Borrelia burgdorferi OspC is an outer membrane lipoprotein required for the establishment of infection in mammals. Due to its universal distribution among B. burgdorferi sensu lato strains and high antigenicity, it is being explored for the development of a next-generation Lyme disease vaccine. An understanding of the surface presentation of OspC will facilitate efforts to maximize its potential as a vaccine candidate. OspC forms homodimers at the cell surface, and it has been hypothesized that it may also form oligomeric arrays. Here, we employ site-directed mutagenesis to test the hypothesis that interdimeric disulfide bonds at cysteine 130 (C130) mediate oligomerization. B. burgdorferi B31 ospC was replaced with a C130A substitution mutant to yield strain B31::ospC(C130A). Recombinant protein was also generated. Disulfide-bond-dependent oligomer formation was demonstrated and determined to be dependent on C130. Oligomerization was not required for in vivo function, as B31::ospC(C130A) retained infectivity and disseminated normally. The total IgG response and the induced isotype pattern were similar between mice infected with untransformed B31 and those infected with the B31::ospC(C130A) strain. These data indicate that the immune response to OspC is not significantly altered by formation of OspC oligomers, a finding that has significant implications in Lyme disease vaccine design.
Mutations in the neuronal protein α-synuclein cause familial Parkinson disease. Phosphorylation of α-synuclein at serine 129 is prominent in Parkinson disease and influences α-synuclein neurotoxicity. Here we report that α-synuclein is also phosphorylated at tyrosine 125 in transgenic Drosophila expressing wild-type human α-synuclein and that this tyrosine phosphorylation protects from α-synuclein neurotoxicity in a Drosophila model of Parkinson disease. Western blot analysis of fly brain homogenates showed that levels of soluble oligomeric species of α-synuclein were increased by phosphorylation at serine 129 and decreased by tyrosine 125 phosphorylation. Tyrosine 125 phosphorylation diminished during the normal aging process in both humans and flies. Notably, cortical tissue from patients with the Parkinson disease–related synucleinopathy dementia with Lewy bodies showed less phosphorylation at tyrosine 125. Our findings suggest that α-synuclein neurotoxicity in Parkinson disease and related synucleinopathies may result from an imbalance between the detrimental, oligomer-promoting effect of serine 129 phosphorylation and a neuroprotective action of tyrosine 125 phosphorylation that inhibits toxic oligomer formation.
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In this study, we applied confocal single molecule fluor- escent techniques to investigate the influence of protein phosphorylation by GSK-3β on tau oligomer formation at the single molecule level at nanomolar concentrations. Ex- posure to 10 μM Al 3+ induced the rapid formation of large tau oligomers, while DMSO at a final concentration of 1% led to the formation of smaller oligomers. The large Al 3+ triggered oligomers contained an average of 220 to 240 molecules as shown by FIDA analysis, and were resistant to treatment with 0.2% SDS, which in contrast readily dis- solved the smaller oligomers formed in presence of DMSO. The oligomer sizes observed here were compar- able with data presented earlier . Interestingly, phos- phorylation by GSK-3β yielded an increase in Al 3+ induced tau oligomer formation, while oligomer size was comparable for pTau and mTau.
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Considering these elements, the kinetic approach that rep- resents oligomer formation as the only possible fate for the relevant condensed organics may lead to a significant over- estimation of the oligomer fraction in the aerosol. Thus, it should at least take into account a possible loss of SOA by evaporation, due notably to fragmentation processes (Re- nard et al., 2015). Indeed, organic compounds in the par- ticulate phase have shown to be submitted to a variety of non-oxidative and oxidative reactions leading to the forma- tion of both semi-volatile and non-volatile compounds, de- pending on their final molecular weight (Kroll and Seinfeld, 2008; Kroll et al., 2009). Furthermore, the absence of re- versibility in the kinetic approach makes it little adaptable to laboratory observations such as the evaporation of SOA from α-pinene on the scale of a few hours (Grieshop et al., 2007). On the contrary, the high SOA mass yields obtained from the oxidation of biogenic SVOCs cannot be reproduced using the KPH-deliquescent approach, as SOA formed this way is permanently released due to aerosol water evapora- tion or pH increase. Whatever the model configuration, our works have shown that the oligomerization reversibility pro- posed by the KPH approach was difficult to set up and con- trol in an AQM. Therefore, considering (i) the laboratory ex- periments conducted by Hall and Johnson (2012b) on the ozonolysis of α-pinene, which indicated that oligomer for- mation would be driven by reactive uptake rather than by the partition of monomers between both phases and (ii) the fact that this reactive uptake may be observed within seconds (Heaton et al., 2007; Hall and Johnson, 2012b), it appears more realistic to propose a representation of the oligomer- ization process in two stages: a first fast step modifying di- rectly the monomer partitioning so as to represent the rapid formation of oligomers (not permitted by the KIN approach only), and a stabilization step consisting
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NP of single-stranded negative-sense RNA viruses not only encapsidates RNA in different manners, they also adopt various strategies to form homo-oligomers. Lassa virus NP uses its N-ter- minal domain to interact with the C-terminal domain of the neighboring molecule (23). The extreme N terminus of Rift Valley fever virus NP forms an alpha-helical arm for inserting into the neighboring molecule (11). Human respiratory syncytial virus and Borna disease virus NP use their extreme N and C termini to interact with the neighboring NP, but without tight contacts (27, 30). Rabies and vesicular stomatitis virus NPs use both an ex- tended loop and the extreme N terminus for the interactions (2, 13). While influenza NPs also utilize the extended tail loop for homo-oligomer formation, whether the N-terminal region takes part in the process like the other viral NPs is yet to be determined. Nine ANP monomers are organized in a ring-like structure in a reconstituted mini-RNP (19). Based on the flexibility between the tail loop and the rest of ANP structure observed, we have attempted to construct a 9-mer model (21). The newly deter- mined BNP structure has provided some support to this model. Despite the fact that different interactions at the central helices ( ␣ 11, ␣ 16, and ␣ 17) are found between BNP tetramer and ANP trimer, several hydrophobic interactions are likely to be main- tained. Residue L485 in BNP helix ␣ 16 interacts with the neigh- boring molecule through residue L316 in helix ␣ 11 and residues L501 and M504 of helix ␣17 (Fig. 5Bii and iii). Accordingly, the equivalent ANP residue F429 interacts with F258, I445, and M448 (Fig. 5Bi and iv). These conserved interactions in ANP trimer and BNP tetramer are likely to be kept in NP higher oligomers. The loop region in helix-loop-helix motif (aa 458 to 509), for connect- ing the tail loop to the main body of NP may vary in structural organization upon the formation of different oligomers, as we have observed that A494 and D495 of BNP are part of the loop, while their corresponding residues in ANP S438 and D439 are part of the helix (Fig. 5C). Therefore, the structural features observed TABLE 3 Polymerase activity of BNP homo-oligomerization mutants
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Highlights of our results include the following. Fibrils form over a wide range of conditions. A maximum in the percentage of peptides that end up in a fibril occurs at intermediate temperatures for all concentrations considered. The fibril formation pathway contains the same basic steps at all conditions: free monomers associate to form small amorphous aggregates that grow and rearrange into beta sheets; the beta sheets grow further and stack with each other or with a neighboring amorphous aggregate to form small fibrils; the small fibrils grow by adding beta sheets, amorphous aggregates, or joining with other small fibrils until one or two large fibrils are present at the end of the simulation. The rate of fibril formation increases as concentration increases and temperature decreases. Results obtained by fitting simple exponential kinetic models to the fibril population curves agree qualitatively with experimental results appearing in the literature, in that they display increased lag time and decreased fibril growth rate as temperature increases and
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The pivotal role of amyloid-β oligomers in CAA has not been fully clarified, although the pathogenicity of soluble amyloid-β in CAA is widely known. Cerebrovascular func- tion was impaired even before the appearance of vascular amyloid-β accumulation in Tg-SwDI mice, which were associated with soluble amyloid-β [22, 52]. Passive im- munotherapy by ponezumab, intended to mobilize the interstitial fluid pool of amyloid-β, thus reducing soluble levels, resulted in amelioration of vascular amyloid-β ac- cumulation and an improvement of CVR . However, no linkage between CAA severity and amyloid-β oligomer ex- pression was documented in a human autopsy study . This may be attributable to limitations of biochemical analysis in human brain samples or bias resulting from the comorbidities of Alzheimer’s disease and CAA.
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Electrochemistry have produced important results as an alternative synthesis route for polymerization because offers several distinct advantages such as process control, cheaper preparation procedures and instrumentation, and also enables an alternative approach for fundamental characterization. The mechanism for conducting polymer electro-synthesis involves, at its early stages, oligomer formation. Therefore, in this work electrochemical techniques are used as an alternative route for the synthesis and characterization of aniline (ANI) and o-anisidine (oANS) oligomers. In the present survey synthesis and characterization of ANI and oANS oligomers was successfully accomplished by applying potentiodynamic and potentiostatic techniques to a saturated monomer solution using sulfuric acid as supporting electrolyte. Oligomers characterization was performed by classical means, e.g. FT- IR, UV-vis, and NMR spectroscopy, the last one being the most important to establish oligomer chain length. The controlled formation of ANI and oANS oligomers was obtained by simpler methods than those previously reported using chemical synthesis.
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Abstract: Human islet amyloid polypeptide (h-IAPP) is a peptide hormone that is synthesized and cosecreted with insulin from insulin-secreting pancreatic β-cells. Recently, h-IAPP was proposed to be the main component responsible for the cytotoxic pancreatic amyloid deposits in patients with type 2 diabetes mellitus (T2DM). Since the causative factors of IAPP (or amylin) oligomer aggregation are not fully understood, this review will discuss the various forms of h-IAPP aggregation. Not all forms of IAPP aggregates trigger the destruction of β-cell function and loss of β-cell mass; however, toxic oligomers do trigger these events. Once these toxic oligomers form under abnormal metabolic conditions in T2DM, they can lead to cell disruption by inducing cell membrane destabilization. In this review, the various factors that have been shown to induce toxic IAPP oligomer formation will be presented, as well as the potential mecha- nism of oligomer and fibril formation from pro-IAPPs. Initially, pro-IAPPs undergo enzymatic reactions to produce the IAPP monomers, which can then develop into oligomers and fibrils. By this mechanism, toxic oligomers could be generated by diverse pathway components. Thus, the interconnections between factors that influence amyloid aggregation (eg, absence of PC2 enzyme, deamidation, reduction of disulfide bonds, environmental factors in the cell, genetic mutations, copper metal ions, and heparin) will be presented. Hence, this review will aid in understanding the fundamental causative factors contributing to IAPP oligomer formation and support studies for investigating novel T2DM therapeutic approaches, such as the development of inhibitory agents for preventing oligomerization at the early stages of diabetic pathology. Keywords: amyloid aggregation, causative factor, IAPP, islet amyloid polypeptide, toxic oligomer, T2DM, type 2 diabetes mellitus
Filament and run-on oligomer formation by noncytoskeletal enzymes is a relatively newly discovered phenomenon, being ﬁrst described in 2009 to 2010 for such diverse enzymes as Ire1 (the unfolded protein response nuclease-kinase) (9), CTP synthase (10, 11), ACC (acetyl-coenzyme A [CoA] carboxylase) (12), and SgrAI (7). At approximately the same time, large-scale screens for protein localization using ﬂuorescence micros- copy showed unexpectedly that many enzymes formed ﬁlaments in response to particular metabolic conditions or other stimuli in cells (11, 13–15). The term “run-on oligomer” (ROO) ﬁlament is used here to describe an assembly of an enzyme into a ﬁlament by the successive addition of enzymes at either end, and which, in principle, could extend indeﬁnitely (8, 16). ROO ﬁlament formation by SgrAI was ﬁrst proposed in 2010 based on behavior in analytical ultracentrifugation and native gels (7) and subsequently using ion-mobility mass spectrometry (17). The enzymatic activity of SgrAI was found to be activated in the ROO and to possess an altered (expanded) DNA sequence speciﬁcity (7, 8). The three-dimensional cryoelectron microscopy (cryo-EM) structure of the ROO ﬁlament formed by the assembly of SgrAI/DNA complexes shows a left-handed helical arrangement with approximately four DNA-bound dimers of SgrAI per turn (Fig. 1A to D show different views of an individual SgrAI/DNA complex) (8). In the ROO ﬁlament helix, both the DNA and SgrAI form stabilizing interactions with neighboring SgrAI/DNA complexes (Fig. 1A, E, and F) (8).
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Organosiloxyalumoxane and organoalumoxanesiloxane oligomers were synthesized 30 years ago . Their probable structure from conventional viewpoint looked like three- coordinated Al atom. These compounds are amorphous, therefore it did not seem possible to prove their structure by means of X-ray diffraction. But in the middle of 1980s papers dealing with nonclassical structure of alumoxane and alumosiloxane compounds with four-coordinated Al atom and three-coordinated oxygen atom were published [2–4]. The coordination number of Al atoms in bicyclic and oligomer alumoxanes and alumosiloxanes was shown to be 4 and may increase to 5 (or even to 6) . The crystalline structure of alumosiloxane of C 8 H 24 Al 3 Br 5 O 6 Si 4
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To summarize these results above, pyridine enhances the open voltage and the short current density at the same time, to improve the energy conversion efficiency for both Mi and Mp ionic liquid. These improvements are more noticeable for the Step 1 treatment than Step 2, except for the fill factor. The difference between the two steps is outstanding for the short current density of the Mp sample, which leads to the conversion efficiency of 4% as a result. The fact that Step 1 gives better performance of the cell than Step 2 tells us that pyridine can- not entirely permeate into the gel after the electrolyte is gelated with the fluorinated oligomer. We are speculat- ing pyridine plays a key role to form a kind of micro phase separation in the electrolyte.
To demonstrate the reaction of ADR oligomer with PLA and SF, the FTIR spectra of raw SF and extracted SF from corresponding composites are shown in Figure 5. The peak at 1735 cm -1 stands for the stretching vibration peak of carbonyl (C=O). The bare of this 1735 cm -1 peak in raw SF reflected the alkaline treatment removed the lignin, impurity, pectin and waxy substances of sisal fibers [16,17]. It was also observed that no obvious 1735 cm -1 peak occurred in the SF extracted from PLA/SF composites, reflecting poor interfacial interaction between SF and PLA matrix in PLA/SF composites. However, it was found that the1735 cm -1 peak was enhanced with addition of ADR into PLA/SF composites especially for PLA/SF/ADR composites with 0.4, 0.6, and 0.8 wt% ADR addition. This phenomenon indicated the reaction of ADR oligomer with PLA and SF during the melt-blending processing, which resulted in the bonding of PLA molecular chain to sisal fibers.
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Abstract. The author's method of oligomer sums for analysis of oligomer compositions of eukaryotic and prokaryotic genomes is described. The use of this method revealed the existence of general rules for cooperative oligomeric organization of a wide list of genomes. These rules are called hyperbolic because they are associated with hyperbolic sequences including the harmonic progression 1, 1/2, 1/3, .., 1/n. These rules are demonstrated by examples of quantitative analysis of many genomes from the human genome to the genomes of archaea and bacteria. The hyperbolic (harmonic) rules, speaking about the existence of algebraic invariants in full genomic sequences, are considered as candidates for the role of universal rules for the cooperative organization of genomes. The described phenomenological results were obtained as consequences of the previously published author's quantum- information model of long DNA sequences. The oligomer sums method was also applied to the analysis of long genes and viruses including the COVID-19 virus; this revealed, in characteristics of many of them, the phenomenon of such rhythmically repeating deviations from model hyperbolic sequences, which are associated with DNA triplets. In addition, an application of the oligomer sums method are shown to the analysis of the following long sequences: 1) amino acid sequences in long proteins like the protein Titin; 2) phonetic sequences of long Russan literary texts (for checking of thoughts of many authors that phonetic organization of human languages is deeply connected with the genetic language). The topics of the algebraic harmony in living bodies and of the quantum-information approach in biology are discussed. Key words. DNA oligomers, harmonic progression, hyperbolic rules, matrices, tensor product, quantum informatics, oligomer sums method, genomes, genes, viruses, proteins, long Russian texts, phonetic sequences.
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The molecular structure of the product is characterized by nuclear magnetic resonance spectrum (NMR, 1 H and 13 C), mass spectrometry (MS), Fourier transform infrared spectroscopy (FTIR) and ultraviolet visible (UV-Vis) spectrum, respectively. The 1 H NMR spectrum of the product is shown in Figure 2a. The strongest signals at δ 1.63 (s) demonstrate the existence of the protons on methyl of the chain structure in prepared product. Other signals appear at 3.43, 2.54, 2.50 are assigned to small amount of adsorption of water, the DMSO residuary in the reaction process and solvent peak of DMSO, respectively. The 13 C NMR spectrum (Figure 2b) of the product displays two singlets at 26.42 and 175.45ppm, which illustrate the existence of carbon atoms of methyl and unsaturated carbon in the chain structure, respectively. The peak with relatively strong intensity at 40 ppm is attributed to the carbon atom in solvent DMSO. On the basis of the results of NMR characterization, it can be obtained that the PAcN oligomer was formed according to the molecular formula as shown in Figure 1.
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This article presents the results of deformation-strength properties measurement and microstructural analysis of hetero- geneous polymer matrix consisting of thermoset and thermoplastic polymers. Thermosetting material is a diamino-di- phenil sulfon-cured epoxy oligomer. Polysulfone was used as thermoplastic material. Two different technological proc- esses were used to obtain heterogeneous polymer matrix: the material was mixed in the block, or layered material was produced in which a layer of thermoplastic material alternated with a layer of epoxy oligomer.
FIG. 1. Southern and Northern blot analyses of replicate products of HBV insertion mutants. (A) Schematic representation of restriction sites and genome organization of HBV. Four open reading frames of HBV are shown at the top, i.e. genes of core protein (C), surface protein (S), DNA polymerase (P), and X protein (X). The XhoI site was used to insert either 825 or 1,021 bp of the lacZ DNA as indicated. The cis elements required for HBV replication are located on the genome, including direct-repeat elements (DR1, DR1*, and DR2) and the RNA encapsidation signal sequence (ε) located at the 5⬘ end of pgRNA. The polymerase-linked oligomer priming site is located at the bulge region of ε. (B and C) Southern blot analysis of HBV nucleic acids. Cytoplasmic cores were isolated from HuH-7- transfected cell 5 days posttransfection. HBV DNAs which had been repaired using endogenous polymerase reaction with cold deoxynucleoside triphosphates (12) were isolated from core particles produced by HuH-7 cells transfected with various plasmids as indicated at the top of the figures. Undigested (lanes 1 to 3) or EcoRI-digested (lanes 4 to 6) DNA samples were separated by agarose gel electrophoresis (1.3% agarose), and transferred to a filter, hybridized with 32 P-labeled full-length HBV DNA
This work intended to develop a new material from plastic arising from municipal solid waste. The discarded PET was oligomerized by a polyfunctional alcohol. The PET oligomer was mixed with CAP in different propor- tions to evaluate its influence on the CAP’s thermal, ad- hesive and morphological characteristics.
firmed by asymmetric-flow field-flow fractionation (AF4), a technique that has previously been used to separate small non- fibrillar ␤ -sheet-rich oligomers of PrP from scrapie-infected mouse brain material (12). The molecular mass determined for the oligomer using this technique was ⬃ 226 ⫾ 36 kDa, in agreement with the values obtained using AUC (Fig. 3), and the number of monomers in infectious prion particles (12). The monomeric species was similarly identified with a close corre- spondence with the AUC data (Fig. 3). The hydrodynamic radius of the oligomer was determined using in-line dynamic light scattering measurements to be ⬃ 11 nm. Notably, the AF4 data indicated a low degree of polydispersity for the oligomeric species (1.04), indicating that the ␤ -PrP 23–231 oligomer was
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reported to be toxic to neuronal cell cultures (13, 29, 30, 66, 74, 75). The variety of cell types tested, the various preparations of recombinant PrP oligomers, and the considerable experimental variation may explain variability in toxicity, but it is also prob- able that subtle differences between the various species under investigation can result in large differences in biological effect. Indeed this has been reported for the bacterial protein HypF-N; this protein forms two oligomers that are similar according to AFM and thioflavin T reactivity, but toxicity is displayed by the one that is characterized by a lower degree of hydrophobic packing (76). The reducing/acidic conditions for the ␤ -PrP oligomerization may be unfavorable for the production of tox- ic/infectious oligomers, however, it is also possible that ␤ -PrP toxicity may occur via a more discrete mechanism, or biological activity requiring perhaps other specific binding partners (for example, the PrP/A ␤ interaction) (77), in which only certain transient A ␤ assemblies cause PrP-dependent toxicity (20), and thus may require the application of the oligomer to more spe- cialized models.
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