

    PubMed

    Gearhart, Tricia L; Montelaro, Ronald C; Schurdak, Mark E; Pilcher, Chris D; Rinaldo, Charles R; Kodadek, Thomas; Park, Yongseok; Islam, Kazi; Yurko, Raymond; Marques, Ernesto T A; Burke, Donald S

    2016-08-01

    Non-biological synthetic oligomers can serve as ligands for antibodies. We hypothesized that a random combinatorial library of synthetic poly-N-substituted glycine oligomers, or peptoids, could represent a random "shape library" in antigen space, and that some of these peptoids would be recognized by the antigen-binding pocket of disease-specific antibodies. We synthesized and screened a one bead one compound combinatorial library of peptoids, in which each bead displayed an 8-mer peptoid with ten possible different amines at each position (10(8) theoretical variants). By screening one million peptoid/beads we found 112 (approximately 1 in 10,000) that preferentially bound immunoglobulins from human sera known to be positive for anti-HIV antibodies. Reactive peptoids were then re-synthesized and rigorously evaluated in plate-based ELISAs. Four peptoids showed very good, and one showed excellent, properties for establishing a sero-diagnosis of HIV. These results demonstrate the feasibility of constructing sero-diagnostic assays for infectious diseases from libraries of random molecular shapes. In this study we sought a proof-of-principle that we could identify a potential diagnostic antibody ligand biomarker for an infectious disease in a random combinatorial library of 100 million peptoids. We believe that this is the first evidence that it is possible to develop sero-diagnostic assays - for any infectious disease - based on screening random libraries of non-biological molecular shapes. PMID:27182050

  1. GeneGenie: optimized oligomer design for directed evolution

    PubMed Central

    Swainston, Neil; Currin, Andrew; Day, Philip J.; Kell, Douglas B.

    2014-01-01

    GeneGenie, a new online tool available at http://www.gene-genie.org, is introduced to support the design and self-assembly of synthetic genes and constructs. GeneGenie allows for the design of oligonucleotide cohorts encoding the gene sequence optimized for expression in any suitable host through an intuitive, easy-to-use web interface. The tool ensures consistent oligomer overlapping melting temperatures, minimizes the likelihood of misannealing, optimizes codon usage for expression in a selected host, allows for specification of forward and reverse cloning sequences (for downstream ligation) and also provides support for mutagenesis or directed evolution studies. Directed evolution studies are enabled through the construction of variant libraries via the optional specification of ‘variant codons’, containing mixtures of bases, at any position. For example, specifying the variant codon TNT (where N is any nucleotide) will generate an equimolar mixture of the codons TAT, TCT, TGT and TTT at that position, encoding a mixture of the amino acids Tyr, Ser, Cys and Phe. This facility is demonstrated through the use of GeneGenie to develop and synthesize a library of enhanced green fluorescent protein variants. PMID:24782527

  2. Oligomer Formation of Tau Protein Hyperphosphorylated in Cells*

    PubMed Central

    Tepper, Katharina; Biernat, Jacek; Kumar, Satish; Wegmann, Susanne; Timm, Thomas; Hübschmann, Sabrina; Redecke, Lars; Mandelkow, Eva-Maria; Müller, Daniel J.; Mandelkow, Eckhard

    2014-01-01

    Abnormal phosphorylation (“hyperphosphorylation”) and aggregation of Tau protein are hallmarks of Alzheimer disease and other tauopathies, but their causative connection is still a matter of debate. Tau with Alzheimer-like phosphorylation is also present in hibernating animals, mitosis, or during embryonic development, without leading to pathophysiology or neurodegeneration. Thus, the role of phosphorylation and the distinction between physiological and pathological phosphorylation needs to be further refined. So far, the systematic investigation of highly phosphorylated Tau was difficult because a reliable method of preparing reproducible quantities was not available. Here, we generated full-length Tau (2N4R) in Sf9 cells in a well defined phosphorylation state containing up to ∼20 phosphates as judged by mass spectrometry and Western blotting with phospho-specific antibodies. Despite the high concentration in living Sf9 cells (estimated ∼230 μm) and high phosphorylation, the protein was not aggregated. However, after purification, the highly phosphorylated protein readily formed oligomers, whereas fibrils were observed only rarely. Exposure of mature primary neuronal cultures to oligomeric phospho-Tau caused reduction of spine density on dendrites but did not change the overall cell viability. PMID:25339173

  3. Cross-linking of glycoprotein oligomers during herpes simplex virus type 1 entry.

    PubMed

    Handler, C G; Cohen, G H; Eisenberg, R J

    1996-09-01

    Herpes simplex virus (HSV) has 10 glycoproteins in its envelope. Glycoprotein B (gB), gC, gD, gH, and gL have been implicated in virus entry. We previously used chemical cross-linking to show that these five glycoproteins were close enough to each other to be cross-linked into homodimeric and hetero-oligomeric forms; hetero-oligomers of gB-gC, gC-gD, gD-gB, gH-gL, gC-gL and gD-gL were found in purified virions. To better understand the roles of these glycoproteins in viral entry, we have modified a standard HSV penetration assay to include cross-linkers. This allowed us to examine changes in associations of viral glycoproteins during the entry process. HSV-1(KOS) was adsorbed at 4 degrees C to human neuroblastoma cells (SY5Y). The temperature was raised to 37 degrees C and cells were treated with cross-linker at various times after the temperature shift. Cytoplasmic extracts were examined by Western blotting (immunoblotting) for viral glycoproteins. We found that (i) as in virus alone, the length and concentration of the cross-linking agent affected the number of specific complexes isolated; (ii) the same glycoprotein patterns found in purified virions were also present after attachment of virions to cells; and (iii) the ability to cross-link HSV glycoproteins changed as virus penetration proceeded, e.g., gB and gD complexes which were present during attachment disappeared with increasing time, and their disappearance paralleled the kinetics of penetration. However, this phenomenon appeared to be selective since it was not observed with gC oligomers. In addition, we examined the cross-linking patterns of gB and gD in null viruses K082 and KOSgD beta. Neither of these mutants, which attach but cannot penetrate, showed changes in glycoprotein cross-linking over time. We speculate that these changes are due to conformational changes which preclude cross-linking or spatial alterations which dissociate the glycoprotein interactions during the penetration events. PMID

  4. Dynamic Conformations of Nucleophosmin (NPM1) at a Key Monomer-Monomer Interface Affect Oligomer Stability and Interactions with Granzyme B

    PubMed Central

    Duan-Porter, Wei D.; Woods, Virgil L.; Maurer, Kimberly D.; Li, Sheng; Rosen, Antony

    2014-01-01

    Nucleophosmin (NPM1) is an abundant, nucleolar tumor antigen with important roles in cell proliferation and putative contributions to oncogenesis. Wild-type NPM1 forms pentameric oligomers through interactions at the amino-terminal core domain. A truncated form of NPM1 found in some hepatocellular carcinoma tissue formed an unusually stable oligomer and showed increased susceptibility to cleavage by granzyme B. Initiation of translation at the seventh methionine generated a protein (M7-NPM) that shared all these properties. We used deuterium exchange mass spectrometry (DXMS) to perform a detailed structural analysis of wild-type NPM1 and M7-NPM, and found dynamic conformational shifts or local “unfolding” at a specific monomer-monomer interface which included the β-hairpin “latch.” We tested the importance of interactions at the β-hairpin “latch” by replacing a conserved tyrosine in the middle of the β-hairpin loop with glutamic acid, generating Y67E-NPM. Y67E-NPM did not form stable oligomers and further, prevented wild-type NPM1 oligomerization in a dominant-negative fashion, supporting the critical role of the β-hairpin “latch” in monomer-monomer interactions. Also, we show preferential cleavage by granzyme B at one of two available aspartates (either D161 or D122) in M7-NPM and Y67E-NPM, whereas wild-type NPM1 was cleaved at both sites. Thus, we observed a correlation between the propensity to form oligomers and granzyme B cleavage site selection in nucleophosmin proteins, suggesting that a small change at an important monomer-monomer interface can affect conformational shifts and impact protein-protein interactions. PMID:25490769

  5. Naturally occurring autoantibodies against Aβ oligomers exhibited more beneficial effects in the treatment of mouse model of Alzheimer's disease than intravenous immunoglobulin.

    PubMed

    Wang, Teng; Xie, Xi-Xiu; Ji, Mei; Wang, Shao-Wei; Zha, Jun; Zhou, Wei-Wei; Yu, Xiao-Lin; Wei, Chen; Ma, Shan; Xi, Zhi-Ying; Pang, Guang-Li; Liu, Rui-Tian

    2016-06-01

    Alzheimer's disease (AD) is characterized by memory loss, intracellular neurofibrillary tangles, and extracellular plaque deposits composed of β-amyloid (Aβ). Previous reports showed that naturally occurring autoantibodies, such as intravenous immunoglobulin (IVIG), benefited patients with moderate-stage AD who carried an APOE-ε4 allele. However, the mechanism underlying the role of IVIG remains unclear. In this study, we identified naturally occurring autoantibodies against Aβ oligomers (NAbs-Aβo), which were purified by Aβ42 oligomer or Cibacron Blue affinity chromatography from IVIG and termed as Oli-NAbs and Blue-NAbs, respectively. Oli-NAbs and Blue-NAbs recognized Aβ42 oligomers or both Aβ40 and 42 oligomers, differently. Both antibodies inhibited Aβ42 aggregation and attenuated Aβ42-induced cytotoxicity. Compared with vehicles, Oli-NAbs, Blue-NAbs and IVIG significantly improved the memory and cognition, and reduced the soluble and oligomeric Aβ levels in APPswe/PS1dE9 transgenic mice. Further investigation showed that Blue-NAbs at increased doses effectively decreased plaque burden and insoluble Aβ levels, whereas Oli-NAbs significantly declined the microgliosis and astrogliosis, as well as the production of proinflammatory cytokines in vivo. Therefore, high levels of these antibodies against oligomeric Aβ40 or Aβ42 were required, correspondingly, to achieve the optimal effect. NAbs-Aβo could be condensed to a high concentration by affinity chromatography and its isolation from IVIG may not interfere with the normal function of conventional IVIG as its concentration is very low. Thus, the isolated NAbs-Aβo as an extra product of plasma required low cost and the enriched NAbs-Aβo may be more feasible than IVIG for the treatment of AD. PMID:26907803

  6. The Reticulon and Dp1/Yop1p Proteins Form Immobile Oligomers in the Tubular Endoplasmic Reticulum*S⃞

    PubMed Central

    Shibata, Yoko; Voss, Christiane; Rist, Julia M.; Hu, Junjie; Rapoport, Tom A.; Prinz, William A.; Voeltz, Gia K.

    2008-01-01

    We recently identified a class of membrane proteins, the reticulons and DP1/Yop1p, which shape the tubular endoplasmic reticulum (ER) in yeast and mammalian cells. These proteins are highly enriched in the tubular portions of the ER and virtually excluded from other regions. To understand how they promote tubule formation, we characterized their behavior in cellular membranes and addressed how their localization in the ER is determined. Using fluorescence recovery after photobleaching, we found that yeast Rtn1p and Yop1p are less mobile in the membrane than normal ER proteins. Sucrose gradient centrifugation and cross-linking analyses show that they form oligomers. Mutants of yeast Rtn1p, which no longer localize exclusively to the tubular ER or are even totally inactive in inducing ER tubules, are more mobile and oligomerize less extensively. The mammalian reticulons and DP1 are also relatively immobile and can form oligomers. The conserved reticulon homology domain that includes the two membrane-embedded segments is sufficient for the localization of the reticulons to the tubular ER, as well as for their diffusional immobility and oligomerization. Finally, ATP depletion in both yeast and mammalian cells further decreases the mobilities of the reticulons and DP1. We propose that oligomerization of the reticulons and DP1/Yop1p is important for both their localization to the tubular domains of the ER and for their ability to form tubules. PMID:18442980

  7. Theoretical investigation of second hyperpolarizability of trans-polyacetylene: Comparison between experimental and theoretical results for small oligomers

    NASA Astrophysics Data System (ADS)

    Andrade, Ageo Meier de; Inacio, Patrícia Loren; Camilo, Alexandre

    2015-12-01

    The development of new conductive polymers nowadays is one of the most important technological areas in materials design. Computational investigation of desired properties in conductive polymers could save financial resources and time, but it is important to choose the methodology that produces good results comparing to experimental results. To verify the prediction of second hyperpolarizability (γ) in oligomers of Trans-Polyacetylene (TPA) by theoretical calculations, a series of semi-empirical, Hartree-Fock (HF), and Density Functional Theory (DFT) calculations were performed and analysed through linear fitting statistical analysis to investigate the accuracy of such theoretical predictions in comparison to the experimental ones. The results showed that HF and DFT methodologies do not describe γ with good accuracy, but the use of diffuse and polarizability functions in HF methodology provided better results than 3-21G and 6-31G functions. It was concluded that RM1 methodology better agrees with γ experimental results for TPA oligomers, and linear fitting statistical analysis is a useful tool to compare experimental and theoretical results.

  8. Amyloid-β oligomers induce synaptic damage via Tau-dependent microtubule severing by TTLL6 and spastin

    PubMed Central

    Zempel, Hans; Luedtke, Julia; Kumar, Yatender; Biernat, Jacek; Dawson, Hana; Mandelkow, Eckhard; Mandelkow, Eva-Maria

    2013-01-01

    Mislocalization and aggregation of Aβ and Tau combined with loss of synapses and microtubules (MTs) are hallmarks of Alzheimer disease. We exposed mature primary neurons to Aβ oligomers and analysed changes in the Tau/MT system. MT breakdown occurs in dendrites invaded by Tau (Tau missorting) and is mediated by spastin, an MT-severing enzyme. Spastin is recruited by MT polyglutamylation, induced by Tau missorting triggered translocalization of TTLL6 (Tubulin-Tyrosine-Ligase-Like-6) into dendrites. Consequences are spine loss and mitochondria and neurofilament mislocalization. Missorted Tau is not axonally derived, as shown by axonal retention of photoconvertible Dendra2-Tau, but newly synthesized. Recovery from Aβ insult occurs after Aβ oligomers lose their toxicity and requires the kinase MARK (Microtubule-Affinity-Regulating-Kinase). In neurons derived from Tau-knockout mice, MTs and synapses are resistant to Aβ toxicity because TTLL6 mislocalization and MT polyglutamylation are prevented; hence no spastin recruitment and no MT breakdown occur, enabling faster recovery. Reintroduction of Tau re-establishes Aβ-induced toxicity in TauKO neurons, which requires phosphorylation of Tau's KXGS motifs. Transgenic mice overexpressing Tau show TTLL6 translocalization into dendrites and decreased MT stability. The results provide a rationale for MT stabilization as a therapeutic approach. PMID:24065130

  9. Theoretical investigation of second hyperpolarizability of trans-polyacetylene: Comparison between experimental and theoretical results for small oligomers.

    PubMed

    de Andrade, Ageo Meier; Inacio, Patrícia Loren; Camilo, Alexandre

    2015-12-28

    The development of new conductive polymers nowadays is one of the most important technological areas in materials design. Computational investigation of desired properties in conductive polymers could save financial resources and time, but it is important to choose the methodology that produces good results comparing to experimental results. To verify the prediction of second hyperpolarizability (γ) in oligomers of Trans-Polyacetylene (TPA) by theoretical calculations, a series of semi-empirical, Hartree-Fock (HF), and Density Functional Theory (DFT) calculations were performed and analysed through linear fitting statistical analysis to investigate the accuracy of such theoretical predictions in comparison to the experimental ones. The results showed that HF and DFT methodologies do not describe γ with good accuracy, but the use of diffuse and polarizability functions in HF methodology provided better results than 3-21G and 6-31G functions. It was concluded that RM1 methodology better agrees with γ experimental results for TPA oligomers, and linear fitting statistical analysis is a useful tool to compare experimental and theoretical results. PMID:26723710

  10. Alzheimer-associated Aβ oligomers impact the central nervous system to induce peripheral metabolic deregulation

    PubMed Central

    Clarke, Julia R; Lyra e Silva, Natalia M; Figueiredo, Claudia P; Frozza, Rudimar L; Ledo, Jose H; Beckman, Danielle; Katashima, Carlos K; Razolli, Daniela; Carvalho, Bruno M; Frazão, Renata; Silveira, Marina A; Ribeiro, Felipe C; Bomfim, Theresa R; Neves, Fernanda S; Klein, William L; Medeiros, Rodrigo; LaFerla, Frank M; Carvalheira, Jose B; Saad, Mario J; Munoz, Douglas P; Velloso, Licio A; Ferreira, Sergio T; De Felice, Fernanda G

    2015-01-01

    Alzheimer's disease (AD) is associated with peripheral metabolic disorders. Clinical/epidemiological data indicate increased risk of diabetes in AD patients. Here, we show that intracerebroventricular infusion of AD-associated Aβ oligomers (AβOs) in mice triggered peripheral glucose intolerance, a phenomenon further verified in two transgenic mouse models of AD. Systemically injected AβOs failed to induce glucose intolerance, suggesting AβOs target brain regions involved in peripheral metabolic control. Accordingly, we show that AβOs affected hypothalamic neurons in culture, inducing eukaryotic translation initiation factor 2α phosphorylation (eIF2α-P). AβOs further induced eIF2α-P and activated pro-inflammatory IKKβ/NF-κB signaling in the hypothalamus of mice and macaques. AβOs failed to trigger peripheral glucose intolerance in tumor necrosis factor-α (TNF-α) receptor 1 knockout mice. Pharmacological inhibition of brain inflammation and endoplasmic reticulum stress prevented glucose intolerance in mice, indicating that AβOs act via a central route to affect peripheral glucose homeostasis. While the hypothalamus has been largely ignored in the AD field, our findings indicate that AβOs affect this brain region and reveal novel shared molecular mechanisms between hypothalamic dysfunction in metabolic disorders and AD. PMID:25617315

  11. The Structure of Gold-Nanoparticle Networks Cross-Linked by Di- and Multifunctional RAFT Oligomers.

    PubMed

    Rossner, Christian; Glatter, Otto; Saldanha, Oliva; Köster, Sarah; Vana, Philipp

    2015-09-29

    Gold nanoparticle (AuNP) network structures featuring particles from the two-phase Brust-Schiffrin synthesis and linear RAFT oligomers of styrene with two and multiple trithiocarbonate (TTC) groups along their backbone have been investigated in detail. Insights into the internal structures of these particle networks could be obtained from small-angle X-ray scattering experiments, showing that primary AuNPs are cross-linked by the employed molecular linker. The extent of AuNP network formation was investigated by means of dynamic light scattering and UV/visible extinction spectroscopy, showing an abrupt attenuation of network formation after a critical degree of polymerization of the cross-linker is exceeded. Analysis of transmission electron micrographs indicated a three-dimensional shape of the particle superstructures, which is evenly filled with the primary AuNPs. From the results obtained in this study, guidelines for the fabrication of nanoparticle networks from the self-assembly with macromolecular cross-linkers are suggested. PMID:26340689

  12. p/n-Polarity of thiophene oligomers in photovoltaic cells: role of molecular vs. supramolecular properties.

    PubMed

    Ghosh, Tanwistha; Gopal, Anesh; Saeki, Akinori; Seki, Shu; Nair, Vijayakumar C

    2015-04-28

    Molecular and supramolecular properties play key roles in the optoelectronic properties and photovoltaic performances of organic materials. In the present work, we show how small changes in the molecular structure affect such properties, which in turn control the intrinsic and fundamental properties such as the p/n-polarity of organic semiconductors in bulk-heterojunction solar cells. Herein, we designed and synthesized two acceptor-donor-acceptor type semiconducting thiophene oligomers end-functionalized with oxazolone/isoxazolone derivatives (OT1 and OT2 respectively). The HOMO-LUMO energy levels of both derivatives were found to be positioned in such a way that they can act as electron acceptors to P3HT and electron donors to PCBM. However, OT1 functions as a donor (with PCBM) and OT2 as an acceptor (with P3HT) in BHJ photovoltaic cells, and their reverse roles results in either no or poor performance of the cells. Detailed studies using UV-vis absorption and fluorescence spectroscopy, time-correlated single photon counting, UV-photoelectron spectroscopy, density functional theory calculations, X-ray diffraction, and thermal gravimetric analysis proved that both molecular and supramolecular properties contributed equally but in a contrasting manner to the abovementioned observation. The obtained results were further validated by flash-photolysis time-resolved microwave conductivity studies which showed an excellent correlation between the structure, property, and device performances of the materials. PMID:25805168

  13. High-Stability, High-Efficiency Organic Monoliths Made of Oligomer Nanoparticles Wrapped in Organic Matrix.

    PubMed

    Soran-Erdem, Zeliha; Erdem, Talha; Gungor, Kivanc; Pennakalathil, Jousheed; Tuncel, Dönüs; Demir, Hilmi Volkan

    2016-05-24

    Oligomer nanoparticles (OL NPs) have been considered unsuitable for solid-state lighting due to their low quantum yields and low temperature stability of their emission. Here, we address these problems by forming highly emissive and stable OL NPs solids to make them applicable in lighting. For this purpose, we incorporated OL NPs into sucrose matrix and then prepared their all-organic monoliths. We show that wrapping the OL NPs in sucrose significantly increases their quantum yield up to 44%, while the efficiency of their dispersion and direct solid-film remain only at ∼6%. We further showed ∼3-fold improved temperature stability of OL NP emission within these monoliths. Our experiments revealed that a physical passivation mechanism is responsible from these improvements. As a proof-of-concept demonstration, we successfully employed these high-stability, high-efficiency monoliths as color converters on a blue LED chip. Considering the improved optical features, low cost, and simplicity of the presented methodology, we believe that this study holds great promise for a ubiquitous use of organic OL NPs in lighting and possibly in other photonic applications. PMID:27149059

  14. Effects of magnesium ions on the stabilization of RNA oligomers of defined structures.

    PubMed Central

    Serra, Martin J; Baird, John D; Dale, Taraka; Fey, Bridget L; Retatagos, Kimberly; Westhof, Eric

    2002-01-01

    Optical melting was used to determine the stabilities of 11 small RNA oligomers of defined secondary structure as a function of magnesium ion concentration. The oligomers included helices composed of Watson-Crick base pairs, GA tandem base pairs, GU tandem base pairs, and loop E motifs (both eubacterial and eukaryotic). The effect of magnesium ion concentration on stability was interpreted in terms of two simple models. The first assumes an uptake of metal ion upon duplex formation. The second assumes nonspecific electrostatic attraction of metal ions to the RNA oligomer. For all oligomers, except the eubacterial loop E, the data could best be interpreted as nonspecific binding of metal ions to the RNAs. The effect of magnesium ions on the stability of the eubacterial loop E was distinct from that seen with the other oligomers in two ways. First, the extent of stabilization by magnesium ions (as measured by either change in melting temperature or free energy) was three times greater than that observed for the other helical oligomers. Second, the presence of magnesium ions produces a doubling of the enthalpy for the melting transition. These results indicate that magnesium ion stabilizes the eubacterial loop E sequence by chelating the RNA specifically. Further, these results on a rather small system shed light on the large enthalpy changes observed upon thermal unfolding of large RNAs like group I introns. It is suggested that parts of those large enthalpy changes observed in the folding of RNAs may be assigned to variations in the hydration states and types of coordinating atoms in some specifically bound magnesium ions and to an increase in the observed cooperativity of the folding transition due to the binding of those magnesium ions coupling the two stems together. Brownian dynamic simulations, carried out to visualize the metal ion binding sites, reveal rather delocalized ionic densities in all oligomers, except for the eubacterial loop E, in which precisely

  15. One-step, regioselective synthesis of up to 50-mers of RNA oligomers by montmorillonite catalysis.

    PubMed

    Huang, Wenhua; Ferris, James P

    2006-07-12

    5'-Nucleotides of A and U with the phosphate activated with 1-methyladenine generate RNA oligomers containing 40-50 monomers in 1 day in reactions catalyzed by montmorillonite. The corresponding monomers of C give oligomers that are 20-25-mers in length after a 9-day reaction. It was not possible to determine the chain lengths of the oligomers of G since they did not give well-defined bands on gel electrophoresis. Co-oligomers of A and U as well as A, U, G, and C were also prepared. The oligo(A)s formed were separated by gel electrophoresis, and the bands of the 7-39-mers were isolated, the 3',5'-phosphodiester bonds were cleaved by RNase T(2), and the terminal phosphate groups were cleaved with alkaline phosphatase. HPLC analysis revealed that the proportions of A(5)'pp(5)'A, A, A(2)'pA, and A(2)'pA(2)'pA formed were almost the same for the long and shorter oligomers. A similar structure analysis performed on the oligo(U)s established that the proportions of U(5)'pp(5)'U, U, U(2)'pU, U(2)'pU(2)'pU, U(2)'pU(2)'pU(2)'pU, and U(2)'pU(2)'pU(2)'pU(2)'pU did not vary with chain length. The structural analysis of the oligomers of A revealed that 74% of the phosphodiester bonds were 3',5'-linked a value slightly greater than 67% observed when imidazole was the activating group. 61% of the bonds in the U oligomers were 3',5'-linked, which is almost 3 times greater than the 20% measured when imidazole was the activating group. The potential significance of these data to the origin and early evolution of life is discussed. PMID:16819887

  16. Solvent free low-melt viscosity imide oligomers and thermosetting polymide composites

    NASA Technical Reports Server (NTRS)

    Chuang, Chun-Hua (Inventor)

    2012-01-01

    .[.This invention relates to the composition and a solvent-free process for preparing novel imide oligomers and polymers specifically formulated with effective amounts of a dianhydride such as 2,3,3',4-biphenyltetra carboxylic dianydride (a-BPDA), at least one aromatic diamine and an endcapped of 4-phenylethynylphthalic anhydride (PEPA) or nadic anhydride to produce imide oligomers that possess a low-melt viscosity of 1-60 poise at 260-280.degree. C. When the imide oligomer melt is cured at about 371.degree. C. in a press or autoclave under 100-500 psi, the melt resulted in a thermoset polyimide having a glass transition temperature (T.sub.g) equal to and above 310.degree. C. A novel feature of this process is that the monomers; namely the dianhydrides, diamines and the endcaps, are melt processable to form imide oligomers at temperatures ranging between 232-280.degree. C. (450-535.degree. F.) without any solvent. These low-melt imide oligomers can be easily processed by resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM) or the resin infusion process with fiber preforms e.g. carbon, glass or quartz preforms to produce polyimide matrix composites with 288-343.degree. C. (550-650.degree. F.) high temperature performance capability..]. .Iadd.This invention relates to compositions and a solvent-free reaction process for preparing imide oligomers and polymers specifically derived from effective amounts of dianhydrides such as 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), at least one aromatic polyamine and an end-cap such as 4-phenylethynyphthalic anhydride (PEPA) or nadic anhydride to produce imide oligomers that possess a low-melt viscosity of 1-60 poise at 260.degree. C.-280.degree. C..Iaddend.

  17. Phosphorodiamidate morpholino oligomers suppress mutant huntingtin expression and attenuate neurotoxicity.

    PubMed

    Sun, Xin; Marque, Leonard O; Cordner, Zachary; Pruitt, Jennifer L; Bhat, Manik; Li, Pan P; Kannan, Geetha; Ladenheim, Ellen E; Moran, Timothy H; Margolis, Russell L; Rudnicki, Dobrila D

    2014-12-01

    Huntington's disease (HD) is a neurodegenerative disorder caused by a CAG trinucleotide repeat expansion in the huntingtin (HTT) gene. Disease pathogenesis derives, at least in part, from the long polyglutamine tract encoded by mutant HTT. Therefore, considerable effort has been dedicated to the development of therapeutic strategies that significantly reduce the expression of the mutant HTT protein. Antisense oligonucleotides (ASOs) targeted to the CAG repeat region of HTT transcripts have been of particular interest due to their potential capacity to discriminate between normal and mutant HTT transcripts. Here, we focus on phosphorodiamidate morpholino oligomers (PMOs), ASOs that are especially stable, highly soluble and non-toxic. We designed three PMOs to selectively target expanded CAG repeat tracts (CTG22, CTG25 and CTG28), and two PMOs to selectively target sequences flanking the HTT CAG repeat (HTTex1a and HTTex1b). In HD patient-derived fibroblasts with expanded alleles containing 44, 77 or 109 CAG repeats, HTTex1a and HTTex1b were effective in suppressing the expression of mutant and non-mutant transcripts. CTGn PMOs also suppressed HTT expression, with the extent of suppression and the specificity for mutant transcripts dependent on the length of the targeted CAG repeat and on the CTG repeat length and concentration of the PMO. PMO CTG25 reduced HTT-induced cytotoxicity in vitro and suppressed mutant HTT expression in vivo in the N171-82Q transgenic mouse model. Finally, CTG28 reduced mutant HTT expression and improved the phenotype of Hdh(Q7/Q150) knock-in HD mice. These data demonstrate the potential of PMOs as an approach to suppressing the expression of mutant HTT. PMID:25035419

  18. Computational design of organometallic oligomers featuring 1,3-metal-carbon bonding and planar tetracoordinate carbon atoms.

    PubMed

    Zhao, Xue-Feng; Yuan, Cai-Xia; Wang, Xiang; Li, Jia-Jia; Wu, Yan-Bo; Wang, Xiaotai

    2016-01-15

    Density functional theory computations (B3LYP) have been used to explore the chemistry of titanium-aromatic carbon "edge complexes" with 1,3-metal-carbon (1,3-MC) bonding between Ti and planar tetracoordinate Cβ . The titanium-coordinated, end-capping chlorides are replaced with OH or SH groups to afford two series of difunctional monomers that can undergo condensation to form oxide- and sulfide-bridged oligomers. The sulfide-linked oligomers have less molecular strain and are more exergonic than the corresponding oxide-linked oligomers. The HOMO-LUMO gap of the oligomers varies with their composition and decreases with growing oligomer chain. This theoretical study is intended to enrich 1,3-MC bonding and planar tetracoordinate carbon chemistry and provide interesting ideas to experimentalists. Organometallic complexes with the TiE2 (E = OH and SH) decoration on the edge of aromatic hydrocarbons have been computationally designed, which feature 1,3-metal-carbon (1,3-MC) bonding between titanium and planar tetracoordinate β-carbon. Condensation of these difunctional monomers by eliminating small molecules (H2O and H2S) produce chain-like oligomers. The HOMO-LUMO gaps of the oligomers decreases with growing oligomer chain, a trend that suggests possible semiconductor properties for oligomers with longer chains. PMID:26399226

  19. Synthetic Aβ oligomers (Aβ(1-42) globulomer) modulate presynaptic calcium currents: prevention of Aβ-induced synaptic deficits by calcium channel blockers.

    PubMed

    Hermann, David; Mezler, Mario; Müller, Michaela K; Wicke, Karsten; Gross, Gerhard; Draguhn, Andreas; Bruehl, Claus; Nimmrich, Volker

    2013-02-28

    Alzheimer's disease is accompanied by increased brain levels of soluble amyloid-β (Aβ) oligomers. It has been suggested that oligomers directly impair synaptic function, thereby causing cognitive deficits in Alzheimer's disease patients. Recently, it has been shown that synthetic Aβ oligomers directly modulate P/Q-type calcium channels, possibly leading to excitotoxic cascades and subsequent synaptic decline. Using whole-cell recordings we studied the modulation of recombinant presynaptic calcium channels in HEK293 cells after application of a stable Aβ oligomer preparation (Aβ1-42 globulomer). Aβ globulomer shifted the half-activation voltage of P/Q-type and N-type calcium channels to more hyperpolarized values (by 11.5 and 7.5 mV). Application of non-aggregated Aβ peptides had no effect. We then analyzed the potential of calcium channel blockers to prevent Aβ globulomer-induced synaptic decline in hippocampal slice cultures. Specific block of P/Q-type or N-type calcium channels with peptide toxins completely reversed Aβ globulomer-induced deficits in glutamatergic neurotransmission. Two state-dependent low molecular weight P/Q-type and N-type calcium channel blockers also protected neurons from Aβ-induced alterations. On the contrary, inhibition of L-type calcium channels failed to reverse the deficit. Our data show that Aβ globulomer directly modulates recombinant P/Q-type and N-type calcium channels in HEK293 cells. Block of presynaptic calcium channels with both state-dependent and state-independent modulators can reverse Aβ-induced functional deficits in synaptic transmission. These findings indicate that presynaptic calcium channel blockers may be a therapeutic strategy for the treatment of Alzheimer's disease. PMID:23376566

  20. Oligomers matrix-assisted dispersion of high content of carbon nanotubes into monolithic column for online separation and enrichment of proteins from complex biological samples.

    PubMed

    Zhou, Chanyuan; Du, Zhuo; Li, Gongke; Zhang, Yukui; Cai, Zongwei

    2013-10-01

    In this work, a new oligomer matrix-assisted dispersion (OMAD) method for the preparation of homogeneous dispersion of multi-walled carbon nanotubes (MWNTs) incorporated monolithic column was developed. Oligomers matrix as a scaffold could allow MWNTs to entangle with it instead of self-aggregation, so the MWNTs remain in the polymer network followed by in situ self-solidification. The OMAD method not only greatly enlarged the BET surface area of MWNTs incorporated monolithic column from 13.8 m(2) g(-1) to 85.5 m(2) g(-1) without a significant effect on the surface chemistry of the MWNTs, but also improved the dispersion of MWNTs making its content up to 5 wt% (with respect to monomers). The synthesized materials combine the favorable attributes of both high permeability and large surface area, making them excellent candidates for on-line separation and enrichment of proteins. The oligomer matrix-assisted dispersion MWNTs incorporated monolithic columns (OMAD-MMC) exhibited higher enrichment factors and the adsorption capacity is about 5-fold for basic proteins compared with MWNTs incorporated monolithic columns (MMC) prepared by the conventional in situ polymerization. The practical application of OMAD-MMC was proven by selective extraction of hemoglobin in human whole blood samples with SDS-PAGE. On the basis of the results, OMAD as a simple and effective method for dispersion high content MWNTs into monolithic columns shows great promise. PMID:23917344

  1. Aβ self-association and adsorption on a hydrophobic nanosurface: competitive effects and the detection of small oligomers via electrical response.

    PubMed

    Jana, Asis K; Sengupta, Neelanjana

    2015-01-14

    Treatment of Alzheimer's disease (AD) is impeded by the lack of effective early diagnostic methods. Small, soluble Aβ globulomers play a major role in AD neurotoxicity, and detecting their presence in aqueous fluids could lead to suitable sensors. We evaluate the adsorption behavior of small Aβ oligomers on the surface of a single walled carbon nanotube of high curvature. While the intrinsic self-assembly propensity of Aβ is markedly hindered by adsorption, the oligomeric units show high degrees of surface immobilization. Immobilized complexes are capable of oligomeric growth, but with a shifted monomer-oligomer equilibrium compared to the free states. In the presence of an ionic solution and suitable external electric fields, magnitudes of the current blockades are found to be sensitive to the oligomeric number of the adsorbed complex. However, this sensitivity gradually diminishes with increasing oligomeric size. The results provide a proof-of-concept basis for further investigations in the design of sensors for detecting the toxic small oligomers of Aβ. PMID:25407676

  2. Disrupting Self-Assembly and Toxicity of Amyloidogenic Protein Oligomers by “Molecular Tweezers” - from the Test Tube to Animal Models

    PubMed Central

    Attar, Aida; Bitan, Gal

    2014-01-01

    Despite decades of research, therapy for diseases caused by abnormal protein folding and aggregation (amyloidoses) is limited to treatment of symptoms and provides only temporary and moderate relief to sufferers. The failure in developing successful disease-modifying drugs for amyloidoses stems from the nature of the targets for such drugs – primarily oligomers of amyloidogenic proteins, which are distinct from traditional targets, such as enzymes or receptors. The oligomers are metastable, do not have well-defined structures, and exist in dynamically changing mixtures. Therefore, inhibiting the formation and toxicity of these oligomers likely will require out-of-the-box thinking and novel strategies. We review here the development of a strategy based on targeting the combination of hydrophobic and electrostatic interactions that are key to the assembly and toxicity of amyloidogenic proteins using lysine (K)-specific “molecular tweezers” (MTs). Our discussion includes a survey of the literature demonstrating the important role of K residues in the assembly and toxicity of amyloidogenic proteins and the development of a lead MT derivative called CLR01, from an inhibitor of protein aggregation in vitro to a drug candidate showing effective amelioration of disease symptoms in animal models of Alzheimer’s and Parkinson’s diseases. PMID:23859557

  3. Synthetic amyloid-β oligomers impair long-term memory independently of cellular prion protein

    PubMed Central

    Balducci, Claudia; Beeg, Marten; Stravalaci, Matteo; Bastone, Antonio; Sclip, Alessandra; Biasini, Emiliano; Tapella, Laura; Colombo, Laura; Manzoni, Claudia; Borsello, Tiziana; Chiesa, Roberto; Gobbi, Marco; Salmona, Mario; Forloni, Gianluigi

    2010-01-01

    Inability to form new memories is an early clinical sign of Alzheimer’s disease (AD). There is ample evidence that the amyloid-β (Aβ) peptide plays a key role in the pathogenesis of this disorder. Soluble, bio-derived oligomers of Aβ are proposed as the key mediators of synaptic and cognitive dysfunction, but more tractable models of Aβ−mediated cognitive impairment are needed. Here we report that, in mice, acute intracerebroventricular injections of synthetic Aβ1–42 oligomers impaired consolidation of the long-term recognition memory, whereas mature Aβ1–42 fibrils and freshly dissolved peptide did not. The deficit induced by oligomers was reversible and was prevented by an anti-Aβ antibody. It has been suggested that the cellular prion protein (PrPC) mediates the impairment of synaptic plasticity induced by Aβ. We confirmed that Aβ1–42 oligomers interact with PrPC, with nanomolar affinity. However, PrP-expressing and PrP knock-out mice were equally susceptible to this impairment. These data suggest that Aβ1–42 oligomers are responsible for cognitive impairment in AD and that PrPC is not required. PMID:20133875

  4. Indirect detection of ethylene glycol oligomers using a contactless conductivity detector in capillary liquid chromatography.

    PubMed

    Takeuchi, Toyohide; Sedyohutomo, Anang; Lim, Lee Wah

    2009-07-01

    Ethylene glycol oligomers were visualized by indirect conductimetric detection based on dilution of the mobile phase due to the analytes. A high electrical conductivity background was maintained by the addition of 5 mM sodium nitrate in the mobile phase, and the analytes were visualized by decreases in the background when they eluted. A capacitively coupled contactless conductivity detector was convenient to monitor effluents from the microcolumn with minimum extra-column band broadening. The signals as negative peaks were linear to the concentration of the analytes, and a concentration detection limit of 0.025% was achieved for tetraethylene glycol at S/N=3, corresponding to the mass detection limit of 38 ng for 0.15 microl injection. The logarithm of the retention factor of ethylene glycol oligomers was linear to the degree of polymerization (DP) as well as to the acetonitrile composition in the mobile phase. These situations allowed us to estimate the DP of eluted ethylene glycol oligomers by using a few oligomers with known DP. The dynamic reserve, defined as the ratio of the background to its noise level achieved under the present conditions, was 2.3 x 10(5) which was much larger than that achieved by UV absorption detection. The present method was applied to profile ethylene glycol oligomers contained in commercially available PEG reagents. PMID:19609021

  5. Nitrogen Containing Organic Compounds and Oligomers in Secondary Organic Aerosol Formed by Photooxidation of Isoprene

    SciTech Connect

    Nguyen, Tran B.; Laskin, Julia; Laskin, Alexander; Nizkorodov, Serguei

    2011-07-06

    Electrospray ionization high-resolution mass spectrometry (ESI HR-MS) was used to probe molecular structures of oligomers in secondary organic aerosol (SOA) generated in laboratory experiments on isoprene photooxidation at low- and high-NOx conditions. Up to 80-90% of the observed products are oligomers and up to 33% are nitrogen-containing organic compounds (NOC). We observe oligomers with up to 8 monomer units in length. Tandem mass spectrometry (MSn) confirms NOC compounds are organic nitrates and elucidates plausible chemical building blocks contributing to oligomer formation. Most organic nitrates are comprised of methylglyceric acid units. Other important multifunctional C2-C5 monomer units are identified including methylglyoxal, hydroxyacetone, hydroxyacetic acid, glycolaldehyde, and 2-methyltetrols. The majority of the NOC oligomers contain only one nitrate moiety resulting in a low average N:C ratio of 0.019. Average O:C ratios of the detected SOA compounds are 0.54 under the low-NOx conditions and 0.83 under the high-NOx conditions. Our results underscore the importance of isoprene photooxidation as a source of NOC in organic particulate matter.

  6. Mitochondrial Ca2+ Overload Underlies Aβ Oligomers Neurotoxicity Providing an Unexpected Mechanism of Neuroprotection by NSAIDs

    PubMed Central

    Sanz-Blasco, Sara; Valero, Ruth A.; Rodríguez-Crespo, Ignacio; Villalobos, Carlos; Núñez, Lucía

    2008-01-01

    Dysregulation of intracellular Ca2+ homeostasis may underlie amyloid β peptide (Aβ) toxicity in Alzheimer's Disease (AD) but the mechanism is unknown. In search for this mechanism we found that Aβ1–42 oligomers, the assembly state correlating best with cognitive decline in AD, but not Aβ fibrils, induce a massive entry of Ca2+ in neurons and promote mitochondrial Ca2+ overload as shown by bioluminescence imaging of targeted aequorin in individual neurons. Aβ oligomers induce also mitochondrial permeability transition, cytochrome c release, apoptosis and cell death. Mitochondrial depolarization prevents mitochondrial Ca2+ overload, cytochrome c release and cell death. In addition, we found that a series of non-steroidal anti-inflammatory drugs (NSAIDs) including salicylate, sulindac sulfide, indomethacin, ibuprofen and R-flurbiprofen depolarize mitochondria and inhibit mitochondrial Ca2+ overload, cytochrome c release and cell death induced by Aβ oligomers. Our results indicate that i) mitochondrial Ca2+ overload underlies the neurotoxicity induced by Aβ oligomers and ii) inhibition of mitochondrial Ca2+ overload provides a novel mechanism of neuroprotection by NSAIDs against Aβ oligomers and AD. PMID:18648507

  7. Methods for the Specific Detection and Quantitation of Amyloid-β Oligomers in Cerebrospinal Fluid.

    PubMed

    Schuster, Judith; Funke, Susanne Aileen

    2016-05-01

    Protein misfolding and aggregation are fundamental features of the majority of neurodegenerative diseases, like Alzheimer's disease (AD), Parkinson's disease, frontotemporal dementia, and prion diseases. Proteinaceous deposits in the brain of the patient, e.g., amyloid plaques consisting of the amyloid-β (Aβ) peptide and tangles composed of tau protein, are the hallmarks of AD. Soluble oligomers of Aβ and tau play a fundamental role in disease progression, and specific detection and quantification of the respective oligomeric proteins in cerebrospinal fluid may provide presymptomatically detectable biomarkers, paving the way for early diagnosis or even prognosis. Several studies on the development of techniques for the specific detection of Aβ oligomers were published, but some of the existing tools do not yet seem to be satisfactory, and the study results are contradicting. The detection of oligomers is challenging due to their polymorphous and unstable nature, their low concentration, and the presence of competing proteins and Aβ monomers in body fluids. Here, we present an overview of the current state of the development of methods for Aβ oligomer specific detection and quantitation. The methods are divided in the three subgroups: (i) enzyme linked immunosorbent assays (ELISA), (ii) methods for single oligomer detection, and (iii) others, which are mainly biosensor based methods. PMID:27163804

  8. Solvent Free Low-Melt Viscosity Imide Oligomers And Thermosetting Polyimide Composites

    NASA Technical Reports Server (NTRS)

    Chuang, CHun-Hua (Inventor)

    2006-01-01

    This invention relates to the composition and a solvent-free process for preparing novel imide oligomers and polymers specifically formulated with effective amounts of a dianhydride such as 2,3,3',4-biphenyltetra carboxylic dianydride (a-BPDA), at least one aromatic diamine' and an endcapped of 4-phenylethynylphthalic anhydride (PEPA) or nadic anhydride to produce imide oligomers that possess a low-melt viscosity of 1-60 poise at 260-280" C. When the imide oligomer melt is cured at about 371 C. in a press or autoclave under 100-500 psi, the melt resulted in a thermoset polyimide having a glass transition temperature (T(sub g)) equal to and above 310 C. A novel feature of this process is that the monomers; namely the dianhydrides, diamines and the endcaps, are melt processable to form imide oligomers at temperatures ranging between 232-280 C. (450-535 F) without any solvent. These low-melt imide oligomers can be easily processed by resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM) or the resin infusion process with fiber preforms e.g. carbon, glass or quartz preforms to produce polyimide matrix composites with 288-343C (550-650 F) high temperature performance capability.

  9. Parametrization of the Gay-Berne potential for conjugated oligomer with a high aspect ratio

    NASA Astrophysics Data System (ADS)

    Lee, Cheng K.; Hua, Chi C.; Chen, Show A.

    2010-08-01

    The Gay-Berne (GB) potential has been a popular semiempirical model for describing the short-range intermolecular forces for a wide variety of aspherical molecules, including liquid crystals and anisotropic colloids, with generally small molecular dimensions and low aspect ratios (<5). This study evaluates the parametrization of the GB potential for a high-aspect-ratio (=10) oligomer belonging to a model conjugated polymer. We elaborate that the semiflexibility associated with a large oligomer species demands a variant umbrella-sampling scheme in establishing the potentials of mean force (PMFs) for four pair ellipsoid arrangements typically utilized to parametrize the GB potential. The model ellipsoid so constructed is shown to capture the PMFs of essential intermediate arrangements as well, and, according to the results of simplex optimizations, recommendations are given for the minimum set of parameters to be included in the optimization of a large oligomer or particulate species. To further attest the parametrized GB potential, the coarse-grained (CG) Monte Carlo simulations employing the GB potential and the back-mapped, full-atom atomistic molecular dynamics (AMD) simulations were performed for a dense oligomer system at two representative system temperatures. The results indicated that the CG simulations can capture, with exceptional computational efficiency, the AMD predictions with good thermal transferability. In future perspectives, we remark on potential applications to construct efficient, parameter-free CG models for capturing fundamental material properties of large oligomer/particulate species as well as long-chain conjugated polymers.

  10. Sequestration of toxic oligomers by HspB1 as a cytoprotective mechanism.

    PubMed

    Ojha, Juhi; Masilamoni, Gunasingh; Dunlap, David; Udoff, Ross A; Cashikar, Anil G

    2011-08-01

    Small heat shock proteins (sHsps) are molecular chaperones that protect cells from cytotoxic effects of protein misfolding and aggregation. HspB1, an sHsp commonly associated with senile plaques in Alzheimer's disease (AD), prevents the toxic effects of Aβ aggregates in vitro. However, the mechanism of this chaperone activity is poorly understood. Here, we observed that in two distinct transgenic mouse models of AD, mouse HspB1 (Hsp25) localized to the penumbral areas of plaques. We have demonstrated that substoichiometric amounts of human HspB1 (Hsp27) abolish the toxicity of Aβ oligomers on N2a (mouse neuroblastoma) cells. Using biochemical methods, spectroscopy, light scattering, and microscopy methods, we found that HspB1 sequesters toxic Aβ oligomers and converts them into large nontoxic aggregates. HspB1 was overexpressed in N2a cells in response to treatment with Aβ oligomers. Cultured neurons from HspB1-deficient mice were more sensitive to oligomer-mediated toxicity than were those from wild-type mice. Our results suggest that sequestration of oligomers by HspB1 constitutes a novel cytoprotective mechanism of proteostasis. Whether chaperone-mediated cytoprotective sequestration of toxic aggregates may bear clues to plaque deposition and may have potential therapeutic implications must be investigated in the future. PMID:21670152

  11. Prefibrillar transthyretin oligomers and cold stored native tetrameric transthyretin are cytotoxic in cell culture

    SciTech Connect

    Soergjerd, Karin; Klingstedt, Therese; Lindgren, Mikael; Kagedal, Katarina; Hammarstroem, Per

    2008-12-26

    Recent studies suggest that soluble, oligomeric species, which are intermediates in the fibril formation process in amyloid disease, might be the key species in amyloid pathogenesis. Soluble oligomers of human wild type transthyretin (TTR) were produced to elucidate oligomer properties. Employing ThT fluorescence, time-resolved fluorescence anisotropy of pyrene-labeled TTR, chemical cross-linking, and electron microscopy we demonstrated that early formed soluble oligomers (within minutes) from A-state TTR comprised on the average 20-30 TTR monomers. When administered to neuroblastoma cells these early oligomers proved highly cytotoxic and induced apoptosis after 48 h of incubation. More mature fibrils (>24 h of fibrillation) were non-toxic. Surprisingly, we also found that native tetrameric TTR, when purified and stored under cold conditions (4 deg. C) was highly cytotoxic. The effect could be partially restored by increasing the temperature of the protein. The cytotoxic effects of native tetrameric TTR likely stems from a hitherto unexplored low temperature induced rearrangement of the tetramer conformation that possibly is related to the conformation of misfolded TTR in amyloigogenic oligomers.

  12. Parametrization of the Gay-Berne potential for conjugated oligomer with a high aspect ratio.

    PubMed

    Lee, Cheng K; Hua, Chi C; Chen, Show A

    2010-08-14

    The Gay-Berne (GB) potential has been a popular semiempirical model for describing the short-range intermolecular forces for a wide variety of aspherical molecules, including liquid crystals and anisotropic colloids, with generally small molecular dimensions and low aspect ratios (<5). This study evaluates the parametrization of the GB potential for a high-aspect-ratio (=10) oligomer belonging to a model conjugated polymer. We elaborate that the semiflexibility associated with a large oligomer species demands a variant umbrella-sampling scheme in establishing the potentials of mean force (PMFs) for four pair ellipsoid arrangements typically utilized to parametrize the GB potential. The model ellipsoid so constructed is shown to capture the PMFs of essential intermediate arrangements as well, and, according to the results of simplex optimizations, recommendations are given for the minimum set of parameters to be included in the optimization of a large oligomer or particulate species. To further attest the parametrized GB potential, the coarse-grained (CG) Monte Carlo simulations employing the GB potential and the back-mapped, full-atom atomistic molecular dynamics (AMD) simulations were performed for a dense oligomer system at two representative system temperatures. The results indicated that the CG simulations can capture, with exceptional computational efficiency, the AMD predictions with good thermal transferability. In future perspectives, we remark on potential applications to construct efficient, parameter-free CG models for capturing fundamental material properties of large oligomer/particulate species as well as long-chain conjugated polymers. PMID:20707586

  13. RPS23RG1 reduces Aβ oligomer-induced synaptic and cognitive deficits

    PubMed Central

    Yan, Li; Chen, Yaomin; Li, Wubo; Huang, Xiumei; Badie, Hedieh; Jian, Fan; Huang, Timothy; Zhao, Yingjun; Cohen, Stanley N.; Li, Limin; Zhang, Yun-wu; Luo, Huanmin; Tu, Shichun; Xu, Huaxi

    2016-01-01

    Alzheimer’s disease (AD) is the most common form of dementia in the elderly. It is generally believed that β-amyloidogenesis, tau-hyperphosphorylation, and synaptic loss underlie cognitive decline in AD. Rps23rg1, a functional retroposed mouse gene, has been shown to reduce Alzheimer’s β-amyloid (Aβ) production and tau phosphorylation. In this study, we have identified its human homolog, and demonstrated that RPS23RG1 regulates synaptic plasticity, thus counteracting Aβ oligomer (oAβ)-induced cognitive deficits in mice. The level of RPS23RG1 mRNA is significantly lower in the brains of AD compared to non-AD patients, suggesting its potential role in the pathogenesis of the disease. Similar to its mouse counterpart, human RPS23RG1 interacts with adenylate cyclase, activating PKA/CREB, and inhibiting GSK-3. Furthermore, we show that human RPS23RG1 promotes synaptic plasticity and offsets oAβ-induced synaptic loss in a PKA-dependent manner in cultured primary neurons. Overexpression of Rps23rg1 in transgenic mice consistently prevented oAβ-induced PKA inactivation, synaptic deficits, suppression of long-term potentiation, and cognitive impairment as compared to wild type littermates. Our study demonstrates that RPS23RG1 may reduce the occurrence of key elements of AD pathology and enhance synaptic functions to counteract oAβ-induced synaptic and cognitive deficits in AD. PMID:26733416

  14. The pilus usher controls protein interactions via domain masking and is functional as an oligomer

    SciTech Connect

    Werneburg, Glenn T.; Li, Huilin; Henderson, Nadine S.; Portnoy, Erica B.; Sarowar, Samema; Hultgren, Scott J.; Thanassi, David G.

    2015-06-08

    The chaperone/usher (CU) pathway is responsible for biogenesis of organelles termed pili or fimbriae in Gram-negative bacteria. Type 1 pili expressed by uropathogenic Escherichia coli are prototypical structures assembled by the CU pathway. Assembly and secretion of pili by the CU pathway requires a dedicated periplasmic chaperone and a multidomain outer membrane protein termed the usher (FimD). We show that the FimD C-terminal domains provide the high-affinity substrate binding site, but that these domains are masked in the resting usher. Domain masking requires the FimD plug domain, which served as a central switch controlling usher activation. In addition, we demonstrate that usher molecules can act in trans for pilus biogenesis, providing conclusive evidence for a functional usher oligomer. These results reveal mechanisms by which molecular machines such as the usher regulate and harness protein-protein interactions, and suggest that ushers may interact in a cooperative manner during pilus assembly in bacteria.

  15. The pilus usher controls protein interactions via domain masking and is functional as an oligomer

    DOE PAGESBeta

    Werneburg, Glenn T.; Li, Huilin; Henderson, Nadine S.; Portnoy, Erica B.; Sarowar, Samema; Hultgren, Scott J.; Thanassi, David G.

    2015-06-08

    The chaperone/usher (CU) pathway is responsible for biogenesis of organelles termed pili or fimbriae in Gram-negative bacteria. Type 1 pili expressed by uropathogenic Escherichia coli are prototypical structures assembled by the CU pathway. Assembly and secretion of pili by the CU pathway requires a dedicated periplasmic chaperone and a multidomain outer membrane protein termed the usher (FimD). We show that the FimD C-terminal domains provide the high-affinity substrate binding site, but that these domains are masked in the resting usher. Domain masking requires the FimD plug domain, which served as a central switch controlling usher activation. In addition, we demonstratemore » that usher molecules can act in trans for pilus biogenesis, providing conclusive evidence for a functional usher oligomer. These results reveal mechanisms by which molecular machines such as the usher regulate and harness protein-protein interactions, and suggest that ushers may interact in a cooperative manner during pilus assembly in bacteria.« less

  16. The mechanism by which influenza A virus nucleoprotein forms oligomers and binds RNA

    SciTech Connect

    Ye, Qiaozhen; Krug, Robert M.; Tao, Yizhi Jane

    2006-12-06

    Influenza A viruses pose a serious threat to world public health, particularly the currently circulating avian H5N1 viruses. The influenza viral nucleoprotein forms the protein scaffold of the helical genomic ribonucleoprotein complexes, and has a critical role in viral RNA replication. Here we report a 3.2 Angstrom crystal structure of this nucleoprotein, the overall shape of which resembles a crescent with a head and a body domain, with a protein fold different compared with that of the rhabdovirus nucleoprotein. Oligomerization of the influenza virus nucleoprotein is mediated by a flexible tail loop that is inserted inside a neighboring molecule. This flexibility in the tail loop enables the nucleoprotein to form loose polymers as well as rigid helices, both of which are important for nucleoprotein functions. Single residue mutations in the tail loop result in the complete loss of nucleoprotein oligomerization. An RNA-binding groove, which is found between the head and body domains at the exterior of the nucleoprotein oligomer, is lined with highly conserved basic residues widely distributed in the primary sequence. The nucleoprotein structure shows that only one of two proposed nuclear localization signals are accessible, and suggests that the body domain of nucleoprotein contains the binding site for the viral polymerase. Our results identify the tail loop binding pocket as a potential target for antiviral development.

  17. Global styrene oligomers monitoring as new chemical contamination from polystyrene plastic marine pollution.

    PubMed

    Kwon, Bum Gun; Koizumi, Koshiro; Chung, Seon-Yong; Kodera, Yoichi; Kim, Jong-Oh; Saido, Katsuhiko

    2015-12-30

    Polystyrene (PS) plastic marine pollution is an environmental concern. However, a reliable and objective assessment of the scope of this problem, which can lead to persistent organic contaminants, has yet to be performed. Here, we show that anthropogenic styrene oligomers (SOs), a possible indicator of PS pollution in the ocean, are found globally at concentrations that are higher than those expected based on the stability of PS. SOs appear to persist to varying degrees in the seawater and sand samples collected from beaches around the world. The most persistent forms are styrene monomer, styrene dimer, and styrene trimer. Sand samples from beaches, which are commonly recreation sites, are particularly polluted with these high SOs concentrations. This finding is of interest from both scientific and public perspectives because SOs may pose potential long-term risks to the environment in combination with other endocrine disrupting chemicals. From SOs monitoring results, this study proposes a flow diagram for SOs leaching from PS cycle. Using this flow diagram, we conclude that SOs are global contaminants in sandy beaches around the world due to their broad spatial distribution. PMID:26218303

  18. Characterization of Prefibrillar Tau Oligomers in Vitro and in Alzheimer Disease*

    PubMed Central

    Patterson, Kristina R.; Remmers, Christine; Fu, Yifan; Brooker, Sarah; Kanaan, Nicholas M.; Vana, Laurel; Ward, Sarah; Reyes, Juan F.; Philibert, Keith; Glucksman, Marc J.; Binder, Lester I.

    2011-01-01

    Neurofibrillary tangles, composed of insoluble aggregates of the microtubule-associated protein Tau, are a pathological hallmark of Alzheimer disease (AD) and other tauopathies. However, recent evidence indicates that neuronal dysfunction precedes the formation of these insoluble fibrillar deposits, suggesting that earlier prefibrillar Tau aggregates may be neurotoxic. To determine the composition of these aggregates, we have employed a photochemical cross-linking technique to examine intermolecular interactions of full-length Tau in vitro. Using this method, we demonstrate that dimerization is an early event in the Tau aggregation process and that these dimers self-associate to form larger oligomeric aggregates. Moreover, using these stabilized Tau aggregates as immunogens, we generated a monoclonal antibody that selectively recognizes Tau dimers and higher order oligomeric aggregates but shows little reactivity to Tau filaments in vitro. Immunostaining indicates that these dimers/oligomers are markedly elevated in AD, appearing in early pathological inclusions such as neuropil threads and pretangle neurons as well as colocalizing with other early markers of Tau pathogenesis. Taken as a whole, the work presented herein demonstrates the existence of alternative Tau aggregates that precede formation of fibrillar Tau pathologies and raises the possibility that these hierarchical oligomeric forms of Tau may contribute to neurodegeneration. PMID:21550980

  19. Synthesis of Dicyclopentadiene Oligomer Over Nanoporous Al-MCM-41 Catalysts.

    PubMed

    Park, Eunseo; Kim, Jinhan; Yim, Jin-Heong; Han, Jeongsik; Kwon, Tae Soo; Park, Y K; Jeon, Jong-Ki

    2016-05-01

    One step reaction composed of DCPD oligomerization and DCPD oligomer isomerization was investigated over nanoporous Al-MCM-41 catalysts. The effects of aluminum grafting over MCM-41 on the catalyst characteristics were studied with respect to the synthesis of TCPD isomer. Physical and chemical properties of the catalysts were analyzed by N2 adsorption, temperature-programmed desorption of ammonia, and infrared spectroscopy of adsorbed pyridine. The overall number of acid sites as well as the number of Lewis acid sites increased with increasing of aluminum content over MCM-41. When utilizing MCM-41 and Al-MCM-41 as the catalyst, DCPD oligomerization reaction activity greatly increased compared to the thermal reaction. The highest TCPD isomer selectivity over the Al-MCM-41 catalyst with the highest aluminum content could be ascribed to the largest amount of acid sites. This study showed an increased level of TCPD isomer selectivity by an increasing level of Lewis acid sites through aluminum addition over MCM-41. PMID:27483783

  20. Optical properties of chiral three-dimensional plasmonic oligomers at the onset of charge-transfer plasmons.

    PubMed

    Hentschel, Mario; Wu, Lin; Schäferling, Martin; Bai, Ping; Li, Er Ping; Giessen, Harald

    2012-11-27

    We demonstrate strong chiral optical response in three-dimensional chiral nanoparticle oligomers in the wavelength regime between 700 and 3500 nm. We show in experiment and simulation that this broad-band response occurs at the onset of charge transfer between the individual nanoparticles. The ohmic contact causes a strong red shift of the fundamental mode, while the geometrical shape of the resulting fused particles still allows for an efficient excitation of higher order modes. Calculated spectra and field distributions confirm our interpretation and show a number of interacting plasmonic modes. Our results deepen the understanding of the chiral optical response in complex chiral plasmonic nanostructures and pave the road toward broad-band chiral optical devices with strong responses, for example, for chiral plasmon rulers or sensing applications. PMID:23078518

  1. Soluble androgen receptor oligomers underlie pathology in a mouse model of spinobulbar muscular atrophy.

    PubMed

    Li, Mei; Chevalier-Larsen, Erica S; Merry, Diane E; Diamond, Marc I

    2007-02-01

    In polyglutamine diseases such as X-linked spinobulbar muscular atrophy (SBMA), it is unknown whether the toxic form of the protein is an insoluble or soluble aggregate or a monomer. We have addressed this question by studying a full-length androgen receptor (AR) mouse model of SBMA. We used biochemistry and atomic force microscopy to immunopurify oligomers soluble after ultracentrifugation that are comprised of a single approximately 50-kDa N-terminal polyglutamine-containing AR fragment. AR oligomers appeared several weeks prior to symptom onset, were distinct and temporally dissociated from intranuclear inclusions, and disappeared rapidly after castration, which halts disease. This is the first demonstration of soluble AR oligomers in vivo and suggests that they underlie neurodegeneration in SBMA. PMID:17121819

  2. Mitochondrial oligomers boost glycolysis in cancer stem cells to facilitate blebbishield-mediated transformation after apoptosis

    PubMed Central

    Jinesh, GG; Molina, JR; Huang, L; Laing, NM; Mills, GB; Bar-Eli, M; Kamat, AM

    2016-01-01

    Apoptosis culminates in secondary necrosis due to lack of ATP. Cancer stem cells form spheres after apoptosis by evoking the blebbishield emergency program. Hence, determining how blebbishields avoid secondary necrosis is crucial. Here we demonstrate that N-Myc and VEGFR2 control transformation from blebbishields, during which oligomers of K-Ras, p27, BAD, Bax, and Bak boost glycolysis to avoid secondary necrosis. Non-apoptotic cancer cells also utilize oligomers to boost glycolysis, which differentiates the glycolytic function of oligomers from their apoptotic action. Smac mimetic in combination with TNF-α or TRAIL but not in combination with FasL abrogates transformation from blebbishields by inducing secondary necrosis. Thus blebbishield-mediated transformation is dependent on glycolysis, and Smac mimetics represent potential candidates to abrogate the blebbishield emergency program. PMID:27551498

  3. Mitochondrial oligomers boost glycolysis in cancer stem cells to facilitate blebbishield-mediated transformation after apoptosis.

    PubMed

    Jinesh, G G; Molina, J R; Huang, L; Laing, N M; Mills, G B; Bar-Eli, M; Kamat, A M

    2016-01-01

    Apoptosis culminates in secondary necrosis due to lack of ATP. Cancer stem cells form spheres after apoptosis by evoking the blebbishield emergency program. Hence, determining how blebbishields avoid secondary necrosis is crucial. Here we demonstrate that N-Myc and VEGFR2 control transformation from blebbishields, during which oligomers of K-Ras, p27, BAD, Bax, and Bak boost glycolysis to avoid secondary necrosis. Non-apoptotic cancer cells also utilize oligomers to boost glycolysis, which differentiates the glycolytic function of oligomers from their apoptotic action. Smac mimetic in combination with TNF-α or TRAIL but not in combination with FasL abrogates transformation from blebbishields by inducing secondary necrosis. Thus blebbishield-mediated transformation is dependent on glycolysis, and Smac mimetics represent potential candidates to abrogate the blebbishield emergency program. PMID:27551498

  4. Excitonic Coupling and Femtosecond Relaxation of Zinc Porphyrin Oligomers Linked with Triazole Bridge: Dynamics and Modeling.

    PubMed

    Bukreev, Alexey; Mikhailov, Konstantin; Shelaev, Ivan; Gostev, Fedor; Polevaya, Yuliya; Tyurin, Vladimir; Beletskaya, Irina; Umansky, Stanislav; Nadtochenko, Victor

    2016-03-31

    The synthesis of new zinc porphyrin oligomers linked by a triazole bridge was carried out via "click" reaction. A split in the porphyrin oligomer B-band was observed. It was considered as evidence of exciton-excitonic coupling. The relaxation of excited states in Q-band porphyrin oligomers was studied by the femtosecond laser spectroscopy technique with a 20 fs pump pulse. The transient oscillations of two B-band excitonic peaks have a π-radian shift. For explanation of the coherent oscillation, a theoretical model was developed. The model considered the combination of the exciton-excitonic coupling between porphyrin rings in dimer and weak exciton-vibronic coupling in one porphyrin ring. By varying the values of the structural parameters of porphyrins (the strength values of this couplings and measure of symmetry breaking), we obtained correspondence between the experimental data (phase shift and amplitudes of the spectrum oscillations) and the predictions of the model developed here. PMID:26935579

  5. Biodegradable polyester-based eco-composites containing hemp fibers modified with macrocyclic oligomers

    NASA Astrophysics Data System (ADS)

    Conzatti, Lucia; Utzeri, Roberto; Hodge, Philip; Stagnaro, Paola

    2016-05-01

    An original compatibilizing pathway for hemp fibers/poly(1,4-butylene adipate-co-terephtalate) (PBAT) eco-composites was explored exploiting the capability of macrocyclic oligomers (MCOs), obtained by cyclodepolymerization (CDP) of PBAT at high dilution, of being re-converted into linear chains by entropically-driven ring-opening polymerization (ED-ROP) that occurs simply heating the MCOS in the bulk. CDP reaction of PBAT was carried out varying solvent, catalyst and reaction time. Selected MCOs were used to adjust the conditions of the ED-ROP reaction. The best experimental conditions were then adopted to modify hemp fibers. Eco-composites based on PBAT and hemp fibers as obtained or modified with PBAT macrocyclics or oligomers were prepared by different process strategies. The best fiber-PBAT compatibility was observed when the fibers were modified with PBAT oligomers before incorporation in the polyester matrix.

  6. New insight into the dynamical system of αB-crystallin oligomers

    PubMed Central

    Inoue, Rintaro; Takata, Takumi; Fujii, Norihiko; Ishii, Kentaro; Uchiyama, Susumu; Sato, Nobuhiro; Oba, Yojiro; Wood, Kathleen; Kato, Koichi; Fujii, Noriko; Sugiyama, Masaaki

    2016-01-01

    α-Crystallin possesses a dynamic quaternary structure mediated by its subunit dynamics. Elucidation of a mechanism of subunit dynamics in homo-oligomers of αB-crystallin was tackled through deuteration-assisted small-angle neutron scattering (DA-SANS) and electrospray ionization (ESI) native mass spectrometry (nMS). The existence of subunit exchange was confirmed with DA-SANS, and monomers liberated from the oligomers were observed with nMS. With increasing temperature, an increase in both the exchange rate and monomer population was observed despite the absence of oligomer collapse. It is proposed that transiently liberated subunits, namely, “traveling subunits,” play a role in subunit exchange. Moreover, we propose that protein function is regulated by these traveling subunits. PMID:27381175

  7. A mechanistic model of tau amyloid aggregation based on direct observation of oligomers

    NASA Astrophysics Data System (ADS)

    Shammas, Sarah L.; Garcia, Gonzalo A.; Kumar, Satish; Kjaergaard, Magnus; Horrocks, Mathew H.; Shivji, Nadia; Mandelkow, Eva; Knowles, Tuomas P. J.; Mandelkow, Eckhard; Klenerman, David

    2015-04-01

    Protein aggregation plays a key role in neurodegenerative disease, giving rise to small oligomers that may become cytotoxic to cells. The fundamental microscopic reactions taking place during aggregation, and their rate constants, have been difficult to determine due to lack of suitable methods to identify and follow the low concentration of oligomers over time. Here we use single-molecule fluorescence to study the aggregation of the repeat domain of tau (K18), and two mutant forms linked with familial frontotemporal dementia, the deletion mutant ΔK280 and the point mutant P301L. Our kinetic analysis reveals that aggregation proceeds via monomeric assembly into small oligomers, and a subsequent slow structural conversion step before fibril formation. Using this approach, we have been able to quantitatively determine how these mutations alter the aggregation energy landscape.

  8. Regeneration of cello-oligomers via selective depolymerization of cellulose fibers derived from printed paper wastes.

    PubMed

    Voon, Lee Ken; Pang, Suh Cem; Chin, Suk Fun

    2016-05-20

    Cellulose extracted from printed paper wastes were selectively depolymerized under controlled conditions into cello-oligomers of controllable chain lengths via dissolution in an ionic liquid, 1-allyl-3-methylimidazolium chloride (AMIMCl), and in the presence of an acid catalyst, Amberlyst 15DRY. The depolymerization process was optimized against reaction temperature, concentration of acid catalyst, and reaction time. Despite rapid initial depolymerization process, the rate of cellulose depolymerization slowed down gradually upon prolonged reaction time, with 75.0wt% yield of regenerated cello-oligomers (mean Viscosimetric Degree of Polymerization value of 81) obtained after 40min. The depolymerization of cellulose fibers at 80°C appeared to proceed via a second-order kinetic reaction with respect to the catalyst concentration of 0.23mmol H3O(+). As such, the cellulose depolymerization process could afford some degree of control on the degree of polymerization or chain lengths of cello-oligomers formed. PMID:26917370

  9. Solution State Structure Determination of Silicate Oligomers by 29Si NMR Spectroscopy and Molecular Modeling

    SciTech Connect

    Cho, Herman M.; Felmy, Andrew R.; Craciun, Raluca; Keenum, Johnathan P.; Shah, Neil K.; Dixon, David A.

    2006-02-22

    Evidence for nine new solution state silicate oligomers has been discovered by 29Si NMR homonuclear correlation experiments of 29Si-enriched samples. In addition to enhancing signal sensitivity, the isotopic enrichment increases the probability of the 29Si–29Si two-bond scalar couplings that are necessary for the observation of internuclear correlations in 2-D experiments. The proposed assignments are validated by comparisons of experimental and simulated crosspeaks obtained with high digital resolution. The internuclear connectivity indicated by the NMR data suggests that several of these oligomers can have multiple stereoisomers, including conformers and/or diastereomers. The stability of these oligomers and their possible stereoisomers have been investigated by electronic structure calculations.

  10. Solution state structure determination of silicate oligomers by 29SI NMR spectroscopy and molecular modeling.

    PubMed

    Cho, Herman; Felmy, Andrew R; Craciun, Raluca; Keenum, J Patrick; Shah, Neil; Dixon, David A

    2006-02-22

    Evidence for nine new solution state silicate oligomers has been discovered by (29)Si NMR homonuclear correlation experiments of (29)Si-enriched samples. In addition to enhancing signal sensitivity, the isotopic enrichment increases the probability of the (29)Si-(29)Si two-bond scalar couplings that are necessary for the observation of internuclear correlations in 2-D experiments. The proposed assignments are validated by comparisons of experimental and simulated cross-peaks obtained with high digital resolution. The internuclear connectivity indicated by the NMR data suggests that several of these oligomers can have multiple stereoisomers, including conformers and/or diastereomers. The stabilities of these oligomers and their possible stereoisomers have been investigated by electronic structure calculations. PMID:16478188

  11. Deleterious effects of soluble amyloid-β oligomers on multiple steps of synaptic vesicle trafficking.

    PubMed

    Park, Joohyun; Jang, Mirye; Chang, Sunghoe

    2013-07-01

    Growing evidence supports a role for soluble amyloid-β oligomer intermediates in the synaptic dysfunction associated with Alzheimer's disease (AD), but the molecular mechanisms underlying this effect remain unclear. We found that acute treatment of cultured rat hippocampal neurons with nanomolar concentrations of Aβ oligomers reduced the recycling pool and increased the resting pool of synaptic vesicles. Endocytosis of synaptic vesicles and the regeneration of fusion-competent vesicles were also severely impaired. Furthermore, the release probability of the readily-releasable pool (RRP) was increased, and recovery of the RRP was delayed. All these effects were prevented by antibody against Aβ. Moreover reduction of the pool size was prevented by inhibiting calpain or CDK5, while the defects in endocytosis were averted by overexpressing phosphatidylinositol-4-phosphate-5-kinase type I-γ, indicating that these two downstream pathways are involved in Aβ oligomers-induced presynaptic dysfunction. PMID:23523634

  12. Simple extrapolation method to predict the electronic structure of conjugated polymers from calculations on oligomers

    DOE PAGESBeta

    Larsen, Ross E.

    2016-04-12

    In this study, we introduce two simple tight-binding models, which we call fragment frontier orbital extrapolations (FFOE), to extrapolate important electronic properties to the polymer limit using electronic structure calculations on only a few small oligomers. In particular, we demonstrate by comparison to explicit density functional theory calculations that for long oligomers the energies of the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and of the first electronic excited state are accurately described as a function of number of repeat units by a simple effective Hamiltonian parameterized from electronic structure calculations on monomers, dimers and, optionally,more » tetramers. For the alternating copolymer materials that currently comprise some of the most efficient polymer organic photovoltaic devices one can use these simple but rigorous models to extrapolate computed properties to the polymer limit based on calculations on a small number of low-molecular-weight oligomers.« less

  13. Formation of nitrogen-containing oligomers by methylglyoxal and amines in simulated evaporating cloud droplets.

    PubMed

    De Haan, David O; Hawkins, Lelia N; Kononenko, Julia A; Turley, Jacob J; Corrigan, Ashley L; Tolbert, Margaret A; Jimenez, Jose L

    2011-02-01

    Reactions of methylglyoxal with amino acids, methylamine, and ammonium sulfate can take place in aqueous aerosol and evaporating cloud droplets. These processes are simulated by drying droplets and bulk solutions of these compounds (at low millimolar and 1 M concentrations, respectively) and analyzing the residuals by scanning mobility particle sizing, nuclear magnetic resonance, aerosol mass spectrometry (AMS), and electrospray ionization MS. The results are consistent with imine (but not diimine) formation on a time scale of seconds, followed by the formation of nitrogen-containing oligomers, methylimidazole, and dimethylimidazole products on a time scale of minutes to hours. Measured elemental ratios are consistent with imidazoles and oligomers being major reaction products, while effective aerosol densities suggest extensive reactions take place within minutes. These reactions may be a source of the light-absorbing, nitrogen-containing oligomers observed in urban and biomass-burning aerosol particles. PMID:21171623

  14. New insight into the dynamical system of αB-crystallin oligomers.

    PubMed

    Inoue, Rintaro; Takata, Takumi; Fujii, Norihiko; Ishii, Kentaro; Uchiyama, Susumu; Sato, Nobuhiro; Oba, Yojiro; Wood, Kathleen; Kato, Koichi; Fujii, Noriko; Sugiyama, Masaaki

    2016-01-01

    α-Crystallin possesses a dynamic quaternary structure mediated by its subunit dynamics. Elucidation of a mechanism of subunit dynamics in homo-oligomers of αB-crystallin was tackled through deuteration-assisted small-angle neutron scattering (DA-SANS) and electrospray ionization (ESI) native mass spectrometry (nMS). The existence of subunit exchange was confirmed with DA-SANS, and monomers liberated from the oligomers were observed with nMS. With increasing temperature, an increase in both the exchange rate and monomer population was observed despite the absence of oligomer collapse. It is proposed that transiently liberated subunits, namely, "traveling subunits," play a role in subunit exchange. Moreover, we propose that protein function is regulated by these traveling subunits. PMID:27381175

  15. The Aβ oligomer hypothesis for synapse failure and memory loss in Alzheimer's disease.

    PubMed

    Ferreira, Sergio T; Klein, William L

    2011-11-01

    Alzheimer's disease (AD) is the 3rd most costly disease and the leading cause of dementia. It can linger for many years, but ultimately is fatal, the 6th leading cause of death. Alzheimer's disease (AD) is fatal and affected individuals can sometimes linger many years. Current treatments are palliative and transient, not disease modifying. This article reviews progress in the search to identify the primary AD-causing toxins. We summarize the shift from an initial focus on amyloid plaques to the contemporary concept that AD memory failure is caused by small soluble oligomers of the Aβ peptide, toxins that target and disrupt particular synapses. Evidence is presented that links Aβ oligomers to pathogenesis in animal models and humans, with reference to seminal discoveries from cell biology and new ideas concerning pathogenic mechanisms, including relationships to diabetes and Fragile X. These findings have established the oligomer hypothesis as a new molecular basis for the cause, diagnosis, and treatment of AD. PMID:21914486

  16. Single Chain Variable Fragment Against Aβ Expressed in Baculovirus Inhibits Abeta Fibril Elongation and Promotes its Disaggregation

    PubMed Central

    Fang, Fang; Song, Lin-Lin; Jiao, Yue-Ying; Wang, He; Peng, Xiang-Lei; Zheng, Yan-Peng; Wang, Jun; He, Jin-Sheng; Hung, Tao

    2015-01-01

    Alzheimer’s disease (AD) is the most common form of age-related dementia, and the most urgent problem is that it is currently incurable. Amyloid-β (Aβ) peptide is believed to play a major role in the pathogenesis of AD. We previously reported that an Aβ N-terminal amino acid targeting monoclonal antibody (MAb), A8, inhibits Aβ fibril formation and has potential as an immunotherapy for AD based on a mouse model. To further study the underlying mechanisms, we tested our hypothesis that the single chain fragment variable (scFv) without the Fc fragment is capable of regulating either Aβ aggregation or disaggregation in vitro. Here, a model of cell-free Aβ “on-pathway” aggregation was established and identified using PCR, Western blot, ELISA, transmission electron microscopy (TEM) and thioflavin T (ThT) binding analyses. His-tagged A8 scFvs was cloned and solubly expressed in baculovirus. Our data demonstrated that the Ni-NTA agarose affinity-purified A8 scFv inhibited the forward reaction of “on-pathway” aggregation and Aβ fibril maturation. The effect of A8 scFv on Aβ fibrillogenesis was markedly more significant when administered at the start of the Aβ folding reaction. Furthermore, the results also showed that pre-formed Aβ fibrils could be disaggregated via incubation with purified A8 scFv, which suggested that A8 scFv is involved in the reverse reaction of Aβ aggregation. Therefore, A8 scFv was capable of both inhibiting fibrillogenesis and disaggregating matured fibrils. Our present study provides valuable insight into the regulators of ultrastructural dynamics of cell-free “on-pathway” Aβ aggregation and will assist in the development of therapeutic strategies for AD. PMID:25919299

  17. Conformational Switching and Nanoscale Assembly of Human Prion Protein into Polymorphic Amyloids via Structurally Labile Oligomers.

    PubMed

    Dalal, Vijit; Arya, Shruti; Bhattacharya, Mily; Mukhopadhyay, Samrat

    2015-12-29

    Conformational switching of the prion protein (PrP) from an α-helical normal cellular form (PrP(C)) to an aggregation-prone and self-propagating β-rich scrapie form (PrP(Sc)) underlies the molecular basis of pathogenesis in prion diseases. Anionic lipids play a critical role in the misfolding and conformational conversion of the membrane-anchored PrP into the amyloidogenic pathological form. In this work, we have used a diverse array of techniques to interrogate the early intermediates during amyloid formation from recombinant human PrP in the presence of a membrane mimetic anionic detergent such as sodium dodecyl sulfate. We have been able to detect and characterize two distinct types of interconvertible oligomers. Our results demonstrate that highly ordered large β-oligomers represent benign off-pathway intermediates that lack the ability to mature into amyloid fibrils. On the contrary, structurally labile small oligomers are capable of switching to an ordered amyloid-state that exhibits profound toxicity to mammalian cells. Our fluorescence resonance energy transfer measurements revealed that the partially disordered PrP serves as precursors to small amyloid-competent oligomers. These on-pathway oligomers are eventually sequestered into higher order supramolecular assemblies that conformationally mature into polymorphic amyloids possessing varied nanoscale morphology as evident by the atomic force microscopy imaging. The nanoscale diversity of fibril architecture is attributed to the heterogeneous ensemble of early obligatory oligomers and offers a plausible explanation for the existence of multiple prion strains in vivo. PMID:26645611

  18. Thio-urethane oligomers improve the properties of light-cured resin cements

    PubMed Central

    Bacchi, Ataís; Consani, Rafael L.; Martim, Gedalias C.; Pfeifer, Carmem S.

    2015-01-01

    Thio-urethanes were synthesized by combining 1,6-Hexanediol-diissocyante (aliphatic) with pentaerythritol tetra-3-mercaptopropionate (PETMP) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (aromatic) with trimethylol-tris-3-mercaptopropionate (TMP), at 1:2 isocyanate:thiol, leaving pendant thiols. Oligomers were added at 10–30 phr to BisGMA-UDMA-TEGDMA (5:3:2, BUT). 25wt% silanated inorganic fillers were added. Commercial cement (Relyx Veneer, 3M-ESPE) was also evaluated with 10–20 phr of aromatic oligomer. Near-IR was used to follow methacrylate conversion (DC) and rate of polymerization (Rpmax). Mechanical properties were evaluated in three-point bending (ISO 4049) for flexural strength/modulus (FS/FM, and toughness), and notched specimens (ASTM Standard E399-90) for fracture toughness (KIC). Polymerization stress (PS) was measured on the Bioman. Volumetric shrinkage (VS, %) was measured with the bonded disk technique. Results were analyzed with ANOVA/Tukey’s test (α=5%). In general terms, for BUT cements, conversion and mechanical properties in flexure increased for selected groups with the addition of thio-urethane oligomers. The aromatic versions resulted in greater FS/FM than aliphatic. Fracture toughness increased by twofold in the experimental groups (from 1.17±0.36 to around 3.23±0.22 MPa.m1/2). Rpmax decreased with the addition of thio-urethanes, though the vitrification point was not statistically different from the control. VS and PS decreased with both oligomers. For the commercial cement, 20 phr of oligomer increased DC, vitrification, reduced Rpmax and also significantly increased KIC, and reduced PS and FM. Thio-urethane oligomers were shown to favorably modify conventional dimethacrylate networks. Significant reductions in polymerization stress were achieved at the same time conversion and fracture toughness increased. PMID:25740124

  19. Nicotinamide mononucleotide protects against β-amyloid oligomer-induced cognitive impairment and neuronal death.

    PubMed

    Wang, Xiaonan; Hu, Xuejun; Yang, Yang; Takata, Toshihiro; Sakurai, Takashi

    2016-07-15

    Amyloid-β (Aβ) oligomers are recognized as the primary neurotoxic agents in Alzheimer's disease (AD). Impaired brain energy metabolism and oxidative stress are implicated in cognitive decline in AD. Nicotinamide adenine dinucleotide (NAD(+)), a coenzyme involved in redox activities in the mitochondrial electron transport chain, has been identified as a key regulator of the lifespan-extending effects, and the activation of NAD(+) expression has been linked with a decrease in Aβ toxicity in AD. One of the key precursors of NAD(+) is nicotinamide mononucleotide (NMN), a product of the nicotinamide phosphoribosyltransferase reaction. To determine whether improving brain energy metabolism will forestall disease progress in AD, the impact of the NAD(+) precursor NMN on Aβ oligomer-induced neuronal death and cognitive impairment were studied in organotypic hippocampal slice cultures (OHCs) and in a rat model of AD. Treatment of intracerebroventricular Aβ oligomer infusion AD model rats with NMN (500mg/kg, intraperitoneally) sustained improvement in cognitive function as assessed by the Morris water maze. In OHCs, Aβ oligomer-treated culture media with NMN attenuated neuronal cell death. NMN treatment also significantly prevented the Aβ oligomer-induced inhibition of LTP. Furthermore, NMN restored levels of NAD(+) and ATP, eliminated accumulation of reactive oxygen species (ROS) in the Aβ oligomer-treated hippocampal slices. All these protective effects were reversed by 3-acetylpyridine, which generates inactive NAD(+). The present study indicates that NMN could restore cognition in AD model rats. The beneficial effect of NMN is produced by ameliorating neuron survival, improving energy metabolism and reducing ROS accumulation. These results suggest that NMN may become a promising therapeutic drug for AD. PMID:27130898

  20. Detection of TDP-43 Oligomers in Frontotemporal Lobar Degeneration–TDP

    PubMed Central

    Kao, Patricia F.; Chen, Yun-Ru; Liu, Xiao-Bo; DeCarli, Charles; Seeley, William W.; Jin, Lee-Way

    2016-01-01

    Objective The proteinaceous inclusions in TDP-43 proteinopathies such as frontotemporal lobar degeneration (FTLD)-TDP are made of high–molecular-weight aggregates of TDP-43. These aggregates have not been classified as amyloids, as prior amyloid staining results were not conclusive. Here we used a specific TDP-43 amyloid oligomer antibody called TDP-O to determine the presence and abundance of TDP-43 oligomers among different subtypes of FTLD-TDP as well as in hippocampal sclerosis (HS), which represents a non-FTLD pathology with TDP-43 inclusions. Methods Postmortem tissue from the hippocampus and anterior orbital gyrus from 54 prospectively assessed and diagnosed subjects was used for immunostaining with TDP-O. Electron microscopy was used to assess the subcellular locations of TDP-O–decorated structures. Results TDP-43 inclusions staining with TDP-O were present in FTLD-TDP and were most conspicuous for FTLD-TDP type C, the subtype seen in most patients with semantic variant primary progressive aphasia. TDP-O immunoreactivity was absent in the hippocampus of HS patients despite abundant TDP-43 inclusions. Ultrastructurally, TDP-43 oligomers resided in granular or tubular structures, frequently in close proximity to, but not within, neuronal lysosomes. Interpretation TDP-43 forms amyloid oligomers in the human brain, which may cause neurotoxicity in a manner similar to other amyloid oligomers. Oligomer formation may contribute to the conformational heterogeneity of TDP-43 aggregates and mark the different properties of TDP-43 inclusions between FTLD-TDP and HS. PMID:25921485

  1. DT-Diaphorase Prevents Aminochrome-Induced Alpha-Synuclein Oligomer Formation and Neurotoxicity

    PubMed Central

    Muñoz, Patricia; Cardenas, Sergio; Huenchuguala, Sandro; Briceño, Andrea; Couve, Eduardo; Paris, Irmgard; Segura-Aguilar, Juan

    2015-01-01

    It was reported that aminochrome induces the formation of alpha synuclein (SNCA) oligomers during dopamine oxidation. We found that DT-diaphorase (NQO1) prevents the formation of SNCA oligomers in the presence of aminochrome determined by Western blot, transmission electron microscopy, circular dichroism, and thioflavin T fluorescence, suggesting a protective role of NQO1 by preventing the formation of SNCA oligomers in dopaminergic neurons. In order to test NQO1 protective role in SNCA neurotoxicity in cellular model, we overexpressed SNCA in both RCSN-3 cells (wild-type) and RCSN-3Nq7 cells, which have constitutive expression of a siRNA against NQO1. The expression of SNCA in RCSN-3SNCA and RCSN-3Nq7SNCA cells increased 4.2- and 4.4-fold, respectively. The overexpression of SNCA in RCSN-3Nq7SNCA cells induces a significant increase in cell death of 2.8- and 3.2-fold when they were incubated with 50 and 70 µM aminochrome, respectively. The cell death was found to be of apoptotic character determined by annexin/propidium iodide technique with flow cytometry and DNA laddering. A Western blot demonstrated that SNCA in RCSN-3SNCA is only found in monomer form both in the presence of 20 µM aminochrome or cell culture medium contrasting with RCSN-3Nq7SNCA cells where the majority SNCA is found as oligomer. The antioligomer compound scyllo-inositol induced a significant decrease in aminochrome-induced cell death in RCSN-3Nq7SNCA cells in comparison to cells incubated in the absence of scyllo-inositol. Our results suggest that NQO1 seems to play an important role in the prevention of aminochrome-induced SNCA oligomer formation and SNCA oligomers neurotoxicity in dopaminergic neurons. PMID:25634539

  2. Synthesis and Properties of Phenylethynyl-Terminated, Star-Branched, Phenylquinoxaline Oligomers

    NASA Technical Reports Server (NTRS)

    Ooi, I. H.; Hergenrother, P. M.; Harris, F. W.

    2000-01-01

    The primary objective of this work was to prepare readily melt and solution processable phenylquinoxaline (PQ) oligomers that could be thermally crosslinked to solvent-resistant resins. Thus, a mixture of 2-(4-hydroxyphenyl)-3-phenyl-6-fluoroquinoxaline and 3-(4-hydroxyphenyl)-2-phenyl-6-fluoroquinoxaline (HPFQ) was used to prepare star-branched PQ oligomers end-capped with 4-fluoro-4-phenylethynylbenzophenone (FPEB). 1,1,1-Tris(4-hydroxyphenyl)ethane (THPE) was used as the branching unit. The oligomer number-average molecular weights (M (bar) (sub n) S) as determined by size exclusion chromatography (SEC) were close to the calculated values of 2922, 4698, 6474, and 13,578 g/mol, and their intrinsic viscosities ranged from 0.16 to 0.57 dl/g (m-cresol at 30 C). The oligomers, which were quite soluble in common organic solvents, had glass transition temperatures (T (sub g) S) that ranged from 181 to 233 C (DSC, DELTA T = 20 C/min). They also underwent an exothermic cure with maxima from 377 to 443 C. The T (sub g) S of the cured oligomers ranged from 259 to 284 C depending on the oligomer M (bar) (sub n) and the curing conditions. The oligomers had low melt viscosities, e.g. an oligomer (SPQ-46) with an M (bar) (sub n) of 4816 g/mol (SEC) had a melt viscosity of 150 Pa s at 348 C. A cured thin film of SPQ-46, which was insoluble in common organic solvents, had a room temperature (RT) tensile strength of 100 MPa, a RT modulus of 2358 MPa, and a RT elongation of 5.9%. A cured sample of SPQ-46 displayed a RT titanium-titanium lap shear tensile strength of 35.2 MPa. SPQ-46/carbon fiber(IM-7) composites, were prepared that displayed a RT flexural strength of 1902 MPa, a RT modulus of 1.38 GPa and a RT open hole compressive strength of 433 MPa.

  3. Synthesis and incorporation of thienylene vinylene oligomers in main-chain copolymers

    SciTech Connect

    Madrigal, L.G.; Elandaloussi, E.H.; Spangler, C.W.

    1998-07-01

    Poly [2,5-thienylene vinylene] (PTV) has been studied extensively over the past decade for both its metallic conductivity behavior upon chemical doping, as well as its interesting third order nonlinear optical properties. PTV oligomers have been synthesized by the group, as well as others, and the formation of polaron-like radical-cations or bipolaron-like dications by oxidative doping has been demonstrated. In this paper the authors describe a general synthetic approach to PTV oligomers functionalized for copolymer formation by step-growth reaction.

  4. Endogenous Docosahexaenoic Acid (DHA) Prevents Aβ1-42 Oligomer-Induced Neuronal Injury.

    PubMed

    Tan, Yuan; Ren, Huixia; Shi, Zhe; Yao, Xiaoli; He, Chengwei; Kang, Jing-X; Wan, Jian-Bo; Li, Peng; Yuan, Ti-Fei; Su, Huanxing

    2016-07-01

    The intake of the polyunsaturated fatty acid docosahexaenoic acid (DHA) or n-3 fatty acid has been associated with reduced risk of Alzheimer's disease (AD) in epidemiological reports. However, the underlying mechanism remains to be elucidated. Here, we report that exogenous DHA administration could protect neurons against Aβ oligomer-induced injury both in vitro and in vivo, partly through reducing the endoplasmic reticulum (ER) stress, and preventing cell apoptosis. In transgenic fat-1 mice with enriched ω-3 fatty acids, Aβ oligomers induced fewer neuronal losses, when compared to wild-type (WT) mice. We conclude that endogenous DHA are neuroprotective in pathogenesis processes of AD. PMID:26021747

  5. Fibrillar Oligomers Nucleate the Oligomerization of Monomeric Amyloid β but Do Not Seed Fibril Formation*

    PubMed Central

    Wu, Jessica W.; Breydo, Leonid; Isas, J. Mario; Lee, Jerome; Kuznetsov, Yurii G.; Langen, Ralf; Glabe, Charles

    2010-01-01

    Soluble amyloid oligomers are potent neurotoxins that are involved in a wide range of human degenerative diseases, including Alzheimer disease. In Alzheimer disease, amyloid β (Aβ) oligomers bind to neuronal synapses, inhibit long term potentiation, and induce cell death. Recent evidence indicates that several immunologically distinct structural variants exist as follows: prefibrillar oligomers (PFOs), fibrillar oligomers (FOs), and annular protofibrils. Despite widespread interest, amyloid oligomers are poorly characterized in terms of structural differences and pathological significance. FOs are immunologically related to fibrils because they react with OC, a conformation-dependent, fibril-specific antibody and do not react with antibodies specific for other types of oligomers. However, fibrillar oligomers are much smaller than fibrils. FOs are soluble at 100,000 × g, rich in β-sheet structures, but yet bind weakly to thioflavin T. EPR spectroscopy indicates that FOs display significantly more spin-spin interaction at multiple labeled sites than PFOs and are more structurally similar to fibrils. Atomic force microscopy indicates that FOs are approximately one-half to one-third the height of mature fibrils. We found that Aβ FOs do not seed the formation of thioflavin T-positive fibrils from Aβ monomers but instead seed the formation of FOs from Aβ monomers that are positive for the OC anti-fibril antibody. These results indicate that the lattice of FOs is distinct from the fibril lattice even though the polypeptide chains are organized in an immunologically identical conformation. The FOs resulting from seeded reactions have the same dimensions and morphology as the initial seeds, suggesting that the seeds replicate by growing to a limiting size and then splitting, indicating that their lattice is less stable than fibrils. We suggest that FOs may represent small pieces of single fibril protofilament and that the addition of monomers to the ends of FOs is

  6. Enzymatic production of defined chitosan oligomers with a specific pattern of acetylation using a combination of chitin oligosaccharide deacetylases

    NASA Astrophysics Data System (ADS)

    Hamer, Stefanie Nicole; Cord-Landwehr, Stefan; Biarnés, Xevi; Planas, Antoni; Waegeman, Hendrik; Moerschbacher, Bruno Maria; Kolkenbrock, Stephan

    2015-03-01

    Chitin and chitosan oligomers have diverse biological activities with potentially valuable applications in fields like medicine, cosmetics, or agriculture. These properties may depend not only on the degrees of polymerization and acetylation, but also on a specific pattern of acetylation (PA) that cannot be controlled when the oligomers are produced by chemical hydrolysis. To determine the influence of the PA on the biological activities, defined chitosan oligomers in sufficient amounts are needed. Chitosan oligomers with specific PA can be produced by enzymatic deacetylation of chitin oligomers, but the diversity is limited by the low number of chitin deacetylases available. We have produced specific chitosan oligomers which are deacetylated at the first two units starting from the non-reducing end by the combined use of two different chitin deacetylases, namely NodB from Rhizobium sp. GRH2 that deacetylates the first unit and COD from Vibrio cholerae that deacetylates the second unit starting from the non-reducing end. Both chitin deacetylases accept the product of each other resulting in production of chitosan oligomers with a novel and defined PA. When extended to further chitin deacetylases, this approach has the potential to yield a large range of novel chitosan oligomers with a fully defined architecture.

  7. Permeability and partitioning of ferrocene ethylene oxide and propylene oxide oligomers into electropolymerized films from acetonitrile and polyether solutions

    SciTech Connect

    Pyati, R.; Murray, R.W. )

    1994-10-27

    We report the first electrochemically-based measurements of the rates of small polymer permeation into another polymer. The small polymer permeants are ferrocene ethylene oxide oligomers containing 2, 7, and 16 units and a propylene oxide oligomer containing 3 units. Their permeation into ultrathin microelectrode-supported films of the metal complex polymer poly[Ru(vbpy)[sub 3

  8. Efficient access to conjugated 4,4'-bipyridinium oligomers using the Zincke reaction: synthesis, spectroscopic and electrochemical properties.

    PubMed

    Chen, Long; Willcock, Helen; Wedge, Christopher J; Hartl, František; Colquhoun, Howard M; Greenland, Barnaby W

    2016-01-21

    The cyclocondensation reaction between rigid, electron-rich aromatic diamines and 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridinium (Zincke) salts has been harnessed to produce a series of conjugated oligomers containing up to twelve aromatic/heterocyclic residues. These oligomers exhibit discrete, multiple redox processes accompanied by dramatic changes in electronic absorption spectra. PMID:26626110

  9. An oligomer complementary to c-myc mRNA inhibits proliferation of HL-60 promyelocytic cells and induces differentiation.

    PubMed Central

    Holt, J T; Redner, R L; Nienhuis, A W

    1988-01-01

    To study the role of a nuclear proto-oncogene in the regulation of cell growth and differentiation, we inhibited HL-60 c-myc expression with a complementary antisense oligomer. This oligomer was stable in culture and entered cells, forming an intracellular duplex. Incubation of cells with the anti-myc oligomer decreased the steady-state levels of c-myc protein by 50 to 80%, whereas a control oligomer did not significantly affect the c-myc protein concentration. Direct inhibition of c-myc expression with the anti-myc oligomer was associated with a decreased cell growth rate and an induction of myeloid differentiation. Related antisense oligomers with 2- to 12-base-pair mismatches with c-myc mRNA did not influence HL-60 cells. Thus, the effects of the antisense oligomer exhibited sequence specificity, and furthermore, these effects could be reversed by hybridization competition with another complementary oligomer. Antisense inhibition of a nuclear proto-oncogene apparently bypasses cell surface events in affecting cell proliferation and differentiation. Images PMID:3280975

  10. Enzymatic production of defined chitosan oligomers with a specific pattern of acetylation using a combination of chitin oligosaccharide deacetylases

    PubMed Central

    Hamer, Stefanie Nicole; Cord-Landwehr, Stefan; Biarnés, Xevi; Planas, Antoni; Waegeman, Hendrik; Moerschbacher, Bruno Maria; Kolkenbrock, Stephan

    2015-01-01

    Chitin and chitosan oligomers have diverse biological activities with potentially valuable applications in fields like medicine, cosmetics, or agriculture. These properties may depend not only on the degrees of polymerization and acetylation, but also on a specific pattern of acetylation (PA) that cannot be controlled when the oligomers are produced by chemical hydrolysis. To determine the influence of the PA on the biological activities, defined chitosan oligomers in sufficient amounts are needed. Chitosan oligomers with specific PA can be produced by enzymatic deacetylation of chitin oligomers, but the diversity is limited by the low number of chitin deacetylases available. We have produced specific chitosan oligomers which are deacetylated at the first two units starting from the non-reducing end by the combined use of two different chitin deacetylases, namely NodB from Rhizobium sp. GRH2 that deacetylates the first unit and COD from Vibrio cholerae that deacetylates the second unit starting from the non-reducing end. Both chitin deacetylases accept the product of each other resulting in production of chitosan oligomers with a novel and defined PA. When extended to further chitin deacetylases, this approach has the potential to yield a large range of novel chitosan oligomers with a fully defined architecture. PMID:25732514

  11. A spiropyran-based fluorescent probe for the specific detection of β-amyloid peptide oligomers in Alzheimer's disease.

    PubMed

    Lv, Guanglei; Sun, Anyang; Wei, Peng; Zhang, Ning; Lan, Haichuang; Yi, Tao

    2016-07-01

    We report a new spiropyran-based fluorescent probe that exhibits high affinity and specificity towards Aβ oligomers both in vitro and in vivo. This probe can penetrate the blood brain barrier and specifically target Aβ oligomers in the brains of transgenic mice in models for Alzheimer's disease. PMID:27346489

  12. Simulating hydrogen-bond clustering and phase behaviour of imidazole oligomers

    NASA Astrophysics Data System (ADS)

    Harvey, Jacob A.; Basak, Dipankar; Venkataraman, Dhandapani; Auerbach, Scott M.

    2012-05-01

    We have modelled structures and dynamics of hydrogen bond networks that form from imidazoles tethered to oligomeric aliphatic backbones in crystalline and glassy phases. We have studied the behaviour of oligomers containing 5 or 10 imidazole groups. These systems have been simulated over the range 100-900 K with constant-pressure molecular dynamics using the AMBER 94 forcefield, which was found to show good agreement with ab initio calculations on hydrogen bond strengths and imidazole rotational barriers. Hypothetical crystalline solids formed from packed 5-mers and 10-mers melt above 600 K, then form glassy solids upon cooling. Viewing hydrogen bond networks as clusters, we gathered statistics on cluster sizes and percolating pathways as a function of temperature, for comparison with the same quantities extracted from neat imidazole liquid. We have found that, at a given temperature, the glass composed of imidazole 5-mers shows the same hydrogen bond mean cluster size as that from the 10-mer glass, and that this size is consistently larger than that in liquid imidazole. Hydrogen bond clusters were found to percolate across the simulation cell for all glassy and crystalline solids, but not for any imidazole liquid. The apparent activation energy associated with hydrogen bond lifetimes in these glasses (9.3 kJ mol-1) is close to that for the liquid (8.7 kJ mol-1), but is substantially less than that in the crystalline solid (13.3 kJ mol-1). These results indicate that glassy oligomeric solids show a promising mixture of extended hydrogen bond clusters and liquid-like dynamics.

  13. Domains of STIP1 responsible for regulating PrPC-dependent amyloid-β oligomer toxicity.

    PubMed

    Maciejewski, Andrzej; Ostapchenko, Valeriy G; Beraldo, Flavio H; Prado, Vania F; Prado, Marco A M; Choy, Wing-Yiu

    2016-07-15

    Soluble oligomers of amyloid-beta peptide (AβO) transmit neurotoxic signals through the cellular prion protein (PrP(C)) in Alzheimer's disease (AD). Secreted stress-inducible phosphoprotein 1 (STIP1), an Hsp70 and Hsp90 cochaperone, inhibits AβO binding to PrP(C) and protects neurons from AβO-induced cell death. Here, we investigated the molecular interactions between AβO and STIP1 binding to PrP(C) and their effect on neuronal cell death. We showed that residues located in a short region of PrP (90-110) mediate AβO binding and we narrowed the major interaction in this site to amino acids 91-100. In contrast, multiple binding sites on STIP1 (DP1, TPR1 and TPR2A) contribute to PrP binding. DP1 bound the N-terminal of PrP (residues 23-95), whereas TPR1 and TPR2A showed binding to the C-terminal of PrP (residues 90-231). Importantly, only TPR1 and TPR2A directly inhibit both AβO binding to PrP and cell death. Furthermore, our structural studies reveal that TPR1 and TPR2A bind to PrP through distinct regions. The TPR2A interface was shown to be much more extensive and to partially overlap with the Hsp90 binding site. Our data show the possibility of a PrP, STIP1 and Hsp90 ternary complex, which may influence AβO-mediated cell death. PMID:27208175

  14. Construction of human Fab library and screening of a single-domain antibody of amyloid-beta 42 oligomers

    PubMed Central

    Yuan, Zuanning; Du, Minge; Chen, Yiwen; Dou, Fei

    2013-01-01

    Screening humanized antibodies from a human Fab phage display library is an effective and quick method to obtain beta-amyloid oligomers. Thus, the present study prepared amyloid-beta 42 oli-gomers and constructed a naïve human Fab phage display library based on blood samples from six healthy people. After three rounds of biopanning in vitro, a human single-domain antibody that specifically recognized amyloid-beta 42 oligomers was identified. Western blot and enzyme-linked immunosorbent assay demonstrated this antibody bound specifically to human amyloid-beta 42 tetramer and nonamer, but not the monomer or high molecular weight oligomers. This study successfully constructed a human phage display library and screened a single-domain antibody that specifically recognized amyloid-beta 42 oligomers. PMID:25206631

  15. Crystallization and preliminary crystallographic study of oligomers of the haemolytic lectin CEL-III from the sea cucumber Cucumaria echinata.

    PubMed

    Unno, Hideaki; Hisamatsu, Keigo; Nagao, Tomonao; Tateya, Yuki; Matsumoto, Naoki; Goda, Shuichiro; Hatakeyama, Tomomitsu

    2013-04-01

    CEL-III is a Ca(2+)-dependent haemolytic lectin isolated from the marine invertebrate Cucumaria echinata. This lectin binds to Gal/GalNAc-containing carbohydrate chains on the cell surface and, after conformational changes, oligomerizes to form ion-permeable pores in cell membranes. CEL-III also forms soluble oligomers similar to those formed in cell membranes upon binding of specific carbohydrates in high-pH and high-salt solutions. These soluble and membrane CEL-III oligomers were crystallized and X-ray diffraction data were collected. Crystals of soluble oligomers and membrane oligomers diffracted X-rays to 3.3 and 4.2 Å resolution, respectively, using synchrotron radiation and the former was found to belong to space group C2. Self-rotation functional analysis of the soluble oligomer crystal suggested that it might be composed of heptameric CEL-III. PMID:23545649

  16. Crystallization and preliminary crystallographic study of oligomers of the haemolytic lectin CEL-III from the sea cucumber Cucumaria echinata

    PubMed Central

    Unno, Hideaki; Hisamatsu, Keigo; Nagao, Tomonao; Tateya, Yuki; Matsumoto, Naoki; Goda, Shuichiro; Hatakeyama, Tomomitsu

    2013-01-01

    CEL-III is a Ca2+-dependent haemolytic lectin isolated from the marine invertebrate Cucumaria echinata. This lectin binds to Gal/GalNAc-containing carbohydrate chains on the cell surface and, after conformational changes, oligomerizes to form ion-permeable pores in cell membranes. CEL-III also forms soluble oligomers similar to those formed in cell membranes upon binding of specific carbohydrates in high-pH and high-salt solutions. These soluble and membrane CEL-III oligomers were crystallized and X-ray diffraction data were collected. Crystals of soluble oligomers and membrane oligomers diffracted X-rays to 3.3 and 4.2 Å resolution, respectively, using synchrotron radiation and the former was found to belong to space group C2. Self-rotation functional analysis of the soluble oligomer crystal suggested that it might be composed of heptameric CEL-III. PMID:23545649

  17. The green tea polyphenol (−)-epigallocatechin gallate prevents the aggregation of tau protein into toxic oligomers at substoichiometric ratios

    PubMed Central

    Wobst, Heike J; Sharma, Apurwa; Diamond, Marc I; Wanker, Erich E; Bieschke, Jan

    2015-01-01

    The accumulation of amyloid-beta (Aβ) and tau aggregates is a pathological hallmark of Alzheimer's disease. Both polypeptides form fibrillar deposits, but several lines of evidence indicate that Aβ and tau form toxic oligomeric aggregation intermediates. Depleting such structures could thus be a powerful therapeutic strategy. We generated a fragment of tau (His-K18ΔK280) that forms stable, toxic, oligomeric tau aggregates in vitro. We show that (−)-epigallocatechin gallate (EGCG), a green tea polyphenol that was previously found to reduce Aβ aggregation, inhibits the aggregation of tau K18ΔK280 into toxic oligomers at ten- to hundred-fold substoichiometric concentrations, thereby rescuing toxicity in neuronal model cells. PMID:25436420

  18. On the Cyclo-Depolymerization of Alkyl Aromatic Polyesters and the in Situ Polymerization of the Cyclic Oligomers Produced

    NASA Astrophysics Data System (ADS)

    Alessi, M.; Stagnaro, P.; Conzatti, L.; Scafati, S. Tagliatatela; Hodge, P.

    2008-08-01

    Macrocyclic oligomers (MCOs) of some commercial alkyl aromatic polyesters (PET, PTT, PBT) were prepared by cyclo-depolymerization (CDP) of the polymers in refluxing 1, 2-dichlorobenzene with di-n-butyltin oxide as a transesterification catalyst. The mixtures of MCOs and residual polymer obtained at varying polymer/solvent ratios were separated and characterized by thorough GPC and DSC analyses. The higher the initial polymer concentration the lower was the yield of MCOs, and vice versa. Rheological measurements carried out on polymer/MCO mixtures showed a decrease in the melt viscosity with increasing amount of MCOs. Moreover, the MCOs present in these systems easily underwent entropically-driven ring-opening polymerizations (ED-ROPs) to reform the parent polyesters.

  19. Amylin-Aβ oligomers at atomic resolution using molecular dynamics simulations: a link between Type 2 diabetes and Alzheimer's disease

    PubMed Central

    Baram, Michal; Atsmon-Raz, Yoav; Ma, Buyong; Nussinov, Ruth; Miller, Yifat

    2015-01-01

    Clinical studies identified Type 2 diabetes (T2D) as a risk factor of Alzheimer's disease (AD). One of the potential mechanisms that link T2D and AD is the loss of cells associated with degenerative changes. Amylin1-37 aggregates (the pathological species in T2D) were found to be co-localized with those of Aβ1-42 (the pathological species in AD) to form the Amylin1-37-Aβ1-42 plaques, promoting aggregation and thus contributing to the etiology of AD. However, the mechanisms by which Amylin1-37 co-aggregate with Aβ1-42 are still elusive. This work presents the interactions between Amylin1-37 oligomers and Aβ1-42 oligomers at atomic resolution applying extensive molecular dynamics simulations for relatively large ensemble of cross-seeding Amylin1-37 -Aβ1-42 oligomers. The main conclusions of this study are first, Aβ1-42 oligomers prefer to interact with Amylin1-37 oligomers to form single layer conformations (in-register interactions) rather than double layer conformations; and second, in some double layer conformations of the cross-seeding Amylin1-37 -Aβ1-42 oligomers, the Amylin1-37 oligomers destabilize the Aβ1-42 oligomers and thus inhibit Aβ1-42 aggregation, while in other double layer conformations, the Amylin1-37 oligomers stabilize Aβ1-42 oligomers and thus promote Aβ1-42 aggregation. PMID:26349542

  20. The MitCHAP-60 disease is due to entropic destabilization of the human mitochondrial Hsp60 oligomer.

    PubMed

    Parnas, Avital; Nadler, Michal; Nisemblat, Shahar; Horovitz, Amnon; Mandel, Hanna; Azem, Abdussalam

    2009-10-01

    The 60-kDa heat shock protein (mHsp60) is a vital cellular complex that mediates the folding of many of the mitochondrial proteins. Its function is executed in cooperation with the co-chaperonin, mHsp10, and requires ATP. Recently, the discovery of a new mHsp60-associated neurodegenerative disorder, MitCHAP-60 disease, has been reported. The disease is caused by a point mutation at position 3 (D3G) of the mature mitochondrial Hsp60 protein, which renders it unable to complement the deletion of the homologous bacterial protein in Escherichia coli (Magen, D., Georgopoulos, C., Bross, P., Ang, D., Segev, Y., Goldsher, D., Nemirovski, A., Shahar, E., Ravid, S., Luder, A., Heno, B., Gershoni-Baruch, R., Skorecki, K., and Mandel, H. (2008) Am. J. Hum. Genet. 83, 30-42). The molecular basis of the MitCHAP-60 disease is still unknown. In this study, we present an in vitro structural and functional analysis of the purified wild-type human mHsp60 and the MitCHAP-60 mutant. We show that the D3G mutation leads to destabilization of the mHsp60 oligomer and causes its disassembly at low protein concentrations. We also show that the mutant protein has impaired protein folding and ATPase activities. An additional mutant that lacks the first three amino acids (N-del), including Asp-3, is similarly impaired in refolding activity. Surprisingly, however, this mutant exhibits profound stabilization of its oligomeric structure. These results suggest that the D3G mutation leads to entropic destabilization of the mHsp60 oligomer, which severely impairs its chaperone function, thereby causing the disease. PMID:19706612

  1. The MitCHAP-60 Disease Is Due to Entropic Destabilization of the Human Mitochondrial Hsp60 Oligomer*

    PubMed Central

    Parnas, Avital; Nadler, Michal; Nisemblat, Shahar; Horovitz, Amnon; Mandel, Hanna; Azem, Abdussalam

    2009-01-01

    The 60-kDa heat shock protein (mHsp60) is a vital cellular complex that mediates the folding of many of the mitochondrial proteins. Its function is executed in cooperation with the co-chaperonin, mHsp10, and requires ATP. Recently, the discovery of a new mHsp60-associated neurodegenerative disorder, MitCHAP-60 disease, has been reported. The disease is caused by a point mutation at position 3 (D3G) of the mature mitochondrial Hsp60 protein, which renders it unable to complement the deletion of the homologous bacterial protein in Escherichia coli (Magen, D., Georgopoulos, C., Bross, P., Ang, D., Segev, Y., Goldsher, D., Nemirovski, A., Shahar, E., Ravid, S., Luder, A., Heno, B., Gershoni-Baruch, R., Skorecki, K., and Mandel, H. (2008) Am. J. Hum. Genet. 83, 30–42). The molecular basis of the MitCHAP-60 disease is still unknown. In this study, we present an in vitro structural and functional analysis of the purified wild-type human mHsp60 and the MitCHAP-60 mutant. We show that the D3G mutation leads to destabilization of the mHsp60 oligomer and causes its disassembly at low protein concentrations. We also show that the mutant protein has impaired protein folding and ATPase activities. An additional mutant that lacks the first three amino acids (N-del), including Asp-3, is similarly impaired in refolding activity. Surprisingly, however, this mutant exhibits profound stabilization of its oligomeric structure. These results suggest that the D3G mutation leads to entropic destabilization of the mHsp60 oligomer, which severely impairs its chaperone function, thereby causing the disease. PMID:19706612

  2. Nanoscale Synaptic Membrane Mimetic Allows Unbiased High Throughput Screen That Targets Binding Sites for Alzheimer’s-Associated Aβ Oligomers

    PubMed Central

    Wilcox, Kyle C.; Marunde, Matthew R.; Das, Aditi; Velasco, Pauline T.; Kuhns, Benjamin D.; Marty, Michael T.; Jiang, Haoming; Luan, Chi-Hao; Sligar, Stephen G.; Klein, William L.

    2015-01-01

    Despite their value as sources of therapeutic drug targets, membrane proteomes are largely inaccessible to high-throughput screening (HTS) tools designed for soluble proteins. An important example comprises the membrane proteins that bind amyloid β oligomers (AβOs). AβOs are neurotoxic ligands thought to instigate the synapse damage that leads to Alzheimer’s dementia. At present, the identities of initial AβO binding sites are highly uncertain, largely because of extensive protein-protein interactions that occur following attachment of AβOs to surface membranes. Here, we show that AβO binding sites can be obtained in a state suitable for unbiased HTS by encapsulating the solubilized synaptic membrane proteome into nanoscale lipid bilayers (Nanodiscs). This method gives a soluble membrane protein library (SMPL)—a collection of individualized synaptic proteins in a soluble state. Proteins within SMPL Nanodiscs showed enzymatic and ligand binding activity consistent with conformational integrity. AβOs were found to bind SMPL Nanodiscs with high affinity and specificity, with binding dependent on intact synaptic membrane proteins, and selective for the higher molecular weight oligomers known to accumulate at synapses. Combining SMPL Nanodiscs with a mix-incubate-read chemiluminescence assay provided a solution-based HTS platform to discover antagonists of AβO binding. Screening a library of 2700 drug-like compounds and natural products yielded one compound that potently reduced AβO binding to SMPL Nanodiscs, synaptosomes, and synapses in nerve cell cultures. Although not a therapeutic candidate, this small molecule inhibitor of synaptic AβO binding will provide a useful experimental antagonist for future mechanistic studies of AβOs in Alzheimer’s model systems. Overall, results provide proof of concept for using SMPLs in high throughput screening for AβO binding antagonists, and illustrate in general how a SMPL Nanodisc system can facilitate drug

  3. Television Quiz Show Simulation

    ERIC Educational Resources Information Center

    Hill, Jonnie Lynn

    2007-01-01

    This article explores the simulation of four television quiz shows for students in China studying English as a foreign language (EFL). It discusses the adaptation and implementation of television quiz shows and how the students reacted to them.

  4. Synthetic Antimicrobial Oligomers Induce a Composition-Dependent Topological Transition in Membranes

    SciTech Connect

    Yang, L.; Gordon, V.D.; Mishra, A.; Som, A.; Purdy, K.R.; Davis, M.A.; Tew, G.N.; Wong, G.C.L.

    2009-06-04

    Antimicrobial peptides (AMPs) are cationic amphiphiles that comprise a key component of innate immunity. Synthetic analogues of AMPs, such as the family of phenylene ethynylene antimicrobial oligomers (AMOs), recently demonstrated broad-spectrum antimicrobial activity, but the underlying molecular mechanism is unknown. Homologues in this family can be inactive, specifically active against bacteria, or nonspecifically active against bacteria and eukaryotic cells. Using synchrotron small-angle X-ray scattering (SAXS), we show that observed antibacterial activity correlates with an AMO-induced topological transition of small unilamellar vesicles into an inverted hexagonal phase, in which hexagonal arrays of 3.4-nm water channels defined by lipid tubes are formed. Polarized and fluorescence microscopy show that AMO-treated giant unilamellar vesicles remain intact, instead of reconstructing into a bulk 3D phase, but are selectively permeable to encapsulated macromolecules that are smaller than 3.4 nm. Moreover, AMOs with different activity profiles require different minimum threshold concentrations of phosphoethanolamine (PE) lipids to reconstruct the membrane. Using ternary membrane vesicles composed of DOPG:DOPE:DOPC with a charge density fixed at typical bacterial values, we find that the inactive AMO cannot generate the inverted hexagonal phase even when DOPE completely replaces DOPC. The specifically active AMO requires a threshold ratio of DOPE:DOPC = 4:1, and the nonspecifically active AMO requires a drastically lower threshold ratio of DOPE:DOPC = 1.5:1. Since most gram-negative bacterial membranes have more PE lipids than do eukaryotic membranes, our results imply that there is a relationship between negative-curvature lipids such as PE and antimicrobial hydrophobicity that contributes to selective antimicrobial activity.

  5. Allosteric modulation in monomers and oligomers of a G protein-coupled receptor

    PubMed Central

    Shivnaraine, Rabindra V; Kelly, Brendan; Sankar, Krishana S; Redka, Dar'ya S; Han, Yi Rang; Huang, Fei; Elmslie, Gwendolynne; Pinto, Daniel; Li, Yuchong; Rocheleau, Jonathan V; Gradinaru, Claudiu C; Ellis, John; Wells, James W

    2016-01-01

    The M2 muscarinic receptor is the prototypic model of allostery in GPCRs, yet the molecular and the supramolecular determinants of such effects are unknown. Monomers and oligomers of the M2 muscarinic receptor therefore have been compared to identify those allosteric properties that are gained in oligomers. Allosteric interactions were monitored by means of a FRET-based sensor of conformation at the allosteric site and in pharmacological assays involving mutants engineered to preclude intramolecular effects. Electrostatic, steric, and conformational determinants of allostery at the atomic level were examined in molecular dynamics simulations. Allosteric effects in monomers were exclusively negative and derived primarily from intramolecular electrostatic repulsion between the allosteric and orthosteric ligands. Allosteric effects in oligomers could be positive or negative, depending upon the allosteric-orthosteric pair, and they arose from interactions within and between the constituent protomers. The complex behavior of oligomers is characteristic of muscarinic receptors in myocardial preparations. DOI: http://dx.doi.org/10.7554/eLife.11685.001 PMID:27151542

  6. Chemistry and properties of imide oligomers containing pendant and terminal phenylethynyl groups

    SciTech Connect

    Smith, J.G. Jr.

    1996-12-31

    As part of a continuing effort to develop high performance/high temperature structural resins for aeronautical applications, oligomers containing latent reactive groups have been under investigation. Material requirements include ease of processability, retention of mechanical properties at elevated temperature, and no loss of mechanical properties after exposure to aircraft fluids such as hydraulic fluid, jet fuel, and cleaning fluids. The phenylethynyl group is an ideal latent reactive group. It has a relatively high cure temperature ({approximately}350{degrees}C) and a large processing window can be obtained with materials possessing the proper glass transition temperature. The thermally cured materials exhibit good retention of mechanical properties at elevated temperatures with no significant loss of properties after exposure to various solvents. To date, the phenylethynyl group has been incorporated either terminal or pendant to a variety of imide oligomers. Upon thermal cure, the phenylethynyl group undergoes chain extension, branching and/or crosslinking; however, the final cured product has not been well defined. As an extension of this work, a series of imide oligomers containing both pendant and terminal phenylethynyl groups (PTPEIs) were prepared as a means to improve retention of mechanical properties at elevated temperature while maintaining processability. The PTPEI oligomers were characterized, thermally cured and the cured polymers evaluated as unoriented thin films and adhesives. The chemistry, physical, and mechanical properties of these materials will be discussed.

  7. Cognitive effects of cell-derived and synthetically-derived Aβ oligomers

    PubMed Central

    Reed, Miranda N.; Hofmeister, Jacki J.; Jungbauer, Lisa; Welzel, Alfred T.; Yu, Chunjiang; Sherman, Mathew A.; Lesné, Sylvain; LaDu, Mary Jo; Walsh, Dominic M.; Ashe, Karen H.; Cleary, James P.

    2010-01-01

    Soluble forms of amyloid-β peptide (Aβ) are a molecular focus in Alzheimer's disease research. Soluble Aβ dimers (≈ 8 kDa), timers (≈ 12 kDa), tetramers (≈ 16 kDa) and Aβ*56 (≈ 56 kDa) have shown biological activity. These Aβ molecules have been derived from diverse sources, including chemical synthesis, transfected cells, and mouse and human brain, leading to uncertainty about toxicity and potency. Herein, synthetic Aβ peptide-derived oligomers, cell- and brain-derived low-n oligomers, and Aβ*56, were injected intracerebroventricularly (icv) into rats assayed under the Alternating Lever Cyclic Ratio (ALCR) cognitive assay. Cognitive deficits were detected at 1.3μM of synthetic Aβ oligomers and at low nanomolar concentrations of cell-secreted Aβ oligomers. Trimers, from transgenic mouse brain (Tg2576), did not cause cognitive impairment at any dose tested, whereas Aβ*56 induced concentration-dependent cognitive impairment at 0.9μM and 1.3μM. Thus, while multiple forms of Aβ have cognition impairing activity, there are significant differences in effective concentration and potency. PMID:20031278

  8. The Effect of Molecular Weight on the Composite Properties of Cured Phenylethynyl Terminated Imide Oligomers

    NASA Technical Reports Server (NTRS)

    Smith, J. G., Jr.; Connell, J. W.; Hergenrother, P. M.

    1997-01-01

    As part of a program to develop high temperature/high performance structural resins for aeronautical applications, imide oligomers containing terminal phenylethynyl groups with calculated number average molecular weights of 1250, 2500 and 5000 g/mol were prepared, characterized, and evaluated as adhesives and composite matrix resins. The goal of this work was to develop resin systems that are processable using conventional processing equipment into void free composites that exhibit high mechanical properties with long term high temperature durability, and are not affected by exposure to common aircraft fluids. The imide oligomers containing terminal phenylethynyl groups were fabricated into titanium adhesive specimens and IM-7 carbon fiber laminates under 0.1 - 1.4 MPa for 1 hr at 350-371 C. The lower molecular weight oligomers exhibited higher cured Tg, better processability, and better retention of mechanical properties at elevated temperature without significantly sacrificing toughness or damage tolerance than the higher molecular weight oligomer. The neat resin, adhesive and composite properties of the cured polymers will be presented.

  9. Diverse Metastable Structures Formed by Small Oligomers of α-Synuclein Probed by Force Spectroscopy

    PubMed Central

    Sosova, Iveta; Belov, Miro; Woodside, Michael T.

    2014-01-01

    Oligomeric aggregates are widely suspected as toxic agents in diseases caused by protein aggregation, yet they remain poorly characterized, partly because they are challenging to isolate from a heterogeneous mixture of species. We developed an assay for characterizing structure, stability, and kinetics of individual oligomers at high resolution and sensitivity using single-molecule force spectroscopy, and applied it to observe the formation of transient structured aggregates within single oligomers of α-synuclein, an intrinsically-disordered protein linked to Parkinson’s disease. Measurements of the molecular extension as the proteins unfolded under tension in optical tweezers revealed that even small oligomers could form numerous metastable structures, with a surprisingly broad range of sizes. Comparing the structures formed in monomers, dimers and tetramers, we found that the average mechanical stability increased with oligomer size. Most structures formed within a minute, with size-dependent rates. These results provide a new window onto the complex α-synuclein aggregation landscape, characterizing the microscopic structural heterogeneity and kinetics of different pathways. PMID:24475132

  10. Oligomers with pendant isocyanate groups as adhesives for dentin and other tissues.

    PubMed

    Lee, C H; Brauer, G M

    1989-03-01

    Oligomers containing pendant isocyanate groups were synthesized from various vinyl monomers, m-isopropenyldimethylbenzyl isocyanate (TMI), and 2-isocyanatoethyl methacrylate (IEM). The liquids were characterized by their refractive indices, infrared spectra, and percentage of isocynate groups in the molecule. Adhesive properties of these compounds were compared with those of oligomers prepared from methacrylate esters, IEM, and/or TMI which had been synthesized previously. Bond strengths of the sodium salt of ethylenediamine-tetraacetic acid (Na2EDTA adjusted to pH 7.4) and glutaraldehyde-treated dentin cemented to composite resin with dilute solutions of the oligomers and then stored in water were determined by the procedure of Kemper and Kilian (1975). These adhesive compositions, especially formulations synthesized from vinyl monomers, adhered at least as well to dentin as did other dentin bonding agents. Oligomers synthesized with methacrylate esters bonded more strongly to bone than did other hard-tissue adhesives. These oligomeric compositions are also excellent soft-tissue adhesives. For example, they provide a strong bond between a collagenous substrate (such as calfskin) and cured denture-base resin. Provided that their biological properties prove satisfactory, these compositions could find many applications as hard- and soft-tissue adhesives in clinical dentistry. PMID:2921392

  11. Development of new fusion proteins for visualizing amyloid-β oligomers in vivo

    PubMed Central

    Ochiishi, Tomoyo; Doi, Motomichi; Yamasaki, Kazuhiko; Hirose, Keiko; Kitamura, Akira; Urabe, Takao; Hattori, Nobutaka; Kinjo, Masataka; Ebihara, Tatsuhiko; Shimura, Hideki

    2016-01-01

    The intracellular accumulation of amyloid-β (Aβ) oligomers critically contributes to disease progression in Alzheimer’s disease (AD) and can be the potential target of AD therapy. Direct observation of molecular dynamics of Aβ oligomers in vivo is key for drug discovery research, however, it has been challenging because Aβ aggregation inhibits the fluorescence from fusion proteins. Here, we developed Aβ1-42-GFP fusion proteins that are oligomerized and visualize their dynamics inside cells even when aggregated. We examined the aggregation states of Aβ-GFP fusion proteins using several methods and confirmed that they did not assemble into fibrils, but instead formed oligomers in vitro and in live cells. By arranging the length of the liker between Aβ and GFP, we generated two fusion proteins with “a long-linker” and “a short-linker”, and revealed that the aggregation property of fusion proteins can be evaluated by measuring fluorescence intensities using rat primary culture neurons transfected with Aβ-GFP plasmids and Aβ-GFP transgenic C. elegans. We found that Aβ-GFP fusion proteins induced cell death in COS7 cells. These results suggested that novel Aβ-GFP fusion proteins could be utilized for studying the physiological functions of Aβ oligomers in living cells and animals, and for drug screening by analyzing Aβ toxicity. PMID:26982553

  12. UV curable lens production using molecular weight controlled PEEK based acrylic oligomer (Ac-PEEK).

    PubMed

    İnan, Tulay Y; Yıldız, Emel; Karaca, Birsen; Dogan, Hacer; Vatansever, Alican; Nalbant, Muhammed; Eken, Koray

    2014-08-01

    We produced UV curable lenses with properties blocking short wave UV light. In the UV-curable formulations, we used an oligomer (Ac-PEEK) with another urethan oligomer (Mw = 2000). Radically active, molecular weight controlled Ac-PEEK was obtained by reacting 2-hydroxyl ethyl methacrylate with molecular- weight- controlled and isocyanate terminated PEEK (Mn = 4500). We characterized all synthesized monomer, oligomer and optical materials with UV/Vis spectrophotometer with interferogram, elemental analyser, mass spectrophotometer, proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermal gravimetric analyzer, differential scanning calorimeter, scanning electron microscopy and gas chromatography. Results suggested that newly synthesized oligomer with the structure of PEEK absorbs short wave UV-light. Ageing tests [ISO 11979-5, Ophthalmic implants-intraocular lenses (IOL)-Part 5: Biocompatibility] performed on the IOL materials were successful. High contact angle of the obtained lenses suggests that all lenses were hydrophobic and SEM results revealed that lenses are morphologically homogeneous. Based on all positive properties just mentioned, we safely conclude that the lenses produced in this study are very promising for IOL production. PMID:24796625

  13. Structural characterization of toxic oligomers that are kinetically trapped during α-synuclein fibril formation

    PubMed Central

    Chen, Serene W.; Drakulic, Srdja; Deas, Emma; Ouberai, Myriam; Aprile, Francesco A.; Arranz, Rocío; Ness, Samuel; Roodveldt, Cintia; Guilliams, Tim; De-Genst, Erwin J.; Klenerman, David; Wood, Nicholas W.; Knowles, Tuomas P.J.; Alfonso, Carlos; Rivas, Germán; Abramov, Andrey Y.; Valpuesta, José María; Dobson, Christopher M.; Cremades, Nunilo

    2015-01-01

    We describe the isolation and detailed structural characterization of stable toxic oligomers of α-synuclein that have accumulated during the process of amyloid formation. Our approach has allowed us to identify distinct subgroups of oligomers and to probe their molecular architectures by using cryo-electron microscopy (cryoEM) image reconstruction techniques. Although the oligomers exist in a range of sizes, with different extents and nature of β-sheet content and exposed hydrophobicity, they all possess a hollow cylindrical architecture with similarities to certain types of amyloid fibril, suggesting that the accumulation of at least some forms of amyloid oligomers is likely to be a consequence of very slow rates of rearrangement of their β-sheet structures. Our findings reveal the inherent multiplicity of the process of protein misfolding and the key role the β-sheet geometry acquired in the early stages of the self-assembly process plays in dictating the kinetic stability and the pathological nature of individual oligomeric species. PMID:25855634

  14. DFT calculation of the electronic properties of fluorene-1,3,4-thiadiazole oligomers.

    PubMed

    Sánchez-Bojorge, Nora Aydeé; Rodríguez-Valdez, Luz María; Flores-Holguín, Norma

    2013-09-01

    Thiadiazole derivatives have been widely employed in the areas of pharmaceutical, agricultural, industrial, and polymer chemistry. The electronic and molecular structures of thiadiazoles are of interest because they have an equal number of valence electrons and similar molecular structures to thiophenes, which are currently used in the construction of organic solar cells due to their relatively high hole mobilities and good light-harvesting properties. For this reason, the electronic properties of fluorene-1,3,4-thiadiazole oligomers warrant investigation. In the present work, the structure of fluorene-1,3,4-thiadiazole with one thiadiazole unit in the structure was analyzed. This molecule was then expanded until there were 10 thiadiazole units in the structure. The band gap, HOMO and LUMO distributions, and absorption spectrum were analyzed for each molecule. All calculations were performed by applying the B3LYP/6-31G(d) chemical model in the Gaussian 03W and GaussView software packages. The electronic properties were observed to significantly enhance as the number of monomeric units increased, which also caused the gap energy to decrease from 3.51 eV in the oligomer with just one thiadiazole ring to 2.33 eV in the oligomer with 10 units. The HOMO and LUMO regions were well defined and separated for oligomers with at least 5 monomer units of thiadiazole. PMID:23722558

  15. Styrene-terminated polysulfone oligomers as matrix material for graphite reinforced composites - An initial study

    NASA Technical Reports Server (NTRS)

    Garcia, Dana; Bowles, Kenneth J.; Vannucci, Raymond D.

    1987-01-01

    Results pertaining to graphite reinforced composites containing styrene-terminated oligomers as the matrix material are summarized. The processing parameters are determined and the properties of the resulting composite are evaluated. In terms of solvent impregnation techniques, CH2Cl2 is the preferred solvent due to its easy removal during the prepreg drying and consolidation steps.

  16. Development of new fusion proteins for visualizing amyloid-β oligomers in vivo.

    PubMed

    Ochiishi, Tomoyo; Doi, Motomichi; Yamasaki, Kazuhiko; Hirose, Keiko; Kitamura, Akira; Urabe, Takao; Hattori, Nobutaka; Kinjo, Masataka; Ebihara, Tatsuhiko; Shimura, Hideki

    2016-01-01

    The intracellular accumulation of amyloid-β (Aβ) oligomers critically contributes to disease progression in Alzheimer's disease (AD) and can be the potential target of AD therapy. Direct observation of molecular dynamics of Aβ oligomers in vivo is key for drug discovery research, however, it has been challenging because Aβ aggregation inhibits the fluorescence from fusion proteins. Here, we developed Aβ1-42-GFP fusion proteins that are oligomerized and visualize their dynamics inside cells even when aggregated. We examined the aggregation states of Aβ-GFP fusion proteins using several methods and confirmed that they did not assemble into fibrils, but instead formed oligomers in vitro and in live cells. By arranging the length of the liker between Aβ and GFP, we generated two fusion proteins with "a long-linker" and "a short-linker", and revealed that the aggregation property of fusion proteins can be evaluated by measuring fluorescence intensities using rat primary culture neurons transfected with Aβ-GFP plasmids and Aβ-GFP transgenic C. elegans. We found that Aβ-GFP fusion proteins induced cell death in COS7 cells. These results suggested that novel Aβ-GFP fusion proteins could be utilized for studying the physiological functions of Aβ oligomers in living cells and animals, and for drug screening by analyzing Aβ toxicity. PMID:26982553

  17. A simple procedure for preparing chitin oligomers through acetone precipitation after hydrolysis in concentrated hydrochloric acid.

    PubMed

    Kazami, Nao; Sakaguchi, Masayoshi; Mizutani, Daisuke; Masuda, Tatsuhiko; Wakita, Satoshi; Oyama, Fumitaka; Kawakita, Masao; Sugahara, Yasusato

    2015-11-01

    Chitin oligomers are of interest because of their numerous biologically relevant properties. To prepare chitin oligomers containing 4-6 GlcNAc units [(GlcNAc)4-6], α- and β-chitin were hydrolyzed with concentrated hydrochloric acid at 40 °C. The reactant was mixed with acetone to recover the acetone-insoluble material, and (GlcNAc)4-6 was efficiently recovered after subsequent water extraction. Composition analysis using gel permeation chromatography and MALDI-TOF mass spectrometry indicated that (GlcNAc)4-6 could be isolated from the acetone-insoluble material with recoveries of approximately 17% and 21% from the starting α-chitin and β-chitin, respectively. The acetone precipitation method is highly useful for recovering chitin oligomers from the acid hydrolysate of chitin. The changes in the molecular size and higher-order structure of chitin during the course of hydrolysis were also analyzed, and a model that explains the process of oligomer accumulation is proposed. PMID:26256353

  18. Student-Driven Design of Peptide Mimetics: Microwave-Assisted Synthesis of Peptoid Oligomers

    ERIC Educational Resources Information Center

    Pohl, Nicola L. B.; Kirshenbaum, Kent; Yoo, Barney; Schulz, Nathan; Zea, Corbin J.; Streff, Jennifer M.; Schwarz, Kimberly L.

    2011-01-01

    An experiment for the undergraduate organic laboratory is described in which peptide mimetic oligomers called "peptoids" are built stepwise on a solid-phase resin. Students employ two modern strategies to facilitate rapid multistep syntheses: solid-phase techniques to obviate the need for intermediate purifications and microwave irradiation to…

  19. Stabilizing Off-pathway Oligomers by Polyphenol Nanoassemblies for IAPP Aggregation Inhibition

    PubMed Central

    Nedumpully-Govindan, Praveen; Kakinen, Aleksandr; Pilkington, Emily H.; Davis, Thomas P.; Chun Ke, Pu; Ding, Feng

    2016-01-01

    Experimental studies have shown that many naturally occurring polyphenols have inhibitory effect on the aggregation of several proteins. Here, we use discrete molecular dynamics (DMD) simulations and high-throughput dynamic light scattering (DLS) experiments to study the anti-aggregation effects of two polyphenols, curcumin and resveratrol, on the aggregation of islet amyloid polypeptide (IAPP or amylin). Our DMD simulations suggest that the aggregation inhibition is caused by stabilization of small molecular weight IAPP off-pathway oligomers by the polyphenols. Our analysis indicates that IAPP-polyphenol hydrogen bonds and π-π stacking combined with hydrophobic interactions are responsible for the stabilization of oligomers. The presence of small oligomers is confirmed with DLS measurements in which nanometer-sized oligomers are found to be stable for up to 7.5 hours, the time frame within which IAPP aggregates in the absence of polyphenols. Our study offers a general anti-aggregation mechanism for polyphenols, and further provides a computational framework for the future design of anti-amyloid aggregation therapeutics. PMID:26763863

  20. A method for the 32P labeling of peptides or peptide nucleic acid oligomers

    NASA Technical Reports Server (NTRS)

    Kozlov, I. A.; Nielsen, P. E.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1998-01-01

    A novel approach to the radioactive labeling of peptides and PNA oligomers is described. It is based on the conjugation of a deoxynucleoside 3'-phosphate with the terminal amine of the substrate, followed by phosphorylation of the 5'-hydroxyl group of the nucleotide using T4 polynucleotide kinase and [gamma-32P]ATP.

  1. Parkinson's Disease with Fatigue: Clinical Characteristics and Potential Mechanisms Relevant to α-Synuclein Oligomer

    PubMed Central

    Zuo, Li-Jun; Yu, Shu-Yang; Wang, Fang; Hu, Yang; Piao, Ying-Shan; Du, Yang; Lian, Teng-Hong; Wang, Rui-Dan; Yu, Qiu-Jin; Wang, Ya-Jie; Wang, Xiao-Min; Chan, Piu; Chen, Sheng-Di; Wang, Yongjun

    2016-01-01

    Background and Purpose The aim of this study was to identify the clinical characteristics and potential mechanisms relevant to pathological proteins in Parkinson's disease (PD) patients who experience fatigue. Methods PD patients (n=102) were evaluated using a fatigue severity scale and scales for motor and nonmotor symptoms. The levels of three pathological proteins—α-synuclein oligomer, β-amyloid (Aβ)1-42, and tau—were measured in 102 cerebrospinal fluid (CSF) samples from these PD patients. Linear regression analyses were performed between fatigue score and the CSF levels of the above-listed pathological proteins in PD patients. Results The frequency of fatigue in the PD patients was 62.75%. The fatigue group had worse motor symptoms and anxiety, depression, and autonomic dysfunction. The CSF level of α-synuclein oligomer was higher and that of Aβ1-42 was lower in the fatigue group than in the non-fatigue group. In multiple linear regression analyses, fatigue severity was significantly and positively correlated with the α-synuclein oligomer level in the CSF of PD patients, after adjusting for confounders. Conclusions PD patients experience a high frequency of fatigue. PD patients with fatigue have worse motor and part nonmotor symptoms. Fatigue in PD patients is associated with an increased α-synuclein oligomer level in the CSF. PMID:26869370

  2. Synthesis and characterization of an isoindigo-dithienocarbazole-isoindigo oligomer for organic solar cells

    NASA Astrophysics Data System (ADS)

    Lyu, Fuzhen; Park, Hanok; Lee, Soo-Hyoung; Lee, Sang Hee; Lee, Youn-Sik

    2014-08-01

    An isoindigo-dithienocarbazole-isoindigo oligomer (II-DTC-II) was synthesized by a Stille coupling reaction between N-hexadecyl-2,8-bis(trimethylstannyl)dithieno[3,2-b:6,7-b]carbazole and 6-bromo-N,N‧-dioctylisoindigo. The oligomer exhibited a broad absorption with an optical band gap of 1.75 eV and a highest occupied molecular orbital energy level of -5.46 eV. Photovoltaic devices were fabricated using the II-DTC-II oligomer and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM), to obtain the configuration ITO/PEDOT:PSS/II-DTC-II:PC71BM/LiF/Al. The best power conversion efficiency of the II-DTC-II-based devices was 1.13% when 0.8 wt% diiodooctane was mixed into the active layer of II-DTC-II/PC71BM (1:1). The low conversion efficiency was attributed to the oligomer's poor solubility and miscibility with PC71BM.

  3. Stabilizing Off-pathway Oligomers by Polyphenol Nanoassemblies for IAPP Aggregation Inhibition.

    PubMed

    Nedumpully-Govindan, Praveen; Kakinen, Aleksandr; Pilkington, Emily H; Davis, Thomas P; Chun Ke, Pu; Ding, Feng

    2016-01-01

    Experimental studies have shown that many naturally occurring polyphenols have inhibitory effect on the aggregation of several proteins. Here, we use discrete molecular dynamics (DMD) simulations and high-throughput dynamic light scattering (DLS) experiments to study the anti-aggregation effects of two polyphenols, curcumin and resveratrol, on the aggregation of islet amyloid polypeptide (IAPP or amylin). Our DMD simulations suggest that the aggregation inhibition is caused by stabilization of small molecular weight IAPP off-pathway oligomers by the polyphenols. Our analysis indicates that IAPP-polyphenol hydrogen bonds and π-π stacking combined with hydrophobic interactions are responsible for the stabilization of oligomers. The presence of small oligomers is confirmed with DLS measurements in which nanometer-sized oligomers are found to be stable for up to 7.5 hours, the time frame within which IAPP aggregates in the absence of polyphenols. Our study offers a general anti-aggregation mechanism for polyphenols, and further provides a computational framework for the future design of anti-amyloid aggregation therapeutics. PMID:26763863

  4. Secondary Ion Mass Spectrometry of Zeolite Materials: Observation of Abundant Aluminosilicate Oligomers Using an Ion Trap

    SciTech Connect

    Groenewold, Gary Steven; Kessinger, Glen Frank; Scott, Jill Rennee; Gianotto, Anita Kay; Appelhans, Anthony David; Delmore, James Edward

    2000-12-01

    Oligomeric oxyanions were observed in the secondary ion mass spectra (SIMS) of zeolite materials. The oxyanions have the general composition AlmSinO2(m+n)H(m-1)- (m + n = 2 to 8) and are termed dehydrates. For a given mass, multiple elemental compositions are possible because (Al + H) is an isovalent and isobaric substitute for Si. Using 18 keV Ga+ as a projectile, oligomer abundances are low relative to the monomers. Oligomer abundance can be increased by using the polyatomic projectile ReO4- (~5 keV). Oligomer abundance can be further increased using an ion trap (IT-) SIMS; in this instrument, long ion lifetimes (tens of ms) and relatively high He pressure result in significant collisional stabilization and increased high-mass abundance. The dehydrates rapidly react with adventitious H2O present in the IT-SIMS to form mono-, di-, and trihydrates. The rapidity of the reaction and comparison to aluminum oxyanion hydration suggest that H2O adds to the aluminosilicate oxyanions in a dissociative fashion, forming covalently bound product ions. In addition to these findings, it was noted that production of abundant oligomeric aluminosilicates could be significantly increased by substituting the countercation (NH4+) with the larger alkali ions Rb+ and Cs+. This constitutes a useful tactic for generating large aluminosilicate oligomers for surface characterization and ion-molecule reactivity studies.

  5. Conformational Flexibility of Soluble Cellulose Oligomers: Chain Length and Temperature Dependence

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Structures, dynamics, and stabilities of different sized cellulosic oligomers need to be considered when designing enzymatic cocktails for the conversion of biomass to biofuels since they can be both productive substrates and inhibitors of the overall process. In the present work, the conformational...

  6. Chemical evolution. XXII - The hydantoins released on hydrolysis of HCN oligomers

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Wos, J. D.; Lobo, A. P.

    1974-01-01

    The isolation of three hydantoins from HCN oligomers is described. One of these hydantoins, 5-carboxymethylidine hydantoin (5-CMH), rearranges to pyrimidine orotic acid in basic solution. The isolation of 5-CMH suggests the possibility that pyrimidines were formed directly from HCN on the primitive earth.

  7. Rapid Multistep Synthesis of a Bioactive Peptidomimetic Oligomer for the Undergraduate Laboratory

    ERIC Educational Resources Information Center

    Utku, Yeliz; Rohatgi, Abhinav; Yoo, Barney; Kirshenbaum, Kent; Zuckermann, Ronald N.; Pohl, Nicola L.

    2010-01-01

    Peptidomimetic compounds are increasingly important in drug-discovery applications. We introduce the synthesis of an N-substituted glycine oligomer, a bioactive "peptoid" trimer. The six-step protocol is conducted on solid-phase resin, enabling the synthesis to be performed by undergraduate organic chemistry students. This synthesis lab was…

  8. The Wordpath Show.

    ERIC Educational Resources Information Center

    Anderton, Alice

    The Intertribal Wordpath Society is a nonprofit educational corporation formed to promote the teaching, status, awareness, and use of Oklahoma Indian languages. The Society produces "Wordpath," a weekly 30-minute public access television show about Oklahoma Indian languages and the people who are teaching and preserving them. The show aims to…

  9. The Familial British Dementia Mutation Promotes Formation of Neurotoxic Cystine Cross-linked Amyloid Bri (ABri) Oligomers*

    PubMed Central

    Cantlon, Adam; Frigerio, Carlo Sala; Freir, Darragh B.; Boland, Barry; Jin, Ming; Walsh, Dominic M.

    2015-01-01

    Familial British dementia (FBD) is an inherited neurodegenerative disease believed to result from a mutation in the BRI2 gene. Post-translational processing of wild type BRI2 and FBD-BRI2 result in the production of a 23-residue long Bri peptide and a 34-amino acid long ABri peptide, respectively, and ABri is found deposited in the brains of individuals with FBD. Similarities in the neuropathology and clinical presentation shared by FBD and Alzheimer disease (AD) have led some to suggest that ABri and the AD-associated amyloid β-protein (Aβ) are molecular equivalents that trigger analogous pathogenic cascades. But the sequences and innate properties of ABri and Aβ are quite different, notably ABri contains two cysteine residues that can form disulfide bonds. Thus we sought to determine whether ABri was neurotoxic and if this activity was regulated by oxidation and/or aggregation. Crucially, the type of oxidative cross-linking dramatically influenced both ABri aggregation and toxicity. Cyclization of Bri and ABri resulted in production of biologically inert monomers that showed no propensity to assemble, whereas reduced ABri and reduced Bri aggregated forming thioflavin T-positive amyloid fibrils that lacked significant toxic activity. ABri was more prone to form inter-molecular disulfide bonds than Bri and the formation of covalently stabilized ABri oligomers was associated with toxicity. These results suggest that extension of the C-terminal of Bri causes a shift in the type of disulfide bonds formed and that structures built from covalently cross-linked oligomers can interact with neurons and compromise their function and viability. PMID:25957407

  10. A graphical method for analyzing distance restraints using residual dipolar couplings for structure determination of symmetric protein homo-oligomers.

    PubMed

    Martin, Jeffrey W; Yan, Anthony K; Bailey-Kellogg, Chris; Zhou, Pei; Donald, Bruce R

    2011-06-01

    High-resolution structure determination of homo-oligomeric protein complexes remains a daunting task for NMR spectroscopists. Although isotope-filtered experiments allow separation of intermolecular NOEs from intramolecular NOEs and determination of the structure of each subunit within the oligomeric state, degenerate chemical shifts of equivalent nuclei from different subunits make it difficult to assign intermolecular NOEs to nuclei from specific pairs of subunits with certainty, hindering structural analysis of the oligomeric state. Here, we introduce a graphical method, DISCO, for the analysis of intermolecular distance restraints and structure determination of symmetric homo-oligomers using residual dipolar couplings. Based on knowledge that the symmetry axis of an oligomeric complex must be parallel to an eigenvector of the alignment tensor of residual dipolar couplings, we can represent distance restraints as annuli in a plane encoding the parameters of the symmetry axis. Oligomeric protein structures with the best restraint satisfaction correspond to regions of this plane with the greatest number of overlapping annuli. This graphical analysis yields a technique to characterize the complete set of oligomeric structures satisfying the distance restraints and to quantitatively evaluate the contribution of each distance restraint. We demonstrate our method for the trimeric E. coli diacylglycerol kinase, addressing the challenges in obtaining subunit assignments for distance restraints. We also demonstrate our method on a dimeric mutant of the immunoglobulin-binding domain B1 of streptococcal protein G to show the resilience of our method to ambiguous atom assignments. In both studies, DISCO computed oligomer structures with high accuracy despite using ambiguously assigned distance restraints. PMID:21413097

  11. Expression of the Native Cholera Toxin B Subunit Gene and Assembly as Functional Oligomers in Transgenic Tobacco Chloroplasts

    PubMed Central

    Daniell, Henry; Lee, Seung-Bum; Panchal, Tanvi; Wiebe, Peter O.

    2012-01-01

    The B subunits of enterotoxigenic Escherichia coli (LTB) and cholera toxin of Vibrio cholerae (CTB) are candidate vaccine antigens. Integration of an unmodified CTB-coding sequence into chloroplast genomes (up to 10,000 copies per cell), resulted in the accumulation of up to 4.1% of total soluble tobacco leaf protein as functional oligomers (410-fold higher expression levels than that of the unmodified LTB gene expressed via the nuclear genome). However, expresssion levels reported are an underestimation of actual accumulation of CTB in transgenic chloroplasts, due to aggregation of the oligomeric forms in unboiled samples similar to the aggregation observed for purified bacterial antigen. PCR and Southern blot analyses confirmed stable integration of the CTB gene into the chloroplast genome. Western blot analysis showed that the chloroplast-synthesized CTB assembled into oligomers and were antigenically identical with purified native CTB. Also, binding assays confirmed that chloroplast- synthesized CTB binds to the intestinal membrane GM1-ganglioside receptor, indicating correct folding and disulfide bond formation of CTB pentamers within transgenic chloroplasts. In contrast to stunted nuclear transgenic plants, chloroplast transgenic plants were morphologically indistinguishable from untransformed plants, when CTB was constitutively expressed in chloroplasts. Introduced genes were inherited stably in subsequent generations, as confirmed by PCR and Southern blot analyses. Increased production of an efficient transmucosal carrier molecule and delivery system, like CTB, in transgenic chloroplasts makes plant-based oral vaccines and fusion proteins with CTB needing oral administration commercially feasible. Successful expression of foreign genes in transgenic chromoplasts and availability of marker-free chloroplast transformation techniques augurs well for development of vaccines in edible parts of transgenic plants. Furthermore, since the quaternary structure of

  12. Native metastable prefibrillar oligomers are the most neurotoxic species among amyloid aggregates.

    PubMed

    Diociaiuti, Marco; Macchia, Gianfranco; Paradisi, Silvia; Frank, Claudio; Camerini, Serena; Chistolini, Pietro; Gaudiano, Maria Cristina; Petrucci, Tamara Corinna; Malchiodi-Albedi, Fiorella

    2014-09-01

    Many proteins belonging to the amyloid family share the tendency to misfold and aggregate following common steps, and display similar neurotoxicity. In the aggregation pathway different kinds of species are formed, including several types of oligomers and eventually mature fibers. It is now suggested that the pathogenic aggregates are not the mature fibrils, but the intermediate, soluble oligomers. Many kinds of aggregates have been described to exist in a metastable state and in equilibrium with monomers. Up to now it is not clear whether a specific structure is at the basis of the neurotoxicity. Here we characterized, starting from the early aggregation stages, the oligomer populations formed by an amyloid protein, salmon calcitonin (sCT), chosen due to its very slow aggregation rate. To prepare different oligomer populations and characterize them by means of photoinduced cross-linking SDS-PAGE, Energy Filtered-Transmission Electron Microscopy (EF-TEM) and Circular Dichroism (CD) spectroscopy, we used Size Exclusion Chromatography (SEC), a technique that does not influence the aggregation process leaving the protein in the native state. Taking advantage of sCT low aggregation rate, we characterized the neurotoxic potential of the SEC-separated, non-crosslinked fractions in cultured primary hippocampal neurons, analyzing intracellular Ca(2+) influx and apoptotic trend. We provide evidence that native, globular, metastable, prefibrillar oligomers (dimers, trimers and tetramers) were the toxic species and that low concentrations of these aggregates in the population was sufficient to render the sample neurotoxic. Monomers and other kind of aggregates, such as annular or linear protofibers and mature fibers, were totally biologically inactive. PMID:24932517

  13. Molecular insight into amyloid oligomer destabilizing mechanism of flavonoid derivative 2-(4' benzyloxyphenyl)-3-hydroxy-chromen-4-one through docking and molecular dynamics simulations.

    PubMed

    Kumar, Akhil; Srivastava, Swati; Tripathi, Shubhandra; Singh, Sandeep Kumar; Srikrishna, Saripella; Sharma, Ashok

    2016-06-01

    Aggregation of amyloid peptide (Aβ) has been shown to be directly related to progression of Alzheimer's disease (AD). Aβ is neurotoxic and its deposition and aggregation ultimately lead to cell death. In our previous work, we reported flavonoid derivative (compound 1) showing promising result in transgenic AD model of Drosophila. Compound 1 showed prevention of Aβ-induced neurotoxicity and neuroprotective efficacy in Drosophila system. However, mechanism of action of compound 1 and its effect on the amyloid is not known. We therefore performed molecular docking and atomistic, explicit-solvent molecular dynamics simulations to investigate the process of Aβ interaction, inhibition, and destabilizing mechanism. Results showed different preferred binding sites of compound 1 and good affinity toward the target. Through the course of 35 ns molecular dynamics simulation, conformations_5 of compound 1 intercalates into the hydrophobic core near the salt bridge and showed major structural changes as compared to other conformations. Compound 1 showed interference with the salt bridge and thus reducing the inter strand hydrogen bound network. This minimizes the side chain interaction between the chains A-B leading to disorder in oligomer. Contact map analysis of amino acid residues between chains A and B also showed lesser interaction with adjacent amino acids in the presence of compound 1 (conformations_5). The study provides an insight into how compound 1 interferes and disorders the Aβ peptide. These findings will further help to design better inhibitors for aggregation of the amyloid oligomer. PMID:26208790

  14. Molecular Interactions of Alzheimer Amyloid-β Oligomer with Neutral and Negatively Charged Lipid Bilayers

    PubMed Central

    Yu, Xiang; Wang, Qiuming; Pan, Qingfen; Zhou, Feimeng; Zheng, Jie

    2013-01-01

    Interaction of p3 (Aβ17-42) peptides with cell membrane is crucial for the understanding of amyloid toxicity associated with Alzheimer’s disease (AD). Such p3-membrane interactions are considered to induce the disruption of membrane permeability and integrity, but the exact mechanisms of how p3 aggregates, particularly small p3 oligomers, induce receptor-independent membrane disruption are not yet completely understood. Here, we investigate the adsorption, orientation, and surface interaction of the p3 pentamer with lipid bilayers composed of both pure zwitterionic POPC (palmitoyl-oleyl-phosphatidylcholine) and mixed anionic POPC/POPG (palmitoyl-oleyl-phosphatidylglycerol) (3:1) lipids using explicit-solvent molecular dynamics (MD) simulations. MD simulation results show that the p3 pentamer has much stronger interactions with mixed POPC/POPG lipids than pure POPC lipids, consistent with experimental observation that Aβ adsorption and fibrililation are enhanced on anionic lipid bilayers. Although electrostatic interactions are main attractive forces to drive the p3 to adsorb on the bilayer surface, the adsorption of the p3 pentamer on the lipid bilayer with a preferential C-terminal β-strands facing toward the bilayer surface is a net outcome of different competitions between p3 peptides-lipid bilayer and ions-p3-bilayer interactions. More importantly, Ca2+ ions are found to form ionic bridges to associate negatively charged residues of p3 with anionic headgroups of the lipid bilayer, resulting in Aβ–Ca2+–PO4− complexes. Intensive Ca2+ bound to lipid bilayer and Ca2+ ionic bridges may lead to the alternation of Ca2+ hemostasis responsible for neuronal dysfunction and death. This work provides insights into the mutual structure, dynamics, and interactions of both Aβ peptides and lipid bilayer at the atomic level, which expand our understanding of the complex behavior of amyloid-induced membrane disruption. PMID:23493873

  15. Dynamics of protein aggregation and oligomer formation governed by secondary nucleation

    NASA Astrophysics Data System (ADS)

    Michaels, Thomas C. T.; Lazell, Hamish W.; Arosio, Paolo; Knowles, Tuomas P. J.

    2015-08-01

    The formation of aggregates in many protein systems can be significantly accelerated by secondary nucleation, a process where existing assemblies catalyse the nucleation of new species. In particular, secondary nucleation has emerged as a central process controlling the proliferation of many filamentous protein structures, including molecular species related to diseases such as sickle cell anemia and a range of neurodegenerative conditions. Increasing evidence suggests that the physical size of protein filaments plays a key role in determining their potential for deleterious interactions with living cells, with smaller aggregates of misfolded proteins, oligomers, being particularly toxic. It is thus crucial to progress towards an understanding of the factors that control the sizes of protein aggregates. However, the influence of secondary nucleation on the time evolution of aggregate size distributions has been challenging to quantify. This difficulty originates in large part from the fact that secondary nucleation couples the dynamics of species distant in size space. Here, we approach this problem by presenting an analytical treatment of the master equation describing the growth kinetics of linear protein structures proliferating through secondary nucleation and provide closed-form expressions for the temporal evolution of the resulting aggregate size distribution. We show how the availability of analytical solutions for the full filament distribution allows us to identify the key physical parameters that control the sizes of growing protein filaments. Furthermore, we use these results to probe the dynamics of the populations of small oligomeric species as they are formed through secondary nucleation and discuss the implications of our work for understanding the factors that promote or curtail the production of these species with a potentially high deleterious biological activity.

  16. A structural mechanism for dimeric to tetrameric oligomer conversion in Halomonas sp. nucleoside diphosphate kinase

    PubMed Central

    Arai, Shigeki; Yonezawa, Yasushi; Okazaki, Nobuo; Matsumoto, Fumiko; Tamada, Taro; Tokunaga, Hiroko; Ishibashi, Matsujiro; Blaber, Michael; Tokunaga, Masao; Kuroki, Ryota

    2012-01-01

    Nucleoside diphosphate kinase (NDK) is known to form homotetramers or homohexamers. To clarify the oligomer state of NDK from moderately halophilic Halomonas sp. 593 (HaNDK), the oligomeric state of HaNDK was characterized by light scattering followed by X-ray crystallography. The molecular weight of HaNDK is 33,660, and the X-ray crystal structure determination to 2.3 and 2.7 Å resolution showed a dimer form which was confirmed in the different space groups of R3 and C2 with an independent packing arrangement. This is the first structural evidence that HaNDK forms a dimeric assembly. Moreover, the inferred molecular mass of a mutant HaNDK (E134A) indicated 62.1–65.3 kDa, and the oligomerization state was investigated by X-ray crystallography to 2.3 and 2.5 Å resolution with space groups of P21 and C2. The assembly form of the E134A mutant HaNDK was identified as a Type I tetramer as found in Myxococcus NDK. The structural comparison between the wild-type and E134A mutant HaNDKs suggests that the change from dimer to tetramer is due to the removal of negative charge repulsion caused by the E134 in the wild-type HaNDK. The higher ordered association of proteins usually contributes to an increase in thermal stability and substrate affinity. The change in the assembly form by a minimum mutation may be an effective way for NDK to acquire molecular characteristics suited to various circumstances. PMID:22275000

  17. Dynamics of protein aggregation and oligomer formation governed by secondary nucleation

    SciTech Connect

    Michaels, Thomas C. T. Lazell, Hamish W.; Arosio, Paolo; Knowles, Tuomas P. J.

    2015-08-07

    The formation of aggregates in many protein systems can be significantly accelerated by secondary nucleation, a process where existing assemblies catalyse the nucleation of new species. In particular, secondary nucleation has emerged as a central process controlling the proliferation of many filamentous protein structures, including molecular species related to diseases such as sickle cell anemia and a range of neurodegenerative conditions. Increasing evidence suggests that the physical size of protein filaments plays a key role in determining their potential for deleterious interactions with living cells, with smaller aggregates of misfolded proteins, oligomers, being particularly toxic. It is thus crucial to progress towards an understanding of the factors that control the sizes of protein aggregates. However, the influence of secondary nucleation on the time evolution of aggregate size distributions has been challenging to quantify. This difficulty originates in large part from the fact that secondary nucleation couples the dynamics of species distant in size space. Here, we approach this problem by presenting an analytical treatment of the master equation describing the growth kinetics of linear protein structures proliferating through secondary nucleation and provide closed-form expressions for the temporal evolution of the resulting aggregate size distribution. We show how the availability of analytical solutions for the full filament distribution allows us to identify the key physical parameters that control the sizes of growing protein filaments. Furthermore, we use these results to probe the dynamics of the populations of small oligomeric species as they are formed through secondary nucleation and discuss the implications of our work for understanding the factors that promote or curtail the production of these species with a potentially high deleterious biological activity.

  18. Donepezil inhibits the amyloid-beta oligomer-induced microglial activation in vitro and in vivo.

    PubMed

    Kim, Hyo Geun; Moon, Minho; Choi, Jin Gyu; Park, Gunhyuk; Kim, Ae-Jung; Hur, Jinyoung; Lee, Kyung-Tae; Oh, Myung Sook

    2014-01-01

    Recent studies on Alzheimer's disease (AD) have focused on soluble oligomeric forms of amyloid-beta (Aβ oligomer, AβO) that are directly associated with AD-related pathologies, such as cognitive decline, neurodegeneration, and neuroinflammation. Donepezil is a well-known anti-dementia agent that increases acetylcholine levels through inhibition of acetylcholinesterase. However, a growing body of experimental and clinical studies indicates that donepezil may also provide neuroprotective and disease-modifying effects in AD. Additionally, donepezil has recently been demonstrated to have anti-inflammatory effects against lipopolysaccharides and tau pathology. However, it remains unknown whether donepezil has anti-inflammatory effects against AβO in cultured microglial cells and the brain in animals. Further, the effects of donepezil against AβO-mediated neuronal death, astrogliosis, and memory impairment have also not yet been investigated. Thus, in the present study, we examined the anti-inflammatory effect of donepezil against AβO and its neuroinflammatory mechanisms. Donepezil significantly attenuated the release of inflammatory mediators (prostaglandin E2, interleukin-1 beta, tumor necrosis factor-α, and nitric oxide) from microglia. Donepezil also decreased AβO-induced up-regulation of inducible nitric oxide synthase and cyclooxygenase-2 protein and phosphorylation of p38 mitogen-activated protein kinase as well as translocation of nuclear factor-kappa B. We next showed that donepezil suppresses activated microglia-mediated toxicity in primary hippocampal cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. In intrahippocampal AβO-injected mice, donepezil significantly inhibited microgliosis and astrogliosis. Furthermore, behavioral tests revealed that donepezil (2 mg/kg/day, 5 days, p.o.) significantly ameliorated AβO-induced memory impairment. These results suggest that donepezil directly inhibits microglial activation

  19. Soluble Oligomers of the Pore-forming Toxin Cytolysin A from Escherichia coli Are Off-pathway Products of Pore Assembly.

    PubMed

    Roderer, Daniel; Benke, Stephan; Schuler, Benjamin; Glockshuber, Rudi

    2016-03-11

    The α-pore-forming toxin Cytolysin A (ClyA) is responsible for the hemolytic activity of various Escherichia coli and Salmonella enterica strains. Soluble ClyA monomers spontaneously assemble into annular dodecameric pore complexes upon contact with membranes or detergent. At ClyA monomer concentrations above ∼100 nm, the rate-limiting step in detergent- or membrane- induced pore assembly is the unimolecular reaction from the monomer to the assembly-competent protomer, which then oligomerizes rapidly to active pore complexes. In the absence of detergent, ClyA slowly forms soluble oligomers. Here we show that soluble ClyA oligomers cannot form dodecameric pore complexes after the addition of detergent and are hemolytically inactive. In addition, we demonstrate that the natural cysteine pair Cys-87/Cys-285 of ClyA forms a disulfide bond under oxidizing conditions and that both the oxidized and reduced ClyA monomers assemble to active pores via the same pathway in the presence of detergent, in which an unstructured, monomeric intermediate is transiently populated. The results show that the oxidized ClyA monomer assembles to pore complexes about one order of magnitude faster than the reduced monomer because the unstructured intermediate of oxidized ClyA is less stable and dissolves more rapidly than the reduced intermediate. Moreover, we show that oxidized ClyA forms soluble, inactive oligomers in the absence of detergent much faster than the reduced monomer, providing an explanation for several contradictory reports in which oxidized ClyA had been described as inactive. PMID:26757820

  20. Theoretical studies of optics and charge transport in organic conducting oligomers and polymers: Rational design of improved transparent and conducting polymers

    NASA Astrophysics Data System (ADS)

    Hutchison, Geoffrey Rogers

    Theoretical studies on a variety of oligo- and polyheterocycles elucidate their optical and charge transport properties, suggesting new, improved transparent conductive polymers. First-principles calculations provide accurate methodologies for predicting both optical band gaps of neutral and cationic oligomers and intrinsic charge transfer rates. Multidimensional analysis reveals important motifs in chemical tailorability of oligoheterocycle optical and charge transport properties. The results suggest new directions for design of novel materials. Using both finite oligomer and infinite polymer calculations, the optical band gaps in polyheterocycles follow a modified particle-in-a-box formalism, scaling approximately as 1/N (where N is the number of monomer units) in short chains, saturating for long chains. Calculations demonstrate that band structure changes upon heteroatom substitution, (e.g., from polythiophene to polypyrrole) derive from heteroatom electron affinity. Further investigation of chemical variability in substituted oligoheterocycles using multidimensional statistics reveals the interplay between heteroatom and substituent in correlations between structure and redox/optical properties of neutral and cationic species. A linear correlation between band gaps of neutral and cationic species upon oxidation of conjugated oligomers, shows redshifts of optical absorption for most species and blueshifts for small band gap species. Interstrand charge-transport studies focus on two contributors to hopping-style charge transfer rates: internal reorganization energy and the electronic coupling matrix element. Statistical analysis of chemical variability of reorganization energies in oligoheterocycles proves the importance of reorganization energy in determining intrinsic charge transfer rates (e.g., charge mobility in unsubstituted oligothiophenes). Computed bandwidths across several oligothiophene crystal packing motifs show similar electron and hole bandwidths

  1. Protective spin-labeled fluorenes maintain amyloid beta peptide in small oligomers and limit transitions in secondary structure

    SciTech Connect

    Altman, Robin; Ly, Sonny; Hilt, Silvia; Petrlova, Jitka; Maezawa, Izumi; Kálai, Tamás; Hideg, Kálmán; Jin, Lee-Way; Laurence, Ted A.; Voss, John C.

    2015-12-01

    Alzheimer’s disease is characterized by the presence of extracellular plaques comprised of amyloid beta (Aβ) peptides. Soluble oligomers of the Aβ peptide underlie a cascade of neuronal loss and dysfunction associated with Alzheimer's disease. Single particle analyses of Aβ oligomers in solution by fluorescence correlation spectroscopy (FCS) were used to provide real-time descriptions of how spin-labeled fluorenes (SLFs; bi-functional small molecules that block the toxicity of Aβ) prevent and disrupt oligomeric assemblies of Aβ in solution. The FCS results, combined with electron paramagnetic resonance spectroscopy and circular dichroism spectroscopy, demonstrate SLFs can inhibit the growth of Aβ oligomers and disrupt existing oligomers while retaining Aβ in a largely disordered state. Furthermore, while the ability of SLF to block Aβ toxicity correlates with a reduction in oligomer size, our results suggest the conformation of Aβ within the oligomer determines the toxicity of the species. Attenuation of Aβ toxicity, which has been associated primarily with the soluble oligomeric form, can be achieved through redistribution of the peptides into smaller oligomers and arrest of the fractional increase in beta secondary structure.

  2. Protective spin-labeled fluorenes maintain amyloid beta peptide in small oligomers and limit transitions in secondary structure

    DOE PAGESBeta

    Altman, Robin; Ly, Sonny; Hilt, Silvia; Petrlova, Jitka; Maezawa, Izumi; Kálai, Tamás; Hideg, Kálmán; Jin, Lee-Way; Laurence, Ted A.; Voss, John C.

    2015-12-01

    Alzheimer’s disease is characterized by the presence of extracellular plaques comprised of amyloid beta (Aβ) peptides. Soluble oligomers of the Aβ peptide underlie a cascade of neuronal loss and dysfunction associated with Alzheimer's disease. Single particle analyses of Aβ oligomers in solution by fluorescence correlation spectroscopy (FCS) were used to provide real-time descriptions of how spin-labeled fluorenes (SLFs; bi-functional small molecules that block the toxicity of Aβ) prevent and disrupt oligomeric assemblies of Aβ in solution. The FCS results, combined with electron paramagnetic resonance spectroscopy and circular dichroism spectroscopy, demonstrate SLFs can inhibit the growth of Aβ oligomers and disruptmore » existing oligomers while retaining Aβ in a largely disordered state. Furthermore, while the ability of SLF to block Aβ toxicity correlates with a reduction in oligomer size, our results suggest the conformation of Aβ within the oligomer determines the toxicity of the species. Attenuation of Aβ toxicity, which has been associated primarily with the soluble oligomeric form, can be achieved through redistribution of the peptides into smaller oligomers and arrest of the fractional increase in beta secondary structure.« less

  3. A Holographic Road Show.

    ERIC Educational Resources Information Center

    Kirkpatrick, Larry D.; Rugheimer, Mac

    1979-01-01

    Describes the viewing sessions and the holograms of a holographic road show. The traveling exhibits, believed to stimulate interest in physics, include a wide variety of holograms and demonstrate several physical principles. (GA)

  4. Photopumped laser oscillation and charge-injected luminescence from organic semiconductor single crystals of a thiophene/phenylene co-oligomer

    NASA Astrophysics Data System (ADS)

    Ichikawa, Musubu; Nakamura, Kiyoshi; Inoue, Masamitsu; Mishima, Hiromi; Haritani, Takeshi; Hibino, Ryota; Koyama, Toshiki; Taniguchi, Yoshio

    2005-11-01

    We have demonstrated that single crystals of a thiophene/phenylene co-oligomer [α ,ω-bis-biphenyl-4-yl-terthiophene (BP3T)] show interesting photonic aspects: (1) the self-waveguided amplified spontaneous light emissions with a comparable low threshold of 8μJ/cm2 to other optimized organic solid-state laser systems, and (2) the laser oscillation based on the optical self-confinement effect in the crystals. We have also presented electroluminescence from the crystals based on bipolar injection and the crystals' tolerance for intense current driving. These achievements strongly imply that BP3T crystals are a promising candidate for organic laser diodes.

  5. Thiophene-based donor-acceptor co-oligomers by copper-catalyzed 1,3-dipolar cycloaddition.

    PubMed

    Potratz, Stefanie; Mishra, Amaresh; Bäuerle, Peter

    2012-01-01

    Herein we present a three-component one-pot procedure to synthesize co-oligomers of a donor-acceptor-donor type, in which thiophene moieties work as donor and 1,2,3-triazoles as acceptor units. In this respect, terminally ethynylated (oligo)thiophenes were coupled to halogenated (oligo)thiophenes in the presence of sodium azide and a copper catalyst. Optoelectronic properties of various thiophene-1,2,3-triazole co-oligomers were investigated by UV-vis spectroscopy and cyclic voltammetry. Several co-oligomers were electropolymerized to the corresponding conjugated polymers. PMID:23015814

  6. Thiophene-based donor–acceptor co-oligomers by copper-catalyzed 1,3-dipolar cycloaddition

    PubMed Central

    Potratz, Stefanie; Mishra, Amaresh

    2012-01-01

    Summary Herein we present a three-component one-pot procedure to synthesize co-oligomers of a donor–acceptor–donor type, in which thiophene moieties work as donor and 1,2,3-triazoles as acceptor units. In this respect, terminally ethynylated (oligo)thiophenes were coupled to halogenated (oligo)thiophenes in the presence of sodium azide and a copper catalyst. Optoelectronic properties of various thiophene-1,2,3-triazole co-oligomers were investigated by UV–vis spectroscopy and cyclic voltammetry. Several co-oligomers were electropolymerized to the corresponding conjugated polymers. PMID:23015814

  7. Nonenzymatic synthesis of RNA and DNA oligomers on hexitol nucleic acid templates: the importance of the A structure

    NASA Technical Reports Server (NTRS)

    Kozlov, I. A.; Politis, P. K.; Van Aerschot, A.; Busson, R.; Herdewijn, P.; Orgel, L. E.; Bada, J. L. (Principal Investigator); Dolan, M. (Principal Investigator)

    1999-01-01

    Hexitol nucleic acid (HNA) is an analogue of DNA containing the standard nucleoside bases, but with a phosphorylated 1,5-anhydrohexitol backbone. HNA oligomers form duplexes having the nucleic acid A structure with complementary DNA or RNA oligomers. The HNA decacytidylate oligomer is an efficient template for the oligomerization of the 5'-phosphoroimidazolides of guanosine or deoxyguanosine. Comparison of the oligomerization efficiencies on HNA, RNA, and DNA decacytidylate templates under various conditions suggests strongly that only nucleic acid double helices with the A structure support efficient template-directed synthesis when 5'-phosphoroimidazolides of nucleosides are used as substrates.

  8. Impact of Pre-Existing Elastic Matrix on TGF-β1 and HA Oligomer-Induced Regenerative Repair by Rat Aortic Smooth Muscle Cells

    PubMed Central

    Gacchina, Carmen E.; Ramamurthi, Anand

    2010-01-01

    Regenerating elastic matrices lost to disease (e.g. in aneurysms) is vital to re-establishing vascular homeostasis but is challenged by poor elastogenicity of post-neonatal cells. We previously showed exogenous hyaluronan oligomers (HA-o) and TGF-β1 to synergistically enhance tropo and matrix elastin deposition by healthy adult rat aortic SMCs (RASMCs). Towards treating aortic aneurysms (AAs), which exhibit cause- and site-specific heterogeneity in matrix content/structure and contain proteolytically-injured SMCs, we investigated impact of pre-existing elastic matrix degeneration on elastogenic induction of injured RASMCs. Elastin-rich RASMC layers at 21 days of culture, were treated with 0.15 U/ml (PPE15) and 0.75 U/ml (PPE75) of porcine pancreatic elastase to degrade the elastic matrix variably, or left uninjured (control). One set of cultures was harvested at 21d, before and after injury, to quantify viable cell count, matrix elastin loss. Other injured cell layers were cultured to 42d with or without factors (0.2 μg/ml HA oligomers, 1 ng/ml TGF-β1). We showed that (a)ability of cultures to self-repair and regenerate elastic matrices following proteolysis is limited when elastolysis is severe, (b)HA oligomers and TGF-β1 elastogenically stimulate RASMCs in mildly-injured (i.e., PPE15) cultures to restore both elastic matrix amounts and elastic-fiber deposition to levels in healthy cultures, and (c) in severely injured (i.e., PPE75) cultures, the factors stimulate matrix elastin synthesis and crosslinking, though not to control levels. The outcomes underscore need to enhance elastogenic factor doses based on severity of elastin loss. This study will help customize therapies for elastin regeneration within AAs based on cause and location. PMID:20653044

  9. Show What You Know

    ERIC Educational Resources Information Center

    Eccleston, Jeff

    2007-01-01

    Big things come in small packages. This saying came to the mind of the author after he created a simple math review activity for his fourth grade students. Though simple, it has proven to be extremely advantageous in reinforcing math concepts. He uses this activity, which he calls "Show What You Know," often. This activity provides the perfect…

  10. The Ozone Show.

    ERIC Educational Resources Information Center

    Mathieu, Aaron

    2000-01-01

    Uses a talk show activity for a final assessment tool for students to debate about the ozone hole. Students are assessed on five areas: (1) cooperative learning; (2) the written component; (3) content; (4) self-evaluation; and (5) peer evaluation. (SAH)

  11. Honored Teacher Shows Commitment.

    ERIC Educational Resources Information Center

    Ratte, Kathy

    1987-01-01

    Part of the acceptance speech of the 1985 National Council for the Social Studies Teacher of the Year, this article describes the censorship experience of this honored social studies teacher. The incident involved the showing of a videotape version of the feature film entitled "The Seduction of Joe Tynan." (JDH)

  12. Talk Show Science.

    ERIC Educational Resources Information Center

    Moore, Mitzi Ruth

    1992-01-01

    Proposes having students perform skits in which they play the roles of the science concepts they are trying to understand. Provides the dialog for a skit in which hot and cold gas molecules are interviewed on a talk show to study how these properties affect wind, rain, and other weather phenomena. (MDH)

  13. Stage a Water Show

    ERIC Educational Resources Information Center

    Frasier, Debra

    2008-01-01

    In the author's book titled "The Incredible Water Show," the characters from "Miss Alaineus: A Vocabulary Disaster" used an ocean of information to stage an inventive performance about the water cycle. In this article, the author relates how she turned the story into hands-on science teaching for real-life fifth-grade students. The author also…

  14. Showing What They Know

    ERIC Educational Resources Information Center

    Cech, Scott J.

    2008-01-01

    Having students show their skills in three dimensions, known as performance-based assessment, dates back at least to Socrates. Individual schools such as Barrington High School--located just outside of Providence--have been requiring students to actively demonstrate their knowledge for years. The Rhode Island's high school graduating class became…

  15. Amyloid β oligomers induce interleukin-1β production in primary microglia in a cathepsin B- and reactive oxygen species-dependent manner

    SciTech Connect

    Taneo, Jun; Adachi, Takumi; Yoshida, Aiko; Takayasu, Kunio; Takahara, Kazuhiko; Inaba, Kayo

    2015-03-13

    Amyloid β (Aβ) peptide, a causative agent of Alzheimer's disease, forms two types of aggregates: oligomers and fibrils. These aggregates induce inflammatory responses, such as interleukin-1β (IL-1β) production by microglia, which are macrophage-like cells located in the brain. In this study, we examined the effect of the two forms of Aβ aggregates on IL-1β production in mouse primary microglia. We prepared Aβ oligomer and fibril from Aβ (1–42) peptide in vitro. We analyzed the characteristics of these oligomers and fibrils by electrophoresis and atomic force microscopy. Interestingly, Aβ oligomers but not Aβ monomers or fibrils induced robust IL-1β production in the presence of lipopolysaccharide. Moreover, Aβ oligomers induced endo/phagolysosome rupture, which released cathepsin B into the cytoplasm. Aβ oligomer-induced IL-1β production was inhibited not only by the cathepsin B inhibitor CA-074-Me but also by the reactive oxygen species (ROS) inhibitor N-acetylcysteine. Random chemical crosslinking abolished the ability of the oligomers to induce IL-1β. Thus, multimerization and fibrillization causes Aβ oligomers to lose the ability to induce IL-1β. These results indicate that Aβ oligomers, but not fibrils, induce IL-1β production in primary microglia in a cathepsin B- and ROS-dependent manner. - Highlights: • We prepared amyloid β (Aβ) fibrils with minimum contamination of Aβ oligomers. • Primary microglia (MG) produced IL-1β in response to Aβ oligomers, but not fibrils. • Only Aβ oligomers induced leakage of cathepsin B from endo/phagolysosomes. • IL-1β production in response to Aβ oligomers depended on both cathepsin B and ROS. • Crosslinking reduced the ability of the Aβ oligomers to induce IL-1β from MG.

  16. Towards directional assembly of hierarchical structures: aniline oligomers as the model precursors

    NASA Astrophysics Data System (ADS)

    Zhao, Yanchai; Stejskal, Jaroslav; Wang, Jixiao

    2013-03-01

    Hierarchical architectures attract a large number of scientists and engineers because of their unique physicochemical properties compared with bulk materials and their precursors. It is believed that intermolecular interactions play a key role in the formation of these hierarchical architectures. However, the principle of coordination of various intermolecular interactions in the self-assembly process is not clear. Here, an aniline oligomer is used as a model brick to study the formation process of well-defined hierarchical architectures, and the directional growth mechanism is proposed. It is assumed that aniline oligomer molecules are asymmetric, and driven by intermolecular attractive forces to aggregate in various manners. Combined with the interactions between the aniline oligomer and molecules from the medium, three-dimensional assemblies, flower-like and urchin-like microspheres, can be formed. The variability and complexity of morphologies produced in the process was analyzed according to the intermolecular interactions, which includes hydrogen bonding, π-π stacking, hydrophobic interaction, etc. The applicability of these special hierarchical architectures, such as in the preparation of superhydrophobic surfaces, is also discussed.Hierarchical architectures attract a large number of scientists and engineers because of their unique physicochemical properties compared with bulk materials and their precursors. It is believed that intermolecular interactions play a key role in the formation of these hierarchical architectures. However, the principle of coordination of various intermolecular interactions in the self-assembly process is not clear. Here, an aniline oligomer is used as a model brick to study the formation process of well-defined hierarchical architectures, and the directional growth mechanism is proposed. It is assumed that aniline oligomer molecules are asymmetric, and driven by intermolecular attractive forces to aggregate in various manners

  17. Taking in a Show.

    PubMed

    Boden, Timothy W

    2016-01-01

    Many medical practices have cut back on education and staff development expenses, especially those costs associated with conventions and conferences. But there are hard-to-value returns on your investment in these live events--beyond the obvious benefits of acquired knowledge and skills. Major vendors still exhibit their services and wares at many events, and the exhibit hall is a treasure-house of information and resources for the savvy physician or administrator. Make and stick to a purposeful plan to exploit the trade show. You can compare products, gain new insights and ideas, and even negotiate better deals with representatives anxious to realize returns on their exhibition investments. PMID:27249887

  18. The effect of terminal substituents on the electronic properties of rod-shaped [HGaNH]n oligomers.

    PubMed

    Pomogaeva, A V; Timoshkin, A Y

    2016-07-20

    The effect of electron-donating and electron-withdrawing terminal groups on the electronic structure of the rod-shaped X3[HGaNH]nY3 or needle-shaped XGa[HGaNH]nNY oligomers (X, Y = H, CH3, F, CF3; n = 9, 30 and 114) was computationally studied at the B3LYP/SVP level of density functional theory. While the needle-shaped oligomers exhibit moderate variability in the electronic structure upon changing the terminal substituents X and Y, the energy gap of long rod-shaped oligomers varies within 2 eV. For oligomers with n = 114, F3[HGaNH]n(CH3)3 exhibits the largest HOMO-LUMO gap of 2.91 eV, while (CH3)3[HGaNH]nF3 has the smallest gap of 0.94 eV. PMID:27389813

  19. Use of complementary DNA oligomers to probe trp leader transcript secondary structures involved in transcription pausing and termination.

    PubMed Central

    Fisher, R; Yanofsky, C

    1984-01-01

    DNA oligomers were synthesized that are perfectly complementary to different segments of the tryptophan (trp) operon leader transcript. These 15 nucleotide long oligomers were used as probes of the involvement of transcript secondary structures in two processes: transcription pausing at the pause site located near base pair 90 in the leader region, and transcription termination at the attenuator. The 15-mers were complementary to the four segments of the trp leader transcript which have been shown to form the alternative secondary structures that are believed to be responsible for pausing, termination, and antitermination. Oligomers complementary to RNA segments 1 and 3 relieved termination while the 15-mer complementary to RNA segment 1 relieved pausing. 15-mers complementary to segment 2 had no effect on pausing and the oligomer complementary to segment 4 had virtually no effect on termination. PMID:6201827

  20. Montmorillonite-catalysed formation of RNA oligomers: the possible role of catalysis in the origins of life

    PubMed Central

    Ferris, James P

    2006-01-01

    Large deposits of montmorillonite are present on the Earth today and it is believed to have been present at the time of the origin of life and has recently been detected on Mars. It is formed by aqueous weathering of volcanic ash. It catalyses the formation of oligomers of RNA that contain monomer units from 2 to 30–50. Oligomers of this length are formed because this catalyst controls the structure of the oligomers formed and does not generate all possible isomers. Evidence of sequence-, regio- and homochiral selectivity in these oligomers has been obtained. Postulates on the role of selective versus specific catalysts on the origins of life are discussed. An introduction to the origin of life is given with an emphasis on reaction conditions based on the recent data obtained from zircons 4.0–4.5 Ga. PMID:17008218

  1. Not a "reality" show.

    PubMed

    Wrong, Terence; Baumgart, Erica

    2013-01-01

    The authors of the preceding articles raise legitimate questions about patient and staff rights and the unintended consequences of allowing ABC News to film inside teaching hospitals. We explain why we regard their fears as baseless and not supported by what we heard from individuals portrayed in the filming, our decade-long experience making medical documentaries, and the full un-aired context of the scenes shown in the broadcast. The authors don't and can't know what conversations we had, what documents we reviewed, and what protections we put in place in each televised scene. Finally, we hope to correct several misleading examples cited by the authors as well as their offhand mischaracterization of our program as a "reality" show. PMID:23631336

  2. Synthetic approaches to mixed ligand chelators on t-butylphenol-formaldehyde oligomer (PFO) platforms

    PubMed Central

    Young, Jennifer A.; Karmakar, Sukhen

    2012-01-01

    Synthetic approaches to mixed ligand chelators on readily available t-butylphenol-formaldehyde oligomer, PFO, scaffolds were examined. In a promising approach, tris and tetraphenol oligomers were selectively mono or di protected using t-butyldiphenyl silyl chloride. The utility of these protected intermediates to prepare representative mixed PFO chelators, carrying ligands such as hydroxamic acid, 3,2-hydroxypyridinones and others was then demonstrated. The introduction of the ligand tethers onto the phenolic scaffold can be done sequentially under relatively mild conditions that tolerate the presence of other sensitive ligand groups. The differential reactivity of the disilyl derivative 20b, allowed stepwise introduction of two different ligands on the internal phenolic positions. This enabled the introduction of three different ligand groups of choice onto the tetra phenol platform. PMID:23226883

  3. QIAD assay for quantitating a compound’s efficacy in elimination of toxic Aβ oligomers

    PubMed Central

    Brener, Oleksandr; Dunkelmann, Tina; Gremer, Lothar; van Groen, Thomas; Mirecka, Ewa A.; Kadish, Inga; Willuweit, Antje; Kutzsche, Janine; Jürgens, Dagmar; Rudolph, Stephan; Tusche, Markus; Bongen, Patrick; Pietruszka, Jörg; Oesterhelt, Filipp; Langen, Karl-Josef; Demuth, Hans-Ulrich; Janssen, Arnold; Hoyer, Wolfgang; Funke, Susanne A.; Nagel-Steger, Luitgard; Willbold, Dieter

    2015-01-01

    Strong evidence exists for a central role of amyloid β-protein (Aβ) oligomers in the pathogenesis of Alzheimer’s disease. We have developed a fast, reliable and robust in vitro assay, termed QIAD, to quantify the effect of any compound on the Aβ aggregate size distribution. Applying QIAD, we studied the effect of homotaurine, scyllo-inositol, EGCG, the benzofuran derivative KMS88009, ZAβ3W, the D-enantiomeric peptide D3 and its tandem version D3D3 on Aβ aggregation. The predictive power of the assay for in vivo efficacy is demonstrated by comparing the oligomer elimination efficiency of D3 and D3D3 with their treatment effects in animal models of Alzheimer´s disease. PMID:26394756

  4. Light-triggered reversible self-assembly of gold nanoparticle oligomers for tunable SERS.

    PubMed

    Zhang, Lei; Dai, Liwei; Rong, Yun; Liu, Zhenzhong; Tong, Dingyi; Huang, Youju; Chen, Tao

    2015-01-27

    A photoresponsive amphiphilic gold nanoparticle (AuNP) is achieved through the decoration of AuNP with hydrophilic poly(ethylene glycol) (PEG) and hydrophobic photoresponsive polymethacrylate containing spiropyran units (PSPMA). Owing to the photoresponsive property of spiropyran units, the amphiphilic AuNPs can easily achieve the controllable assembly/disassembly behaviors under the trigger by light. Under visible light, spiropyran units provide weak intermolecular interactions between neighbored AuNPs, leading to isolated AuNPs in the solution. While under UV light irradiation, spiropyran units in the polymer brushes transform into merocyanine isomer with conjugated structure and zwitterionic state, promoting the integration of adjacent AuNPs through π-π stacking and electrostatic attractions, further leading to the formation of Au oligomers. The smart reversible AuNP oligomers exhibited switchable plasmonic coupling for tuning surface-enhanced Raman scattering (SERS) activity, which is promising for the application of SERS based sensors and optical imaging. PMID:25540841

  5. Preparation and NMR characterization of glucosamine oligomers bearing an azide function using chitosan.

    PubMed

    Maria Marzaioli, Alberto; Bedini, Emiliano; Lanzetta, Rosa; Perino, Vincenzo; Parrilli, Michelangelo; De Castro, Cristina

    2012-10-01

    In this study, a procedure to produce glucosamine oligomers with the amino functions transformed into azido groups was optimized, and HPLC purification afforded to the isolation of nine different oligosaccharides derivatives, with the reducing end transformed in alditol. These oligomers differed for the degree of polymerization and for the type of alditol at the reducing end. The first group comprehended species from di- to hexasaccharide, with all the amino functions converted into an azido group. The second and the third groups were isolated in minor yields, and were both constituted from tri- and tetrasaccharides; the difference between the two groups regarded exclusively the type of alditol found at the reducing end, which was a glucosaminitol in the first case, or a N-acetylglucosaminitol in the other. Products were fully characterized by 2D NMR spectroscopy. The azido moieties installed on these oligosaccharides can be further exploited in Cu(I) catalyzed azido-alkyne cycloaddition reactions. PMID:22840011

  6. Cholesterol facilitates interactions between α-synuclein oligomers and charge-neutral membranes.

    PubMed

    van Maarschalkerweerd, Andreas; Vetri, Valeria; Vestergaard, Bente

    2015-09-14

    Oligomeric species formed during α-synuclein fibrillation are suggested to be membrane-disrupting agents, and have been associated with cytotoxicity in Parkinson's disease. The majority of studies, however, have revealed that the effect of α-synuclein oligomers is only noticeable on systems composed of anionic lipids, while the more physiologically relevant zwitterionic lipids remain intact. We present experimental evidence for significant morphological changes in zwitterionic membranes containing cholesterol, induced by α-synuclein oligomers. Depending on the lipid composition, model membranes are either unperturbed, disrupt, or undergo dramatic morphological changes and segregate into structurally different components, which we visualize by 2-photon fluorescence microscopy and generalized polarization analysis using the fluorescent probe Laurdan. Our results highlight the crucial role of cholesterol for mediating interactions between physiologically relevant membranes and α-synuclein. PMID:26297828

  7. Fluctuation Methods To Study Protein Aggregation in Live Cells: Concanavalin A Oligomers Formation

    PubMed Central

    Vetri, V.; Ossato, G.; Militello, V.; Digman, M.A.; Leone, M.; Gratton, E.

    2011-01-01

    Prefibrillar oligomers of proteins are suspected to be the primary pathogenic agents in several neurodegenerative diseases. A key approach for elucidating the pathogenic mechanisms is to probe the existence of oligomers directly in living cells. In this work, we were able to monitor the process of aggregation of Concanavalin A in live cells. We used number and brightness analysis, two-color cross number and brightness analysis, and Raster image correlation spectroscopy to obtain the number of molecules, aggregation state, and diffusion coefficient as a function of time and cell location. We observed that binding of Concanavalin A to the membrane and the formation of small aggregates paralleled cell morphology changes, indicating progressive cell compaction and death. Upon protein aggregation, we observed increased membrane water penetration as reported by Laurdan generalized polarization imaging. PMID:21281593

  8. Coplanar switching of polarization in thin films of vinylidene fluoride oligomers

    SciTech Connect

    Sharma, Pankaj Fursina, Alexandra; Poddar, Shashi; Ducharme, Stephen; Gruverman, Alexei

    2014-11-03

    Switching characteristics of vinylidene fluoride oligomer thin films with molecular chains aligned normal to the substrate and exhibiting a preferential in-plane polarization have been investigated using coplanar geometry of inter-digital electrodes via high-resolution piezoresponse force microscopy. It has been shown that in-plane switching proceeds via non-180° rotation of dipoles mediated by non-stochastic nucleation, expansion, and coalescence of domains. As-grown multidomain configuration is found to be strongly pinned aided by charged domain walls, and the electrically induced (in-plane) mono-domain states relax to the as-grown state. The observed coercive field (approximately 0.6 MV/m) is two to three orders of magnitude smaller than that for the oligomer films with out-of-plane polarization. It is suggested that the low steric hindrance to the rotation of molecular dipoles gives rise to the observed low coercive field.

  9. Heat-induced formation of myosin oligomer-soluble filament complex in high-salt solution.

    PubMed

    Shimada, Masato; Takai, Eisuke; Ejima, Daisuke; Arakawa, Tsutomu; Shiraki, Kentaro

    2015-02-01

    Heat-induced aggregation of myosin into an elastic gel plays an important role in the water-holding capacity and texture of meat products. Here, we investigated thermal aggregation of porcine myosin in high-salt solution over a wide temperature range by dynamic light scattering experiments. The myosin samples were readily dissolved in 1.0 M NaCl at 25 °C followed by dilution into various salt concentrations. The diluted solutions consistently contained both myosin monomers and soluble filaments. The filament size decreased with increasing salt concentration and temperature. High temperatures above Tm led to at least partial dissociation of soluble filaments and thermal unfolding, resulting in the formation of soluble oligomers and binding to the persistently present soluble filaments. Such a complex formation between the oligomers and filaments has never been observed. Our results provide new insight into the heat-induced myosin gelation in high-salt solution. PMID:25445683

  10. Sequence-Defined Oligomers from Hydroxyproline Building Blocks for Parallel Synthesis Applications.

    PubMed

    Kanasty, Rosemary L; Vegas, Arturo J; Ceo, Luke M; Maier, Martin; Charisse, Klaus; Nair, Jayaprakash K; Langer, Robert; Anderson, Daniel G

    2016-08-01

    The functionality of natural biopolymers has inspired significant effort to develop sequence-defined synthetic polymers for applications including molecular recognition, self-assembly, and catalysis. Conjugation of synthetic materials to biomacromolecules has played an increasingly important role in drug delivery and biomaterials. We developed a controlled synthesis of novel oligomers from hydroxyproline-based building blocks and conjugated these materials to siRNA. Hydroxyproline-based monomers enable the incorporation of broad structural diversity into defined polymer chains. Using a perfluorocarbon purification handle, we were able to purify diverse oligomers through a single solid-phase extraction method. The efficiency of synthesis was dem