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Artykuły w czasopismach na temat "Oligomeric forms"
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NEMOTO, Takayuki, i Nobuko SATO. "Oligomeric forms of the 90-kDa heat shock protein". Biochemical Journal 330, nr 2 (1.03.1998): 989–95. http://dx.doi.org/10.1042/bj3300989.
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Two isoforms of the 90-kDa heat shock protein, HSP90α and HSP90β, are present in the cytosol of mammalian cells. Analysis by polyacrylamide gel electrophoresis under nondenaturing conditions (native PAGE) revealed that HSP90α predominantly exists as a homodimer and that HSP90β is present mainly as a monomer [Minami, Kawasaki, Miyata, Suzuki and Yahara (1991) J. Biol. Chem. 266, 10099-10103]. However, only the dimeric form has been observed under other analytical conditions such as gradient centrifugation. In this study, therefore, we investigated native forms of HSP90 by use of immunochemical techniques with isoform-specific monoclonal antibodies recently developed in our laboratory. Glycerol gradient centrifugation at the physiological salt concentration as well as native PAGE analysis of rat liver cytosol revealed oligomeric forms of HSP90α sedimenting at 8-10S as predominant ones. On the other hand, the glycerol gradient centrifugation revealed multiple forms of HSP90β oligomers sedimenting at 6-12S. All of the HSP90β oligomers, however, migrated at 100-kDa monomer and 190-kDa dimer positions on native PAGE. A novel two-dimensional double native PAGE revealed that the entity was converted from the HSP90β dimer to monomers during the electrophoresis. The same PAGE further revealed that the HSP90α oligomer also dissociated into dimers during the electrophoresis. Full-length form of bacterially-expressed human HSP90α migrated as dimers, but a considerable amount did not penetrate into the gel under native PAGE conditions, indicating the existence of oligomeric forms. Electrophoretic studies of deletion mutants of HSP90 demonstrated that the C-terminal 200 amino acids were capable of forming oligomers. Taken together, we conclude that both of the HSP90 isoforms predominantly exist as oligomeric forms in the cytosol even under unstressed conditions but that they artificially dissociate into smaller forms when subjected to native PAGE.
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Harrison, R. A. "Preliminary characterization of the multiple forms of ram sperm hyaluronidase". Biochemical Journal 252, nr 3 (15.06.1988): 875–82. http://dx.doi.org/10.1042/bj2520875.
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An investigation was made of the inter-relationships and characteristics of various hyaluronidase forms isolated from ram spermatozoa. They were shown to be members of an oligomeric series, apparently formed by intermolecular disulphide cross-linking. Two monomer species were detected, alpha (Mr 89,600) and beta (Mr 81,200). Although the alpha species predominated, the two were evenly distributed throughout the oligomer population, and they shared antigenic determinants; the beta species did not arise from the alpha species as a result of catabolism following cell disruption. The oligomeric series was of the form [Hyal]n, where n = 1, 2, 4, 5, 6, 7 etc.; no trimer was detectable. Though essentially cationic, part of the hyaluronidase population also had anionic characteristics, probably due to oxidation of free thiol groups. In the anionic subpopulation tetramers and higher oligomers predominated, whereas the non-anionic subpopulation was composed of monomers, dimers and tetramers. The pH optimum of the monomer was 4.3 in 0.2 M-NaCl/0.1 M-sodium citrate, whereas that of the anionic oligomers was 4.9. Both serum albumin and polylysine stimulated enzyme activity at pH 4.0 in the absence of NaCl; polylysine was particularly effective. NaCl diminished the stimulatory effects, and essentially suppressed them above the pH optimum. The specific activities of different oligomer populations were the same as that of the monomer, and conversion of oligomers into monomer by reduction had likewise no effect upon the specific activity. Low concentrations of poly(vinyl alcohol), poly(ethylene glycol) or polyvinylpyrrolidone stabilized soluble hyaluronidase activity by preventing the enzyme's binding to surfaces; solutions of anionic oligomers were further stabilized by NaCl. Enzyme preparations were stable for several months frozen in the presence of poly(vinyl alcohol) and salt.
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Larson, Megan E., Susan J. Greimel, Fatou Amar, Michael LaCroix, Gabriel Boyle, Mathew A. Sherman, Hallie Schley i in. "Selective lowering of synapsins induced by oligomeric α-synuclein exacerbates memory deficits". Proceedings of the National Academy of Sciences 114, nr 23 (22.05.2017): E4648—E4657. http://dx.doi.org/10.1073/pnas.1704698114.
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Mounting evidence indicates that soluble oligomeric forms of amyloid proteins linked to neurodegenerative disorders, such as amyloid-β (Aβ), tau, or α-synuclein (αSyn) might be the major deleterious species for neuronal function in these diseases. Here, we found an abnormal accumulation of oligomeric αSyn species in AD brains by custom ELISA, size-exclusion chromatography, and nondenaturing/denaturing immunoblotting techniques. Importantly, the abundance of αSyn oligomers in human brain tissue correlated with cognitive impairment and reductions in synapsin expression. By overexpressing WT human αSyn in an AD mouse model, we artificially enhanced αSyn oligomerization. These bigenic mice displayed exacerbated Aβ-induced cognitive deficits and a selective decrease in synapsins. Following isolation of various soluble αSyn assemblies from transgenic mice, we found that in vitro delivery of exogenous oligomeric αSyn but not monomeric αSyn was causing a lowering in synapsin-I/II protein abundance. For a particular αSyn oligomer, these changes were either dependent or independent on endogenous αSyn expression. Finally, at a molecular level, the expression of synapsin genes SYN1 and SYN2 was down-regulated in vivo and in vitro by αSyn oligomers, which decreased two transcription factors, cAMP response element binding and Nurr1, controlling synapsin gene promoter activity. Overall, our results demonstrate that endogenous αSyn oligomers can impair memory by selectively lowering synapsin expression.
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You, Young Suk, Jae-Hoon Kim, Jong-Soo Lee i Hyeseong Cho. "The mitochodnrial E3 ligase MARCH5 resolves RIG-I and MAVS aggregates in innate immunity". Journal of Immunology 198, nr 1_Supplement (1.05.2017): 222.13. http://dx.doi.org/10.4049/jimmunol.198.supp.222.13.
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Abstract Ubiquitin proteasome system (UPS) on the mitochondrial is one of quality control systems that works as a first line of defense barrier against aggregated or misfolded proteins. In innate immunity formation of the MAVS(Mitochondrial anti-viral signaling protein) oligomers elicits robust type-I interferon induction upon viral infection and however, persistent RIG-I and MAVS complex rather leads to host immunopathology. We recently reported that mitochondria-resident E3 ligase, MARCH5, recognizes the oligomeric form of RIG-I and MAVS complex. MARCH5+/− mice and MARCH5 deficient immune cells exhibited low viral replication and elevated type-I interferon response to viral infection. MARCH5 bound RIG-I and MAVS complex only during viral infection when MAVS forms oligomer. MARCH5 mediates Lys-48-linked poly-ubiquitination chain addition to RIG-I and MAVS oligomer and induces the RIG-I/MAVS monomer. Next, we studies have suggested that a novel function of MARCH5 in inflammation signaling. Together, these data demonstrates that MARCH5 regulates oligomeric RIG-I and MAVS complex.
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Cerf, Emilie, Rabia Sarroukh, Shiori Tamamizu-Kato, Leonid Breydo, Sylvie Derclaye, Yves F. Dufrêne, Vasanthy Narayanaswami, Erik Goormaghtigh, Jean-Marie Ruysschaert i Vincent Raussens. "Antiparallel β-sheet: a signature structure of the oligomeric amyloid β-peptide". Biochemical Journal 421, nr 3 (15.07.2009): 415–23. http://dx.doi.org/10.1042/bj20090379.
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AD (Alzheimer's disease) is linked to Aβ (amyloid β-peptide) misfolding. Studies demonstrate that the level of soluble Aβ oligomeric forms correlates better with the progression of the disease than the level of fibrillar forms. Conformation-dependent antibodies have been developed to detect either Aβ oligomers or fibrils, suggesting that structural differences between these forms of Aβ exist. Using conditions which yield well-defined Aβ-(1–42) oligomers or fibrils, we studied the secondary structure of these species by ATR (attenuated total reflection)–FTIR (Fouriertransform infrared) spectroscopy. Whereas fibrillar Aβ was organized in a parallel β-sheet conformation, oligomeric Aβ displayed distinct spectral features, which were attributed to an antiparallel β-sheet structure. We also noted striking similarities between Aβ oligomers spectra and those of bacterial outer membrane porins. We discuss our results in terms of a possible organization of the antiparallel β-sheets in Aβ oligomers, which may be related to reported effects of these highly toxic species in the amyloid pathogenesis associated with AD.
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Tian, Huilai, Eliot Davidowitz, Patricia Lopez, Sharareh Emadi, James Moe i Michael Sierks. "Trimeric Tau Is Toxic to Human Neuronal Cells at Low Nanomolar Concentrations". International Journal of Cell Biology 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/260787.
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In Alzheimer’s disease (AD), tau aggregates into fibrils and higher order neurofibrillary tangles, a key histopathological feature of AD. However, soluble oligomeric tau species may play a more critical role in AD progression since these tau species correlate better with neuronal loss and cognitive dysfunction. Recent studies show that extracellular oligomeric tau can inhibit memory formation and synaptic function and also transmit pathology to neighboring neurons. However, the specific forms of oligomeric tau involved in toxicity are still unknown. Here, we used two splice variants of recombinant human tau and generated monomeric, dimeric, and trimeric fractions of each isoform. The composition of each fraction was verified chromatographically and also by atomic force microscopy. The toxicity of each fraction toward both human neuroblastoma cells and cholinergic-like neurons was assessed. Trimeric, but not monomeric or dimeric, tau oligomers of both splice variants were neurotoxic at low nanomolar concentrations. Further characterization of tau oligomer species with disease-specific modifications and morphologies is necessary to identify the best targets for the development of biomarker and therapeutic development for AD and related tauopathies.
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Sonnen, Andreas F. P., Jürgen M. Plitzko i Robert J. C. Gilbert. "Incomplete pneumolysin oligomers form membrane pores". Open Biology 4, nr 4 (kwiecień 2014): 140044. http://dx.doi.org/10.1098/rsob.140044.
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Pneumolysin is a member of the cholesterol-dependent cytolysin (CDC) family of pore-forming proteins that are produced as water-soluble monomers or dimers, bind to target membranes and oligomerize into large ring-shaped assemblies comprising approximately 40 subunits and approximately 30 nm across. This pre-pore assembly then refolds to punch a large hole in the lipid bilayer. However, in addition to forming large pores, pneumolysin and other CDCs form smaller lesions characterized by low electrical conductance. Owing to the observation of arc-like (rather than full-ring) oligomers by electron microscopy, it has been hypothesized that smaller oligomers explain smaller functional pores. To investigate whether this is the case, we performed cryo-electron tomography of pneumolysin oligomers on model lipid membranes. We then used sub-tomogram classification and averaging to determine representative membrane-bound low-resolution structures and identified pre-pores versus pores by the presence of membrane within the oligomeric curve. We found pre-pore and pore forms of both complete (ring) and incomplete (arc) oligomers and conclude that arc-shaped oligomeric assemblies of pneumolysin can form pores. As the CDCs are evolutionarily related to the membrane attack complex/perforin family of proteins, which also form variably sized pores, our findings are of relevance to that class of proteins as well.
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Center, Rob J., Richard D. Leapman, Jacob Lebowitz, Larry O. Arthur, Patricia L. Earl i Bernard Moss. "Oligomeric Structure of the Human Immunodeficiency Virus Type 1 Envelope Protein on the Virion Surface". Journal of Virology 76, nr 15 (1.08.2002): 7863–67. http://dx.doi.org/10.1128/jvi.76.15.7863-7867.2002.
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ABSTRACT The envelope protein (Env) of human immunodeficiency virus type 1 forms homo-oligomers in the endoplasmic reticulum. The oligomeric structure of Env is maintained after cleavage in a Golgi compartment and transport to the surfaces of infected cells, where incorporation into budding virions takes place. Here, we use biophysical techniques to assess the oligomeric valency of virion-associated Env prior to fusion activation. Virion-associated Env oligomers were stabilized by chemical cross-linking prior to detergent extraction and were purified by immunoaffinity chromatography. Gel filtration revealed a single predominant oligomeric species, and sedimentation equilibrium analysis-derived mass values indicated a trimeric structure. Determination of the masses of individual Env molecules by scanning transmission electron microscopy demonstrated that virion-associated Env was trimeric, and a triangular morphology was observed in 20 to 30% of the molecules. These results, which firmly establish the oligomeric structure of human immunodeficiency virus virion-associated Env, parallel those of our previous analysis of the simian immunodeficiency virus Env.
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Kvansakul, Marc, Ivan Poon, Amy Baxter, Fung Lay, Grant Mills, Christopher Adda, Jennifer Payne i in. "NaD1 forms oligomeric complexes with phosphatidylinositol to lyse cell membranes". Acta Crystallographica Section A Foundations and Advances 70, a1 (5.08.2014): C1049. http://dx.doi.org/10.1107/s2053273314089505.
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Cationic antimicrobial peptides (CAPs) are innate defense molecules produced by essentially all living species and represent a rich source of novel therapeutic molecules for the treatment of human diseases including cancer. Although several CAPs (mainly from amphibians and vertebrates) have been shown to exhibit direct toxicity against tumor cells, the underlying molecular mechanisms are not well understood. Nicotiana alata (ornamental tobacco) defensin 1, NaD1, is a Class II solanaceous plant defensin in the CAP family that exhibits antifungal activities. We have identified NaD1 as a potent molecule in killing mammalian tumour cells. Microscopy analyses have revealed that NaD1 induces cytolysis of tumor cells via the formation of large plasma membrane blebs. NaD1 was demonstrated to bind directly to phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2 or PIP2) resulting in disruption of cytoskeleton-membrane interactions and subsequent plasma membrane blebbing. To define the molecular basis of the interaction between NaD1 and PIP2, we determined the crystal structure of a NaD1:PIP2 complex. Strikingly, NaD1 forms a unique arch-shaped oligomer comprised of seven NaD1 dimers and 14 PIP2. The structure of the protein:lipid complex indicates that the presence of PIP2 is critical for oligomerisation of NaD1. Formation of NaD1:PIP2 oligomers was further confirmed by protein-protein crosslinking and transmission electron microscopy. Based on these data we propose that NaD1 is an innate pattern recognition molecule for PIP2 and forms a unique protein-lipid oligomeric complex that mediates permeabilisation of both microbes and tumour cells.
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Wojciechowska, Daria, Michał Taube, Karolina Rucińska, Joanna Maksim i Maciej Kozak. "Oligomerization of Human Cystatin C—An Amyloidogenic Protein: An Analysis of Small Oligomeric Subspecies". International Journal of Molecular Sciences 23, nr 21 (3.11.2022): 13441. http://dx.doi.org/10.3390/ijms232113441.
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Human cystatin C (HCC), an amyloidogenic protein, forms dimers and higher oligomers (trimers, tetramers and donut like large oligomers) via a domain-swapping mechanism. The aim of this study was the characterization of the HCC oligomeric states observed within the pH range from 2.2 to 10.0 and also in conditions promoting oligomerization. The HCC oligomeric forms obtained in different conditions were characterized using size exclusion chromatography, dynamic light scattering and small-angle X-ray scattering. The marked ability of HCC to form tetramers at low pH (2.3 or 3.0) and dimers at pH 4.0–5.0 was observed. HCC remains monomeric at pH levels above 6.0. Based on the SAXS data, the structure of the HCC tetramer was proposed. Changes in the environment (from acid to neutral) induced a breakdown of the HCC tetramers to dimers. The tetrameric forms of human cystatin C are formed by the association of the dimers without a domain-swapping mechanism. These observations were confirmed by their dissociation to dimers at pH 7.4.
Rozprawy doktorskie na temat "Oligomeric forms"
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Paumier, Adrien. "Evaluation du canal calcique TRPA1 comme cible thérapeutique potentielle dans la pathogénèse de la maladie d’Alzheimer TRPA1 channels promote astrocytic Ca2+ hyperactivity and synaptic dysfunction mediated by oligomeric forms of amyloid-β peptide". Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALV010.
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La maladie d'Alzheimer (MA) est une maladie neurodégénérative qui affecte progressivement les fonctions cognitives et la mémoire. Le cerveau des personnes atteintes de la MA est caractérisé par le dépôt extracellulaire d'amyloïde-β (Aβ), un peptide qui s'agrège au sein de structures appelées "plaques séniles". Cependant, il a été reconnu que les formes solubles oligomériques d’Aβ (Aβo) sont les formes du peptide qui déclenchent la pathologie. Elles sont impliquées dans des dysfonctionnements synaptiques qui sont considérés comme l'un des premiers événements de la MA. Des études récentes suggèrent que les astrocytes pourraient jouer un rôle majeur dans les dysfonctionnements synaptiques, mais leur implication dans les premiers stades de la MA reste peu documentée. En utilisant l'imagerie calcique, nous avons montré que l'application brève d’Aβo sur des tranches aiguës de cerveau de souris induit une hyperexcitabilité calcique astrocytaire dans l'hippocampe. Cette hyperexcitabilité est indépendante de l'activité neuronale et se produit dans les microdomaines des prolongements astrocytaires impliqués dans la formation des synapses tripartites. Dans la même échelle de temps, nous avons observé une hyperactivité au sein des neurones voisins, en utilisant des enregistrements par patch-clamp en configuration cellule entière. Cette hyperactivité dépend de la signalisation calcique dans le réseau astrocytaire. De manière intéressante, l'inhibition du canal calcique TRPA1, exprimé dans les astrocytes, bloque l'effet d’Aβo et restaure l'activité des astrocytes et des neurones à un niveau basal. Par ailleurs, l'inhibition chronique de TRPA1 dans le modèle de souris APP/PS1-21 de la MA bloque les perturbations neuronales et astrocytaires précliniques et prévient les troubles de l'apprentissage. En somme, ce travail de thèse suggère un rôle essentiel pour l'hyperexcitabilité précoce astrocytaire dans la pathogenèse de la MA, et souligne que TRPA1 est une cible thérapeutique prometteuse avec un effet neuroprotecteurAlzheimer’s disease (AD) is a neurodegenerative disorder that progressively affects cognitive functions and memory. AD brains are characterized with the extracellular deposition of amyloid-β (Aβ), a peptide that aggregates in structures named “senile plaques”. However, it has been recognized that oligomeric soluble forms of Aβ (Aβo) are the pathology-triggering form of the peptide. They are involved in synaptic dysfunctions which are thought to be one of the earliest events in AD. Recent studies suggest that astrocyte could play a major role in synaptic dysfunctions but their involvement in early stages of AD remained largely undefined. By using calcium imaging we showed that short term application of Aβo on mice acute brain slices induces astrocytic calcium hyperexcitability in the hippocampus. This hyperexcitability was independent of neuronal activity and occurred in the astrocyte processes microdomains involved in tripartite synapses formation. In the same time-scale, we observed hyperactivity in neighboring neurons, using whole-cell patch-clamp recordings, which depends on calcium signaling in astrocyte network. Strikingly, the inhibition of astrocytic calcium channel TRPA1 blocked the effect of Aβo and reversed both astrocyte and neuron activity toward physiological range. Interestingly, chronic inhibition of TRPA1 in APP/PS1-21 mouse model of AD, blocked both neuron and astrocyte dysfunctions at preclinical stages and prevented learning impairments. Overall, this thesis work suggests a critical role for early astrocyte hyperexcitability in pathogenesis of AD and highlights TRPA1 as an interesting therapeutic target with neuroprotective effect
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Jansen, Katja. "Dimere und Oligomere des Prion-Proteins als Modell für den Umwandlungsmechanismus von der zellulären Isoform des Prion-Proteins in die pathogene Form". [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=966041461.
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Bailleul, Serge. "Heterogeneite des recepteurs aux oestrogenes et a la progesterone dans les tumeurs mammaires humaines : relation avec l'hormonodependance". Caen, 1988. http://www.theses.fr/1988CAEN2026.
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Andrianarivelo, Andry. "Rôle des hétéromères formés par les récepteurs de la dopamine et du glutamate dans les adaptations à long terme induites par la cocaïne Unraveling the Functions of Endogenous Receptor Oligomers in the Brain Using Interfering Peptide: The Example of D1R/NMDAR Heteromers Modulation and functions of dopamine receptor heteromers in drugs of abuse-induced adaptations". Thesis, Sorbonne université, 2020. http://www.theses.fr/2020SORUS014.
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Les substances addictives détournent les apprentissages par la récompense en augmentant la dopamine (DA) dans le système mésolimbique, en particulier dans le striatum, où elle module durablement la transmission glutamatergique excitatrice et contribue à la mise en place d’altérations comportementales persistantes. L’intégration des signaux dopaminergique et glutamatergique au sein du striatum est réalisée par les neurones moyen épineux du striatum (MSN), qui forment deux populations majoritairement distinctes : les MSN de la « voie directe » exprimant les récepteurs D1 de la DA (D1R-MSN) et ceux de la « voie indirecte » qui expriment les récepteurs D2 de la DA (D2R-MSN). Une hypothèse qui prévaut à l’heure actuelle est que la libération de DA induite par les drogues active les D1R-MSN, ce qui promeut le renforcement, alors qu’elle inhibe les D2R-MSN, diminuant ainsi leurs fonctions « anti-renforcement ». Les travaux du laboratoire ont montré que l’interaction physique (i.e. hétéromérisation) entre le D1R et le récepteur NMDA (NMDAR) du glutamate était nécessaire à la facilitation de la transmission glutamatergique par la DA dans les D1R-MSN. À l'inverse, d'autres travaux ont montré que l'interaction D2R / NMDAR sous-tend l'effet inhibiteur de DA sur la signalisation NMDAR dans les D2R-MSN. Toutefois, la modulation et la fonction de ces hétéromères in vivo dans les réponses induites par la cocaïne sont encore inconnues. À l'aide du test de « proximity ligation assay », nous avons montré que la sensibilisation locomotrice induite par des expositions répétées à la cocaïne est associée à la formation d'hétéromères D1R/NMDAR dans le Noyau Accumbens (NAc) et le Striatum Dorsal, tandis que l'hétéromérisation D2R/GluN2B est majoritairement observée au sein du NAc. Pour identifier les rôles des hétéromères DAR / NMDAR dans les différentes phases des adaptations moléculaires, morphologiques et comportementales induites par la cocaïne in vivo, nous avons conçu une approche virale pour perturber les hétéromères DAR / NMDAR de manière contrôlée dans le temps grâce à un promoteur dépendant de la doxycycline. Nous avons constaté que la perturbation de l'interaction D1R / NMDAR dans le NAc bloque la mise en place des altérations synaptiques induites par la cocaïne dans les D1R-MSN ainsi que le développement de la sensibilisation locomotrice et de la préférence de lieu conditionné par la cocaïne (CPP). A l’inverse, le blocage de l'interaction D2R / NMDAR interfère avec le maintien de la sensibilisation psychomotrice et de la CPP à la cocaïne. L’observation d’un rôle préférentiel des hétéromères D2R/GluN2B dans la maintenance des réponses comportementales à la cocaïne et leur absence d’effet dans le cas d’une récompense naturelle suggèrent que ce sous-type d’hétéromère pourrait être une cible thérapeutique à envisager. J’ai donc mis au point la détection des complexes D2R / NMDAR à partir des tissus striataux humains post-mortem issus d’individus avec un historique de dépendance aux psychostimulants ou des sujets sains. Ceci m’a permis de montrer, qu’en dépit d’une forte baisse de l’expression du D2R, la proportion de D2R formant des hétéromères avec les NMDAR est trois fois supérieure chez les sujets dépendants par rapport au sujets sains. Ce travail renforce donc les évidences en faveur d’un rôle central des interactions entre les systèmes dopaminergique et glutamatergiques dans les réponses aux drogues et identifie les hétéromères DAR / NMDAR comme des cibles moléculaires avec un potentiel thérapeutique non seulement dans la dépendance aux drogues mais également pour les nombreux troubles psychiatriques associés à un déséquilibre entre les transmissions dopaminergiques et du glutamatergiquesAddictive substances hijack reward-dependent learning by increasing dopamine (DA) in the mesolimbic system, in particular in the striatum, where it modulates durably excitatory glutamatergic transmission and contributes to the establishment of persistent behavioral alterations. The integration of dopaminergic and glutamatergic signals within the striatum is achieved by the medium-size spiny neurons of the striatum (MSN), which form two mostly segregated populations: the MSN of the "direct pathway" expressing DA D1 receptors (D1R-MSN) and those of the "indirect pathway" which express the DA D2 receptors (D2R-MSN). A prevailing hypothesis is that the surge of DA evoked by drugs of abuse facilitates D1R-MSN activation through the stimulation of D1R, which promotes reinforcement, whereas the D2R-mediated inhibition of D2R-MSN prevent their so-called anti-reward action. Our laboratory has previously shown that the physical interaction (i.e. heteromerization) between D1R and the NMDA glutamate receptor (NMDAR) was necessary for the facilitation of glutamatergic transmission by DA in D1R-MSN. Conversely, others have shown that the D2R/NMDAR interaction underlies the inhibitory effect of DA on NMDAR signaling in D2R-MSN.However, the modulation and function of these heteromers in vivo in responses to cocaine are still unknown. Using the “proximity ligation assay” technique, we found that locomotor sensitization induced by repeated exposure to cocaine is associated with the formation of D1R/NMDAR heteromers in the Nucleus Accumbens (NAc) and the Dorsal Striatum, while the D2R/GluN2B heteromerization is mainly observed within the NAc. To identify the roles of the DAR/NMDAR heteromers in the different phases of the molecular, morphological and behavioral adaptations induced by cocaine in vivo, we designed a viral-based approach to disrupt the DAR/NMDAR heteromers in a controlled manner over time owing to a doxycycline-dependent promoter. We found that the disruption of the D1R/NMDAR interaction in the NAc blocks cocaine-evoked long-term synaptic plasticity in D1R-MSN and the development of both psychomotor sensitization and conditioned place preference (CPP). By contrast, blocking the D2R/NMDAR interaction interferes with the maintenance of cocaine psychomotor sensitization and CPP. The observation of a preferential involvement of the D2R/GluN2B heteromers in the maintenance of behavioral responses to cocaine and their lack of effect in natural reward suggests that this subtype of heteromers could be a promising therapeutic target. Based on this hypothesis, we developed the detection of D2R/NMDAR complexes from human post-mortem striatal tissues prepared from individuals with a history of psychostimulants dependence or healthy subjects. This allowed us to show that, despite a sharp decrease in D2R expression, the proportion of D2R forming heteromers with NMDAR is three-fold higher in addict subjects compared to healthy controls. This work therefore reinforces the evidence of the central role of interactions between the dopaminergic and glutamatergic systems in drug responses and identifies the DAR/NMDAR heteromers as molecular targets with therapeutic potential not only in addiction but also for the numerous psychiatric disorders associated with an imbalance between dopaminergic and glutamatergic transmissions
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Basu, Deblina. "Identification and Characterisation of a miRNA releasing activity from Caenorhabditis elegans". Thesis, 2019. https://etd.iisc.ac.in/handle/2005/4366.
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MicroRNAs (miRNA) are endogenous, small non coding RNAs, which play a prominent role in eukaryotic gene regulation. Perturbations leading to an altered abundance of miRNAs can lead to pathological conditions like neurological disorders, auto-immune diseases, and even cancer. Thus regulating the regulators is of utmost importance. While miRNA biogenesis is well delineated pathway, currently sparse information is available about active miRNA turnover. A mature miRNA is thought to be formed within the pre-miRISC (RNA induced silencing complex), where one of the strands, miRNA/ guide strand from the miRNA: miRNA*/ guide: passenger strand duplex, is preferentially selected and loaded onto the Argonaute (AGO). This miRNA acts as an ‘address label’, and guides the miRISC to cognate mRNA targets, and repress their expression.
Researchers while purifying human siRISC have found that the small RNA remains very strongly bound by AGO, even under highly stringent conditions applied during the purification. The notion got strengthened when the crystal structure of Thermus thermophilus AGO bound to a 5’ phosphorylated guide DNA revealed that AGO has a bi-lobed structure comprising of four domains (N, PAZ, MID, and PIWI), where except the nucleotides in the seed region (2nd-8th nucleotide from the 5’ end), the entire guide sequence remains buried inside a channel. The co-crystal structure also showed that the 5’ nucleotide of the guide sequence remains anchored at the basic pocket of the MID domain, and 3’ end is bound by the PAZ domain. Later, co-crystal structures of human Ago2 with endogenous RNA, and that of yeast AGO with guide RNA, revealed that multiple general and specific contacts exist between the residues of AGO and the guide sequence. This endorsed the earlier notion that only seed sequence of the guide strand remains free for interaction with cognate targets through antisense mechanism. Together all these findings contributed to the notion that miRISC (as well as siRISC) is a super-stable structure, and the guide sequence remains inaccessible to the nucleases in the cell. Hence, miRNAs might undergo passive degradation with host AGO protein.
Interestingly, this notion got upturned, when researchers working with Caenorhabditis elegans (C. elegans) demonstrated through explicit biochemical assays that miRNAs do get released from AGO, before they undergo degradation by bona fide miRNase (XRN-2), without affecting the integrity of the AGO protein. The researchers also showed that XRN-2 depleted worm lysate exhibits compromised miRNA release activity. This could possibly be because of a direct role of XRN-2 in miRNA release. Conversely, XRN-2 might function downstream of a dedicated miRNA release factor, and in XRN-2 depleted state, as the release and turnover kinetics are inter-linked, the overall miRNA release activity got diminished. However, the identity of this endogenous, and dedicated ‘miRNA release factor’ has remained elusive, so far.
Here, we report, that a small 26 kDa pur-alpha family protein (PLP-1) is responsible for release of a subset of miRNAs from miRNA AGO of C. elegans, without affecting the integrity of AGO. The protein is not only capable of freeing the miRNA from the grasp of AGO, but can also bind, and deliver it to a defined component of miRNA turnover machinery (miRNasome-1). We have also found that this protein can oligomerize, and that binding of specific miRNAs can induce unique pattern of oligomerization of the protein (by enhancing specific oligomeric forms over others). This work unfurls the potential of a single protein to perform multiple functions through its different oligomeric forms, and connect miRISC/AGO to a miRNA turnover complex (miRNAsome-1) in a two-step miRNA turnover pathway.
The Chapter 1 forms the Introduction to the thesis, and presents extensive literature survey on topics pertaining to the current work. The chapter begins with a brief history of non-coding RNAs, miRNAs in particular. Next, an account of the different small non-coding RNAs is presented. This is followed by a description of the well-delineated miRNA biogenesis pathway, with special emphasis on RISC (RNA induced silencing complex) and AGO proteins, the core of RISC. Next, a short summary on RNAi is documented. Further, an account of miRNA functions in general, miRNA stability, and active miRNA turnover is presented chronologically. Thereafter, a brief description of the model organism C. elegans, used for the current study is presented.
The Chapter 2 constitutes the first data chapter titled ‘Identification of a miRNA releasing activity in Caenorhabditis elegans.’ This chapter embodies the primary working hypothesis, and establishes the platform for the identification of the miRNA release factor. Here an account of the step-wise fractionation of C. elegans total lysate, yielding a fraction enriched in miRNA release activity is presented. After subsequent biochemical assays with the enriched fraction, mass spectrometric analysis is carried out, which reveals Pur alpha like protein-1 (PLP-1), as a putative miRNA release factor. Using recombinant PLP-1 in in vitro assays, the protein is validated as the miRNA release factor, which can dislodge the miRNA from the grasp of AGO/ miRISC, in C. elegans. Further, a probable role of the paralogous protein PLP-2 from C. elegans in miRNA binding and release, is studied and discussed.
The Chapter 3 titled ‘in vivo effects upon plp-1 knockdown in C. elegans’ follows the PLP-1 identification chapter. In this section, the consequent in vivo effects upon plp-1 knockdown is depicted. Effects on worms, both phenotypic and developmental are accounted for briefly. Next, effect on endogenous miRNAs (precursor and mature forms), and their cognate targets is assessed. This is followed by illustrating effects on other major players of miRNA metabolism namely miRNA AGO, and miRNases: XRN-1 and XRN-2, in PLP-1 depleted condition.
The Chapter 4 titled ‘Functional characterization of PLP-1’, encompasses the brunt of the work, where through in vitro assays, three major functional aspects of the protein PLP-1: miRNA binding, miRNA release, and delivery of miRNA to bona fide miRNA turnover machinery, are elucidated. While demonstrating the miRNA binding property of the protein, an intriguing observation led to the revelation that the protein possess an exceptional oligomerization property. Together with biochemical assays and mutational studies, the importance of the different regions and residues of the protein, for individual functions is depicted. This chapter ends with summarising the independence or inter-dependence of the different functionalities of the protein.
The thesis is concluded with a combined Discussion and Future Perspective section. This section gives a holistic picture of the work with respect to the existing knowledge on miRNA metabolism, and how the current study enhances our understanding of this process leading to the next level of perception.
The following chapter contains the Materials and Methods, used in the present study. In this chapter, a comprehensive description of all the methodologies employed in the experiments is provided. References for already established methodologies are indicated and incorporated.
As an addendum Appendix is included where detailed information on the different clones used in the study is provided. Also, figures corresponding to some of the data not shown in the previous version of the thesis is incorporated in this section. Finally, the closure is done with the Bibliography section.UGC
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Pisterzi, Luca Francis. "Pairing Form with Function: The Oligomeric Size and Configuration of G Protein-coupled Receptors". Thesis, 2012. http://hdl.handle.net/1807/65486.
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The quaternary status of G protein-coupled receptors (GPCRs) is important, unknown and
controversial. Estimates of size from numerous pharmacological, biochemical and biophysical
studies range from monomers to octamers. Accounts of stability vary from constitutive oligomers
to a spontaneous, ligand-regulated interconversion between monomers and dimers. In the present
investigation, the oligomeric size of GPCRs in live Chinese hamster ovary (CHO) cells has been
examined by two methods. Both are based on the efficiency of Förster resonance energy transfer
(FRET) between fluorophore-tagged receptors, as determined from emission spectra via spectral
deconvolution. In the first, the apparent FRET efficiency (Eapp) was measured for cells expressing
eGFP- and eYFP-tagged M2 muscarinic receptors at different ratios of acceptor to donor. Eapp then
was related to the pair-wise efficiency (Ep) according to a model that enumerates all pathways for
the transfer of energy between single donors and acceptors within an oligomer of given size (n).
Each value n returned a distinct and well-defined value of Ep. Fluorescence lifetime imaging
provided an independent estimate of Ep that was in close agreement with the model-based value
when n = 4, identifying the M2 receptor as a tetramer. In the second approach, the M1 and M2
muscarinic receptors and the β1 and β2 adrenergic receptors were tagged with GFP2 and eYFP, and
the value of Eapp was estimated for each pixel in the image of a cell. The distributions of Eapp from
34–40 cells expressing each receptor were compared with those predicted for populations of dimers,
trimers and tetramers, the latter configured as a square and a rhombus. In each case, the combined
data were well described in terms of a rhombus. Distributions obtained for the M2 and β2 receptors
were not affected by agonists or inverse agonists, nor was there evidence for appreciable numbers
of dimers or larger oligomers. Taken together, the results suggest that GPCRs of Family 1 exist
largely or wholly as constitutive tetramers.
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El-Huneidi, Waseem. "Functional Characterization of Arcanobacterium pyogenes Pyolysin in an Oligomeric Form, and the Binding of CAMP Factor to IgG". Thesis, 2007. http://hdl.handle.net/10012/3432.
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The work described in this thesis deals with two pore forming toxins, namely Arcanobacterium pyogenes pyolysin and Streptococcus agalactiae CAMP factor. Pyolysin (PLO) belongs to the homologous group of cholesterol-dependent cytolysins. In chapter 2, it is shown that PLO can form small oligomers in solution, without the requirement for any membranes or membrane lipids. These small oligomers may aggregate into larger ones on membranes; however, in solution, they apparently do not grow by addition of further monomers, as their size is virtually unaffected by variations of incubation time or toxin concentration. The small, solution-derived oligomers retain hemolytic activity. The membrane lesions observed by electron microscopy are similar to those that are formed by monomeric PLO, except that they are mostly incomplete and arc-shaped, as opposed to the predominantly ring-shaped ones formed by monomeric PLO when directly incubated with membranes. This structural difference corresponds to a detectable difference in functional pore size, as determined by marker release experiments. Thus, arc-shaped PLO oligomers may form functional pores of reduced size. In chapter 3, we show that liposomes that contain phosphatidylcholine and ceramide but no cholesterol or other sterol are susceptible to the cholesterol-dependent cytolysin pyolysin. Pyolysin, at a low rate, forms small oligomers in solution. The solution-derived oligomers are more effective on ceramide-containing liposomes than the monomeric toxin. In contrast, they have much lower activity on liposome membranes that contain cholesterol but no ceramide. Our findings therefore show that at least one member of the ‘cholesterol-dependent cytolysins’ is in fact not strictly dependent on the sterol. In addition, in conjunction with previous data, they suggest that the requirement for cholesterol involves early or intermediate stages of oligomer formation, rather than the final event of membrane insertion. Chapter 4 of this thesis concerns Streptococcus agalactiae CAMP factor. CAMP factor has previously been reported to bind the Fc fragments of immunoglobulin G (IgG) and has therefore also been called ‘protein B’, in analogy to protein A of Staphylococcus aureus. We attempted to characterize the interaction of protein B with IgG in more detail. In contrast to protein A, CAMP factor does not inhibit the activation of complement by hemolysin antibodies bound to sheep red cell surfaces. IgG also failed to inhibit the cohemolytic activity of CAMP factor, which it displays on sphingomyelinase-treated sheep red cells; this is in disagreement with previous findings. After co-incubation, CAMP factor and IgG were cleanly separated by gel filtration. Therefore, CAMP factor does not detectably bind to IgG.
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Jansen, Katja [Verfasser]. "Dimere und Oligomere des Prion-Proteins als Modell für den Umwandlungsmechanismus von der zellulären Isoform des Prion-Proteins in die pathogene Form / vorgelegt von Katja Jansen". 2002. http://d-nb.info/966041461/34.
Pełny tekst źródłaKsiążki na temat "Oligomeric forms"
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Nakamura, Tomohiro, i Stuart A. Lipton. Neurodegenerative Diseases as Protein Misfolding Disorders. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780190233563.003.0002.
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Neurodegenerative diseases (NDDs) often represent disorders of protein folding. Rather than large aggregates, recent evidence suggests that soluble oligomers of misfolded proteins are the most neurotoxic species. Emerging evidence points to small, soluble oligomers of misfolded proteins as the cause of synaptic dysfunction and loss, the major pathological correlate to disease progression in many NDDs including Alzheimer’s disease. The protein quality control machinery of the cell, which includes molecular chaperones as found in the endoplasmic reticulum (ER), the ubiquitin-proteasome system (UPS), and various forms of autophagy, can counterbalance the accumulation of misfolded proteins to some extent. Their ability to eliminate the neurotoxic effects of misfolded proteins, however, declines with age. A plausible explanation for the age-dependent deterioration of the quality control machinery involves compromise of these systems by excessive generation of reactive oxygen species (ROS), such as superoxide anion (O2-), and reactive nitrogen species (RNS), such as nitric oxide (NO). The resulting redox stress contributes to the accumulation of misfolded proteins. Here, we focus on aberrantly increased generation of NO-related species since this process appears to accelerate the manifestation of key neuropathological features, including protein misfolding. We review the chemical mechanisms of posttranslational modification by RNS such as protein S-nitrosylation of critical cysteine thiol groups and nitration of tyrosine residues, showing how they contribute to the pathogenesis of NDDs.
Części książek na temat "Oligomeric forms"
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Klyachko, N. L., P. A. Levashov, A. V. Levashov i C. Balny. "Pressure Activates Oligomeric Enzymes in Reversed Micelles by Stabilisation of Different Oligomeric Forms". W Advances in High Pressure Bioscience and Biotechnology, 283–86. Berlin, Heidelberg: Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/978-3-642-60196-5_63.
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Georgakopoulos, John, i Joan Argyroudi-Akoyunoglou. "Thylakoid Protein Phosphorylation Leads to Organization of the Oligomeric Forms of Pigment-Protein Complexes in Pea Grana and Stroma Lamellae". W Regulation of Chloroplast Biogenesis, 539–44. Boston, MA: Springer US, 1992. http://dx.doi.org/10.1007/978-1-4615-3366-5_78.
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Geldof, D., A. Krishtal, F. Blockhuys i C. Van Alsenoy. "Quantum chemical study of self-doping PPV oligomers: spin distribution of the radical forms". W Highlights in Theoretical Chemistry, 87–93. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-41315-5_8.
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Fradin, Cécile, Dmitri Satsoura i David W. Andrews. "Punching Holes in Membranes: How Oligomeric Pore-Forming Proteins and Lipids Cooperate to Form Aqueous Channels in Membranes". W Biomembrane Frontiers, 223–62. Totowa, NJ: Humana Press, 2009. http://dx.doi.org/10.1007/978-1-60761-314-5_9.
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Soteriadou, Ketty Ph, Athina K. Tzinia, Maria G. Hadziantoniou i Socrates J. Tzartos. "Surface Antigens of Leishmania Infantum Identified by Monoclonal Antibodies: Isolation of a Monomeric and an Oligomeric form of a Major L. Infantum Antigen". W Leishmaniasis, 603–10. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4613-1575-9_74.
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Dutruch, L., M. Senneron, M. Bartholin, P. Mison i B. Sillion. "Preparation of Thermostable Rigid Foams by Control of the Reverse Diels—Alder Reaction During the Cross-Linking of Bis-nadimide Oligomers". W ACS Symposium Series, 37–53. Washington, DC: American Chemical Society, 1997. http://dx.doi.org/10.1021/bk-1997-0669.ch004.
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Jaing, James T., Beth A. Welty, Daryl T. Morishige i J. Philip Thornber. "Assembly of the Photosystem I Multiprotein Complex and the Oligomeric Form of the Major Light-Harvesting Chlorophyll a/b-Protein in Pea Seedlings Grown in Flashed Light Followed by Continuous Illumination". W Regulation of Chloroplast Biogenesis, 291–301. Boston, MA: Springer US, 1992. http://dx.doi.org/10.1007/978-1-4615-3366-5_42.
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Garnier, Jacques, Benrui Wu, Jeannine Maroc, Denise Guyon i Antoine Tremolieres. "Restoration of an Oligomeric Form of the Light-Harvesting Antenna CP II and of a Fluorescence State II-State I Transition by Δ3-Trans-Hexadecenoic Acid-Containing Phosphatidylglycerol, in a Mutant of Chlamydomonas". W Current Research in Photosynthesis, 1237–40. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-0511-5_286.
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Shevchenko, Valery V., Alexandr V. Stryutsky, Mariana A. Gumenna, Nina S. Klimenko i Valeri V. Klepko. "Synthesis, structure and properties of oligomeric ionic liquids of highly branched structure and special features of their self-arrangement". W NEW FUNCTIONAL SUBSTANCES AND MATERIALS FOR CHEMICAL ENGINEERING, 199–209. PH “Akademperiodyka”, 2021. http://dx.doi.org/10.15407/akademperiodyka.444.199.
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Synthesis, features of structural organization and behavior in aqueous solution of amphiphilic reactive aprotic cationic oligomeric ionic liquids obtained on the basis of a mixture of oligomeric amino- and hydroxyl-containing silsesquioxanes were considered. The dependence of the glass transition temperature, the value of ionic conductivity, self-organization in dilute aqueous solutions and the ζ-potential on the length of the alkyl substituent near the quaternary nitrogen atom in the composition of the synthesized compounds was shown. It was found that quaternization of the tertiary nitrogen atom of the starting oligomer causes a sharp decrease in the glass transition temperature. The value of the latter increases with an increase in the length of the hydrophobic alkyl fragments due to their association. In this case the ionic conductivity under anhydrous conditions decreases and at temperatures above 100°C drops by almost an order of magnitude. The maximum conductivity was reached for the oligomeric ionic liquid with the short alkyl chain and its value was 10-3 S/cm at 120oC. In dilute aqueous solutions the synthesized oligomeric ionic liquids with the short alkyl chain form aggregates with an average size of 100 nm while increasing the length of the alkyl chain prevents aggregation of silsesquioxane nuclei and leads to formation of unimolecular micelles with an average size of 3 nm
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Wemmer, D. "Design and Characterization of New Sequence Specific DNA Ligands". W Biological NMR Spectroscopy. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195094688.003.0026.
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During the early 1980s there were two developments which lead to our studies of sequence specific DNA ligands. The first was the development of sequential assignment methods based on 2D NMR spectra which allowed complete assignment of resonances for proteins (Wüthrich, 1986). The assignments in turn allowed determination of many structural restraints through interpretation of NOESY crosspeaks and coupling constants from COSY type spectra. The second advance was the improvement of the chemistry for direct synthesis of DNA oligomers. With multimilligram samples of DNA oligomers available sequential assignment methods for DNA, paralleling those for proteins, were also worked out. Again with assignments came the possibility of determining DNA structures in solution. Howeverfor double stranded, Watson-Crick paired DNAs the structure can be reasonably approximated by the standard B-form model derived from fiber diffraction. The accurate determination of local conformational features has been somewhat difficult using NMR since tertiary contacts (as are so valuable in determining protein structures) do not occur. However with careful quantitative analysis some of the local details of structure can be determined. These NMR methods also offered the possibility of trying to understand the structural basis for binding of ligands to DNA oligomers. In order to make welldefined complexes we wanted to start with a compound that showed some sequence specificity in binding, and selected distamycin (shown below), a polypyrrole antibiotic which was known to have preference for binding to A-T rich DNA sequences. A close relative, netropsin, had been studied by Dinshaw Patel who showed that the binding is in the minor groove by identifying an NOE between a proton of the ligand and an adenosine H2 in the center of the minor groove (Patel, 1982). We began by making a complex with the self-complementary DNA oligomer: 5'-CGCGAATTCGCG-3', which had been studied extensively by X-- ray crystallography, and also by NMR. Distamycin did form a well-defined complex with this DNA, which was is slow exchange with free DNA during titrations (Klevit et al., 1986).
Streszczenia konferencji na temat "Oligomeric forms"
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Arroyo, Raquel, Mercedes Echaide, Emma Batllori, Alberto Galindo, Fernando Moreno-Herrero, Jesús Pérez-Gil i Paul S. Kingma. "Characterization of the activity of the different oligomeric forms of pulmonary human surfactant protein SP-D". W ERS International Congress 2019 abstracts. European Respiratory Society, 2019. http://dx.doi.org/10.1183/13993003.congress-2019.pa2382.
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Grøn, B., i F. Brosstad. "IMMUNO-VISUALIZATION OF FIBRINOGEN AND FIBRIN IN GELS PRDUCED BY GELATION OF PLASMA WITH ETHANOL". W XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643326.
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The Ethanol Gelation Test(=EGT) is a well-documented simple,specific and frequently used test to detect plasma soluble fibrin(Godal & Abildgaard:Gelation of soluble fibrin in plasma by ethanol.Scand.J.Haanat.3,342,1966) .If soluble fibrin present in plasma amounts to 1% or more of the plasma-f ibrinogen conc.,the admixing of 0.15 ml 50% ethanol to 0.5 ml plasma in a test tube will-(subsequent to incubation for 10 min at 20°C)-upon tilting the test tube semi-horizontally produce a characteristic,(upwardly) convex gel. Although earlier studies have confirmed the validity and specificity of EGT as a means to detect soluble fibrin,we found it of interest to see to which degree such soluble fibrin is FXIII-stabilized EGT-positive(from patients with Disseminated Intravascular Coagula-tion(DIC) and EGT-negative plasma was studied as follows: The EGT test was performed as above,and the entire content of the test tube emptied upon a nylon micro-meshed membrane.Applying slight suction underneath the nylon manbrane the fluid was removed,leaving the ethanol precipitated material which was immediately dissolved in SDS (1%)-urea(5M)-Tris-HCl (0.15M,pH8.6). After incubation at 100°C for 1 min the material was SDS-electrophoresed on flat-bed agarose(2%) Subsequent to Western-blotting onto nitrocellulose and gelatine-blocking, the fibrin(ogen)-related pattern was reacted with either: a)polyclonal antibodies to fibrinogen,b)plyclonal antibodies to FPA or c)monoclonal antibody to FPA(gift from Dr.Nieuwenhuizen, Leyden, Holland) .Then,the fibrin(ogen)related pattern was developed using peroxidase-conjugated secondary antibodies.From the specificity of the primary antibodies used,it could be deduced that:1)A substantial amount of the soluble fibrin content of DIC-plasma was present in an oligomeric form(up to 6-mers) .2)These oligomers contained fibrinogen, i.e. thus representing FXIII-1 inked fibrinogen/fibrin hybride molecules .3) Even normal plasma contained some detectable oli-gomers(up to 3-mers) .4) Col lecting blood with all appropriate thrombin- and FXIII-inhibitors did not change the patterns obtained and described above.It may be concluded that soluble fibrin occurs mainly in a FXIII-stabilized,oligomeric form which contains fibrinogen Due to the nature of the polymerization process,the fibrinogen moiety of these hybride molecules must be end-located representing a physiological means to inhibit further polymer growth.
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Savikhir, S., Y. Zhu, S. Lin, R. E. Blankenship i W. S. Struve. "Femtosecond energy transfer and coherent oscillations in BChl c light-harvesting antennae of chlorosomes from the green photosynthetic bacterium Chloroflexus aurantiacus". W International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/up.1994.tub.3.
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Chlorosomes are the principal light-harvesting bodies in green photosynthetic bacteria. These 100×30×12 nm ellipsoidal bodies contain ~104 bacteriochlorophyll (BChl) c chromophores, as well as a BChl a pigment-protein complex that forms an interfacial baseplate between the chlorosome and the cytoplasmic membrane. The BChl c pigments in chlorosomes are organized into large oligomers, whose electronic and vibrational spectroscopy is remarkably similar to that of BChl c aggregates that form spontaneously from BChl c monomers in solution. This unique self-aggregating property has attracted wide attention because of its potential applications in artificial photosynthesis. The BChl c and BChl a antennae of chlorosomes from the green bacterium Chloroflexus aurantiacus exhibit broad Qy (S1←S0) electronic absorption bands centered at ~740 and ~790 nm, respectively. Downhill BChl c → BChl a energy transfer occurs with ~10 ps kinetics in isolated chlorosomes [1,2]. In this work, we have focussed on the femtosecond internal energy transfer events within the BChl c antenna. It is currently believed [3] that this 740 nm antenna comprises several distinct BChl c spectral forms (c727, c744, c766 etc.) Equilibration among chlorophyll and bacteriochlorophyll spectral forms requires several hundred fs in most pigment-protein antenna complexes that have been studied to date [4].
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Ide, J. P., D. R. Klug, W. Kuhlbrandt i G. Porter. "Detergent effects upon the picosecond dynamics of higher plant light harvesting chlorophyll complex (LHC)." W International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/up.1986.mf1.
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The light-harvesting chlorophyll a/b protein complex (LHC) has been shown to form crystalline arrays in vitro. These arrays have P321 symmetry. The unit cell is composed of trimeric protein oligomers arranged with a 3-fold symmetry axis running centrally through each complex[1]. Each polypeptide has an apparent molecular weight of 25–27kd within which are bound 6-11 chlorophyll molecules.
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Hunziker, E. B., P. W. Straub i A. Haeberli. "AN INTERLOCKING SINGLE-STRAND MODEL FOR FIBRIN POLYMERIZATION." W XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643315.
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The early stages of fibrin polymerization were investigated by rotatory shadowing and electron microscopy. Individual molecules within initial oligomers were found to be unaligned and contacted neighbouring molecules by single E + D and D + E contacts, suggesting an intermediate phase of activation (des A-fibrin). The interacting molecular domains were separated by a distance of 2 to 3 nm, indicating that (both or at least one) binding sites are located on protruding segments of the polypeptide chains. Upon completion of fibrin activation (des AA-fibrin), molecules within the early oligomers aligned to form single-stranded polymers,o these being characterized by repeating trinodular units of 230 A in length. Based upon these findings, a new interlocking single-stranded model for fibrin polymerization was designed and tested. The model is consistent with previous experimental data on fibrin polymerization such as that obtained by X-ray diffraction and negative staining. Moreover, early branching and lateral association phenomena are easily explained.
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Garcia Frade, L. J., L. Landin, A. Garcia Avello, J. L. Bavarro, L. J. Creighton i P. J. Gaffney. "FIBRIIOLYTIC ACTIVITY II THE IITBISIVE CARE PATIEIT". W XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644885.
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Critically ill patients have been described to have blood coagulation abnormalities that predispose to bleeding and thrombosis.We have studied plasminogen activators (fibrin plate, enzyme-linked Immunosorbent assay using polyclonalantibodies for t-PA), X-oligomers fibrin fragments (using monoclonal antibodies in an enzyme-linked immunosorbent assay), octant i pi asmin, antithrombtai III and fibronectin (Laurel1 innaunoeleetrophoretic technique), fibrinogen (thrombin timeassay), plateLets count, kaolln-cephalin clotting time and prothrombin time on admission to the intensive care unit and sequentially after 24 and 48 hours in 39 adult patients: Adult respiratory distress syndrome (ARDS) (n:6), Trauma (n:12), Sepsis (n:8), and Miscellanea (n:13).A decrease in tissue plasminogen activator (ng/ml)(p<0.001, p<0.05, p<0.01, p<0.05, respectively in the four groups), associated to an increase in the earliest form of cross-linked fibrin degradation products, X-Oligomers concentration (ng/ml) (p<0.01), indicatethat fibrindeposition and fibrinolytic exhaustion is a widespread situation in the ICU patients. Fibronectin was significantly reduced (p<0.001) in ARDS and Sepsis patients, low fibronectin levels were related to prognosis (p<0.01).These findings suggest.that critically ill patients, must be evaluated in respect to fibrinolysis and supported when necessary with prophylactic treatment.
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Shimizu, Tsuyoshi, i Hiroshi Tani. "Behavior of Chemical Reaction Between Siloxane Compounds and Surface on Carbon Materials". W ASME 2017 Conference on Information Storage and Processing Systems collocated with the ASME 2017 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/isps2017-5424.
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Among many organic vapor contaminations released from structural components of hard disk drives, organic sioloxanes are particularly ominous, as they can be released in a relatively large quantity. Adherence of organic pollutants to the disk surface is a factor that hinders the normal operation of the head and the disk surface. It is known that volatile siloxane oligomers such as D4 (octamethyl cycletetrasiloxane) often form cyclic polydimethylsiloxane polymers in the presence of acidic catalysts. We investigated the reaction between D4 and some carbon materials such as diamond-like carbon in hard disk and graphite. The effect of the protection of carbon materials by Perfluoropolyether (PFPE) lubricants was observed.
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Rak, K., J. Harsfalvi, M. Udavardy, I. Tornai, M. Misz i Z. Boda. "ALTERATION OF PRIMARY HAEMOSTASIS IN PATIENTS WITH ATHEROSCLEROSIS: ITS POSSIBLE ROLE IN ATHEROGENESIS". W XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643082.
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Complex study was performed in order to evaluate the primary haemostasis of patients with generalized atherosclerosis. Signs referring to hypercoagulability and platelet activation are known from previous studies. The purpose of this work was to investigate the primary haemostasis in every detail. Assays were performed in 20 atherosclerotic patients and 10 control persons. Methods: platelet count, Ivy bleeding time (Simplate II), platelet retention (Adeplat T), in vivo platelet consumption (Borchgrevink), study of vWFAg by Laurell’s rocket and crossed immunoelectrophoresis (using Clottimmun-AHG Assoc. Protein, Behring), plasma B-TG (Amersham), the stable metabolites of TXA2 (TXB2) and PGI2 (6-KPGF) by RIA-kits. Results: platelet counts and bleeding times were not different, in vivo platelet consumption was also similar, but platelet retention proved to be increased in patients (40 vs 27 %). Increase of vWFAg level characterized atherosclerotic patients (277±83 vs 102±28 %); the relative mobility (RM) ratio which indicates the migration distance of vWFAG in CIE was significanty altered (0.33 compared to 0.26) meaning that the molecular forms of protein with faster mobility were increased to a greater degree than forms with slow mobility. B-TG plasmatic level was increased in patients (115 vs 28 ng/ml), the quotient of TXB2 and 6-KPGF was much bigger (4.7 vs 0.4). In conclusion: the most striking change was the elevation of plasmatic vWFAg level together with its structural alteration, i.e. predominance of the smaller oligomers. Primary haemostasis seems to be more active than normal, atherosclerosis represents a hyperadhesive and/or prethrombotic state. Although all the findings may be the result of vessel wall lesions, the observed changes may also have a causal role in the progression and complications of atherosclerosis.
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Shibatay, N., K. Tanaka, K. Okamoto i T. Onji. "REORGANIZATION OF ACTIN AND MYOSIN IN THE ACTIVATED PLATELETS". W XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643539.
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This study was done to clarify the intracellular dynamic arrangements of myosin(My) and actin(Ac) in activation process of human platelets (PLs) from unactivated to activated stage (clot retraction) in electron microscopy. The observation of unactivated PLs was done either in the fresh whole blood fixed directly with 0.1 % glutaraldehyde or in PLs isolated by gel filtration of platelet rich plasma(PRP) containing prostaglandin I2 (10 ng/ml). The isolated PLs mounted on a glass cover slip were used as activated PLs (adrerent ones). The contracted PLs were prepared in PRP incubated with thrombin (0.5 u/ml) and 20 mM CaCl- for 10-60 min. Treating PLs with 0.15 % Triton X-100 containing 0.05 % glutaraldehyde produced cytoskeleton. My and F-Ac were identified by an indirect immuno-cytochemical method using the specific antibody (rabbit IgG) against PL-My and protein A-gold and by demonstration of in “arrow-head” decoration by Ishikawa's method using skeletal meromyosin (HMM), respectively. [Results] (1) Unactivated PLs. Mys in monomer or oligomer distributed homogenously in scare association with cytoskeleton. Cytoskeletons were exclusively composed of F-Ac networks of crossolinked short filaments which were thinly distributed in the cytoplasm with partial connection to the cell membrance. (2) Surface activated spreading PLs. PLs adhered to the glass cover slip in dendritic forms. Mys were densely located around granulomere and formed linear arrays associated with F-Ac filaments of the cytoskeleton surrounding the granulomere and running straightly in cytoplasm. (3) Contracted PLs. Activated PLs protruded several filopodia in which networks or bundles of F-Ac filaments were found connecting to extracellular fibrin strand through cell membrene. Microfilaments formed arrow-head decoration with HMM pointing toward the cell body. The cytoskeleton in contracted PLs contained thick filaments of My-polymers attaching to F-Ac filaments end by end. It is concluded that the reorganization of Ac-My is the basis for the shape change, secretion and clot retraction of activated PLs.
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Cavalcanti, Maria Isabel dos Santos, Débora Brígida Moura de Freitas, Dijanah Cota Machado i Cláudio Gabriel Rodrigues. "ANÁLISE COMPUTACIONAL DA INTERAÇÃO ENTRE O CANAL IÔNICO DE α-HL E COMPOSTOS TIAZOLIDÍNICOS". W XXVII Semana de Biomedicina Inovação e Ciência. Editora IME, 2021. http://dx.doi.org/10.51161/9786588884119/13.
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Introdução: Staphylococcus aureus (S. aureus) é uma bactéria associada a diversas infecções, tanto na comunidade quanto em ambiente hospitalar, ocasionando desde infecção cutânea até septicemia(1). Um importante fator de virulência é a exotoxina alfa-hemolisina (α-HL), que oligomeriza e forma canais iônicos transmembranares nas células-alvo, permitindo o fluxo livre de várias espécies químicas, resultando na morte celular(2). Diversas cepas de S. aureus exibem multirresistência aos antibióticos, limitando as opções de tratamento. Os derivados tiazolidínicos podem ser uma boa alternativa para bloquear a α-HL, pois possuem amplas propriedades bioativas, como por exemplo a antimicrobiana para cepas multirresistentes, sendo eficazes contra o S. aureus e inibindo o seu crescimento(3). Objetivos: Dada a importância da busca de compostos com ação antibacteriana, via bloqueio da α-HL, este trabalho visa analisar, via docagem molecular, a interação de derivados tiazolidínicos 5-benzilideno com o canal iônico formado pela toxina. Métodos: A estrutura cristalográfica da α-HL de S. aureus foi obtida pelo Protein Data Bank (PDB) e utilizou-se o MolView para modelagem dos compostos denominados GQ294 e GQ443, posteriormente submetidos ao Avogadro 1.1.1 para minimização de energia molecular. A docagem foi realizada pelo DockThor e os resultados foram analisados utilizando o Discovery Studio Visualizer. Resultados: A partir dos resultados de docagem pelo DockThor, foi obtida uma classificação dos compostos de acordo com suas energias totais e scores de afinidade com a toxina. Os valores de energia total do GQ443 e GQ294 foram iguais a -15,152 KJ/ mol e -19,009 KJ/ mol, respectivamente. Enquanto o score de afinidade de GQ443 e GQ294 foi de -6,820 Kcal/ mol e -5,902 Kcal/ mol respectivamente. As análises obtidas a partir do Discovery Studio Visualizer demonstraram que os dois compostos interagem com a região de constrição do canal iônico, principalmente com os resíduos GLU 111 e LYS 147, sendo estas interações mediadas principalmente por ligações de hidrogênio, além de interações do tipo cátionpi, pi-alquila, pi-enxofre. Esses dados corroboram com outros trabalhos já encontrados na literatura(4). Conclusões: Os resultados indicam, preditivamente, que os compostos GQ443 e GQ294 interagem com o canal da α-HL na região de constrição, sugerindo um bloqueio de sua atividade. São necessários dados experimentais para elucidar os dados teóricos já obtidos.