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Sample records for insulin oligomer reaction

  1. Time-dependent insulin oligomer reaction pathway prior to fibril formation: cooling and seeding.

    PubMed

    Sorci, Mirco; Grassucci, Robert A; Hahn, Ingrid; Frank, Joachim; Belfort, Georges

    2009-10-01

    The difficulty in identifying the toxic agents in all amyloid-related diseases is likely due to the complicated kinetics and thermodynamics of the nucleation process and subsequent fibril formation. The slow progression of these diseases suggests that the formation, incorporation, and/or action of toxic agents are possibly rate limiting. Candidate toxic agents include precursors (some at very low concentrations), also called oligomers and protofibrils, and the fibrils. Here, we investigate the kinetic and thermodynamic behavior of human insulin oligomers (imaged by cryo-EM) under fibril-forming conditions (pH 1.6 and 65 degrees C) by probing the reaction pathway to insulin fibril formation using two different types of experiments-cooling and seeding-and confirm the validity of the nucleation model and its effect on fibril growth. The results from both the cooling and seeding studies confirm the existence of a time-changing oligomer reaction process prior to fibril formation that likely involves a rate-limiting nucleation process followed by structural rearrangements of intermediates (into beta-sheet rich entities) to form oligomers that then form fibrils. The latter structural rearrangement step occurs even in the absence of nuclei (i.e., with added heterologous seeds). Nuclei are formed at the fibrillation conditions (pH 1.6 and 65 degrees C) but are also continuously formed during cooling at pH 1.6 and 25 degrees C. Within the time-scale of the experiments, only after increasing the temperature to 65 degrees C are the trapped insulin nuclei and resultant structures able to induce the structural rearrangement step and overcome the energy barrier to form fibrils. This delay in fibrillation and accumulation of nuclei at low temperature (25 degrees C) result in a decrease in the mean length of the fibers when placed at 65 degrees C. Fits of an empirical model to the data provide quantitative measures of the delay in the lag-time during the nucleation process and

  2. Time-dependent insulin oligomer reaction pathway prior to fibril formation: Cooling and seeding

    PubMed Central

    Sorci, Mirco; Grassucci, Robert A.; Hahn, Ingrid; Frank, Joachim; Belfort, Georges

    2009-01-01

    The difficulty in identifying the toxic agents in all amyloid-related diseases is likely due to the complicated kinetics and thermodynamics of the nucleation process and subsequent fibril formation. The slow progression of these diseases suggests that the formation, incorporation and/or action of toxic agents is possibly rate limiting. Candidate toxic agents include precursors (some at very low concentrations), also called oligomers and protofibrils, and the fibrils. Here, we investigate the kinetic and thermodynamic behavior of human insulin oligomers (imaged by cryo-EM) under fibril forming conditions (pH 1.6 and 65°C) by probing the reaction pathway to insulin fibril formation using two different types of experiments – cooling and seeding – and confirm the validity of the nucleation model and its effect on fibril growth. The results from both the cooling and seeding studies confirm the existence of a time-changing oligomer reaction process prior to fibril formation that likely involves a rate-limiting nucleation process followed by structural rearrangements of intermediates (into β-sheet rich entities) to form oligomers that then form fibrils. The latter structural rearrangement step occurs even in the absence of nuclei (i.e. with added heterologous seeds). Nuclei are formed at the fibrillation conditions (pH 1.6 and 65°C) but are also continuously formed during cooling at pH 1.6 and 25°C. Within the time-scale of the experiments, only after increasing the temperature to 65°C are the trapped insulin nuclei and resultant structures able to induce the structural rearrangement step and overcome the energy barrier to form fibrils. This delay in fibrillation and accumulation of nuclei at low temperature (25°C), result in a decrease in the mean length of the fibers when placed at 65°C. Fits of an empirical model to the data provide quantitative measures of the delay in the lag-time during the nucleation process and subsequent reduction in fibril growth rate

  3. Amyloid beta oligomers induce impairment of neuronal insulin receptors.

    PubMed

    Zhao, Wei-Qin; De Felice, Fernanda G; Fernandez, Sara; Chen, Hui; Lambert, Mary P; Quon, Michael J; Krafft, Grant A; Klein, William L

    2008-01-01

    Recent studies have indicated an association between Alzheimer's disease (AD) and central nervous system (CNS) insulin resistance. However, the cellular mechanisms underlying the link between these two pathologies have not been elucidated. Here we show that signal transduction by neuronal insulin receptors (IR) is strikingly sensitive to disruption by soluble Abeta oligomers (also known as ADDLs). ADDLs are known to accumulate in AD brain and have recently been implicated as primary candidates for initiating deterioration of synapse function, composition, and structure. Using mature cultures of hippocampal neurons, a preferred model for studies of synaptic cell biology, we found that ADDLs caused a rapid and substantial loss of neuronal surface IRs specifically on dendrites bound by ADDLs. Removal of dendritic IRs was associated with increased receptor immunoreactivity in the cell body, indicating redistribution of the receptors. The neuronal response to insulin, measured by evoked IR tyrosine autophosphorylation, was greatly inhibited by ADDLs. Inhibition also was seen with added glutamate or potassium-induced depolarization. The effects on IR function were completely blocked by NMDA receptor antagonists, tetrodotoxin, and calcium chelator BAPTA-AM. Downstream from the IR, ADDLs induced a phosphorylation of Akt at serine473, a modification associated with neurodegenerative and insulin resistance diseases. These results identify novel factors that affect neuronal IR signaling and suggest that insulin resistance in AD brain is a response to ADDLs, which disrupt insulin signaling and may cause a brain-specific form of diabetes as part of an overall pathogenic impact on CNS synapses.

  4. Thermal Reaction of Cinnamate Oligomers and Their Effect on the Orientational Stability of Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Hah, Hyundae; Sung, Shi‑Joon; Park, Jung‑Ki

    2006-08-01

    Cinnamate groups are well-known for a dimerization reaction upon exposure to ultraviolet irradiation and a thermal reaction after being heated. In this study, to verify the thermal reaction of the cinnamate group in detail, we investigated the thermal crosslinking of cinnamate oligomers. The thermal reaction of cinnamate oligomers of low molecular weight is induced more readily by thermal energy compared with that of cinnamate polymers. This reaction is attributed to a radical reaction involving the carbon-carbon double bond in the cinnamate group. The orientation of the liquid crystal depended on the length of the spacers in the cinnamate oligomers.

  5. Detecting the Formation and Transformation of Oligomers during Insulin Fibrillation by a Dendrimer Conjugated with Aggregation-Induced Emission Molecule.

    PubMed

    Huang, Qin; Xie, Jing; Liu, Yanpeng; Zhou, Anna; Li, Jianshu

    2017-02-08

    The fibrillation of protein is harmful and impedes the use of protein drugs. It also relates to various debilitating diseases such as Alzheimer's diseases. Thus, investigating the protein fibrillation process is necessary. In this study, poly(amido amine) dendrimers (PAMAM) of generation 3 (G3) and generation 4 (G4) were synthesized and conjugated with 4-aminobiphenyl, an aggregation-induced emission (AIE) moiety, at varied grafting ratios. Among them, one fluorescence probe named G3-biph-3 that was grafted average 3.25 4-aminobiphenyl to the G3, can detect the transformations both from native insulin to oligomers and from oligomers to fibrils. The size difference of native insulin, oligomers, and fibrils was proposed to be the main factor leading to the detection of the above transformations. Different molecular weights of sodium polyacrylate (PAAS) were also applied as a model to interact with G3-biph-3 to further reveal the mechanism. The results indicated that PAMAM with a certain generation and grafted with appropriate AIE groups can detect the oligomer formation and transformation during the insulin fibrillation process.

  6. Efficient synthesis of oxygenated terphenyls and other oligomers: sequential arylation reactions through phenol oxidation-rearomatization.

    PubMed

    Dohi, Toshifumi; Kamitanaka, Tohru; Watanabe, Shohei; Hu, Yinjun; Washimi, Naohiko; Kita, Yasuyuki

    2012-10-22

    One by one: starting from simple phenols, a diverse series of oxygenated terphenyl compounds can be prepared in a concise and practical manner using sequential arylation reactions involving phenol oxidation/rearomatization and quinone monoacetal intermediates. Many of the terphenyl products can be used for preparing well-defined oligomers and, furthermore, contain valuable functional groups that can be transformed for further diversification.

  7. Enhancement of β-amyloid oligomer accumulation after intracerebroventricular injection of streptozotocin, which involves central insulin signaling in a transgenic mouse model.

    PubMed

    Lin, Fangju; Jia, Jianping; Qin, Wei

    2014-11-12

    The β-amyloid (Aβ) oligomer rather than fibrillar Aβ has become the important focus of recent studies on the pathogenesis of Alzheimer's disease (AD). Insulin signaling plays important roles in cognitive disease, such as AD. However, in-vivo evidence for the link between central insulin signaling and the Aβ oligomer are lacking, and the mechanisms underlying the effect of central insulin signaling on AD are still elusive. Our team has established the Presenilin-1 Val97Leu mutant transgenic (PS1V97L) AD mouse model with the intraneuronal Aβ oligomer as the potential initiator for other pathologies, but without extracellular amyloid plaque formation. Using this model, we investigated the roles of disturbed central insulin signaling induced by intracerebroventricular injection of streptozotocin (STZ) in the progression of AD. We observed that PS1V97L mice after intracerebroventricular injection of STZ showed increased Aβ oligomer accumulation and aggravated spatial learning and memory deficit in the absence of diabetes symptoms. Furthermore, STZ administration inhibited the activation of the insulin receptor and enhanced the activation of c-Jun NH2-terminal kinase, which was accompanied by increased production of carboxy-terminal fragments from the amyloid precursor protein, in the brain of PS1V97L mice. Overall, our study provided in-vivo evidence for a role of central insulin signaling in AD progression.

  8. Multidimensional Self-Assembled Structures of Alkylated Cellulose Oligomers Synthesized via in Vitro Enzymatic Reactions.

    PubMed

    Yataka, Yusuke; Sawada, Toshiki; Serizawa, Takeshi

    2016-10-04

    The self-assembly of biomolecules into highly ordered nano-to-macroscale structures is essential in the construction of biological tissues and organs. A variety of biomolecular assemblies composed of nucleic acids, peptides, and lipids have been used as molecular building units for self-assembled materials. However, crystalline polysaccharides have rarely been utilized in self-assembled materials. In this study, we describe multidimensional self-assembled structures of alkylated cellulose oligomers synthesized via in vitro enzymatic reactions. We found that the alkyl chain length drastically affected the assembled morphologies and allomorphs of cellulose moieties. The modulation of the intermolecular interactions of cellulose oligomers by alkyl substituents was highly effective at controlling their assembly into multidimensional structures. This study proposes a new potential of crystalline oligosaccharides for structural components of molecular assemblies with controlled morphologies and crystal structures.

  9. Nano- and Microgels Through Addition Reactions of Functional Oligomers and Polymers

    NASA Astrophysics Data System (ADS)

    Albrecht, Krystyna; Moeller, Martin; Groll, Juergen

    Nano- and Microgels are predominantly prepared using radical polymerization techniques. This chapter reviews alternative approaches to microgel preparation based on addition reactions of functional oligomers and polymers. This allows preparation of microgels under physiological conditions and in the presence of biologically active molecules without affecting their function. This method is therefore predominantly used to synthesize microgels for biomedical applications. Different crosslinking chemistries that have been used in this context are presented and discussed with regard to reaction conditions and stability of the reaction product. Microgels that have been prepared by these techniques are divided into two groups. Natural polymers used for the preparation of microgels are described first, followed by artificial prepolymers that are suitable for the preparation of microgels. The different preparation methods as well as the resulting microgels and their properties are presented and discussed.

  10. Preparation of 13C/15N-labeled oligomers using the polymerase chain reaction

    DOEpatents

    Chen, Xian; Gupta, Goutam; Bradbury, E. Morton

    2001-01-01

    Preparation of .sup.13 C/.sup.15 N-labeled DNA oligomers using the polymerase chain reaction (PCR). A PCR based method for uniform (.sup.13 C/.sup.15 N)-labeling of DNA duplexes is described. Multiple copies of a blunt-ended duplex are cloned into a plasmid, each copy containing the sequence of interest and restriction Hinc II sequences at both the 5' and 3' ends. PCR using bi-directional primers and uniformly .sup.13 C/.sup.15 N-labeled dNTP precursors generates labeled DNA duplexes containing multiple copies of the sequence of interest. Twenty-four cycles of PCR, followed by restriction and purification, gave the uniformly .sup.13 C/.sup.15 N-labeled duplex sequence with a 30% yield. Such labeled duplexes find significant applications in multinuclear magnetic resonance spectroscopy.

  11. Oligomer Formation Reactions of Criegee Intermediates in the Ozonolysis of Small Unsaturated Hydrocarbons

    NASA Astrophysics Data System (ADS)

    Sakamoto, Y.; Inomata, S.; Hirokawa, J.

    2013-12-01

    hydroperoxides of low volatility formed in the gas phase are partitioned into the particle phase to contribute to the SOA formation. Here, we propose a new oligomer formation mechanism including sequential addition of Criegee intermediates to hydroperoxides. REFERENCE: (1)Kroll, J. H.; Seinfeld, J. H. Chemistry of Secondary Organic Aerosol: Formation and Evolution of Low-Volatility Organics in the Atmosphere. Atmos. Environ. 2008, 42, 3593-3624. (2)Sadezky, A.; Chaimbault, P.; Mellouki, A.; Roempp, A.; Winterhalter, R.; Le Bras, G.; Moortgat, G. K. Formation of Secondary Organic Aerosol and Oligomers from the Ozonolysis of Enol Ethers. Atmos. Chem. Phys. 2006, 6, 5009-5024. (3)Sadezky, A.; Winterhalter, R.; Kanawati, B.; Roempp, A.; Spengler, B.; Mellouki, A.; Le Bras, G.; Chaimbault, P.; Moortgat, G. K. Oligomer Formation during Gas-Phase Ozonolysis of Small Alkenes and Enol Ethers: New Evidence for the Central Role of the Criegee Intermediate as Oligomer Chain Unit. Atmos. Chem. Phys. 2008, 8, 2667-2699. (4)Klotz, B.; Barnes, I.; Imamura, T. Product Study of the Gas-Phase Reactions of O3, OH and NO3 Radicals with Methyl Vinyl Ether. Phys. Chem. Chem. Phys. 2004, 6, 1725-1734.

  12. Phenylenevinylene oligomers by Mizoroki-Heck cross coupling reaction. Structural and optoelectronic characterization

    NASA Astrophysics Data System (ADS)

    Estrada, Sandra E.; Ochoa-Puentes, Cristian; Sierra, Cesar A.

    2017-04-01

    In order to study the effect of the molecular structure on the optical properties of totally trans-trans phenylenevinylene oligomers (OPVs), sixteen 1,4-distyrylbenzene derivatives (1a-i and 2a-g) functionalized with different electron-donating (ED) and electron-withdrawing (EW) groups were synthesized by the Mizoroki-Heck cross coupling reaction in moderate to good yields (40-95%). The implemented methodology, with a small modification previously reported by our group, allows obtaining the desired vinyl configuration as well as one novel OPV compound (1h). After structural characterization by several techniques (e.g. FTIR, 1H, 13C and Solid-State NMR), particular emphasis was placed upon the investigation of their optical properties by UV-vis and fluorescence spectroscopies. The results showed that, with only one exception, the ED and EW groups at the ends of OPV systems lead to a bathochromic shift. This effect is intensified with the introduction of methoxy groups on the central ring. Consistent with these, the HOMO-LUMO gaps (ΔE) decreases as the strength of ED and EW substituents increases. The ED and EW substituents also lead to a decrease in the Φf values. This contribution in the area of organic electronics can be used as a reference to better select the most appropriate technological application for each OPV and this can be extrapolated to their respective structurally analogous segmented polymer.

  13. Oligomers formed through in-cloud methylglyoxal reactions: Chemical composition, properties, and mechanisms investigated by ultra-high resolution FT-ICR mass spectrometry

    NASA Astrophysics Data System (ADS)

    Altieri, K. E.; Seitzinger, S. P.; Carlton, A. G.; Turpin, B. J.; Klein, G. C.; Marshall, A. G.

    Secondary organic aerosol (SOA) is a substantial component of total atmospheric organic particulate matter, but little is known about the composition of SOA formed through cloud processing. We conducted aqueous phase photo-oxidation experiments of methylglyoxal and hydroxyl radical to simulate cloud processing. In addition to predicted organic acid monomers, oligomer formation from methylglyoxal-hydroxyl radical reactions was detected by electrospray ionization mass spectrometry (ESI-MS). The chemical composition of the oligomers and the mechanism of their formation were investigated by ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and LCQ DUO ion trap mass spectrometry (ESI-MS-MS). Reaction products included 415 compounds detected in the mass range 245-800 Da and the elemental composition of all 415 compounds were determined by ultra-high resolution FT-ICR MS. The ratio of total organic molecular weight per organic carbon weight (OM:OC) of the oligomers (1.0-2.5) was lower than the OM:OC of the organic acid monomers (2.3-3.8) formed, suggesting that the oligomers are less hygroscopic than the organic acid monomers formed from methylglyoxal-hydroxyl radical reaction. The OM:OC of the oligomers (average=2.0) is consistent with that of aged atmospheric aerosols and atmospheric humic-like substances (HULIS). A mechanism is proposed in which the organic acid monomers formed through hydroxyl radical reactions oligomerize through esterification. The mechanism is supported by the existence of series of oligomers identified by elemental composition from FT-ICR MS and ion fragmentation patterns from ESI-MS-MS. Each oligomer series starts with an organic acid monomer formed from hydroxyl radical oxidation, and increases in molecular weight and total oxygen content through esterification with a hydroxy acid (C 3H 6O 3) resulting in multiple additions of 72.02113 Da (C 3H 4O 2) to the parent organic acid monomer. Methylglyoxal is

  14. Nonenzymatic template-directed reactions on altritol oligomers, preorganized analogues of oligonucleotides

    NASA Technical Reports Server (NTRS)

    Kozlov, I. A.; Zielinski, M.; Allart, B.; Kerremans, L.; Van Aerschot, A.; Busson, R.; Herdewijn, P.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    2000-01-01

    Altritol nucleic acids (ANAs) are RNA analogues with a phosphorylated D-altritol backbone. The nucleobase is attached at the 2-(S)-position of the carbohydrate moiety. We report that ANA oligomers are superior to the corresponding DNA, RNA, and HNA (hexitol nucleic acid) in supporting efficient nonenzymatic template-directed synthesis of complementary RNAs from nucleoside-5'-phosphoro-2-methyl imidazolides. Activated ANA and HNA monomers do not oligomerize efficiently on DNA, RNA, HNA, or ANA templates.

  15. Monitoring Time-Dependent Formation of Oligomers and Brown Carbon in Reactions of Glycolaldehyde, Methylglyoxal, and Amines

    NASA Astrophysics Data System (ADS)

    Espelien, B.; Galloway, M. M.; De Haan, D. O.

    2012-12-01

    Authors: Brenna Espelien, Melissa Galloway, and David De Haan The brown carbon components of atmospheric aerosol exhibit strong UV absorbance with a featureless 'tail' that extends into the visible range. Recent work has shown that brown carbon (or HULIS) is formed at least in part by aqueous-phase chemical reactions in the atmosphere. Reactions between aldehydes (such as glycolaldehyde and methylglyoxal) and amines create brown products that have similar light-absorbing spectra as HULIS extracted from atmospheric aerosol. However, the structures of these products have not been well-characterized. Bulk-phase reactions were monitored using LCMS and UV-Vis spectroscopy over a period of 2-3 weeks to see what products formed, whether oligomerization is occurring, and how this correlates with the development of absorbance peaks in the visible range. UV-Vis data shows that these reactions generally take several days to reach maximum absorbance in the visible range. For the glycolaldehyde/glycine reaction, the appearance of a strong absorber at about 400 nm correlated with the appearance of high-mass products at m/z 227, 363, 393, and 431. Additional reactions between aldehydes and amines that quickly produce brown products are being studied. We suggest that imine oligomers are major products of these reactions.

  16. β-Amyloid Oligomers Induce Phosphorylation of Tau and Inactivation of Insulin Receptor Substrate via c-Jun N-Terminal Kinase Signaling: Suppression by Omega-3 Fatty Acids and Curcumin

    PubMed Central

    Ma, Qiu-Lan; Yang, Fusheng; Rosario, Emily R.; Ubeda, Oliver J.; Beech, Walter; Gant, Dana J.; Chen, Ping Ping; Hudspeth, Beverly; Chen, Cory; Zhao, Yongle; Vinters, Harry V.; Frautschy, Sally A.

    2009-01-01

    Both insulin resistance (type II diabetes) and β-amyloid (Aβ) oligomers are implicated in Alzheimer's disease (AD). Here, we investigate the role of Aβ oligomer-induced c-Jun N-terminal kinase (JNK) activation leading to phosphorylation and degradation of the adaptor protein insulin receptor substrate-1 (IRS-1). IRS-1 couples insulin and other trophic factor receptors to downstream kinases and neuroprotective signaling. Increased phospho-IRS-1 is found in AD brain and insulin-resistant tissues from diabetics. Here, we report Aβ oligomers significantly increased active JNK and phosphorylation of IRS-1 (Ser616) and tau (Ser422) in cultured hippocampal neurons, whereas JNK inhibition blocked these responses. The omega-3 fatty acid docosahexaenoic acid (DHA) similarly inhibited JNK and the phosphorylation of IRS-1 and tau in cultured hippocampal neurons. Feeding 3xTg-AD transgenic mice a diet high in saturated and omega-6 fat increased active JNK and phosphorylated IRS-1 and tau. Treatment of the 3xTg-AD mice on high-fat diet with fish oil or curcumin or a combination of both for 4 months reduced phosphorylated JNK, IRS-1, and tau and prevented the degradation of total IRS-1. This was accompanied by improvement in Y-maze performance. Mice fed with fish oil and curcumin for 1 month had more significant effects on Y-maze, and the combination showed more significant inhibition of JNK, IRS-1, and tau phosphorylation. These data indicate JNK mediates Aβ oligomer inactivation of IRS-1 and phospho-tau pathology and that dietary treatment with fish oil/DHA, curcumin, or a combination of both has the potential to improve insulin/trophic signaling and cognitive deficits in AD. PMID:19605645

  17. Damage to fuel cell membranes. Reaction of HO* with an oligomer of poly(sodium styrene sulfonate) and subsequent reaction with O(2).

    PubMed

    Dockheer, Sindy M; Gubler, Lorenz; Bounds, Patricia L; Domazou, Anastasia S; Scherer, Günther G; Wokaun, Alexander; Koppenol, Willem H

    2010-10-07

    An understanding of the reactivity of oligomeric compounds that model fuel cell membrane materials under oxidative-stress conditions that mimic the fuel cell operating environment can identify material weaknesses and yield valuable insights into how a polymer might be modified to improve oxidative stability. The reaction of HO˙ radicals with a polymer electrolyte fuel cell membrane represents an initiation step for irreversible membrane oxidation. By means of pulse radiolysis, we measured k = (9.5 ± 0.6) × 10(9) M(-1) s(-1) for the reaction of HO˙ with poly(sodium styrene sulfonate), PSSS, with an average molecular weight of 1100 Da (PSSS-1100) in aqueous solution at room temperature. In the initial reaction of HO˙ with the oligomer (90 ± 10)% react by addition to form hydroxycyclohexadienyl radicals, while the remaining abstract a hydrogen to yield benzyl radicals. The hydroxycyclohexadienyl radicals react reversibly with dioxygen to form the corresponding peroxyl radicals; the second-order rate constant for the forward reaction is k(f) = (3.0 ± 0.5) × 10(7) M(-1) s(-1), and for the back reaction, we derive an upper limit for the rate constant k(r) of (4.5 ± 0.9) × 10(3) s(-1). These data place a lower bound on the equilibrium constant K of (7 ± 2) × 10(3) M(-1) at 295 K, which allows us to calculate a lower limit of the Gibbs energy for the reaction, (-21.7 ± 0.8) kJ mol(-1). At pH 1, the hydroxycyclohexadienyl radicals decay with an overall first-order rate constant k of (6 ± 1) × 10(3) s(-1) to yield benzyl radicals. The second-order rate constant for reaction of dioxygen with benzyl radicals of PSSS-1100 is k = (2-5) × 10(8) M(-1) s(-1). We discuss hydrogen abstraction from PSSS-1100 in terms of the bond dissociation energy, and relate these to relevant electrode potentials. We propose a reaction mechanism for the decay of hydroxycyclohexadienyl radicals and subsequent reaction steps.

  18. Monofunctional hyperbranched ethylene oligomers.

    PubMed

    Wiedemann, Thomas; Voit, Gregor; Tchernook, Alexandra; Roesle, Philipp; Göttker-Schnetmann, Inigo; Mecking, Stefan

    2014-02-05

    The neutral κ(2)N,O-salicylaldiminato Ni(II) complexes [κ(2)N,O-{(2,6-(3',5'-R2C6H3)2C6H3-N═C(H)-(3,5-I2-2-O-C6H2)}]NiCH3(pyridine)] (1a-pyr, R = Me; 1b-pyr, R = Et; 1c-pyr, R = iPr) convert ethylene to hyperbranched low-molecular-weight oligomers (Mn ca. 1000 g mol(-1)) with high productivities. While all three catalysts are capable of generating hyperbranched structures, branching densities decrease significantly with the nature of the remote substituent along Me > Et > iPr and oligomer molecular weights increase. Consequently, only 1a-pyr forms hyperbranched structures over a wide range of reaction conditions (ethylene pressure 5-30 atm and 20-70 °C). An in situ catalyst system achieves similar activities and identical highly branched oligomer microstructures, eliminating the bottleneck given by the preparation and isolation of Ni-Me catalyst precursor species. Selective introduction of one primary carboxylic acid ester functional group per highly branched oligoethylene molecule was achieved by isomerizing ethoxycarbonylation and alternatively cross metathesis with ethyl acrylate followed by hydrogenation. The latter approach results in complete functionalization and no essential loss of branched oligomer material and molecular weight, as the reacting double bonds are close to a chain end. Reduction yielded a monoalcohol-functionalized oligomer. Introduction of one reactive epoxide group per branched oligomer occurs completely and selectively under mild conditions. All reaction steps involved in oligomerization and monofunctionalization are efficient and readily scalable.

  19. Direct immobilization of DNA oligomers onto the amine-functionalized glass surface for DNA microarray fabrication through the activation-free reaction of oxanine

    PubMed Central

    Pack, Seung Pil; Kamisetty, Nagendra Kumar; Nonogawa, Mitsuru; Devarayapalli, Kamakshaiah Charyulu; Ohtani, Kairi; Yamada, Kazunari; Yoshida, Yasuko; Kodaki, Tsutomu; Makino, Keisuke

    2007-01-01

    Oxanine having an O-acylisourea structure was explored to see if its reactivity with amino group is useful in DNA microarray fabrication. By the chemical synthesis, a nucleotide unit of oxanine (Oxa-N) was incorporated into the 5′-end of probe DNA with or without the -(CH2)n- spacers (n = 3 and 12) and found to immobilize the probe DNA covalently onto the NH2-functionalized glass slide by one-pot reaction, producing the high efficiency of the target hybridization. The methylene spacer, particularly the longer one, generated higher efficiency of the target recognition although there was little effect on the amount of the immobilized DNA oligomers. The post-spotting treatment was also carried out under the mild conditions (at 25 or 42°C) and the efficiencies of the immobilization and the target recognition were evaluated similarly, and analogous trends were obtained. It has also been determined under the mild conditions that the humidity and time of the post-spotting treatment, pH of the spotting solution and the synergistic effects with UV-irradiation largely contribute to the desired immobilization and resulting target recognition. Immobilization of DNA oligomer by use of Oxa-N on the NH2-functionalized surface without any activation step would be employed as one of the advanced methods for generating DNA-conjugated solid surface. PMID:17715142

  20. Insulin

    MedlinePlus

    ... container that can be closed like a laundry detergent bottle. Check the expiration date on the insulin ... in a hard container like an empty laundry detergent bottle or a metal coffee can. Make sure ...

  1. Clickable Nucleic Acids: Sequence-Controlled Periodic Copolymer/Oligomer Synthesis by Orthogonal Thiol-X Reactions.

    PubMed

    Xi, Weixian; Pattanayak, Sankha; Wang, Chen; Fairbanks, Benjamin; Gong, Tao; Wagner, Justine; Kloxin, Christopher J; Bowman, Christopher N

    2015-11-23

    Synthetic polymer approaches generally lack the ability to control the primary sequence, with sequence control referred to as the holy grail. Two click chemistry reactions were now combined to form nucleobase-containing sequence-controlled polymers in simple polymerization reactions. Two distinct approaches are used to form these click nucleic acid (CNA) polymers. These approaches employ thiol-ene and thiol-Michael reactions to form homopolymers of a single nucleobase (e.g., poly(A)n ) or homopolymers of specific repeating nucleobase sequences (e.g., poly(ATC)n). Furthermore, the incorporation of monofunctional thiol-terminated polymers into the polymerization system enables the preparation of multiblock copolymers in a single reaction vessel; the length of the diblock copolymer can be tuned by the stoichiometric ratio and/or the monomer functionality. These polymers are also used for organogel formation where complementary CNA-based polymers form reversible crosslinks.

  2. Large-Scale Refolding and Enzyme Reaction of Human Preproinsulin for Production of Human Insulin.

    PubMed

    Kim, Chang-Kyu; Lee, Seung-Bae; Son, Young-Jin

    2015-10-01

    Human insulin is composed of 21 amino acids of an A-chain and 30 amino acids of a B-chain. This is the protein hormone that has the role of blood sugar control. When the recombinant human proinsulin is expressed in Escherichia coli, a serious problem is the formation of an inclusion body. Therefore, the inclusion body must be denatured and refolded under chaotropic agents and suitable reductants. In this study, H27R-proinsulin was refolded from the denatured form with β-mercaptoethanol and urea. The refolding reaction was completed after 15 h at 15°C, whereas the reaction at 25°C was faster than that at 15°C. The refolding yield at 15°C was 17% higher than that at 25°C. The refolding reaction could be carried out at a high protein concentration (2 g/l) using direct refolding without sulfonation. The most economical and optimal refolding condition for human preproinsulin was 1.5 g/l protein, 10 mM glycine buffer containing 0.6 M urea, pH 10.6, and 0.3 mM β-mercaptoethanol at 15°C for 16 h. The maximum refolding yield was 74.8% at 15°C with 1.5 g/l protein. Moreover, the refolded preproinsulin could be converted into normal mature insulin with two enzymes. The average amount of human insulin was 138.2 g from 200 L of fermentation broth after enzyme reaction with H27R-proinsulin. The direct refolding process for H27R-proinsulin was successfully set up without sulfonation. The step yields for refolding and enzyme reaction were comparatively high. Therefore, our refolding process for production of recombinant insulin may be beneficial to the large-scale production of other biologically active proteins.

  3. Patient reactions to long-term outpatient treatment with continuous subcutaneous insulin infusion.

    PubMed Central

    Pickup, J C; Keen, H; Viberti, G C; Bilous, R W

    1981-01-01

    Fourteen of the first 15 insulin-dependent diabetics to be treated in our unit by three weeks or more of outpatient continuous subcutaneous insulin infusion with a portable syringe pump completed a questionnaire about their reactions to the system. Motivation was more important to a favourable response than occupation or intelligence. Most patients thought that diabetic control was better with the pump than conventional injection treatment and several felt subjectively better. Features such as the greater flexibility of diet and insulin delivery rates during continuous subcutaneous infusion were appreciated. The most consistent adverse criticism was about the size of the device used, nearly all patients thinking that smaller and lighter infusion systems should be developed. Psychological reactions to the infusion and difficulties with interpersonal relationships were identified; these must be clearly appreciated and discussed with patients and family before and during treatment. Nine of the 14 patients said they would undertake continuous subcutaneous infusion for one year and a further two said they would do so if the infuser was smaller. These results provide guidance on future technological development of continuous subcutaneous insulin infusion and indicate that the major constraint to long-term trials of the present system is the size of the pump. PMID:6783163

  4. Insulin

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The manipulation of organic materials--cells, tissues, and even living organisms--offers many exciting possibilities for the future from organic computers to improved aquaculture. Commercial researchers are using the microgravity environment to produce large near perfect protein crystals Research on insulin has yielded crystals that far surpass the quality of insulin crystals grown on the ground. Using these crystals industry partners are working to develop new and improved treatments for diabetes. Other researchers are exploring the possibility of producing antibiotics using plant cell cultures which could lead to both orbital production and the improvement of ground-based antibiotic production.

  5. 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.

  6. Theoretical Investigations on the Formation and Dehydrogenation Reaction Pathways of H(NH2BH2)nH (n=1-4) Oligomers: Importance of Dihydrogen Interactions (DHI)

    SciTech Connect

    Li, Jun; Kathmann, Shawn M.; Hu, Han-Shi; Schenter, Gregory K.; Autrey, Thomas; Gutowski, Maciej S.

    2010-09-06

    The H(NH2BH2)nH oligomers are possible products from dehydrogenation of ammonia borane (NH3BH3) and ammonium borohydride (NH4BH4), which belong to a class of boron-nitrogen-hydrogen (BNHx) compounds that are promising materials for chemical hydrogen storage. Understanding the kinetics and reaction pathways of formation of these oligomers and their further dehydrogenation is essential for developing BNHx-based hydrogen storage materials. We have performed computational modeling using density functional theory (DFT), ab initio wavefunction theory, and Car-Parrinello molecular dynamics (CPMD) simulations on the energetics and formation pathways for the H(NH2BH2)nH (n=1-4) oligomers, polyaminoborane (PAB), from NH3BH3 monomers and the subsequent dehydrogenation steps to form polyiminoborane (PIB). Through transition state searches and evaluation of the intrinsic reaction coordinates, we have investigated the B-N bond cleavage, the reactions of NH3BH3 molecule with intermediates, dihydrogen release through intra- and intermolecular hydrogen transfer, dehydrocoupling/cyclization of the oligomers, and the dimerization of NH3BH3 molecules. We discovered the formation mechanism of H(NH2BH2)n+1H oligomers through reactions of the H(NH2BH2)nH oligomers first with BH3 followed by reactions with NH3 and the release of H2, where the BH3 and NH3 intermediates are formed through dissociation of NH3BH3. We also found that the dimerization of the NH3BH3 molecules to form c-(NH2BH2)2 is slightly exothermic, with an unexpected transition state that leads to the simultaneous release of two H2 molecules. The dehydrogenations of the oligomers are also exothermic, typically by less than 10 kcal/(mol of H2), with the largest exothermicity for n=3. The transition state search shows that the one-step direct dehydrocoupling cyclization of the oligomers is not a favored pathway because of high activation barriers. The dihydrogen bonding, in which protic (HN) hydrogens interact with hydridic

  7. Oligomer formation of the bacterial second messenger c-di-GMP: reaction rates and equilibrium constants indicate a monomeric state at physiological concentrations.

    PubMed

    Gentner, Martin; Allan, Martin G; Zaehringer, Franziska; Schirmer, Tilman; Grzesiek, Stephan

    2012-01-18

    Cyclic diguanosine-monophosphate (c-di-GMP) is a bacterial signaling molecule that triggers a switch from motile to sessile bacterial lifestyles. This mechanism is of considerable pharmaceutical interest, since it is related to bacterial virulence, biofilm formation, and persistence of infection. Previously, c-di-GMP has been reported to display a rich polymorphism of various oligomeric forms at millimolar concentrations, which differ in base stacking and G-quartet interactions. Here, we have analyzed the equilibrium and exchange kinetics between these various forms by NMR spectroscopy. We find that the association of the monomer into a dimeric form is in fast exchange (oligomers are formed in the presence of cations. These are presumably tetramers and octamers, with octamers dominating above about 0.5 mM. Thus, at the low micromolar concentrations of the cellular environment and in the absence of additional compounds that stabilize oligomers, c-di-GMP should be predominantly monomeric. This finding has important implications for the understanding of c-di-GMP recognition by protein receptors. In contrast to the monomer/dimer exchange, formation and dissociation of higher oligomers occurs on a time scale of several hours to days. The time course can be described quantitatively by a simple kinetic model where tetramers are intermediates of octamer formation. The extremely slow oligomer dissociation may generate severe artifacts in biological experiments when c-di-GMP is diluted from concentrated stock solution. We present a simple method to quantify c-di-GMP monomers and oligomers from UV spectra and a procedure to dissolve the unwanted oligomers by an annealing step.

  8. Control the kinetics and pathway of insulin fibril formation

    NASA Astrophysics Data System (ADS)

    Zheng, Zhongli; Jing, Benxin; Zhu, Y. Elaine

    2012-02-01

    Protein fibrils have been proposed as possible toxic agents for many amyloid related diseases, such as Alzheimer's disease, however the reaction pathway toward the amyloid fibrillation remain inadequately understood. In this work, we examine the conformational transition of human insulin as the model amyloid protein by single-molecule fluorescence spectroscopy and imaging. By controlling the pH cycling, insulin monomer and oligomers are indentified at given pH variation condition. Furthermore, low frequency ac-electric fields are employed to control the insulin aggregation from its monomers in a microchannel. It is observed that lag time to induce insulin fibrillation can be significantly shortened, in compassion to the commonly used cooling and seeding methods, and exhibits a strong dependence on applied ac-field strength. Additionally, the structure of insulin aggregates under ac-electric fields is observed to be drastically different from that under the temperature control.

  9. Insulin allergy.

    PubMed

    Ghazavi, Mohammad K; Johnston, Graham A

    2011-01-01

    Insulin reactions occur rarely but are of tremendous clinical importance. The first was reported in 1922 as a callus reaction at the injection site of insufficiently purified bovine insulin. Porcine insulin was subsequently found to be less allergenic than bovine insulin. Increasingly pure insulins have decreased the risk of adverse reactions, and the production of recombinant insulin with the same amino sequence as human insulin saw a large decrease in adverse reactions. Currently, the prevalence of allergic reactions to insulin products appears to be approximately 2%, and less than one-third of these events have been considered related to the insulin itself. Other reactions occur due to the preservatives added to insulin, including zinc, protamine, and meta-cresol. Allergic reactions can be type I or immunoglobulin E-mediated, type III or Arthus, and type IV or delayed-type hypersensitivity reactions. Type I reactions are the most common and can, rarely, cause anaphylaxis. In contrast, type IV reactions can occur after a delay of several days. Investigations include skin prick testing, patch testing, intradermal testing, and occasionally, skin biopsy.

  10. Insulin resistance and necroinflammation drives ductular reaction and epithelial-mesenchymal transition in chronic hepatitis C

    PubMed Central

    Svegliati-Baroni, Gianluca; Faraci, Graziella; Fabris, Luca; Saccomanno, Stefania; Cadamuro, Massimiliano; Pierantonelli, Irene; Trozzi, Luciano; Bugianesi, Elisabetta; Guido, Maria; Strazzabosco, Mario; Benedetti, Antonio; Marchesini, Giulio

    2013-01-01

    Objective To study the mechanism(s) linking insulin resistance (IR) to hepatic fibrosis and the role of the epithelial component in tissue repair and fibrosis in chronic hepatitis C (CHC). Design Prospective observational study. Setting Tertiary care academic centre. Patients 78 consecutive patients with CHC. Main outcome measures IR, calculated by the oral glucose insulin sensitivity during oral glucose tolerance test; necroinflammatory activity and fibrosis, defined according to Ishak’s score; steatosis, graded as 0 (<5% of hepatocytes), 1 (5–33%), 2 (33–66%) and 3 (>66%). To evaluate the role of the epithelial component in tissue repair and fibrosis, the expansion of the ductular reaction (DR) was calculated by keratin-7 (CK7) morphometry. Nuclear expression of Snail, downregulation of E-cadherin and expression of fibroblast specific protein-1 (FSP1) and vimentin by CK7-positive cells were used as markers of epithelial-mesenchymal transition in DR elements. Results IR, the degree of necroinflammation and expansion of the DR (stratified as reactive ductular cells (RDCs), hepatic progenitor cells and intermediate hepatobiliary cells according to morphological criteria) were all associated with the stage of fibrosis. Nuclear Snail expression, E-cadherin downregulation and vimentin upregulation were observed in RDCs. By dual immunofluorescence for CK7 and FSP1, the number of RDCs undergoing epithelial-mesenchymal transition progressively increased together with the necroinflammatory score. By multivariate analysis, total inflammation and insulin resistance were the only factors significantly predicting the presence of advanced fibrosis (Ishak score ≥3) and the expansion of RDCs. Conclusion This study indicates that IR is associated with the degree of necroinflammatory injury in CHC and contributes to hepatic fibrosis by stimulating the expansion of RDCs that express epithelial-mesenchymal transition markers. PMID:20966027

  11. Rapid reaction of superoxide with insulin-tyrosyl radicals to generate a hydroperoxide with subsequent glutathione addition.

    PubMed

    Das, Andrew B; Nauser, Thomas; Koppenol, Willem H; Kettle, Anthony J; Winterbourn, Christine C; Nagy, Péter

    2014-05-01

    Tyrosine (Tyr) residues are major sites of radical generation during protein oxidation. We used insulin as a model to study the kinetics, mechanisms, and products of the reactions of radiation-induced or enzyme-generated protein-tyrosyl radicals with superoxide to demonstrate the feasibility of these reactions under oxidative stress conditions. We found that insulin-tyrosyl radicals combined to form dimers, mostly via the tyrosine at position 14 on the α chain (Tyr14). However, in the presence of superoxide, dimerization was largely outcompeted by the reaction of superoxide with insulin-tyrosyl radicals. Using pulse radiolysis, we measured a second-order rate constant for the latter reaction of (6±1) × 10(8) M(-1) s(-1) at pH 7.3, representing the first measured rate constant for a protein-tyrosyl radical with superoxide. Mass-spectrometry-based product analyses revealed the addition of superoxide to the insulin-Tyr14 radical to form the hydroperoxide. Glutathione efficiently reduced the hydroperoxide to the corresponding monoxide and also subsequently underwent Michael addition to the monoxide to give a diglutathionylated protein adduct. Although much slower, conjugation of the backbone amide group can form a bicyclic Tyr-monoxide derivative, allowing the addition of only one glutathione molecule. These findings suggest that Tyr-hydroperoxides should readily form on proteins under oxidative stress conditions where protein radicals and superoxide are both generated and that these should form addition products with thiol compounds such as glutathione.

  12. Preparation and applications of a variety of fluoroalkyl end-capped oligomer/hydroxyapatite composites.

    PubMed

    Takashima, Hiroki; Iwaki, Ken-Ichi; Furukuwa, Rika; Takishita, Katsuhisa; Sawada, Hideo

    2008-04-15

    A variety of fluoroalkyl end-capped oligomers were applied to the preparation of fluorinated oligomer/hydroxyapatite (HAp) composites (particle size: 38-356 nm), which exhibit a good dispersibility in water and traditional organic solvents. These fluoroalkyl end-capped oligomer/HAp composites were easily prepared by the reactions of disodium hydrogen phosphate and calcium chloride in the presence of self-assembled molecular aggregates formed by fluoroalkyl end-capped oligomers in aqueous solutions. In these fluorinated HAp composites thus obtained, fluoroalkyl end-capped acrylic acid oligomers and 2-methacryloyloxyethanesulfonic acid oligomer/HAp nanocomposites afforded transparent colorless solutions toward water; however, fluoroalkyl end-capped N,N-dimethylacrylamide oligomer and acryloylmorpholine oligomer were found to afford transparent colorless solutions with trace amounts of white-colored HAp precipitants under similar conditions. HAp could be encapsulated more effectively into fluorinated 2-methacryloyloxyethanesulfonic acid oligomeric aggregate cores to afford colloidal stable fluorinated oligomer/HAp composites, compared to that of fluorinated acrylic acid oligomers. These fluorinated oligomer/HAp composites were applied to the surface modification of glass and PVA to exhibit a good oleophobicity imparted by fluorine. HAp formation was newly observed on the modified polyethylene terephthalate film surface treated with fluorinated 2-methacryloyloxyethanesulfonic acid oligomers and acrylic acid oligomer/HAp composites by soaking these films into the simulated body fluid.

  13. 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.

  14. Oligomer formation in the radiation-induced polymerization of styrene

    NASA Astrophysics Data System (ADS)

    Harayma, Hiroshi; Al-Sheikhly, Mohamad; Silverman, Joseph

    2003-12-01

    Analyses of the oligomers formed in radiation-induced polymerization of purified styrene were performed. The principal dimeric products were cis- and trans-diphenyl-cyclobutane with a relatively small amount of 1-phenyltetralin; the trimeric products were the optical isomers of 1-phenyl-4-[1'-phenylethyl-(1')]-tetralin in gamma-ray and 60 MeV proton irradiation. Oligomer formation increased with increasing dose, but more gradually than the linear formation of high polymer with dose. The yield was 0.25-3.1 μmol/J at low doses and decreased to an asymptotic value of 0.15 at higher doses. It appears that oligomers act as chain transfer agents during the polymerization reaction which would account for the observed decrease in molecular weight of the high polymer with increase in dose. Although the thermal and radiation-induced polymerization of styrene have different initiation steps, the oligomers produced by both reactions are similar in composition.

  15. Monte Carlo Simulation of Endlinking Oligomers

    NASA Technical Reports Server (NTRS)

    Hinkley, Jeffrey A.; Young, Jennifer A.

    1998-01-01

    This report describes initial efforts to model the endlinking reaction of phenylethynyl-terminated oligomers. Several different molecular weights were simulated using the Bond Fluctuation Monte Carlo technique on a 20 x 20 x 20 unit lattice with periodic boundary conditions. After a monodisperse "melt" was equilibrated, chain ends were linked whenever they came within the allowed bond distance. Ends remained reactive throughout, so that multiple links were permitted. Even under these very liberal crosslinking assumptions, geometrical factors limited the degree of crosslinking. Average crosslink functionalities were 2.3 to 2.6; surprisingly, they did not depend strongly on the chain length. These results agreed well with the degrees of crosslinking inferred from experiment in a cured phenylethynyl-terminated polyimide oligomer.

  16. 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.

  17. 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.

  18. 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.

  19. Synthesis and Optoelectronic Characterization of Some Star-Shaped Oligomers with Benzene and Triphenylamine Cores

    PubMed Central

    Ivan, Teofilia; Vacareanu, Loredana; Grigoras, Mircea

    2012-01-01

    Six star-shaped oligomers containing triphenylamine (D1–D3) and benzene unit (D4–D6) as cores have been synthesized by Wittig condensation or Heck coupling reaction using aromatic aldehydes and triphenylphosphonium salts or aromatic halogenated compounds with vinyl triphenylamine. All oligomers have well-defined molecular structure and high purity. Characterization of the oligomers was made by FT-IR, 1H-NMR spectroscopy, UV-Vis, and fluorescence spectroscopy. The electrochemical behavior was studied by cyclic voltammetry (CV). The cyclic voltammograms have revealed that oligomers undergo quasireversible or irreversible redox processes. The irreversible process is associated with electrochemical polymerization of oligomers by dimerization of unsubstituted triphenylamine groups. Thermal characterization was accomplished by TGA and DSC methods and evidenced that all oligomers were stable materials until 250°C and have formed stable molecular glasses after first heating scan. PMID:24052859

  20. Synthesis of soybean oil-based thiol oligomers.

    PubMed

    Wu, Jennifer F; Fernando, Shashi; Weerasinghe, Dimuthu; Chen, Zhigang; Webster, Dean C

    2011-08-22

    Industrial grade soybean oil (SBO) and thiols were reacted to generate thiol-functionalized oligomers via a thermal, free radical initiated thiol-ene reaction between the SBO double bond moieties and the thiol functional groups. The effect of the reaction conditions, including thiol concentration, catalyst loading level, reaction time, and atmosphere, on the molecular weight and the conversion to the resultant soy-thiols were examined in a combinatorial high-throughput fashion using parallel synthesis, combinatorial FTIR, and rapid gel permeation chromatography (GPC). High thiol functionality and concentration, high thermal free radical catalyst concentration, long reaction time, and the use of a nitrogen reaction atmosphere were found to favor fast consumption of the SBO, and produced high molecular weight products. The thiol conversion during the reaction was inversely affected by a high thiol concentration, but was favored by a long reaction time and an air reaction atmosphere. These experimental observations were explained by the initial low affinity of the SBO and thiol, and the improved affinity between the generated soy-thiol oligomers and unreacted SBO during the reaction. The synthesized soy-thiol oligomers can be used for renewable thiol-ene UV curable materials and high molecular solids and thiourethane thermal cure materials.

  1. Insulin and Lispro Insulin: What is Common and Different in their Behavior?

    PubMed

    Selivanova, Olga M; Suvorina, Mariya Yu; Surin, Alexey K; Dovidchenko, Nikita V; Galzitskaya, Oxana V

    2017-01-01

    There are different insulin analogues with various pharmacokinetic characteristics, such as, rapid-acting, long-acting, or intermediate-acting analogues. Since insulin tends to form amyloid aggregates, it is of particular interest to measure characteristic times of formation of amyloid aggregates and compare those to action times for insulin and its analogues. For the study we have chosen one of the insulin analogues - insulin Lispro, which is a fast acting insulin analog. It is usually thought of amyloid aggregation as a nucleation-dependent process. We have estimated the size of the primary nucleus to be one monomer and the size of the secondary nucleus to be around zero in both insulin and Lispro insulin aggregation processes. The main structural element of insulin and Lispro insulin amyloid fibrils is a rounded ring oligomer of about 6-7 nm in diameter, about 2-3 nm in height and about 2 nm in diameter of the hole. Fibrils of several μm in length are produced due to interaction of such oligomers. The packing of ring oligomers in fibrils differs because of the difference in their orderliness. Though the initial stages of fibril formation (monomer, oligomer) are similar, the further process depends on the unique sequence of each peptide. Namely the sequence affects the final morphology of mature amyloids. These observations allow us to conclude that formation of fibrils by short peptides occurs via and by means of oligomer ring structures. Such an important issue as the nature of polymorphism of insulin amyloid fibrils has been settled by us. The role of early oligomeric aggregates in such processes as nucleation and aggregation of amyloid fibrils has been examined.

  2. Clinical utility of insulin and insulin analogs

    PubMed Central

    Sanlioglu, Ahter D.; Altunbas, Hasan Ali; Balci, Mustafa Kemal; Griffith, Thomas S.; Sanlioglu, Salih

    2013-01-01

    Diabetes is a pandemic disease characterized by autoimmune, genetic and metabolic abnormalities. While insulin deficiency manifested as hyperglycemia is a common sequel of both Type-1 and Type-2 diabetes (T1DM and T2DM), it does not result from a single genetic defect—rather insulin deficiency results from the functional loss of pancreatic β cells due to multifactorial mechanisms. Since pancreatic β cells of patients with T1DM are destroyed by autoimmune reaction, these patients require daily insulin injections. Insulin resistance followed by β cell dysfunction and β cell loss is the characteristics of T2DM. Therefore, most patients with T2DM will require insulin treatment due to eventual loss of insulin secretion. Despite the evidence of early insulin treatment lowering macrovascular (coronary artery disease, peripheral arterial disease and stroke) and microvascular (diabetic nephropathy, neuropathy and retinopathy) complications of T2DM, controversy exists among physicians on how to initiate and intensify insulin therapy. The slow acting nature of regular human insulin makes its use ineffective in counteracting postprandial hyperglycemia. Instead, recombinant insulin analogs have been generated with a variable degree of specificity and action. Due to the metabolic variability among individuals, optimum blood glucose management is a formidable task to accomplish despite the presence of novel insulin analogs. In this article, we present a recent update on insulin analog structure and function with an overview of the evidence on the various insulin regimens clinically used to treat diabetes. PMID:23584214

  3. 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

  4. Microwave assisted synthesis of bithiophene based donor-acceptor-donor oligomers and their optoelectronic performances

    NASA Astrophysics Data System (ADS)

    Bathula, Chinna; Buruga, Kezia; Lee, Sang Kyu; Khazi, Imtiyaz Ahmed M.; Kang, Youngjong

    2017-07-01

    In this article we present the synthesis of two novel bithiophene based symmetrical π conjugated oligomers with donor-acceptor-donor (D-A-D) structures by microwave assisted PdCl2(dppf) catalyzed Suzuki coupling reaction. These molecules contain electron rich bithiophene as a donor, dithienothiadiazole[3,4-c]pyridine and phthalic anhydride units as acceptors. The shorter reaction time, excellent yields and easy product isolation are the advantages of this method. The photophysical prerequisites for electronic application such as strong and broad optical absorption, thermal stability, and compatible energy levels were determined for synthesized oligomers. Optical band gap for the oligomers is found to be 1.72-1.90 eV. The results demonstrated the novel oligomers to be promising candidates in organic optoelectronic applications.

  5. Production of random DNA oligomers for scalable DNA computing.

    PubMed

    Wang, Sixue S L; Johnson, John J X; Hughes, Bradley S T; Karabay, Dundar A O; Bader, Karson D W; Austin, Allen; Austin, Alan; Habib, Aisha; Hatef, Husnia; Joshi, Megha; Nguyen, Lawrence; Mills, Allen P

    2009-01-01

    While remarkably complex networks of connected DNA molecules can form from a relatively small number of distinct oligomer strands, a large computational space created by DNA reactions would ultimately require the use of many distinct DNA strands. The automatic synthesis of this many distinct strands is economically prohibitive. We present here a new approach to producing distinct DNA oligomers based on the polymerase chain reaction (PCR) amplification of a few random template sequences. As an example, we designed a DNA template sequence consisting of a 50-mer random DNA segment flanked by two 20-mer invariant primer sequences. Amplification of a dilute sample containing about 30 different template molecules allows us to obtain around 10(11) copies of these molecules and their complements. We demonstrate the use of these amplicons to implement some of the vector operations that will be required in a DNA implementation of an analog neural network.

  6. Changes of adiponectin oligomer composition by moderate weight reduction.

    PubMed

    Bobbert, Thomas; Rochlitz, Helmut; Wegewitz, Uta; Akpulat, Suzan; Mai, Knut; Weickert, Martin O; Möhlig, Matthias; Pfeiffer, Andreas F H; Spranger, Joachim

    2005-09-01

    Adiponectin affects lipid metabolism and insulin sensitivity. However, adiponectin circulates in three different oligomers that may also have distinct biological functions. We aimed to analyze the role of these oligomers in obesity and lipid metabolism after weight reduction. A total of 17 obese volunteers (15 women and 2 men) participated in a weight reduction program. Individuals were characterized before and after 6 months of a balanced diet. Adiponectin was determined by enzyme-linked immunosorbent assay, and oligomers were detected by nondenaturating Western blot. BMI decreased (35.1 +/- 1.2 to 32.8 +/- 1.1 kg/m(2), P < 0.001), which was associated with an improved metabolite profile. Total adiponectin increased from 5.3 +/- 0.5 to 6.1 +/- 0.6 microg/ml (P = 0.076). High (HMW) and medium molecular weight (MMW) adiponectin oligomers significantly increased during weight reduction (HMW: 0.37 +/- 0.07 to 0.4 +/- 0.08 microg/ml, P = 0.042; MMW: 2.3 +/- 0.2 to 2.9 +/- 0.3 microg/ml, P = 0.007), while low molecular weight (LMW) did not significantly change. Body weight inversely correlated with HMW (r = -0.695, P = 0.002) and positively with LMW (r = 0.579, P = 0.015). Interestingly, HDL cholesterol and HMW were strongly correlated (r = 0.665, P = 0.007). Indeed, HMW and free fatty acids before weight reduction predicted approximately 60% of HDL changes during intervention. In conclusion, weight reduction results in a relative increase of HMW/MMW adiponectin and a reduction of LMW adiponectin. Total adiponectin and especially HMW adiponectin are related to circulating HDL cholesterol.

  7. Insulin and Insulin Resistance

    PubMed Central

    2005-01-01

    As obesity and diabetes reach epidemic proportions in the developed world, the role of insulin resistance and its consequences are gaining prominence. Understanding the role of insulin in wide-ranging physiological processes and the influences on its synthesis and secretion, alongside its actions from the molecular to the whole body level, has significant implications for much chronic disease seen in Westernised populations today. This review provides an overview of insulin, its history, structure, synthesis, secretion, actions and interactions followed by a discussion of insulin resistance and its associated clinical manifestations. Specific areas of focus include the actions of insulin and manifestations of insulin resistance in specific organs and tissues, physiological, environmental and pharmacological influences on insulin action and insulin resistance as well as clinical syndromes associated with insulin resistance. Clinical and functional measures of insulin resistance are also covered. Despite our incomplete understanding of the complex biological mechanisms of insulin action and insulin resistance, we need to consider the dramatic social changes of the past century with respect to physical activity, diet, work, socialisation and sleep patterns. Rapid globalisation, urbanisation and industrialisation have spawned epidemics of obesity, diabetes and their attendant co-morbidities, as physical inactivity and dietary imbalance unmask latent predisposing genetic traits. PMID:16278749

  8. Isolating Toxic Insulin Amyloid Reactive Species that Lack β-Sheets and Have Wide pH Stability

    PubMed Central

    Heldt, Caryn L.; Kurouski, Dmitry; Sorci, Mirco; Grafeld, Elizabeth; Lednev, Igor K.; Belfort, Georges

    2011-01-01

    Amyloid diseases, including Alzheimer's disease, are characterized by aggregation of normally functioning proteins or peptides into ordered, β-sheet rich fibrils. Most of the theories on amyloid toxicity focus on the nuclei or oligomers in the fibril formation process. The nuclei and oligomers are transient species, making their full characterization difficult. We have isolated toxic protein species that act like an oligomer and may provide the first evidence of a stable reactive species created by disaggregation of amyloid fibrils. This reactive species was isolated by dissolving amyloid fibrils at high pH and it has a mass >100 kDa and a diameter of 48 ± 15 nm. It seeds the formation of fibrils in a dose dependent manner, but using circular dichroism and deep ultraviolet resonance Raman spectroscopy, the reactive species was found to not have a β-sheet rich structure. We hypothesize that the reactive species does not decompose at high pH and maintains its structure in solution. The remaining disaggregated insulin, excluding the toxic reactive species that elongated the fibrils, returned to native structured insulin. This is the first time, to our knowledge, that a stable reactive species of an amyloid reaction has been separated and characterized by disaggregation of amyloid fibrils. PMID:21641325

  9. 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

  10. Using hyperbranched oligomer functionalized glass fillers to reduce shrinkage stress

    PubMed Central

    Ye, Sheng; Azarnoush, Setareh; Smith, Ian R.; Cramer, Neil B.; Stansbury, Jeffrey W.; Bowman, Christopher N

    2012-01-01

    Objective Fillers are widely utilized to enhance the mechanical properties of polymer resins. However, polymerization stress has the potential to increase due to the higher elastic modulus achieved upon filler addition. Here, we demonstrate a hyperbranched oligomer functionalized glass filler UV curable resin composite which is able to reduce the shrinkage stress without sacrificing mechanical properties. Methods A 16-functional alkene-terminated hyperbranched oligomer is synthesized by thiol-acrylate and thiol-yne reactions and the product structure is analyzed by 1H-NMR, mass spectroscopy, and gel permeation chromatography. Surface functionalization of the glass filler is measured by thermogravimetric analysis. Reaction kinetics, mechanical properties and shrinkage stress are studied via Fourier transform infrared spectroscopy, dynamic mechanical analysis and a tensometer, respectively. Results Silica nanoparticles are functionalized with a flexible 16-functional alkene-terminated hyperbranched oligomer which is synthesized by multistage thiol-ene/yne reactions. 93% of the particle surface was covered by this oligomer and an interfacial layer ranging from 0.7 – 4.5 nm thickness is generated. A composite system with these functionalized silica nanoparticles incorporated into the thiol-yne-methacrylate resin demonstrates 30% reduction of shrinkage stress (from 0.9 MPa to 0.6 MPa) without sacrificing the modulus (3100 ± 300 MPa) or glass transition temperature (62 ± 3 °C). Moreover, the shrinkage stress of the composite system builds up at much later stages of the polymerization as compared to the control system. Significance Due to the capability of reducing shrinkage stress without sacrificing mechanical properties, this composite system will be a great candidate for dental composite applications. PMID:22717296

  11. Counterion condensation on heparin oligomers.

    PubMed

    Minsky, Burcu Baykal; Atmuri, Anand; Kaltashov, Igor A; Dubin, Paul L

    2013-04-08

    The electropherogram of native heparin shows a broad distribution of mobilities μ, which truncates abruptly at a notably high μ = 4.7 × 10(-4) cm(2) V(-1) s(-1). This highly skewed mobility distribution is also found for the 20-saccharide chain, which shows from mass spectrometry a more uniform (symmetrical) with respect to sulfation level. Since a partially degraded heparin exhibits oligomer peaks with μ> 5 × 10(-4) cm(2) V(-1) s(-1) (appearing to escape the limitation of the mobility value for native heparin), we examined the electrophoretic behavior of chain-length monodisperse heparin oligomers. Their mobilities varied inversely with the logarithm of the contour length, L, for L from 3 to 10 nm and reached an asymptotic limit for L > 20 nm. The generality of this effect was indicated by similar behavior for oligomers of poly(styrene sulfonate). A recent theory of polyelectrolyte end effects (Manning, G. S. Macromolecules2008, 41, 6217-6227), in which chain termini exhibit reduced counterion condensation was found to quantitatively account for these results. A qualitative explanation for the anomalously high value of μ of native heparin, 10-20% higher than those seen for synthetic polyelectrolytes of higher linear charge density, is suggested on the basis of similar junction effects (Manning, G. S. Macromolecules2008, 41, 6217-6227), which reduce counterion condensation at the interfaces of regions of high and low sulfation. We suggest that these effects should be considered in models for the biofunctionality of the regulated high and low sulfation (NS/NA) domains of heparan sulfate.

  12. Insulin Therapy

    MedlinePlus

    ... 3 hours and lasts 12 to 16 hours.Long-acting insulin (such as insulin glargine and insulin detemir) ... hard to time their meals around regular insulin injections. Sometimes they end up eating too soon or ...

  13. Synthesis of long prebiotic oligomers on mineral surfaces.

    PubMed

    Ferris, J P; Hill, A R; Liu, R; Orgel, L E

    1996-05-02

    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 acids) 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.

  14. 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.

  15. 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.

  16. Asymmetric synthesis of vinylogous β-amino acids and their incorporation into mixed backbone oligomers.

    PubMed

    Wu, Hao; An, Hongchan; Mo, Shuting Cynthia; Kodadek, Thomas

    2017-03-27

    Chiral vinylogous β-amino acids (VBAA) were synthesized using enantioselective Mannich reactions of aldehydes with in situ generated N-carbamoyl imines followed by a Horner-Wadsworth-Emmons reaction. The efficiency with which these units could be incorporated into oligomers with different moieties on the C- and N-terminal sides was established, as was the feasibility of sequencing oligomers containing VBAAs by tandem mass spectrometry. The data show that VBAAs will be useful building blocks for the construction of combinatorial libraries of peptidomimetic compounds.

  17. Deuteration-induced scission of C{sub 58} oligomers

    SciTech Connect

    Loeffler, Daniel; Jester, Stefan-S.; Weis, Patrick; Boettcher, Artur; Kappes, Manfred M.

    2006-12-14

    The reaction of solid C{sub 58} films with atomic deuterium to yield deuterofullerenes, C{sub 58}D{sub x}, has been investigated by thermal desorption spectroscopy coupled with mass spectrometric detection, ultraviolet photoionization spectroscopy (21.2 eV), and atomic force microscopy (AFM). The average composition of the deuterofullerenes created depends on deuterium dose, beam flux, and surface temperature. Low deuterium exposures at room temperature yield predominantly C{sub 58}D{sub 6-8} cages. Saturation exposures at room temperature yield mass spectra peaked at C{sub 58}D{sub 26}. After saturation exposures at elevated surface temperatures ({approx}500 K), the (subsequently) desorbed material reveals a comparatively narrow mass spectral distribution centered at C{sub 58}D{sub 30}. Deuteration is associated with cleavage of covalent cage-cage bonds in the starting C{sub 58} oligomer material, as evidenced by a considerable lowering of the sublimation energies of C{sub 58}D{sub x} compared to desorption of C{sub 58} desorbed from pure oligomer films. Correspondingly, AFM images reveal a D-induced, thermally activated transition from dendritic C{sub 58} oligomer islands into smooth-rimmed islands composed of deuterated cages. Deuterated films exhibit a significantly lower work function than bare C{sub 58} films. Progressing deuteration also gradually raises the surface ionization potential.

  18. A nonsense mutation causing decreased levels of insulin receptor mRNA: Detection by a simplified technique for direct sequencing of genomic DNA amplified by the polymerase chain reaction

    SciTech Connect

    Kadowaki, T.; Kadowaki, H.; Taylor, S.I. )

    1990-01-01

    Mutations in the insulin receptor gene can render the cell resistant to the biological action of insulin. The authors have studied a patient with leprechaunism (leprechaun/Minn-1), a genetic syndrome associated with intrauterine growth retardation and extreme insulin resistance. Genomic DNA from the patient was amplified by the polymerase chain reaction catalyzed by Thermus aquaticus (Taq) DNA polymerase, and the amplified DNA was directly sequenced. A nonsense mutations was identified at codon 897 in exon 14 in the paternal allele of the patient's insulin receptor gene. Levels of insulin receptor mRNA are decreased to <10% of normal in Epstein-Barr virus-transformed lymphoblasts and cultured skin fibroblasts from this patient. Thus, this nonsense mutation appears to cause a decrease in the levels of insulin receptor mRNA. In addition, they have obtained indirect evidence that the patient's maternal allele of the insulin receptor gene contains a cis-acting dominant mutation that also decreases the level of mRNA, but by a different mechanism. The nucleotide sequence of the entire protein-coding domain and the sequences of the intron-exon boundaries for all 22 exons of the maternal allele were normal. Presumably, the mutation in the maternal allele maps elsewhere in the insulin receptor gene. Thus, they conclude that the patient is a compound heterozygote for two cis-acting dominant mutations in the insulin receptor gene: (i) a nonsense mutation in the paternal allel that reduces the level of insulin receptor mRNA and (ii) an as yet unidentified mutation in the maternal allele that either decreases the rate of transcription or decreases the stability of the mRNA.

  19. Monitoring Insulin Aggregation via Capillary Electrophoresis

    PubMed Central

    Pryor, Elizabeth; Kotarek, Joseph A.; Moss, Melissa A.; Hestekin, Christa N.

    2011-01-01

    Early stages of insulin aggregation, which involve the transient formation of oligomeric aggregates, are an important aspect in the progression of Type II diabetes and in the quality control of pharmaceutical insulin production. This study is the first to utilize capillary electrophoresis (CE) with ultraviolet (UV) detection to monitor insulin oligomer formation at pH 8.0 and physiological ionic strength. The lag time to formation of the first detected species in the aggregation process was evaluated by UV-CE and thioflavin T (ThT) binding for salt concentrations from 100 mM to 250 mM. UV-CE had a significantly shorter (5–8 h) lag time than ThT binding (15–19 h). In addition, the lag time to detection of the first aggregated species via UV-CE was unaffected by salt concentration, while a trend toward an increased lag time with increased salt concentration was observed with ThT binding. This result indicates that solution ionic strength impacts early stages of aggregation and β-sheet aggregate formation differently. To observe whether CE may be applied for the analysis of biological samples containing low insulin concentrations, the limit of detection using UV and laser induced fluorescence (LIF) detection modes was determined. The limit of detection using LIF-CE, 48.4 pM, was lower than the physiological insulin concentration, verifying the utility of this technique for monitoring biological samples. LIF-CE was subsequently used to analyze the time course for fluorescein isothiocyanate (FITC)-labeled insulin oligomer formation. This study is the first to report that the FITC label prevented incorporation of insulin into oligomers, cautioning against the use of this fluorescent label as a tag for following early stages of insulin aggregation. PMID:22272138

  20. Insulin Basics

    MedlinePlus

    ... long insulin continues to lower blood glucose. Insulin Strength All insulins come dissolved or suspended in liquids. The standard and most commonly used strength in the United States today is U-100, ...

  1. Pathogenesis of Abeta oligomers in synaptic failure.

    PubMed

    Sivanesan, Senthilkumar; Tan, Aaron; Rajadas, Jayakumar

    2013-03-01

    The soluble Abeta oligomers in brain are highly correlated with memory related synaptic dysfunctions in Alzheimer's disease (AD). However, more recent studies implicate the involvement of Abeta dimers and trimers in memory related AD pathology. Apparently, Abeta oligomers can bind with cellular prion protein at the membrane receptors, forming annular amyloid pores and membrane ion channels to induce aberrant spine cytoskeletal changes. Hence synapse targeting of Abeta oligomers involves activation of many receptors such as N-Methyl-D-aspartate (NMDA), alpha-amino-3- hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), nicotinic acetylcholine (nAChRs), p75 neurotrophin (p75NTR) following aberrant clustering of metabotropic glutamate receptors (mGluR5) leading to neuronal loss and LTP failure. In particular, NMDA and AMPA receptor activation by soluble amyloid oligomers involves calcium mediated mitochondrial dysfunction, decreased Ca((2+))/calmodulin-dependent protein kinase II (CaMKII) levels at the synapses accompanying dramatic loss of synaptic proteins such as postsynaptic density-95 (PSD-95), dynamin-1 and synaptophysin. This kind of receptor-Abeta oligomer interaction might eventually affect the neuronal membrane integrity by altering dielectric barrier, various synaptic proteins, spine morphology and density and P/Q calcium currents that might provoke a cascade of events leading to neuronal loss and memory failure. In this review, we try to explain in detail the various possible mechanisms that connect Abeta oligomers with synapse damage and memory failure.

  2. 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.

  3. Self-propagative replication of Aβ oligomers suggests potential transmissibility in Alzheimer disease.

    PubMed

    Kumar, Amit; Pate, Kayla M; Moss, Melissa A; Dean, Dexter N; Rangachari, Vijayaraghavan

    2014-01-01

    The aggregation of amyloid-β (Aβ) peptide and its deposition in parts of the brain form the central processes in the etiology of Alzheimer disease (AD). The low-molecular weight oligomers of Aβ aggregates (2 to 30 mers) are known to be the primary neurotoxic agents whose mechanisms of cellular toxicity and synaptic dysfunction have received substantial attention in the recent years. However, how these toxic agents proliferate and induce widespread amyloid deposition throughout the brain, and what mechanism is involved in the amplification and propagation of toxic oligomer species, are far from clear. Emerging evidence based on transgenic mice models indicates a transmissible nature of Aβ aggregates and implicates a prion-like mechanism of oligomer propagation, which manifests as the dissemination and proliferation of Aβ toxicity. Despite accumulating evidence in support of a transmissible nature of Aβ aggregates, a clear, molecular-level understanding of this intriguing mechanism is lacking. Recently, we reported the characterization of unique replicating oligomers of Aβ42 (12-24 mers) in vitro called Large Fatty Acid-derived Oligomers (LFAOs) (Kumar et al., 2012, J. Biol. Chem). In the current report, we establish that LFAOs possess physiological activity by activating NF-κB in human neuroblastoma cells, and determine the experimental parameters that control the efficiency of LFAO replication by self-propagation. These findings constitute the first detailed report on monomer - oligomer lateral propagation reactions that may constitute potential mechanism governing transmissibility among Aβ oligomers. These data support the previous reports on transmissible mechanisms observed in transgenic animal models.

  4. Montmorillonite catalysis of RNA oligomer formation in aqueous solution. A model for the prebiotic formation of RNA

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Ertem, G.

    1993-01-01

    Oligomers of adenylic acid of up to the 11-mer in length are formed by the reaction of the phosphorimidazolide of adenosine (ImpA) in pH 8 aqueous solution at room temperature in the presence of Na(+)-montmorillonite. These oligomers are joined by phosphodiester bonds in which the 3',5'-linkage predominates over the 2',5'-linkage by a 2:1 ratio. Reaction of a 9:1 mixture of ImpA, A5'ppA results in the formation of oligomers with a 3:1 ratio of 3',5'- to 2',5'-linked phosphodiester bonds. A high proportion of these oligomers contain the A5'ppA grouping. A5'ppA reacts much more rapidly with ImpA than does 5'-ADP (ppA) or 5'-ATP (pppA). The exchangeable cation associated with the montmorillonite effects the observed catalysis with Li+, Na+, NH4+, and Ca2+ being the more effective while Mg2+ and Al3+ are almost ineffective catalysts. 2',5'-Linked oligomers, up to the tetramer in length, are formed using UO2(2+)-montmorillonite. The structure analysis of individual oligomer fractions was performed by selective enzymatic and KOH hydrolytic studies followed by HPLC analysis of the reaction products. It is concluded from the composition of the oligomers that the rate of addition ImpA to a 3'-terminus containing a 2',5'-linkage is slower than the addition to a nucleoside joined by a 3',5'-linked phosphodiester bond. The potential importance of mineral catalysis of the formation of RNA and other oligomers on primitive Earth is discussed.

  5. 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.

  6. 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.

  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. Insulin signaling and insulin resistance.

    PubMed

    Beale, Elmus G

    2013-01-01

    Insulin resistance or its sequelae may be the common etiology of maladies associated with metabolic syndrome (eg, hypertension, type 2 diabetes, atherosclerosis, heart attack, stroke, and kidney failure). It is thus important to understand those factors that affect insulin sensitivity. This review stems from the surprising discovery that interference with angiotensin signaling improves insulin sensitivity, and it provides a general overview of insulin action and factors that control insulin sensitivity.

  9. 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

  10. Studies in the Mineral and Salt-Catalyzed Formation of RNA Oligomers

    NASA Astrophysics Data System (ADS)

    Miyakawa, Shin; Joshi, Prakash C.; Gaffey, Michael J.; Gonzalez-Toril, Elena; Hyland, Callen; Ross, Teresa; Rybij, Kristin; Ferris, James P.

    2006-08-01

    Activated mononucleotides oligomerize in the presence of montmorillonite clay to form RNA oligomers. In the present study, effects of salts, temperature and pH on the clay-catalyzed synthesis of RNA oligomers were investigated. This reaction is favored by relatively high concentration of salts, such as 1 M NaCl. It was shown that the presence of divalent cations was not required for this reaction. High concentrations of NH4 + and HCO3 - and 0.01 M HPO4 2- inhibit the reaction. The yields of RNA oligomers decreased as the temperature was raised from 4 ^∘C to 50 ^∘C. A5' ppA was the major product at pH's below 6. The catalytic activity of a variety of minerals and three meteorites were investigated but none of them except galena catalyzed the oligomerization. ATP was generated from ADP but it was due to the presence of HEPES buffer and not due to the minerals. Meteorites catalyzed the hydrolysis of the pyrophosphate bonds of ATP. The results suggest that oligomers of RNA could have formed in pH 7-9 solutions of alkali metal salts in the presence of montmorillonite clay.

  11. Use of Doubly Charged Precursors to Validate Dissociation Mechanisms of Singly Charged Poly(Dimethylsiloxane) Oligomers

    NASA Astrophysics Data System (ADS)

    Fouquet, Thierry; Toniazzo, Valérie; Ruch, David; Charles, Laurence

    2013-07-01

    Collision-induced dissociation of doubly charged poly(dimethylsiloxane) (PDMS) molecules was investigated to provide experimental evidence for fragmentation reactions proposed to occur upon activation of singly charged oligomers. This study focuses on two PDMS species holding trimethylsilyl or methoxy end-groups and cationized with ammonium. In both cases, introduction of the additional charge did not induce significant differences in dissociation behavior, and the use of doubly charged precursors enabled the occurrence of charge-separation reactions, allowing molecules always eliminated as neutrals upon activation of singly charged oligomers to be detected as cationized species. In the case of trimethylsilyl-terminated oligomers, random location of the adducted charge combined with rapid consecutive reactions proposed to occur from singly charged precursors could be validated based on MS/MS data of doubly charged oligomers. In the case of methoxy-terminated PDMS, favored interaction of the adducted ammonium with both end-groups, proposed to rationalize the dissociation behavior of singly charged molecules, was also supported by MS/MS data obtained for molecules adducted with two ammonium cations.

  12. Lactic acid oligomers (OLAs) as prodrug moieties.

    PubMed

    Kruse, J; Lachmann, B; Lauer, R; Eppacher, S; Noe, C R

    2013-02-01

    In this paper we propose the use of lactic acid oligomers (OLAs) as prodrug moieties. Two synthetic approaches are presented, on the one hand a non selective oligomerisation of lactic acid and on the other hand a block synthesis to tetramers of lactic acid. Dimers of lactic acid were investigated with respect to their plasma stability and their adsorption to albumine. Ibuprofen was chosen as the first drug for OLAylation. The ester 19 of LA(1)-ibuprofen was evaluated with respect to the degradation to human plasma and the adsorption to albumine. All results indicate that lactic acid oligomers are promising prodrug moieties.

  13. Insulin Test

    MedlinePlus

    ... ovarian syndrome (PCOS) , prediabetes or heart disease , or metabolic syndrome . A health practitioner also may order insulin and ... such as appears in type 2 diabetes and metabolic syndrome Decreased insulin levels are seen with: Diabetes Hypopituitarism ...

  14. Designing Surface-Confined Coordination Oligomers

    SciTech Connect

    Altman, M.; Rachamim, M; Ichiki, T; Iron, M; Evmenenko, G; Dutta, P; van der Boom, M

    2010-01-01

    HOMO-LUMO engineering of coordination-based oligomers covalently bound to silicon or glass has been achieved by the use of a partially fluorinated chromophore (see graphic). The experimental and computationally derived physical chemical properties of these assemblies are compared to their non-fluorinated analogues.

  15. Glucosamine oligomers: 1. Preparation and characterization.

    PubMed

    Domard, A; Cartier, N

    1989-10-01

    Hydrolysis of chitosan in hot concentrated HCl led to chito-oligosaccharides [beta-(1----4) linked 2-amino-2-deoxy-D-glucose]. The time dependence of the distribution was studied. A convenient choice of the conditions for steric exclusion chromatography of these hydrolysates allowed the separation of the first 15 oligomers and of fractions up to DP = 40.

  16. 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

  17. Capping of Aβ42 Oligomers by Small Molecule Inhibitors

    PubMed Central

    2015-01-01

    Aβ42 peptides associate into soluble oligomers and protofibrils in the process of forming the amyloid fibrils associated with Alzheimer’s disease. The oligomers have been reported to be more toxic to neurons than fibrils, and have been targeted by a wide range of small molecule and peptide inhibitors. With single touch atomic force microscopy (AFM), we show that monomeric Aβ42 forms two distinct types of oligomers, low molecular weight (MW) oligomers with heights of 1–2 nm and high MW oligomers with heights of 3–5 nm. In both cases, the oligomers are disc-shaped with diameters of ∼10–15 nm. The similar diameters suggest that the low MW species stack to form the high MW oligomers. The ability of Aβ42 inhibitors to interact with these oligomers is probed using atomic force microscopy and NMR spectroscopy. We show that curcumin and resveratrol bind to the N-terminus (residues 5–20) of Aβ42 monomers and cap the height of the oligomers that are formed at 1–2 nm. A second class of inhibitors, which includes sulindac sulfide and indomethacin, exhibit very weak interactions across the Aβ42 sequence and do not block the formation of the high MW oligomers. The correlation between N-terminal interactions and capping of the height of the Aβ oligomers provides insights into the mechanism of inhibition and the pathway of Aβ aggregation. PMID:25422864

  18. 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.

  19. A Kinetic Model for Cell Damage Caused by Oligomer Formation.

    PubMed

    Hong, Liu; Huang, Ya-Jing; Yong, Wen-An

    2015-10-06

    It is well known that the formation of amyloid fiber may cause invertible damage to cells, although the underlying mechanism has not been fully understood. In this article, a microscopic model considering the detailed processes of amyloid formation and cell damage is constructed based on four simple assumptions, one of which is that cell damage is raised by oligomers rather than mature fibrils. By taking the maximum entropy principle, this microscopic model in the form of infinite mass-action equations together with two reaction-convection partial differential equations (PDEs) has been greatly coarse-grained into a macroscopic system consisting of only five ordinary differential equations (ODEs). With this simple model, the effects of primary nucleation, elongation, fragmentation, and protein and seeds concentration on amyloid formation and cell damage have been extensively explored and compared with experiments. We hope that our results will provide new insights into the quantitative linkage between amyloid formation and cell damage.

  20. 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.

  1. 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.

  2. 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.

  3. New Acetylene-Terminated Quinoxaline Oligomers

    DTIC Science & Technology

    1982-03-01

    diketone . In this work, we tried other bases, but potassium t-butoxide and lithium t- butoxide gave unsatisfactory results. Synthesis of acetone adduct...the most expensive ingredient. We have previously been able to improve the synthesis of the bisglyoxals needed for these adhesives,2 and are now...general method of synthesis which have been developed is to first condense the quinoxallne oligomer with glyoxal end groups. 2 r ),-CO--CO-Ar--CO--C&O--j

  4. Variability of NPH insulin preparations.

    PubMed

    Belmonte, M M; Colle, E; DeBelle, R; Murthy, D Y

    1971-01-23

    In 1968-69 certain juvenile diabetics receiving NPH insulin began having pre-breakfast glucosuria and mid-morning hypoglycemic reactions. A mail survey of our clinic population and a study done at the Quebec camp for diabetic children in 1969 revealed that certain lot numbers were associated with poor control and that a change to new lot numbers or alternate insulin preparations resulted in better control. "Suspect" insulin preparations and non-suspect insulins were given to newly diagnosed diabetics, and plasma insulin and glucose levels were measured over a 24-hour period. The data confirmed that the "suspect" insulins were causing early hypoglycemia and failing to control hyperglycemia during the latter hours of the 24-hour period. The lower glucose levels were associated with higher plasma insulin levels. The "suspect" insulins were further found to have elevated levels of free insulin in the supernatant fluid.The requirements for quality control of modified insulin preparations are reviewed and suggestions are offered for their improvement.

  5. Complement Protein C1q Forms a Complex with Cytotoxic Prion Protein Oligomers

    PubMed Central

    Erlich, Paul; Dumestre-Pérard, Chantal; Ling, Wai Li; Lemaire-Vieille, Catherine; Schoehn, Guy; Arlaud, Gérard J.; Thielens, Nicole M.; Gagnon, Jean; Cesbron, Jean-Yves

    2010-01-01

    A growing number of studies have investigated the interaction between C1q and PrP, but the oligomeric form of PrP involved in this interaction remains to be determined. Aggregation of recombinant full-length murine PrP in the presence of 100 mm NaCl allowed us to isolate three different types of oligomers by size-exclusion chromatography. In contrast to PrP monomers and fibrils, these oligomers activate the classical complement pathway, the smallest species containing 8–15 PrP protomers being the most efficient. We used Thioflavine T fluorescence to monitor PrP aggregation and showed that, when added to the reaction, C1q has a cooperative effect on PrP aggregation and leads to the formation of C1q-PrP complexes. In these complexes, C1q interacts through its globular domains preferentially with the smallest oligomers, as shown by electron microscopy, and retains the ability to activate the classical complement pathway. Using two cell lines, we also provide evidence that C1q inhibits the cytotoxicity induced by the smallest PrP oligomers. The cooperative interaction between C1q and PrP could represent an early step in the disease, where it prevents elimination of the prion seed, leading to further aggregation. PMID:20410306

  6. 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.

  7. Synthesis of a new π-conjugated redox oligomer: Electrochemical and optical investigation

    NASA Astrophysics Data System (ADS)

    Blili, Saber; Zaâboub, Zouhour; Maaref, Hassen; Haj Said, Ayoub

    2017-01-01

    A new π-conjugated redox oligomer was prepared according a two-Step Synthesis. Firstly, an oligophenylene (OMPA) was obtained from the anodic oxidation of the (4-methoxyphenyl)acetonitrile. Then, the resulting material was chemically modified by the Knoevenagel condensation with the ferrocenecarboxaldehyde. This reaction led to a redox-conjugated oligomer the Fc-OMPA. The synthesized material was characterized using different spectroscopic techniques: NMR, FTIR, UV-vis and photoluminescence (PL) spectroscopy. The Fc-OMPA was used to modify a platinum electrode surface and the electrochemical response of the ferrocene redox-center was investigated by cyclic voltammetry. Moreover, the room temperature PL spectra of Fc-OMPA revealed that the ferrocene moiety, which acts as an electron donor, can effectively quench the oligomer luminescence. However, when ferrocene was oxidized to ferrocenium ion, the intramolecular charge transfer process was prevented which consequently enhanced the light emission. Thus, the oligomer light-emission can be, chemically or electrochemically tuned. The obtained results showed that the prepared material is a good candidate for the elaboration of electrochemical sensors and for the development of luminescent Redox-switchable devices.

  8. 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.

  9. From N-vinylpyrrolidone anions to modified paraffin-like oligomers via double alkylation with 1,8-dibromooctane: access to covalent networks and oligomeric amines for dye attachment

    PubMed Central

    Obels, Daniela; Lievenbrück, Melanie

    2016-01-01

    Summary The double alkylation of N-vinylpyrrolidone (N-VP) with 1,8-dibromooctane yields paraffin-like oligomeric chains bearing polymerizable vinyl moieties. These oligomers were radically crosslinked in bulk with N-VP as co-monomer yielding swellable polymer disks. The vinylic side groups of the N-VP oligomers allow thiol–ene click reactions with 2-aminoethanethiol hydrochloride to obtain reactive amino-functionalized oligomers. Further modification of the free amino groups with 1,4-difluoro-9,10-anthraquinone (DFA) yields red-colored oligomeric anthraquinone dyes. The final reaction of DFA-substituted N-VP oligomers with Jeffamine® M 600 leads to blue-colored and branched oligomers with poly(ethylene glycol) side chains. PMID:27559389

  10. 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.

  11. Amyloid β-protein oligomers and Alzheimer’s disease

    PubMed Central

    2013-01-01

    The oligomer cascade hypothesis, which states that oligomers are the initiating pathologic agents in Alzheimer’s disease, has all but supplanted the amyloid cascade hypothesis, which suggested that fibers were the key etiologic agents in Alzheimer’s disease. We review here the results of in vivo, in vitro and in silico studies of amyloid β-protein oligomers, and discuss important caveats that should be considered in the evaluation of these results. This article is divided into four sections that mirror the main approaches used in the field to better understand oligomers: (1) attempts to locate and examine oligomers in vivo in situ; that is, without removing these species from their environment; (2) studies involving oligomers extracted from human or animal tissues and the subsequent characterization of their properties ex vivo; (3) studies of oligomers that have been produced synthetically and studied using a reductionist approach in relatively simple in vitro biophysical systems; and (4) computational studies of oligomers in silico. These multiple orthogonal approaches have revealed much about the molecular and cell biology of amyloid β-protein. However, as informative as these approaches have been, the amyloid β-protein oligomer system remains enigmatic. PMID:24289820

  12. 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.

  13. Macrocyclic 2,7-Anthrylene Oligomers.

    PubMed

    Yamamoto, Yuta; Wakamatsu, Kan; Iwanaga, Tetsuo; Sato, Hiroyasu; Toyota, Shinji

    2016-05-06

    A macrocyclic compound consisting of six 2,7-anthrylene units was successfully synthesized by Ni-mediated coupling of the corresponding dibromo precursor as a novel π-conjugated compound. This compound was sufficiently stable and soluble in organic solvents due to the presence of mesityl groups. X-ray analysis showed that the molecule had a nonplanar and hexagonal wheel-shaped framework of approximately S6 symmetry. The dynamic process between two S6 structures was observed by using the dynamic NMR technique, the barrier being 58 kJ mol(-1) . The spectroscopic properties of the hexamer were compared with those of analogous linear oligomers.

  14. 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.

  15. Transesterification of PHA to Oligomers Covalently Bonded with (Bio)Active Compounds Containing Either Carboxyl or Hydroxyl Functionalities

    PubMed Central

    Kwiecień, Iwona; Radecka, Iza; Kowalczuk, Marek; Adamus, Grażyna

    2015-01-01

    This manuscript presents the synthesis and structural characterisation of novel biodegradable polymeric controlled-release systems of pesticides with potentially higher resistance to weather conditions in comparison to conventional forms of pesticides. Two methods for the preparation of pesticide-oligomer conjugates using the transesterification reaction were developed. The first method of obtaining conjugates, which consist of bioactive compounds with the carboxyl group and polyhydroxyalkanoates (PHAs) oligomers, is "one-pot" transesterification. In the second method, conjugates of bioactive compounds with hydroxyl group and polyhydroxyalkanoates oligomers were obtained in two-step method, through cyclic poly(3-hydroxybutyrate) oligomers. The obtained pesticide-PHA conjugates were comprehensively characterised using GPC, 1H NMR and mass spectrometry techniques. The structural characterisation of the obtained products at the molecular level with the aid of mass spectrometry confirmed that both of the synthetic strategies employed led to the formation of conjugates in which selected pesticides were covalently bonded to PHA oligomers via a hydrolysable ester bond. PMID:25781908

  16. Depolymerisation optimisation of cranberry procyanidins and transport of resultant oligomers on monolayers of human intestinal epithelial Caco-2 cells.

    PubMed

    Ou, Keqin; Gu, Liwei

    2015-01-15

    Procyanidins in cranberries are predominantly polymers (>85%). The objective of this study was to optimise the depolymerisation of polymers and to investigate the absorption of resultant oligomers on Caco-2 cell monolayers. Depolymerisation conditions were optimised using response surface methodology. Depolymerisation, with or without added epicatechin, yielded 644 μg and 202 μg of oligomers (monomer through tetramers) per mg of partially purified polymers (PP), respectively. Oligomers (yielded from both methods) were transported through Caco-2 cell monolayer despite absorption rates being low. With the aid of response surface methodology, the optimum depolymerisation conditions were determined to be 60°C, 0.1M HCl in methanol and 3h without added epicatechin. The predicted maximum yield was 364 μg oligomers per mg of PP. The optimum depolymerisation condition with added epicatechin shared the same temperature, acid concentration and reaction time, in addition to an epicatechin/PP mass ratio of 2.19. Its predicted maximum oligomer yield was 1,089 μg/mg. The predicted yields were verified by experimental data.

  17. Oligomer formation during gas-phase ozonolysis of small alkenes and enol ethers: new evidence for the central role of the Criegee Intermediate as oligomer chain unit

    NASA Astrophysics Data System (ADS)

    Sadezky, A.; Winterhalter, R.; Kanawati, B.; Römpp, A.; Spengler, B.; Mellouki, A.; Le Bras, G.; Chaimbault, P.; Moortgat, G. K.

    2008-05-01

    An important fraction of secondary organic aerosol (SOA) formed by atmospheric oxidation of diverse volatile organic compounds (VOC) has recently been shown to consist of high-molecular weight oligomeric species. In our previous study (Sadezky et al., 2006), we reported the identification and characterization of oligomers as main constituents of SOA from gas-phase ozonolysis of small enol ethers. These oligomers contained repeated chain units of the same chemical composition as the main Criegee Intermediates (CI) formed during the ozonolysis reaction, which were CH2O2 (mass 46) for alkyl vinyl ethers (AVE) and C2H4O2 (mass 60) for ethyl propenyl ether (EPE). In the present work, we extend our previous study to another enol ether (ethyl butenyl ether EBE) and a variety of structurally related small alkenes (trans-3-hexene, trans-4-octene and 2,3-dimethyl-2-butene). Experiments have been carried out in a 570 l spherical glass reactor at atmospheric conditions in the absence of seed aerosol. SOA formation was measured by a scanning mobility particle sizer (SMPS). SOA filter samples were collected and chemically characterized off-line by ESI(+)/TOF MS and ESI(+)/TOF MS/MS, and elemental compositions were determined by ESI(+)/FTICR MS and ESI(+)/FTICR MS/MS. The results for all investigated unsaturated compounds are in excellent agreement with the observations of our previous study. Analysis of the collected SOA filter samples reveal the presence of oligomeric compounds in the mass range 200 to 800 u as major constituents. The repeated chain units of these oligomers are shown to systematically have the same chemical composition as the respective main Criegee Intermediate (CI) formed during ozonolysis of the unsaturated compounds, which is C3H6O2 (mass 74) for ethyl butenyl ether (EBE), trans-3-hexene, and 2,3-dimethyl-2-butene, and C4H8O2 (mass 88) for trans-4-octene. Analogous fragmentation pathways among the oligomers formed by gas-phase ozonolysis of the different

  18. 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.

  19. Computing highly specific and mismatch tolerant oligomers efficiently.

    PubMed

    Yamada, Tomoyuki; Morishita, Shinichi

    2003-01-01

    The sequencing of the genomes of a variety of species and the growing databases containing expressed sequence tags (ESTs) and complementary DNAs (cDNAs) facilitate the design of highly specific oligomers for use as genomic markers, PCR primers, or DNA oligo microarrays. The first step in evaluating the specificity of short oligomers of about twenty units in length is to determine the frequencies at which the oligomers occur. However, for oligomers longer than about fifty units this is not efficient, as they usually have a frequency of only 1. A more suitable procedure is to consider the mismatch tolerance of an oligomer, that is, the minimum number of mismatches that allows a given oligomer to match a sub-sequence other than the target sequence anywhere in the genome or the EST database. However, calculating the exact value of mismatch tolerance is computationally costly and impractical. Therefore, we studied the problem of checking whether an oligomer meets the constraint that its mismatch tolerance is no less than a given threshold. Here, we present an efficient dynamic programming algorithm solution that utilizes suffix and height arrays. We demonstrated the effectiveness of this algorithm by efficiently computing a dense list of oligo-markers applicable to the human genome. Experimental results show that the algorithm runs faster than well-known Abrahamson's algorithm by orders of magnitude and is able to enumerate 63% to approximately 79% of qualified oligomers.

  20. Computing highly specific and noise-tolerant oligomers efficiently.

    PubMed

    Yamada, Tomoyuki; Morishita, Shinichi

    2004-03-01

    The sequencing of the genomes of a variety of species and the growing databases containing expressed sequence tags (ESTs) and complementary DNAs (cDNAs) facilitate the design of highly specific oligomers for use as genomic markers, PCR primers, or DNA oligo microarrays. The first step in evaluating the specificity of short oligomers of about 20 units in length is to determine the frequencies at which the oligomers occur. However, for oligomers longer than about fifty units this is not efficient, as they usually have a frequency of only 1. A more suitable procedure is to consider the mismatch tolerance of an oligomer, that is, the minimum number of mismatches that allows a given oligomer to match a substring other than the target sequence anywhere in the genome or the EST database. However, calculating the exact value of mismatch tolerance is computationally costly and impractical. Therefore, we studied the problem of checking whether an oligomer meets the constraint that its mismatch tolerance is no less than a given threshold. Here, we present an efficient dynamic programming algorithm solution that utilizes suffix and height arrays. We demonstrated the effectiveness of this algorithm by efficiently computing a dense list of numerous oligo-markers applicable to the human genome. Experimental results show that the algorithm runs faster than well-known Abrahamson's algorithm by orders of magnitude and is able to enumerate 65% approximately 76% of qualified oligomers.

  1. Hyaluronan synthase assembles chitin oligomers with -GlcNAc(α1→)UDP at the reducing end.

    PubMed

    Weigel, Paul H; West, Christopher M; Zhao, Peng; Wells, Lance; Baggenstoss, Bruce A; Washburn, Jennifer L

    2015-06-01

    Class I hyaluronan synthases (HASs) assemble a polysaccharide containing the repeating disaccharide [GlcNAc(β1,4)GlcUA(β1,3)]n-UDP and vertebrate HASs also assemble (GlcNAc-β1,4)n homo-oligomers (chitin) in the absence of GlcUA-UDP. This multi-membrane domain CAZy GT2 family glycosyltransferase, which couples HA synthesis and translocation across the cell membrane, is atypical in that monosaccharides are incrementally assembled at the reducing, rather than the non-reducing, end of the growing polymer. Using Escherichia coli membranes containing recombinant Streptococcus equisimilis HAS, we demonstrate that a prokaryotic Class I HAS also synthesizes chitin oligomers (up to 15-mers, based on MS and MS/MS analyses of permethylated products). Furthermore, chitin oligomers were found attached at their reducing end to -4GlcNAc(α1→)UDP [i.e. (GlcNAcβ1,4)nGlcNAc(α1→)UDP]. These oligomers, which contained up to at least seven HexNAc residues, consisted of β4-linked GlcNAc residues, based on the sensitivity of the native products to jack bean β-N-acetylhexosaminidase. Interestingly, these oligomers exhibited mass defects of -2, or -4 for longer oligomers, that strictly depended on conjugation to UDP, but MS/MS analyses indicate that these species result from chemical dehydrogenations occurring in the gas phase. Identification of (GlcNAc-β1,4)n-GlcNAc(α1→)UDP as HAS reaction products, made in the presence of GlcNAc(α1→)UDP only, provides strong independent confirmation for the reducing terminal addition mechanism. We conclude that chitin oligomer products made by HAS are derived from the cleavage of these novel activated oligo-chitosyl-UDP oligomers. Furthermore, it is possible that these UDP-activated chitin oligomers could serve as self-assembled primers for initiating HA synthesis and ultimately modify the non-reducing terminus of HA with a chitin cap.

  2. Origin and diversification of a metabolic cycle in oligomer world.

    PubMed

    Nishio, Tomoaki; Narikiyo, Osamu

    2013-02-01

    Based on the oligomer-world hypothesis we propose an abstract model where the molecular recognition among oligomers is described in the shape space. The origin of life in the oligomer world is regarded as the establishment of a metabolic cycle in a primitive cell. The cycle is sustained by the molecular recognition. If an original cell acquires the ability of the replication of oligomers, the relationship among oligomers changes due to the poor fidelity of the replication. This change leads to the diversification of metabolic cycles. The selection among diverse cycles is the basis of the evolution. The evolvability is one of the essential characters of life. We demonstrate the origin and diversification of the metabolic cycle by the computer simulation of our model. Such a simulation is expected to be the simplified demonstration of what actually occurred in the primordial soup. Our model describes an analog era preceding the digital era based on the genetic code.

  3. Non-aqueous dispersion coatings based on crystalline oligomers

    SciTech Connect

    Jones, F.N.

    1993-12-31

    Amorphous oligomers and polymers are generally used in coatings; crystalline ones are avoided because of the difficulty of achieving homogeneous, defect-free films. However, dispersions of crystalline oligomers offer potential advantages of stability, useful application rheology, and excellent film properties. The authors describe non-aqueous dispersions of mixtures of crystalline and amorphous oligomers. An example is a dispersion of mixtures of crystalline (at ambient temperature) hydroxyl-functional oligomer of terephthalic acid and 1,6-hexanediol mixed with an amorphous hydroxyl-functional oligomer of terephthalic acid and glycidyl neodecanote. Microscopy, WAXD and DSC indicate that the dispersion particles are crystalline and have a diameter of 5 to 20 {mu}m. The dispersions are stable and are thixotropic. Coatings formulated with melamine and polyisocyanate resin crosslinkers form glossy, transparent film with excellent mechanical properties.

  4. 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.

  5. Glucosamine oligomers: 4. Solid state-crystallization and sustained dissolution.

    PubMed

    Domard, A; Cartier, N

    1992-04-01

    When glucosamine oligomers are stored in the solid state they undergo a process of crystallization. The extent to which this occurs depends on whether the samples are isolated in the -NH3+ or -NH2 form, on the storage time, and on the degree of polymerization of the isolated oligomer. The allomorph obtained by this process seems to correspond to the so-called 'tendon-chitosan'. Dissolution of such aged oligomer samples gives rise to a process of dissociation of the associated chains in the crystal, leading to the establishment of a pseudo-equilibrium between single and associated oligomer chains and hence the simultaneous presence of the 'monomeric', 'dimeric', 'trimeric', etc., forms of the oligomer. The phenomenon cannot be attributed to a process of aggregation in solution. The effects of various parameters on this behaviour have been investigated.

  6. Soluble Aβ oligomer production and toxicity

    PubMed Central

    Larson, Megan E.; Lesné, Sylvain E.

    2011-01-01

    For nearly 100 years following the first description of this neurological disorder by Dr. Alois Alzheimer, amyloid plaques and neurofibrillary tangles have been hypothesized to cause neuronal loss. With evidence that the extent of insoluble, deposited amyloid poorly correlated with cognitive impairment, research efforts focused on soluble forms of Aβ, also referred as Aβ oligomers. Following a decade of studies, soluble oligomeric forms of Aβ are now believed to induce the deleterious cascade(s) involved in the pathophysiology of Alzheimer’s disease. In this review, we will discuss our current understanding about endogenous oligomeric Aβ production, their relative toxicity in vivo and in vitro, and explore the potential future directions needed for the field. PMID:22121920

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

    PubMed

    Pieri, Laura; Madiona, Karine; Melki, Ronald

    2016-04-14

    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.

  8. 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

  9. A Generic Method for Design of Oligomer-Specific Antibodies

    PubMed Central

    Brännström, Kristoffer; Lindhagen-Persson, Malin; Gharibyan, Anna L.; Iakovleva, Irina; Vestling, Monika; Sellin, Mikael E.; Brännström, Thomas; Morozova-Roche, Ludmilla; Forsgren, Lars; Olofsson, Anders

    2014-01-01

    Antibodies that preferentially and specifically target pathological oligomeric protein and peptide assemblies, as opposed to their monomeric and amyloid counterparts, provide therapeutic and diagnostic opportunities for protein misfolding diseases. Unfortunately, the molecular properties associated with oligomer-specific antibodies are not well understood, and this limits targeted design and development. We present here a generic method that enables the design and optimisation of oligomer-specific antibodies. The method takes a two-step approach where discrimination between oligomers and fibrils is first accomplished through identification of cryptic epitopes exclusively buried within the structure of the fibrillar form. The second step discriminates between monomers and oligomers based on differences in avidity. We show here that a simple divalent mode of interaction, as within e.g. the IgG isotype, can increase the binding strength of the antibody up to 1500 times compared to its monovalent counterpart. We expose how the ability to bind oligomers is affected by the monovalent affinity and the turnover rate of the binding and, importantly, also how oligomer specificity is only valid within a specific concentration range. We provide an example of the method by creating and characterising a spectrum of different monoclonal antibodies against both the Aβ peptide and α-synuclein that are associated with Alzheimer's and Parkinson's diseases, respectively. The approach is however generic, does not require identification of oligomer-specific architectures, and is, in essence, applicable to all polypeptides that form oligomeric and fibrillar assemblies. PMID:24618582

  10. 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

  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.

  12. Insulin Lispro Injection

    MedlinePlus

    ... unless it is used in an external insulin pump. In patients with type 2 diabetes, insulin lispro ... also can be used with an external insulin pump. Before using insulin lispro in a pump system, ...

  13. Comparison of automated pre-column and post-column analysis of amino acid oligomers

    NASA Technical Reports Server (NTRS)

    Chow, J.; Orenberg, J. B.; Nugent, K. D.

    1987-01-01

    It has been shown that various amino acids will polymerize under plausible prebiotic conditions on mineral surfaces, such as clays and soluble salts, to form varying amounts of oligomers (n = 2-6). The investigations of these surface reactions required a quantitative method for the separation and detection of these amino acid oligomers at the picomole level in the presence of nanomole levels of the parent amino acid. In initial high-performance liquid chromatography (HPLC) studies using a classical postcolumn o-phthalaldehyde (OPA) derivatization ion-exchange HPLC procedure with fluorescence detection, problems encountered included lengthy analysis time, inadequate separation and large relative differences in sensitivity for the separated species, expressed as a variable fluorescent yield, which contributed to poor quantitation. We have compared a simple, automated, pre-column OPA derivatization and reversed-phase HPLC method with the classical post-column OPA derivatization and ion-exchange HPLC procedure. A comparison of UV and fluorescent detection of the amino acid oligomers is also presented. The conclusion reached is that the pre-column OPA derivatization, reversed-phase HPLC and UV detection produces enhanced separation, improved sensitivity and faster analysis than post-column OPA derivatization, ion-exchange HPLC and fluorescence detection.

  14. Pramipexole prevents neurotoxicity induced by oligomers of beta-amyloid.

    PubMed

    Uberti, Daniela; Bianchi, Irene; Olivari, Luca; Ferrari-Toninelli, Giulia; Canonico, PierLuigi; Memo, Maurizio

    2007-08-27

    Here we demonstrate that pramipexole, an antiparkinsonian dopamine receptor agonist drug, exerts neuroprotective effects against beta-amyloid neurotoxicity. Using a specific protocol to test individually oligomers, fibrils, or unaggregated amyloid beta-peptide, we found pramipexole able to protect cells against oligomers and fibrils. Unaggregated amyloid beta-peptide was found unable to cause cell death. Fibrils and oligomers were also found to produce elevated amount of free radicals, and this effect was prevented by pramipexole. We propose pramipexole may become in the future a coadjuvant in the treatment of neuropathologies, besides Parkinson's disease, where amyloid beta-peptide-mediated oxidative injury exerts a relevant role.

  15. 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.

  16. Optically and redox-active ferroceneacetylene polymers and oligomers

    PubMed

    Plenio; Hermann; Sehring

    2000-05-15

    The palladium-catalyzed Sonogashira reaction can be used to build optically active, oligomeric 1,2,3-substituted ferrocenes up to the tetramer, as well as polymers, by sequential coupling of optically active (ee > 98 %), planar chiral iodoferroceneacetylenes and ferroceneacetylenes. (SFC)-1-Iodoferrocene-2-carbaldehyde (1) was reduced to the alcohol and methylated to give the corresponding methyl ether, which was Sonogashira-coupled with HC(triple bond)CSiEt3, resulting in (RFc)-1-(C(triple bond)CSiEt3)-2-methoxymethylferrocene (4) (79%, three steps). Orthometalation with tBuLi followed by quenching with 1,2-diodoethane gave (RFc)-1-(C(triple bond)CSiEt3)-2-methoxymethyl-3-iodoferrocene (5). Deprotection of the acetylene with nBu4NF resulted in (RFc)-1-ethynyl-2-methoxymethyl-3-iodoferrocene (6), which was Sonogashira-coupled with itself to produce an optically active polymer. Deprotection of 4 with nBu4NF and Sonogashira coupling of the product with 5 resulted in the dinuclear ferrocene 9. Deprotection of 9 and coupling with 5, followed by deprotection of the resulting acetylene 11, gave the trinuclear ferrocene 12. Another such sequence involving 11 and 5 produced a tetranuclear ferrocene 13. To study the electronic communication in such oligomers in more detail, two symmetrical, closely interrelated, trinuclear ferrocenes 18 and 19 were synthesized. The redox potentials of all the ferrocenes and the ferroceneacetylene polymer were determined by cyclic and square-wave voltammetry. All the metallocenes were investigated by UV/Vis spectroscopy. A linear relationship was found between lambdamax and l/n (n=number of ferrocene units in the oligomer). The polymer displayed two redox waves in the cyclic voltammogram, at 0.65 and 0.795 V. The corresponding mixed-valence oligoferrocene cations were synthesized from four ferroceneacetylenes, and their metal-metal charge transfer bands were examined by UV/Vis-NIR. The resonance exchange integrals Had, calculated on the

  17. Biomimetic peptoid oligomers as dual-action antifreeze agents

    PubMed Central

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

    2012-01-01

    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

  18. Oligomer formation during gas-phase ozonolysis of small alkenes and enol ethers: new evidence for the central role of the Criegee Intermediate as oligomer chain unit

    NASA Astrophysics Data System (ADS)

    Sadezky, A.; Winterhalter, R.; Kanawati, B.; Römpp, A.; Spengler, B.; Mellouki, A.; Le Bras, G.; Chaimbault, P.; Moortgat, G. K.

    2007-10-01

    An important fraction of secondary organic aerosol (SOA) formed by atmospheric oxidation of diverse volatile organic compounds (VOC) has recently been shown to consist of high-molecular weight oligomeric species. In our previous study (Sadezky et al., 2006), we reported the identification and characterization of oligomers as main constituents of SOA from gas-phase ozonolysis of small enol ethers. These oligomers contained repeated chain units of the same chemical composition as the main Criegee Intermediates (CI) formed during the ozonolysis reaction, which were CH2O2 (mass 46) for alkyl vinyl ethers (AVE) and C2H4O2 (mass 60) for ethyl propenyl ether (EPE). In the present work, we extend our previous study (Sadezky et al., 2006) to another enol ether (ethyl butenyl ether EBE) and a variety of structurally related small alkenes (trans-3-hexene, trans-4-octene and 2,3-dimethyl-2-butene). Experiments have been carried out in a 570 l spherical glass reactor at atmospheric conditions in the absence of seed aerosol. SOA formation was measured by a scanning mobility particle sizer (SMPS). SOA filter samples were collected and chemically characterized off-line by ESI(+)/MS-TOF and ESI(+)/MS/MS-TOF, and elemental compositions were confirmed by ESI(+)/MS/MS-FTICR. The results for all investigated unsaturated compounds are in excellent agreement with the observations of our previous study (Sadezky et al., 2006). Analysis of the collected SOA filter samples reveal the presence of oligomeric compounds in the mass range 200 to 800 u as major constituents. The repeated chain units of these oligomers are shown to systematically have the same chemical composition as the respective main Criegee Intermediate (CI) formed during ozonolysis of the unsaturated compounds, which is C3H6O2 (mass 74) for ethyl butenyl ether (EBE), trans-3-hexene, and 2,3-dimethyl-2-butene, and C4H8O2 (mass 88) for trans-4-octene. Analogous fragmentation pathways among the oligomers formed by gas

  19. Formation of critical oligomers is a key event during conformational transition of recombinant syrian hamster prion protein.

    PubMed

    Sokolowski, Fabian; Modler, Andreas Johannes; Masuch, Ralf; Zirwer, Dietrich; Baier, Michael; Lutsch, Gudrun; Moss, David Alan; Gast, Klaus; Naumann, Dieter

    2003-10-17

    We have investigated the conformational transition and aggregation process of recombinant Syrian hamster prion protein (SHaPrP90-232) by Fourier transform infrared spectroscopy, circular dichroism spectroscopy, light scattering, and electron microscopy under equilibrium and kinetic conditions. SHaPrP90-232 showed an infrared absorbance spectrum typical of proteins with a predominant alpha-helical structure both at pH 7.0 and at pH 4.2 in the absence of guanidine hydrochloride. At pH 4.2 and destabilizing conditions (0.3-2 m guanidine hydrochloride), the secondary structure of SHaPrP90-232 was transformed to a strongly hydrogen-bonded, most probably intermolecularly arranged antiparallel beta-sheet structure as indicated by dominant amide I band components at 1620 and 1691 cm-1. Kinetic analysis of the transition process showed that the decrease in alpha-helical structures and the increase in beta-sheet structures occurred concomitantly according to a bimolecular reaction. However, the concentration dependence of the corresponding rate constant pointed to an apparent third order reaction. No beta-sheet structure was formed within the dead time (190 ms) of the infrared experiments. Light scattering measurements revealed that the structural transition of SHaPrP90-232 was accompanied by formation of oligomers, whose size was linearly dependent on protein concentration. Extrapolation to zero protein concentration yielded octamers as the smallest oligomers, which are considered as "critical oligomers." The small oligomers showed spherical and annular shapes in electron micrographs. Critical oligomers seem to play a key role during the transition and aggregation process of SHaPrP90-232. A new model for the structural transition and aggregation process of the prion protein is described.

  20. Anti-insulin antibody test

    MedlinePlus

    Insulin antibodies - serum; Insulin Ab test; Insulin resistance - insulin antibodies; Diabetes - insulin antibodies ... Normally, there are no antibodies against insulin in your blood. ... different laboratories. Some labs use different measurements or ...

  1. Amyloid β oligomers in Alzheimer’s disease pathogenesis, treatment, and diagnosis

    PubMed Central

    Viola, Kirsten L.; Klein, William L.

    2015-01-01

    Protein aggregation is common to dozens of diseases including prionoses, diabetes, Parkinson’s and Alzheimer’s. Over the past 15 years, there has been a paradigm shift in understanding the structural basis for these proteinopathies. Precedent for this shift has come from investigation of soluble Aβ oligomers (AβOs), toxins now widely regarded as instigating neuron damage leading to Alzheimer’s dementia. Toxic AβOs accumulate in AD brain and constitute long-lived alternatives to the disease-defining Aβ fibrils deposited in amyloid plaques. Key experiments using fibril-free AβO solutions demonstrated that while Aβ is essential for memory loss, the fibrillar Aβ in amyloid deposits is not the agent. The AD-like cellular pathologies induced by AβOs suggest their impact provides a unifying mechanism for AD pathogenesis, explaining why early stage disease is specific for memory and accounting for major facets of AD neuropathology. Alternative ideas for triggering mechanisms are being actively investigated. Some research favors insertion of AβOs into membrane, while other evidence supports ligand-like accumulation at particular synapses. Over a dozen candidate toxin receptors have been proposed. AβO binding triggers a redistribution of critical synaptic proteins and induces hyperactivity in metabotropic and ionotropic glutamate receptors. This leads to Ca2+ overload and instigates major facets of AD neuropathology, including tau hyperphosphorylation, insulin resistance, oxidative stress, and synapse loss. Because different species of AβOs have been identified, a remaining question is which oligomer is the major pathogenic culprit. The possibility has been raised that more than one species plays a role. Despite some key unknowns, the clinical relevance of AβOs has been established, and new studies are beginning to point to co-morbidities such as diabetes and hypercholesterolemia as etiological factors. Because pathogenic AβOs appear early in the disease

  2. Subdiffusion of proteins and oligomers on membranes

    NASA Astrophysics Data System (ADS)

    Lepzelter, David; Zaman, Muhammad

    2012-11-01

    Diffusion of proteins on lipid membranes plays a central role in cell signaling processes. From a mathematical perspective, most membrane diffusion processes are explained by the Saffman-Delbrück theory. However, recent studies have suggested a major limitation in the theoretical framework, the lack of complexity in the modeled lipid membrane. Lipid domains (sometimes termed membrane rafts) are known to slow protein diffusion, but there have been no quantitative theoretical examinations of how much diffusion is slowed in a general case. We provide an overall theoretical framework for confined-domain ("corralled") diffusion. Further, there have been multiple apparent contradictions of the basic conclusions of Saffman and Delbrück, each involving cases in which a single protein or an oligomer has multiple transmembrane regions passing through a lipid phase barrier. We present a set of corrections to the Saffman-Delbrück theory to account for these experimental observations. Our corrections are able to provide a quantitative explanation of numerous cellular signaling processes that have been considered beyond the scope of the Saffman-Delbrück theory, and may be extendable to other forms of subdiffusion.

  3. Functional Diversity of Isoamylase Oligomers: The ISA1 Homo-Oligomer Is Essential for Amylopectin Biosynthesis in Rice Endosperm1[W][OA

    PubMed Central

    Utsumi, Yoshinori; Utsumi, Chikako; Sawada, Takayuki; Fujita, Naoko; Nakamura, Yasunori

    2011-01-01

    Rice (Oryza sativa) endosperm has two isoamylase (ISA) oligomers, ISA1 homo-oligomer and ISA1-ISA2 hetero-oligomer. To examine their contribution to starch synthesis, expression of the ISA1 or ISA2 gene was differently regulated in various transgenic plants. Although suppression of ISA2 gene expression caused the endosperm to have only the homo-oligomer, no significant effects were detected on the starch phenotypes. In contrast, ISA2 overexpression led to endosperm having only the hetero-oligomer, and starch synthesis in the endosperm was drastically impaired, both quantitatively and qualitatively, because the starch was devoid of typical starch features, such as thermal and x-ray diffraction properties, and water-soluble highly branched maltodextrins were accumulated. In the ISA2 overexpressed line, about 60% to 70% of the ISA1-ISA2 hetero-oligomer was bound to starch, while the ISA homo- and hetero-oligomers from the wild type were mostly present in the soluble form at the early milking stage of the endosperm. Detailed analysis of the relative amounts of homo- and hetero-oligomers in various lines also led us to the conclusion that the ISA1 homo-oligomer is essential, but not the ISA1-ISA2 oligomer, for starch production in rice endosperm. The relative amounts of ISA1 and ISA2 proteins were shown to determine the ratio of both oligomers and the stoichiometry of both ISAs in the hetero-oligomer. It was noted when compared with the homo-oligomer that all the hetero-oligomers from rice endosperm and leaf and potato (Solanum tuberosum) tuber were much more stable at 40°C. This study provides substantial data on the structural and functional diversity of ISA oligomers between plant tissues and species. PMID:21436381

  4. Organotin(IV) compounds as intramolecular transesterification catalysts in thermal depolymerization of poly(L-lactic acid) oligomer to form LL-lactide.

    PubMed

    Noda, M

    1999-11-01

    Mono-, di-, and tetraalkyl tin(IV) compounds were evaluated for the intramolecular transesterification reaction of the thermal depolymerization of poly(L-lactic acid) oligomer forming lactide by gas chromatography using a beta-cyclodextrin stationary phase capillary column. The most active catalyst was found to be monobutyltin trichloride (BuSnCl3) (8), which contains tin-halogen bonds, and the least effective was the coordinatively saturated monoorganotin derivative, monobutyltin tris(2-ethylhexanoate) (7). Coordination of the carbonyl group in the oligomer to the tin catalysts is an important factor influencing its activity.

  5. Human insulin prepared by recombinant DNA techniques and native human insulin interact identically with insulin receptors.

    PubMed Central

    Keefer, L M; Piron, M A; De Meyts, P

    1981-01-01

    Human insulin synthesized from A and B chains separately produced in Escherichia coli from cloned synthetic genes (prepared by the Eli Lilly Research Laboratories, Indianapolis, IN) was characterized by examining its interaction with human cultured lymphocytes, human circulating erythrocytes in vitro, and isolated rat fat cells. The binding behavior of the biosynthetic insulin with human cells was indistinguishable from that of native human or porcine insulins, with respect to affinity, association and dissociation kinetics, negative cooperativity, and the down-regulation of lymphocyte receptors. Similarly, the biosynthetic insulin was as potent as the native insulins in stimulating lipogenesis in isolated rat fat cells. We also examined the receptor binding characteristics of 125I-labeled human and porcine insulins monoiodinated solely at Tyr-A14, which were obtained by means of high-performance liquid chromatography of the iodination reaction mixture (this material was prepared by B. Frank, Eli Lilly Research Laboratories). In all aspects studied, the pure [TyrA14-125I]iodoinsulins were superior as tracers to the monoiodoinsulin purified by the more conventional method of gel filtration. PMID:7015337

  6. Reactions of. cap alpha. -oxides in the presence of hexamethylenetetramine and glycerine diphenyl ether

    SciTech Connect

    Nikolaev, P.V.; Sveshnikova, N.F.; Ignatov, V.A.

    1987-11-20

    Hexamethylenetetramine (HMTA) is widely used as a catalyst for the condensation and hardening of compositions based on epoxide oligomer. To provide objective information about the reaction scheme and the kinetics of reactions in which epoxide oligomers participate we studied a model reaction system. The model epoxide oligomer selected was phenyl glycidyl ether (PGE) and the ..cap alpha..,..gamma..-diphenyl ether of glycerine (GDPE). The reference substances in the differential thermal analysis were magnesium oxide, aluminum oxide, and GDPE. Monitoring of the progress of the isothermal reaction was effected by determining the ..cap alpha..-oxide group mercurimetrically. The concentration of HMTA was determined iodometrically.

  7. ortho-Phenylene oligomers with terminal push-pull substitution.

    PubMed

    He, Jian; Mathew, Sanyo M; Cornett, Sarah D; Grundy, Stephan C; Hartley, C Scott

    2012-05-07

    ortho-Phenylenes are an emerging class of helical oligomers and polymers. We have synthesized a series of push-pull-substituted o-phenylene oligomers (dimethylamino/nitro) up to the octamer. Conformational analysis of the hexamer using a combination of low-temperature NMR spectroscopy and ab initio predictions of (1)H NMR chemical shifts indicates that, like other o-phenylenes, they exist as compact helices in solution. However, the substituents are found to have a significant effect on their conformational behavior: the nitro-functionalized terminus is 3-fold more likely to twist out of the helix. Protonation of the dimethylamino group favors the helical conformer. UV/vis spectroscopy indicates that the direct charge-transfer interaction between the push-pull substituents attenuates quickly compared to other conjugated systems, with no significant charge-transfer band for oligomers longer than the trimer. On protonation of the dimethylamino group, significant bathochromic shifts with increasing oligomer length are observed: the effective conjugation length is 9 repeat units, more than twice that of the parent oligomer. This behavior may be rationalized through examination of the frontier molecular orbitals of these compounds, which exhibit greater delocalization after protonation, as shown by DFT calculations.

  8. Giving an insulin injection

    MedlinePlus

    ... want. Put the needle into and through the rubber top of the insulin bottle. Push the plunger ... longer-acting insulin. Put the needle into the rubber top of that insulin bottle. Push the plunger ...

  9. Tandem mass spectrometry of poly(methacrylic Acid) oligomers produced by negative mode electrospray ionization.

    PubMed

    Giordanengo, Rémi; Viel, Stéphane; Allard-Breton, Béatrice; Thévand, André; Charles, Laurence

    2009-01-01

    Dissociation of small poly(methyl acrylic acid) (PMAA) anions produced by electrospray was characterized by tandem mass spectrometry. Upon collisional activation, singly, and doubly deprotonated PMAA oligomers were shown to fragment via two major reactions, dehydration and decarboxylation. The elimination of a water molecule would occur between two consecutive acid groups in a charged-remote mechanism, giving rise to cyclic anhydrides, and was shown to proceed as many times as pairs of neutral pendant groups were available. As a result, the number of dehydration steps, together with the abundance of the fragment ions produced after the release of all water molecules, revealed the polymerization degree of the molecule in the particular case of doubly charged oligomers. For singly deprotonated molecules, the exact number of MAA units could be reached from the number of carbon dioxide molecules successively eliminated from the fully dehydrated precursor ions. In contrast to dehydration, decarboxylation reactions would proceed via a charge-induced mechanism. The proposed dissociation mechanisms are consistent with results commonly reported in thermal degradation studies of poly(acrylic acid) resins and were supported by accurate mass measurements. These fragmentation rules were successfully applied to characterize a polymeric impurity detected in the tested PMAA sample.

  10. One-Step Assembly of Molecular Separation Membranes by Direct Atomizing Oligomers.

    PubMed

    Fan, Hongwei; Wang, Ren; Shan, Linglong; Yan, Hao; Li, Jie; Ji, Shulan; Lin, Haiqing; Zhang, Guojun

    2017-02-01

    Polymeric membranes are important materials for efficient sieving of targeted components at the molecular level and have made significant advancement in many industrial applications such as biofuel production, water purification, fuel combustion, and carbon dioxide capture. Although their separation efficiencies have been widely investigated, lack of more efficient, greener, and lower-cost membrane fabrication mechanisms is still a major hurdle for mass production, because the conventional membrane-making process is always time-consuming, highly inefficient, and consumes a large amount of organic solvents. Herein we report a one-step assembly concept capable of directly processing low-viscosity oligomers into polymer-based molecular separation membranes in an ultrafast and green manner. This process was implemented by alternate atomizing-depositing of low-viscosity oligomers and reaction auxiliary agents onto a rotating support and followed by an ultrafast interfacial reaction under solvent-free conditions. Without the need for dissolution processing of polymer, solvent evaporation, and any post-treatments, the whole technological process could be accomplished within a few seconds/minutes, which is 2-3 orders of magnitude faster than conventional solution-coating technologies. The universality of this facile approach has also been demonstrated by successfully producing various defect-free polymeric membranes and homodispersed nanohybrid membranes with excellent and stable performance for bioalcohol production and recovery of different trace organics from dilute solutions.

  11. Insulin receptor: Interaction with nonreceptor glycoprotein from liver cell membranes

    PubMed Central

    Maturo, Joseph M.; Hollenberg, Morley D.

    1978-01-01

    In crude receptor preparations (either particulate or soluble) of rat liver membranes, the insulin receptor exhibits complicated binding kinetics (two binding plateaus, half-saturated at approximately 60 pM and 700 pM insulin) and an apparent chromatographic heterogeneity, suggested by the presence of two detectable, soluble insulin-binding components with apparent Stokes radii of 72 Å and 38 Å. In contrast, the insulin receptor isolated by affinity chromatography exhibits a simple binding isotherm (half-maximal saturation of binding at 700 pM insulin) without evidence for negative cooperativity and behaves as a single component (apparent Stokes radius of 38 Å) upon chromatography on Sepharose 6B. The apparent discrepancies between the properties of the unpurified insulin receptor and the affinity-purified receptor can be attributed to the presence in crude preparations of a nonreceptor constituent(s) having properties consistent with those of a membrane glycoprotein. A glycoprotein fraction from such crude soluble membrane preparations, freed from insulin receptor and subsequently partially purified using concanavalin-A-agarose, when combined with affinity-purified insulin receptor, causes both a reappearance of the complicated binding kinetics and an increase in the receptor's apparent Stokes radius from 38 Å to 72 Å. Similar results are observed for a glycoprotein fraction obtained from rat adipocyte membranes but are not observed for an identical fraction isolated from human erythrocyte membranes. We conclude that the insulin receptor in rat liver membranes can interact with another nonreceptor membrane glycoprotein that may represent either a nonrecognition moiety of the receptor oligomer or an effector molecule to the biological action of insulin. PMID:277909

  12. Single Particle Characterization of Aβ Oligomers in Solution

    PubMed Central

    Yusko, Erik C.; Prangkio, Panchika; Sept, David; Rollings, Ryan C.; Li, Jiali; Mayer, Michael

    2012-01-01

    Determining the pathological role of amyloids in amyloid-associated diseases will require a method for determining the dynamic distributions in size and shape of amyloid oligomers with high resolution. Here, we explored the potential of resistive-pulse sensing through lipid bilayer-coated nanopores to measure the size of individual amyloid-β oligomers directly in solution and without chemical modification. This method classified individual amyloid-β aggregates as spherical oligomers, protofibrils, or mature fibers and made it possible to account for the large heterogeneity of amyloid-β aggregate sizes. The approach revealed the distribution of protofibrillar lengths as well as the average cross-sectional area of protofibrils and fibers. PMID:22686709

  13. Proportion effect in diblock co-oligomer molecular diodes

    NASA Astrophysics Data System (ADS)

    Hu, G. C.; Zhang, G. P.; Li, Y.; Ren, J. F.; Wang, C. K.

    2014-10-01

    Based on ab-initio theory and nonequilibrium Green's function method, the effect of proportion on the rectification in pyrimidinyl-phenyl diblock co-oligomer diodes is investigated in two regimes. For a short co-oligomer diode, it is found that the 1:1 proportion of the two moieties favors the largest rectification ratio. For a long co-oligomer diode, an interesting proportion-dependent variation of the rectifying direction is observed. Furthermore, the optimal proportion for the largest rectification ratio is not 1:1 any longer. A deep understanding can be achieved by analyzing the bias-dependent transmission spectra combined with the evolution of the molecular orbitals.

  14. Aggregation of inorganic nanoparticles mediated by biomimetic oligomers.

    PubMed

    Tigger-Zaborov, Hagar; Maayan, Galia

    2015-09-14

    Assemblies of nanoparticles (NPs) have been broadly used for the construction of materials with unique spectroscopic and chiral properties for applications in various scientific disciplines such as sensing, bio-nanotechnology and medicine. Mediating the aggregation of NPs by synthetic biomimetic oligomers, namely, DNA, PNA, peptides and peptide mimics, rather than by small organic molecules has been shown to produce interesting supramolecular structures and enable the combination of the biocompatibility of the mediators and the spectroscopic properties of the NPs. Yet, the key to using this powerful approach for designing new functional materials is to understand the NPs aggregation patterns induced by biopolymers and biomimetic oligomers. Herein we describe the important developments in this field, from early studies to recent work with an emphasis on synthetic methods and tools for controlled assembly of metal NPs by biomimetic polymers and oligomers.

  15. Characterization of RNA-Like Oligomers from Lipid-Assisted Nonenzymatic Synthesis: Implications for Origin of Informational Molecules on Early Earth

    PubMed Central

    Mungi, Chaitanya V.; Rajamani, Sudha

    2015-01-01

    Prebiotic polymerization had to be a nonenzymatic, chemically driven process. These processes would have been particularly favored in scenarios which push reaction regimes far from equilibrium. Dehydration-rehydration (DH-RH) cycles are one such regime thought to have been prevalent on prebiotic Earth in niches like volcanic geothermal pools. The present study defines the optimum DH-RH reaction conditions for lipid-assisted polymerization of nucleotides. The resultant products were characterized to understand their chemical makeup. Primarily, our study demonstrates that the resultant RNA-like oligomers have abasic sites, which means these oligomers lack information-carrying capability because of losing most of their bases during the reaction process. This results from low pH and high temperature conditions, which, importantly, also allows the formation of sugar-phosphate oligomers when ribose 5'-monophosphates are used as the starting monomers instead. Formation of such oligomers would have permitted sampling of a large variety of bases on a preformed polymer backbone, resulting in “prebiotic phosphodiester polymers” prior to the emergence of modern RNA-like molecules. This suggests that primitive genetic polymers could have utilized bases that conferred greater N-glycosyl bond stability, a feature crucial for information propagation in low pH and high temperature regimes of early Earth. PMID:25569237

  16. Characterization of RNA-Like Oligomers from Lipid-Assisted Nonenzymatic Synthesis: Implications for Origin of Informational Molecules on Early Earth.

    PubMed

    Mungi, Chaitanya V; Rajamani, Sudha

    2015-01-05

    Prebiotic polymerization had to be a nonenzymatic, chemically driven process. These processes would have been particularly favored in scenarios which push reaction regimes far from equilibrium. Dehydration-rehydration (DH-RH) cycles are one such regime thought to have been prevalent on prebiotic Earth in niches like volcanic geothermal pools. The present study defines the optimum DH-RH reaction conditions for lipid-assisted polymerization of nucleotides. The resultant products were characterized to understand their chemical makeup. Primarily, our study demonstrates that the resultant RNA-like oligomers have abasic sites, which means these oligomers lack information-carrying capability because of losing most of their bases during the reaction process. This results from low pH and high temperature conditions, which, importantly, also allows the formation of sugar-phosphate oligomers when ribose 5'-monophosphates are used as the starting monomers instead. Formation of such oligomers would have permitted sampling of a large variety of bases on a preformed polymer backbone, resulting in "prebiotic phosphodiester polymers" prior to the emergence of modern RNA-like molecules. This suggests that primitive genetic polymers could have utilized bases that conferred greater N-glycosyl bond stability, a feature crucial for information propagation in low pH and high temperature regimes of early Earth.

  17. Ethynyl-Terminated Ester Oligomers and Polymers

    NASA Technical Reports Server (NTRS)

    Hergenrother, P. M.; Havens, S. J.

    1985-01-01

    Polyesters of various molecular weights terminated with ethynyl groups. As ethynyl-terminated polyesters are exposed to elevated temperatures, thermally induced reaction of ethynyl groups occurs to provide cross-linking and chain extension. Reaction raises use temperature of polymer and greatly improves resistance to solvents. New materials produced by this process potentially useful as adhesives, composite matrices, solvent-resistant coatings, membranes, and films.

  18. Amino siloxane oligomer-linked graphene oxide as an efficient adsorbent for removal of Pb(II) from wastewater.

    PubMed

    Luo, Shenglian; Xu, Xiangli; Zhou, Guiyin; Liu, Chengbin; Tang, Yanhong; Liu, Yutang

    2014-06-15

    A high performance sorbent, oligomer-linked graphene oxide (GO) composite, was prepared through simple cross-linking reactions between GO sheets and poly3-aminopropyltriethoxysilane (PAS) oligomers as crosslinking agents. The three-dimensional PAS oligomers prevented GO sheets from aggregation, provided foreign molecules with easier access, and introduced a large amount of amino functional groups. The morphology, structure and property of the PAS-GO composite were determined by scanning electron microscope (SEM), transmission electron microscope (TEM), Fourie transform infrared (FTIR), X-ray diffractometer (XRD), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The adsorption performance of PAS-GO was investigated in removing Pb(II) ions from water. Compared to 3-aminopropyltriethoxysilane functionalized GO (AS-GO) which was prepared by the direct reaction between 3-aminopropyltriethoxysilane and GO, PAS-GO exhibited much higher adsorptivity toward Pb(II) with the maximum adsorption capacity of 312.5mg/g at 303 K and furthermore the maximum adsorption capacity increased with increasing temperature. The adsorption could be conducted in a wide pH range of 4.0-7.0. Importantly, PAS-GO had a priority tendency to adsorb Pb, Cu and Fe from a mixed solution of metal ions, especially from a practical industrial effluent.

  19. Direct detection of alpha synuclein oligomers in vivo

    PubMed Central

    2013-01-01

    Background Rat models of Parkinson’s disease are widely used to elucidate the mechanisms underlying disease etiology or to investigate therapeutic approaches. Models were developed using toxins such as MPTP or 6-OHDA to specifically target dopaminergic neurons resulting in acute neuronal loss in the substantia nigra or by using viral vectors to induce the specific and gradual expression of alpha synuclein in the substantia nigra. The detection of alpha- synuclein oligomers, the presumed toxic species, in these models and others has been possible using only indirect biochemical approaches to date. Here we coinjected AAVs encoding alpha-synuclein fused to the N- or C-terminal half of VenusYFP in rat substantia nigra pars compacta and describe for the first time a novel viral vector rodent model with the unique ability to directly detect and track alpha synuclein oligomers ex vivo and in vivo. Results Viral coinjection resulted in widespread VenusYFP signal within the nigrostriatal pathway, including cell bodies in the substantia nigra and synaptic accumulation in striatal terminals, suggestive of in vivo alpha-synuclein oligomers formation. Transduced rats showed alpha-synuclein induced dopaminergic neuron loss in the substantia nigra, the appearance of dystrophic neurites, and gliosis in the striatum. Moreover, we have applied in vivo imaging techniques in the living mouse to directly image alpha-synuclein oligomers in the cortex. Conclusion We have developed a unique animal model that provides a tool for the Parkinson’s disease research community with which to directly detect alpha- synuclein oligomers in vivo and screen therapeutic approaches targeting alpha-synuclein oligomers. PMID:24252244

  20. Supramolecular substitution reactions between hydrazide-based molecular duplex strands: complexation induced nonsymmetry and dynamic behavior.

    PubMed

    Yang, Yong; Xiang, Jun-Feng; Xue, Min; Hu, Hai-Yu; Chen, Chuan-Feng

    2008-08-15

    Supramolecular substitution reactions between hydrazide-based oligomers 1a- c and 2a- c were systematically investigated. Each oligomer existed as hydrogen-bonding mediated molecular duplex strands or a polymeric zipper structure in apolar solvents. But when another oligomer with complementary hydrogen bonding sites was added, a heterodimer structure formed due to supramolecular substitution reaction driven by the formation of more hydrogen bonds, which was evidenced by NMR experiments, sometimes gel-sol transition. When a nonsymmetric oligomer and a symmetric oligomer were involved, complexation-induced nonsymmetry was observed. When two nonsymmetric oligomers were involved, two hydrogen-bonded isomers were observed in solution. Variable-temperature (1)H NMR experiments further revealed unique dynamic behavior for the individual oligomer and the complexes. When diacetyl-terminated oligomer 1c was involved, slides perpendicular to hydrogen bonds between two constituent molecules were observed, which led to complicated (1)H NMR spectra at lower temperature; otherwise, high selectivity was obtained. Combined with the results we reported previously, a detailed picture of the structure-property relationship for our hydrazide-based oligomers was depicted, which would provide guidelines for the design of hydrazide-based fine-tuning functional materials.

  1. Memantine rescues transient cognitive impairment caused by high-molecular-weight aβ oligomers but not the persistent impairment induced by low-molecular-weight oligomers.

    PubMed

    Figueiredo, Cláudia P; Clarke, Julia R; Ledo, José Henrique; Ribeiro, Felipe C; Costa, Carine V; Melo, Helen M; Mota-Sales, Axa P; Saraiva, Leonardo M; Klein, William L; Sebollela, Adriano; De Felice, Fernanda G; Ferreira, Sergio T

    2013-06-05

    Brain accumulation of soluble amyloid-β oligomers (AβOs) has been implicated in synapse failure and cognitive impairment in Alzheimer's disease (AD). However, whether and how oligomers of different sizes induce synapse dysfunction is a matter of controversy. Here, we report that low-molecular-weight (LMW) and high-molecular-weight (HMW) Aβ oligomers differentially impact synapses and memory. A single intracerebroventricular injection of LMW AβOs (10 pmol) induced rapid and persistent cognitive impairment in mice. On the other hand, memory deficit induced by HMW AβOs (10 pmol) was found to be reversible. While memory impairment in LMW oligomer-injected mice was associated with decreased hippocampal synaptophysin and GluN2B immunoreactivities, synaptic pathology was not detected in the hippocampi of HMW oligomer-injected mice. On the other hand, HMW oligomers, but not LMW oligomers, induced oxidative stress in hippocampal neurons. Memantine rescued both neuronal oxidative stress and the transient memory impairment caused by HMW oligomers, but did not prevent the persistent cognitive deficit induced by LMW oligomers. Results establish that different Aβ oligomer assemblies act in an orchestrated manner, inducing different pathologies and leading to synapse dysfunction. Furthermore, results suggest a mechanistic explanation for the limited efficacy of memantine in preventing memory loss in AD.

  2. 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.

  3. 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

  4. Effects of several quinones on insulin aggregation.

    PubMed

    Gong, Hao; He, Zihao; Peng, Anlin; Zhang, Xin; Cheng, Biao; Sun, Yue; Zheng, Ling; Huang, Kun

    2014-07-10

    Protein misfolding and aggregation are associated with more than twenty diseases, such as neurodegenerative diseases and metabolic diseases. The amyloid oligomers and fibrils may induce cell membrane disruption and lead to cell apoptosis. A great number of studies have focused on discovery of amyloid inhibitors which may prevent or treat amyloidosis diseases. Polyphenols have been extensively studied as a class of amyloid inhibitors, with several polyphenols under clinical trials as anti-neurodegenerative drugs. As oxidative intermediates of natural polyphenols, quinones widely exist in medicinal plants or food. In this study, we used insulin as an amyloid model to test the anti-amyloid effects of four simple quinones and four natural anthraquinone derivatives from rhubarb, a traditional herbal medicine used for treating Alzheimer's disease. Our results demonstrated that all eight quinones show inhibitory effects to different extent on insulin oligomerization, especially for 1,4-benzoquinone and 1,4-naphthoquinone. Significantly attenuated oligomerization, reduced amount of amyloid fibrils and reduced hemolysis levels were found after quinones treatments, indicating quinones may inhibit insulin from forming toxic oligomeric species. The results suggest a potential action of native anthraquinone derivatives in preventing protein misfolding diseases, the quinone skeleton may thus be further explored for designing effective anti-amyloidosis compounds.

  5. Electronic coherence dynamics in trans-polyacetylene oligomers.

    PubMed

    Franco, Ignacio; Brumer, Paul

    2012-04-14

    Electronic coherence dynamics in trans-polyacetylene oligomers are considered by explicitly computing the time dependent molecular polarization from the coupled dynamics of electronic and vibrational degrees of freedom in a mean-field mixed quantum-classical approximation. The oligomers are described by the Su-Schrieffer-Heeger Hamiltonian and the effect of decoherence is incorporated by propagating an ensemble of quantum-classical trajectories with initial conditions obtained by sampling the Wigner distribution of the nuclear degrees of freedom. The electronic coherence of superpositions between the ground and excited and between pairs of excited states is examined for chains of different length, and the dynamics is discussed in terms of the nuclear overlap function that appears in the off-diagonal elements of the electronic reduced density matrix. For long oligomers the loss of coherence occurs in tens of femtoseconds. This time scale is determined by the decay of population into other electronic states through vibronic interactions, and is relatively insensitive to the type and class of superposition considered. By contrast, for smaller oligomers the decoherence time scale depends strongly on the initially selected superposition, with superpositions that can decay as fast as 50 fs and as slow as 250 fs. The long-lived superpositions are such that little population is transferred to other electronic states and for which the vibronic dynamics is relatively harmonic.

  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. Imide Oligomers Containing Pendent and Terminal Phenylethynyl Groups-2

    NASA Technical Reports Server (NTRS)

    Connell, J. W.; Smith, J. G., Jr.; Hergenrother, P. M.

    1998-01-01

    As part of a program to develop high-performance/high-temperature structural resins for aeronautical applications, imide oligomers containing pendent and terminal phenylethynyl groups were prepared, characterized and the cured resins evaluated as composite matrices. The oligomers were prepared at a calculated number-average molecular weight of 5000 g/mol and contained 15-20 mol% pendent phenylethynyl groups. In previous work, an oligomer containing pendent and terminal phenylethynyl groups exhibited a high glass transition temperature (approximately 313 C), and laminates therefrom exhibited high compressive properties, but processability, fracture toughness, microcrack resistance and damage tolerance were less than desired. In an attempt to improve these deficiencies, modifications in the oligomeric backbone involving the incorporation of 1,3-bis(3-aminophenoxy)benzene were investigated as a means of improving processability and toughness without detracting from the high glass transition temperature and high compressive properties. The amide acid oligomeric solutions were prepared in N-methyl-2-pyrrolidinone and were subsequently processed into imide powder, thin films, adhesive tape and carbon fiber prepreg. Neat resin plaques were fabricated from imide powder by compression moulding. The maximum processing pressure was 1.4 MPa and the cure temperature ranged from 350 to 371 C for 1 h for the mouldings, adhesives, films and composites. The properties of the 1,3-bis(3-aniinophenoxy)benzene modified cured imide oligomers containing pendent and terminal phenylethynyl groups are compared with those of previously prepared oligomers containing pendent and terminal phenylethynyl groups of similar composition and molecular weight.

  8. Effects of dilute acid pretreatment conditions on enzymatic hydrolysis monomer and oligomer sugar yields for aspen, balsam, and switchgrass.

    PubMed

    Jensen, Jill R; Morinelly, Juan E; Gossen, Kelsey R; Brodeur-Campbell, Michael J; Shonnard, David R

    2010-04-01

    The effects of dilute acid hydrolysis conditions were investigated on total sugar (glucose and xylose) yields after enzymatic hydrolysis with additional analyses on glucose and xylose monomer and oligomer yields from the individual hydrolysis steps for aspen (a hardwood), balsam (a softwood), and switchgrass (a herbaceous energy crop). The results of this study, in the form of measured versus theoretical yields and a severity analysis, show that for aspen and balsam, high dilute acid hydrolysis xylose yields were obtainable at all acid concentrations (0.25-0.75 wt.%) and temperatures (150-175 degrees C) studied as long as reaction time was optimized. Switchgrass shows a relatively stronger dependence on dilute acid hydrolysis acid concentration due to its higher neutralizing mineral content. Maximum total sugar (xylose and glucose; monomer plus oligomer) yields post-enzymatic hydrolysis for aspen, balsam, and switchgrass, were 88.3%, 21.2%, and 97.6%, respectively. In general, highest yields of total sugars (xylose and glucose; monomer plus oligomer) were achieved at combined severity parameter values (log CS) between 2.20 and 2.40 for the biomass species studied.

  9. Chemo-enzymatic synthesis of glycosylated insulin using a GlcNAc tag.

    PubMed

    Tomabechi, Yusuke; Suzuki, Rena; Haneda, Katsuji; Inazu, Toshiyuki

    2010-02-01

    Artificial insulin with an N-linked oligosaccharide was synthesized by a chemo-enzymatic method using endo-beta-N-acetylglucosaminidase from Mucor hiemalis (Endo-M). GlcNAc-modified insulin was prepared by the reaction of the carboxymethyl glycoside of GlcNAc and 3 amino groups of bovine insulin using a dimethylphosphinothioic mixed anhydride (Mpt-MA) method. A transglycosylation reaction of the GlcNAc-modified insulin using Endo-M gave mono-transglycosylated insulin predominantly. We determined the transglycosylation site of the mono-transglycosylated insulin.

  10. Capping of aβ42 oligomers by small molecule inhibitors.

    PubMed

    Fu, Ziao; Aucoin, Darryl; Ahmed, Mahiuddin; Ziliox, Martine; Van Nostrand, William E; Smith, Steven O

    2014-12-23

    Aβ42 peptides associate into soluble oligomers and protofibrils in the process of forming the amyloid fibrils associated with Alzheimer's disease. The oligomers have been reported to be more toxic to neurons than fibrils, and have been targeted by a wide range of small molecule and peptide inhibitors. With single touch atomic force microscopy (AFM), we show that monomeric Aβ42 forms two distinct types of oligomers, low molecular weight (MW) oligomers with heights of 1-2 nm and high MW oligomers with heights of 3-5 nm. In both cases, the oligomers are disc-shaped with diameters of ~10-15 nm. The similar diameters suggest that the low MW species stack to form the high MW oligomers. The ability of Aβ42 inhibitors to interact with these oligomers is probed using atomic force microscopy and NMR spectroscopy. We show that curcumin and resveratrol bind to the N-terminus (residues 5-20) of Aβ42 monomers and cap the height of the oligomers that are formed at 1-2 nm. A second class of inhibitors, which includes sulindac sulfide and indomethacin, exhibit very weak interactions across the Aβ42 sequence and do not block the formation of the high MW oligomers. The correlation between N-terminal interactions and capping of the height of the Aβ oligomers provides insights into the mechanism of inhibition and the pathway of Aβ aggregation.

  11. Insulin use in NIDDM.

    PubMed

    Genuth, S

    1990-12-01

    The effects of insulin treatment on the pathophysiology of non-insulin-dependent diabetes mellitus (NIDDM) are reviewed herein. Short-term studies indicate variable and partial reduction in excessive hepatic glucose output, decrease in insulin resistance, and enhancement of beta-cell function. These beneficial actions may be due to a decrease in secondary glucose toxicity rather than a direct attack on the primary abnormality. Insulin should be used as initial treatment of new-onset NIDDM in the presence of ketosis, significant diabetes-induced weight loss (despite residual obesity), and severe hyperglycemic symptoms. In diet-failure patients, prospective randomized studies comparing insulin to sulfonylurea treatment show approximately equal glycemic outcomes or a slight advantage to insulin. A key goal of insulin therapy is to normalize the fasting plasma glucose level. In contrast to the conventional use of morning injections of intermediate- and long-acting insulin, preliminary studies suggest potential advantages of administering the same insulins only at bedtime. Obese patients may require several hundred units of insulin daily and still not achieve satisfactory control. In some, addition of a sulfonylurea to insulin may reduce hyperglycemia, the insulin dose, or both. However, long-term benefits from such combination therapy remain to be demonstrated conclusively. Established adverse effects of insulin treatment in NIDDM are hypoglycemia, particularly in the elderly, and weight gain. Self-monitoring of blood glucose can identify patients in whom excessive weight gain is caused by subtle hypoglycemia. Whether insulin causes weight gain by direct effects on appetite or energy utilization remains controversial. A potential adverse effect of insulin has been suggested by epidemiological studies showing associations between hyperinsulinemia or insulin resistance and increased risk for coronary artery disease, stroke, and hypertension. Although potential mechanisms

  12. Human insulin genome sequence map, biochemical structure of insulin for recombinant DNA insulin.

    PubMed

    Chakraborty, Chiranjib; Mungantiwar, Ashish A

    2003-08-01

    Insulin is a essential molecule for type I diabetes that is marketed by very few companies. It is the first molecule, which was made by recombinant technology; but the commercialization process is very difficult. Knowledge about biochemical structure of insulin and human insulin genome sequence map is pivotal to large scale manufacturing of recombinant DNA Insulin. This paper reviews human insulin genome sequence map, the amino acid sequence of porcine insulin, crystal structure of porcine insulin, insulin monomer, aggregation surfaces of insulin, conformational variation in the insulin monomer, insulin X-ray structures for recombinant DNA technology in the synthesis of human insulin in Escherichia coli.

  13. Inherent insulin sensitivity is a major determinant of multimeric adiponectin responsiveness to short-term weight loss in extreme obesity.

    PubMed

    Mai, Stefania; Walker, Gillian E; Brunani, Amelia; Guzzaloni, Gabriele; Grossi, Glenda; Oldani, Alberto; Aimaretti, Gianluca; Scacchi, Massimo; Marzullo, Paolo

    2014-07-24

    High molecular weight (HMW-A) adiponectin levels mirror alterations in glucose homeostasis better than medium (MMW-A) and low molecular weight (LMW-A) components. In 25 patients with wide-range extreme obesity (BMI 40-77 kg/m(2)), we aimed to explore if improvements of multimeric adiponectin following 4-wk weight loss reflect baseline OGTT-derived insulin sensitivity (ISIOGTT) and disposition index (DIOGTT). Compared to 40 lean controls, adiponectin oligomers were lower in extreme obesity (p < 0.001) and, within this group, HMW-A levels were higher in insulin-sensitive (p < 0.05) than -resistant patients. In obese patients, short-term weight loss did not change total adiponectin levels and insulin resistance, while the distribution pattern of adiponectin oligomers changed due to significant increment of HMW-A (p < 0.01) and reduction of MMW-A (p < 0.05). By multivariate analysis, final HMW-A levels were significantly related to baseline ISIOGTT and final body weight (adjusted R(2) = 0.41). Our data suggest that HMW adiponectin may reflect baseline insulin sensitivity appropriately in the context of extreme obesity. Especially, we documented that HMW-A is promptly responsive to short-term weight loss prior to changes in insulin resistance, by a magnitude that is proportioned to whole body insulin sensitivity. This may suggest an insulin sensitivity-dependent control operated by HMW-A on metabolic dynamics of patients with extreme obesity.

  14. Alzheimer's therapeutics targeting amyloid beta 1-42 oligomers II: Sigma-2/PGRMC1 receptors mediate Abeta 42 oligomer binding and synaptotoxicity.

    PubMed

    Izzo, Nicholas J; Xu, Jinbin; Zeng, Chenbo; Kirk, Molly J; Mozzoni, Kelsie; Silky, Colleen; Rehak, Courtney; Yurko, Raymond; Look, Gary; Rishton, Gilbert; Safferstein, Hank; Cruchaga, Carlos; Goate, Alison; Cahill, Michael A; Arancio, Ottavio; Mach, Robert H; Craven, Rolf; Head, Elizabeth; LeVine, Harry; Spires-Jones, Tara L; Catalano, Susan M

    2014-01-01

    Amyloid beta (Abeta) 1-42 oligomers accumulate in brains of patients with Mild Cognitive Impairment (MCI) and disrupt synaptic plasticity processes that underlie memory formation. Synaptic binding of Abeta oligomers to several putative receptor proteins is reported to inhibit long-term potentiation, affect membrane trafficking and induce reversible spine loss in neurons, leading to impaired cognitive performance and ultimately to anterograde amnesia in the early stages of Alzheimer's disease (AD). We have identified a receptor not previously associated with AD that mediates the binding of Abeta oligomers to neurons, and describe novel therapeutic antagonists of this receptor capable of blocking Abeta toxic effects on synapses in vitro and cognitive deficits in vivo. Knockdown of sigma-2/PGRMC1 (progesterone receptor membrane component 1) protein expression in vitro using siRNA results in a highly correlated reduction in binding of exogenous Abeta oligomers to neurons of more than 90%. Expression of sigma-2/PGRMC1 is upregulated in vitro by treatment with Abeta oligomers, and is dysregulated in Alzheimer's disease patients' brain compared to age-matched, normal individuals. Specific, high affinity small molecule receptor antagonists and antibodies raised against specific regions on this receptor can displace synthetic Abeta oligomer binding to synaptic puncta in vitro and displace endogenous human AD patient oligomers from brain tissue sections in a dose-dependent manner. These receptor antagonists prevent and reverse the effects of Abeta oligomers on membrane trafficking and synapse loss in vitro and cognitive deficits in AD mouse models. These findings suggest sigma-2/PGRMC1 receptors mediate saturable oligomer binding to synaptic puncta on neurons and that brain penetrant, small molecules can displace endogenous and synthetic oligomers and improve cognitive deficits in AD models. We propose that sigma-2/PGRMC1 is a key mediator of the pathological effects of

  15. Anticoagulant flavonoid oligomers from the rhizomes of Alpinia platychilus.

    PubMed

    Shen, Chuan-Pu; Luo, Jian-Guang; Yang, Ming-Hua; Kong, Ling-Yi

    2015-10-01

    Two pairs of enantiomers of flavonoid oligomers (1a and 1b, 2a and 2b) along with one known chalcone (3) were isolated from the rhizomes of Alpinia platychilus. Their structures were elucidated on the basis of spectroscopic data (MS and 1D/2D NMR). The absolute configurations of the flavonoid oligomers were established by their ECD spectra. Separation of the enantiomeric mixtures (1a and 1b, 2a and 2b) was achieved on a chiral column using hexane:isopropyl alcohol:ethanol (7:2:1) as eluents. The anticoagulant assay showed that 2a, 2b and 3 exhibited potent activities to prolong the prothrombin times (PT) and the thrombin times (TT).

  16. 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.

  17. Phase behavior of a lattice hydrophobic oligomer in explicit water.

    PubMed

    Romero-Vargas Castrillón, Santiago; Matysiak, Silvina; Stillinger, Frank H; Rossky, Peter J; Debenedetti, Pablo G

    2012-08-09

    We investigate the thermodynamics of hydrophobic oligomer collapse using a water-explicit, three-dimensional lattice model. The model captures several aspects of protein thermodynamics, including the emergence of cold- and thermal-unfolding, as well as unfolding at high solvent density (a phenomenon akin to pressure-induced denaturation). We show that over a range of conditions spanning a ≈14% increase in solvent density, the oligomer transforms into a compact, strongly water-penetrated conformation at low temperature. This contrasts with thermal unfolding at high temperature, where the system "denatures" into an extended random coil conformation. We report a phase diagram for hydrophobic collapse that correctly captures qualitative aspects of cold and thermal unfolding at low to intermediate solvent densities.

  18. Diabetes and Insulin

    MedlinePlus

    ... you have. There are three main types of diabetes: • Type 1 occurs when the pancreas stops making insulin. It ... but may occur later in life. People with type 1 diabetes need insulin to survive. Treatment includes changes in ...

  19. Insulin pump (image)

    MedlinePlus

    The catheter at the end of the insulin pump is inserted through a needle into the abdominal ... with diabetes. Dosage instructions are entered into the pump's small computer and the appropriate amount of insulin ...

  20. 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.

  1. Characterization of reducible peptide oligomers as carriers for gene delivery.

    PubMed

    Kiselev, Anton; Egorova, Anna; Laukkanen, Antti; Baranov, Vladislav; Urtti, Arto

    2013-01-30

    The stability of DNA-polyplexes and intracellular DNA release are important features of gene delivery systems. To study these features, we have evaluated reducible cysteine-flanked linear lysine and arginine-rich peptides, modified with histidine residues. The reducible disulfide bonds in cysteine flanked peptides and histidine residues should augment DNA release from the peptide-DNA complexes upon disintegration of the reducible bonds. Template polymerization and oxidative polycondensation were applied to obtain peptide oligomers used for DNA-polyplex preparation. The peptides and DNA-peptide complexes were investigated with physical, chemical and transfection measurements. Physicochemical and transfection properties of DNA-polyplexes depended on the amino acid sequence of the peptidic polymers and type of the polymerization. MALDI-TOF analysis of oxidatively polycondensed products revealed several forms of peptide oligomers corresponding to 5-8 amino acid monomers. DNA-peptide particles based on template-polymerized complexes were more resistant to relaxation by negatively charged heparan sulfate than polyplexes formed with oxidatively condensed peptides. Complexes of DNA with the polycations prepared by oxidative polycondensation exhibited a 100-1000-fold higher level of gene expression compared to DNA/template-polymerized peptide complexes. The most efficient transgene expression was shown with arginine-rich polyplexes. Transfection efficacy of the arginine-rich polyplexes was even 10-fold better than that of DNA/PEI complexes. On average, polyplexes based on cysteine-flanked peptide oligomers showed lower cytotoxicity than non-reducible high molecular weight polylysine/DNA particles. We conclude that reducible peptide oligomers provide efficient DNA transfection and have the potential as vehicles for gene delivery.

  2. Differential behaviors of tea catechins under thermal processing: Formation of non-enzymatic oligomers.

    PubMed

    Fan, Fang-Yuan; Shi, Meng; Nie, Ying; Zhao, Yue; Ye, Jian-Hui; Liang, Yue-Rong

    2016-04-01

    Tea catechins as a member of flavan-3-ols subclass with the same skeleton may behave differentially. This study investigated the chemical conversions of 8 catechins under heat treatment with the involvement of epimerization, hydrolysis and oxidation/condensation reactions. Three reactions were enhanced as temperature increased from 30 °C to 90 °C. The epimerization of non-gallated catechins was favored by epi-configuration but hindered by pyrogallol moiety, and the hydrolysis reaction of gallated catechins was facilitated by pyrogallol moiety. Epicatechin and epigallocatechin had the lowest thermostabilities due to epimerization and oxidation/condensation reactions respectively. Sufficient O2 was not a precondition for the occurrence of chemical conversions of catechins under heat treatment. Non-enzymatic oligomerization occurred to epi type catechins and catechin under heat treatment, and dehydrodicatechins A were mainly responsible for the browning of epicatechin and catechin solutions. The evidence of generation of catechin oligomers provides a novel way to explain sensory change of tea and relevant products during thermal processing.

  3. Molecular modeling of crystalline alkylthiophene oligomers and polymers.

    PubMed

    Moreno, Margherita; Casalegno, Mosè; Raos, Guido; Meille, Stefano V; Po, Riccardo

    2010-02-04

    We present the results of a thorough molecular modeling study of several alkylthiophene-based oligomers and polymers. In particular, we consider two polymers whose limit-ordered crystal structures have been recently reported by our group, on the basis of powder X-ray data analysis: poly(3-(S)-2-methylbutylthiophene) (P3MBT) and form I' of poly(3-butylthiophene) (P3BT). We first describe the development of a series general purpose force fields for the simulation of these and related systems. The force fields incorporate the results of ab initio calculations of the bond torsion energies of selected oligomers and differ in the set of atomic charges used to represent the electrostatic interactions. We then present the results of an extensive validation of these force fields, by means of molecular mechanics (MM) energy minimizations and molecular dynamics (MD) simulations of the crystal structures of these oligomers and polymers. While our "best" force field does not outperform the others on each of the investigated systems, it provides a balanced description of their overall structure and energetics. Finally, our MM minimizations and MD simulations confirm that the reported crystal structures of P3MBT and P3BT are stable and correspond to well-defined energetic minima. The room-temperature MD simulations reveal a certain degree of side-chain disorder, even in our virtually defect-free polymer crystal models.

  4. α-Synuclein oligomers and clinical implications for Parkinson disease.

    PubMed

    Kalia, Lorraine V; Kalia, Suneil K; McLean, Pamela J; Lozano, Andres M; Lang, Anthony E

    2013-02-01

    Protein aggregation within the central nervous system has been recognized as a defining feature of neurodegenerative diseases since the early 20th century. Since that time, there has been a growing list of neurodegenerative disorders, including Parkinson disease, which are characterized by inclusions of specific pathogenic proteins. This has led to the long-held dogma that these characteristic protein inclusions, which are composed of large insoluble fibrillar protein aggregates and visible by light microscopy, are responsible for cell death in these diseases. However, the correlation between protein inclusion formation and cytotoxicity is inconsistent, suggesting that another form of the pathogenic proteins may be contributing to neurodegeneration. There is emerging evidence implicating soluble oligomers, smaller protein aggregates not detectable by conventional microscopy, as potential culprits in the pathogenesis of neurodegenerative diseases. The protein α-synuclein is well recognized to contribute to the pathogenesis of Parkinson disease and is the major component of Lewy bodies and Lewy neurites. However, α-synuclein also forms oligomeric species, with certain conformations being toxic to cells. The mechanisms by which these α-synuclein oligomers cause cell death are being actively investigated, as they may provide new strategies for diagnosis and treatment of Parkinson disease and related disorders. Here we review the possible role of α-synuclein oligomers in cell death in Parkinson disease and discuss the potential clinical implications.

  5. 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.

  6. 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

  7. Size-dependent neurotoxicity of beta-amyloid oligomers.

    PubMed

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

    2010-04-15

    The link between the size of soluble amyloid beta (Abeta) oligomers and their toxicity to rat cerebellar granule cells (CGC) was investigated. Variation in conditions during in vitro oligomerization of Abeta(1-42) resulted in peptide assemblies with different particle size as measured by atomic force microscopy and confirmed by dynamic light scattering and fluorescence correlation spectroscopy. Small oligomers of Abeta(1-42) with a mean particle z-height of 1-2 nm exhibited propensity to bind to 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. A similar neurotoxic pattern was also observed in primary cultures of cortex neurons whereas Abeta(1-42) oligomers, monomers and fibrils were non-toxic to glial cells in CGC cultures or macrophage J774 cells. However, both oligomeric forms of Abeta(1-42) induced reduction of neuronal cell densities in the CGC cultures.

  8. 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.

  9. Optimized Ultrasonic Irradiation Finds Out Ultrastable Aβ1-40 Oligomers.

    PubMed

    Nakajima, Kichitaro; So, Masatomo; Takahashi, Kazuma; Tagawa, Yoh-Ichi; Hirao, Masahiko; Goto, Yuji; Ogi, Hirotsugu

    2017-03-16

    Oligomer species of amyloid β (Aβ) peptides are intensively investigated because of their relevance to Alzheimer's disease (AD), and a stable oligomer will be a cause of AD. In this article, we investigate the structural stability of two representative Aβ1-40 oligomers, which are with and without the β-sheet structure, denoted by β and non-β oligomers, respectively, using optimized ultrasonic irradiation (OUI). Recent studies reveal that OUI significantly accelerates the fibril formation in Aβ1-40 monomers; it is capable of transforming any unstable oligomers into fibrils (the dead-end products) in a short time. First, we find that β oligomers can be produced under high-speed stirring agitation; their β-sheet structures are evaluated by the circular-dichroism spectrum measurement, by the immunoassay using the fibril-specific OC antibody, and by the seeding experiment, showing identical characteristics to those formed in previous reports. Second, we form non-β oligomers in a high-concentration NaCl solution and confirm that they include no β-sheet structure, and they are recognized by the oligomer-specific A11 antibody. Furthermore, we confirm the neurotoxicity of the two types of oligomers using the neural tissue derived from mouse embryonic stem cells. We apply the OUI agitation to the β and non-β oligomers. The non-β oligomers are transformed into the fibrils, indicating that they are intermediate species in the fibrillation pathway. However, the β oligomers are surprisingly unaffected by OUI, indicating their high thermodynamic stability. We conclude that the β oligomers should be the independent dead-end products of another pathway, different from the fibrillation pathway.

  10. 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.

  11. All about Insulin Resistance

    MedlinePlus

    Toolkit No. 2 All About Insulin Resistance Insulin resistance is a condition that raises your risk for type 2 diabetes and heart disease. ... Diabetes Association, Inc. 1/15 Toolkit No. 2: All About Insulin Resistance continued J Order the smallest ...

  12. SYNTHESIS OF THE FULLY PROTECTED PHOSPHORAMIDITE OF THE BENZENE-DNA ADDUCT, N2- (4-HYDROXYPHENYL)-2'-DEOXYGUANOSINE AND INCORPORATION OF THE LATER INTO DNA OLIGOMERS

    SciTech Connect

    Chenna, Ahmed; Gupta, Ramesh C.; Bonala, Radha R.; Johnson, Francis; Huang, Bo

    2008-06-09

    N2-(4-Hydroxyphenyl)-2'-deoxyguanosine-5'-O-DMT-3'-phosphoramidite has been synthesized and used to incorporate the N2-(4-hydroxyphenyl)-2'-dG (N2-4-HOPh-dG) into DNA, using solid-state synthesis technology. The key step to obtaining the xenonucleoside is a palladium (Xantphos-chelated) catalyzed N2-arylation (Buchwald-Hartwig reaction) of a fully protected 2'-deoxyguanosine derivative by 4-isobutyryloxybromobenzene. The reaction proceeded in good yield and the adduct was converted to the required 5'-O-DMT-3'-O-phosphoramidite by standard methods. The latter was used to synthesize oligodeoxynucleotides in which the N2-4-HOPh-dG adduct was incorporated site-specifically. The oligomers were purified by reverse-phase HPLC. Enzymatic hydrolysis and HPLC analysis confirmed the presence of this adduct in the oligomers.

  13. Real-time polymerase chain reaction, in situ hybridization and immunohistochemical localization of insulin-like growth factor-I and myostatin during development of Dicentrarchus labrax (Pisces: Osteichthyes).

    PubMed

    Patruno, Marco; Sivieri, Susanna; Poltronieri, Carlo; Sacchetto, Roberta; Maccatrozzo, Lisa; Martinello, Tiziana; Funkenstein, Bruria; Radaelli, Giuseppe

    2008-03-01

    The distribution of insulin-like growth factor-I (IGF-I) and myostatin (MSTN) was investigated in sea bass (Dicentrarchus labrax) by real-time polymerase chain reaction (PCR), in situ hybridization (ISH) and immunohistochemistry. Real-time PCR indicated that IGF-I mRNA increased from the second day post-hatching and that this trend became significant from day 4. ISH confirmed a strong IGF-I mRNA expression from the first week post-hatching, with the most abundant expression being detected in the liver of larvae and adults. Real-time PCR also showed that the level of MSTN mRNA increased significantly from day 25. The expression of MSTN mRNA was higher in muscle and almost absent in other anatomical regions in both larvae and adults. Interestingly, the lateral muscle showed a quantitative differential expression of IGF-I and MSTN mRNAs in red and white muscle, depending on the developmental stage examined. IGF-I immunoreactivity was detected in developing intestine at hatching and in skeletal muscle, skin and yolk sac. MSTN immunostaining was evident in several tissues and organs in both larvae and adults. Both IGF-I and MSTN proteins were detected in the liver from day 4 post-hatching and, subsequently, in the kidney and heart muscle from day 10. Our results suggest, on the basis of a combined methodological approach, that IGF-I and MSTN are involved in the regulation of somatic growth in the sea bass.

  14. 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}.

  15. Oral Insulin Reloaded

    PubMed Central

    Heinemann, Lutz; Plum-Mörschel, Leona

    2014-01-01

    Optimal coverage of insulin needs is the paramount aim of insulin replacement therapy in patients with diabetes mellitus. To apply insulin without breaking the skin barrier by a needle and/or to allow a more physiological provision of insulin are the main reasons triggering the continuous search for alternative routes of insulin administration. Despite numerous attempts over the past 9 decades to develop an insulin pill, no insulin for oral dosing is commercially available. By way of a structured approach, we aim to provide a systematic update on the most recent developments toward an orally available insulin formulation with a clear focus on data from clinical-experimental and clinical studies. Thirteen companies that claim to be working on oral insulin formulations were identified. However, only 6 of these companies published new clinical trial results within the past 5 years. Interestingly, these clinical data reports make up a mere 4% of the considerably high total number of publications on the development of oral insulin formulations within this time period. While this picture clearly reflects the rising research interest in orally bioavailable insulin formulations, it also highlights the fact that the lion’s share of research efforts is still allocated to the preclinical stages. PMID:24876606

  16. The colorimetric determination of selectively cleaved adenosines and guanosines in DNA oligomers using bicinchoninic acid and copper.

    PubMed

    Thomas, Elizabeth M; Testa, Stephen M

    2017-01-01

    Colorimetric methods combined with color-changing chemical probes are widely used as simple yet effective tools for identifying and quantifying a wide variety of molecules in solution. For nucleic acids (DNA and RNA), perhaps the most commonly used colorimetric probe is potassium permanganate, which can be used to identify single-stranded pyrimidines (thymine and cytosine) in polymers. Unfortunately, permanganate is not an effective probe for identifying purines (adenine and guanine), especially in the presence of the more reactive pyrimidines. Therefore, robust methods for discriminating between the purines remain elusive, thereby creating a barrier toward developing more complex colorimetric applications. In this proof-of-principle study, we demonstrate that bicinchoninic acid (BCA) and copper, when combined with purine-specific chemical cleavage reactions, can be a colorimetric probe for the identification and quantification of adenosines and/or guanosines in single-stranded DNA oligomers, even in the presence of pyrimidines. Furthermore, the reactions are stoichiometric, which allows for the quantification of the number of adenosines and/or guanosines in these oligomers. Because the BCA/copper reagent detects the reducing sugar, 2-deoxyribose, that results from the chemical cleavage of a given nucleotide's N-glycosidic bond, these colorimetric assays are effectively detecting apurinic sites in DNA oligomers, which are known to occur via DNA damage in biological systems. We demonstrate that simple digital analysis of the color-changing chromophore (BCA/copper) is all that is necessary to obtain quantifiable and reproducible data, which indicates that these assays should be broadly accessible.

  17. Inhaled human insulin.

    PubMed

    Strack, Thomas R

    2006-04-01

    The benefit of subcutaneous insulin therapy in patients with diabetes is frequently limited due to difficulty in convincing patients of the importance of multiple daily insulin injections to cope effectively with meal-associated glycemic changes. Thus, the aim of achieving tight glycemic control, which is critical for reducing the risk of long-term diabetes-related complications, frequently remains elusive. The successful development of an inhalable insulin as a noninvasive alternative promises to change the management of diabetes. The first product to become available to patients is inhaled human insulin, a dry-powder formulation packaged into discrete blisters containing 1 or 3 mg of dry-powder human insulin and administered via a unique pulmonary inhaler device. It has recently been approved in both the United States and the European Union for the control of hyperglycemia in adult patients with type 1 or type 2 diabetes. The pharmacokinetic profile of inhaled human insulin closely mimics the natural pattern of insulin secretion, and resembles that of rapid-acting subcutaneous analogs. Similarly to rapid-acting subcutaneous analogs, inhaled human insulin has a more rapid onset of glucose-lowering activity compared to subcutaneous regular insulin, allowing it to be administered shortly before meals. It has a duration of glucose-lowering activity comparable to subcutaneous regular insulin and longer than rapid-acting insulin analogs. Inhaled human insulin effectively controls postprandial glucose concentrations in patients with type 1 or type 2 diabetes without increasing the risk of hypoglycemia, and even improves fasting glucose levels compared to subcutaneous insulin. Inhaled human insulin has an overall favorable safety profile. There are small reductions in lung function (1-1.5% of total lung forced expiratory volume in the first second [FEV1] capacity) after onset of treatment that are reversible in most patients if treatment is discontinued. Inhaled human

  18. Adiponectin profile and Irisin expression in Italian obese children: Association with insulin-resistance.

    PubMed

    Nigro, Ersilia; Scudiero, Olga; Ludovica Monaco, Maria; Polito, Rita; Schettino, Pietro; Grandone, Anna; Perrone, Laura; Miraglia Del Giudice, Emanuele; Daniele, Aurora

    2017-04-03

    Adiponectin (Acrp30), its high molecular weight (HMW) oligomers, and Irisin are molecules involved in several metabolic processes. To investigate if these cytokines could represent new metabolic markers, we evaluated the expression of Acrp30 and Irisin in serum of obese children from South Italy affected by different degrees of insulin resistance (IR). The anthropometric and metabolic features were evaluated in 27 obese children versus 13 age-matched controls. The expression of Acrp30, its pattern and Irisin were investigated by ELISA, western blotting and fast protein liquid chromatography. The HOMA index was significantly higher in obese children versus controls, and metabolic syndrome was more prevalent in obese children with elevated IR versus those with normal HOMA (38% vs 16%). Total Acrp30 and HMW oligomers were significantly lower in obese than in control children, and the difference was more pronounced in children with HOMA >3.4. In control and obese children, total Acrp30 and HMW oligomers were inversely related to HOMA (r-0.38, p 0.02; r-0.35, p 0.03). Irisin was significantly higher in obese than in control children, and was inversely correlated with Acrp30 and HMW (r-0.32, p 0.04; r-0.39, p 0.01). The inverse correlation of Acpr30 and HMW oligomers with HOMA indicates that Acpr30 is directly involved in IR status. Moreover, the inverse correlation between Irisin and Acrp30 and, more significantly, between Irisin and HMW oligomers suggests that the two cytokines are closely connected. The use of Acrp30, HMW oligomers and Irisin as predictive factors of IR in obese children remains to be further elucidated.

  19. Abiotic formation of RNA-like oligomers by montmorillonite catalysis: part II

    NASA Astrophysics Data System (ADS)

    Ertem, Gözen; Snellinger-O'Brien, Ann M.; Ertem, M. C.; Rogoff, D. A.; Dworkin, Jason P.; Johnston, Murray V.; Hazen, Robert M.

    2008-01-01

    This work is an extension of our previous studies carried out to investigate the possible catalytic role of minerals in the abiotic synthesis of biologically important molecules. In the presence of montmorillonite, a member of the phyllosilicate group minerals that are abundant on Earth and identified on Mars, activated RNA monomers, namely 5‧-phosphorimidazolides of nucleosides (ImpNs), undergo condensation reactions in aqueous electrolyte solution producing oligomers with similar structures to short RNA fragments. Analysis of the linear trimer isomers formed in the reaction of a mixture of activated adenosine and cytidine monomers (ImpA and ImpC, respectively) employing high-performance liquid chromatography, selective enzymatic hydrolysis and matrix-assisted laser desorption/ionization mass spectroscopy molecular weight measurements demonstrate that montmorillonite catalysis facilitates the formation of hetero-isomers containing 56% A- and 44% C-monomer incorporated in their structure. The results also show that 56% of the monomer units are linked together by RNA-like 3‧, 5‧-phosphodiester bonds. These results follow the same trend observed in our most recent work studying the reaction of activated adenosine and uridine monomers, and support Bernal's hypothesis proposing the possible catalytic role of minerals in the abiotic processes in the course of chemical evolution.

  20. Direct Correlation Between Ligand-Induced α-Synuclein Oligomers and Amyloid-like Fibril Growth

    PubMed Central

    Nors Perdersen, Martin; Foderà, Vito; Horvath, Istvan; van Maarschalkerweerd, Andreas; Nørgaard Toft, Katrine; Weise, Christoph; Almqvist, Fredrik; Wolf-Watz, Magnus; Wittung-Stafshede, Pernilla; Vestergaard, Bente

    2015-01-01

    Aggregation of proteins into amyloid deposits is the hallmark of several neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease. The suggestion that intermediate oligomeric species may be cytotoxic has led to intensified investigations of pre-fibrillar oligomers, which are complicated by their transient nature and low population. Here we investigate alpha-synuclein oligomers, enriched by a 2-pyridone molecule (FN075), and the conversion of oligomers into fibrils. As probed by leakage assays, the FN075 induced oligomers potently disrupt vesicles in vitro, suggesting a potential link to disease related degenerative activity. Fibrils formed in the presence and absence of FN075 are indistinguishable on microscopic and macroscopic levels. Using small angle X-ray scattering, we reveal that FN075 induced oligomers are similar, but not identical, to oligomers previously observed during alpha-synuclein fibrillation. Since the levels of FN075 induced oligomers correlate with the amounts of fibrils among different FN075:protein ratios, the oligomers appear to be on-pathway and modeling supports an ‘oligomer stacking model’ for alpha-synuclein fibril elongation. PMID:26020724

  1. 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.

  2. Low-resolution structure of a vesicle disrupting α-synuclein oligomer that accumulates during fibrillation

    PubMed Central

    Giehm, Lise; Svergun, Dmitri I.; Otzen, Daniel E.; Vestergaard, Bente

    2011-01-01

    One of the major hallmarks of Parkinson disease is aggregation of the protein α-synuclein (αSN). Aggregate cytotoxicity has been linked to an oligomeric species formed at early stages in the aggregation process. Here we follow the fibrillation process of αSN in solution over time using small angle X-ray scattering and resolve four major coexisting species in the fibrillation process, namely monomer, dimer, fibril and an oligomer. By ab initio modeling to fit the data, we obtain a low-resolution structure of a symmetrical and slender αSN fibril in solution, consisting of a repeating unit with a maximal distance of 900 Å and a diameter of ∼180 Å. The same approach shows the oligomer to be shaped like a wreath, with a central channel and with dimensions corresponding to the width of the fibril. The structure, accumulation and decay of this oligomer is consistent with an on-pathway role for the oligomer in the fibrillation process. We propose an oligomer-driven αSN fibril formation mechanism, where the fibril is built from the oligomers. The wreath-shaped structure of the oligomer highlights its potential cytotoxicity by simple membrane permeabilization. This is confirmed by the ability of the purified oligomer to disrupt liposomes. Our results provide the first structural description in solution of a potentially cytotoxic oligomer, which accumulates during the fibrillation of αSN. PMID:21300904

  3. Quantitative monitoring of dermal and inhalation exposure to 1,6-hexamethylene diisocyanate monomer and oligomers.

    PubMed

    Fent, Kenneth W; Jayaraj, Karupiah; Ball, Louise M; Nylander-French, Leena A

    2008-04-01

    Respiratory sensitization and occupational asthma are associated with exposure to 1,6-hexamethylene diisocyanate (HDI) in both monomeric and oligomeric forms. The monomer and polymers of diisocyanates differ significantly in their rates of absorption into tissue and their toxicity, and hence may differ in their contribution to sensitization. We have developed and evaluated a liquid chromatography/mass spectrometry (LC-MS) method capable of quantifying HDI and its oligomers (uretidone, biuret, and isocyanurate) in air, tape-stripped skin, and paint samples collected in the automotive refinishing industry. To generate analytical standards, urea derivatives of HDI, biuret, and isocyanurate were synthesized by reaction with 1-(2-methoxyphenyl)piperazine and purified. The urea derivatives were shown to degrade on average by less than 2% per week at -20 degrees C over a 2 month period in occupational samples. The average recovery of HDI and its oligomers from tape was 100% and the limits of detection were 2 and 8 fmol microl(-1), respectively. Exposure assessments were performed on 13 automotive spray painters to evaluate the LC-MS method and the sampling methods under field conditions. Isocyanurate was the most abundant component measured in paint tasks, with median air and skin concentrations of 2.4 mg m(-3) and 4.6 microg mm(-3), respectively. Log-transformed concentrations of HDI (r = 0.79, p < 0.0001) and of isocyanurate (r = 0.71, p < 0.0001) in the skin of workers were correlated with the log-transformed product of air concentration and painting time. The other polyisocyanates were detected on skin for less than 25% of the paint tasks. This LC-MS method provides a valuable tool to investigate inhalation and dermal exposures to specific polyisocyanates and to explore relative differences in the exposure pathways.

  4. Purification of recombinant catalase-peroxidase HPI from E. coli and its application in enzymatic polymerization reactions.

    PubMed

    Di Gennaro, Patrizia; Bargna, Anna; Bruno, Ferdinando; Sello, Guido

    2014-02-01

    In this paper, a recombinant catalase-peroxidase HPI from Escherichia coli was prepared, purified, and used in enzymatic polymerization reactions for the production of several oligomeric products. We tested the enzyme on four different substrates, chosen as representative of phenols and anilines: phenol, 3-methoxyphenol, catechol, and aniline. The polymerization reactions were followed by SEC-HPLC analysis, and except for aniline, all the other substrates were completely converted into one or more polymerization products. Results showed that reactions performed with phenol and 3-methoxyphenol allowed the isolation of some oligomers of different weight: a 27-monomeric unit oligomer and a 23-U oligomer are the heaviest ones. Experiments performed with catechol showed the formation of oligomers of 7 U in the reaction with HPI. HPI polymerization reactions performed with aniline allowed the identification of two different oligomers, one of 4 U and one of 10 U. All the substrates have been also used in reactions catalyzed by HRP in the same reaction conditions. Several products were common to the two enzymes. This work suggests the use of HPI as an alternative enzyme in peroxidatic reactions for the production of different oligomers from phenols and other compounds.

  5. Basal insulin: beyond glycemia.

    PubMed

    Niswender, Kevin D

    2011-07-01

    Insulin is a pleiotropic hormone with numerous effects at the cellular, tissue, and organismal levels. Clinicians are familiar with physiological effects of insulin on carbohydrate metabolism, including stimulation of glucose uptake in skeletal muscle and the suppression of glucose production from the liver. Other metabolic effects of insulin include inhibiting the release of free fatty acids from adipose tissue and stimulating the incorporation of amino acids into proteins. Indeed, every organ in the body, including the brain, is a target for insulin action. Insulin resistance, typically defined with respect to glucose metabolism, is a condition in which normal levels of insulin do not trigger the signal for glucose disposition. The effects of insulin resistance and impaired insulin signaling have profound pathophysiologic effects, such as hyperglycemia-induced tissue damage, hypertension, dyslipidemia, metabolic syndrome, and cardiovascular and renal disease. An integrated view of insulin action in all of these tissues may yield improved therapeutic insight and possibly even illuminate new therapeutic opportunities. With the increase in the number of patients diagnosed with prediabetes and diabetes, an updated understanding of the disease and the pharmacologic armamentarium used to treat it is needed to improve outcomes. To help expand the clinical care provider's perspective, this article will provide a provocative discussion about the pathophysiology of diabetes, the role of insulin and insulin resistance, and the clinical efficacy potential of insulin. Understanding the cellular and molecular mechanisms underlying the effects of insulin and how these translate into clinical consequences beyond glycemia will assist primary care physicians in the care of their patients with diabetes and metabolic syndrome.

  6. Electrorheology of aniline-oligomer suspensions under oscillatory shear

    NASA Astrophysics Data System (ADS)

    Mrlik, M.; Pavlinek, V.; Almajdalawi, S.; Saha, P.; Bober, P.; Stejskal, J.

    2013-02-01

    Preparation of the aniline oligomers by the oxidation of aniline with p-benzoquinone in the solutions of methanesulfonic acid (MSA) and the rheology of their suspensions in silicone oil are presented in this study. This synthesis provides particles of flake-like morphology and various conductivities depending on the molar concentration of MSA. Further, the electrorheological (ER) performance of the particles suspended in the silicone oil was measured as well as dielectric properties of suspensions. Finally, the effect of the temperature on the ER activity was investigated.

  7. Aromatic small molecules remodel toxic soluble oligomers of amyloid beta through three independent pathways.

    PubMed

    Ladiwala, Ali Reza A; Dordick, Jonathan S; Tessier, Peter M

    2011-02-04

    In protein conformational disorders ranging from Alzheimer to Parkinson disease, proteins of unrelated sequence misfold into a similar array of aggregated conformers ranging from small oligomers to large amyloid fibrils. Substantial evidence suggests that small, prefibrillar oligomers are the most toxic species, yet to what extent they can be selectively targeted and remodeled into non-toxic conformers using small molecules is poorly understood. We have evaluated the conformational specificity and remodeling pathways of a diverse panel of aromatic small molecules against mature soluble oligomers of the Aβ42 peptide associated with Alzheimer disease. We find that small molecule antagonists can be grouped into three classes, which we herein define as Class I, II, and III molecules, based on the distinct pathways they utilize to remodel soluble oligomers into multiple conformers with reduced toxicity. Class I molecules remodel soluble oligomers into large, off-pathway aggregates that are non-toxic. Moreover, Class IA molecules also remodel amyloid fibrils into the same off-pathway structures, whereas Class IB molecules fail to remodel fibrils but accelerate aggregation of freshly disaggregated Aβ. In contrast, a Class II molecule converts soluble Aβ oligomers into fibrils, but is inactive against disaggregated and fibrillar Aβ. Class III molecules disassemble soluble oligomers (as well as fibrils) into low molecular weight species that are non-toxic. Strikingly, Aβ non-toxic oligomers (which are morphologically indistinguishable from toxic soluble oligomers) are significantly more resistant to being remodeled than Aβ soluble oligomers or amyloid fibrils. Our findings reveal that relatively subtle differences in small molecule structure encipher surprisingly large differences in the pathways they employ to remodel Aβ soluble oligomers and related aggregated conformers.

  8. Biosimilar Insulin and Costs

    PubMed Central

    Heinemann, Lutz

    2015-01-01

    The costs for insulin treatment are high, and the steady increase in the number of patients with diabetes on insulin presents a true challenge to health care systems. Therefore, all measures to lower these costs are welcomed by patients, physicians, and health care providers. The market introduction of biosimilar insulins presents an option to lower treatment costs as biosimilars are usually offered at a lower price than the originator product. However, the assumption that a drastic reduction in insulin prices will take place, as was observed with many generic drugs, is most probably not realistic. As the first biosimilar insulin has now been approved in the EU, this commentary discusses a number of aspects that are relevant when it comes to the potential cost reduction we will see with the use of biosimilar insulins. PMID:26350722

  9. Adipokines and insulin action

    PubMed Central

    Knights, Alexander J; Funnell, Alister PW; Pearson, Richard CM; Crossley, Merlin; Bell-Anderson, Kim S

    2014-01-01

    Obesity is a major public health concern and a strong risk factor for insulin resistance, type 2 diabetes mellitus (T2DM), and cardiovascular disease. The last two decades have seen a reconsideration of the role of white adipose tissue (WAT) in whole body metabolism and insulin action. Adipose tissue-derived cytokines and hormones, or adipokines, are likely mediators of metabolic function and dysfunction. While several adipokines have been associated with obese and insulin-resistant phenotypes, a select group has been linked with insulin sensitivity, namely leptin, adiponectin, and more recently, adipolin. What is known about these insulin-sensitizing molecules and their effects in healthy and insulin resistant states is the subject of this review. There remains a significant amount of research to do to fully elucidate the mechanisms of action of these adipokines for development of therapeutics in metabolic disease. PMID:24719781

  10. Immunologic insulin resistance.

    PubMed

    Davidson, J K; DeBra, D W

    1978-03-01

    The efficacy of sulfated beef insulin for plasma glucose control in 35 patients with immunologic insulin resistance was studied. Patients were on a mean dose of 550 U./day (range 200--2,000) of U-500 regular beef insulin. Mean maximum 125I-insulin-binding capacity was 191 mU./ml. serum (range 13--1,080). Mean in vivo half-life (T 1/2) of 125I-regular beef insulin was 614 minutes (range 114--1,300), as against a mean T 1/2 of 13.9 minutes (range 11.8--16.5) in normal controls. Treatment was successful in 34 patients and unsuccessful in one with lipoatrophic diabetes. The mean initial dose of sulfated insulin was 89 U./day (range 15--400) and at three months was 66 U./day (range 20--400). Twenty-eight patients who responded and survived have been on sulfated insulin for a mean of 39 months (range 2-66) and are on a mean dose of 25 U./day (range 0--100). The mean maximum binding capacity fell to 9 mU./ml. (range 0--34) during therapy (p less than 0.01). Mean 125I-insulin T 1/2 fell from 614 to 249 minutes after sulfated insulin therapy (p less than 0.001). A comparative study of 15 patients on consecutive days showed a 35 sulfated insulin T 1/2 of 60 minutes (range 15--94) and a mean 125I-regular insulin T 1/2 of 246 minutes (range 62--560, p less than 0.001). These results indicate that sulfated insulin is less antigenic than regular beef insulin and combines less avidly with human antibodies to regular beef insulin. The response to sulfated insulin therapy was significantly better than the response reported by other investigators to pork insulin or to steroid therapy in similar patients.

  11. Insulin resistance and atherosclerosis

    PubMed Central

    Semenkovich, Clay F.

    2006-01-01

    Considerable evidence supports the association between insulin resistance and vascular disease, and this has led to wide acceptance of the clustering of hyperlipidemia, glucose intolerance, hypertension, and obesity as a clinical entity, the metabolic syndrome. While insulin resistance, by promoting dyslipidemia and other metabolic abnormalities, is part of the proatherogenic milieu, it is possible that insulin resistance itself in the vascular wall does not promote atherosclerosis. Recent findings suggest that insulin resistance and atherosclerosis could represent independent and ultimately maladaptive responses to the disruption of cellular homeostasis caused by the excess delivery of fuel. PMID:16823479

  12. 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.

  13. Broadband terahertz dynamics of propylene glycol monomer and oligomers

    NASA Astrophysics Data System (ADS)

    Koda, Shota; Mori, Tatsuya; Kojima, Seiji

    2016-12-01

    We investigated the broadband terahertz spectra (0.1-5.0 THz) of glass-forming liquids, propylene glycol (PG), its oligomers poly (propylene glycol)s (PPGs), and poly (propylene glycol) diglycidyl ether (PPG-de) using broadband terahertz time-domain spectroscopy and low-frequency Raman scattering. The numerical value of the dielectric loss at around 1.5 THz, which is the peak position of broad peaks in all samples, decreased as the molecular weight increased. Furthermore, the peak at around 1.5 THz is insensitive to the molecular weight. For PPGs, the side chain effect of the oligomer was observed in the terahertz region. Based on the experimental and calculation results for the PPGs and PPG-de, whose end groups are epoxy groups, the beginnings of the increases in the observed dielectric loss above 3.5 THz of the PPGs are assigned to the OH bending vibration. The higher value of the dielectric loss in the terahertz region for the PPG-de can be the tail of a broad peak located in the MHz region. The difference between the Raman susceptibility and dielectric loss reflects the difference in the observable molecular dynamics between the infrared and Raman spectroscopies.

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

    NASA Astrophysics Data System (ADS)

    Nguyen, Phuong H.; Li, Mai Suan; Derreumaux, Philippe

    2014-03-01

    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 Aβ9-40, resulting from two atomistic molecular dynamics simulations in explicit solvent, each of 200 ns, starting from two distinct structures.

  15. Lipid raft disruption protects mature neurons against amyloid oligomer toxicity.

    PubMed

    Malchiodi-Albedi, Fiorella; Contrusciere, Valentina; Raggi, Carla; Fecchi, Katia; Rainaldi, Gabriella; Paradisi, Silvia; Matteucci, Andrea; Santini, Maria Teresa; Sargiacomo, Massimo; Frank, Claudio; Gaudiano, Maria Cristina; Diociaiuti, Marco

    2010-04-01

    A specific neuronal vulnerability to amyloid protein toxicity may account for brain susceptibility to protein misfolding diseases. To investigate this issue, we compared the effects induced by oligomers from salmon calcitonin (sCTOs), a neurotoxic amyloid protein, on cells of different histogenesis: mature and immature primary hippocampal neurons, primary astrocytes, MG63 osteoblasts and NIH-3T3 fibroblasts. In mature neurons, sCTOs increased apoptosis and induced neuritic and synaptic damages similar to those caused by amyloid beta oligomers. Immature neurons and the other cell types showed no cytotoxicity. sCTOs caused cytosolic Ca(2+) rise in mature, but not in immature neurons and the other cell types. Comparison of plasma membrane lipid composition showed that mature neurons had the highest content in lipid rafts, suggesting a key role for them in neuronal vulnerability to sCTOs. Consistently, depletion in gangliosides protected against sCTO toxicity. We hypothesize that the high content in lipid rafts makes mature neurons especially vulnerable to amyloid proteins, as compared to other cell types; this may help explain why the brain is a target organ for amyloid-related diseases.

  16. 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.

  17. Amyloid oligomer structure characterization from simulations: a general method.

    PubMed

    Nguyen, Phuong H; Li, Mai Suan; Derreumaux, Philippe

    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 Aβ9-40, resulting from two atomistic molecular dynamics simulations in explicit solvent, each of 200 ns, starting from two distinct structures.

  18. Fluoroalkyl end-capped vinyltrimethoxysilane oligomer/anatase titanium oxide nanocomposites possessing photocatalytic activity even after calcination at 1000°C.

    PubMed

    Guo, Sujuan; Yoshioka, Hiroaki; Kakehi, Hiroshi; Kato, Yoshihiro; Miura, Masashi; Isu, Norifumi; Ameduri, Bruno; Sawada, Hideo

    2012-12-01

    Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [R(F)-(VM)(n)-R(F)] underwent the sol-gel reaction under alkaline conditions in the presence of anatase titanium oxide nanoparticles (an-TiO(2)) in tetrahydrofuran to give the corresponding fluorinated oligomer/anatase titanium oxide nanocomposites [R(F)-(VM-SiO(2))(n)-R(F)/an-TiO(2)]. Crystalline structure of an-TiO(2) in the nanocomposites thus obtained was found to keep completely its structure without phase transformation to rutile even after calcination at 1000°C, although crystalline structure of the original an-TiO(2) nanoparticles underwent a complete phase transformation to the rutile under similar conditions. Interestingly, R(F)-(VM-SiO(2))(n)-R(F)/an-TiO(2) nanocomposites before and after calcination at 1000°C exhibited the similar photocatalytic activity for the decolorization of methylene blue under UV light irradiation.

  19. Sedimentation studies on human amylin fail to detect low-molecular-weight oligomers.

    PubMed

    Vaiana, Sara M; Ghirlando, Rodolfo; Yau, Wai-Ming; Eaton, William A; Hofrichter, James

    2008-04-01

    Sedimentation velocity experiments show that only monomers coexist with amyloid fibrils of human islet amyloid-polypeptide. No oligomers containing <100 monomers could be detected, suggesting that the putative toxic oligomers are much larger than those found for the Alzheimer's peptide, Abeta(1-42).

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

    PubMed

    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.

  1. Seeding induced by alpha-synuclein oligomers provides evidence for spreading of alpha-synuclein pathology.

    PubMed

    Danzer, Karin M; Krebs, Simon K; Wolff, Michael; Birk, Gerald; Hengerer, Bastian

    2009-10-01

    Lewy bodies, alpha-synuclein (alpha-syn) immunopositive intracellular deposits, are the pathological hallmark of Parkinson's disease (PD). Interestingly, Lewybody-like structures have been identified in fetal tissue grafts about one decade after transplantation into the striatum of PD patients. One possible explanation for the accelerated deposition of alpha-syn in the graft is that the aggregation of alpha-syn from the host tissue to the graft is spread by a prion disease-like mechanism. We discuss here an in vitro model which might recapitulate some aspects of disease propagation in PD. We found here that in vitro-generated alpha-syn oligomers induce transmembrane seeding of alpha-syn aggregation in a dose- and time-dependent manner. This effect was observed in primary neuronal cultures as well as in neuronal cell lines. The seeding oligomers were characterized by a distinctive lithium dodecyl sulfate-stable oligomer pattern and could be generated in a dynamic process out of pore-forming oligomers. We propose that alpha-syn oligomers form as a dynamic mixture of oligomer types with different properties and that alpha-syn oligomers can be converted into different types depending on the brain milieu conditions. Our data indicate that extracellular alpha-syn oligomers can induce intracellular alpha-syn aggregation, therefore we hypothesize that a similar mechanism might lead to alpha-syn pathology propagation.

  2. Amyloid-beta oligomers increase the localization of prion protein at the cell surface.

    PubMed

    Caetano, Fabiana A; Beraldo, Flavio H; Hajj, Glaucia N M; Guimaraes, Andre L; Jürgensen, Sofia; Wasilewska-Sampaio, Ana Paula; Hirata, Pedro H F; Souza, Ivana; Machado, Cleiton F; Wong, Daisy Y-L; De Felice, Fernanda G; Ferreira, Sergio T; Prado, Vania F; Rylett, R Jane; Martins, Vilma R; Prado, Marco A M

    2011-05-01

    In Alzheimer's disease, the amyloid-β peptide (Aβ) interacts with distinct proteins at the cell surface to interfere with synaptic communication. Recent data have implicated the prion protein (PrP(C)) as a putative receptor for Aβ. We show here that Aβ oligomers signal in cells in a PrP(C)-dependent manner, as might be expected if Aβ oligomers use PrP(C) as a receptor. Immunofluorescence, flow cytometry and cell surface protein biotinylation experiments indicated that treatment with Aβ oligomers, but not monomers, increased the localization of PrP(C) at the cell surface in cell lines. These results were reproduced in hippocampal neuronal cultures by labeling cell surface PrP(C). In order to understand possible mechanisms involved with this effect of Aβ oligomers, we used live cell confocal and total internal reflection microscopy in cell lines. Aβ oligomers inhibited the constitutive endocytosis of PrP(C), but we also found that after Aβ oligomer-treatment PrP(C) formed more clusters at the cell surface, suggesting the possibility of multiple effects of Aβ oligomers. Our experiments show for the first time that Aβ oligomers signal in a PrP(C)-dependent way and that they can affect PrP(C) trafficking, increasing its localization at the cell surface.

  3. Wnt-5a occludes Aβ oligomer-induced depression of glutamatergic transmission in hippocampal neurons

    PubMed Central

    2010-01-01

    Background Soluble amyloid-β (Aβ;) oligomers have been recognized to be early and key intermediates in Alzheimer's disease (AD)-related synaptic dysfunction. Aβ oligomers block hippocampal long-term potentiation (LTP) and impair rodent spatial memory. Wnt signaling plays an important role in neural development, including synaptic differentiation. Results We report here that the Wnt signaling activation prevents the synaptic damage triggered by Aβ oligomers. Electrophysiological analysis of Schaffer collaterals-CA1 glutamatergic synaptic transmission in hippocampal slices indicates that Wnt-5a increases the amplitude of field excitatory postsynaptic potentials (fEPSP) and both AMPA and NMDA components of the excitatory postsynaptic currents (EPSCs), without modifying the paired pulse facilitation (PPF). Conversely, in the presence of Aβ oligomers the fEPSP and EPSCs amplitude decreased without modification of the PPF, while the postsynaptic scaffold protein (PSD-95) decreased as well. Co-perfusion of hippocampal slices with Wnt-5a and Aβ oligomers occludes against the synaptic depression of EPSCs as well as the reduction of PSD-95 clusters induced by Aβ oligomers in neuronal cultures. Taken together these results indicate that Wnt-5a and Aβ oligomers inversely modulate postsynaptic components. Conclusion These results indicate that post-synaptic damage induced by Aβ oligomers in hippocampal neurons is prevented by non-canonical Wnt pathway activation. PMID:20205789

  4. Ultrahigh mass resolution and accurate mass measurements as a tool to characterize oligomers in secondary organic aerosols.

    PubMed

    Reinhardt, Alain; Emmenegger, Christian; Gerrits, Bertran; Panse, Christian; Dommen, Josef; Baltensperger, Urs; Zenobi, Renato; Kalberer, Markus

    2007-06-01

    Organic aerosols are a major fraction, often more than 50%, of the total atmospheric aerosol mass. The chemical composition of the total organic aerosol mass is poorly understood, although hundreds of compounds have been identified in the literature. High molecular weight compounds have recently gained much attention because this class of compounds potentially represents a major fraction of the unexplained organic aerosol mass. Here we analyze secondary organic aerosols, generated in a smog chamber from alpha-pinene ozonolysis with ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). About 450 compounds are detected in the mass range of m/z 200-700. The mass spectrum is clearly divided into a low molecular weight range (monomer) and a high molecular weight range, where dimers and trimers are distinguishable. Using the Kendrick mass analysis, the elemental composition of about 60% of all peaks could be determined throughout the whole mass range. Most compounds have high O:C ratios between 0.4 and 0.6. Small compounds (i.e., monomers) have a higher maximum O:C ratio than dimers and trimers, suggesting that condensation reactions with, for example, the loss of water are important in the oligomer formation process. A program developed in-house was used to determine exact mass differences between peaks in the monomer, dimer, and trimer mass range to identify potential monomer building blocks, which form the co-oligomers observed in the mass spectrum. A majority of the peaks measured in the low mass region of the spectrum (m/z < 300) is also found in the calculated results. For the first time the elemental composition of the majority of peaks over a wide mass range was determined using advanced data analysis methods for the analysis of ultra-high-resolution MS data. Possible oligomer formation mechanisms in secondary organic aerosols were investigated.

  5. Theory of microphase separation in homopolymer oligomer mixtures

    NASA Astrophysics Data System (ADS)

    Olemskoi, Alexander; Savelyev, Alexey

    2005-11-01

    This work starts with the review of theoretical methods proposed, during past decades, for description of phase behavior in different polymer systems, involving variety of linear polymers (regular and polydisperse block (co)polymers, random polymers) and the polymer systems with non-covalent bonds of different strength. Microphase separation (MS) into different ordered mesophases is known to be the principal property of such systems. It is shown that most of the theoretical approaches proposed for description of the MS are based on the simple random phase approximation (RPA). It turns out, however, that mean field RPA method applied to description of the systems with non-covalent bonds does not provide the whole picture of MS. We show that the problem here arises when one treats both Flory-Huggins non-associated interactions and non-covalent bonds (hydrogen, ionic) within the unified RPA scheme, which is obviously rough for description of the latter type of interactions. Such a theory was developed in a few recent papers for the systems involving weak hydrogen bonds between homopolymer chains and the low molecular weight oligomers (surfactants). However, it leaves some experimental data unaccounted. The purpose of this review is to consider more detailed theory which is able to explain not only all the experimental data for the above systems but also to take into account the strength variation of non-bonding interactions. In particular, we consider the strong ionic interactions, weak hydrogen bonding, and the interactions of intermediate strength between polymer chain and short oligomers within our unifying theory. To develop such a description in a self-consistent way we propose to use a general field theory of stochastic systems. The mesoscopic (lamellar) structure of the periodically alternating layers of stretched homopolymer chains surrounded by perpendicularly oriented oligomeric tails is studied for the systems with both strong (ionic) and weak (hydrogen

  6. Temperature oscillations near natural nuclear reactor cores and the potential for prebiotic oligomer synthesis.

    PubMed

    Adam, Zachary R

    2016-06-01

    Geologic settings capable of driving prebiotic oligomer synthesis reactions remain a relatively unexplored aspect of origins of life research. Natural nuclear reactors are an example of Precambrian energy sources that produced unique temperature fluctuations. Heat transfer models indicate that water-moderated, convectively-cooled natural fission reactors in porous host rocks create temperature oscillations that resemble those employed in polymerase chain reaction (PCR) devices to artificially amplify oligonucleotides. This temperature profile is characterized by short-duration pulses up to 70-100 °C, followed by a sustained period of temperatures in the range of 30-70 °C, and finally a period of relaxation to ambient temperatures until the cycle is restarted by a fresh influx of pore water. For a given reactor configuration, temperature maxima and the time required to relax to ambient temperatures depend most strongly on the aggregate effect of host rock permeability in decreasing the thermal expansion and increasing the viscosity and evaporation temperature of the pore fluids. Once formed, fission-fueled reactors can sustain multi-kilowatt-level power production for 10(5)-10(6) years, ensuring microenvironmental longevity and chemical output. The model outputs indicate that organic synthesis on young planetary bodies with a sizeable reservoir of fissile material can involve more sophisticated energy dissipation pathways than modern terrestrial analog settings alone would suggest.

  7. Temperature oscillations near natural nuclear reactor cores and the potential for prebiotic oligomer synthesis

    NASA Astrophysics Data System (ADS)

    Adam, Zachary R.

    2016-06-01

    Geologic settings capable of driving prebiotic oligomer synthesis reactions remain a relatively unexplored aspect of origins of life research. Natural nuclear reactors are an example of Precambrian energy sources that produced unique temperature fluctuations. Heat transfer models indicate that water-moderated, convectively-cooled natural fission reactors in porous host rocks create temperature oscillations that resemble those employed in polymerase chain reaction (PCR) devices to artificially amplify oligonucleotides. This temperature profile is characterized by short-duration pulses up to 70-100 °C, followed by a sustained period of temperatures in the range of 30-70 °C, and finally a period of relaxation to ambient temperatures until the cycle is restarted by a fresh influx of pore water. For a given reactor configuration, temperature maxima and the time required to relax to ambient temperatures depend most strongly on the aggregate effect of host rock permeability in decreasing the thermal expansion and increasing the viscosity and evaporation temperature of the pore fluids. Once formed, fission-fueled reactors can sustain multi-kilowatt-level power production for 105-106 years, ensuring microenvironmental longevity and chemical output. The model outputs indicate that organic synthesis on young planetary bodies with a sizeable reservoir of fissile material can involve more sophisticated energy dissipation pathways than modern terrestrial analog settings alone would suggest.

  8. Alzheimer's Therapeutics Targeting Amyloid Beta 1–42 Oligomers I: Abeta 42 Oligomer Binding to Specific Neuronal Receptors Is Displaced by Drug Candidates That Improve Cognitive Deficits

    PubMed Central

    Izzo, Nicholas J.; Staniszewski, Agnes; To, Lillian; Fa, Mauro; Teich, Andrew F.; Saeed, Faisal; Wostein, Harrison; Walko, Thomas; Vaswani, Anisha; Wardius, Meghan; Syed, Zanobia; Ravenscroft, Jessica; Mozzoni, Kelsie; Silky, Colleen; Rehak, Courtney; Yurko, Raymond; Finn, Patricia; Look, Gary; Rishton, Gilbert; Safferstein, Hank; Miller, Miles; Johanson, Conrad; Stopa, Edward; Windisch, Manfred; Hutter-Paier, Birgit; Shamloo, Mehrdad; Arancio, Ottavio; LeVine, Harry; Catalano, Susan M.

    2014-01-01

    Synaptic dysfunction and loss caused by age-dependent accumulation of synaptotoxic beta amyloid (Abeta) 1–42 oligomers is proposed to underlie cognitive decline in Alzheimer's disease (AD). Alterations in membrane trafficking induced by Abeta oligomers mediates reduction in neuronal surface receptor expression that is the basis for inhibition of electrophysiological measures of synaptic plasticity and thus learning and memory. We have utilized phenotypic screens in mature, in vitro cultures of rat brain cells to identify small molecules which block or prevent the binding and effects of Abeta oligomers. Synthetic Abeta oligomers bind saturably to a single site on neuronal synapses and induce deficits in membrane trafficking in neuronal cultures with an EC50 that corresponds to its binding affinity. The therapeutic lead compounds we have found are pharmacological antagonists of Abeta oligomers, reducing the binding of Abeta oligomers to neurons in vitro, preventing spine loss in neurons and preventing and treating oligomer-induced deficits in membrane trafficking. These molecules are highly brain penetrant and prevent and restore cognitive deficits in mouse models of Alzheimer's disease. Counter-screening these compounds against a broad panel of potential CNS targets revealed they are highly potent and specific ligands of the sigma-2/PGRMC1 receptor. Brain concentrations of the compounds corresponding to greater than 80% receptor occupancy at the sigma-2/PGRMC1 receptor restore cognitive function in transgenic hAPP Swe/Ldn mice. These studies demonstrate that synthetic and human-derived Abeta oligomers act as pharmacologically-behaved ligands at neuronal receptors - i.e. they exhibit saturable binding to a target, they exert a functional effect related to their binding and their displacement by small molecule antagonists blocks their functional effect. The first-in-class small molecule receptor antagonists described here restore memory to normal in multiple AD

  9. Alzheimer's therapeutics targeting amyloid beta 1-42 oligomers I: Abeta 42 oligomer binding to specific neuronal receptors is displaced by drug candidates that improve cognitive deficits.

    PubMed

    Izzo, Nicholas J; Staniszewski, Agnes; To, Lillian; Fa, Mauro; Teich, Andrew F; Saeed, Faisal; Wostein, Harrison; Walko, Thomas; Vaswani, Anisha; Wardius, Meghan; Syed, Zanobia; Ravenscroft, Jessica; Mozzoni, Kelsie; Silky, Colleen; Rehak, Courtney; Yurko, Raymond; Finn, Patricia; Look, Gary; Rishton, Gilbert; Safferstein, Hank; Miller, Miles; Johanson, Conrad; Stopa, Edward; Windisch, Manfred; Hutter-Paier, Birgit; Shamloo, Mehrdad; Arancio, Ottavio; LeVine, Harry; Catalano, Susan M

    2014-01-01

    Synaptic dysfunction and loss caused by age-dependent accumulation of synaptotoxic beta amyloid (Abeta) 1-42 oligomers is proposed to underlie cognitive decline in Alzheimer's disease (AD). Alterations in membrane trafficking induced by Abeta oligomers mediates reduction in neuronal surface receptor expression that is the basis for inhibition of electrophysiological measures of synaptic plasticity and thus learning and memory. We have utilized phenotypic screens in mature, in vitro cultures of rat brain cells to identify small molecules which block or prevent the binding and effects of Abeta oligomers. Synthetic Abeta oligomers bind saturably to a single site on neuronal synapses and induce deficits in membrane trafficking in neuronal cultures with an EC50 that corresponds to its binding affinity. The therapeutic lead compounds we have found are pharmacological antagonists of Abeta oligomers, reducing the binding of Abeta oligomers to neurons in vitro, preventing spine loss in neurons and preventing and treating oligomer-induced deficits in membrane trafficking. These molecules are highly brain penetrant and prevent and restore cognitive deficits in mouse models of Alzheimer's disease. Counter-screening these compounds against a broad panel of potential CNS targets revealed they are highly potent and specific ligands of the sigma-2/PGRMC1 receptor. Brain concentrations of the compounds corresponding to greater than 80% receptor occupancy at the sigma-2/PGRMC1 receptor restore cognitive function in transgenic hAPP Swe/Ldn mice. These studies demonstrate that synthetic and human-derived Abeta oligomers act as pharmacologically-behaved ligands at neuronal receptors--i.e. they exhibit saturable binding to a target, they exert a functional effect related to their binding and their displacement by small molecule antagonists blocks their functional effect. The first-in-class small molecule receptor antagonists described here restore memory to normal in multiple AD models

  10. X-ray Crystallographic Structure of Oligomers Formed by a Toxic β-Hairpin Derived from α-Synuclein: Trimers and Higher-Order Oligomers.

    PubMed

    Salveson, Patrick J; Spencer, Ryan K; Nowick, James S

    2016-04-06

    Oligomeric assemblies of the protein α-synuclein are thought to cause neurodegeneration in Parkinson's disease and related synucleinopathies. Characterization of α-synuclein oligomers at high resolution is an outstanding challenge in the field of structural biology. The absence of high-resolution structures of oligomers formed by α-synuclein impedes understanding the synucleinopathies at the molecular level. This paper reports the X-ray crystallographic structure of oligomers formed by a peptide derived from residues 36-55 of α-synuclein. The peptide 1a adopts a β-hairpin structure, which assembles in a hierarchical fashion. Three β-hairpins assemble to form a triangular trimer. Three copies of the triangular trimer assemble to form a basket-shaped nonamer. Two nonamers pack to form an octadecamer. Molecular modeling suggests that full-length α-synuclein may also be able to assemble in this fashion. Circular dichroism spectroscopy demonstrates that peptide 1a interacts with anionic lipid bilayer membranes, like oligomers of full-length α-synuclein. LDH and MTT assays demonstrate that peptide 1a is toxic toward SH-SY5Y cells. Comparison of peptide 1a to homologues suggests that this toxicity results from nonspecific interactions with the cell membrane. The oligomers formed by peptide 1a are fundamentally different than the proposed models of the fibrils formed by α-synuclein and suggest that α-Syn36-55, rather than the NAC, may nucleate oligomer formation.

  11. An investigation into the effect of amphiphilic siloxane oligomers on dermal fibroblasts.

    PubMed

    Farrugia, Brooke L; Keddie, Daniel J; George, Graeme A; Lynam, Emily C; Brook, Michael A; Upton, Zee; Dargaville, Tim R

    2012-07-01

    This study investigates the effect of well-defined poly(dimethylsiloxane)-poly(ethylene glycol) (PDMS-PEG) ABA linear block co-oligomers on the proliferation of human dermal fibroblasts. The co-oligomers assessed ranged in molecular weight (MW) from 1335 to 5208 Da and hydrophilic-lipophilic balance (HLB) from 5.9 to 16.6 by varying the number of both PDMS and PEG units. In general, it was found that co-oligomers of low MW or intermediate hydrophilicity significantly reduced fibroblast proliferation. A linear relationship between down-regulation of fibroblast proliferation, and the ratio HLB/MW was observed at concentrations of 0.1 and 1.0 wt % of the oligomers. This enabled the structures with highest efficiency to be determined. These results suggest the possible use of the PEG-PDMS-PEG block co-oligomers as an alternative to silicone gels for hypertrophic scar remediation.

  12. Direct PIP2 binding mediates stable oligomer formation of the serotonin transporter

    PubMed Central

    Anderluh, Andreas; Hofmaier, Tina; Klotzsch, Enrico; Kudlacek, Oliver; Stockner, Thomas; Sitte, Harald H.; Schütz, Gerhard J.

    2017-01-01

    The human serotonin transporter (hSERT) mediates uptake of serotonin from the synaptic cleft and thereby terminates serotonergic signalling. We have previously found by single-molecule microscopy that SERT forms stable higher-order oligomers of differing stoichiometry at the plasma membrane of living cells. Here, we report that SERT oligomer assembly at the endoplasmic reticulum (ER) membrane follows a dynamic equilibration process, characterized by rapid exchange of subunits between different oligomers, and by a concentration dependence of the degree of oligomerization. After trafficking to the plasma membrane, however, the SERT stoichiometry is fixed. Stabilization of the oligomeric SERT complexes is mediated by the direct binding to phosphoinositide phosphatidylinositol-4,5-biphosphate (PIP2). The observed spatial decoupling of oligomer formation from the site of oligomer operation provides cells with the ability to define protein quaternary structures independent of protein density at the cell surface. PMID:28102201

  13. 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

  14. Alginate gels with a combination of calcium and chitosan oligomer mixtures as crosslinkers.

    PubMed

    Feng, Yiming; Kopplin, Georg; Sato, Kimihiko; Draget, Kurt I; Vårum, Kjell M

    2017-01-20

    Alginates are polysaccharides that are widely used in relation to their ability to form gels. Recently we reported that alginates may also form gels with chitosan oligomers as crosslinkers (Khong, Aarstad, Skjåk-Bræk, Draget, & Vårum, 2013). The purpose of the present study was to characterize alginate gels crosslinked with calcium and chitosan oligomers. Using two different alginates of similar molecular weights but different chemical composition, i.e. guluronic acid content of 46 and 68%, we found that both alginates could form homogeneous gels with calcium and chitosan oligomers separately and without syneresis. Systematic combinations of calcium and chitosan oligomers as crosslinkers were tested, showing that up to 50% of the calcium could be substituted with chitosan oligomers without reduction in gel strength or increased syneresis for the alginate with the lowest guluronic acid content. Furthermore, the kinetics of the combined gels were different from pure calcium alginate gels.

  15. 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

    2016-07-23

    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.

  16. 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

  17. 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

  18. Dissecting the role of disulfide bonds on the amyloid formation of insulin

    SciTech Connect

    Li, Yang; Gong, Hao; Sun, Yue; Yan, Juan; Cheng, Biao; Zhang, Xin; Huang, Jing; Yu, Mengying; Guo, Yu; Zheng, Ling; Huang, Kun

    2012-06-29

    Highlights: Black-Right-Pointing-Pointer We dissect how individual disulfide bond affects the amyloidogenicity of insulin. Black-Right-Pointing-Pointer A controlled reduction system for insulin is established in this study. Black-Right-Pointing-Pointer Disulfide breakage is associated with unfolding and increased amyloidogenicity. Black-Right-Pointing-Pointer Breakage of A6-A11 is associated with significantly increased cytotoxicity. Black-Right-Pointing-Pointer Analogs without A6-A11 have a higher potency to form high order toxic oligomers. -- Abstract: Disulfide bonds play a critical role in the stability and folding of proteins. Here, we used insulin as a model system, to investigate the role of its individual disulfide bond during the amyloid formation of insulin. Tris(2-carboxyethyl)phosphine (TCEP) was applied to reduce two of the three disulfide bonds in porcine insulin and the reduced disulfide bonds were then alkylated by iodoacetamide. Three disulfide bond-modified insulin analogs, INS-2 (lack of A6-A11), INS-3 (lack of A7-B7) and INS-6 (lack of both A6-A11 and A7-B7), were obtained. Far-UV circular dichroism (CD) spectroscopy results indicated that the secondary structure of INS-2 was the closest to insulin under neutral conditions, followed by INS-3 and INS-6, whereas in an acidic solution all analogs were essentially unfolded. To test how these modifications affect the amyloidogenicity of insulin, thioflavin-T (ThT) fluorescence and transmission electronic microscopy (TEM) were performed. Our results showed that all analogs were more prone to aggregation than insulin, with the order of aggregation rates being INS-6 > INS-3 > INS-2. Cross-linking of unmodified proteins (PICUP) assay results showed that analogs without A6-A11 (INS-2 and INS-6) have a higher potential for oligomerization than insulin and INS-3, which is accompanied with a higher cytotoxicity as the hemolytic assays of human erythrocytes suggested. The results indicated that breakage of A7

  19. 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.

  20. Protein Crystal Bovine Insulin

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The comparison of protein crystal, Bovine Insulin space-grown (left) and earth-grown (right). Facilitates the incorporation of glucose into cells. In diabetics, there is either a decrease in or complete lack of insulin, thereby leading to several harmful complications. Principal Investigator is Larry DeLucas.

  1. One-Step Synthesis of Precursor Oligomers for Organic Photovoltaics: A Comparative Study between Polymers and Small Molecules.

    PubMed

    Li, Wei; Wang, Daojuan; Wang, Suhao; Ma, Wei; Hedström, Svante; James, David Ian; Xu, Xiaofeng; Persson, Petter; Fabiano, Simone; Berggren, Magnus; Inganäs, Olle; Huang, Fei; Wang, Ergang

    2015-12-16

    Two series of oligomers TQ and rhodanine end-capped TQ-DR were synthesized using a facile one-step method. Their optical, electrical, and thermal properties and photovoltaic performances were systematically investigated and compared. The TQ series of oligomers were found to be amorphous, whereas the TQ-DR series are semicrystalline. For the TQ oligomers, the results obtained in solar cells show that as the chain length of the oligomers increases, an increase in power conversion efficiency (PCE) is obtained. However, when introducing 3-ethylrhodanine into the TQ oligomers as end groups, the PCE of the TQ-DR series of oligomers decreases as the chain length increases. Moreover, the TQ-DR series of oligomers give much higher performances compared to the original amorphous TQ series of oligomers owing to the improved extinction coefficient (ε) and crystallinity afforded by the rhodanine. In particular, the highly crystalline oligomer TQ5-DR, which has the shortest conjugation length shows a high hole mobility of 0.034 cm(2) V(-1) s(-1) and a high PCE of 3.14%, which is the highest efficiency out of all of the six oligomers. The structure-property correlations for all of the oligomers and the TQ1 polymer demonstrate that structural control of enhanced intermolecular interactions and crystallinity is a key for small molecules/oligomers to achieve high mobilities, which is an essential requirement for use in OPVs.

  2. Brain amyloid-β oligomers in ageing and Alzheimer's disease.

    PubMed

    Lesné, Sylvain E; Sherman, Mathew A; Grant, Marianne; Kuskowski, Michael; Schneider, Julie A; Bennett, David A; Ashe, Karen H

    2013-05-01

    Alzheimer's disease begins about two decades before the onset of symptoms or neuron death, and is believed to be caused by pathogenic amyloid-β aggregates that initiate a cascade of molecular events culminating in widespread neurodegeneration. The microtubule binding protein tau may mediate the effects of amyloid-β in this cascade. Amyloid plaques comprised of insoluble, fibrillar amyloid-β aggregates are the most characteristic feature of Alzheimer's disease. However, the correspondence between the distribution of plaques and the pattern of neurodegeneration is tenuous. This discrepancy has stimulated the investigation of other amyloid-β aggregates, including soluble amyloid-β oligomers. Different soluble amyloid-β oligomers have been studied in several mouse models, but not systematically in humans. Here, we measured three amyloid-β oligomers previously described in mouse models-amyloid-β trimers, Aβ*56 and amyloid-β dimers-in brain tissue from 75 cognitively intact individuals, ranging from young children to the elderly, and 58 impaired subjects with mild cognitive impairment or probable Alzheimer's disease. As in mouse models, where amyloid-β trimers appear to be the fundamental amyloid-β assembly unit of Aβ*56 and are present in young mice prior to memory decline, amyloid-β trimers in humans were present in children and adolescents; their levels rose gradually with age and were significantly above baseline in subjects in their 70s. Aβ*56 levels were negligible in children and young adults, rose significantly above baseline in subjects in their 40s and increased steadily thereafter. Amyloid-β dimers were undetectable until subjects were in their 60s; their levels then increased sharply and correlated with plaque load. Remarkably, in cognitively intact individuals we found strong positive correlations between Aβ*56 and two pathological forms of soluble tau (tau-CP13 and tau-Alz50), and negative correlations between Aβ*56 and two postsynaptic

  3. Chromium and insulin resistance.

    PubMed

    Anderson, Richard A

    2003-12-01

    Insulin resistance leads to the inability of insulin to control the utilization and storage of glucose. It is associated initially with elevated levels of circulating insulin followed by glucose intolerance which may progress to type 2 diabetes, hyperlipidaemia, hypertension, obesity and cardiovascular diseases. While the causes of these diseases are multifactorial, one nutrient that is associated with all of these abnormalities is Cr. In the presence of Cr, in a biologically active form, much lower levels of insulin are required. Modern diets, which are often high in refined carbohydrates, are not only low in Cr, but lead to enhanced Cr losses. In response to the consumption of refined carbohydrates, there is a rapid rise in blood sugar leading to elevations in insulin that cause a mobilization of Cr. Once mobilized, Cr is not reabsorbed but lost via the urine leading to decreased Cr stores. Several studies involving both human subjects and experimental animals have reported improvements in insulin sensitivity, blood glucose, insulin, lipids, haemoglobin A1c, lean body mass and related variables in response to improved Cr nutrition. However, not all studies have reported beneficial effects associated with improved Cr nutrition. Well-controlled human studies are needed to document an unequivocal effect of Cr on insulin sensitivity in human subjects. Studies need to involve a significant number of subjects with insulin resistance, glucose intolerance or early stages of diabetes, who have not been taking supplements containing Cr for at least 4 months, and involve at least 400 to 600 microg supplemental Cr daily or more. Studies should be at least 4 months to document sustained effects of supplemental Cr on insulin resistance and related variables. Cr is a nutrient and not a therapeutic agent and therefore will only be of benefit to those whose problems are due to suboptimal intake of Cr.

  4. Guanidine hydrochloride denaturation of dopamine-induced α-synuclein oligomers: a small-angle X-ray scattering study.

    PubMed

    Pham, Chi L L; Kirby, Nigel; Wood, Kathleen; Ryan, Timothy; Roberts, Blaine; Sokolova, Anna; Barnham, Kevin J; Masters, Colin L; Knott, Robert B; Cappai, Roberto; Curtain, Cyril C; Rekas, Agata

    2014-01-01

    Alpha-synuclein (α-syn) forms the amyloid-containing Lewy bodies found in the brain in Parkinson's disease. The neurotransmitter dopamine (DA) reacts with α-syn to form SDS-resistant soluble, non-amyloid, and melanin-containing oligomers. Their toxicity is debated, as is the nature of their structure and their relation to amyloid-forming conformers of α-syn. The small-angle X-ray scattering technique in combination with modeling by the ensemble optimization method showed that the un-reacted native protein populated three broad classes of conformer, while reaction with DA gave a restricted ensemble range suggesting that the rigid melanin molecule played an important part in their structure. We found that 6 M guanidine hydrochloride did not dissociate α-syn DA-reacted dimers and trimers, suggesting covalent linkages. The pathological significance of covalent association is that if they are non-toxic, the oligomers would act as a sink for toxic excess DA and α-syn; if toxic, their stability could enhance their toxicity. We argue it is essential, therefore, to resolve the question of whether they are toxic or not.

  5. Toughening of BIS maleimide resins: Synthesis and characterization of maleimide terminated poly(arylene ether) oligomers and polymers

    NASA Technical Reports Server (NTRS)

    Mcgrath, J. E.; Lyle, G. D.; Jurek, M. J.; Mohanty, D.; Hedrick, J. C.

    1986-01-01

    Amine functional poly(arylene ether) sulfones were previously reported. Herein, the chemistry was extended to amorphous poly(arylene ether) ketones because of their higher fracture toughness values, relative to the polysulfones. It was demonstrated that the amino functional oligomers undergo a self-crosslinking reaction at temperatures above about 220 C. This produces an insoluble, but ductile network that has excellent resistance. A ketamine structure hypothesis was proposed and verified using solid state magic angle NMR. In most cases, the water generated upon ketamine formation is too low to produce porosity and solid networks are obtained. The stability of the ketamine networks towards hydrolysis is excellent. The chemistry was further demonstrated to be able to crosslink preformed nonfunctional poly(arylene ether) ketones if a difunctional amine was utilized. This concept has the possibility of greatly improving the creep resistance of thermoplastics. Also, a new technique was developed for converting the amine functional oligomers cleanly into maleimide structures. This method involves reacting maleic anhydride with monomeric aminophenols in the presence of solvent mixtures.

  6. Electrosynthesis, spectral and structural studies of a semi-conducting oligomer deriving from a methoxy-substituted chalcone

    NASA Astrophysics Data System (ADS)

    Aribi, Imen; Ghomrasni, Saber; Ayachi, Sahbi; Alimi, Kamel; Roudesli, Sadok; Said, Ayoub Haj

    2016-11-01

    The anodic oxidation of a substituted chalcone namely the (E)-1-(4-methoxyphenyl)-3-(3,4,5-trimethoxyphenyl) prop-2-enone (TMC) was investigated by different electrochemical techniques using a platinum working electrode in acetonitrile. On the cyclic voltammetry time scale, the TMC exhibited a single irreversible anodic peak around 1.4 V vs. Ag/AgCl and the coupling of the radical cations, issued from the first electron transfer, was the governing reaction near the electrode. Electrolysis at a constant potential revealed that an oligo o-phenylenevinylene was the main product of the anodic oxidation of TMC. The chemical structure of the isolated oligomer was elucidated by 1H, 13C NMR, and IR spectroscopy. Gel permeation chromatography indicated that the average chain length was about 5 units. In addition, the obtained oligomer was thermally stable up to 220 °C and exhibited a light emission in the indigo-blue region. Finally, a mechanism for the TMC electro-oligomerization was proposed on the basis of the electrochemical data and the theoretical calculation of the spin densities distribution for the TMC radical cation.

  7. The Flavodiiron Protein Flv3 Functions as a Homo-Oligomer During Stress Acclimation and is Distinct from the Flv1/Flv3 Hetero-Oligomer Specific to the O2 Photoreduction Pathway

    PubMed Central

    Mustila, Henna; Paananen, Pasi; Battchikova, Natalia; Santana-Sánchez, Anita; Muth-Pawlak, Dorota; Hagemann, Martin; Aro, Eva-Mari; Allahverdiyeva, Yagut

    2016-01-01

    The flavodiiron proteins (FDPs) Flv1 and Flv3 in cyanobacteria function in photoreduction of O2 to H2O, without concomitant formation of reactive oxygen species, known as the Mehler-like reaction. Both Flv1 and Flv3 are essential for growth under fluctuating light (FL) intensities, providing protection for PSI. Here we compared the global transcript profiles of the wild type (WT), Δflv1 and Δflv1/Δflv3 grown under constant light (GL) and FL. In the WT, FL induced the largest down-regulation in transcripts involved in carbon-concentrating mechanisms (CCMs), while those of the nitrogen assimilation pathways increased as compared with GL. Already under GL the Δflv1/Δflv3 double mutant demonstrated a partial down-regulation of transcripts for CCM and nitrogen metabolism, while in FL conditions the transcripts for nitrogen assimilation were strongly down-regulated. Many alterations were specific only for Δflv1/Δflv3, and not detected in Δflv1, suggesting that certain transcripts are affected primarily because of the lack of flv3. By constructing the strains overproducing solely either Flv1 or Flv3, we demonstrate that the homo-oligomers of these proteins also function in acclimation of cells to FL, by catalyzing reactions with as yet unidentified components, while the presence of both Flv1 and Flv3 is a prerequisite for the Mehler-like reaction and thus the electron transfer to O2. Considering the low expression of flv1, it is unlikely that the Flv1 homo-oligomer is present in the WT. PMID:26936793

  8. Fundamental Heterogeneous Reaction Chemistry Related to Secondary Organic Aerosols (SOA) in the Atmosphere

    NASA Astrophysics Data System (ADS)

    Akimoto, H.

    2016-11-01

    Typical reaction pathways of formation of dicarboxylic acids, larger multifunctional compounds, oligomers, and organosulfur and organonitrogen compounds in secondary organic aerosols (SOA), revealed by laboratory experimental studies are reviewed with a short introduction to field observations. In most of the reactions forming these compounds, glyoxal, methyl glyoxal and related difunctional carbonyl compounds play an important role as precursors, and so their formation pathways in the gas phase are discussed first. A substantial discussion is then presented for the OH-initiated aqueous phase radical oxidation reactions of glyoxal and other carbonyls which form dicarboxylic acids, larger multifunctional compounds and oligomers, and aqueous-phase non-radical reactions which form oligomers, organosulfates and organonitrogen compounds. Finally, the heterogeneous oxidation reaction of gaseous O3, OH and NO3 with liquid and solid organic aerosols at the air-particle interface is discussed relating to the aging of SOA in the atmosphere.

  9. VCD Studies on Chiral Characters of Metal Complex Oligomers

    PubMed Central

    Sato, Hisako; Yamagishi, Akihiko

    2013-01-01

    The present article reviews the results on the application of vibrational circular dichroism (VCD) spectroscopy to the study of stereochemical properties of chiral metal complexes in solution. The chiral characters reflecting on the vibrational properties of metal complexes are revealed by measurements of a series of β-diketonato complexes with the help of theoretical calculation. Attention is paid to the effects of electronic properties of a central metal ion on vibrational energy levels or low-lying electronic states. The investigation is further extended to the oligomers of β-diketonato complex units. The induction of chiral structures is confirmed by the VCD spectra when chiral inert moieties are connected with labile metal ions. These results have demonstrated how VCD spectroscopy is efficient in revealing the static and dynamic properties of mononuclear and multinuclear chiral metal complexes, which are difficult to clarify by means of other spectroscopes. PMID:23296273

  10. VCD studies on chiral characters of metal complex oligomers.

    PubMed

    Sato, Hisako; Yamagishi, Akihiko

    2013-01-07

    The present article reviews the results on the application of vibrational circular dichroism (VCD) spectroscopy to the study of stereochemical properties of chiral metal complexes in solution. The chiral characters reflecting on the vibrational properties of metal complexes are revealed by measurements of a series of β-diketonato complexes with the help of theoretical calculation. Attention is paid to the effects of electronic properties of a central metal ion on vibrational energy levels or low-lying electronic states. The investigation is further extended to the oligomers of β-diketonato complex units. The induction of chiral structures is confirmed by the VCD spectra when chiral inert moieties are connected with labile metal ions. These results have demonstrated how VCD spectroscopy is efficient in revealing the static and dynamic properties of mononuclear and multinuclear chiral metal complexes, which are difficult to clarify by means of other spectroscopes.

  11. EGFP oligomers as natural fluorescence and hydrodynamic standards

    PubMed Central

    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 μm2/s and 97.3…54.8 μm2/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

  12. Preformed Seeds Modulate Native Insulin Aggregation Kinetics.

    PubMed

    Dutta, Colina; Yang, Mu; Long, Fei; Shahbazian-Yassar, Reza; Tiwari, Ashutosh

    2015-12-10

    Insulin aggregates under storage conditions via disulfide interchange reaction. It is also known to form aggregates at the site of repeated injections in diabetes patients, leading to injection amyloidosis. This has fueled research in pharmaceutical and biotechnology industry as well as in academia to understand factors that modulate insulin stability and aggregation. The main aim of this study is to understand the factors that modulate aggregation propensity of insulin under conditions close to physiological and measure effect of "seeds" on aggregation kinetics. We explored the aggregation kinetics of insulin at pH 7.2 and 37 °C in the presence of disulfide-reducing agent dithiothreitol (DTT), using spectroscopy (UV-visible, fluorescence, and Fourier transform infrared spectroscopy) and microscopy (scanning electron microscopy, atomic force microscopy) techniques. We prepared insulin "seeds" by incubating disulfide-reduced insulin at pH 7.2 and 37 °C for varying lengths of time (10 min to 12 h). These seeds were added to the native protein and nucleation-dependent aggregation kinetics was measured. Aggregation kinetics was fastest in the presence of 10 min seeds suggesting they were nascent. Interestingly, intermediate seeds (30 min to 4 h incubation) resulted in formation of transient fibrils in 4 h that converted to amorphous aggregates upon longer incubation of 24 h. Overall, the results show that insulin under disulfide reducing conditions at pH and temperature close to physiological favors amorphous aggregate formation and seed "maturity" plays an important role in nucleation dependent aggregation kinetics.

  13. Tagging insulin in microgravity

    NASA Technical Reports Server (NTRS)

    Dobeck, Michael; Nelson, Ronald S.

    1992-01-01

    Knowing the exact subcellular sites of action of insulin in the body has the potential to give basic science investigators a basis from which a cause and cure for this disease can be approached. The goal of this project is to create a test reagent that can be used to visualize these subcellular sites. The unique microgravity environment of the Shuttle will allow the creation of a reagent that has the possibility of elucidating the subcellular sites of action of insulin. Several techniques have been used in an attempt to isolate the sites of action of items such as insulin. One of these is autoradiography in which the test item is obtained from animals fed radioactive materials. What is clearly needed is to visualize individual insulin molecules at their sites of action. The insulin tagging process to be used on G-399 involves the conjugation of insulin molecules with ferritin molecules to create a reagent that will be used back on Earth in an attempt to elucidate the sites of action of insulin.

  14. Insulin enhances metabolic capacities of cancer cells by dual regulation of glycolytic enzyme pyruvate kinase M2

    PubMed Central

    2013-01-01

    Background Insulin is tightly associated with cancer progression; however, mechanistic insights into such observations are poorly understood. Recent studies show that metabolic transformation is critical to cancer cell proliferation. Here, we attempt to understand the role of insulin in promotion of cancer metabolism. To this end, the role of insulin in regulating glycolytic enzyme pyruvate kinase M2 (PKM2) was examined. Results We observed that insulin up-regulated PKM2 expression, through PI3K/mTOR mediated HIF1α induction, but significantly reduced PKM2 activity independent of this pathway. Drop in PKM2 activity was attributed to subunit dissociation leading to formation of low activity PKM2 oligomers, as assessed by density gradient centrifugation. However, tyrosine 105 phosphorylation of PKM2, known for inhibiting PKM2 activity, remained unaffected on insulin treatment. Interestingly, insulin-induced ROS was found responsible for PKM2 activity reduction. The observed changes in PKM2 status led to augmented cancer metabolism. Insulin-induced PKM2 up-regulation resulted in enhanced aerobic glycolysis as confirmed by PKM2 knockdown studies. Further, PKM2 activity reduction led to characteristic pooling of glycolytic intermediates and increased accumulation of NADPH; suggesting diversion of glucose flux towards macromolecular synthesis, necessary for cancer cell growth. Conclusion The study identifies new PKM2-mediated effects of insulin on cancer metabolism, thus, advancing the understanding of insulin’s role in cancer. PMID:23837608

  15. 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.

  16. High-resolution atomic force microscopy of soluble Abeta42 oligomers.

    PubMed

    Mastrangelo, Iris A; Ahmed, Mahiuddin; Sato, Takeshi; Liu, Wei; Wang, Chengpu; Hough, Paul; Smith, Steven O

    2006-04-21

    Soluble oligomers and protofibrils are widely thought to be the toxic forms of the Abeta42 peptide associated with Alzheimer's disease. We have investigated the structure and formation of these assemblies using a new approach in atomic force microscopy (AFM) that yields high-resolution images of hydrated proteins and allows the structure of the smallest molecular weight (MW) oligomers to be observed and characterized. AFM images of monomers, dimers and other low MW oligomers at early incubation times (< 1h) are consistent with a hairpin structure for the monomeric Abeta42 peptide. The low MW oligomers are relatively compact and have significant order. The most constant dimension of these oligomers is their height (approximately 1-3 nm) above the mica surface; their lateral dimensions (width and length) vary between 5 nm and 10nm. Flat nascent protofibrils with lengths of over 40 nm are observed at short incubation times (< or = 3h); their lateral dimensions of 6-8 nm are consistent with a mass-per-length of 9 kDa/nm previously predicted for the elementary fibril subunit. High MW oligomers with lateral dimensions of 15-25 nm and heights ranging from 2-8 nm are common at high concentrations of Abeta. We show that an inhibitor designed to block the sheet-to-sheet packing in Abeta fibrils is able to cap the heights of these oligomers at approximately 4 nm. The observation of fine structure in the high MW oligomers suggests that they are able to nucleate fibril formation. AFM images obtained as a function of incubation time reveal a sequence of assembly from monomers to soluble oligomers and protofibrils.

  17. Infliximab and insulin resistance.

    PubMed

    Ursini, Francesco; Naty, Saverio; Grembiale, Rosa Daniela

    2010-06-01

    Insulin resistance is the most important pathophysiologic feature of obesity, type 2 diabetes mellitus and prediabetic states. TNF-alpha, a proinflammatory cytokine, plays a pivotal role in the pathogenesis of inflammation-associated insulin resistance during the course of rheumatic diseases. Therapies aimed at neutralizing TNF-alpha, such as the monoclonal antibody infliximab, represent a novel approach for the treatment of rheumatic diseases and allow to obtain significant results in terms of control of the inflammatory process. In this article we reviewed the scientific evidence published in the literature about a potential role of TNF-alpha blockade in improving insulin resistance in non-diabetic rheumatic patients.

  18. Studies on Oligomer Metal Complexes Derived from Bisamic Acid of Pyromellitic Dianhydride and 4-Bromoaniline

    PubMed Central

    Patel, Yogesh S.

    2014-01-01

    Novel oligomer metal complexes (2a–f) of the ligand 2,5-bis((4-bromophenyl)carbamoyl) terephthalic acid (1) were prepared using transition metal salts and characterized by various spectroscopic techniques. The geometry of oligomer metal complexes was carried out by electronic spectral analysis and magnetic measurement studies. Polymeric properties have also been carried out. Ligand was synthesized using pyromellitic dianhydride and 4-bromoaniline. It was duly characterized. All novel synthesized compounds 1 and 2a–f were evaluated for their antibacterial and antifungal activity. The results showed significantly higher antibacterial and antifungal activity of oligomer metal complexes compared to the ligand. PMID:27379295

  19. Studies on Oligomer Metal Complexes Derived from Bisamic Acid of Pyromellitic Dianhydride and 4-Bromoaniline.

    PubMed

    Patel, Yogesh S

    2014-01-01

    Novel oligomer metal complexes (2a-f) of the ligand 2,5-bis((4-bromophenyl)carbamoyl) terephthalic acid (1) were prepared using transition metal salts and characterized by various spectroscopic techniques. The geometry of oligomer metal complexes was carried out by electronic spectral analysis and magnetic measurement studies. Polymeric properties have also been carried out. Ligand was synthesized using pyromellitic dianhydride and 4-bromoaniline. It was duly characterized. All novel synthesized compounds 1 and 2a-f were evaluated for their antibacterial and antifungal activity. The results showed significantly higher antibacterial and antifungal activity of oligomer metal complexes compared to the ligand.

  20. Common structure and toxic function of amyloid oligomers implies a common mechanism of pathogenesis.

    PubMed

    Glabe, Charles G; Kayed, Rakez

    2006-01-24

    Recent findings indicate that soluble amyloid oligomers may represent the primary pathologic species in degenerative diseases. These amyloid oligomers share common structural features and the ability to permeabilize membranes, suggesting that they also share a common primary mechanism of pathogenesis. Membrane permeabilization by amyloid oligomers may initiate a common group of downstream pathologic processes, including intracellular calcium dyshomeostasis, production of reactive oxygen species, altered signaling pathways, and mitochondrial dysfunction that represent key effectors of cellular dysfunction and cell death in amyloid-associated degenerative disease, such as sporadic inclusion-body myositis.

  1. 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.

  2. 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.

  3. Effect of molecular weight of oligomer on ionic diffusion in oligomer electrolytes and its implication for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Park, Jong Hyuk; Choi, Kyu Jin; Kim, Junkyung; Kang, Yong Soo; Lee, Sang-Soo

    This study measures the diffusion coefficients of I - and I 3 - in oligomer electrolytes as a function of the molecular weight of oligomers and investigates their effect on the performance of dye-sensitized solar cells (DSSCs). The high-diffusion coefficients of ions in an oligomer electrolyte with a lower molecular weight can help to promote the redox mechanism in DSSCs and thereby increase the short-circuit current density. They can also cause a decrease in the open-circuit voltage since a high-diffusion coefficient of I 3 - is capable of reducing the lifetime of electrons in TiO 2 electrodes. To offset these effects, N-methyl-benzimidazole is added to the oligomer electrolytes, thereby improving the open-circuit voltage and fill factor and, consequently, the overall energy-conversion efficiency, which increases to over 5%. A further test involving storage at a high temperature of 75 °C demonstrates that DSSCs employing the oligomer electrolytes show excellent thermal stability over 200 h.

  4. Large Soluble Oligomers of Amyloid β-Protein from Alzheimer Brain Are Far Less Neuroactive Than the Smaller Oligomers to Which They Dissociate.

    PubMed

    Yang, Ting; Li, Shaomin; Xu, Huixin; Walsh, Dominic M; Selkoe, Dennis J

    2017-01-04

    Soluble oligomers of amyloid β-protein (oAβ) isolated from the brains of Alzheimer's disease (AD) patients have been shown experimentally (in the absence of amyloid plaques) to impair hippocampal synaptic plasticity, decrease synapses, induce tau hyperphosphorylation and neuritic dystrophy, activate microglial inflammation, and impair memory in normal adult rodents. Nevertheless, there has been controversy about what types of oligomers actually confer these AD-like phenotypes. Here, we show that the vast majority of soluble Aβ species obtained from brains of humans who died with confirmed AD elute at high molecular weight (HMW) on nondenaturing size-exclusion chromatography. These species have little or no cytotoxic activity in several bioassays. However, incubation of HMW oAβ in mildly alkaline buffer led to their quantitative dissociation into low molecular weight oligomers (∼8-70 kDa), and these were now far more bioactive: they impaired hippocampal LTP, decreased neuronal levels of β2-adrenergic receptors, and activated microglia in wt mice in vivo Thus, most soluble Aβ assemblies in AD cortex are large and inactive but under certain circumstances can dissociate into smaller, highly bioactive species. Insoluble amyloid plaques likely sequester soluble HMW oligomers, limiting their potential to dissociate. We conclude that conditions that destabilize HMW oligomers or retard the sequestration of their smaller, more bioactive components are important drivers of Aβ toxicity. Selectively targeting these small, cytotoxic forms should be therapeutically beneficial.

  5. Coulombic free energy and salt ion association per phosphate of all-atom models of DNA oligomer: dependence on oligomer size.

    PubMed

    Shkel, Irina A; Record, M Thomas

    2012-08-23

    We investigate how the coulombic Gibbs free energy and salt ion association per phosphate charge of DNA oligomers vary with oligomer size (i.e. number of charged residues ∣ZD∣) at 0.15 M univalent salt by non-linear Poisson Boltzmann (NLPB) analysis of all-atom DNA models. Calculations of these quantities ([Formula: see text], [Formula: see text]) are performed for short and long double-stranded (ds) and single-stranded (ss) DNA oligomers, ranging from 4 to 118 phosphates (ds) and from 2 to 59 phosphates (ss). Behaviors of [Formula: see text] and [Formula: see text] as functions of ∣ZD∣ provide a measure of the range of the coulombic end effect and determine the size of an oligomer at which an interior region with the properties (per charge) of the infinite-length polyelectrolyte first appears. This size (10-11 phosphates at each end for ds DNA and 6-9 for ss DNA at 0.15 M salt) is in close agreement with values obtained previously by Monte Carlo and NLPB calculations for cylindrical models of polyions, and by analysis of binding of oligocations to DNA oligomers. Differences in [Formula: see text] and in [Formula: see text] between ss and ds DNA are used to predict effects of oligomeric size and salt concentration on duplex stability in the vicinity of 0.15 M salt. Results of all-atom calculations are compared with results of less structurally detailed models and with experimental data.

  6. Positive mode electrospray tandem mass spectrometry of poly(methacrylic acid) oligomers.

    PubMed

    Giordanengo, Rémi; Viel, Stéphane; Allard-Breton, Béatrice; Thévand, André; Charles, Laurence

    2009-06-01

    The dissociation of small poly(methacrylic acid) (PMAA) cations produced by electrospray was characterized by tandem mass spectrometry. Similarly to PMAA ions produced in the negative ion mode, the two electrosprayed cationic forms, namely [PMAA+Na](+) and [PMAA-H+2Na](+), were shown to fragment via a major pathway consisting of successive dehydration steps. Elimination of a water molecule would occur between two consecutive acid groups in a charged-remote mechanism and was shown to proceed as many times as pairs of acidic pendant groups were available. As a result, comparing the number of dehydration steps observed in the MS/MS spectrum of two consecutive oligomers from the polymeric distribution reveals the degree of polymerization of the molecule. Secondary less informative reactions were shown to consist of losses of CO and/or CO(2), depending on the nature of the precursor ion. These fragmentation rules could be used to characterize PMAA-based copolymers, as successfully demonstrated for a polymeric impurity in the tested PMAA sample.

  7. Non-Radiative Relaxation of Electronically Excited DNA Oligomers: Proton Coupled Charge Transfer

    NASA Astrophysics Data System (ADS)

    Lange, Adrian W.; Herbert, John M.

    2009-06-01

    We address possible relaxation mechanisms of electronically excited DNA oligomers with a combined quantum mechanics/molecular mechanics (QM/MM) approach. Using long-range corrected density functional theory (LRC-DFT), we show that charge transfer (CT) states between neighboring nucleobases appear at energies just above optically bright ^{1}ππ^{ast} excitonic states in aqueous solution. In double stranded DNA systems, both intrastrand and interstrand CT states are observed. It has been hypothesized that excitonic states may decay via a conical intersection into a CT state on a subpicosecond timescale. The proximity in energy of such states in out calculations appears consistent with this claim. Assuming that such a non-radiative mechanism occurs, we investigate subsequent relaxation of CT states by constructing and optimizing the geometry of model CT systems with constrained density functional theory (CDFT). We find that CT states relax in double stranded DNA through proton transfer across Watson-Crick base pairs with little to no energy barrier. Furthermore, the ground state energy shifts upwards along this reaction coordinate to nearly the same as that of the proton coupled charge transfer state, creating the possibility for a non-radiative pathway to the ground state. Q. Wu and T. Van Voorhis Phys. Rev. A (2005)

  8. Insulin and IR-beta in pig spermatozoa: a role of the hormone in the acquisition of fertilizing ability.

    PubMed

    Carpino, A; Rago, V; Guido, C; Casaburi, I; Aquila, S

    2010-06-01

    Recent studies have revealed that insulin, the main regulator of the glucose homeostasis in somatic cells, is expressed in human spermatozoa which are also able to secrete it. This study investigated the expression of insulin and insulin receptor beta in pig spermatozoa, at immunohistochemical protein and mRNA level. The immunofluorescence assay revealed that insulin and its receptor were co-localized in the sperm midpiece, while insulin was also detected in the acrosomal region. Western blot evidenced a 36 kDa band for insulin and a 95 kDa band for insulin receptor, such as reported in somatic cells. In addition, both insulin and insulin receptor transcripts were detected in pig spermatozoa. Interestingly, a possible biological role of the hormone was evidenced during pig sperm capacitation and acrosome reaction. In fact, the results showed that insulin (0.01 and 0.1 nm) can induce both the activities. A possible autocrine short loop of insulin in pig spermatozoa was suggested by the evaluation of the hormone secretion in both uncapacitated and capacitated spermatozoa. Furthermore, spontaneous sperm capacitation and acrosome reaction were stimulated by glucose and inhibited by the blockage of insulin release (nifedipine). In conclusion, this work has firstly demonstrated the expression of insulin and of its receptor, as well as the insulin secretion by pig spermatozoa, thereby suggesting an unexpected significance of the hormone in the acquisition of the male gamete fertilizing ability.

  9. Insulin Resistance and Prediabetes

    MedlinePlus

    ... especially sleep apnea; and cigarette smoking. Does sleep matter? Yes. Studies show that untreated sleep problems, especially ... a severe form of insulin resistance may have dark patches of skin, usually on the back of ...

  10. Insulin Delivery System

    NASA Technical Reports Server (NTRS)

    1988-01-01

    When Programmable Implantable Medication System (PIMS) is implanted in human body, it delivers precise programmed amounts of insulin over long periods of time. Mini-Med Technologies has been refining the Technologies since initial development at APL. The size of a hockey puck, and encased in titanium shell, PIMS holds about 2 1/2 teaspoons of insulin at a programmed basal rate. If a change in measured blood sugar level dictates a different dose, the patient can vary the amount of insulin delivered by holding a small radio transceiver over the implanted system and dialing in a specific program held in the PIMS computer memory. Insulin refills are accomplished approximately 4 times a year by hypodermic needle.

  11. Synaptotoxic amyloid-β oligomers: a molecular basis for the cause, diagnosis, and treatment of Alzheimer's disease?

    PubMed

    Klein, William L

    2013-01-01

    The oligomer hypothesis for Alzheimer's disease (AD)was introduced in 1998. It was based on evidence that oligomers could exist free of amyloid fibrils, that fibril-free oligomer solutions rapidly inhibited long term potentiation, and that oligomers ultimately caused a highly selective nerve cell death. Fibrils no longer were the only toxins made by amyloid-β (Aβ), and likely not the most important ones. Oligomers provided a new basis for instigating AD. Since introduction of the hypothesis, more than 1,500 articles on oligomers have been published. Articles for this review were selected for contributions to oligomer theory at three different levels. The first set demonstrated new aspects of oligomer pathobiology in cell models, showing that exposure of neurons to oligomers is sufficient to cause key features of AD neuropathology. The second set confirmed the relationship between oligomers and salient AD neuropathology in animal models, consistent with other in vivo studies that overall have substantiated cell-based discoveries. The third set developed strategies for therapeutic targeting of oligomers, introducing both small molecule and antibody-based approaches. These and related findings from many groups have helped establish oligomers as central to the mechanism of AD pathogenesis. Comprising a ligand-based attack on specific synapses, the action of toxic oligomers gives a molecular basis to account for key features of AD neuropathology and to explain why early disease targets memory. Although there still is no effective treatment for AD, insights over the past five years raise hopes that new approaches targeting Aβ oligomers could finally bring disease-modifying therapeutics.

  12. Erythrocyte Mr 28,000 transmembrane protein exists as a multisubunit oligomer similar to channel proteins.

    PubMed

    Smith, B L; Agre, P

    1991-04-05

    A novel Mr 28,000 erythrocyte transmembrane protein was recently purified and found to exist in two forms, "28kDa" and "gly28kDa," the latter containing N-linked carbohydrate (Denker, B. M., Smith, B. L., Kuhajda, F. P., and Agre, P. (1988) J. Biol. Chem. 263, 15634-15642). Although 28kDa protein resembles the Rh polypeptides biochemically, structural homologies were not identified by immunoblot or two-dimensional iodopeptide maps. The NH2-terminal amino acid sequence for the first 35 residues of purified 28kDa protein is 37% identical to the 26-kDa major intrinsic protein of lens (Gorin, M. B., Yancey, S. B., Cline, J., Revel, J.-P., and Horwitz, J. Cell 39, 49-59). Antisera to a synthetic peptide corresponding to the NH2-terminus of 28kDa protein gave a single reaction of molecular mass 28kDa on immunoblots of erythrocyte membranes. Selective digestions of intact erythrocytes and inside-out membrane vesicles with carboxypeptidase Y indicated the existence of a 5-kDa COOH-terminal cytoplasmic domain. Multiple studies indicated that 28kDa and gly28kDa proteins exist together as a multisubunit oligomer: 1) similar partial solubilizations in Triton X-100; 2) co-purification during ion exchange and lectin affinity chromatography; 3) cross-linking in low concentrations of glutaraldehyde; and 4) physical analyses of purified proteins and solubilized membranes in 1% (v/v) Triton X-100 showed 28kDa and gly28kDa proteins behave as a large single unit with Stokes radius of 61 A and sedimentation coefficient of 5.7 S. These studies indicate that the 28kDa and gly28kDa proteins are distinct from the Rh polypeptides and exist as a multisubunit oligomer. The 28kDa protein has NH2-terminal amino acid sequence homology and membrane organization similar to major intrinsic protein and other members of a newly recognized family of transmembrane channel proteins.

  13. The Adsorption of Short Single-Stranded DNA Oligomers on Mineral Surfaces

    NASA Astrophysics Data System (ADS)

    Kopstein, M.; Sverjensky, D. A.; Hazen, R. M.; Cleaves, H. J.

    2009-12-01

    Previous studies have described feasible pathways for the synthesis of simple organic building blocks such as formaldehyde and hydrogen cyanide, and their reaction to form more complex biomolecules such as nucleotide bases, amino acids and sugars (Miller and Orgel 1974, Miller and Cleaves 2006). However, the polymerization of monomers into a useful genetic material remains problematic (Orgel 2004). Organic building blocks were unlikely to polymerize from very dilute aqueous solution in the primitive oceans. Mineral surface adsorption has been suggested as a possible mechanism for concentrating the necessary building blocks (Bernal 1951). This study focused on the adsorption behavior of single-stranded DNA homo-oligomers of adenine and thymine (including the monomers, dimers, tetramers, hexamers, octomers, and decamers) with five different mineral surfaces (pyrite, rutile, hematite, olivine and calcite). Adsorption was studied in 0.1 M pH 8.1 KHCO3 with0.05 M NaCl as background electrolyte. Solutions were mixed for 24 hours at room temperature, centrifuged and the supernatants analyzed by UV/visible spectrophotometry. Equilibrium solution concentrations were measured and used to determine the number of moles adsorbed per square meter. Langmuir isotherms were constructed using the experimental data. It was found that adenine-containing molecules tend to bind much more strongly than thymine-containing molecules. It was also found that the number of moles adsorbed at saturation tends to fall with increasing chain length, while adsorption affinity tends to rise. Oligomer length appears to affect adsorption more than the mineral type. These results may have implications for the primordial organization of the first nucleic acid molecules as the persistence of extra-cellular nucleic acids in the environment. References Bernal, J. D. (1951) The Physical Basis of Life (Routledge, London). Miller S.L. and Cleaves, H.J. (2006) Prebiotic chemistry on the primitive Earth. In

  14. A pulse radiolysis study of zinc(II)-insulin.

    PubMed

    Elliot, A J; Wilkinson, F; Armstrong, D A

    1980-07-01

    Reactions of eaq with zinc(II)-insulin at pH 6.6 and 9.0 yielded relatively low disulphide anion absorptions, suggesting eaq reacts at other sites than S-S. A similar conclusion was reached for the reation of CO2 where an even lower yield of disulphide anion was found. However, here the disulphide anion yield increased with 'prepulsing'. Simultaneously the rate constant decreased, implying that a more reactive site was 'cleaned up'. While no reaction of Br2 with insulin was observed, both OH and Cl2 reacted rapidly and predominantly at the tyrosine residues. The second order rate constants, calculated in terms of insulin monomer concentrations, are reported for eaq, CO2 and Cl2. The transient spectra qualitatively support evidence regarding the accessibility of S-S bonds and tryosine residues in the various forms of insulin as predicted from earlier studies.

  15. Moving toward the ideal insulin for insulin pumps.

    PubMed

    Cengiz, Eda; Bode, Bruce; Van Name, Michelle; Tamborlane, William V

    2016-01-01

    Advances in insulin formulations have been important for diabetes management and achieving optimal glycemic control. Rapid-acting insulin analogs provide a faster time-action profile than regular insulin and are approved for use in pumps. However, the need remains for therapy to deliver a more physiologic insulin profile. New insulin formulations and delivery methods are in development, with the aim of accelerating insulin absorption to accomplish ultra-fast-acting insulin time-action profiles. Furthermore, the integration of continuous glucose monitoring with insulin pump therapy enables on-going adjustment of insulin delivery to optimize glycemic control throughout the day and night. These technological and pharmacological advances are likely to facilitate the development of closed-loop pump systems (i.e., artificial pancreas), and improve glycemic control and quality of life for patients with diabetes.

  16. Synthesis of carboxylated poly(NIPAAm) oligomers and their application to form thermo-reversible polymer-enzyme conjugates.

    PubMed

    Chen, G; Hoffman, A S

    1994-01-01

    A thermo-reversible poly(N-isopropylacrylamide) poly(NIPAAm) oligomer with a carboxyl functional end group has been synthesized by radical polymerization using beta-mercaptopropionic acid as a chain transfer reagent. This polymer has been conjugated to an enzyme, beta-D-glucosidase, to form a thermo-reversible water soluble-insoluble polymer-enzyme conjugate. This conjugate can be used for separation, recovery and recycle of an enzyme simply by applying small temperature changes to the reaction medium. In contrast to the random polymer-enzyme conjugates reported in the literature, in this study the enzyme is coupled to each polymer chain by a single end attachment. These preliminary studies show that the conjugated enzyme exhibits very high retention of activity (> 90%) compared to the native enzyme and shows improved thermal stability.

  17. From lignocellulosic biomass to lactic- and glycolic-acid oligomers: a gram-scale microwave-assisted protocol.

    PubMed

    Carnaroglio, Diego; Tabasso, Silvia; Kwasek, Beata; Bogdal, Dariusz; Gaudino, Emanuela Calcio; Cravotto, Giancarlo

    2015-04-24

    The conversion of lignocellulosic biomass into platform chemicals is the key step in the valorization of agricultural waste. Of the biomass-derived platform chemicals currently produced, lactic acid plays a particularly pivotal role in modern biorefineries as it is a versatile commodity chemical and building block for the synthesis of biodegradable polymers. Microwave-assisted processes that furnish lactic acid avoid harsh depolymerization conditions while cutting down reaction time and energy consumption. We herein report a flash catalytic conversion (2 min) of lignocellulosic biomass into lactic and glycolic acids under microwave irradiation. The batch procedure was successfully adapted to a microwave-assisted flow process (35 mL min(-1) ), with the aim of designing a scalable process with higher productivity. The C2 and C4 units recovered from the depolymerization were directly used as the starting material for a solvent and catalyst-free microwave-assisted polycondensation that afforded oligomers in good yields.

  18. Reactive Processing with Difunctional Oligomers to Increase Interfacial Adhesion in Polymer Blends

    NASA Astrophysics Data System (ADS)

    O'Brien, Charles; Rice+, Kevin; Dadmun, Mark

    2000-03-01

    The intoduction of blocky copolymers represents a possible method of compatibilizing two immiscible polymers in a blend. However, copolymers do not diffuse quickly to the interface of a polymer blend system. Therefore, reactive processing is being investigated as a means to form in-situ compatibilizers for polymer blends. A model system composed of poly(bisphenol A-co-epichlorohydrin) blended with poly(ethylene oxide) that is compatibilized with difunctional oligomers that are the same structure as the blend components is currently under investigation. It is expected that the oligomers can undergo an addition copolymerization during processing to create the blocky copolymers at the biphasic interface. Initial tensile measurements show that the addition of the reactive oligomers improves the properties of the blend. Additionally, preliminary results indicate that reactive oligomers may act as plasticizers and continue to polymerize at room temperature after the blend is removed from the melt mixer if insufficiently mixed.

  19. Enhanced Emission of Highly Labeled DNA Oligomers near Silver Metallic Surfaces

    PubMed Central

    Malicka, Joanna; Gryczynski, Ignacy; Lakowicz, Joseph R.

    2009-01-01

    Fluorescein is a widely used fluorescent probe in DNA analysis. One difficulty with fluorescein is its self-quenching due to resonance energy transfer between the residues, which results in decreased intensities with increasing labeling density. We examined the emission spectral properties of DNA oligomers labeled with one or five fluorescein residues. The emission intensity of the more highly labeled oligomer was decreased due to self-quenching. The self-quenching was mostly eliminated when this oligomer was held ~90 Å from the surface of metallic silver particles. The intensities increased 7- and 19-fold for the oligomers with one or five fluoresceins, respectively. The increased intensity did not result in increased photobleaching. These results suggest the use of substrates coated with silver particles for increased sensitivity on DNA arrays or for DNA analysis. PMID:14632044

  20. The Anti-Prion Antibody 15B3 Detects Toxic Amyloid-β Oligomers

    PubMed Central

    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

    2016-01-01

    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. Place of technosphere inhaled insulin in treatment of diabetes.

    PubMed

    Mikhail, Nasser

    2016-12-15

    Technosphere insulin (TI), Afrezza, is a powder form of short-acting regular insulin taken by oral inhalation with meals. Action of TI peaks after approximately 40-60 min and lasts for 2-3 h. TI is slightly less effective than subcutaneous insulin aspart, with mean hemoglobin A1c (HbA1c) reduction of 0.21% and 0.4%, respectively. When compared with technosphere inhaled placebo, the decrease in HbA1c levels was 0.8% and 0.4% with TI and placebo, respectively. Compared with insulin aspart, TI is associated with lower risk of late post-prandial hypoglycemia and weight gain. Apart from hypoglycemia, cough is the most common adverse effect of TI reported by 24%-33% of patients vs 2% with insulin aspart. TI is contraindicated in patients with asthma and chronic obstructive pulmonary disease. While TI is an attractive option of prandial insulin, its use is limited by frequent occurrence of cough, need for periodic monitoring of pulmonary function, and lack of long-term safety data. Candidates for use of TI are patients having frequent hypoglycemia while using short-acting subcutaneous insulin, particularly late post-prandial hypoglycemia, patients with needle phobia, and those who cannot tolerate subcutaneous insulin due to skin reactions.

  2. Place of technosphere inhaled insulin in treatment of diabetes

    PubMed Central

    Mikhail, Nasser

    2016-01-01

    Technosphere insulin (TI), Afrezza, is a powder form of short-acting regular insulin taken by oral inhalation with meals. Action of TI peaks after approximately 40-60 min and lasts for 2-3 h. TI is slightly less effective than subcutaneous insulin aspart, with mean hemoglobin A1c (HbA1c) reduction of 0.21% and 0.4%, respectively. When compared with technosphere inhaled placebo, the decrease in HbA1c levels was 0.8% and 0.4% with TI and placebo, respectively. Compared with insulin aspart, TI is associated with lower risk of late post-prandial hypoglycemia and weight gain. Apart from hypoglycemia, cough is the most common adverse effect of TI reported by 24%-33% of patients vs 2% with insulin aspart. TI is contraindicated in patients with asthma and chronic obstructive pulmonary disease. While TI is an attractive option of prandial insulin, its use is limited by frequent occurrence of cough, need for periodic monitoring of pulmonary function, and lack of long-term safety data. Candidates for use of TI are patients having frequent hypoglycemia while using short-acting subcutaneous insulin, particularly late post-prandial hypoglycemia, patients with needle phobia, and those who cannot tolerate subcutaneous insulin due to skin reactions. PMID:28031777

  3. Chemical syntheses of inhibitory substrates of the RNA-RNA ligation reaction catalyzed by the hairpin ribozyme.

    PubMed

    Massey, Archna P; Sigurdsson, Snorri Th

    2004-01-01

    The chemical syntheses of RNA oligomers containing modifications on the 5'-carbon of the 5'-terminal nucleoside for crystallographic and mechanistic studies of the hairpin ribozyme are reported. Phosphoramidites 4 and 8 were prepared and used in solid phase syntheses of RNA oligomers containing the sequence 5'-N'UCCUCUCC, where N' indicates either 5'-chloro-5'-deoxyguanosine or 5'-amino-5'-deoxyguanosine, respectively. A ribozyme ligation assay with the 5'-chloro- and 5'-amino-modified RNA oligomers demonstrated their inhibition of the hairpin-catalyzed RNA-RNA ligation reaction.

  4. Vesicle permeabilization by purified soluble oligomers of prion protein: a comparative study of the interaction of oligomers and monomers with lipid membranes.

    PubMed

    Chich, J-F; Chapuis, C; Henry, C; Vidic, J; Rezaei, H; Noinville, S

    2010-04-09

    The conversion of normal cellular prion protein (PrP) into its pathological isoform, scrapie PrP, may occur at the cell surface or, more probably, in late endosomes. The early events leading to the structural conversion of PrP appear to be related to the presence of more or less stable soluble oligomers, which might mediate neurotoxicity. In the current study, we investigate the interaction of alpha-rich PrP monomers and beta-rich size-exclusion-chromatography-purified PrP oligomers with lipid membranes. We compare their structural properties when associated with lipid bilayers and study their propensities to permeabilize the membrane at physiological pH. We also study the influence of the N-terminal flexible region (residues 24-103) by comparing full-length PrP(24-234) and N-terminally truncated PrP(104-234) oligomers. We showed that both 12-subunit oligomers cause an immediate and large increase in the permeability of the membrane, whereas equivalent amounts of monomeric forms cause no detectable leakage. Although the two monomeric PrP constructs undergo an alpha-to-beta conformational change when bound to the negatively charged membrane, only the full-length form of monomeric PrP has a weak fusogenic effect. Finally, the oligomers affect the integrity of the membrane differently from the monomers, independently of the presence of the N-terminal flexible domain. As for other forms of amyloidogenesis, a reasonable mechanism for the toxicity arising from PrP fibrillization must be associated with low-molecular-weight oligomeric intermediates, rather than with mature fibrils. Knowledge of the mechanism of action of these soluble oligomers would have a high impact on the development of novel therapeutic targets.

  5. Salt anions promote the conversion of HypF-N into amyloid-like oligomers and modulate the structure of the oligomers and the monomeric precursor state.

    PubMed

    Campioni, Silvia; Mannini, Benedetta; López-Alonso, Jorge P; Shalova, Irina N; Penco, Amanda; Mulvihill, Estefania; Laurents, Douglas V; Relini, Annalisa; Chiti, Fabrizio

    2012-12-07

    An understanding of the solution factors contributing to the rate of aggregation of a protein into amyloid oligomers, to the modulation of the conformational state populated prior to aggregation and to the structure/morphology of the resulting oligomers is one of the goals of present research in this field. We have studied the influence of six different salts on the conversion of the N-terminal domain of Escherichiacoli HypF (HypF-N) into amyloid-like oligomers under conditions of acidic pH. Our results show that salts having different anions (NaCl, NaClO(4), NaI, Na(2)SO(4)) accelerate oligomerization with an efficacy that follows the electroselectivity series of the anions (SO(4)(2-)≥ ClO(4)(-)>I(-)>Cl(-)). By contrast, salts with different cations (NaCl, LiCl, KCl) have similar effects. We also investigated the effect of salts on the structure of the final and initial states of HypF-N aggregation. The electroselectivity series does not apply to the effect of anions on the structure of the oligomers. By contrast, it applies to their effect on the content of secondary structure and on the exposure of hydrophobic clusters of the monomeric precursor state. The results therefore indicate that the binding of anions to the positively charged residues of HypF-N at low pH is the mechanism by which salts modulate the rate of oligomerization and the structure of the monomeric precursor state but not the structure of the resulting oligomers. Overall, the data contribute to rationalize the effect of salts on amyloid-like oligomer formation and to explain the role of charged biological macromolecules in protein aggregation processes.

  6. Bacterial Resistance to Antisense Peptide Phosphorodiamidate Morpholino Oligomers

    PubMed Central

    Puckett, Susan E.; Reese, Kaleb A.; Mitev, Georgi M.; Mullen, Valerie; Johnson, Rudd C.; Pomraning, Kyle R.; Mellbye, Brett L.; Tilley, Lucas D.; Iversen, Patrick L.; Freitag, Michael

    2012-01-01

    Peptide phosphorodiamidate morpholino oligomers (PPMOs) are synthetic DNA mimics that bind cRNA and inhibit bacterial gene expression. The PPMO (RFF)3RXB-AcpP (where R is arginine, F, phenylalanine, X is 6-aminohexanoic acid, B is β-alanine, and AcpP is acyl carrier protein) is complementary to 11 bases of the essential gene acpP (which encodes acyl carrier protein). The MIC of (RFF)3RXB-AcpP was 2.5 μM (14 μg/ml) in Escherichia coli W3110. The rate of spontaneous resistance of E. coli to (RFF)3RXB-AcpP was 4 × 10−7 mutations/cell division. A spontaneous (RFF)3RXB-AcpP-resistant mutant (PR200.1) was isolated. The MIC of (RFF)3RXB-AcpP was 40 μM (224 μg/ml) for PR200.1. The MICs of standard antibiotics for PR200.1 and W3110 were identical. The sequence of acpP was identical in PR200.1 and W3110. PR200.1 was also resistant to other PPMOs conjugated to (RFF)3RXB or peptides with a similar composition or pattern of cationic and nonpolar residues. Genomic sequencing of PR200.1 identified a mutation in sbmA, which encodes an active transport protein. In separate experiments, a (RFF)3RXB-AcpP-resistant isolate (RR3) was selected from a transposome library, and the insertion was mapped to sbmA. Genetic complementation of PR200.1 or RR3 with sbmA restored susceptibility to (RFF)3RXB-AcpP. Deletion of sbmA caused resistance to (RFF)3RXB-AcpP. We conclude that resistance to (RFF)3RXB-AcpP was linked to the peptide and not the phosphorodiamidate morpholino oligomer, dependent on the composition or repeating pattern of amino acids, and caused by mutations in sbmA. The data further suggest that (RFF)3R-XB PPMOs may be transported across the plasma membrane by SbmA. PMID:22985881

  7. Bacterial resistance to antisense peptide phosphorodiamidate morpholino oligomers.

    PubMed

    Puckett, Susan E; Reese, Kaleb A; Mitev, Georgi M; Mullen, Valerie; Johnson, Rudd C; Pomraning, Kyle R; Mellbye, Brett L; Tilley, Lucas D; Iversen, Patrick L; Freitag, Michael; Geller, Bruce L

    2012-12-01

    Peptide phosphorodiamidate morpholino oligomers (PPMOs) are synthetic DNA mimics that bind cRNA and inhibit bacterial gene expression. The PPMO (RFF)(3)RXB-AcpP (where R is arginine, F, phenylalanine, X is 6-aminohexanoic acid, B is β-alanine, and AcpP is acyl carrier protein) is complementary to 11 bases of the essential gene acpP (which encodes acyl carrier protein). The MIC of (RFF)(3)RXB-AcpP was 2.5 μM (14 μg/ml) in Escherichia coli W3110. The rate of spontaneous resistance of E. coli to (RFF)(3)RXB-AcpP was 4 × 10(-7) mutations/cell division. A spontaneous (RFF)(3)RXB-AcpP-resistant mutant (PR200.1) was isolated. The MIC of (RFF)(3)RXB-AcpP was 40 μM (224 μg/ml) for PR200.1. The MICs of standard antibiotics for PR200.1 and W3110 were identical. The sequence of acpP was identical in PR200.1 and W3110. PR200.1 was also resistant to other PPMOs conjugated to (RFF)(3)RXB or peptides with a similar composition or pattern of cationic and nonpolar residues. Genomic sequencing of PR200.1 identified a mutation in sbmA, which encodes an active transport protein. In separate experiments, a (RFF)(3)RXB-AcpP-resistant isolate (RR3) was selected from a transposome library, and the insertion was mapped to sbmA. Genetic complementation of PR200.1 or RR3 with sbmA restored susceptibility to (RFF)(3)RXB-AcpP. Deletion of sbmA caused resistance to (RFF)(3)RXB-AcpP. We conclude that resistance to (RFF)(3)RXB-AcpP was linked to the peptide and not the phosphorodiamidate morpholino oligomer, dependent on the composition or repeating pattern of amino acids, and caused by mutations in sbmA. The data further suggest that (RFF)(3)R-XB PPMOs may be transported across the plasma membrane by SbmA.

  8. Amyloid-β Oligomers Transiently Inhibit AMP-activated kinase and Cause Metabolic Defects in Hippocampal Neurons.

    PubMed

    Seixas da Silva, Gisele S; Melo, Helen M; Lourenco, Mychael V; Lyra E Silva, Natalia de M; de Carvalho, Marcelo B; Alves-Leon, Soniza; de Souza, Jorge M; Klein, William L; da-Silva, Wagner S; Ferreira, Sergio T; De Felice, Fernanda G

    2017-03-16

    AMP-activated kinase (AMPK) is a key player in energy sensing and metabolic reprogramming under cellular energy restriction. Several studies have linked impaired AMPK function to peripheral metabolic diseases such as diabetes. However, the impact of neurological disorders, such as Alzheimer disease (AD), on AMPK function and downstream effects of altered AMPK activity on neuronal metabolism have been investigated only recently. Here, we report the impact of A β oligomers (AβOs), synaptotoxins that accumulate in AD brains, on neuronal AMPK activity. Short-term exposure of cultured rat hippocampal neurons or ex vivo human cortical slices to AβOs transiently decreased intracellular ATP levels and AMPK activity, as evaluated by its phosphorylation at threonine residue 172 (AMPKpThr172). The AβO-dependent reduction in AMPKpThr172 levels was mediated by glutamate receptors of the N-methyl-D-aspartate (NMDA) subtype, and resulted in removal of glucose transporters (GLUTs) from the surfaces of dendritic processes in hippocampal neurons. Importantly, insulin prevented the AβO-induced inhibition of AMPK. Our results establish a novel toxic impact of A βOs on neuronal metabolism and suggest that AβO-induced, NMDA receptor-mediated AMPK inhibition may play a key role in early brain metabolic defects in AD.

  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. Soluble Prion Protein Binds Isolated Low Molecular Weight Amyloid-β Oligomers Causing Cytotoxicity Inhibition.

    PubMed

    Williams, Thomas L; Choi, Jin-Kyu; Surewicz, Krystyna; Surewicz, Witold K

    2015-12-16

    A growing number of observations indicate that soluble amyloid-β (Aβ) oligomers play a major role in Alzheimer's disease. Recent studies strongly suggest that at least some of the neurotoxic effects of these oligomers are mediated by cellular, membrane-anchored prion protein and that Aβ neurotoxicity can be inhibited by soluble recombinant prion protein (rPrP) and its fragments. However, the mechanism by which rPrP interacts with Aβ oligomers and prevents their toxicity is largely unknown, and studies in this regard are hindered by the large structural heterogeneity of Aβ oligomers. To overcome this difficulty, here we used photoinduced cross-linking of unmodified proteins (PICUP) to isolate well-defined oligomers of Aβ42 and characterize these species with regard to their cytotoxicity and interaction with rPrP, as well the mechanism by which rPrP inhibits Aβ42 cytotoxicity. Our data shows that the addition of rPrP to the assembling Aβ42 results in a shift in oligomer size distribution, decreasing the population of toxic tetramers and higher order oligomers and increasing the population of nontoxic (and possibly neuroprotective) monomers. Isolated oligomeric species of Aβ42 are cytotoxic to primary neurons and cause permeation of model lipid bilayers. These toxic effects, which are oligomer size-dependent, can be inhibited by the addition of rPrP, and our data suggest potential mechanisms of this inhibitory action. This insight should help in current efforts to develop PrP-based therapeutics for Alzheimer's disease.

  11. Oligomer formation of the gB glycoprotein of herpes simplex virus type 1.

    PubMed Central

    Highlander, S L; Goins, W F; Person, S; Holland, T C; Levine, M; Glorioso, J C

    1991-01-01

    Oligomer formation of the gB glycoprotein of herpes simplex virus type 1 was studied by sedimentation analysis of radioactively labeled infected cell and virion lysates. Fractions from sucrose gradients were precipitated with a pool of gB-specific monoclonal antibodies and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Pulse-labeled gB from infected cell was synthesized as monomers and converted to oligomers posttranslationally. The oligomers from infected cells and from virions sedimented as dimers, and there was no evidence of higher-molecular-weight forms. To identify amino acid sequences of gB that contribute to oligomer formation, pairs of mutant plasmids were transfected into Vero cells and superinfected with a gB-null mutant virus to stimulate plasmid-specified gene expression. Radioactively labeled lysates were precipitated with antibodies and examined by SDS-PAGE. Polypeptides from cotransfections were precipitated with an antibody that recognized amino acid sequences present in only one of the two polypeptides. A coprecipitated polypeptide lacking the antibody target epitope was presumed to contain the sequences necessary for oligomer formation. Using this technique, two noncontiguous sites for oligomer formation were detected. An upstream site was localized between residues 93 and 282, and a downstream site was localized between residues 596 and 711. Oligomer formation resulted from molecular interactions between two upstream sites, between two downstream sites, and between an upstream and a downstream site. A schematic diagram of a gB oligomer is presented that is consistent with these data. Images PMID:1649330

  12. KCTD Hetero-oligomers Confer Unique Kinetic Properties on Hippocampal GABAB Receptor-Induced K+ Currents.

    PubMed

    Fritzius, Thorsten; Turecek, Rostislav; Seddik, Riad; Kobayashi, Hiroyuki; Tiao, Jim; Rem, Pascal D; Metz, Michaela; Kralikova, Michaela; Bouvier, Michel; Gassmann, Martin; Bettler, Bernhard

    2017-02-01

    GABAB receptors are the G-protein coupled receptors for the main inhibitory neurotransmitter in the brain, GABA. GABAB receptors were shown to associate with homo-oligomers of auxiliary KCTD8, KCTD12, KCTD12b, and KCTD16 subunits (named after their T1 K(+)-channel tetramerization domain) that regulate G-protein signaling of the receptor. Here we provide evidence that GABAB receptors also associate with hetero-oligomers of KCTD subunits. Coimmunoprecipitation experiments indicate that two-thirds of the KCTD16 proteins in the hippocampus of adult mice associate with KCTD12. We show that the KCTD proteins hetero-oligomerize through self-interacting T1 and H1 homology domains. Bioluminescence resonance energy transfer measurements in live cells reveal that KCTD12/KCTD16 hetero-oligomers associate with both the receptor and the G-protein. Electrophysiological experiments demonstrate that KCTD12/KCTD16 hetero-oligomers impart unique kinetic properties on G-protein-activated Kir3 currents. During prolonged receptor activation (one min) KCTD12/KCTD16 hetero-oligomers produce moderately desensitizing fast deactivating K(+) currents, whereas KCTD12 and KCTD16 homo-oligomers produce strongly desensitizing fast deactivating currents and nondesensitizing slowly deactivating currents, respectively. During short activation (2 s) KCTD12/KCTD16 hetero-oligomers produce nondesensitizing slowly deactivating currents. Electrophysiological recordings from hippocampal neurons of KCTD knock-out mice are consistent with these findings and indicate that KCTD12/KCTD16 hetero-oligomers increase the duration of slow IPSCs. In summary, our data demonstrate that simultaneous assembly of distinct KCTDs at the receptor increases the molecular and functional repertoire of native GABAB receptors and modulates physiologically induced K(+) current responses in the hippocampus.

  13. Mouse models of insulin resistance.

    PubMed

    Hribal, Marta Letizia; Oriente, Francesco; Accili, Domenico

    2002-05-01

    The hallmarks of type 2 diabetes are impaired insulin action in peripheral tissues and decreased pancreatic beta-cell function. Classically, the two defects have been viewed as separate entities, with insulin resistance arising primarily from impaired insulin-dependent glucose uptake in skeletal muscle, and beta-cell dysfunction arising from impaired coupling of glucose sensing to insulin secretion. Targeted mutagenesis and transgenesis involving components of the insulin action pathway have changed our understanding of these phenomena. It appears that the role of insulin signaling in the pathogenesis of type 2 diabetes has been overestimated in classic insulin target tissues, such as skeletal muscle, whereas it has been overlooked in liver, pancreatic beta-cells, and brain, which had been thought not to be primary insulin targets. We review recent progress and try to reconcile areas of apparent controversy surrounding insulin signaling in skeletal muscle and pancreatic beta-cells.

  14. Lignin chemistry: biosynthetic study and structural characterisation of coniferyl alcohol oligomers formed in vitro in a micellar environment.

    PubMed

    Reale, Samantha; Attanasio, Francesca; Spreti, Nicoletta; De Angelis, Francesco

    2010-05-25

    Model coniferyl alcohol lignin (the so-called dehydrogenative polymerisate, DHP) was produced in water under homogeneous conditions guaranteed by the presence of a micellised cationic surfactant. A complete study of the activity of the enzymatic system peroxidase/H(2)O(2) under our reaction conditions was reported and all the reaction products up to the pentamer were characterised by (1)H NMR spectroscopy and ESI mass spectrometry. Our system, and the molecules that have been generated in it, represent a closer mimicry of the natural microenvironment since an enzyme, under micellar conditions, reproduces the cell system better than in buffer alone. On the basis of the oligomers structures a new biosynthetic perspective was proposed that focused attention on a coniferyl alcohol dimeric quinone methide as the key intermediate of the reaction. A formal, strictly alternate sequence of a radical and an ionic step underlines the reaction, thus generating ordered oligolignols structures. Alternatively to other model lignins, our olignols present a lower degree of radical coupling between oligomeric units. This offers a closer biosynthetic situation to the observation of a low rate of radical generation in the cell wall.

  15. Oligomers of the amyloid-beta protein disrupt working memory: confirmation with two behavioral procedures.

    PubMed

    Poling, Alan; Morgan-Paisley, Kineta; Panos, John J; Kim, Eun-Mee; O'Hare, Eugene; Cleary, James P; Lesné, Sylvain; Ashe, Karen H; Porritt, Matthew; Baker, Lisa E

    2008-11-21

    Converging lines of evidence suggest that oligomers of amyloid-beta play a role in the cognitive impairment characteristic of Alzheimer's disease, but only three studies have provided experimental evidence of such impairment. To provide additional information about the effects of these oligomers on memory, the present study examined the memory of groups of rats exposed to ICV injections of the culture media (CM) of Chinese Hamster Ovary cells that were (7PA2) and were not (CHO-) transfected with a human mutation of amyloid precursor protein that appears to cause early-onset Alzheimer's disease. The 7PA2 CM, which contained concentrations of soluble amyloid-beta oligomers physiologically relevant to those found in human brain, significantly disrupted working memory in rats tested in a radial-arm maze. In contrast, CHO- CM, which did not contain such oligomers, had no effect on memory. The disruptive effects of 7PA2-derived amyloid-beta oligomers, evident 2h after exposure, disappeared within a day. These findings are compared to results from 7PA2 CM tested under a complex procedure thought to measure aspects of executive function. The results confirm the disruptive effects of low-n amyloid-beta oligomers and extend them to a well-established rat model of memory.

  16. 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

    2016-05-04

    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.

  17. 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.

  18. 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.

  19. π-Conjugated Discrete Oligomers Containing Planar and Nonplanar Aromatic Motifs.

    PubMed

    Li, Ji; Terec, Anamaria; Wang, Yue; Joshi, Hrishikesh; Lu, Yunpeng; Sun, Handong; Stuparu, Mihaiela C

    2017-03-01

    A new family of π-conjugated oligomers featuring a nonplanar polycyclic aromatic hydrocarbon, corannulene, and a planar aromatic unit, thiophene, is synthesized through an iterative metal-catalyzed coupling protocol. The two structural motifs are connected through an acetylene linkage. In the shorter oligomers, a thiophene unit is attached to one or two corannulenes. In the higher analogues, two, three, and four thiophene units are placed in an alternating fashion with three, four, and five corannulene units, respectively. Photophysical studies reveal extended π-effects that initially increase and then attenuate as a function of the oligomer length. Notably, longer oligomers are found to be highly active for nonlinear absorption and emission properties. The oligomer with three corannulene and two thiophene units exhibits a two-photon absorption cross section of 600 GM and two-photon-excited intense green luminescence. This work, therefore, introduces the concept of combining planar and nonplanar aromatic motifs in the design of π-conjugated discrete oligomers, establishes synthetic feasibility of such hybrid materials, reports on their photophysical properties that is anticipated to have significant implications for future research targets, and features the discovery that corannulene derivatives can exhibit excellent nonlinear optical activity when extended through π-bridges.

  20. α-Synuclein Oligomers Induced by Docosahexaenoic Acid Affect Membrane Integrity

    PubMed Central

    Fecchio, Chiara; De Franceschi, Giorgia; Relini, Annalisa; Greggio, Elisa; Dalla Serra, Mauro; Bubacco, Luigi; Polverino de Laureto, Patrizia

    2013-01-01

    A key feature of Parkinson disease is the aggregation of α-synuclein and its intracellular deposition in fibrillar form. Increasing evidence suggests that the pathogenicity of α-synuclein is correlated with the activity of oligomers formed in the early stages of its aggregation process. Oligomers toxicity seems to be associated with both their ability to bind and affect the integrity of lipid membranes. Previously, we demonstrated that α-synuclein forms oligomeric species in the presence of docosahexaenoic acid and that these species are toxic to cells. Here we studied how interaction of these oligomers with membranes results in cell toxicity, using cellular membrane-mimetic and cell model systems. We found that α-synuclein oligomers are able to interact with large and small unilamellar negatively charged vesicles acquiring an increased amount of α-helical structure, which induces small molecules release. We explored the possibility that oligomers effects on membranes could be due to pore formation, to a detergent-like effect or to fibril growth on the membrane. Our biophysical and cellular findings are consistent with a model where α-synuclein oligomers are embedded into the lipid bilayer causing transient alteration of membrane permeability. PMID:24312431

  1. Effect of Zn(2+) ions on the assembly of amylin oligomers: insight into the molecular mechanisms.

    PubMed

    Wineman-Fisher, Vered; Miller, Yifat

    2016-08-03

    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.

  2. II - Insulin processing in mitochondria.

    PubMed

    Camberos, María Del Carmen; Pérez, Adriana A; Passicot, Gisel A; Martucci, Lucía C; Wanderley, María I; Udrisar, Daniel P; Cresto, Juan C

    2016-10-01

    Our objective was to know how insulin is processing in mitochondria; if IDE is the only participant in mitochondrial insulin degradation and the role of insulin degradation on IDE accumulation in mitoplasts. Mitochondria and its fractions were isolated as described by Greenwalt. IDE was purified and detected in immunoblot with specific antibodies. High insulin degradation was obtained through addition to rat's diet of 25 g/rat of apple and 10 g/rat of hard-boiled eggs, 3 days a week. Mitochondrial insulin degradation was assayed with 5 % TCA, insulin antibody or Sephadex G50 chromatography. Degradation was also assayed 60 min at 37 °C in mitochondrial fractions (IMS and Mx) with diet or not and without IDE. Degradation in fractions precipitated with ammonium sulfates (60-80 %) were studied after mitochondrial insulin incubation (1 ng. insulin during 15 min, at 30 °C) or with addition of 2.5 mM ATP. Supplementary diet increased insulin degradation. High insulin did not increase mitoplasts accumulation and did not decrease mitochondrial degradation. High insulin and inhibition of degradation evidence insulin competition for a putative transport system. Mitochondrial incubation with insulin increased IDE in matrix as observed in immunoblot. ATP decreased degradation in Mx and increased it in IMS. Chromatography of IMS demonstrated an ATP-dependent protease that degraded insulin, similar to described by Sitte et al. Mitochondria participate in insulin degradation and the diet increased it. High insulin did not accomplish mitochondrial decrease of degradation or its accumulation in mitoplasts. Mitochondrial incubation with insulin increased IDE in matrix. ATP suggested being a regulator of mitochondrial insulin degradation.

  3. Clay-mediated reactions of HCN oligomers - The effect of the oxidation state of the clay

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Alwis, K. W.; Edelson, E. H.; Mount, N.; Hagan, W. J., Jr.

    1981-01-01

    Montmorillonite clays which contain Fe(III) inhibit the oligomerization of aqueous solutions of HCN. The inhibitory effect is due to the rapid oxidation of diaminomaleonitrile, a key intermediate in HCN oligomerization, by the Fe(III) incorporated into the aluminosilicate lattice of the clay. The Fe(III) oxidizes diaminomaleonitrile to diiminosuccinonitrile, a compound which is rapidly hydrolyzed to HCN and oxalic acid derivatives. Diaminomaleonitrile is not oxidized when Fe(III) in the montmorillonite is reduced with hydrazine. The oxidation state of the clay is an important variable in experiments designed to simulate clay catalysis on the primitive earth.

  4. Cyclen-based lipidic oligomers as potential gene delivery vehicles.

    PubMed

    Yi, Wen-Jing; Zhang, Qin-Fang; Zhang, Ji; Liu, Qiang; Ren, Laifeng; Chen, Qian-Ming; Guo, Liandi; Yu, Xiao-Qi

    2014-03-01

    A series of cyclen-based linear oligomers bearing hydrophobic long chains (lipopolymers Cy-LC, where Cy and LC represent cyclen-based linear backbone and hydrophobic long chain substituents, respectively) were designed and synthesized. The effects of type and degree of substitution (DS) of hydrophobic long chains on the transfection efficiency were systematically studied. The nitrogen atoms with relatively strong basicity on the cyclen ensure their good DNA binding ability, which was confirmed by gel retardation and ethidium bromide exclusion assays. Lipopolyplexes could be formed as nanoparticles with suitable sizes and zeta potentials for gene transfection. In vitro gene delivery experiments revealed that the linoleic acid (LIN) substituted material Cy-LIN has better transfection efficiency than 25 kDa polyethylenimine in the absence or in the presence of serum. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and hemolysis assays showed low cytotoxicity and good biocompatibility of the lipopolyplexes. Fluorescent labeled DNA was used to study the cellular uptake and intracellular distribution of transfected DNA. Flow cytometry results suggested that a long chain is necessary for efficient cellular uptake, and images from confocal laser scanning microscopy showed that after 4h transfection, most of the fluorescent labeled DNA accumulated in the perinuclear region, which was required for efficient gene expression. Moreover, it was also found that the DS of the hydrophobic moiety can adjust the balance between DNA binding ability and dissociation of polyplexes, significantly affecting the transfection efficiency.

  5. Structure and stability of oligomer/α-cyclodextrin inclusion complexes.

    NASA Astrophysics Data System (ADS)

    Hunt, Marcus; Villar, Silvia; Gomez, Marian; Tonelli, Alan; Balik, Maury

    2007-03-01

    Cyclomaltohexaose (α-cyclodextrin, α-CD) can form inclusion complexes (ICs) with polymer molecules in the columnar crystal in which α-CD molecules stack to form a molecular tube. Complementary water vapor sorption and wide-angle X-ray diffractomery (WAXD) were performed on oligomer/α-CD ICs to probe their structures and stabilities. To discern the effect of guest molecule hydrophobicity on water adsorption isotherms, polyethylene glycol (PEG, MW = 600 g/mol) and hexatriacontane (HTC) guests were used. Sorption isotherms for PEG/α-CD IC are similar to those obtained for pure α-CD and PEG, suggesting the presence of dethreaded PEG in the sample. WAXD collected before and after water vapor sorption of PEG/α-CD IC indicated a partial conversion from columnar to cage crystal structure, the thermodynamically preferred structure for pure α-CD, due to dethreading of PEG. This behavior does not occur for HTC/α-CD IC. Sorption isotherms collected at 20, 30, 40 and 50 C allowed the calculation of differential heats of adsorption and integral entropies of adsorbed water, while solid-state ^13C NMR suggested a dramatic increase in HTC and α-CD mobilities upon complexation.

  6. Unique copper-induced oligomers mediate alpha-synuclein toxicity.

    PubMed

    Wright, Josephine A; Wang, Xiaoyan; Brown, David R

    2009-08-01

    Parkinson's disease and a number of other neurodegenerative diseases have been linked to either genetic mutations in the alpha-synuclein gene or show evidence of aggregates of the alpha-synuclein protein, sometimes in the form of Lewy bodies. There currently is no clear evidence of a distinct neurotoxic species of alpha-synuclein to explain the death of neurons in these diseases. We undertook to assess the toxicity of alpha-synuclein via exogenous application in cell culture. Initially, we showed that only aggregated alpha-synuclein is neurotoxic and requires the presence copper but not iron. Other members of the synuclein family showed no toxicity in any form and inherited point mutations did not alter the effective toxic concentration of alpha-synuclein. Through protein fractionation techniques, we were able to isolate an oligomeric species responsible for the toxicity of alpha-synuclein. This oligomeric species has a unique stellate appearance under EM and again, requires association with copper to induce cell death. The results allow us to suggest that the toxic species of alpha-synuclein in vivo could possibly be these stellate oligomers and not fibrils. Our data provide a link between the recently noted association of copper and alpha-synuclein and a potential role for the combination in causing neurodegeneration.

  7. 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

  8. 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

  9. HAMLET forms annular oligomers when deposited with phospholipid monolayers.

    PubMed

    Baumann, Anne; Gjerde, Anja Underhaug; Ying, Ming; Svanborg, Catharina; Holmsen, Holm; Glomm, Wilhelm R; Martinez, Aurora; Halskau, Oyvind

    2012-04-20

    Recently, the anticancer activity of human α-lactalbumin made lethal to tumor cells (HAMLET) has been linked to its increased membrane affinity in vitro, at neutral pH, and ability to cause leakage relative to the inactive native bovine α-lactalbumin (BLA) protein. In this study, atomic force microscopy resolved membrane distortions and annular oligomers (AOs) produced by HAMLET when deposited at neutral pH on mica together with a negatively charged lipid monolayer. BLA, BAMLET (HAMLET's bovine counterpart) and membrane-binding Peptide C, corresponding to BLA residues 75-100, also form AO-like structures under these conditions but at higher subphase concentrations than HAMLET. The N-terminal Peptide A, which binds to membranes at acidic but not at neutral pH, did not form AOs. This suggests a correlation between the capacity of the proteins/peptides to integrate into the membrane at neutral pH-as observed by liposome content leakage and circular dichroism experiments-and the formation of AOs, albeit at higher concentrations. Formation of AOs, which might be important to HAMLET's tumor toxic action, appears related to the increased tendency of the protein to populate intermediately folded states compared to the native protein, the formation of which is promoted by, but not uniquely dependent on, the oleic acid molecules associated with HAMLET.

  10. Carboxybetaine methacrylate oligomer modified nylon for circulating tumor cells capture.

    PubMed

    Dong, Chaoqun; Wang, Huiyu; Zhang, Zhuo; Zhang, Tao; Liu, Baorui

    2014-10-15

    Circulating tumor cells (CTC) capture is one of the most effective approaches in diagnosis and treatment of cancers in the field of personalized cancer medicine. In our study, zwitterionic carboxybetaine methacrylate (CBMA) oligomers were grafted onto nylon via atomic transfer random polymerization (ATRP) which would serve as a novel material for the development of convenient CTC capture interventional medical devices. The chemical, physical and biological properties of pristine and modified nylon surfaces were assessed by Fourier transform infrared spectra, atomic force microscope, water contact angle measurements, X-ray photoelectron spectroscopy, protein adsorption, platelet adhesion, and plasma recalcification time (PRT) determinations, etc. The results, including the significant decrease of proteins adsorption and platelets adhesion, as well as prolonged PRTs demonstrated the extraordinary biocompatibility and blood compatibility of the modified surface. Furthermore, we showed that upon immobilization of anti-epithelial cell adhesion molecular (anti-EpCAM) antibody onto the CBMA moiety, the modified nylon surface can selectively capture EpCAM positive tumor cells from blood with high efficiency, indicating the potential of the modified nylon in the manufacture of convenient interventional CTC capture medical devices.

  11. Cloud forming potential of oligomers relevant to secondary organic aerosols

    NASA Astrophysics Data System (ADS)

    Xu, Wen; Guo, Song; Gomez-Hernandez, Mario; Zamora, Misti L.; Secrest, Jeremiah; Marrero-Ortiz, Wilmarie; Zhang, Annie L.; Collins, Don R.; Zhang, Renyi

    2014-09-01

    The hygroscopic growth factor (HGF) and cloud condensation nuclei (CCN) activity are measured for surrogates that mimic atmospherically relevant oligomers, including glyoxal trimer dihydrate, methyl glyoxal trimer dihydrate, sucrose, methyl glyoxal mixtures with sulfuric acid and glycolic acid, and 2,4-hexandienal mixtures with sulfuric acid and glycolic acid. For the single-component aerosols, the measured HGF ranges from 1.3 to 1.4 at a relative humidity of 90%, and the hygroscopicity parameter (κ) is in the range of 0.06 to 0.19 on the basis of the measured CCN activity and 0.13 to 0.22 on the basis of the measured HGF, compared to the calculated values of 0.08 to 0.16. Large differences exist in the κ values derived using the measured HGF and CCN data for the multi-component aerosols. Our results reveal that, in contrast to the oxidation process, oligomerization decreases particle hygroscopicity and CCN activity and provides guidance for analyzing the organic species in ambient aerosols.

  12. Molecular Mechanisms of Insulin Secretion and Insulin Action.

    ERIC Educational Resources Information Center

    Flatt, Peter R.; Bailey, Clifford J.

    1991-01-01

    Information and current ideas on the factors regulating insulin secretion, the mechanisms underlying the secretion and biological actions of insulin, and the main characteristics of diabetes mellitus are presented. (Author)

  13. Intracellular soluble α‐synuclein oligomers reduce pyramidal cell excitability

    PubMed Central

    Kaufmann, Timothy J.; Harrison, Paul M.; Richardson, Magnus J. E.; Pinheiro, Teresa J. T.

    2016-01-01

    Key points The presynaptic protein α‐synuclein forms aggregates during Parkinson's disease.Accumulating evidence suggests that the small soluble oligomers of α‐synuclein are more toxic than the larger aggregates appearing later in the disease.The link between oligomer toxicity and structure still remains unclear.In the present study, we have produced two structurally‐defined oligomers that have a similar morphology but differ in secondary structure.These oligomers were introduced into neocortical pyramidal cells during whole‐cell recording and, using a combination of experimentation and modelling, electrophysiological parameters were extracted.Both oligomeric species had similar effects on neuronal properties reducing input resistance, time constant and increasing capacitance. The net effect was a marked reduction in neuronal excitability that could impact on network activity. Abstract The presynaptic protein α‐synuclein (αSyn) aggregates during Parkinson's disease (PD) to form large proteinaceous amyloid plaques, the spread of which throughout the brain clinically defines the severity of the disease. During early stages of aggregation, αSyn forms soluble annular oligomers that show greater toxicity than much larger fibrils. These oligomers produce toxicity via a number of possible mechanisms, including the production of pore‐forming complexes that permeabilize membranes. In the present study, two well‐defined species of soluble αSyn oligomers were produced by different protocols: by polymerization of monomer and by sonication of fibrils. The two oligomeric species produced were morphologically similar, with both having an annular structure and consisting of approximately the same number of monomer subunits, although they differed in their secondary structure. Oligomeric and monomeric αSyn were injected directly into the soma of pyramidal neurons in mouse neocortical brain slices during whole‐cell patch clamp recording. Using a combined

  14. Insulin Aspart (rDNA Origin) Injection

    MedlinePlus

    ... unless it is used in an external insulin pump. In patients with type 2 diabetes, insulin aspart ... also can be used with an external insulin pump. Before using insulin aspart in a pump system, ...

  15. Synthesis of molecular wires of linear and branched bis(terpyridine)-complex oligomers and electrochemical observation of through-bond redox conduction.

    PubMed

    Nishimori, Yoshihiko; Kanaizuka, Katsuhiko; Murata, Masaki; Nishihara, Hiroshi

    2007-03-05

    Films of linear and branched oligomer wires of Fe(tpy)2 (tpy = 2,2':6',2''-terpyridine) were constructed on a gold-electrode surface by the interfacial stepwise coordination method, in which a surface-anchoring ligand, (tpy-C6H4N=NC6H4-S)2 (1), two bridging ligands, 1,4-(tpy)2C6H4 (3) and 1,3,5-(C[triple bond]C-tpy)3C6H3 (4), and metal ions were used. The quantitative complexation of the ligands and Fe(II) ions was monitored by electrochemical measurements in up to eight complexation cycles for linear oligomers of 3 and in up to four cycles for branched oligomers of 4. STM observation of branched oligomers at low surface coverage showed an even distribution of nanodots of uniform size and shape, which suggests the quantitative formation of dendritic structures. The electron-transport mechanism and kinetics for the redox reaction of the films of linear and branched oligomer wires were analyzed by potential-step chronoamperometry (PSCA). The unique current-versus-time behavior observed under all conditions indicates that electron conduction occurs not by diffusional motion but by successive electron hopping between neighboring redox sites within a molecular wire. Redox conduction in a single molecular wire in a redox-polymer film has not been reported previously. The analysis provided the rate constant for electron transfer between the electrode and the nearest redox-complex moiety, k1 (s(-1)), as well as that for intrawire electron transfer between neighboring redox-complex moieties, k2 (cm2 mol(-1) s(-1)). The strong effect of the electrolyte concentration on both k1 and k2 indicates that the counterion motion limits the electron-hopping rate at lower electrolyte concentrations. Analysis of the dependence of k1 and k2 on the potential gave intrinsic kinetic parameters without overpotential effects: (k1(0) = 110 s(-1), k2(0) = 2.6x10(12) cm2 mol(-1) s(-1) for [n Fe3], and k1(0) = 100 s(-1), k2(0) = 4.1x10(11) cm2 mol(-1) s(-1) for [n Fe4] (n = number of complexation

  16. Novel demonstration of amyloid-β oligomers in sporadic inclusion-body myositis muscle fibers.

    PubMed

    Nogalska, Anna; D'Agostino, Carla; Engel, W King; Klein, William L; Askanas, Valerie

    2010-11-01

    Accumulation of amyloid-β (Aβ) within muscle fibers has been considered an upstream step in the development of the s-IBM pathologic phenotype. Aβ42, which is considered more cytotoxic than Aβ40 and has a higher propensity to oligomerize, is preferentially increased in s-IBM muscle fibers. In Alzheimer disease (AD), low-molecular weight Aβ oligomers and toxic oligomers, also referred to as "Aβ-Derived Diffusible Ligands" (ADDLs), are considered strongly cytotoxic and proposed to play an important pathogenic role. ADDLs have been shown to be increased in AD brain. We now report for the first time that in s-IBM muscle biopsies Aβ-dimer, -trimer, and -tetramer are identifiable by immunoblots. While all the s-IBM samples we studied had Aβ-oligomers, their molecular weights and intensity varied between the patient samples. None of the control muscle biopsies had Aβ oligomers. Dot-immunoblots using highly specific anti-ADDL monoclonal antibodies also showed highly increased ADDLs in all s-IBM biopsies studied, while controls were negative. By immunofluorescence, in some of the abnormal s-IBM muscle fibers ADDLs were accumulated in the form of plaque-like inclusions, and were often increased diffusely in very small fibers. Normal and disease-controls were negative. By gold-immuno-electron microscopy, ADDL-immunoreactivities were in close proximity to 6-10 nm amyloid-like fibrils, and also were immunodecorating amorphous and floccular material. In cultured human muscle fibers, we found that inhibition of autophagy led to the accumulation of Aβ oligomers. This novel demonstration of Aβ42 oligomers in s-IBM muscle biopsy provides additional evidence that intra-muscle fiber accumulation of Aβ42 oligomers in s-IBM may contribute importantly to s-IBM pathogenic cascade.

  17. Discrete Molecular Dynamics Study of Oligomer Formation by N-Terminally Truncated Amyloid β-Protein

    PubMed Central

    Meral, Derya; Urbanc, Brigita

    2013-01-01

    In Alzheimer’s disease (AD), amyloid β-protein (Aβ) self–assembles into toxic oligomers. Of the two predominant Aβ alloforms, Aβ1–40 and Aβ1–42, the latter is particularly strongly linked to AD. N-terminally truncated and pyroglutamated Aβ peptides were recently shown to seed Aβ aggregation and contribute significantly to Aβ–mediated toxicity, yet their folding and assembly were not explored computationally. Discrete molecular dynamics (DMD) approach previously captured in vitro–derived distinct Aβ1–40 and Aβ1–42 oligomer size distributions and predicted that the more toxic Aβ1–42 oligomers had more flexible and solvent exposed N-termini than Aβ1–40 oligomers. Here, we examined oligomer formation of Aβ3–40, Aβ3–42, Aβ11–40, and Aβ11–42 by the DMD approach. The four N-terminally truncated peptides showed increased oligomerization propensity relative to the full–length peptides, consistent with in vitro findings. Conformations formed by Aβ3–40/42 had significantly more flexible and solvent–exposed N-termini than Aβ1–40/42 conformations. In contrast, in Aβ11–40/42 conformations the N-termini formed more contacts and were less accessible to the solvent. The compactness of the Aβ11–40/42 conformations was in part facilitated by Val12. Two single amino acid substitutions that reduced and abolished hydrophobicity at position 12, respectively, resulted in a proportionally increased structural variability. Our results suggest that Aβ11–40 and Aβ11–42 oligomers might be less toxic than Aβ1–40 and Aβ1–42 oligomers and offer a plausible explanation for the experimentally–observed increased toxicity of Aβ3–40 and Aβ3–42 and their pyroglutamated forms. PMID:23500806

  18. Humanin Specifically Interacts with Amyloid-β Oligomers and Counteracts Their in vivo Toxicity.

    PubMed

    Romeo, Margherita; Stravalaci, Matteo; Beeg, Marten; Rossi, Alessandro; Fiordaliso, Fabio; Corbelli, Alessandro; Salmona, Mario; Gobbi, Marco; Cagnotto, Alfredo; Diomede, Luisa

    2017-03-06

    The 24-residue peptide humanin (HN) has been proposed as peptide-based inhibitors able to interact directly with amyloid-β (Aβ) oligomers and interfere with the formation and/or biological properties of toxic Aβ species. When administered exogenously HN, or its synthetic S14G-derivative (HNG), exerted multiple cytoprotective effects, counteracting the Aβ-induced toxicity. Whether these peptides interact directly with Aβ, particularly with the soluble oligomeric assemblies, remains largely unknown. We here investigated the ability of HN and HNG to interact directly with highly aggregating Aβ42, and interfere with the formation and toxicity of its oligomers. Experiments were run in cell-free conditions and in vivo in a transgenic C. elegans strain in which the Aβ toxicity was specifically due to oligomeric species. Thioflavin-T assay indicated that both HN and HNG delay the formation and reduce the final amount of Aβ42 fibrils. In vitro surface plasmon resonance studies indicated that they interact with Aβ42 oligomers favoring the formation of amorphous larger assemblies, observed with turbidity and electron microscopy. In vivo studies indicated that both HN and HNG decrease the relative abundance of A11-positive prefibrillar oligomers as well as OC-positive fibrillar oligomers and had similar protective effects. However, while HN possibly decreased the oligomers by promoting their assembly into larger aggregates, the reduction of oligomers caused by HNG can be ascribed to a marked decrease of the total Aβ levels, likely the consequence of the HNG-induced overexpression of the Aβ-degrading enzyme neprilysin. These findings provide information on the mechanisms underlying the anti-oligomeric effects of HN and HNG and illustrate the role of S14G substitution in regulating the in vivo mechanism of action.

  19. Self-assembly of conjugated oligomers and polymers at the interface: structure and properties.

    PubMed

    Xu, Lirong; Yang, Liu; Lei, Shengbin

    2012-08-07

    In this review, we give a brief account on the recent scanning tunneling microscopy investigation of interfacial structures and properties of π-conjugated semiconducting oligomers and polymers, either at the solid-air (including solid-vacuum) or at the solid-liquid interface. The structural aspects of the self-assembly of both oligomers and polymers are highlighted. Conjugated oligomers can form well ordered supramolecular assemblies either at the air-solid or liquid-solid interface, thanks to the relatively high mobility and structural uniformity in comparison with polymers. The backbone structure, substitution of side chains and functional groups can affect the assembling behavior significantly, which offers the opportunity to tune the supramolecular structure of these conjugated oligomers at the interface. For conjugated polymers, the large molecular weight limits the mobility on the surface and the distribution in size also prevents the formation of long range ordered supramolecular assembly. The submolecular resolution obtained on the assembling monolayers enables a detailed investigation of the chain folding at the interface, both the structural details and the effect on electronic properties. Besides the ability in studying the assembling structures at the interfaces, STM also provides a reasonable way to evaluate the distribution of the molecular weight of conjugated polymers by statistic of the contour length of the adsorbed polymer chains. Both conjugated oligomers and polymers can form composite assemblies with other materials. The ordered assembly of oligomers can act as a template to controllably disperse other molecules such as coronene or fullerene. These investigations open a new avenue to fine tune the assembling structure at the interface and in turn the properties of the composite materials. To summarize scanning tunneling microscopy has demonstrated its surprising ability in the investigation of the assembling structures and properties of

  20. Amplification and analysis of promoter region of insulin receptor gene in a patient with leprechaunism associated with severe insulin resistance.

    PubMed

    Haruta, T; Imamura, T; Iwanishi, M; Egawa, K; Goji, K; Kobayashi, M

    1995-04-01

    A patient with leprechaunism associated with severe insulin resistance was studied to identify the molecular and genetic basis for insulin resistance. Insulin binding and surface labeling of transformed lymphocytes prepared from the patient showed a significantly decreased insulin receptor number on the cell surface. Southern blot analysis of the insulin receptor gene showed no evidence of large insertions or deletions. Furthermore, direct sequencing of all 22 exons and exon-intron junctions of the insulin receptor gene failed to show any missense mutations, nonsense mutations, or mutations at exon-intron junctions. However, Northern blot analysis indicated significantly decreased insulin receptor mRNA expression in the patient's cells. Moreover, restriction endonuclease digestion of the amplified cDNA suggested that the expression levels of one allele were less efficient than the other. These findings suggested that the regulatory region of the insulin receptor gene might have abnormalities. Therefore, we examined the 5' flanking region of the insulin receptor gene. Southern blot analysis showed no major deletions or insertions between positions -1,823 and -2 relative to the translation initiation site. A 5' flanking region of the insulin receptor gene spanning positions -881 approximately +7 was amplified by polymerase chain reaction (PCR) and introduced into a reporter plasmid carrying the human growth hormone (hGH) gene. The nucleotide sequence of the amplified fragment showed two polymorphic sites at positions -603 and -500 in the patient, as well as in normal subjects. No other abnormal sequence was found in the patient. Promoter activity measured by hGH expression in transfected mouse L cells was not influenced by the polymorphism at position -603 located in a cluster of GC boxes.(ABSTRACT TRUNCATED AT 250 WORDS)

  1. Aromatic oligomers that form hetero duplexes in aqueous solution.

    PubMed

    Gabriel, Gregory J; Iverson, Brent L

    2002-12-25

    The electron-deficient 1,4,5,8-naphthalenetetracarboxylic diimide (Ndi) and electron-rich 1,5-dialkoxynaphthalene (Dan) have been shown to complex strongly with each other in water due to the hydrophobic effect as modulated through the electrostatic complementarity of the stacked dimer. Previously, oligomers of alternating Ndi and Dan units, termed aedamers, were the first foldamers to employ intramolecular aromatic stacking to effect the formation of secondary structure of nonnatural chains in aqueous solution. Described here is the use of this aromatic-aromatic (or pi-pi) interaction, this time in an intermolecular format, to demonstrate the self-assembly of stable hetero duplexes from a set of molecular strands (1a-4a) and (1b-4b) incorporating Ndi and Dan units, respectively. A 1-to-1 binding stoichiometry was determined from NMR and isothermal titration calorimetry (ITC) investigations, and these experiments indicated that association is enthalpically favored with the tetra-Ndi (4a) and tetra-Dan (4b) strands forming hetero duplexes (4a:4b) with a stability constant of 350 000 M-1 at T = 318 K. Polyacrylamide gel electrophoresis (PAGE) also illustrated the strong interaction between 4a and 4b and support a 1-to-1 binding mode even when one component is in slight excess. Overall, this system is the first to utilize complementary aromatic units to drive discrete self-assembly in aqueous solution. This new approach for designing assemblies is encouraging for future development of duplex systems with highly programmable modes of binding in solution or on surfaces.

  2. Novel supramolecular elastomer films based on linear carboxyl-terminated polydimethylsiloxane oligomers: preparation, characterization, biocompatibility, and application in wound dressings.

    PubMed

    Zhang, Anqiang; Deng, Wenwen; Lin, Yaling; Ye, Junhui; Dong, Yaomin; Lei, Yufeng; Chen, Hongtao

    2014-01-01

    A novel supramolecular elastomer (SESi) based on multiple hydrogen bond associations between low-molecular-weight polydimethylsiloxane chains was obtained through a two-step reaction of linear carboxyl-terminated polydimethylsiloxane oligomers with diethylenetriamine and urea, and the reaction mechanism was characterized. The results of differential scanning calorimetry and X-ray diffraction analyses indicated that the supramolecular network structure is completely amorphous, endowing SESi with rubber-like elastic behavior at room temperature. The transparent SESi film prepared by hot pressing displayed nice viscoelasticity, benign water absorption, water vapor transition rates, and ideal biocompatibility; and did not show cytotoxicity or skin irritation. These properties allow the elastomer to function as an occlusive wound dressing. To demonstrate its potential in wound dressings, a detailed comparison of commercial 3M Tegaderm(™) film and the SESi film was conducted. The SESi film exhibited similar effects in wound healing, and the wound bed was covered by the SESi film without the occurrence of significant adverse reactions.

  3. [Treatment by external insulin pump].

    PubMed

    Clavel, Sylvaine

    2010-12-01

    Since the recent recommendations by the French speaking association for research on diabetes and metabolic illnesses (Alfediam), treatment by insulin pump has found itself in competition with basal-bolus, a procedure using similar injections of insulin which has become a benchmark treatment. The latest Alfediam guidelines focus on defining ways of treating diabetics with an external insulin pump.

  4. Insulin Resistance in Alzheimer's Disease

    PubMed Central

    Dineley, Kelly T; Jahrling, Jordan B; Denner, Larry

    2014-01-01

    Insulin is a key hormone regulating metabolism. Insulin binding to cell surface insulin receptors engages many signaling intermediates operating in parallel and in series to control glucose, energy, and lipids while also regulating mitogenesis and development. Perturbations in the function of any of these intermediates, which occur in a variety of diseases, cause reduced sensitivity to insulin and insulin resistance with consequent metabolic dysfunction. Chronic inflammation ensues which exacerbates compromised metabolic homeostasis. Since insulin has a key role in learning and memory as well as directly regulating ERK, a kinase required for the type of learning and memory compromised in early Alzheimer's disease (AD), insulin resistance has been identified as a major risk factor for the onset of AD. Animal models of AD or insulin resistance or both demonstrate that AD pathology and impaired insulin signaling form a reciprocal relationship. Of note are human and animal model studies geared toward improving insulin resistance that have led to the identification of the nuclear receptor and transcription factor, peroxisome proliferator-activated receptor gamma (PPARγ) as an intervention tool for early AD. Strategic targeting of alternate nodes within the insulin signaling network has revealed disease-stage therapeutic windows in animal models that coalesce with previous and ongoing clinical trial approaches. Thus, exploiting the connection between insulin resistance and AD provides powerful opportunities to delineate therapeutic interventions that slow or block the pathogenesis of AD. PMID:25237037

  5. 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.

  6. Synthesis of paucidisperse poly(gamma-benzyl-alpha,L-glutamate) oligomers and star polymers with rigid arms.

    PubMed

    Wang, X; Daly, W H; Russo, P; Ngu-Schwemlein, M

    2001-01-01

    The synthesis of highly uniform gamma-benzyl-alpha,L-glutamate (BLG) oligomers via a convergent solution phase approach is reported. BLG oligomers were produced with designed lengths of 4, 8, 12, and 16 as a first step to production of BLG-4-mer and BLG-8-mer rod stars. The star oligomers were purified by size-exclusion chromatography and reversed phase HPLC, and characterized by MALDI-TOF mass spectrometry and reversed phase HPLC. These star-shaped BLG oligomers could be used as initiators for growing larger stars.

  7. Formation of secondary organic aerosol and oligomers from the ozonolysis of enol ethers

    NASA Astrophysics Data System (ADS)

    Sadezky, A.; Chaimbault, P.; Mellouki, A.; Römpp, A.; Winterhalter, R.; Le Bras, G.; Moortgat, G. K.

    2006-10-01

    Formation of secondary organic aerosol has been observed in the gas phase ozonolysis of a series of enol ethers, among them several alkyl vinyl ethers (AVE, ROCH=CH2), such as ethyl, propyl, n-butyl, iso-butyl, t-butyl vinyl ether, and ethyl propenyl ether (EPE, C2H5OCH=CHCH3). The ozonolysis has been studied in a 570 l spherical glass reactor at ambient pressure (730 Torr) and room temperature (296 K). Gas phase reaction products were investigated by in-situ FTIR spectroscopy, and secondary organic aerosol (SOA) formation was monitored by a scanning mobility particle sizer (SMPS). The chemical composition of the formed SOA was analysed by a hybrid mass spectrometer using electrospray ionization (ESI). The main stable gas phase reaction product is the respective alkyl formate ROC(O)H, formed with yields of 60 to 80%, implying that similar yields of the corresponding excited Criegee Intermediates (CI) CH2O2 for the AVE and CH3CHO2 for EPE are generated. Measured SOA yields are between 2 to 4% for all enol ethers. Furthermore, SOA formation is strongly reduced or suppressed by the presence of an excess of formic acid, which acts as an efficient CI scavenger. Chemical analysis of the formed SOA by ESI(+)/MS-TOF allows to identify oligomeric compounds in the mass range 200 to 800 u as its major constituents. Repetitive chain units are identified as CH2O2 (mass 46) for the AVE and C2H4O2 (mass 60) for EPE and thus have the same chemical compositions as the respective major Criegee Intermediates formed during ozonolysis of these ethers. The oligomeric structure and chain unit identity are confirmed by HPLC/ESI(+)/MS-TOF and ESI(+)/MS/MS-TOF experiments, whereby successive and systematic loss of a fragment with mass 46 for the AVE (and mass 60 for EPE) is observed. It is proposed that the oligomer has the following basic structure of an oligoperoxide, -[CH(R)-O-O]n-, where R=H for the AVE and R=CH3 for the EPE. Oligoperoxide formation is thus suggested to be another, so

  8. Formation of secondary organic aerosol and oligomers from the ozonolysis of enol ethers

    NASA Astrophysics Data System (ADS)

    Sadezky, A.; Chaimbault, P.; Mellouki, A.; Römpp, A.; Winterhalter, R.; Le Bras, G.; Moortgat, G. K.

    2006-06-01

    Formation of secondary organic aerosol has been observed in the gas phase ozonolysis of a series of enol ethers, among them several alkyl vinyl ethers (AVE, ROCH=CH2), such as ethyl, propyl, n-butyl, iso-butyl, t-butyl vinyl ether, and ethyl propenyl ether (EPE, C2H5OCH=CHCH3). The ozonolysis has been studied in a 570 l spherical glass reactor at atmospheric pressure (730 Torr) and temperature (296 K). Gas phase reaction products were investigated by in-situ FTIR spectroscopy, and secondary organic aerosol (SOA) formation was monitored by a scanning mobility particle sizer (SMPS). The chemical composition of the formed SOA was analysed by a hybrid mass spectrometer using electrospray ionization (ESI). The main stable gas phase reaction product is the respective alkyl formate ROC(O)H, formed with yields of 60 to 80%, implying that similar yields of the corresponding Criegee Intermediates (CI) CH2O2 for the AVE and CH3CHO2 for EPE are generated. Measured SOA yields are between 2 to 4% for all enol ethers. Furthermore, SOA formation is strongly reduced or suppressed by the presence of an excess of formic acid, which acts as an efficient CI scavenger. Chemical analysis of the formed SOA by ESI(+)/MS-TOF allows to identify oligomeric compounds in the mass range 200 to 800 u as its major constituents. Repetitive chain units are identified as CH2O2 (mass 46) for the AVE and C2H4O2 (mass 60) for EPE and thus have the same chemical compositions as the respective major Criegee Intermediates formed during ozonolysis of these ethers. The oligomeric structure and chain unit identity are confirmed by HPLC/ESI(+)/MS-TOF and ESI(+)/MS/MS-TOF experiments, whereby successive and systematic loss of a fragment with mass 46 for the AVE (and mass 60 for EPE) is observed. It is proposed that the oligomer has the following basic structure of an oligoperoxide, -[CH(R)-O-O]n-, where R=H for the AVE and R=CH3 for the EPE. Oligoperoxide formation is thus suggested to be another, so far

  9. 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.

  10. In vitro release of a water-soluble agent from low viscosity biodegradable, injectable oligomers.

    PubMed

    Sharifpoor, Soroor; Amsden, Brian

    2007-03-01

    Low-molecular-weight poly(epsilon-caprolactone-co-1,3-trimethylene carbonate) and poly(1,3-trimethylene carbonate) are potential vehicles for the regio-specific delivery of water-soluble agents. In this paper, the characteristics and the mechanism governing the in vitro release of a model water-soluble drug, vitamin B12, from these polymer vehicles were determined. The loading of vitamin B12 was kept to 1 w/w%. The oligomers examined ranged from amorphous, high viscosity to crystalline but low viscosity. The oligomers did not degrade appreciably in vitro. The total fraction of vitamin B12 released increased as the crystallinity of the oligomers decreased, reaching nearly total release only for the completely amorphous oligomers. The rate of release was fastest for the amorphous oligomers and dependent on their viscosity. Inclusion of a more osmotically active agent, trehalose, into the vitamin B12 particles through co-lyophilization resulted in enhanced total fraction released and a faster release rate. The results are consistent with an osmotically driven release mechanism.

  11. Alzheimer's-associated Abeta oligomers show altered structure, immunoreactivity and synaptotoxicity with low doses of oleocanthal.

    PubMed

    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-beta1-42 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 Abeta 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 Abeta species, when assayed with both sequence- and conformation-specific Abeta 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 (Abeta-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.

  12. 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.

  13. Oligomer and SOA formation through aqueous phase photooxidation of methacrolein and methyl vinyl ketone

    NASA Astrophysics Data System (ADS)

    Liu, Yao; Siekmann, Frank; Renard, Pascal; El Zein, Atallah; Salque, Guillaume; El Haddad, Imad; Temime-Roussel, Brice; Voisin, Didier; Thissen, Roland; Monod, Anne

    2012-03-01

    This work investigates the ability of methacrolein (MACR) and methyl vinyl ketone (MVK) (the two main gas phase atmospheric oxidation products of isoprene) to form oligomers and secondary organic aerosol (SOA) upon aqueous phase OH-oxidation and subsequent water evaporation. For the two precursors, electrospray mass spectrometry (in infusion and coupled to liquid chromatography) analysis of the reacting solutions brought clear evidence for the formation of oligomer systems having a mass range of up to 1400 Da. More than 11 series of oligomers were found. For MVK, the intensity and masses of oligomers became increasingly important as MVK initial concentrations increased from 0.2 to 20 mM. For both precursors, the oligomers were responsible for the SOA formation during nebulization experiments. The evaluated SOA mass yield ranged from 3.9 to 9.9% for MVK. These yields were time dependent and were in good agreement with the range (1.6-11.7%) obtained for MACR under the same conditions by El Haddad et al. (2009).

  14. The Effect of Difunctional Oligomer Concentration and Processing Temperature on the Reactive Processing of Polymer Blends

    NASA Astrophysics Data System (ADS)

    O'Brien, Charles; Rice, Kevin; Dadmun, Mark

    2001-03-01

    Reactive processing is an interesting method to form compatibilizers for polymer blends in-situ. A model blend composed of poly(bisphenol A-co-epichlorohydrin) and poly(ethylene oxide) that is compatibilized with difunctional oligomers that are the same structure as the homopolymers is currently under investigation. It is expected that blocky copolymers will form at the bipahasic interface during processing as the difunctional oligomers undergo an addition copolymerization. Previous results have shown that the addition of the reactive oligomers improves the properties of the blend and thus this reactive process scheme is feasible. Additionally, these results indicate that the difunctioanal oligomers may act as plasticizers and continue to polymerize at room temperature after the blend is removed from the melt mixer. In this presentation, we will discuss our research that is focused on optimizing the reactive compatibilization process by controlling the amount of reactive oligomer added and the processing temperature and evaluating the effect of these parameters on the ultimate properties of the blend.

  15. Large-scale motif discovery using DNA Gray code and equiprobable oligomers

    PubMed Central

    Ichinose, Natsuhiro; Yada, Tetsushi; Gotoh, Osamu

    2012-01-01

    Motivation: How to find motifs from genome-scale functional sequences, such as all the promoters in a genome, is a challenging problem. Word-based methods count the occurrences of oligomers to detect excessively represented ones. This approach is known to be fast and accurate compared with other methods. However, two problems have hampered the application of such methods to large-scale data. One is the computational cost necessary for clustering similar oligomers, and the other is the bias in the frequency of fixed-length oligomers, which complicates the detection of significant words. Results: We introduce a method that uses a DNA Gray code and equiprobable oligomers, which solve the clustering problem and the oligomer bias, respectively. Our method can analyze 18 000 sequences of ~1 kbp long in 30 s. We also show that the accuracy of our method is superior to that of a leading method, especially for large-scale data and small fractions of motif-containing sequences. Availability: The online and stand-alone versions of the application, named Hegma, are available at our website: http://www.genome.ist.i.kyoto-u.ac.jp/~ichinose/hegma/ Contact: ichinose@i.kyoto-u.ac.jp; o.gotoh@i.kyoto-u.ac.jp PMID:22057160

  16. Chain-length and mode-delocalization dependent amide-I anharmonicity in peptide oligomers.

    PubMed

    Zhao, Juan; Wang, Jianping

    2012-06-07

    The diagonal anharmonicities of the amide-I mode in the alanine oligomers are examined in the normal-mode basis by ab initio calculations. The selected oligomers range from dimer to heptamer, in either the α-helical or β-sheet conformations. It is found that the anharmonicity varies from mode to mode within the same oligomer. For a given amide-I mode, the anharmonicity is closely related to the delocalization extent of the mode: the less it delocalizes, the larger the anharmonicity it has. Thus, the single-mode potential energy distribution (PED(max)) can be used as an indicator of the magnitude of the anharmonicity. It is found that as the peptide chain length increases, the averaged diagonal anharmonicity generally decreases; however, the sum of the averaged diagonal and off-diagonal anharmonicities within a peptide roughly remains a constant for all the oligomers examined, indicating the excitonic characteristics of the amide-I modes. Excitonic coupling tends to decrease the diagonal anharmonicities in a coupled system with multiple chromophores, which explains the observed behavior of the anharmonicities. The excitonic nature of the amide-I band in peptide oligomers is thus verified by the anharmonic computations. Isotopic substitution effect on the anharmonicities and mode localizations of the amide-I modes in peptides is also discussed.

  17. Amyloid Oligomers and Mature Fibrils Prepared from an Innocuous Protein Cause Diverging Cellular Death Mechanisms*

    PubMed Central

    Harte, Níal P.; Klyubin, Igor; McCarthy, Eoin K.; Min, Soyoung; Garrahy, Sarah Ann; Xie, Yongjing; Davey, Gavin P.; Boland, John J.; Rowan, Michael J.; Mok, K. Hun

    2015-01-01

    Despite significant advances, the molecular identity of the cytotoxic species populated during in vivo amyloid formation crucial for the understanding of neurodegenerative disorders is yet to be revealed. In this study lysozyme prefibrillar oligomers and fibrils in both mature and sonicated states have been isolated through an optimized ultrafiltration/ultracentrifugation method and characterized with various optical spectroscopic techniques, atomic force microscopy, and transmission electron microscopy. We examined their level and mode of toxicity on rat pheochromocytoma (PC12) cells in both differentiated and undifferentiated states. We find that oligomers and fibrils display cytotoxic capabilities toward cultured cells in vitro, with oligomers producing elevated levels of cellular injury toward undifferentiated PC12 cells (PC12undiff). Furthermore, dual flow cytometry staining experiments demonstrate that the oligomers and mature fibrils induce divergent cellular death pathways (apoptosis and secondary necrosis, respectively) in these PC12 cells. We have also shown that oligomers but not sonicated mature fibrils inhibit hippocampal long term potentiation, a form of synaptic plasticity implicated in learning and memory, in vivo. We conclude that our in vitro and in vivo findings confer a level of resistance toward amyloid fibrils, and that the PC 12-based comparative cytotoxicity assay can provide insights into toxicity differences between differently aggregated protein species. PMID:26221033

  18. 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.

  19. Sugar monomer and oligomer solubility: data and predictions for application to biomass hydrolysis.

    PubMed

    Gray, Matthew C; Converse, Alvin O; Wyman, Charles E

    2003-01-01

    Oligomer solubility could potentially play an important role in controlling the rates and yields in the thermochemical hydrolysis of hemicellulose as a pretreatment for subsequent enzymatic conversion of cellulose. However, limited data or models are available to describe the aqueous solubility of sugar monomers and oligomers. In this work, we measured the solubilities of sugars common to many biomass feedstocks in the temperature range of 25-30 degrees C. Then we reviewed solubility models for sugars from the open literature. Finally, we applied models to test their ability to describe this and other data reported in the literature. It was found that the solubility of sugar monomers was not well described by the ideal solubility law or other more complex models. However, with an empirical adjustment to the enthalpy of fusion, the ideal solubility law was able to approximately predict the solubility of cello-oligomers. Based on these results, solubilities for low molecular weight xylo-oligomers are predicted to investigate their possible importance in pretreatment and define further experimental measurements needed to improve our understanding of sugar and oligomer solubility.

  20. Comparison of mass spectrometric techniques for generating molecular weight information on a class of ethoxylated oligomers.

    PubMed

    Parees, D M; Hanton, S D; Clark, P A; Willcox, D A

    1998-04-01

    The results of fast atom bombardment (FAB), time-of-flight secondary ion mass spectrometry (ToF-SIMS), matrix-assisted laser desorption/ionization (MALD/I), electrospray ionization (ESI), and field desorption (FD) analyses of ethoxylated oligomers of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (Surfynol(®) 104) were compared.Each of these desorption mass spectrometry (MS) techniques can produce spectra of unfragmented cationized oligomers. From the observed ion series we calculate average molecular weight information. We have compared the results of mass spectrometric analyses of a series of ethoxylated Surfynol surfactants. Our data indicate that FAB, ToF-SIMS, MALDI/I, and ESI produce similar results for the lower molecular weight species, but that as the average molecular weight increases FAB and SIMS produce slightly lower results than MALD/I and FD. This could be due to increased fragmentation. ESI produced a result similar to FAB and SIMS for the highest average molecular weight material. Further experiments compare the mass spectral results with gas chromatographic quantitative data. Although gas chromatography is not expected to accurately analyze the higher mass oligomers, we observe significant differences in intensities of the short-chain oligomers (especially the 0- and 1-mers) when compared to the desorption mass spectrometer results. These differences may reflect poor cationization efficiency for very short oligomer chains in the mass spectrometric analyses.

  1. Increased insulin translation from an insulin splice-variant overexpressed in diabetes, obesity, and insulin resistance.

    PubMed

    Minn, Alexandra H; Lan, Hong; Rabaglia, Mary E; Harlan, David M; Peculis, Brenda A; Attie, Alan D; Shalev, Anath

    2005-03-01

    Type 2 diabetes occurs when pancreatic beta-cells become unable to compensate for the underlying insulin resistance. Insulin secretion requires beta-cell insulin stores to be replenished by insulin biosynthesis, which is mainly regulated at the translational level. Such translational regulation often involves the 5'-untranslated region. Recently, we identified a human insulin splice-variant (SPV) altering only the 5'-untranslated region and conferring increased translation efficiency. We now describe a mouse SPV (mSPV) that is found in the cytoplasm and exhibits increased translation efficiency resulting in more normal (prepro)insulin protein per RNA. The RNA stability of mSPV is not increased, but the predicted secondary RNA structure is altered, which may facilitate translation. To determine the role of mSPV in insulin resistance and diabetes, mSPV expression was measured by quantitative real-time RT-PCR in islets from three diabetic and/or insulin-resistant, obese and nonobese, mouse models (BTBRob/ob, C57BL/6ob/ob, and C57BL/6azip). Interestingly, mSPV expression was significantly higher in all diabetic/insulin-resistant mice compared with wild-type littermates and was dramatically induced in primary mouse islets incubated at high glucose. This raises the possibility that the mSPV may represent a compensatory beta-cell mechanism to enhance insulin biosynthesis when insulin requirements are elevated by hyperglycemia/insulin resistance.

  2. Use of a small peptide fragment as an inhibitor of insulin fibrillation process: a study by high and low resolution spectroscopy.

    PubMed

    Banerjee, Victor; Kar, Rajiv K; Datta, Aritreyee; Parthasarathi, Krupakar; Chatterjee, Subhrangsu; Das, Kali P; Bhunia, Anirban

    2013-01-01

    A non-toxic, nine residue peptide, NIVNVSLVK is shown to interfere with insulin fibrillation by various biophysical methods. Insulin undergoes conformational changes under certain stress conditions leading to amyloid fibrils. Fibrillation of insulin poses a problem in its long-term storage, reducing its efficacy in treating type II diabetes. The dissociation of insulin oligomer to monomer is the key step for the onset of fibrillation. The time course of insulin fibrillation at 62°C using Thioflavin T fluorescence shows an increase in the lag time from 120 min without peptide to 236 min with peptide. Transmission electron micrographs show branched insulin fibrils in its absence and less inter-fibril association in its presence. Upon incubation at 62°C and pH 2.6, insulin lost some α-helical structure as seen by Fourier transformed infra-red spectroscopy (FT-IR), but if the peptide is added, secondary structure is almost fully maintained for 3 h, though lost partially at 4 h. FT-IR spectroscopy also shows that insulin forms the cross beta structure indicative of fibrils beyond 2 h, but in the presence of the peptide, α-helix retention is seen till 4 h. Both size exclusion chromatography and dynamic light scattering show that insulin primarily exists as trimer, whose conversion to a monomer is resisted by the peptide. Saturation transfer difference nuclear magnetic resonance confirms that the hydrophobic residues in the peptide are in close contact with an insulin hydrophobic groove. Molecular dynamics simulations in conjunction with principal component analyses reveal how the peptide interrupts insulin fibrillation. In vitro hemolytic activity of the peptide showed insignificant cytotoxicity against HT1080 cells. The insulin aggregation is probed due to the inter play of two key residues, Phe(B24) and Tyr(B26) monitored from molecular dynamics simulations studies. Further new peptide based leads may be developed from this nine residue peptide.

  3. Transdermal Insulin Delivery Using Microdermabrasion

    PubMed Central

    Andrews, Samantha; Lee, Jeong Woo; Choi, Seong-O

    2011-01-01

    Purpose Transdermal insulin delivery is an attractive needle-free alternative to subcutaneous injection conventionally used to treat diabetes. However, skin’s barrier properties prevent insulin permeation at useful levels. Methods We investigated whether microdermabrasion can selectively remove skin’s surface layers to increase skin permeability as a method to administer insulin to diabetic rats. We further assessed the relative roles of stratum corneum and viable epidermis as barriers to insulin delivery. Results Pretreatment of skin with microdermabrasion to selectively remove stratum corneum did not have a significant effect on insulin delivery or reduction in blood glucose level (BGL). Removal of full epidermis by microdermabrasion significantly reduced BGL, similar to the positive control involving subcutaneous injection of 0.1U insulin. Significant pharmacokinetic differences between microdermabrasion and subcutaneous injection were faster time to peak insulin concentration after injection and larger peak insulin concentration and area-under-the-curve after microdermabrasion. Conclusions Microdermabrasion can increase skin permeability to insulin at levels sufficient to reduce BGL. Viable epidermis is a barrier to insulin delivery such that removal of full epidermis enables significantly more insulin delivery than removal of stratum corneum alone. PMID:21499837

  4. Insulin Signalling: The Inside Story.

    PubMed

    Posner, Barry I

    2017-02-01

    Insulin signalling begins with binding to its cell surface insulin receptor (IR), which is a tyrosine kinase. The insulin receptor kinase (IRK) is subsequently autophosphorylated and activated to tyrosine phosphorylate key cellular substrates that are essential for entraining the insulin response. Although IRK activation begins at the cell surface, it is maintained and augmented following internalization into the endosomal system (ENS). The peroxovanadium compounds (pVs) were discovered to activate the IRK in the absence of insulin and lead to a full insulin response. Thus, IRK activation is both necessary and sufficient for insulin signalling. Furthermore, this could be shown to occur with activation of only the endosomal IRK. The mechanism of pV action was shown to be the inhibition of IRK-associated phosphotyrosine phosphatases (PTPs). Our studies showed that the duration and intensity of insulin signalling are modulated within ENS by the recruitment of cellular substrates to ENS; intra-endosomal acidification, which promotes dissociation of insulin from the IRK; an endosomal acidic insulinase, which degrades intra-endosomal insulin; and IRK-associated PTPs, which dephosphorylate and, hence, deactivate the IRK. Therefore, the internalization of IRKs is central to insulin signalling and its regulation.

  5. Adipocyte lipolysis and insulin resistance.

    PubMed

    Morigny, Pauline; Houssier, Marianne; Mouisel, Etienne; Langin, Dominique

    2016-06-01

    Obesity-induced insulin resistance is a major risk factor for the development of type 2 diabetes. Basal fat cell lipolysis (i.e., fat cell triacylglycerol breakdown into fatty acids and glycerol in the absence of stimulatory factors) is elevated during obesity and is closely associated with insulin resistance. Inhibition of adipocyte lipolysis may therefore be a promising therapeutic strategy for treating insulin resistance and preventing obesity-associated type 2 diabetes. In this review, we explore the relationship between adipose lipolysis and insulin sensitivity. After providing an overview of the components of fat cell lipolytic machinery, we describe the hypotheses that may support the causality between lipolysis and insulin resistance. Excessive circulating fatty acids may ectopically accumulate in insulin-sensitive tissues and impair insulin action. Increased basal lipolysis may also modify the secretory profile of adipose tissue, influencing whole body insulin sensitivity. Finally, excessive fatty acid release may also worsen adipose tissue inflammation, a well-known parameter contributing to insulin resistance. Partial genetic or pharmacologic inhibition of fat cell lipases in mice as well as short term clinical trials using antilipolytic drugs in humans support the benefit of fat cell lipolysis inhibition on systemic insulin sensitivity and glucose metabolism, which occurs without an increase of fat mass. Modulation of fatty acid fluxes and, putatively, of fat cell secretory pattern may explain the amelioration of insulin sensitivity whereas changes in adipose tissue immune response do not seem involved.

  6. 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

  7. Exploring the assembly mechanism of tetrapeptide oligomers using the Activation-Relaxation Technique

    NASA Astrophysics Data System (ADS)

    Wei, Guanghong; Mousseau, Normand; Derreumaux, Philippe

    2004-03-01

    Alzheimer's disease and Parkinson's disease are associated with formation of amyloid fibrils. All amyloid fibrils seem to share a common cross β-sheet structure. Experimental studies have shown that peptides as short as 4 amino acids can form amyloid fibrils. It has also been shown that the oligomers that form early in the aggregation process of even non-disease-related proteins may be cytotoxic. We report a detailed study of the assembly mechanisms of the tetrapeptides into different size oligomers: trimers, hexamers and more. The assembly of the oligomers, in which the peptides form β-sheets through interpeptide interactions, are studied using the activation-relaxation technique (ART) in combination with a reduced off-lattice energy model (OPEP). We also describe the multiple pathways of oligomerization as well as categorize the various oligomeric intermediates, providing information of the early events of β-sheet formation.

  8. 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

  9. Simple extrapolation method to predict the electronic structure of conjugated polymers from calculations on oligomers

    SciTech Connect

    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, 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.

  10. Simple extrapolation method to predict the electronic structure of conjugated polymers from calculations on oligomers

    DOE PAGES

    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

  11. 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.

  12. 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.

  13. pH-dependent self-association of zinc-free Insulin characterized by concentration-gradient static light scattering

    PubMed Central

    Attri, Arun K.; Fernández, Cristina; Minton, Allen P.

    2010-01-01

    Insulin self-association at pH 1.85, 1.95, 3.0, 7.2, 8.0 and 10 was studied via composition gradient light scattering (CG-SLS). At pH 1.95 in acetic acid, insulin was found to exist as a monomer, and in pH 1.85 HCl as a dimer. At pH values of 3.0 – 8.0, the dependence of scattering intensity upon total insulin concentration at concentrations of up to 1.5 mg/mL may be quantitatively accounted for by a simple isodesmic association equilibrium scheme requiring only a single association constant for addition of monomer to monomer or any oligomer. At pH 10, the association constant for addition of monomer to monomer was found to be smaller than the association constant for addition of monomer to all higher oligomers by a factor of approximately five. The isodesmic association scheme was also found to quantitatively account for the concentration dependence of the weight-average molecular weight derived from previously published sedimentation equilibrium measurements made at pH 7.0, and the best-fit value of the stepwise equilibrium constant obtained therefrom was in excellent agreement with that obtained from analysis of the light scattering data obtained at pH 7.2 PMID:20202737

  14. Insulin treatment of type 2 diabetes: considerations when converting from human insulin to insulin analogs.

    PubMed

    Griffin, Stacy

    2013-03-01

    Type 2 diabetes mellitus is a highly prevalent disease characterized by insulin resistance, hyperglycemia, and diminished pancreatic β-cell function. Conventional insulin products used to manage this disease include regular human insulin and intermediate-acting human insulin. However, due to several limitations imposed by human insulins, such as onset and duration of action that do not coincide with physiologic needs and increased risk of hypoglycemia, insulin analogs were developed. Because they more closely mimic the physiologic action of endogenous insulin, insulin analogs are associated with more effective glucose control, a lower risk of hypoglycemia, greater convenience, and, in some instances, less weight gain. Switching from human insulin to insulin analogs is easily accomplished. Several studies have demonstrated a high rate of success with patient-initiated, self-adjusted dosing algorithms compared to investigator/clinician-initiated dose adjustments. These studies and several other published guidelines on insulin analogs provide patients and clinicians with information pertaining to better treatment options and can help increase overall patient satisfaction.

  15. 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

  16. Air-Stable n-channel Diketopyrrolopyrrole-Diketopyrrolopyrrole Oligomers for High Performance Ambipolar Organic Transistors.

    PubMed

    Mukhopadhyay, Tushita; Puttaraju, Boregowda; Senanayak, Satyaprasad P; Sadhanala, Aditya; Friend, Richard; Faber, Hendrik A; Anthopoulos, Thomas D; Salzner, Ulrike; Meyer, Andreas; Patil, Satish

    2016-09-28

    n-channel organic semiconductors are prone to oxidation upon exposed to ambient conditions. Herein, we report design and synthesis of diketopyrrolopyrrole (DPP)-based oligomers for ambipolar organic thin-film transistors (OFETs) with excellent air and bias stability at ambient conditions. The cyclic voltammetry measurements reveal exceptional electrochemical stability during the redox cycle of oligomers. Structural properties including aggregation, crystallinity, and morphology in thin film were investigated by UV-visible spectroscopy, atomic force microscopy (AFM), thin-film X-ray diffraction (XRD), and grazing incidence small-angle X-ray scattering (GISAXS) measurements. AFM reveals morphological changes induced by different processing conditions whereas GISAXS measurements show an increase in the population of face-on oriented crystallites in films subjected to a combination of solvent and thermal treatments. These measurements also highlight the significance of chalcogen atom from sulfur to selenium on the photophysical, optical, electronic, and solid-state properties of DPP-DPP oligomers. Charge carrier mobilities of the oligomers were investigated by fabricating top-gate bottom-contact (TG-BC) thin-film transistors by annealing the thin films under various conditions. Combined solvent and thermal annealing of DPP-DPP oligomer thin films results in consistent electron mobilities as high as ∼0.2 cm(2) V(-1) s(-1) with an on/off ratio exceeding 10(4). Field-effect behavior was retained for up to ∼4 weeks, which illustrates remarkable air and bias stability. This work paves the way toward the development of n-channel DPP-DPP-based oligomers exhibiting retention of field-effect behavior with superior stability at ambient conditions.

  17. 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.

  18. Folding and self-assembly of aromatic and aliphatic urea oligomers: towards connecting structure and function.

    PubMed

    Fischer, Lucile; Guichard, Gilles

    2010-07-21

    Folding and self-assembly of biomacromolecules has inspired the development of discrete, non-natural oligomers that fold and/or self-assemble in a controlled manner. Though aromatic and aliphatic oligoamides remain unmatched for structural diversity and synthetic versatility, oligomers based on amide bond surrogates, such as urea backbones, also demonstrated a propensity for folding and self-assembly. In this Perspective, we review the advances in the design of oligomeric aromatic and aliphatic urea sequences (essentially N,N'-linked) that fold and/or self-assemble. Whenever applicable, the relationship between structure and function will be highlighted.

  19. Energy Aspects of Thermal Molecular Switching: Molecular Thermal Hysteresis of Helicene Oligomers.

    PubMed

    Shigeno, Masanori; Kushida, Yo; Yamaguchi, Masahiko

    2015-07-20

    Molecular switching is a phenomenon by which a molecule reversibly changes its structure and state in response to external stimuli or energy. Herein, molecular switching is discussed from thermodynamic and kinetic aspects in terms of energy supply with an emphasis on the thermal switching exhibited by helicene oligomers. It includes the inversion of relative thermodynamic stability induced by temperature changes and molecular thermal hysteresis in a closed system. The thermal phenomenon associated with the oligomers involves population/concentration changes between metastable states under nonequilibrium thermodynamic control.

  20. Synthesis and G-Quadruplex-Binding Properties of Defined Acridine Oligomers

    PubMed Central

    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

  1. Thermo-reversible gelation of atactic poly(methyl methacrylate) in poly(ethylene glycol) oligomers.

    PubMed

    Gao, Yun; Yu, Chunhong; Chen, Minzhi; Wang, Xiaoliang; Zhou, Dongshan; Xue, Gi

    2013-04-01

    The temperature-concentration behavior of physical gel by atactic poly(methyl methacrylate) (aPMMA) in poly(ethylene glycol) oligomer (PEG400) was investigated. A liquid-liquid demixing interferes with a glass transition during cooling. The combination of demixing and T g leads to the formation of amorphous gels at low temperature. We suggest that the gelation of aPMMA/PEG400 is a glassy gel, in which short-range attractive depletion interaction in the polymer/oligomer system was the driving force at molecular level.

  2. Absorption enhancing effects of chitosan oligomers on the intestinal absorption of low molecular weight heparin in rats.

    PubMed

    Zhang, Hailong; Mi, Jie; Huo, Yayu; Huang, Xiaoyan; Xing, Jianfeng; Yamamoto, Akira; Gao, Yang

    2014-05-15

    Absorption enhancing effects of chitosan oligomers with different type and varying concentration on the intestinal absorption of low molecular weight heparin (LMWH) were examined by an in situ closed loop method in different intestinal sections of rats. Chitosan hexamer with the optimal concentration of 0.5% (w/v) showed the highest absorption enhancing ability both in the small intestine and large intestine. The membrane toxicities of chitosan oligomers were evaluated by morphological observation and determining the biological markers including amount of protein and activity of lactate dehydrogenase (LDH) released from intestinal epithelium cells. There was no obvious change both in levels of protein and LDH and morphology in the intestinal membrane between control and various chitosan oligomers groups, suggesting that chitosan oligomers did not induce any significant membrane damage to the intestinal epithelium. In addition, zeta potentials became less negative and amount of free LMWH gradually decreased when various chitosan oligomers were added to LMWH solution, revealing that electrostatic interaction between positively charged chitosan oligomers and negative LMWH was included in the absorption enhancing mechanism of chitosan oligomers. In conclusion, chitosan oligomers, especially chitosan hexamer, are safe and efficient absorption enhancers and can be used promisingly to improve oral absorption of LMWH.

  3. Single-Molecule Imaging Reveals Aβ42:Aβ40 Ratio-Dependent Oligomer Growth on Neuronal Processes

    PubMed Central

    Johnson, Robin D.; Schauerte, Joseph A.; Chang, Chun-Chieh; Wisser, Kathleen C.; Althaus, John Christian; Carruthers, Cynthia J.L.; Sutton, Michael A.; Steel, Duncan G.; Gafni, Ari

    2013-01-01

    Soluble oligomers of the amyloid-β peptide have been implicated as proximal neurotoxins in Alzheimer’s disease. However, the identity of the neurotoxic aggregate(s) and the mechanisms by which these species induce neuronal dysfunction remain uncertain. Physiologically relevant experimentation is hindered by the low endogenous concentrations of the peptide, the metastability of Aβ oligomers, and the wide range of observed interactions between Aβ and biological membranes. Single-molecule microscopy represents one avenue for overcoming these challenges. Using this technique, we find that Aβ binds to primary rat hippocampal neurons at physiological concentrations. Although amyloid-β(1–40) as well as amyloid-β(1–42) initially form larger oligomers on neurites than on glass slides, a 1:1 mix of the two peptides result in smaller neurite-bound oligomers than those detected on-slide or for either peptide alone. With 1 nM peptide in solution, Aβ40 oligomers do not grow over the course of 48 h, Aβ42 oligomers grow slightly, and oligomers of a 1:1 mix grow substantially. Evidently, small Aβ oligomers are capable of binding to neurons at physiological concentrations and grow at rates dependent on local Aβ42:Aβ40 ratios. These results are intriguing in light of the increased Aβ42:Aβ40 ratios shown to correlate with familial Alzheimer’s disease mutations. PMID:23442968

  4. The effects of a multifunctional oligomer and its incorporation strategies on the gene delivery efficiency of poly(L-lysine).

    PubMed

    Zhou, Dezhong; Li, Congxin; Hu, Yuling; Zhou, Hao; Chen, Jiatong; Zhang, Zhengpu; Guo, Tianying

    2012-05-14

    A novel multifunctional oligomer is synthesized and incorporated to enhance the gene delivery efficiency of PLL via non-electrostatic assembly and covalent grafting strategies. The improvement of the gene delivery efficiency is dependent on the gene carrying complex properties, and the properties are dependent on the oligomer incorporation strategy.

  5. 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.

  6. 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

  7. Enzymatic production of defined chitosan oligomers with a specific pattern of acetylation using a combination of chitin oligosaccharide deacetylases.

    PubMed

    Hamer, Stefanie Nicole; Cord-Landwehr, Stefan; Biarnés, Xevi; Planas, Antoni; Waegeman, Hendrik; Moerschbacher, Bruno Maria; Kolkenbrock, Stephan

    2015-03-03

    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.

  8. Alpha-synuclein oligomers and fibrils originate in two distinct conformer pools: a small angle X-ray scattering and ensemble optimisation modelling study.

    PubMed

    Curtain, Cyril C; Kirby, Nigel M; Mertens, Haydyn D T; Barnham, Kevin J; Knott, Robert B; Masters, Colin L; Cappai, Roberto; Rekas, Agata; Kenche, Vijaya B; Ryan, Timothy

    2015-01-01

    The 140 residue intrinsically disordered protein α-synuclein (α-syn) self-associates to form fibrils that are the major constituent of the Lewy body intracellular protein inclusions, and neurotoxic oligomers. Both of these macromolecular structures are associated with a number of neurodegenerative diseases, including Parkinson's disease and dementia with Lewy bodies. Using ensemble optimisation modelling (EOM) and small angle X-ray scattering (SAXS) on a size-exclusion column equipped beamline, we studied how the distribution of structural conformers in α-syn may be influenced by the presence of the familial early-onset mutations A30P, E45K and A53T, by substituting the four methionine residues with alanines and by reaction with copper (Cu2+) or an anti-fibril organic platinum (Pt) complex. We found that the WT had two major conformer groups, representing ensembles of compact and extended structures. The population of the extended group was increased in the more rapidly fibril-forming E45K and A53T mutants, while the compact group was enlarged in the oligomer-forming A30P mutant. Addition of Cu2+ resulted in the formation of an ensemble of compact conformers, while the anti-fibril agent and alanine substitution substantially reduced the population of extended conformers. Since our observations with the mutants suggest that fibrils may be drawn from the extended conformer ensemble, we propose that the compact and extended ensembles represent the beginning of oligomer and fibril formation pathways respectively, both of which have been reported to lead to a toxic gain of function. Manipulating these pathways and monitoring the results by EOM and SAXS may be useful in the development of anti-Parkinson's disease therapies.

  9. 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.

  10. Soluble Oligomers of the Pore-forming Toxin Cytolysin A from Escherichia coli Are Off-pathway Products of Pore Assembly*

    PubMed Central

    Roderer, Daniel; Benke, Stephan; Schuler, Benjamin; Glockshuber, Rudi

    2016-01-01

    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

  11. Ordered Self-Assembly Mechanism of a Spherical Oncoprotein Oligomer Triggered by Zinc Removal and Stabilized by an Intrinsically Disordered Domain

    PubMed Central

    Smal, Clara; Alonso, Leonardo G.; Wetzler, Diana E.; Heer, Angeles; de Prat Gay, Gonzalo

    2012-01-01

    Background Self-assembly is a common theme in proteins of unrelated sequences or functions. The human papillomavirus E7 oncoprotein is an extended dimer with an intrinsically disordered domain, that can form large spherical oligomers. These are the major species in the cytosol of HPV transformed and cancerous cells. E7 binds to a large number of targets, some of which lead to cell transformation. Thus, the assembly process not only is of biological relevance, but represents a model system to investigate a widely distributed mechanism. Methodology/Principal Findings Using various techniques, we monitored changes in secondary, tertiary and quaternary structure in a time course manner. By applying a robust kinetic model developed by Zlotnik, we determined the slow formation of a monomeric “Z-nucleus” after zinc removal, followed by an elongation phase consisting of sequential second-order events whereby one monomer is added at a time. This elongation process takes place at a strikingly slow overall average rate of one monomer added every 28 seconds at 20 µM protein concentration, strongly suggesting either a rearrangement of the growing complex after binding of each monomer or the existence of a “conformation editing” mechanism through which the monomer binds and releases until the appropriate conformation is adopted. The oligomerization determinant lies within its small 5 kDa C-terminal globular domain and, remarkably, the E7 N-terminal intrinsically disordered domain stabilizes the oligomer, preventing an insoluble amyloid route. Conclusion We described a controlled ordered mechanism with features in common with soluble amyloid precursors, chaperones, and other spherical oligomers, thus sharing determining factors for symmetry, size and shape. In addition, such a controlled and discrete polymerization reaction provides a valuable tool for nanotechnological applications. Finally, its increased immunogenicity related to its supramolecular structure is the

  12. Insulin receptor in Drosophila melanogaster

    SciTech Connect

    Petruzzelli, L.; Herrera, R.; Rosen, O.

    1986-05-01

    A specific, high affinity insulin receptor is present in both adult Drosophila and in Drosophila embryos. Wheat germ lectin-enriched extracts of detergent-solubilized membranes from embryos and adults bind insulin with a K/sub d/ of 15 nM. Binding is specific for insulin; micromolar concentrations of proinsulin, IGFI, and IGFII are required to displace bound /sup 125/I-insulin. Insulin-dependent protein tyrosine kinase activity appears during embryogenesis. It is evident between 6 and 12 hours of development, peaks between 12 and 18 hours and falls in the adult. During 0-6 hours of embryogenesis, and in the adult, a specific protein band (Mr = 135,000) is crosslinked to /sup 125/I-insulin. During 6-12 and 12-18 hours of embryogenesis stages in which insulin-dependent protein tyrosine kinase is high, an additional band (Mr = 100,000) becomes crosslinked to /sup 125/I-insulin. Isolation and DNA sequence analysis of genomic clones encoding the Drosophila insulin receptor will be presented as will the characterization of insulin receptor mRNA's during development.

  13. Oligomers, organosulfates, and nitroxy organosulfates in rainwater identified by ultra-high resolution electrospray ionization FT-ICR mass spectrometry

    NASA Astrophysics Data System (ADS)

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

    2008-09-01

    Wet deposition is an important removal mechanism for atmospheric organic matter, and a potentially important input for receiving ecosystems, yet less than 50% 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). Elemental compositions of 552 unique molecular species were determined in the mass range 50 500 Da in the rainwater. Three main groups of organic compounds were identified: compounds containing carbon, hydrogen, and oxygen (CHO) only, sulfur (S) containing CHOS compounds, and S- and nitrogen containing CHONS compounds. Organic acids commonly identified in precipitation were detected, as well as linear alkylbenzene sulfonates, which are persistent pollutants commonly measured in river water, seawater, and sediments, but to our knowledge, not previously documented in atmospheric samples. Within the three main groups of compounds detected in the rainwater, oligomers, organosulfates, and nitroxy-organosulfates were identified. The majority of the compounds identified are products of atmospheric reactions and are known contributors to secondary organic aerosol (SOA) formed from gas phase, aerosol phase, and in-cloud reactions in the atmosphere. It is suggested that the large uncharacterized component of SOA is the main contributor to the large uncharacterized component of rainwater organic matter.

  14. Pitfalls of Insulin Pump Clocks

    PubMed Central

    Reed, Amy J.

    2014-01-01

    The objective was to raise awareness about the importance of ensuring that insulin pumps internal clocks are set up correctly at all times. This is a very important safety issue because all commercially available insulin pumps are not GPS-enabled (though this is controversial), nor equipped with automatically adjusting internal clocks. Special attention is paid to how basal and bolus dose errors can be introduced by daylight savings time changes, travel across time zones, and am-pm clock errors. Correct setting of insulin pump internal clock is crucial for appropriate insulin delivery. A comprehensive literature review is provided, as are illustrative cases. Incorrect setting can potentially result in incorrect insulin delivery, with potential harmful consequences, if too much or too little insulin is delivered. Daylight saving time changes may not significantly affect basal insulin delivery, given the triviality of the time difference. However, bolus insulin doses can be dramatically affected. Such problems may occur when pump wearers have large variations in their insulin to carb ratio, especially if they forget to change their pump clock in the spring. More worrisome than daylight saving time change is the am-pm clock setting. If this setting is set up incorrectly, both basal rates and bolus doses will be affected. Appropriate insulin delivery through insulin pumps requires correct correlation between dose settings and internal clock time settings. Because insulin pumps are not GPS-enabled or automatically time-adjusting, extra caution should be practiced by patients to ensure correct time settings at all times. Clinicians and diabetes educators should verify the date/time of insulin pumps during patients’ visits, and should remind their patients to always verify these settings. PMID:25355713

  15. Insulin and Leptin Relations in Obesity: A Multimedia Approach

    ERIC Educational Resources Information Center

    Yokaichiya, Daniela K.; Galembeck, Eduardo; Torres, Bayardo B.; Da Silva, Jose Antonio; de Araujo, Daniele R.

    2008-01-01

    Obesity has been recognized as a worldwide public health problem. It significantly increases the chances of developing several diseases, including Type II diabetes. The roles of insulin and leptin in obesity involve reactions that can be better understood when they are presented step by step. The aim of this work was to design software with data…

  16. Glycosyl-Templated Chiral Helix Stapling of Ethynylpyridine Oligomers by Alkene Metathesis between Inter-Pitch Side Chains.

    PubMed

    Abe, Hajime; Kayamori, Fumihiro; Inouye, Masahiko

    2015-06-22

    Ethynylpyridine polymers and oligomers consisting of 4-substituted pyridine rings linked by acetylene bonds at the 2- and 6-positions have been investigated. Ethynylpyridine oligomers covalently linked with a glycosyl chiral template form chiral helical complexes by intramolecular hydrogen bonding, in which the chirality of the template is translated to the helix. With a view to fixation of the chiral architecture, D/L-galactosyl- and D/L-mannosyl-linked ethynylpyridine oligomers have been developed with 4-(3-butenyloxy)pyridine units having alkene side chains. The helical structures are successfully stapled by alkene metathesis of the side chains. Subsequent removal of the chiral templates by acidolysis produces template-free stapled oligomers. The chiral, template-free, stapled oligomers show chiral helicity, which is resistant to polar solvents and heating.

  17. 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.

  18. Linking Functional Domains of the Human Insulin Receptor with the Bacterial Aspartate Receptor

    NASA Astrophysics Data System (ADS)

    Ellis, Leland; Morgan, David O.; Koshland, Daniel E.; Clauser, Eric; Moe, Gregory R.; Bollag, Gideon; Roth, Richard A.; Rutter, William J.

    1986-11-01

    A hybrid receptor has been constructed that is composed of the extracellular domain of the human insulin receptor fused to the transmembrane and cytoplasmic domains of the bacterial aspartate chemoreceptor. This hybrid protein can be expressed in rodent (CHO) cells and displays several functional features comparable to wild-type insulin receptor. It is localized to the cell surface, binds insulin with high affinity, forms oligomers, and is recognized by conformation-specific monoclonal antibodies. Although most of the expressed protein accumulates as a 180-kDa proreceptor, some processed 135-kDa receptor can be detected on the cell surface by covalent cross-linking. Expression of the hybrid receptor inhibits the insulin-activated uptake of 2-deoxyglucose by CHO cells. Thus, this hybrid is partially functional and can be processed; however, it is incapable of native transmembrane signaling. The results indicate that the intact domains of different types of receptors can retain some of the native features in a hybrid molecule but specific requirements will need to be satisfied for transmembrane signaling.

  19. Colon targeting: an emerging frontier for oral insulin delivery.

    PubMed

    Patel, Mayur Mahendrakumar

    2013-06-01

    Subcutaneous administration of insulin is associated with several limitations such as discomfort, local pain, irritation, infections, immune reactions and lipoatrophy as well as lipohypertrophy manifestations at the injection site. To overcome these drawbacks, enormous research is currently going on worldwide for designing of an alternative noninvasive route of administration. Pulmonary and oral route seem to be the most promising ones, with respect to the market value. However, after the letdown by pulmonary delivery of insulin, oral colon targeted delivery of insulin has gained tremendous interest among researchers. Although bioavailability remains a challenge for oral colon specific delivery of insulin, the employment of protease inhibitors, permeation enhancers and polymeric delivery systems have proved to be advantageous to overcome the said problem. This Editorial article is not intended to offer a comprehensive review on drug delivery, but shall familiarize the readers with the strategies employed for attaining non-erratic bioavailability of insulin, and to highlight some of the formulation technologies that have been developed for attaining oral colon-specific delivery of insulin.

  20. Ligand-dependent intersubunit association with the insulin receptor complex activates its intrinsic kinase activity

    SciTech Connect

    Boeni-Schnetzler, M.; Kaligian, A.; DelVecchio, R.; Pilch, P.F.

    1988-05-15

    Insulin receptor halves (..cap alpha beta..) were obtained upon selective reduction of the holoreceptor (..cap alpha../sub 2/..beta../sub 2/) and were isolated in concentrated form. Autophosphorylation of concentrated ..cap alpha beta.. receptor halves can be stimulated by insulin an average of 4.0-fold, whereas nonreduced holoreceptor can be stimulated 5.4-fold. If ..cap alpha beta.. half-receptors are immobilized on wheat germ agglutinin-agarose, no insulin-stimulated autophosphorylation is observed, whereas immobilized holoreceptor retains insulin responsiveness. Treatment of ..cap alpha beta.. half-receptors with glutathione in the presence of insulin results in reoxidation to the holoreceptor form (..cap alpha../sub 2/..beta../sub 2/) with an efficiency of 60-70% as visualized by immunoblotting, thus providing evidence that two ..cap alpha beta.. halves are in close physical proximity. This reoxidation reaction, which is evident prior to autophosphorylation, is rapid and strictly dependent on the presence of insulin, consistent with the hypothesis that insulin promotes the association of two ..cap alpha beta.. halves. Furthermore, the insulin-induced reoxidation reaction and the insulin-induced autophosphorylation show the same dose dependence suggesting that the noncovalent association of ..cap alpha beta.. half-receptors upon insulin binding is a prerequisite for insulin-stimulated autophosphorylation in concentrated ..gamma beta.. half-receptor preparations. If the ..cap alpha beta.. half-receptor forms are phosphorylated in the presence of an anti-phosphotyrosine antibody and separated from nonphosphorylated ..cap alpha beta.. receptors, we observe that the phosphorylated ..cap alpha beta.. receptor halves contain bound insulin.

  1. Protein Crystal Recombinant Human Insulin

    NASA Technical Reports Server (NTRS)

    1994-01-01

    The comparison of protein crystal, Recombiant Human Insulin; space-grown (left) and earth-grown (right). On STS-60, Spacehab II indicated that space-grown crystals are larger and of greater optical clarity than their earth-grown counterparts. Recombiant Human Insulin facilitates the incorporation of glucose into cells. In diabetics, there is either a decrease in or complete lack of insulin, thereby leading to several harmful complications. Principal Investigator is Larry DeLucas.

  2. Insulin signal transduction pathways and insulin-induced gene expression.

    PubMed

    Keeton, Adam B; Amsler, Maggie O; Venable, Derwei Y; Messina, Joseph L

    2002-12-13

    Insulin regulates metabolic activity, gene transcription, and cell growth by modulating the activity of several intracellular signaling pathways. Insulin activation of one mitogen-activated protein kinase cascade, the MEK/ERK kinase cascade, is well described. However, the effect of insulin on the parallel p38 pathway is less well understood. The present work examines the effect of inhibiting the p38 signaling pathway by use of specific inhibitors, either alone or in combination with insulin, on the activation of ERK1/2 and on the regulation of gene transcription in rat hepatoma cells. Activation of ERK1/2 was induced by insulin and was dependent on the activation of MEK1, the kinase upstream of ERK in this pathway. Treatment of cells with p38 inhibitors also induced ERK1/2 activation/phosphorylation. The addition of p38 inhibitors followed by insulin addition resulted in a greater than additive activation of ERK1/2. The two genes studied, c-Fos and Pip92, are immediate-early genes that are dependent on the ERK1/2 pathway for insulin-regulated induction because the insulin effect was inhibited by pretreatment with a MEK1 inhibitor. The addition of p38 inhibitors induced transcription of both genes in a dose-dependent manner, and insulin stimulation of both genes was enhanced by prior treatment with p38 inhibitors. The ability of the p38 inhibitors to induce ERK1/2 and gene transcription, both alone and in combination with insulin, was abolished by prior inhibition of MEK1. These data suggest possible cross-talk between the p38 and ERK1/2 signaling pathways and a potential role of p38 in insulin signaling.

  3. Lipid mediators of insulin resistance.

    PubMed

    Holland, William L; Knotts, Trina A; Chavez, Jose A; Wang, Li-Ping; Hoehn, Kyle L; Summers, Scott A

    2007-06-01

    Lipid abnormalities such as obesity, increased circulating free fatty acid levels, and excess intramyocellular lipid accumulation are frequently associated with insulin resistance. These observations have prompted investigators to speculate that the accumulation of lipids in tissues not suited for fat storage (e.g., skeletal muscle and liver) is an underlying component of insulin resistance and the metabolic syndrome. We review the metabolic fates of lipids in insulin-responsive tissues and discuss the roles of specific lipid metabolites (e.g., ceramides, GM3 ganglioside, and diacylglycerol) as antagonists of insulin signaling and action.

  4. The synthesis, characterization, and structure-property relationships of regioregular 4,4'-dialkyl-2,2'-bithiazole oligomers and polymers

    NASA Astrophysics Data System (ADS)

    Nanos, John I.

    2005-12-01

    The 4,4'-dialkyl-2,2'-bithiazole moiety can be efficiently coupled to produce well-defined oligomers or block co-oligomers via Stille reactions of mono-bromo and tin substituted precursors. Dehalogenative polycondensations produce high molecular weight homo-polymers and Stille coupling of dibromo and di-tin monomers yields alternating copolymers. The symmetry of the bithiazole monomeric unit produces regioregular oligomers and polymers with the HH-TT dyad sequence. Model compound oligomers were synthesized and studied to explore the progression of structure property relationships with main chain extension. DSC measurements indicate the potential presence of at least three phases in solution cast thin films---the disordered isotropic melt, a stable low temperature morphology designated the alpha-phase, and a high temperature meta-stable morphology designated the beta-phase. Melt transition temperatures are inversely proportional to side alkyl chain length and directly proportional to main chain length and the interplay between the two effects greatly influences the observed thermochromism. Temperature dependent IR studies show an increase in the gauche conformations of the side chains at the low temperature alpha-beta phase transition and main chain twisting at the beta-isotropic transition. The onset of side chain and main chain motion at these phase transition temperatures was confirmed with variable temperature solid state NMR. Temperature dependent XRD results indicate the presence of a solid-to-solid crystal phase change at the low temperature transition followed by formation of preferred orientations of the beta and alpha ordered phases upon cooling from the isotropic melt. The solid-to-solid crystal phase transition is triggered by the increased motion of the side chains, and the magnitude of the intermolecular side chain packing forces dictate if the transitions occur cooperatively (observed isosbestic point) or as isolated events. Comparison with the 3

  5. A strategy for designing a peptide probe for detection of β-amyloid oligomers.

    PubMed

    Hu, Yang; Su, Baihao; Kim, Chung-Sei; Hernandez, Michael; Rostagno, Agueda; Ghiso, Jorge; Kim, Jin Ryoun

    2010-11-22

    Aggregation of β-amyloid (Aβ) is implicated in the pathology of Alzheimer's disease. Development of a robust strategy to detect Aβ oligomeric intermediates, which have been identified as significant toxic agents, would be highly beneficial in the screening of drug candidates as well as enhancing our understanding of Aβ oligomerization. Rapid, specific and quantitative detection, currently unavailable, would be highly preferred for accurate and reliable probing of transient Aβ oligomers. Here, we report the development of a novel peptide probe, PG46, based on the nature of Aβ self-assembly and the conformation-sensitive fluorescence of the biarsenical dye, FlAsH. PG46 was found to bind to Aβ oligomers and displayed an increase in FlAsH fluorescence upon binding. No such event was observed when PG46 was co-incubated with Aβ low-molecular-weight species or Aβ fibrils. Aβ oligomer detection was fast, and occurred within one hour without any additional sample incubation or preparation. We anticipate that the development of a strategy for detection of amyloid oligomers described in this study will be directly relevant to a host of other amyloidogenic proteins.

  6. 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.

  7. 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.

  8. 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

    2015-07-03

    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.

  9. 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

    2015-11-05

    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.

  10. 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.

  11. 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...

  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.

  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. Structural characterization of toxic oligomers that are kinetically trapped during α-synuclein fibril formation.

    PubMed

    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

    2015-04-21

    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.

  15. An update on the physiological and therapeutic relevance of GPCR oligomers.

    PubMed

    Farran, Batoul

    2017-03-01

    The traditional view on GPCRs held that they function as single monomeric units composed of identical subunits. This notion was overturned by the discovery that GPCRs can form homo- and hetero-oligomers, some of which are obligatory, and can further assemble into receptor mosaics consisting of three or more protomers. Oligomerisation exerts significant impacts on receptor function and physiology, offering a platform for the diversification of receptor signalling, pharmacology, regulation, crosstalk, internalization and trafficking. Given their involvement in the modulation of crucial physiological processes, heteromers could constitute important therapeutic targets for a wide range of diseases, including schizophrenia, Parkinson's disease, substance abuse or obesity. This review aims at depicting the current developments in GPCR oligomerisation research, documenting various class A, B and C GPCR heteromers detected in vitro and in vivo using biochemical and biophysical approaches, as well as recently identified higher-order oligomeric complexes. It explores the current understanding of dimerization dynamics and the possible interaction interfaces that drive oligomerisation. Most importantly, it provides an inventory of the wide range of physiological processes and pathophysiological conditions to which GPCR oligomers contribute, surveying some of the oligomers that constitute potential drug targets. Finally, it delineates the efforts to develop novel classes of ligands that specifically target and tether to receptor oligomers instead of a single monomeric entity, thus ameliorating their ability to modulate GPCR function.

  16. The Role of Initial Oligomers in Amyloid Fibril Formation by Human Stefin B

    PubMed Central

    Taler-Verčič, Ajda; Kirsipuu, Tiina; Friedemann, Merlin; Noormägi, Andra; Polajnar, Mira; Smirnova, Julia; Žnidarič, Magda Tušek; Žganec, Matjaž; Škarabot, Miha; Vilfan, Andrej; Staniforth, Rosemary A.; Palumaa, Peep; Žerovnik, Eva

    2013-01-01

    Oligomers are commonly observed intermediates at the initial stages of amyloid fibril formation. They are toxic to neurons and cause decrease in neural transmission and long-term potentiation. We describe an in vitro study of the initial steps in amyloid fibril formation by human stefin B, which proved to be a good model system. Due to relative stability of the initial oligomers of stefin B, electrospray ionization mass spectrometry (ESI MS) could be applied in addition to size exclusion chromatography (SEC). These two techniques enabled us to separate and detect distinguished oligomers from the monomers: dimers, trimers, tetramers, up to decamers. The amyloid fibril formation process was followed at different pH and temperatures, including such conditions where the process was slow enough to detect the initial oligomeric species at the very beginning of the lag phase and those at the end of the lag phase. Taking into account the results of the lower-order oligomers transformations early in the process, we were able to propose an improved model for the stefin B fibril formation. PMID:24013380

  17. 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.

  18. Alzheimer's disease-type neuronal tau hyperphosphorylation induced by Aβ oligomers

    PubMed Central

    De Felice, Fernanda G.; Wu, Diana; Lambert, Mary P.; Fernandez, Sara J.; Velasco, Pauline T.; Lacor, Pascale N.; Bigio, Eileen H.; Jerecic, Jasna; Acton, Paul J.; Shughrue, Paul J.; Chen-Dodson, Elizabeth; Kinney, Gene G.; Klein, William L.

    2008-01-01

    Alzheimer’s disease (AD) is characterized by presence of extracellular fibrillar Aβ in amyloid plaques, intraneuronal neurofibrillary tangles consisting of aggregated hyperphosphorylated tau and elevated brain levels of soluble Aβ oligomers (ADDLs). A major question is how these disparate facets of AD pathology are mechanistically related. Here we show that, independent of the presence of fibrils, ADDLs stimulate tau phosphorylation in mature cultures of hippocampal neurons and in neuroblastoma cells at epitopes characteristically hyperphosphorylated in AD. A monoclonal antibody that targets ADDLs blocked their attachment to synaptic binding sites and prevented tau hyperphosphorylation. Tau phosphorylation was blocked by the Src family tyrosine kinase inhibitor, 4-amino-5-(4-chlorophenyl)-7(t-butyl)pyrazol(3,4-D)pyramide (PP1), and by the phosphatidylinositol-3-kinase inhibitor LY294002. Significantly, tau hyperphosphorylation was also induced by a soluble aqueous extract containing Aβ oligomers from AD brains, but not by an extract from non-AD brains. Aβ oligomers have been increasingly implicated as the main neurotoxins in AD, and the current results provide a unifying mechanism in which oligomer activity is directly linked to tau hyperphosphorylation in AD pathology. PMID:17403556

  19. Enhanced Volatile Organic Compounds emissions and organic aerosol mass increase the oligomer content of atmospheric aerosols.

    PubMed

    Kourtchev, Ivan; Giorio, Chiara; Manninen, Antti; Wilson, Eoin; Mahon, Brendan; Aalto, Juho; Kajos, Maija; Venables, Dean; Ruuskanen, Taina; Levula, Janne; Loponen, Matti; Connors, Sarah; Harris, Neil; Zhao, Defeng; Kiendler-Scharr, Astrid; Mentel, Thomas; Rudich, Yinon; Hallquist, Mattias; Doussin, Jean-Francois; Maenhaut, Willy; Bäck, Jaana; Petäjä, Tuukka; Wenger, John; Kulmala, Markku; Kalberer, Markus

    2016-10-13

    Secondary organic aerosol (SOA) accounts for a dominant fraction of the submicron atmospheric particle mass, but knowledge of the formation, composition and climate effects of SOA is incomplete and limits our understanding of overall aerosol effects in the atmosphere. Organic oligomers were discovered as dominant components in SOA over a decade ago in laboratory experiments and have since been proposed to play a dominant role in many aerosol processes. However, it remains unclear whether oligomers are relevant under ambient atmospheric conditions because they are often not clearly observed in field samples. Here we resolve this long-standing discrepancy by showing that elevated SOA mass is one of the key drivers of oligomer formation in the ambient atmosphere and laboratory experiments. We show for the first time that a specific organic compound class in aerosols, oligomers, is strongly correlated with cloud condensation nuclei (CCN) activities of SOA particles. These findings might have important implications for future climate scenarios where increased temperatures cause higher biogenic volatile organic compound (VOC) emissions, which in turn lead to higher SOA mass formation and significant changes in SOA composition. Such processes would need to be considered in climate models for a realistic representation of future aerosol-climate-biosphere feedbacks.

  20. 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

  1. Stabilizing Off-pathway Oligomers by Polyphenol Nanoassemblies for IAPP Aggregation Inhibition

    NASA Astrophysics Data System (ADS)

    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.

  2. 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.

  3. WASP-1, a canonical Wnt signaling potentiator, rescues hippocampal synaptic impairments induced by Aβ oligomers.

    PubMed

    Vargas, Jessica Y; Ahumada, Juan; Arrázola, Macarena S; Fuenzalida, Marco; Inestrosa, Nibaldo C

    2015-02-01

    Amyloid-β (Aβ) oligomers are a key factor in Alzheimer's disease (AD)-associated synaptic dysfunction. Aβ oligomers block the induction of hippocampal long-term potentiation (LTP) in rodents. The activation of Wnt signaling prevents Aβ oligomer-induced neurotoxic effects. The compound WASP-1 (Wnt-activating small molecule potentiator-1), has been described as a synergist of the ligand Wnt-3a, enhancing the activation of Wnt/β-catenin signaling. Herein, we report that WASP-1 administration successfully rescued Aβ-induced synaptic impairments both in vitro and in vivo. The activation of canonical Wnt/β-catenin signaling by WASP-1 increased synaptic transmission and rescued hippocampal LTP impairments induced by Aβ oligomers. Additionally, intra-hippocampal administration of WASP-1 to the double transgenic APPswe/PS1dE9 mouse model of AD prevented synaptic protein loss and reduced tau phosphorylation levels. Moreover, we found that WASP-1 blocked Aβ aggregation in vitro and reduced pathological tau phosphorylation in vivo. These results indicate that targeting canonical Wnt signaling with WASP-1 could have value for treating AD.

  4. Enhanced Volatile Organic Compounds emissions and organic aerosol mass increase the oligomer content of atmospheric aerosols

    NASA Astrophysics Data System (ADS)

    Kourtchev, Ivan; Giorio, Chiara; Manninen, Antti; Wilson, Eoin; Mahon, Brendan; Aalto, Juho; Kajos, Maija; Venables, Dean; Ruuskanen, Taina; Levula, Janne; Loponen, Matti; Connors, Sarah; Harris, Neil; Zhao, Defeng; Kiendler-Scharr, Astrid; Mentel, Thomas; Rudich, Yinon; Hallquist, Mattias; Doussin, Jean-Francois; Maenhaut, Willy; Bäck, Jaana; Petäjä, Tuukka; Wenger, John; Kulmala, Markku; Kalberer, Markus

    2016-10-01

    Secondary organic aerosol (SOA) accounts for a dominant fraction of the submicron atmospheric particle mass, but knowledge of the formation, composition and climate effects of SOA is incomplete and limits our understanding of overall aerosol effects in the atmosphere. Organic oligomers were discovered as dominant components in SOA over a decade ago in laboratory experiments and have since been proposed to play a dominant role in many aerosol processes. However, it remains unclear whether oligomers are relevant under ambient atmospheric conditions because they are often not clearly observed in field samples. Here we resolve this long-standing discrepancy by showing that elevated SOA mass is one of the key drivers of oligomer formation in the ambient atmosphere and laboratory experiments. We show for the first time that a specific organic compound class in aerosols, oligomers, is strongly correlated with cloud condensation nuclei (CCN) activities of SOA particles. These findings might have important implications for future climate scenarios where increased temperatures cause higher biogenic volatile organic compound (VOC) emissions, which in turn lead to higher SOA mass formation and significant changes in SOA composition. Such processes would need to be considered in climate models for a realistic representation of future aerosol-climate-biosphere feedbacks.

  5. 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…

  6. 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…

  7. Synthesis and Properties of Bis(aniline, methyl)siloxy-octaphenylsilsesquioxane Modified Thermosetting Polyimide Oligomers

    DTIC Science & Technology

    2011-08-19

    Conference Paper 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Synthesis and Properties of Bis( aniline , methyl)siloxy...SYNTHESIS AND PROPERTIES OF BIS( ANILINE , METHYL)SILOXY-OCTAPHENYLSILSESQUIOXANE MODIFIED THERMOSETTING POLYIMIDE OLIGOMERS Gregory R. Yandek1...oxydiphenylene aniline (Kapton™) reduced its moisture uptake by 83% concurrently improving mechanical properties.4 The objective of this work is to

  8. 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

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

    PubMed

    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.

  10. Enhanced Volatile Organic Compounds emissions and organic aerosol mass increase the oligomer content of atmospheric aerosols

    PubMed Central

    Kourtchev, Ivan; Giorio, Chiara; Manninen, Antti; Wilson, Eoin; Mahon, Brendan; Aalto, Juho; Kajos, Maija; Venables, Dean; Ruuskanen, Taina; Levula, Janne; Loponen, Matti; Connors, Sarah; Harris, Neil; Zhao, Defeng; Kiendler-Scharr, Astrid; Mentel, Thomas; Rudich, Yinon; Hallquist, Mattias; Doussin, Jean-Francois; Maenhaut, Willy; Bäck, Jaana; Petäjä, Tuukka; Wenger, John; Kulmala, Markku; Kalberer, Markus

    2016-01-01

    Secondary organic aerosol (SOA) accounts for a dominant fraction of the submicron atmospheric particle mass, but knowledge of the formation, composition and climate effects of SOA is incomplete and limits our understanding of overall aerosol effects in the atmosphere. Organic oligomers were discovered as dominant components in SOA over a decade ago in laboratory experiments and have since been proposed to play a dominant role in many aerosol processes. However, it remains unclear whether oligomers are relevant under ambient atmospheric conditions because they are often not clearly observed in field samples. Here we resolve this long-standing discrepancy by showing that elevated SOA mass is one of the key drivers of oligomer formation in the ambient atmosphere and laboratory experiments. We show for the first time that a specific organic compound class in aerosols, oligomers, is strongly correlated with cloud condensation nuclei (CCN) activities of SOA particles. These findings might have important implications for future climate scenarios where increased temperatures cause higher biogenic volatile organic compound (VOC) emissions, which in turn lead to higher SOA mass formation and significant changes in SOA composition. Such processes would need to be considered in climate models for a realistic representation of future aerosol-climate-biosphere feedbacks. PMID:27733773

  11. DOPAL derived alpha-synuclein oligomers impair synaptic vesicles physiological function

    PubMed Central

    Plotegher, N.; Berti, G.; Ferrari, E.; Tessari, I.; Zanetti, M.; Lunelli, L.; Greggio, E.; Bisaglia, M.; Veronesi, M.; Girotto, S.; Dalla Serra, M.; Perego, C.; Casella, L.; Bubacco, L.

    2017-01-01

    Parkinson’s disease is a neurodegenerative disorder characterized by the death of dopaminergic neurons and by accumulation of alpha-synuclein (aS) aggregates in the surviving neurons. The dopamine catabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL) is a highly reactive and toxic molecule that leads to aS oligomerization by covalent modifications to lysine residues. Here we show that DOPAL-induced aS oligomer formation in neurons is associated with damage of synaptic vesicles, and with alterations in the synaptic vesicles pools. To investigate the molecular mechanism that leads to synaptic impairment, we first aimed to characterize the biochemical and biophysical properties of the aS-DOPAL oligomers; heterogeneous ensembles of macromolecules able to permeabilise cholesterol-containing lipid membranes. aS-DOPAL oligomers can induce dopamine leak in an in vitro model of synaptic vesicles and in cellular models. The dopamine released, after conversion to DOPAL in the cytoplasm, could trigger a noxious cycle that further fuels the formation of aS-DOPAL oligomers, inducing neurodegeneration. PMID:28084443

  12. Structural Insights into Amyloid Oligomers of the Parkinson Disease-related Protein α-Synuclein*

    PubMed Central

    Gallea, J. Ignacio; Celej, M. Soledad

    2014-01-01

    The presence of intraneuronal deposits mainly formed by amyloid fibrils of the presynaptic protein α-synuclein (AS) is a hallmark of Parkinson disease. Currently, neurotoxicity is attributed to prefibrillar oligomeric species rather than the insoluble aggregates, although their mechanisms of toxicity remain elusive. Structural details of the supramolecular organization of AS oligomers are critically needed to decipher the structure-toxicity relationship underlying their pathogenicity. In this study, we employed site-specific fluorescence to get a deeper insight into the internal architecture of AS oligomeric intermediates. We demonstrate that AS oligomers are ordered assemblies possessing a well defined pattern of intermolecular contacts. Some of these contacts involve regions that form the β-sheet core in the fibrillar state, although their spatial arrangement may differ in the two aggregated forms. However, even though the two termini are excluded from the fibrillar core, they are engaged in a number of intermolecular interactions within the oligomer. Therefore, substantial structural remodeling of early oligomeric interactions is essential for fibril growth. The intermolecular contacts identified in AS oligomers can serve as targets for the rational design of anti-amyloid compounds directed at preventing oligomeric interactions/reorganizations. PMID:25143382

  13. Glycan arrays containing synthetic Clostridium difficile lipoteichoic acid oligomers as tools toward a carbohydrate vaccine.

    PubMed

    Martin, Christopher E; Broecker, Felix; Eller, Steffen; Oberli, Matthias A; Anish, Chakkumkal; Pereira, Claney L; Seeberger, Peter H

    2013-08-18

    Clostridium difficile is a leading cause of severe nosocomial infections. Cell-surface carbohydrate antigens are promising vaccine candidates. Here we report the first total synthesis of oligomers of the lipoteichoic acid antigen repeating unit. Synthetic glycan microarrays revealed anti-glycan antibodies in the blood of patients that help to define epitopes for vaccine development.

  14. Facile Synthesis of Highly Crystalline and Large Areal Hexagonal Boron Nitride from Borazine Oligomers

    NASA Astrophysics Data System (ADS)

    Park, Sungchan; Seo, Tae Hoon; Cho, Hyunjin; Min, Kyung Hyun; Lee, Dong Su; Won, Dong-Il; Kang, Sang Ook; Kim, Myung Jong

    2017-01-01

    A novel and facile synthetic method for h-BN films from borazine oligomer (B3N3H4)x precursors has been developed. This method only includes spin-coating of borazine oligomer onto nickel catalysts and a subsequent annealing step. Large areal and highly crystalline h-BN films were obtained. The stoichiometric B/N ratio of borazine oligomer precursor was preserved in the final h-BN product such that it was close to 1 as revealed by XPS. Catalytic effect of nickel for h-BN formation was clearly demonstrated by lowering crystallization temperature compared to the growth condition in the absence of catalyst. The graphene field effect transistor (GFET) characterization has proved the high quality synthesis of h-BN films, showing the shift of neutrality point and the increase of the mobility. This method can also provide functional h-BN coating on various surfaces by annealing Ni-coated borazine oligomer films and subsequent removal of Ni catalyst.

  15. 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

  16. Synthesis of DNA mimics representing HypNA-pPNA hetero-oligomers.

    PubMed

    Efimov, Vladimir A; Chakhmakhcheva, Oksana G

    2005-01-01

    The methods for the synthesis and purification of negatively charged peptide nucleic acid (PNA)-relative deoxyribonucleic acid (DNA) mimics containing alternating residues of phosphono peptide nucleic acid (pPNA) monomers and PNA-like monomers on the base of trans-4-hydroxy-L-proline are described. Examples of the chimeric oligomers hybridization with complementary DNA and ribonucleic acid fragments are demonstrated.

  17. Facile Synthesis of Highly Crystalline and Large Areal Hexagonal Boron Nitride from Borazine Oligomers

    PubMed Central

    Park, Sungchan; Seo, Tae Hoon; Cho, Hyunjin; Min, Kyung Hyun; Lee, Dong Su; Won, Dong-Il; Kang, Sang Ook; Kim, Myung Jong

    2017-01-01

    A novel and facile synthetic method for h-BN films from borazine oligomer (B3N3H4)x precursors has been developed. This method only includes spin-coating of borazine oligomer onto nickel catalysts and a subsequent annealing step. Large areal and highly crystalline h-BN films were obtained. The stoichiometric B/N ratio of borazine oligomer precursor was preserved in the final h-BN product such that it was close to 1 as revealed by XPS. Catalytic effect of nickel for h-BN formation was clearly demonstrated by lowering crystallization temperature compared to the growth condition in the absence of catalyst. The graphene field effect transistor (GFET) characterization has proved the high quality synthesis of h-BN films, showing the shift of neutrality point and the increase of the mobility. This method can also provide functional h-BN coating on various surfaces by annealing Ni-coated borazine oligomer films and subsequent removal of Ni catalyst. PMID:28074854

  18. 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.

  19. Cell-mediated immunity to insulin: a new criterion for differentiation of diabetes mellitus?

    PubMed

    Asfandiyarova, Nailya S

    2012-03-01

    Any classification is a step forward and it should help to determine the reason, the course, the prognosis, the treatment of a disease. The current classification of diabetes mellitus (DM) is really very convenient for work, but it has some drawbacks, and the absence of differentiation of type 2 diabetes is the main. The problem is the absence of an adequate criterion, based on pathogenesis for differentiation. We suppose that cell mediated immunity (CMI) to insulin plays the central role in the diabetes genesis. Autoimmune process may be triggered by viruses family Paramyxoviridae, in 10-20% of type 1 diabetes patients the disease is a consequence of direct cytotoxic effect of other viruses to the islet cells of pancreas. In acute phase of viral infection (measles, mumps, parainfluenza) CMI against viruses is developed, in some patients CMI to insulin appeared. We suppose that autoimmune reactions in these cases are the result of cross reaction between viral antigens and insulin. The majorities of patients suppress these reactions and recover from acute infection diseases with the antiviral immunity development and without any complications. Other patients are not able to suppress autoimmune reactions to insulin and pathological process is triggered. Type 1A diabetes is a result of direct CMI to insulin, and this process is responsible for beta-cells destruction; may be type 1B DM is due to the direct cytotoxic effect of other viruses or toxins to them. Some patients with acute viral infection cannot destroy the aggressive clone and they suppress autoimmune reaction to insulin by prostaglandin synthesizing cells (PGSC) or сells with histamine receptors (CHR). As a result of this process the insulin resistance is developed, because these cells or their cytokines form a block to the insulin receptors not only on immunocompetent cells, but in insulin sensitive tissues too. Patients with different reactions to insulin have different courses and outcomes of DM. We

  20. Reactions of stabilized Criegee Intermediates

    NASA Astrophysics Data System (ADS)

    Vereecken, Luc; Harder, Hartwig; Novelli, Anna

    2014-05-01

    Carbonyl oxides (Criegee intermediates) were proposed as key intermediates in the gas phase ozonolysis of alkenes in 1975 by Rudolf Criegee. Despite the importance of ozonolysis in atmospheric chemistry, direct observation of these intermediates remained elusive, with only indirect experimental evidence for their role in the oxidation of hydrocarbons, e.g. through scavenging experiments. Direct experimental observation of stabilized CI has only been achieved since 2008. Since then, a concerted effort using experimental and theoretical means is in motion to characterize the chemistry and kinetics of these reactive intermediates. We present the results of theoretical investigations of the chemistry of Criegee intermediates with a series of coreactants which may be of importance in the atmosphere, in experimental setups, or both. This includes the CI+CI cross-reaction, which proceeds with a rate coefficient near the collision limit and can be important in experimental conditions. The CI + alkene reactions show strong dependence of the rate coefficient depending on the coreactants, but is generally found to be rather slow. The CI + ozone reaction is sufficiently fast to occur both in experiment and the free troposphere, and acts as a sink for CI. The reaction of CI with hydroperoxides, ROOH, is complex, and leads both to the formation of oligomers, as to the formation of reactive etheroxides, with a moderately fast rate coefficient. The importance of these reactions is placed in the context of the reaction conditions in different atmospheric environments ranging from unpolluted to highly polluted.

  1. Oligomeric Forms of Insulin Amyloid Aggregation Disrupt Outgrowth and Complexity of Neuron-Like PC12 Cells

    PubMed Central

    Kachooei, Ehsan; Moosavi-Movahedi, Ali Akbar; Khodagholi, Fariba; Ramshini, Hassan; Shaerzadeh, Fatemeh; Sheibani, Nader

    2012-01-01

    Formation of protein amyloid fibrils consists of a series of intermediates including oligomeric aggregates, proto-fibrillar structures, and finally mature fibrils. Recent studies show higher toxicity for oligomeric and proto-fibrillar intermediates of protein relative to their mature fibrils. Here the kinetic of the insulin amyloid fibrillation was evaluated using a variety of techniques including ThT fluorescence, Congo red absorbance, circular dichroism, and atomic force microscopy (AFM). The solution surface tension changes were attributed to hydrophobic changes in insulin structure and were detected by Du Noüy Ring method. Determination of the surface tension of insulin oligomeric, proto-fibrillar and fibrillar forms indicated that the hydrophobicity of solution is enhanced by the formation of the oligomeric forms of insulin compared to other forms. In order to investigate the toxicity of the different forms of insulin we monitored morphological alterations of the differentiated neuron-like PC12 cells following incubation with native, oligomeric aggregates, proto-fibrillar, and fibrillar forms of insulin. The cell body area, average neurite length, neurite width, number of primary neurites, and percent of bipolar cells and node/primary neurite ratios were used to assess the growth and complexity of PC12 cells exposed to different forms of insulin. We observed that the oligomeric form of insulin impaired the growth and complexity of PC12 cells compared to other forms. Together our data suggest that the lower surface tension of oligomers and their perturbation affects the morphology of PC12 cells, mainly due to their enhanced hydrophobicity and detergent-like structures. PMID:22848469

  2. Intensive Insulin Therapy: Tight Blood Sugar Control

    MedlinePlus

    ... insulin therapy can help you achieve desired blood sugar control and what intensive insulin therapy requires of ... aggressive treatment approach designed to control your blood sugar levels. Intensive insulin therapy requires close monitoring of ...

  3. Novel chemo-enzymatic oligomers of cinnamic acids as direct and indirect inhibitors of coagulation proteinases.

    PubMed

    Monien, Bernhard H; Henry, Brian L; Raghuraman, Arjun; Hindle, Michael; Desai, Umesh R

    2006-12-01

    Thrombin and factor Xa, two important procoagulant enzymes, have been prime targets for regulation of clotting through the direct and indirect mechanism of inhibition. Our efforts on exploiting the indirect mechanism led us to study a carboxylic acid-based scaffold, which displayed major acceleration in the inhibition of these enzymes [J. Med. Chem.2005, 48, 1269, 5360]. This work advances the study to chemo-enzymatically prepared oligomers of 4-hydroxycinnamic acids, DHPs, which display interesting anticoagulant properties. Oligomers, ranging in size from tetramers to pentadecamers, were prepared through peroxidase-catalyzed oxidative coupling of caffeic, ferulic, and sinapic acids, and sulfated using triethylamine-sulfur trioxide complex. Chromatographic, spectroscopic, and elemental studies suggest that the DHPs are heterogeneous, polydisperse preparations composed of inter-monomer linkages similar to those found in natural lignins. Measurement of activated thromboplastin and prothrombin time indicates that both the sulfated and unsulfated derivatives of the DHPs display anticoagulant activity, which is dramatically higher than that of the reference polyacrylic acids. More interestingly, this activity approaches that of low-molecular-weight heparin with the sulfated derivative showing approximately 2- to 3-fold greater potency than the unsulfated parent. Studies on the inhibition of factor Xa and thrombin indicate that the oligomers exert their anticoagulant effect through both direct and indirect inhibition mechanisms. This dual inhibition property of 4-hydroxycinnamic acid-based DHP oligomers is the first example in inhibitors of coagulation. This work puts forward a novel, non-heparin structure, which may be exploited for the design of potent, dual action inhibitors of coagulation through combinatorial virtual screening on a library of DHP oligomers.

  4. PrPSc-Specific Antibodies with the Ability to Immunodetect Prion Oligomers

    PubMed Central

    Tayebi, Mourad; Jones, Daryl Rhys; Taylor, William Alexander; Stileman, Benjamin Frederick; Chapman, Charlotte; Zhao, Deming; David, Monique

    2011-01-01

    The development of antibodies with binding capacity towards soluble oligomeric forms of PrPSc recognised in the aggregation process in early stage of the disease would be of paramount importance in diagnosing prion diseases before extensive neuropathology has ensued. As blood transfusion appears to be efficient in the transmission of the infectious prion agent, there is an urgent need to develop reagents that would specifically recognize oligomeric forms of the abnormally folded prion protein, PrPSc. To that end, we show that anti-PrP monoclonal antibodies (called PRIOC mAbs) derived from mice immunised with native PrP-coated microbeads are able to immunodetect oligomers/multimers of PrPSc. Oligomer-specific immunoreactivity displayed by these PRIOC mAbs was demonstrated as large aggregates of immunoreactive deposits in prion-permissive neuroblastoma cell lines but not in equivalent non-infected or prn-p0/0 cell lines. In contrast, an anti-monomer PrP antibody displayed diffuse immunoreactivity restricted to the cell membrane. Furthermore, our PRIOC mAbs did not display any binding with monomeric recombinant and cellular prion proteins but strongly detected PrPSc oligomers as shown by a newly developed sensitive and specific ELISA. Finally, PrioC antibodies were also able to bind soluble oligomers formed of Aβ and α-synuclein. These findings demonstrate the potential use of anti-prion antibodies that bind PrPSc oligomers, recognised in early stage of the disease, for the diagnosis of prion diseases in blood and other body fluids. PMID:21625515

  5. Postsynaptic Receptors for Amyloid-β Oligomers as Mediators of Neuronal Damage in Alzheimer's Disease.

    PubMed

    Dinamarca, Margarita C; Ríos, Juvenal A; Inestrosa, Nibaldo C

    2012-01-01

    The neurotoxic effect of amyloid-β peptide (Aβ) over the central synapses has been described and is reflected in the decrease of some postsynaptic excitatory proteins, the alteration in the number and morphology of the dendritic spines, and a decrease in long-term potentiation. Many studies has been carried out to identify the putative Aβ receptors in neurons, and is still no clear why the Aβ oligomers only affect the excitatory synapses. Aβ oligomers bind to neurite and preferentially to the postsynaptic region, where the postsynaptic protein-95 (PSD-95) is present in the glutamatergic synapse, and interacts directly with the N-methyl-D-aspartate receptor (NMDAR) and neuroligin (NL). NL is a postsynaptic protein which binds to the presynaptic protein, neurexin to form a heterophilic adhesion complex, the disruption of this interaction affects the integrity of the synaptic contact. Structurally, NL has an extracellular domain homolog to acetylcholinesterase, the first synaptic protein that was found to interact with Aβ. In the present review we will document the interaction between Aβ and the extracellular domain of NL-1 at the excitatory synapse, as well as the interaction with other postsynaptic components, including the glutamatergic receptors (NMDA and mGluR5), the prion protein, the neurotrophin receptor, and the α7-nicotinic acetylcholine receptor. We conclude that several Aβ oligomers receptors exist at the excitatory synapse, which could be the responsible for the neurotoxic effect described for the Aβ oligomers. The characterization of the interaction between Aβ receptors and Aβ oligomers could help to understand the source of the neurologic damage observed in the brain of the Alzheimer's disease patients.

  6. Insulin pumps: Beyond basal-bolus.

    PubMed

    Millstein, Richard; Becerra, Nancy Mora; Shubrook, Jay H

    2015-12-01

    Insulin pumps are a major advance in diabetes management, making insulin dosing easier and more accurate and providing great flexibility, safety, and efficacy for people who need basal-bolus insulin therapy. They are the preferred treatment for people with type 1 diabetes and many with type 2 diabetes who require insulin. This article reviews the basics of how insulin pumps work, who benefits from a pump, and how to manage inpatients and outpatients on insulin pumps.

  7. Folding Landscape of Mutant Huntingtin Exon1: Diffusible Multimers, Oligomers and Fibrils, and No Detectable Monomer

    PubMed Central

    Sahoo, Bankanidhi; Arduini, Irene; Drombosky, Kenneth W.; Kodali, Ravindra; Sanders, Laurie H.; Greenamyre, J. Timothy; Wetzel, Ronald

    2016-01-01

    Expansion of the polyglutamine (polyQ) track of the Huntingtin (HTT) protein above 36 is associated with a sharply enhanced risk of Huntington’s disease (HD). Although there is general agreement that HTT toxicity resides primarily in N-terminal fragments such as the HTT exon1 protein, there is no consensus on the nature of the physical states of HTT exon1 that are induced by polyQ expansion, nor on which of these states might be responsible for toxicity. One hypothesis is that polyQ expansion induces an alternative, toxic conformation in the HTT exon1 monomer. Alternative hypotheses posit that the toxic species is one of several possible aggregated states. Defining the nature of the toxic species is particularly challenging because of facile interconversion between physical states as well as challenges to identifying these states, especially in vivo. Here we describe the use of fluorescence correlation spectroscopy (FCS) to characterize the detailed time and repeat length dependent self-association of HTT exon1-like fragments both with chemically synthesized peptides in vitro and with cell-produced proteins in extracts and in living cells. We find that, in vitro, mutant HTT exon1 peptides engage in polyQ repeat length dependent dimer and tetramer formation, followed by time dependent formation of diffusible spherical and fibrillar oligomers and finally by larger, sedimentable amyloid fibrils. For expanded polyQ HTT exon1 expressed in PC12 cells, monomers are absent, with tetramers being the smallest molecular form detected, followed in the incubation time course by small, diffusible aggregates at 6–9 hours and larger, sedimentable aggregates that begin to build up at 12 hrs. In these cell cultures, significant nuclear DNA damage appears by 6 hours, followed at later times by caspase 3 induction, mitochondrial dysfunction, and cell death. Our data thus defines limits on the sizes and concentrations of different physical states of HTT exon1 along the reaction

  8. Role of insulin and insulin receptor in learning and memory.

    PubMed

    Zhao, W Q; Alkon, D L

    2001-05-25

    As one of the most extensively studied protein hormones, insulin and its receptor have been known to play key roles in a variety of important biological functions. Until recent years, the functions of insulin and insulin receptor (IR) in the central nervous system (CNS) have largely remained unclear. IR is abundantly expressed in several specific brain regions that govern fundamental behaviors such as food intake, reproduction and high cognition. The IR from the periphery and CNS exhibit differences in both structure and function. In addition to that from the peripheral system, locally synthesized insulin in the brain has also been identified. Accumulated evidence has demonstrated that insulin/IR plays important roles in associative learning, as suggested by results from both interventive and correlative studies. Interruption of insulin production and IR activity causes deficits in learning and memory formation. Abnormal insulin/IR levels and activities are seen in Alzheimer's dementia, whereas administration of insulin significantly improves the cognitive performance of these patients. The synaptic bases for the action of insulin/IR include modifying neurotransmitter release processes at various types of presynaptic terminals and modulating the activities of both excitatory and inhibitory postsynaptic receptors such as NMDA and GABA receptors, respectively. At the molecular level, insulin/IR participates in regulation of learning and memory via activation of specific signaling pathways, one of which is shown to be associated with the formation of long-term memory and is composed of intracellular molecules including the shc, Grb-r/SOS, Ras/Raf, and MEK/MAP kinases. Cross-talk with another IR pathway involving IRS1, PI3 kinase, and protein kinase C, as well as with the non-receptor tyrosine kinase pp60c-src, may also be associated with memory processing.

  9. Chitosan oligomers as potential and safe absorption enhancers for improving the pulmonary absorption of interferon-alpha in rats.

    PubMed

    Yamada, Keigo; Odomi, Masaaki; Okada, Naoki; Fujita, Takuya; Yamamoto, Akira

    2005-11-01

    Effects of chitosan oligomers on pulmonary absorption of interferon-alpha (IFN) were examined by means of an in vivo pulmonary absorption experiment. Chitosan oligomers used in this study were chitosan dimer, tetramer, hexamer, and water-soluble (WS) chitosan. A significant increase in serum IFN concentrations was observed after intratracheal administration of IFN with these oligomers. Of these chitosan oligomers, 0.5% w/v chitosan hexamer appeared to be more effective in enhancing the pulmonary absorption of IFN than other oligomers at the same concentration, and the AUC value of IFN with chitosan hexamer increased 2.6-fold as compared with the control. On the other hand, chitosan polymers, which have relatively high molecular weights (22-96 kDa), were not effective in enhancing the pulmonary absorption of IFN due to their low solubility in water. Additionally, the effect of different concentrations (0.1%-1% w/v) of chitosan hexamer on the pulmonary absorption of IFN was studied. Of these different concentrations of chitosan hexamers, the highest AUC value of IFN was obtained in the presence of 0.5% w/v chitosan hexamer. Furthermore, chitosan oligomers did not cause any membrane damage to the rat pulmonary tissues, as determined by leakage of protein and lactate dehydrogenase (LDH) in bronchoalveolar lavage (BAL) fluid. Therefore, these findings indicated that the use of chitosan oligomers would be a promising approach for improving of the pulmonary absorption of biologically active peptides including IFN.

  10. Direct observation of single amyloid-β(1-40) oligomers on live cells: binding and growth at physiological concentrations.

    PubMed

    Johnson, Robin D; Schauerte, Joseph A; Wisser, Kathleen C; Gafni, Ari; Steel, Duncan G

    2011-01-01

    Understanding how amyloid-β peptide interacts with living cells on a molecular level is critical to development of targeted treatments for Alzheimer's disease. Evidence that oligomeric Aβ interacts with neuronal cell membranes has been provided, but the mechanism by which membrane binding occurs and the exact stoichiometry of the neurotoxic aggregates remain elusive. Physiologically relevant experimentation is hindered by the high Aβ concentrations required for most biochemical analyses, the metastable nature of Aβ aggregates, and the complex variety of Aβ species present under physiological conditions. Here we use single molecule microscopy to overcome these challenges, presenting direct optical evidence that small Aβ(1-40) oligomers bind to living neuroblastoma cells at physiological Aβ concentrations. Single particle fluorescence intensity measurements indicate that cell-bound Aβ species range in size from monomers to hexamers and greater, with the majority of bound oligomers falling in the dimer-to-tetramer range. Furthermore, while low-molecular weight oligomeric species do form in solution, the membrane-bound oligomer size distribution is shifted towards larger aggregates, indicating either that bound Aβ oligomers can rapidly increase in size or that these oligomers cluster at specific sites on the membrane. Calcium indicator studies demonstrate that small oligomer binding at physiological concentrations induces only mild, sporadic calcium leakage. These findings support the hypothesis that small oligomers are the primary Aβ species that interact with neurons at physiological concentrations.

  11. Acute amnestic encephalopathy in amyloid-β oligomer-injected mice is due to their widespread diffusion in vivo.

    PubMed

    Epelbaum, Stéphane; Youssef, Ihsen; Lacor, Pascale N; Chaurand, Pierre; Duplus, Eric; Brugg, Bernard; Duyckaerts, Charles; Delatour, Benoît

    2015-06-01

    Amyloid-β (Aβ) oligomers are the suspected culprit as initiators of Alzheimer's disease (AD). However, their diffusion in the brain remains unknown. Here, we studied Aβ oligomers' dissemination and evaluated their in vivo toxicity. Wild-type mice were injected with 50 pmol of synthetic Aβ oligomers (of different size) in the hippocampus. Oligomers diffused largely in the brain as soon as 1 hour and up to 7 days after injection. A transient encephalopathy with memory impairment was induced by this unique injection. The immunoreactivity of the postsynaptic marker PSD95 was diffusely decreased. Similar results (both on memory and PSD95 immunoreactivity) were obtained with delipidated and high molecular weight oligomers (>50 kDa) but not with smaller assemblies. Tau hyperphosphorylation was observed in the oligomer-injected brains. Finally, fos immunostaining was increased in Aβ-derived diffusible ligands-injected mice, suggesting neuronal hyperactivity. Rapid and widespread diffusion of Aβ oligomers was demonstrated in vivo and associated with decreased synaptic markers and memory deficits which gives new insight to the pathogenicity of Aβ.

  12. Protective spin-labeled fluorenes maintain amyloid beta peptide in small oligomers and limit transitions in secondary structure

    PubMed Central

    Altman, Robin; Ly, Sonny; Hilt, Silvia; Petrlova, Jitka; Maezawa, Izumi; Kálai, Tamás; Hideg, Kálmán; Jin, Lee-Way; Laurence, Ted A.; Voss, John C.

    2015-01-01

    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. Furthermore, the circular dichroism (CD) spectrum of untreated Aβ shows a continuous, progressive change over a 24-hour period, while the spectrum of Aβ treated with SLF remains relatively constant following initial incubation. These findings suggest the conformation of Aβ within the oligomer provides a complementary determinant of Aβ toxicity in addition to oligomer growth and size. Although SLF does not produce a dominant state of secondary structure in Aβ, it does induce a net reduction in beta secondary content compared to untreated samples of Aβ. The FCS results, combined with electron paramagnetic resonance spectroscopy and CD spectroscopy, demonstrate SLFs can inhibit the growth of Aβ oligomers and disrupt existing oligomers, while retaining Aβ as a population of smaller, yet largely disordered oligomers. PMID:26374940

  13. Matrix-assisted laser desorption/ionization mass spectrometry of discrete mass poly(butylene glutarate) oligomers.

    PubMed

    Williams, John B; Chapman, Toby M; Hercules, David M

    2003-07-01

    The mass dependency of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) response has been studied using equimolar mixtures of synthetic discrete mass poly(butylene glutarate) (PBG) oligomers of known structure having degrees of polymerization of 8, 16, 32, and 64. Mass discrimination observed was attributed to choice of matrix and detector saturation caused by higher laser intensity and inclusion of matrix ions in the MALDI spectra. Optimization of sample preparation and instrumental parameters provided uniform response over the mass ranged spanned by these four oligomers. The oligomer mixture was shown to serve as a model of more complex polymer distributions in the mass range 780-6000 Da, and application of the discrete mass oligomers as internal and calibration standards was demonstrated. Inclusion of PBG discrete mass oligomers as an internal standard in a quasi-equimolar mixture with polydispersed poly(butylene adipate) (PBA) indicated that some diminution of response occurred during the analysis of this mixture of materials. Reasons for differences in the corrected molecular weight averages of the polydispersed PBA obtained from measurements using MALDI and GPC were studied using individual discrete mass oligomers as calibration standards for GPC. The data indicated that differences in hydrodynamic volumes of PBG oligomers and PEG standards at similar masses resulted in an overestimation by GPC of the molecular weight averages of the PBA distribution.

  14. 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.

  15. Antigenic implications of human immunodeficiency virus type 1 envelope quaternary structure: oligomer-specific and -sensitive monoclonal antibodies.

    PubMed Central

    Broder, C C; Earl, P L; Long, D; Abedon, S T; Moss, B; Doms, R W

    1994-01-01

    A majority of monoclonal antibodies (mAbs) raised against soluble oligomeric human immunodeficiency virus type 1 isolate IIIB (HIV-1IIIB) envelope (env) glycoprotein reacted with conformational epitopes within the gp120 or gp41 subunits. Of 35 mAbs directed against gp41, 21 preferentially reacted with oligomeric env. A subset of these mAbs reacted only with env oligomers (oligomer-specific mAbs). In contrast, only 1 of 27 mAbs directed against the gp120 subunit reacted more strongly with env oligomers than with monomers, and none were oligomer-specific. However, 50% of anti-gp120 mAbs preferentially recognized monomeric env, suggesting that some epitopes in gp120 are partially masked or altered by intersubunit contacts in the native env oligomer. Two mAbs to oligomer-dependent epitopes in gp41 neutralized HIV-1IIIB and HIV-1SF2, and binding of these mAbs to env was blocked by preincubation with HIV-1-positive human serum. Thus, immunization with soluble, oligomeric env elicits antibodies to conserved, conformational epitopes including a newly defined class of neutralizing antibodies that bind to oligomer-specific epitopes in gp41, and may also minimize the production of antibodies that preferentially react with monomeric env protein. Images PMID:7972127

  16. Effects of secreted oligomers of amyloid β-protein on hippocampal synaptic plasticity: a potent role for trimers

    PubMed Central

    Townsend, Matthew; Shankar, Ganesh M; Mehta, Tapan; Walsh, Dominic M; Selkoe, Dennis J

    2006-01-01

    The accumulation of amyloid β-protein (Aβ) in brain regions serving memory and cognition is a central pathogenic feature of Alzheimer's disease (AD). We have shown that small soluble oligomers of human Aβ that are naturally secreted by cultured cells inhibit hippocampal long-term potentiation (LTP) in vitro and in vivo and transiently impair the recall of a complex learned behaviour in rats. These results support the hypothesis that diffusible oligomers of Aβ initiate a synaptic dysfunction that may be an early event in AD. We now report detailed electrophysiological analyses that define conditions under which acute application of soluble Aβ inhibits hippocampal synaptic plasticity in wild-type mice. To ascertain which Aβ assemblies contribute to the impairment of LTP, we fractionated oligomers by size-exclusion chromatography and found that Aβ trimers fully inhibit LTP, whereas dimers and tetramers have an intermediate potency. Natural Aβ oligomers are sensitive to heat denaturation, primarily inhibit the induction phase of LTP, and cause a sustained impairment of LTP even after extensive washout. We observed no effects of Aβ oligomers on presynaptic vesicle release. LTP in juvenile mice is resistant to the effects of Aβ oligomers, as is brain-derived-neurotrophic-factor-induced LTP in adult hippocampus. We conclude that specific assemblies, particularly timers, of naturally secreted Aβ oligomers are potent and selective inhibitors of certain forms of hippocampal LTP. PMID:16469784

  17. Insulin Signaling and Heart Failure.

    PubMed

    Riehle, Christian; Abel, E Dale

    2016-04-01

    Heart failure is associated with generalized insulin resistance. Moreover, insulin-resistant states such as type 2 diabetes mellitus and obesity increases the risk of heart failure even after adjusting for traditional risk factors. Insulin resistance or type 2 diabetes mellitus alters the systemic and neurohumoral milieu, leading to changes in metabolism and signaling pathways in the heart that may contribute to myocardial dysfunction. In addition, changes in insulin signaling within cardiomyocytes develop in the failing heart. The changes range from activation of proximal insulin signaling pathways that may contribute to adverse left ventricular remodeling and mitochondrial dysfunction to repression of distal elements of insulin signaling pathways such as forkhead box O transcriptional signaling or glucose transport, which may also impair cardiac metabolism, structure, and function. This article will review the complexities of insulin signaling within the myocardium and ways in which these pathways are altered in heart failure or in conditions associated with generalized insulin resistance. The implications of these changes for therapeutic approaches to treating or preventing heart failure will be discussed.

  18. Insulin and the Burned Patient

    DTIC Science & Technology

    2007-01-01

    glucose utili- zation in muscle. J Clin Invest 1984; 74: 888–897 10. Watson RT, Pessin JE: Intracellular organi- zation of insulin signaling and GLUT4 ...regulated fusion of GLUT4 -containing vesicles with the plasma membrane. Mol Membr Biol 2001; 18:237–245 15. Nystrom FH, Quon MJ: Insulin signalling

  19. The load of amyloid-β oligomers is decreased in the cerebrospinal fluid of Alzheimer's disease patients.

    PubMed

    Sancesario, Giulia M; Cencioni, Maria T; Esposito, Zaira; Borsellino, Giovanna; Nuccetelli, Marzia; Martorana, Alessandro; Battistini, Luca; Sorge, Roberto; Spalletta, Gianfranco; Ferrazzoli, Davide; Bernardi, Giorgio; Bernardini, Sergio; Sancesario, Giuseppe

    2012-01-01

    Amyloid-β (Aβ) oligomers are heterogeneous and instable compounds of variable molecular weight. Flow cytometry and fluorescence resonance energy transfer (FRET)-based methods allow the simultaneous detection of Aβ oligomers with low and high molecular weight in their native form. We evaluated whether an estimate of different species of Aβ oligomers in the cerebrospinal fluid (CSF) with or without dilution with RIPA buffer could be more useful in the diagnosis of Alzheimer's disease (AD) than the measurement of Aβ42 monomers, total tau (t-tau), and phosphorylated tau (p-tau). Increased t-tau (p < 0.01) and p-tau (p < 0.01), and decreased Aβ42 (p < 0.01), were detected in the CSF of patients with AD (n = 46), compared to patients with other dementia (OD) (n = 35) or with other neurological disorders (OND) (n = 56). In native CSF (n = 137), the levels of Aβ oligomers were lower (p < 0.05) in AD than in OD and OND patients; in addition, the ratio Aβ oligomers/p-tau was lower in AD than in OD (p < 0.01) and OND (p < 0.05) patients, yielding a sensitivity of 75% and a specificity of 64%. However, in CSF diluted with RIPA (n = 30), Aβ oligomers appeared higher (p < 0.05) in AD than in OND patients, suggesting they become partially disaggregated and more easily detectable after RIPA. In conclusion, FRET analysis in native CSF is essential to correctly determine the composition of Aβ oligomers. In this experimental setting, the simultaneous estimate of low and high molecular weight Aβ oligomers is as useful as the other biomarkers in the diagnosis of AD. The low amount of Aβ oligomers detected in native CSF of AD may be inversely related to their levels in the brain, as occurs for Aβ monomers, representing a biomarker for the amyloid pathogenic cascade.

  20. Abnormal insulin levels and vertigo.

    PubMed

    Proctor, C A

    1981-10-01

    Fifty patients with unexplained vertigo (36) or lightheadedness (14) are evaluated, all of whom had abnormal ENGs and normal audiograms. Five hour insulin glucose tolerance tests were performance on all patients, with insulin levels being obtained fasting and at one-half, one, two, and three hours. The results of this investigation were remarkable. Borderline or abnormal insulin levels were discovered in 82% of patients; 90% were found to have either an abnormal glucose tolerance test or at least borderline insulin levels. The response to treatment in these dizzy patients was also startling, with appropriate low carbohydrate diets improving the patient's symptoms in 90% of cases. It is, therefore, apparent that the earliest identification of carbohydrate imbalance with an insulin glucose tolerance test is extremely important in the work-up of the dizzy patients.

  1. 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.

  2. Purified high molecular weight synthetic Aβ(1-42) and biological Aβ oligomers are equipotent in rapidly inducing MTT formazan exocytosis.

    PubMed

    Weidner, Adam M; Housley, Molly; Murphy, M Paul; Levine, Harry

    2011-06-15

    Synthetic soluble Aβ oligomers are often used as a surrogate for biologic material in a number of model systems. We compared the activity of Aβ oligomers (synthetic and cell culture media derived) on the human SH-SY5Y neuroblastoma and C2C12 mouse myoblast cell lines in a novel, modified MTT assay. Separating oligomers from monomeric peptide by size exclusion chromatography produced effects at peptide concentrations approaching physiologic levels (10-100 nM). Purified oligomers, but not monomers or fibrils, elicited an increase of a detergent-insoluble form of MTT formazan within 2h as opposed to a control toxin (H(2)O(2)). This effect was comparable for biological and synthetic peptide in both cell types. Monomeric Aβ attenuated the effect of soluble oligomers. This study suggests that the activities of biological and synthetic oligomers are indistinguishable during early stages of Aβ oligomer-cell interaction.

  3. Design and solid phase synthesis of new DOTA conjugated (+)-biotin dimers planned to develop molecular weight-tuned avidin oligomers.

    PubMed

    Pratesi, Alessandro; Ginanneschi, Mauro; Melani, Fabrizio; Chinol, Marco; Carollo, Angela; Paganelli, Giovanni; Lumini, Marco; Bartoli, Mattia; Frediani, Marco; Rosi, Luca; Petrucci, Giorgio; Messori, Luigi; Papini, Anna Maria

    2015-04-07

    Chemical modifications of the biotin carrier in pretargeted avidin–biotin radionuclide therapy may be of paramount importance for tuning the amount of the radioactivity delivered to cancer cells by labelled biotins. We report here the synthesis of a collection of new synthetic DOTA-constructs bearing two (+)-biotin molecules (bis-biotins), designed for the creation of multimeric Av units (tetramers) bonded to the antibody. All the syntheses were carried out following the solid phase strategy and growing the molecules on a Rink Amide resin. The biotin heads are connected through spacers containing PEG or non-PEG residues. Molecular modelling calculations suggested that the Av cross-linking ability of the bis-biotins depends mainly on the spacers length, with the best results being expected for arms affording distances in the range of 10–25 Å between the biotin carboxylate atoms, in the fully extended conformation. SEC-HPLC MALLS analysis of the products of our Av/bis-biotin reaction mixtures have confirmed this hypothesis. The bis-biotin 16, where the non-PEG linker ensured a distance of 26.7 Å between the biotin moieties, gave about 50% of Av oligomers while the shorter analogue 18 (19.5 Å) afforded 100% of an Av polymer containing about 21 protein units. Remarkably, the solubility of both the bis-biotins, i.e.16 and 18, in aqueous solutions was good and they showed excellent stability against the action of peptidases.

  4. Tumour destruction and proliferation kinetics following periodic, low power light, haematoporphyrin oligomers mediated photodynamic therapy in the mouse tongue.

    PubMed

    Pe, M B; Ikeda, H; Inokuchi, T

    1994-05-01

    Photodynamic therapy (PDT) is an experimental modality in the treatment of cancer. It involves photochemical reactions that require the interaction of a photosensitising drug, light and oxygen. The development of an efficient protocol based on assuring oxygen availability through modulation of the incident light power density and its mode of delivery was addressed in this study. An estimated energy dose of 180 J/cm2 of 630 nm light from pulsed Nd:YAG dye laser was delivered 24 h after injection of 10 mg/kg haematoporphyrin oligomers in C3H/HeNCrj mice bearing the transplantable squamous cell carcinoma NR-S1, by either of these light regimens: (1) 5 mJ/cm2/pulse for 30 min, 1 h dark interval, followed by another 30 min exposure to the same power (low power, periodic light regimen) or (2) 15 mJ/cm2/pulse for 20 min (high power, continuous light regimen). Results showed a higher mean percentage area of tumour destruction with the low power, periodic light regimen at 54.34% in contrast to 12.44% of the high power, continuous light regimen 2 days after PDT. Furthermore, the mean bromodeoxyuridine labelling indices of the remaining viable-appearing cancer cells were 27.90 and 42.41, respectively, indicating a smaller tumour growth fraction with the former regimen. These results suggest that use of low power, periodically delivered light increases the antitumour efficacy of PDT.

  5. A Simplified and Efficient Process for Insulin Production in Pichia pastoris

    PubMed Central

    Polez, Sulena; Origi, Domenico; Zahariev, Sotir; Guarnaccia, Corrado; Tisminetzky, Sergio G.; Skoko, Nataša

    2016-01-01

    A significant barrier to insulin is affordability. In this manuscript we describe improvements to key steps in the insulin production process in Pichia pastoris that reduce cost and time. The strategy for recovery and processing of human insulin precursor has been streamlined to two steps from bioreactor to the transpeptidation reaction. In the first step the insulin precursor secreted during the methanol induction phase is recovered directly from the culture broth using Tangential Flow Filtration with a Prostak™ module eliminating the laborious and time-consuming multi-step clarification, including centrifugation. In the second step the protein is applied at very high loadings on a cation exchange resin and eluted in a mixture of water and ethanol to obtain a concentrated insulin precursor, suitable for use directly in the transpeptidation reaction. Overall the yield from insulin precursor to human insulin was 51% and consisted of three purification chromatography steps. In addition we describe a method for recovery of the excess of H-Thr(tBu)-OtBu from the transpeptidation reaction mixture, one of the more costly reagents in the process, along with its successful reuse. PMID:27907132

  6. Single-Nucleotide Polymorphism on Exon 17 of Insulin Receptor Gene Influences Insulin Resistance in PCOS: A Pilot Study on North Indian Women.

    PubMed

    Gangopadhyay, Sukanya; Agrawal, Nitin; Batra, Aruna; Kabi, Bhaskar Charan; Gupta, Akash

    2016-04-01

    Polycystic ovarian syndrome (PCOS), a major cause of infertility, is also strongly associated with insulin resistance. Defects in insulin receptor signaling are considered as one of the major molecular pathogeneses for insulin resistance. To investigate the possible mechanism of this signaling defect at genetic level, single-nucleotide polymorphism (SNP) [His 1085 C/T] at the exon 17 of insulin receptor gene (INSR) was studied in this pilot study. Polymerase chain reaction was performed on leucocytic DNA of women diagnosed with PCOS, selected from the outpatient department of Safdarjung Hospital, New Delhi, using suitable primer to amplify a region on INSR. An equal number of age-matched healthy women were selected as controls. SNP analysis was performed with restriction enzyme length polymorphism technique using Pm II enzyme. Serum insulin level was measured by ELISA kit and HOMA-IR was calculated mathematically. A higher frequency of the CC genotype was observed in PCOS women than in controls. Also, HOMA-IR, a tool for estimating insulin resistance, was significantly high in PCOS women with the CC genotype. C1008T SNP at exon 17 of INSR is associated with insulin resistance in Indian women with PCOS. Presence of CC genotype (C1085T) could be developed as a marker for insulin resistance and metabolic complications in PCOS women.

  7. 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.

  8. Soluble oligomers of amyloid-β cause changes in redox state, DNA methylation, and gene transcription by inhibiting EAAT3 mediated cysteine uptake.

    PubMed

    Hodgson, Nathaniel; Trivedi, Malav; Muratore, Christina; Li, Shaomin; Deth, Richard

    2013-01-01

    Oxidative stress, hyperhomocysteinemia, altered DNA methylation, and insulin resistance in the brain are associated with Alzheimer's disease (AD), but the role of amyloid-β (Aβ) in these events remains unclear. Intracellular cysteine is rate-limiting for synthesis of the antioxidant glutathione (GSH), and factors regulating cysteine uptake exert a powerful influence over cellular redox status, especially in mature neurons where cysteine synthesis via transsulfuration of homocysteine (HCY) is restricted. We investigated the effect of soluble Aβ oligomers (oAβ) on basal and insulin-like growth factor-1 (IGF-1)-induced cysteine uptake mediated by the excitatory amino acid transporter 3 (EAAT3) in cultured human neuronal cells. We also examined the effect of oAβ on intracellular thiol metabolite levels, DNA methylation, and the transcription status of redox and methylation-associated genes. oAβ inhibited EAAT3-mediated cysteine uptake, causing a decrease in intracellular cysteine and GSH levels. The ratio of the methyl donor S-adenosylmethionine to the methylation inhibitor S-adenosylhomocysteine was decreased, in association with an increase in HCY and a global decrease in DNA methylation, indicative of decreased activity of the redox-sensitive enzyme methionine synthase. These metabolic effects of oAβ coincided with changes in the expression of redox and methylation pathway genes. The ability of oAβ to modulate gene expression via their redox and methylation-dependent epigenetic effects may contribute to the pathology of AD and recognition of this mechanism may lead to novel treatment approaches. We describe a role of IGF-1 signaling in regulating redox and methylation homeostasis, and propose this to be a pathogenic target of oAβ.

  9. Cell factories for insulin production.

    PubMed

    Baeshen, Nabih A; Baeshen, Mohammed N; Sheikh, Abdullah; Bora, Roop S; Ahmed, Mohamed Morsi M; Ramadan, Hassan A I; Saini, Kulvinder Singh; Redwan, Elrashdy M

    2014-10-02

    The rapid increase in the number of diabetic patients globally and exploration of alternate insulin delivery methods such as inhalation or oral route that rely on higher doses, is bound to escalate the demand for recombinant insulin in near future. Current manufacturing technologies would be unable to meet the growing demand of affordable insulin due to limitation in production capacity and high production cost. Manufacturing of therapeutic recombinant proteins require an appropriate host organism with efficient machinery for posttranslational modifications and protein refolding. Recombinant human insulin has been produced predominantly using E. coli and Saccharomyces cerevisiae for therapeutic use in human. We would focus in this review, on various approaches that can be exploited to increase the production of a biologically active insulin and its analogues in E. coli and yeast. Transgenic plants are also very attractive expression system, which can be exploited to produce insulin in large quantities for therapeutic use in human. Plant-based expression system hold tremendous potential for high-capacity production of insulin in very cost-effective manner. Very high level of expression of biologically active proinsulin in seeds or leaves with long-term stability, offers a low-cost technology for both injectable as well as oral delivery of proinsulin.

  10. 1,2,3-Triazolium-Based Peptoid Oligomers.

    PubMed

    Aliouat, Hafida; Caumes, Cécile; Roy, Olivier; Zouikri, Mohamed; Taillefumier, Claude; Faure, Sophie

    2017-02-22

    The cis-directing effect of the 1,2,3-triazolium-type side chain was studied on dimeric peptoid models with various patterns: αα, αβ, βα and ββ. Low influences of the sequence and of the solvent were observed, the cis conformation of the amide carrying the triazolium ranging from 83 to 94% in proportion. The synthesis of peptoid homooligomers with four or eight pendant 1,2,3-triazolium side chains is described. α-, β- and α,β-peptoids carrying propargyl groups were subjected to CuAAC reaction using alkyl azides, and the resulting triazoles were quaternized providing well-defined multitriazolium platforms. The influence of the counteranion (PF6(-), BF4(-) or I(-)) on the conformation was also studied.

  11. Conformation-specific antibodies to target amyloid β oligomers and their application to immunotherapy for Alzheimer's disease.

    PubMed

    Murakami, Kazuma

    2014-01-01

    Amyloid β-protein (Aβ) oligomers, intermediates of Aβ aggregation, cause cognitive impairment and synaptotoxicity in the pathogenesis of Alzheimer's disease (AD). Immunotherapy using anti-Aβ antibody is one of the most promising approaches for AD treatment. However, most clinical trials using conventional sequence-specific antibodies have proceeded with difficulty. This is probably due to the unintended removal of the non-pathological monomer and fibrils of Aβ as well as the pathological oligomers by these antibodies that recognize Aβ sequence, which is not involved in synaptotoxicity. Several efforts have been made recently to develop conformation-specific antibodies that target the tertiary structure of Aβ oligomers. Here, we review the recent findings of Aβ oligomers and anti-Aβ antibodies including our own, and discuss their potential as therapeutic and diagnostic tools.

  12. Saccharide recognition-induced transformation of pyridine-pyridone alternate oligomers from self-dimer to helical complex.

    PubMed

    Abe, Hajime; Machiguchi, Hiroshi; Matsumoto, Shinya; Inouye, Masahiko

    2008-06-20

    Co-oligomers involving (1H)-4-pyridone and 4-alkoxypyridine rings were studied, and it was found that their supramolecular transformation was caused by saccharide recognition. In the co-oligomers, pyridone and pyridine rings are alternately linked at their 2,6-position with an acetylene bond. The pyridine rings behave as a hydrogen bonding acceptor, and the pyridone rings and tautomerized 4-pyridinol work as a donor. Pyridine-pyridone-pyridine 3-mer was found to self-dimerize on the basis of vapor pressure osmometry in CHCl(3), and the association constant was obtained as 2.3 x 10(3) M(-1) by (1)H NMR titration. Longer 5-, 7-, 9-, and 11-mer oligomers showed considerable broadening and anisotropy in the (1)H NMR spectra due to self-association. These longer oligomers recognized octyl beta-D-glucopyranoside and changed their form into a chiral helical complex, showing characteristic circular dichroism.

  13. Insulin Receptor Signaling in Normal and Insulin-Resistant States

    PubMed Central

    Boucher, Jérémie; Kleinridders, André; Kahn, C. Ronald

    2014-01-01

    In the wake of the worldwide increase in type-2 diabetes, a major focus of research is understanding the signaling pathways impacting this disease. Insulin signaling regulates glucose, lipid, and energy homeostasis, predominantly via action on liver, skeletal muscle, and adipose tissue. Precise modulation of this pathway is vital for adaption as the individual moves from the fed to the fasted state. The positive and negative modulators acting on different steps of the signaling pathway, as well as the diversity of protein isoform interaction, ensure a proper and coordinated biological response to insulin in different tissues. Whereas genetic mutations are causes of rare and severe insulin resistance, obesity can lead to insulin resistance through a variety of mechanisms. Understanding these pathways is essential for development of new drugs to treat diabetes, metabolic syndrome, and their complications. PMID:24384568

  14. Insulin and IGF-1 signalling: longevity, protein homoeostasis and Alzheimer's disease.

    PubMed

    O'Neill, Cora; Kiely, Aoife P; Coakley, Meghan F; Manning, Sean; Long-Smith, Caitriona M

    2012-08-01

    The quality control of protein homoeostasis deteriorates with aging, causing the accumulation of misfolded proteins and neurodegeneration. Thus, in AD (Alzheimer's disease), soluble oligomers, protofibrils and fibrils of the Aβ (amyloid β-peptide) and tau protein accumulate in specific brain regions. This is associated with the progressive destruction of synaptic circuits controlling memory and higher mental function. The primary signalling mechanisms that (i) become defective in AD to alter the normal proteostasis of Aβ and tau, and (ii) initiate a pathophysiological response to cause cognitive decline, are unclear. The IIS [insulin/IGF-1 (insulin-like growth factor 1)-like signalling] pathway is mechanistically linked to longevity, protein homoeostasis, learning and memory, and is emerging to be central to both (i) and (ii). This pathway is aberrantly overactivated in AD brain at the level of increased activation of the serine/threonine kinase Akt and the phosphorylation of its downstream targets, including mTOR (mammalian target of rapamycin). Feedback inhibition of normal insulin/IGF activation of the pathway also occurs in AD due to inactivation of IRS-1 (insulin receptor substrate 1) and decreased IRS-1/2 levels. Pathogenic forms of Aβ may induce aberrant sustained activation of the PI3K (phosphoinositide 3-kinase)/Akt signal in AD, also causing non-responsive insulin and IGF-1 receptor, and altered tau phosphorylation, conformation and function. Reducing IIS activity in animal models by decreasing IGF-1R levels or inhibiting mTOR activity alters Aβ and tau protein homoeostasis towards less toxic protein conformations, improves cognitive function and extends healthy lifespan. Thus normalizing IIS dysfunction may be therapeutically relevant in abrogating Aβ and tau proteotoxicity, synaptic dysfunction and cognitive decline in AD.

  15. New ways of insulin delivery.

    PubMed

    Heinemann, L

    2010-02-01

    When Exubera (EXU), the first inhaled insulin formulation to make it through the clinical development process, was introduced to the market some years ago it was hoped that this would be the first in a series of novel insulin formulations applied by this route. In addition, it was hoped that inhaled insulin would pave the way for other alternative routes of insulin administration (ARIA), i.e. oral insulin, nasal insulin or transdermal insulin to mention only some of the different attempts that have been studied in the last 90 years. The failure of EXU, i.e. its withdrawal from the market due to insufficient market success, was followed by the cessation of nearly all other attempts to develop inhaled insulin formulations. Currently there is only one company (MannKind) which moves sturdily ahead with their Technosphere insulin. This company has submitted an NDA for their product recently and hopes to bring it to the market by the end of 2010 or early 2011. Even if the product is able to pass the approval hurdles in the USA and Europe, this does not guarantee that it will become a market success. Many diabetologists were sceptical about the need/advantages of inhaled insulin/EXU from the start and the introduction of this product has raised even more scepticism. Reports about 'side effects' (development of lung cancer in patients treated with EXU) of inhaled insulin are also not helpful, even if the causality of the appearance of cancer with this type of insulin therapy is not proven. One of the very negative consequences of stopping EXU are the huge financial losses to Pfizer. The managers in charge in other pharmaceutical companies and also most venture capitalists are reluctant to invest in ARIA nowadays. This in turn means that many of the small companies that try to develop new forms of insulin administration have issues when they try to find a big brother and/or sufficient financial support. Clearly the economic crisis has further aggravated this issue. One can

  16. 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

    2016-08-08

    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 demonstrated by building 14 unique trimers and 4 hexamers from 6 diverse building blocks. We then adapted this method to the parallel synthesis of hundreds of materials in 96-well plates. This strategy provides a platform for the screening of libraries of modified biomolecules.

  17. 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.

  18. 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.

  19. Liquid Crystalline Thermosets from Ester, Ester-imide, and Ester-amide Oligomers

    NASA Technical Reports Server (NTRS)

    Dingemans, Theodorus J. (Inventor); Weiser, Erik S. (Inventor); St. Clair, Terry L. (Inventor)

    2009-01-01

    Main chain thermotropic liquid crystal esters, ester-imides, and ester-amides were prepared from AA, BB, and AB type monomeric materials and end-capped with phenylacetylene, phenylmaleimide, or nadimide reactive end-groups. 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 crystaloligomers have broad liquid crystalline melting ranges and exhibit high melt stability and very low melt viscosities at accessible temperatures. The end-capped liquid crystal oli-gomers are stable forup to an hour in the melt phase. They are highly processable by a variety of melt process shape forming and blending techniques. Once processed and shaped, the end-capped liquid crystal oigomers were heated to further polymerize and form liquid crystalline thermosets (LCT). The fully cured products are rubbers above their glass transition temperatures.

  20. Similarities and differences in the influence of polycations and oligomers on DNA conformation and packaging.

    PubMed

    Kasyanenko, Nina; Dribinsky, Boris

    2016-05-01

    A comparison of DNA conformational changes in a solution containing the poly-l-lysine with the number of monomers z=3, 5, 17, 20, 270, 325 and polyamines (spermine and spermidine) was carried out in 1M and 5mM NaCl solutions. It was shown that despite the identical results of DNA condensation induced by compounds, their influence on the DNA conformation prior to packaging depends on whether they belong to a long polycations or short oligomers. DNA secondary and tertiary structures were examined using Circular Dichroism, UV-vis Spectrophotometry, Dynamic Light Scattering, Low Gradient Viscometry, Flow Birefringence, and AFM. The phase diagrams for systems of DNA-polycations, DNA-oligomers, DNA-polyamines were drawn.

  1. Liquid Crystal Ordering and Isotropic Gelation in Solutions of Four-Base-Long DNA Oligomers.

    PubMed

    Fraccia, Tommaso P; Smith, Gregory P; Bethge, Lucas; Zanchetta, Giuliano; Nava, Giovanni; Klussmann, Sven; Clark, Noel A; Bellini, Tommaso

    2016-09-27

    Liquid crystal ordering is reported in aqueous solutions of the oligomer 5'-ATTAp-3' and of the oligomer 5'-GCCGp-3'. In both systems, we quantitatively interpret ordering as stemming from the chaining of molecules via a "running-bond" type of pairing, a self-assembly process distinct from the duplex aggregation previously reported for longer oligonucleotides. While concentrated solutions of 5'-ATTAp-3' show only a columnar liquid crystal phase, solutions of 5'-GCCGp-3' display a rich phase diagram, featuring a chiral nematic phase analogous to those observed in solutions of longer oligonucleotides and two unconventional phases, a columnar crystal and, at high concentration, an isotropic amorphous gel. The appearance of these phases, which can be interpreted on the basis of features of 5'-GCCGp-3'molecular structure, suggests distinctive assembly motifs specific to ultrashort oligonucleotides.

  2. Self-assembly of human MxA GTPase into highly ordered dynamin-like oligomers.

    PubMed

    Kochs, Georg; Haener, Markus; Aebi, Ueli; Haller, Otto

    2002-04-19

    Human MxA protein is a member of the interferon-induced Mx protein family and an important component of the innate host defense against RNA viruses. The Mx family belongs to a superfamily of large GTPases that also includes the dynamins and the interferon-regulated guanylate-binding proteins. A common feature of these large GTPases is their ability to form high molecular weight oligomers. Here we determined the capacity of MxA to self-assemble into homo-oligomers in vitro. We show that recombinant MxA protein assembles into long filamentous structures with a diameter of about 20 nm at physiological salt concentration as demonstrated by sedimentation assays and electron microscopy. In the presence of guanosine nucleotides the filaments rearranged into rings and more compact helical arrays. Our data indicate that binding and hydrolysis of GTP induce conformational changes in MxA that may be essential for viral target recognition and antiviral activity.

  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. Considerable Enhancement of Emission Yields of [Au(CN)2(-)] Oligomers in Aqueous Solutions by Coexisting Cations.

    PubMed

    Wakabayashi, Ryo; Maeba, Junichi; Nozaki, Koichi; Iwamura, Munetaka

    2016-08-01

    The photophysical properties of [Au(CN)2(-)] oligomers in aqueous solutions were investigated as functions of coexisting cations as well as the viscosity and temperature of solutions. A solution of [Au(CN)2(-)] in the concentration range of 0.03-0.2 mol/dm(3) exhibited emission peaks at 460-480 nm because of the presence of oligomers larger than trimers. Although the emission yields (ϕem) of K[Au(CN)2] solutions were <1%, it considerably increased to 43% when 1.0 mol/dm(3) tetraethylammonium chloride (Et4NCl) was added. The lifetimes of the main emission bands were also significantly varied with additional salts, e.g., KCl, 15 ns; Et4NCl, 520 ns. The time-resolved emission measurements of [Au(CN)2(-)] in a water/glycerol mixture indicated that the lifetimes were almost directly proportional to the inverse of the viscosity of the solution. On the other hand, the intrinsic lifetimes of dimers and trimers with weak emission in shorter wavelength regions were very short and independent of the viscosity of the solutions and coexisting cations (dimer, ∼25 ps; trimer, ∼2 ns). These results indicated that the deactivation of the excited-state [Au(CN)2(-)]n oligomers (n ≥ 4) was dominated by the dissociation of the oligomers to a shorter species (dimer or trimer). The hydrophobic interactions between tetraalkylammonium cations and CN ligands remarkably stabilized the larger oligomers and suppressed the dissociation of the excited-state oligomers, which enhanced the emission yield of the oligomers. This work provides a new method of "exciplex tuning" by changing the environment of excited-state [Au(CN)2(-)]n oligomers.

  5. Tau Oligomers Associate with Inflammation in the Brain and Retina of Tauopathy Mice and in Neurodegenerative Diseases

    PubMed Central

    Nilson, Ashley N.; English, Kelsey C.; Gerson, Julia E.; Barton Whittle, T.; Nicolas Crain, C.; Xue, Judy; Sengupta, Urmi; Castillo-Carranza, Diana L.; Zhang, Wenbo; Gupta, Praveena; Kayed, Rakez

    2016-01-01

    It is well-established that inflammation plays an important role in Alzheimer’s disease (AD) and frontotemporal lobar dementia (FTLD). Inflammation and synapse loss occur in disease prior to the formation of larger aggregates, but the contribution of tau to inflammation has not yet been thoroughly investigated. Tau pathologically aggregates to form large fibrillar structures known as tangles. However, evidence suggests that smaller soluble aggregates, called oligomers, are the most toxic species and form prior to tangles. Furthermore, tau oligomers can spread to neighboring cells and between anatomically connected brain regions. In addition, recent evidence suggests that inspecting the retina may be a window to brain pathology. We hypothesized that there is a relationship between tau oligomers and inflammation, which are hallmarks of early disease. We conducted immunofluorescence and biochemical analyses on tauopathy mice, FTLD, and AD subjects. We showed that oligomers co-localize with astrocytes, microglia, and HMGB1, a pro-inflammatory cytokine. Additionally, we show that tau oligomers are present in the retina and are associated with inflammatory cells suggesting that the retina may be a valid non-invasive biomarker for brain pathology. These results suggest that there may be a toxic relationship between tau oligomers and inflammation. Therefore, the ability of tau oligomers to spread may initiate a feed-forward cycle in which tau oligomers induce inflammation, leading to neuronal damage, and thus more inflammation. Further mechanistic studies are warranted in order to understand this relationship, which may have critical implications for improving the treatment of tauopathies. PMID:27716675

  6. Characterisation of proanthocyanidins from black soybeans: isolation and characterisation of proanthocyanidin oligomers from black soybean seed coats.

    PubMed

    Ito, Chiaki; Oki, Tomoyuki; Yoshida, Tadashi; Nanba, Fumio; Yamada, Katsushige; Toda, Toshiya

    2013-12-01

    Proanthocyanidin oligomers (dimers to tetramers) were isolated from black soybean seed coats, using Sephadex LH-20 column chromatography and reversed-phase preparative HPLC. The isolated oligomers consisted of only (-)-epicatechin units, which were linked through either 4β→8 or 4β→6 (B-type) bonds. Procyanidin B2, procyanidin C1, and cinnamtannin A2 were identified as the main compounds of the proanthocyanidin dimers, trimers, and tetramers, respectively.

  7. A quantification method for heat-decomposable methylglyoxal oligomers and its application on 1,3,5-trimethylbenzene SOA

    NASA Astrophysics Data System (ADS)

    Rodigast, Maria; Mutzel, Anke; Herrmann, Hartmut

    2017-03-01

    Methylglyoxal forms oligomeric compounds in the atmospheric aqueous particle phase, which could establish a significant contribution to the formation of aqueous secondary organic aerosol (aqSOA). Thus far, no suitable method for the quantification of methylglyoxal oligomers is available despite the great effort spent for structure elucidation. In the present study a simplified method was developed to quantify heat-decomposable methylglyoxal oligomers as a sum parameter. The method is based on the thermal decomposition of oligomers into methylglyoxal monomers. Formed methylglyoxal monomers were detected using PFBHA (o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride) derivatisation and gas chromatography-mass spectrometry (GC/MS) analysis. The method development was focused on the heating time (varied between 15 and 48 h), pH during the heating process (pH = 1-7), and heating temperature (50, 100 °C). The optimised values of these method parameters are presented. The developed method was applied to quantify heat-decomposable methylglyoxal oligomers formed during the OH-radical oxidation of 1,3,5-trimethylbenzene (TMB) in the Leipzig aerosol chamber (LEipziger AerosolKammer, LEAK). Oligomer formation was investigated as a function of seed particle acidity and relative humidity. A fraction of heat-decomposable methylglyoxal oligomers of up to 8 % in the produced organic particle mass was found, highlighting the importance of those oligomers formed solely by methylglyoxal for SOA formation. Overall, the present study provides a new and suitable method for quantification of heat-decomposable methylglyoxal oligomers in the aqueous particle phase.

  8. [Cerebral proteolysis of amiloid-b peptide: relevance of insulin-degrading enzyme in Alzheimer's disease].

    PubMed

    Leal, María Celeste; Fernandez Gamba, Agata; Morelli, Laura; Castaño, Eduardo M

    2009-01-01

    The global increase in life expectancy turns Alzheimer's disease (AD) into a growing problem. One of the distinctive features of AD is the excessive accumulation of amyloid-b (Ab) peptide in the brain. In recent years, a concept that has gained strength is that degradation of Ab by proteases in situ is an important mechanism that prevents cerebral peptide accumulation. Biochemical and genetic data have shown that insulin-degrading enzyme (IDE) participates in Ab and insulin homeostasis. IDE expression and activity are significantly decreased in AD brains compared to age-matched controls. Also, IDE is deposited with Ab in senile plaques and blood vessels, indicating a gross conformational change as a consequence of diverse post-translational mechanisms. These alterations in IDE distribution and activity may result in insufficient degradation of Ab and insulin, promoting the formation of Ab oligomers and hormone resistance. Both processes might play a fundamental part in neurodegeneration. The study of the clearance mechanisms of cerebral Ab will not only aid in the understanding AD pathogenesis but will also allow a better interpretation of ongoing clinical trials and the development of new therapeutic strategies.

  9. Energetic contributions of residues to the formation of early amyloid-β oligomers.

    PubMed

    Pouplana, R; Campanera, J M

    2015-01-28

    Low-weight amyloid-β (Aβ) oligomers formed at early stages of oligomerization rather than fibril assemblies seem to be the toxic components that drive neurodegeneration in Alzheimer's disease. Unfortunately, detailed knowledge of the structure of these early oligomers at the residue level is not yet available. In this study, we performed all-atom explicit solvent molecular dynamics simulations to examine the oligomerization process of Aβ10-35 monomers when forming dimers, trimers, tetramers and octamers, with four independent simulations of a total simulated time of 3 μs for each oligomer system. The decomposition of the stability free energy by MM-GBSA methodology allowed us to unravel the network of energetic interactions that stabilize such oligomers. The contribution of the intermonomeric van der Waals term is the most significant energy feature of the oligomerization process, consistent with the so-called hydrophobic effect. Furthermore, the decomposition of the stability free energy into residues and residue-pairwise terms revealed that it is mainly apolar interactions between the three specific hydrophobic fragments 31-35 (C-terminal region), 17-20 (central hydrophobic core) and 12-14 (N-terminal region) that are responsible for such a favourable effect. The conformation in which the hydrophobic cthr-chc interaction is oriented perpendicularly is particularly important. We propose three other model substructures that favour the oligomerization process and can thus be considered as molecular targets for future inhibitors. Understanding Aβ oligomerization at the residue level could lead to more efficient design of inhibitors of this process.

  10. Yeast prion-protein, sup35, fibril formation proceeds by addition and substraction of oligomers.

    PubMed

    Narayanan, Saravanakumar; Walter, Stefan; Reif, Bernd

    2006-05-01

    In analogy to human prions, a domain of the translation-termination protein in Saccharomyces cerevisiae, Sup35, can switch its conformation from a soluble functional state, [psi-], to a conformation, [PSI+], that facilitates aggregation and impairs its native function. Overexpression of the molecular chaperone Hsp104 abolishes the [PSI+] phenotype and restores the normal function of Sup35. We have recently shown that Hsp104 interacts preferably with low oligomeric species of a Sup35 derived peptide, Sup35[5-26]; however, due to possible exchange between different oligomeric states, it was not possible to obtain information on the distribution and stability of the oligomeric state. We show here, that low-molecular-weight oligomers (Sup35[5-26])n (n approximately = 4-6) are indeed important for the fibril formation and disassembly process. We find that Hsp104 is able to disaggregate Sup35[5-26] fibrils by substraction of hexameric to decameric Sup35[5-26] oligomers. This disaggregation effect does not require assistance from other chaperones and is independent of ATP at high Hsp104 concentrations. Furthermore, we demonstrate that critical oligomers have a preference for alpha-helical conformations. The conformational reorganization into beta-sheet structures seems to occur only upon incorporation of these oligomers into fibrillar structures. The results are demonstrated by using an equilibrium dialysis experiment that employed different molecular-weight cut-off membranes. A combination of thioflavin-T (ThT) fluorescence and UV measurements allowed the quantification of fibril formation and the amount of peptide diffusing out of the dialysis bag. CD and NMR spectroscopy data were combined to obtain structural information.

  11. Probing and trapping a sensitive conformation: amyloid-β fibrils, oligomers, and dimers.

    PubMed

    Fawver, Janelle N; Duong, Karen T; Wise-Scira, Olivia; Petrofes Chapa, Rachel; Schall, Hayley E; Coskuner, Orkid; Zhu, Xiongwei; Colom, Luis V; Murray, Ian V J

    2012-01-01

    Alzheimer's disease (AD) is a devastating neurodegenerative disease with pathological misfolding of amyloid-β protein (Aβ). The recent interest in Aβ misfolding intermediates necessitates development of novel detection methods and ability to trap these intermediates. We speculated that two regions of Aβ may allow for detection of specific Aβ species: the N-terminal and 22-35, both likely important in oligomer interaction and formation. We determined via epitomics, proteomic assays, and electron microscopy that the Aβ(42) species (wild type, ΔE22, and MetOx) predominantly formed fibrils, oligomers, or dimers, respectively. The 2H4 antibody to the N-terminal of Aβ, in the presence of 2% SDS, primarily detected fibrils, and an antibody to the 22-35 region detected low molecular weight Aβ species. Simulated molecular modeling provided insight into these SDS-induced structural changes. We next determined if these methods could be used to screen anti-Aβ drugs as well as identify compounds that trap Aβ in various conformations. Immunoblot assays determined that taurine, homotaurine (Tramiprosate), myoinositol, methylene blue, and curcumin did not prevent Aβ aggregation. However, calmidazolium chloride trapped Aβ at oligomers, and berberine reduced oligomer formation. Finally, pretreatment of AD brain tissues with SDS enhanced 2H4 antibody immunostaining of fibrillar Aβ. Thus we identified and characterized Aβs that adopt specific predominant conformations (modified Aβ or via interactions with compounds), developed a novel assay for aggregated Aβ, and applied it to drug screening and immunohistochemistry. In summary, our novel approach facilitates drug screening, increases the probability of success of antibody therapeutics, and improves antibody-based detection and identification of different conformations of Aβ.

  12. 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

  13. A model for non-obligate oligomer formation in protein aggregration

    PubMed Central

    Healy, Eamonn F.

    2015-01-01

    Using solvent-exposed intramolecular backbone hydrogen bonds as physico-chemical descriptors for protein packing, a role for transient, non-obligate oligomers in the formation of aberrant protein aggregates is presented. Oligomeric models of the both wild type (wt) and select mutant variants of superoxide dismutase (SOD1) are proposed to provide a structural basis for investigating the etiology of Amyotrophic Lateral Sclerosis (ALS). PMID:26282203

  14. Conformational control in a bipyridine linked π-conjugated oligomer: cation mediated helix unfolding and refolding.

    PubMed

    Divya, Kizhumuri P; Sreejith, Sivaramapanicker; Suresh, Cherumuttathu H; Ajayaghosh, Ayyappanpillai

    2010-11-28

    A chiral π-conjugated oligomer having alternate bipyridine and carbazole moieties connected through acetylinic bonds undergoes helical folding in chloroform-acetonitrile (40/60, v/v) as evident by fluorescence and circular dichroism changes. In the presence of transition metal cations such as Zn(2+) defolding of the helical conformation occurs. Upon decomplexation of the cation with EDTA, the helical conformation is regained.

  15. Quaternized chitosan oligomers as novel gene delivery vectors in epithelial cell lines.

    PubMed

    Thanou, M; Florea, B I; Geldof, M; Junginger, H E; Borchard, G

    2002-01-01

    Quaternized modifications of chitosan present characteristics that might be useful in DNA condensing and efficient gene delivery. Trimethylated chitosan (TMO) was synthesized from oligomeric chitosan (<20 monomer units). TMOs spontaneously formed complexes (chitoplexes) with RSV-alpha3 luciferase plasmid DNA. These complexes were characterized by photon correlation spectroscopy and were investigated for their ability to transfect COS-1 and Caco-2 cell lines in the presence and absence of fetal calf serum and compared with DOTAP (N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium sulphate) lipoplexes. Additionally, their effect on the viability of the respective cell cultures was investigated using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. Results showed that quaternized chitosan oligomers were able to condense DNA and form complexes with a size ranging from 200 to 500 nm. Chitoplexes proved to transfect COS-1 cells, however, to a lesser extent than DOTAP-DNA lipoplexes. The quaternized oligomer derivatives appeared to be superior to oligomeric chitosan. The presence of fetal calf serum (FCS) did not affect the transfection efficiency of the chitoplexes, whereas the transfection efficiency of DOTAP DNA complexes was decreased. Cells remained 100% viable in the presence of chitosan oligomers whereas viability of DOTAP treated cells decreased to approximately 50% in both cell lines. Both DOTAP-DNA lipoplexes and chitoplexes resulted in less transfection efficiency in Caco-2 cell cultures than in COS-1 cells; however quaternized chitosan oligomers proved to be superior to DOTAP. Effects on the viability of Caco-2 cells were similar to the effects observed in COS-1 cells. We conclude that trimethylated chitosan-DNA complexes present suitable characteristics and the potential to be used as gene delivery vectors.

  16. Chemical evolution. XXI - The amino acids released on hydrolysis of HCN oligomers

    NASA Technical Reports Server (NTRS)

    Ferris, J. P.; Wos, J. D.; Nooner, D. W.; Oro, J.

    1974-01-01

    Major amino acids released by hydrolysis of acidic and basic HCN oligomers are identified by chromatography as Gly, Asp, and diaminosuccinic acid. Smaller amounts of Ala, Ile and alpha-aminoisobutyric acid are also detected. The amino acids released did not change appreciably when the hydrolysis medium was changed from neutral to acidic or basic. The presence of both meso and d, l-diaminosuccinic acids was established by paper chromatography and on an amino acid analyzer.

  17. Effect of shear on the desorption of oligomers in nanoscopically confined films

    NASA Astrophysics Data System (ADS)

    Manias, E.; Hadziioannou, G.; ten Brinke, G.

    1994-07-01

    Bitsanis et al. J. Chem. Phys. 99, 5520 (1993) found that in nanoscopically confined films between strongly physisorbing surfaces chains with many contacts with the walls are irreversibly adsorbed. When shear is imposed to these systems molecular dynamics (MD) simulations show that the majority of the adsorbed oligomers adopts flat conformations on top of the walls. Although these conformations are characterized by high molecular adsorption energies, the same MD simulations show that desorption is strongly promoted by shear. The underlying mechanism is discussed.

  18. Thermal stability of hydrophobic helical oligomers: a lattice simulation study in explicit water.

    PubMed

    Romero-Vargas Castrillón, Santiago; Matysiak, Silvina; Stillinger, Frank H; Rossky, Peter J; Debenedetti, Pablo G

    2012-08-23

    We investigate the thermal stability of helical hydrophobic oligomers using a three-dimensional, water-explicit lattice model and the Wang-Landau Monte Carlo method. The degree of oligomer helicity is controlled by the parameter ε(mm) < 0, which mimics monomer-monomer hydrogen bond interactions leading to the formation of helical turns in atomistic proteins. We vary |ε(mm)| between 0 and 4.5 kcal/mol and therefore investigate systems ranging from flexible homopolymers (i.e., those with no secondary structure) to helical oligomers that are stable over a broad range of temperatures. We find that systems with |ε(mm)| ≤ 2.0 kcal/mol exhibit a broad thermal unfolding transition at high temperature, leading to an ensemble of random coils. In contrast, the structure of conformations involved in a second, low-temperature, transition is strongly dependent on |ε(mm)|. Weakly helical oligomers are observed when |ε(mm)| ≤ 1.0 kcal/mol and exhibit a low-temperature, cold-unfolding-like transition to an ensemble of strongly water-penetrated globular conformations. For higher |ε(mm)| (1.7 kcal/mol ≤ |ε(mm)| ≤ 2.0 kcal/mol), cold unfolding is suppressed, and the low-temperature conformational transition becomes a "crystallization", in which a "molten" helix is transformed into a defect-free helix. The molten helix preserves ≥50% of the helical contacts observed in the "crystal" at a lower temperature. When |ε(mm)| = 4.5 kcal/mol, we find that conformational transitions are largely suppressed within the range of temperatures investigated.

  19. A Recombinant Fungal Chitin Deacetylase Produces Fully Defined Chitosan Oligomers with Novel Patterns of Acetylation.

    PubMed

    Naqvi, Shoa; Cord-Landwehr, Stefan; Singh, Ratna; Bernard, Frank; Kolkenbrock, Stephan; El Gueddari, Nour Eddine; Moerschbacher, Bruno M

    2016-11-15

    Partially acetylated chitosan oligosaccharides (paCOS) are potent biologics with many potential applications, and their bioactivities are believed to be dependent on their structure, i.e., their degrees of polymerization and acetylation, as well as their pattern of acetylation. However, paCOS generated via chemical N-acetylation or de-N-acetylation of GlcN or GlcNAc oligomers, respectively, typically display random patterns of acetylation, making it difficult to control and predict their bioactivities. In contrast, paCOS produced from chitin deacetylases (CDAs) acting on chitin oligomer substrates may have specific patterns of acetylation, as shown for some bacterial CDAs. However, compared to what we know about bacterial CDAs, we know little about the ability of fungal CDAs to produce defined paCOS with known patterns of acetylation. Therefore, we optimized the expression of a chitin deacetylase from the fungus Puccinia graminis f. sp. tritici in Escherichia coli The best yield of functional enzyme was obtained as a fusion protein with the maltose-binding protein (MBP) secreted into the periplasmic space of the bacterial host. We characterized the MBP fusion protein from P. graminis (PgtCDA) and tested its activity on different chitinous substrates. Mass spectrometric sequencing of the products obtained by enzymatic deacetylation of chitin oligomers, i.e., tetramers to hexamers, revealed that PgtCDA generated paCOS with specific acetylation patterns of A-A-D-D, A-A-D-D-D, and A-A-D-D-D-D, respectively (A, GlcNAc; D, GlcN), indicating that PgtCDA cannot deacetylate the two GlcNAc units closest to the oligomer's nonreducing end. This unique property of PgtCDA significantly expands the so far very limited library of well-defined paCOS available to test their bioactivities for a wide variety of potential applications.

  20. A Foldamer-Dendrimer Conjugate Neutralizes Synaptotoxic β-Amyloid Oligomers

    PubMed Central

    Fülöp, Lívia; Mándity, István M.; Juhász, Gábor; Szegedi, Viktor; Hetényi, Anasztázia; Wéber, Edit; Bozsó, Zsolt; Simon, Dóra; Benkő, Mária; Király, Zoltán; Martinek, Tamás A.

    2012-01-01

    Background and Aims Unnatural self-organizing biomimetic polymers (foldamers) emerged as promising materials for biomolecule recognition and inhibition. Our goal was to construct multivalent foldamer-dendrimer conjugates which wrap the synaptotoxic β-amyloid (Aβ) oligomers with high affinity through their helical foldamer tentacles. Oligomeric Aβ species play pivotal role in Alzheimer's disease, therefore recognition and direct inhibition of this undruggable target is a great current challenge. Methods and Results Short helical β-peptide foldamers with designed secondary structures and side chain chemistry patterns were applied as potential recognition segments and their binding to the target was tested with NMR methods (saturation transfer difference and transferred-nuclear Overhauser effect). Helices exhibiting binding in the µM region were coupled to a tetravalent G0-PAMAM dendrimer. In vitro biophysical (isothermal titration calorimetry, dynamic light scattering, transmission electron microscopy and size-exclusion chromatography) and biochemical tests (ELISA and dot blot) indicated the tight binding between the foldamer conjugates and the Aβ oligomers. Moreover, a selective low nM interaction with the low molecular weight fraction of the Aβ oligomers was found. Ex vivo electrophysiological experiments revealed that the new material rescues the long-term potentiation from the toxic Aβ oligomers in mouse hippocampal slices at submicromolar concentration. Conclusions The combination of the foldamer methodology, the fragment-based approach and the multivalent design offers a pathway to unnatural protein mimetics that are capable of specific molecular recognition, and has already resulted in an inhibitor for an extremely difficult target. PMID:22859942

  1. Intentional overdose with insulin glargine and insulin aspart.

    PubMed

    Tofade, Toyin S; Liles, E Allen

    2004-10-01

    Reports of intentional massive overdoses of insulin are infrequent. A review of the literature revealed no reports of overdose attempts with either insulin glargine or insulin aspart. We report the case of a 33-year-old woman without diabetes mellitus who intentionally injected herself with an overdose of both products, which belonged to her husband. She arrived at the emergency department 15 hours after her suicide attempt, which took place the night before. Her husband had checked her blood glucose level throughout the night and had given her high-carbohydrate drinks and foods. The patient had a history of obsessive-compulsive disorder, major depression, and numerous suicide attempts. She recovered from the resulting hypoglycemia after 40 hours of dextrose infusion and was transferred to a mental health facility. The main danger associated with insulin overdose is the resultant hypoglycemia and its effects on the central nervous system; hypokalemia, hypophosphatemia, and hypomagnesemia also can develop with excess insulin administration. Dextrose infusion, with liberal oral intake when possible, and monitoring for electrolyte changes, making adjustments as needed, are recommended for the treatment of intentional insulin overdose.

  2. 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.

  3. Fabrication of an antibody-aptamer sandwich assay for electrochemical evaluation of levels of β-amyloid oligomers

    PubMed Central

    Zhou, Yanli; Zhang, Huanqing; Liu, Lantao; Li, Congming; Chang, Zhu; Zhu, Xu; Ye, Baoxian; Xu, Maotian

    2016-01-01

    Amyloid β-peptide (Aβ) in its oligomeric form is often considered as the most toxic species in Alzheimer’s disease (AD), and thus Aβ oligomer is a potentially promising candidate biomarker for AD diagnosis. The development of a sensitive and reliable method for monitoring the Aβ oligomer levels in body fluids is an urgent requirement in order to predict the severity and progression at early or preclinical stages of AD. Here, we show a proof of concept for a sensitive and specific detection of Aβ oligomers by an antibody-aptamer sandwich assay. The antibodies of Aβ oligomers and a nanocomposite of gold nanoparticles with aptamer and thionine (aptamer-Au-Th) were used as the recognition element and the detection probe for specifically binding to Aβ oligomers, respectively. The electrochemical signal of Th reduction could provide measurable electrochemical signals, and a low limit of detection (100 pM) was achieved due to the signal amplification by high loading of Th on the gold nanoparticles. The feasibility of the assay was verified by test of Aβ oligomers in artificial cerebrospinal fluid. The proposed strategy presents valuable information related to early diagnosis of AD process. PMID:27725775

  4. Aβ42 assembles into specific β-barrel pore-forming oligomers in membrane-mimicking environments

    PubMed Central

    Serra-Batiste, Montserrat; Ninot-Pedrosa, Martí; Bayoumi, Mariam; Gairí, Margarida; Maglia, Giovanni; Carulla, Natàlia

    2016-01-01

    The formation of amyloid-β peptide (Aβ) oligomers at the cellular membrane is considered to be a crucial process underlying neurotoxicity in Alzheimer’s disease (AD). Therefore, it is critical to characterize the oligomers that form within a membrane environment. To contribute to this characterization, we have applied strategies widely used to examine the structure of membrane proteins to study the two major Aβ variants, Aβ40 and Aβ42. Accordingly, various types of detergent micelles were extensively screened to identify one that preserved the properties of Aβ in lipid environments—namely the formation of oligomers that function as pores. Remarkably, under the optimized detergent micelle conditions, Aβ40 and Aβ42 showed different behavior. Aβ40 aggregated into amyloid fibrils, whereas Aβ42 assembled into oligomers that inserted into lipid bilayers as well-defined pores and adopted a specific structure with characteristics of a β-barrel arrangement that we named β-barrel pore-forming Aβ42 oligomers (βPFOsAβ42). Because Aβ42, relative to Aβ40, has a more prominent role in AD, the higher propensity of Aβ42 to form βPFOs constitutes an indication of their relevance in AD. Moreover, because βPFOsAβ42 adopt a specific structure, this property offers an unprecedented opportunity for testing a hypothesis regarding the involvement of βPFOs and, more generally, membrane-associated Aβ oligomers in AD. PMID:27621459

  5. 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

    2015-10-29

    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.

  6. 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

  7. Interaction of toxic and non-toxic HypF-N oligomers with lipid bilayers investigated at high resolution with atomic force microscopy

    PubMed Central

    Oropesa-Nuñez, Reinier; Seghezza, Silvia; Dante, Silvia; Diaspro, Alberto; Cascella, Roberta; Cecchi, Cristina; Stefani, Massimo; Chiti, Fabrizio; Canale, Claudio

    2016-01-01

    Protein misfolded oligomers are considered the most toxic species amongst those formed in the process of amyloid formation and the molecular basis of their toxicity, although not completely understood, is thought to originate from the interaction with the cellular membrane. Here, we sought to highlight the molecular determinants of oligomer-membrane interaction by atomic force microscopy. We monitored the interaction between multiphase supported lipid bilayers and two types of HypF-N oligomers displaying different structural features and cytotoxicities. By our approach we imaged with unprecedented resolution the ordered and disordered lipid phases of the bilayer and different oligomer structures interacting with either phase. We identified the oligomers and lipids responsible for toxicity and, more generally, we established the importance of the membrane lipid component in mediating oligomer toxicity. Our findings support the importance of GM1 ganglioside in mediating the oligomer-bilayer interaction and support a mechanism of oligomer cytotoxicity involving bilayer destabilization by globular oligomers within GM1-rich ordered raft regions rather than by annular oligomers in the surrounding disordered membrane domains. PMID:27391440

  8. Benzothienobenzothiophene-based conjugated oligomers as semiconductors for stable organic thin-film transistors.

    PubMed

    Yu, Han; Li, Weili; Tian, Hongkun; Wang, Haibo; Yan, Donghang; Zhang, Jingping; Geng, Yanhou; Wang, Fosong

    2014-04-09

    Two benzothienobenzothiophene (BTBT)-based conjugated oligomers, i.e., 2,2'-bi[1]benzothieno[3,2-b][1]benzothiophene (1) and 5,5'-bis([1]benzothieno[3,2-b][1]benzothiophen-2-yl)-2,2'-bithiophene (2), were prepared and characterized. Both oligomers exhibit excellent thermal stability, with 5% weight-loss temperatures (T(L)) above 370 °C; no phase transition was observed before decomposition. The highest occupied molecular orbital (HOMO) levels of 1 and 2 are -5.3 and -4.9 eV, respectively, as measured by ultraviolet photoelectron spectroscopy. Thin-film X-ray diffraction and atomic force microscopy characterizations indicate that both oligomers form highly crystalline films with large domain sizes on octadecyltrimethoxysilane-modified substrates. Organic thin-film transistors with top-contact and bottom-gate geometry based on 1 and 2 exhibited mobilities up to 2.12 cm(2)/V·s for 1 and 1.39 cm(2)/V·s for 2 in an ambient atmosphere. 1-based devices exhibited great air and thermal stabilities, as evidenced by the slight performance degradation after 2 months of storage under ambient conditions and after thermal annealing at temperatures below 250 °C.

  9. The adsorption of short single-stranded DNA oligomers to mineral surfaces.

    PubMed

    Cleaves, H James; Crapster-Pregont, Ellen; Jonsson, Caroline M; Jonsson, Christopher L; Sverjensky, Dimitri A; Hazen, Robert A

    2011-06-01

    We studied the adsorption of short single-stranded deoxyribonucleic acid (ssDNA) oligomers, of approximately 30 nucleotides (nt) in length, of varying sequence, adenine+guanine+cytosine (AGC) content, and propensity to form secondary structure, to equal surface area samples of olivine, pyrite, calcite, hematite, and rutile in 0.1M NaCl, 0.05M pH 8.1 KHCO(3) buffer. Although the mineral surfaces have widely varying points of zero charge, under these conditions they show remarkably similar adsorption of ssDNA regardless of oligomer characteristics. Mineral surfaces appear to accommodate ssDNA comparably, or ssDNA oligomers of this length are able to find binding sites of comparable strength and density due to their flexibility, despite the disparate surface properties of the different minerals. This may partially be due charge shielding by the ionic strength of the solutions tested, which are typical of many natural environments. These results may have some bearing on the adsorption and accumulation of biologically derived nucleic acids in sediments as well as the abiotic synthesis of nucleic acids before the origin of life.

  10. Supramolecular Order of 2,5-Bis(dodecanoxy)phenyleneethynylene-Butadiyne Oligomers in the Solid State.

    PubMed

    Vergara, Edgar; Arias, Eduardo; Moggio, Ivana; Gallardo-Vega, Carlos; Ziolo, Ronald F; Jiménez-Barrera, Rosa M; Navarro, Damaso; Rodríguez, Oliverio; Fernández, Salvador; Herrera, Manuel

    2015-06-23

    The supramolecular order of a 2,5-bis(dodecanoxy)phenyleneethynylene-butadiyne series of rod-like oligomers with 2, 4, 6, and 8 phenyleneethynylene moieties was studied in the solid state by differential scanning calorimetry (DSC), temperature-dependent small- and wide-angle X-ray scattering (SWAXS), selected area electron diffraction (SAED), polarized optical microscopy (POM), high-resolution transmission microscopy (HRTEM), and scanning tunneling microscopy (STM). It was found that all of the oligomers self-assemble in blocks of molecules that resemble bricks that are randomly oriented. These oligomers are described as sanidic liquid crystals as a term to classify their mesomorphic behavior because of their brick or board-like structure. The strong π-π interaction that governs the package of conjugated backbones was evidenced by the reiterative distances of 0.36 ± 0.017 nm found by SWAXS and 0.32 ± 0.017 nm found by HRTEM. A STM study of a cast film of the tetramer deposited on highly oriented pyrolitic graphite (HOPG) allowed for the visualization and determination of the conjugated backbone length of 2.48 nm and a phenyl-phenyl distance of 0.34 nm, suggesting that the molecules are stacked in lamellae perpendicularly aligned to the substrate.

  11. Aβ40 Oligomers Identified as a Potential Biomarker for the Diagnosis of Alzheimer's Disease

    PubMed Central

    Wang, Xuemei; Magdangal, Erika; Salisbury, Cleo; Peretz, David; Zuckermann, Ronald N.; Connolly, Michael D.; Hansson, Oskar; Minthon, Lennart; Zetterberg, Henrik; Blennow, Kaj; Fedynyshyn, Joseph P.; Allauzen, Sophie

    2010-01-01

    Alzheimer's Disease (AD) is the most prevalent form of dementia worldwide, yet the development of therapeutics has been hampered by the absence of suitable biomarkers to diagnose the disease in its early stages prior to the formation of amyloid plaques and the occurrence of irreversible neuronal damage. Since oligomeric Aβ species have been implicated in the pathophysiology of AD, we reasoned that they may correlate with the onset of disease. As such, we have developed a novel misfolded protein assay for the detection of soluble oligomers composed of Aβ x-40 and x-42 peptide (hereafter Aβ40 and Aβ42) from cerebrospinal fluid (CSF). Preliminary validation of this assay with 36 clinical samples demonstrated the presence of aggregated Aβ40 in the CSF of AD patients. Together with measurements of total Aβ42, diagnostic sensitivity and specificity greater than 95% and 90%, respectively, were achieved. Although larger sample populations will be needed to confirm this diagnostic sensitivity, our studies demonstrate a sensitive method of detecting circulating Aβ40 oligomers from AD CSF and suggest that these oligomers could be a powerful new biomarker for the early detection of AD. PMID:21209907

  12. Oligomers modulate interfibril branching and mass transport properties of collagen matrices.

    PubMed

    Whittington, Catherine F; Brandner, Eric; Teo, Ka Yaw; Han, Bumsoo; Nauman, Eric; Voytik-Harbin, Sherry L

    2013-10-01

    Mass transport within collagen-based matrices is critical to tissue development, repair, and pathogenesis, as well as the design of next-generation tissue engineering strategies. This work shows how collagen precursors, specified by intermolecular cross-link composition, provide independent control of collagen matrix mechanical and transport properties. Collagen matrices were prepared from tissue-extracted monomers or oligomers. Viscoelastic behavior was measured in oscillatory shear and unconfined compression. Matrix permeability and diffusivity were measured using gravity-driven permeametry and integrated optical imaging, respectively. Both collagen types showed an increase in stiffness and permeability hindrance with increasing collagen concentration (fibril density); however, different physical property–concentration relationships were noted. Diffusivity was not affected by concentration for either collagen type over the range tested. In general, oligomer matrices exhibited a substantial increase in stiffness and only a modest decrease in transport properties when compared with monomer matrices prepared at the same concentration. The observed differences in viscoelastic and transport properties were largely attributed to increased levels of interfibril branching within oligomer matrices. The ability to relate physical properties to relevant microstructure parameters, including fibril density and interfibril branching, is expected to advance the understanding of cell–matrix signaling, as well as facilitate model-based prediction and design of matrix-based therapeutic strategies.

  13. Cell-physiological effects of elastin derived (VGVAPG)n oligomers in a unicellular model system.

    PubMed

    Köhidai, László; Kun, Lídia; Eva, Pállinger; Csaba, György; Mihala, Nikolett; Majer, Zsuzsa; Süli-Vargha, Helga

    2004-07-01

    Elastin is one of the most significant components of the extracellular matrix, which supports the stretchiness of the blood vessels via its helical structure and cross-links. Enzymatic decomposition of this protein could induce chemotactic responses of cell populations in the surrounding tissues by several peptide sequences, e.g. XGXXPG. In our present work the VGVAPG variant and its oligomers were studied. The objective of the experiments was to learn (i) whether the chemotactic effect of these peptides is general in different levels of phylogeny: (ii) whether increasing the number of monomer units influences the chemotactic behaviour of the cell? The trimer had the strongest chemoattractant effect in a wide concentration range (10(-12) - 10(-7) M), while the monomer and the pentamer were chemorepellent. All tri-, tetra-, penta- and hexamers could chemotactically select subpopulations with a high chemotactic responsiveness to the identical peptide, in the long term. With regard to its repellent effect, the pentamer had a negative effect on phagocytosis. All six oligomers had a growth-promoter effect in Tetrahymena. The characteristic cell-physiological effects of VGVAPG oligomers signal that molecules of the extracellular matrix can induce identical responses even in lower levels of phylogeny, e.g. in the Ciliates.

  14. Bacterial adhesion and growth reduction by novel rubber-derived oligomers

    PubMed Central

    Badawy, Hope T.; Pasetto, Pamela; Mouget, Jean-Luc; Pilard, Jean-François; Cutright, Teresa J.

    2013-01-01

    In the medical field, attached bacteria can cause infections associated with catheters, incisions, burns, and medical implants especially in immunocompromised patients. The problem is exacerbated by the fact that attached bacteria are ~1000 times more resistant to antibiotics than planktonic cells. The rapid spread of antibiotic resistance in these and other organisms has led to a significant need to find new methods for preventing bacterial attachment. The goal of this research was to evaluate the effectiveness of novel polymer coatings to prevent the attachment of three medically relevant bacteria. Tests were conducted with Pseudomonas aeruginosa, Staphylococcus epidermidis, and Staphylococcus aureus for oligomers derived from modifications of natural rubber (cis 1,4-polyisoprene). The different oligomers were: PP04, with no quaternary ammonium (QA); MV067, one QA; PP06, three QA groups. In almost all experiments, cell attachment was inhibited to various extents as long as the oligomers were used. PP06 was the most effective as it decreased the planktonic cell numbers by at least 50% for all bacteria. Differences between species sensitivity were also observed. P. aeruginosa was the most resistant bacteria tested, S. aureus, the most sensitive. Further experiments are required to understand the full extent and mode of the antimicrobial properties of these surfaces. PMID:23921230

  15. Aβ1-42 monomers or oligomers have different effects on autophagy and apoptosis.

    PubMed

    Guglielmotto, Michela; Monteleone, Debora; Piras, Antonio; Valsecchi, Valeria; Tropiano, Marta; Ariano, Stefania; Fornaro, Michele; Vercelli, Alessandro; Puyal, Julien; Arancio, Ottavio; Tabaton, Massimo; Tamagno, Elena

    2014-10-01

    The role of autophagy and its relationship with apoptosis in Alzheimer disease (AD) pathogenesis is poorly understood. Disruption of autophagy leads to buildup of incompletely digested substrates, amyloid-β (Aβ) peptide accumulation in vacuoles and cell death. Aβ, in turn, has been found to affect autophagy. Thus, Aβ might be part of a loop in which it is both the substrate of altered autophagy and its cause. Given the relevance of different soluble forms of Aβ1-42 in AD, we have investigated whether monomers and oligomers of the peptide have a differential role in causing altered autophagy and cell death. Using differentiated SK-N-BE neuroblastoma cells, we found that monomers hamper the formation of the autophagic BCL2-BECN1/Beclin 1 complex and activate the MAPK8/JNK1-MAPK9/JNK2 pathway phosphorylating BCL2. Monomers also inhibit apoptosis and allow autophagy with intracellular accumulation of autophagosomes and elevation of levels of BECN1 and LC3-II, resulting in an inhibition of substrate degradation due to an inhibitory action on lysosomal activity. Oligomers, in turn, favor the formation of the BCL2-BECN1 complex favoring apoptosis. In addition, they cause a less profound increase in BECN1 and LC3-II levels than monomers without affecting the autophagic flux. Thus, data presented in this work show a link for autophagy and apoptosis with monomers and oligomers, respectively. These studies are likely to help the design of novel disease modifying therapies.

  16. Soluble amyloid-β oligomers as synaptotoxins leading to cognitive impairment in Alzheimer’s disease

    PubMed Central

    Ferreira, Sergio T.; Lourenco, Mychael V.; Oliveira, Mauricio M.; De Felice, Fernanda G.

    2015-01-01

    Alzheimer’s disease (AD) is the most common form of dementia in the elderly, and affects millions of people worldwide. As the number of AD cases continues to increase in both developed and developing countries, finding therapies that effectively halt or reverse disease progression constitutes a major research and public health challenge. Since the identification of the amyloid-β peptide (Aβ) as the major component of the amyloid plaques that are characteristically found in AD brains, a major effort has aimed to determine whether and how Aβ leads to memory loss and cognitive impairment. A large body of evidence accumulated in the past 15 years supports a pivotal role of soluble Aβ oligomers (AβOs) in synapse failure and neuronal dysfunction in AD. Nonetheless, a number of basic questions, including the exact molecular composition of the synaptotoxic oligomers, the identity of the receptor(s) to which they bind, and the signaling pathways that ultimately lead to synapse failure, remain to be definitively answered. Here, we discuss recent advances that have illuminated our understanding of the chemical nature of the toxic species and the deleterious impact they have on synapses, and have culminated in the proposal of an Aβ oligomer hypothesis for Alzheimer’s pathogenesis. We also highlight outstanding questions and challenges in AD research that should be addressed to allow translation of research findings into effective AD therapies. PMID:26074767

  17. Synaptic Amyloid-β Oligomers Precede p-Tau and Differentiate High Pathology Control Cases

    PubMed Central

    Bilousova, Tina; Miller, Carol A.; Poon, Wayne W.; Vinters, Harry V.; Corrada, Maria; Kawas, Claudia; Hayden, Eric Y.; Teplow, David B.; Glabe, Charles; Albay, Ricardo; Cole, Gregory M.; Teng, Edmond; Gylys, Karen H.

    2017-01-01

    Amyloid-β (Aβ) and hyperphosphorylated tau (p-tau) aggregates form the two discrete pathologies of Alzheimer disease (AD), and oligomeric assemblies of each protein are localized to synapses. To determine the sequence by which pathology appears in synapses, Aβ and p-tau were quantified across AD disease stages in parietal cortex. Nondemented cases with high levels of AD-related pathology were included to determine factors that confer protection from clinical symptoms. Flow cytometric analysis of synaptosome preparations was used to quantify Aβ and p-tau in large populations of individual synaptic terminals. Soluble Aβ oligomers were assayed by a single antibody sandwich enzyme-linked immunosorbent assay. Total in situ Aβ was elevated in patients with early- and late-stage AD dementia, but not in high pathology nondemented controls compared with age-matched normal controls. However, soluble Aβ oligomers were highest in early AD synapses, and this assay distinguished early AD cases from high pathology controls. Overall, synapse-associated p-tau did not increase until late-stage disease in human and transgenic rat cortex, and p-tau was elevated in individual Aβ-positive synaptosomes in early AD. These results suggest that soluble oligomers in surviving neocortical synaptic terminals are associated with dementia onset and suggest an amyloid cascade hypothesis in which oligomeric Aβ drives phosphorylated tau accumulation and synaptic spread. These results indicate that antiamyloid therapies will be less effective once p-tau pathology is developed. PMID:26718979

  18. Multifunctional oligomer incorporation: a potent strategy to enhance the transfection activity of poly(l-lysine).

    PubMed

    Liu, Shuai; Yang, Jixiang; Ren, Hongqi; O'Keeffe-Ahern, Jonathan; Zhou, Dezhong; Zhou, Hao; Chen, Jiatong; Guo, Tianying

    2016-03-01

    Natural polycations, such as poly(l-lysine) (PLL) and chitosan (CS), have inherent superiority as non-viral vectors due to their unparalleled biocompatibility and biodegradability. However, the application was constrained by poor transfection efficiency and safety concerns. Since previous modification strategies greatly weakened the inherent advantages of natural polycations, developing a strategy for functional group introduction with broad applicability to enhance the transfection efficiency of natural polycations without compromising their cationic properties is imperative. Herein, two uncharged functional diblock oligomers P(DMAEL-b-NIPAM) and P(DMAEL-b-Vlm) were prepared from a lactose derivative, N-iso-propyl acrylamide (NIPAM) as well as 1-vinylimidazole (Vlm) and further functionalized with four small ligands folate, glutathione, cysteine and arginine, respectively, aiming to enhance the interactions of complexes with cells, which were quantified utilizing a quartz crystal microbalance (QCM) biosensor, circumventing the tedious material screening process of cell transfection. Upon incorporation with PLL and DNA, the multifunctional oligomers endow the formulated ternary complexes with great properties suitable for transfection, such as anti-aggregation in serum, destabilized endosome membrane, numerous functional sites for promoted endocytosis and therefore robust transfection activity. Furthermore, different from the conventional strategy of decreasing cytotoxicity by reducing the charge density, the multifunctional oligomer incorporation strategy maintains the highly positive charge density, which is essential for efficient cellular uptake. This system develops a new platform to modify natural polycations towards clinical gene therapy.

  19. Synthesis of polyamide oligomers based on 14-amino-3,6,9, 12-tetraoxatetradecanoic acid.

    PubMed

    Dhawan, R; Kadijk, M G; Joikinen, T J; Feng, M; Ansell, S M

    2000-01-01

    A series of oligomers of polyamides based on 14-amino-3,6,9, 12-tetraoxatetradecanoic acid monomers (ATTAn) was synthesized. These materials were designed as monodisperse analogues of poly(ethylene glycol) for use in biomedical applications where reproducible behavior is important. Synthesis of the monomer was evaluated using two routes. For small-scale preparations, tetraethylene glycol (TEG) was monoprotected with dihydropyran, converted to an alkoxide, and alkylated with ethyl bromoacetate. On larger scales, TEG was alkylated directly by treatment with sodium, followed by ethyl bromoacetate. The amine function was introduced by mesylation followed by treatment with sodium azide. Reduction of the azide to amino groups was performed over Pd/C using either hydrogen or formic acid as proton sources. Assembly of the oligomers was accomplished using standard DCC/NHS chemistry and an iterative dimerization sequence after appropriate deprotection of a pair of monomers. The amino group was protected by retaining the azido group as a latent amine. A series of ATTAn oligomers was prepared (n = 1-8). A lipid conjugate of the octamer, ATTA8-DSPE, was synthesized.

  20. Conformational analysis of o-phenylenes: helical oligomers with frayed ends.

    PubMed

    Hartley, C Scott; He, Jian

    2010-12-17

    The o-phenylenes represent a fundamental class of conjugated polymers that, unlike the isomeric p-phenylenes, should exhibit rich conformational behavior. Recently, we reported the synthesis and characterization of a series of o-phenylene oligomers featuring unusual electronic properties, including surprisingly long-range delocalization as measured by UV-vis spectroscopy and hypsochromic shifts in fluorescence maxima with increasing length. To rationalize these properties, we hypothesized that the oligomers predominantly assume a stacked helical conformation in solution. This assertion, however, was supported by only indirect evidence. Here we present a thorough investigation of the conformational behavior of this series of o-phenylenes by dynamic NMR spectroscopy and computational chemistry. EXSY experiments, in combination with other two-dimensional NMR techniques, provided full (1)H chemical shift assignments for at least the two most prevalent conformers for each member of the series (hexamer to dodecamer). GIAO density functional theory calculations were then used to relate the NMR data to specific molecular geometries. We have found that the o-phenylenes do indeed assume stacked helical conformations with disorder occurring at the ends. Thus, the o-phenylene motif appears to have great potential as a means to organize arenes into predictable three-dimensional arrangements. Our results also illustrate the power of (1)H NMR GIAO predictions in the solution-phase conformational analysis of oligomers, particularly those with a high density of aromatic subunits.

  1. NMR studies of DNA oligomers and their interactions with minor groove binding ligands

    SciTech Connect

    Fagan, Patricia A.

    1996-05-01

    The cationic peptide ligands distamycin and netropsin bind noncovalently to the minor groove of DNA. The binding site, orientation, stoichiometry, and qualitative affinity of distamycin binding to several short DNA oligomers were investigated by NMR spectroscopy. The oligomers studied contain A,T-rich or I,C-rich binding sites, where I = 2-desaminodeoxyguanosine. I•C base pairs are functional analogs of A•T base pairs in the minor groove. The different behaviors exhibited by distamycin and netropsin binding to various DNA sequences suggested that these ligands are sensitive probes of DNA structure. For sites of five or more base pairs, distamycin can form 1:1 or 2:1 ligand:DNA complexes. Cooperativity in distamycin binding is low in sites such as AAAAA which has narrow minor grooves, and is higher in sites with wider minor grooves such as ATATAT. The distamycin binding and base pair opening lifetimes of I,C-containing DNA oligomers suggest that the I,C minor groove is structurally different from the A,T minor groove. Molecules which direct chemistry to a specific DNA sequence could be used as antiviral compounds, diagnostic probes, or molecular biology tools. The author studied two ligands in which reactive groups were tethered to a distamycin to increase the sequence specificity of the reactive agent.

  2. Lysosomal Enzyme Glucocerebrosidase Protects against Aβ1-42 Oligomer-Induced Neurotoxicity

    PubMed Central

    Kam, Tae-In; Yun, Seungpil; Kim, Sangjune; Park, Hyejin; Hwang, Heehong; Pletnikova, Olga; Troncoso, Juan C.; Dawson, Valina L.; Dawson, Ted M.; Ko, Han Seok

    2015-01-01

    Glucocerebrosidase (GCase) functions as a lysosomal enzyme and its mutations are known to be related to many neurodegenerative diseases, including Gaucher’s disease (GD), Parkinson’s disease (PD), and Dementia with Lewy Bodies (DLB). However, there is little information about the role of GCase in the pathogenesis of Alzheimer’s disease (AD). Here we demonstrate that GCase protein levels and enzyme activity are significantly decreased in sporadic AD. Moreover, Aβ1–42 oligomer treatment results in neuronal cell death that is concomitant with decreased GCase protein levels and enzyme activity, as well as impairment in lysosomal biogenesis and acidification. Importantly, overexpression of GCase promotes the lysosomal degradation of Aβ1–42 oligomers, restores the lysosomal impairment, and protects against the toxicity in neurons treated with Aβ1–42 oligomers. Our findings indicate that a deficiency of GCase could be involved in progression of AD pathology and suggest that augmentation of GCase activity may be a potential therapeutic option for the treatment of AD. PMID:26629917

  3. New strategy for stable-isotope-aided, multidimensional NMR spectroscopy of DNA oligomers

    SciTech Connect

    Ono, Okira; Tate, Shin-Ichi; Kainosho, Masatsune

    1994-12-01

    Nuclear Magnetic Resonance (NMR) is the most efficient method for determining the solution structures of biomolecules. By applying multidimensional heteronuclear NMR techniques to {sup 13}C/{sup 15}N-labeled proteins, we can determine the solution structures of proteins with molecular mass of 20 to 30kDa at an accuracy similar to that of x-ray crystallography. Improvements in NMR instrumentation and techniques as well as the development of protein engineering methods for labeling proteins have rapidly advanced multidimensional heteronuclear NMR of proteins. In contrast, multidimensional heteronuclear NMR studies of nucleic acids is less advanced because there were no efficient methods for preparing large amounts of labeled DNA/RNA oligomers. In this report, we focused on the chemical synthesis of DNA oligomers labeled at specific residue(s). RNA oligomers with specific labels, which are difficult to synthesize by the enzyme method, can be synthes