Oligomer Concentration Research Articles

Addition of chitosan oligomers to improve bread texture

This study aimed to characterize the bread products that was given additional chitosan oligomer from crustacean (shrimp) waste. The making of bread with the addition of chitosan oligomer was carried out with concentration treatment (0, 0.1%, 0.3% and 0.5%) and the test parameters were chemical, physical (functional groups of chitosan oligomers, hardness with texture profile analyzer, and appearance of bread texture improvement using SEM tools) and sensory (hedonic). The results of chemical content of white bread showed that of moisture content ranged from 28.50% to 31.48%, protein content of 8.75%-10.85%, fat content of 5.87%-7.6% and carbohydrate (by different) of 48.77% to 56.88%. Analysis of hydroxyl groups in chitosan oligomers using FTIR displayed an absorption at a wavelength of 1437.7 cm−1. Based on the results of hardness testing, the greater the concentration of chitosan oligomer added, the lower the hardness value of the resulting bread would be, making the texture softer. The results of SEM analysis showed that the addition of chitosan oligomer expanded more perfectly, especially in the addition of chitosan oligomer treatment by 0.3%. The overall hedonic test results on the bread gave insight that the addition of chitosan oligomer treatment by 0.3% was the most preferred.

Antifungal activity of chitosan oligomer prepared using chitosanase of Aeromonas media KLU 11.16

Chitosan oligomer is a hydrolysis product of chitosan which can be prepared by enzymatic method, including chitosanase that may be produced by bacteria. Previously, chitosanase from Aeromonas media KLU 11.16 has been purified and characterized. The aim of this study was to analyze the bioactivity of chitosan oligomer prepared by using Aeromonas media KLU 11.16 chitosanase, as antifungal. Chitosan oligomer was prepared from shrimp waste chitosan, and hydrolyzed by 8U chitosanase per gram chitosan. The reaction time was for 2, 3 and 4 hours at 30°C. The oligomer produced then determined their yields and viscosities; and was identified by using a thin layer chromatography (TLC). Antifungal activity test against Aspergilus flavus, A. niger, Eurotium amstelodami and Emericella nidulans was performed on selected oligomers based on consideration of yield and TLC result, with oligomer concentrations of 0; 50; 100 and 200 ppm. The result showed that hydrolysis chitosan by Aeromonas media KLU 11.16 chitosanase for 4 hours reduced the viscosity from 187.5 to 13 cPs, and produced oligomers 96.14% of yield. The oligomers identified by TLC were monomer (1 unit) to hexamer (6 unit), and showed their antifungal activity against the four fungi tested. The best inhibition was showed by 200 ppm of oligomer against A. flavus.

Highly sensitive aptasensor based on interferometric reflectance spectroscopy for the determination of amyloid β as an Alzheimer's disease biomarkers using nanoporous anodic alumina

It is well known that Alzheimer's disease is one of the global challenges for the 21st century. Therefore, it is urgent to develop a reliable biosensor for the detection of this disease. Here in, we have developed for the first time, an aptasensor based on interferometric reflectance spectroscopy (IRS) for the determination of amyloid β (Aβ) oligomers that is an Alzheimer's disease biomarker. For this purpose, the nanoporous anodic alumina (NAA) was first fabricated. After that, the pore walls of the NAA were modified with (3-aminopropyl) trimethoxysilane (NAA-NH2). The amino-terminal aptamers probe were then attached to the pore walls of the NAA-NH2 by using glutaraldehyde (GA) as the cross-linking agent. Subsequently, methylene blue (MB) was immobilized into the aptamer as the photo-probe, generating the MB/G-quadruplex complex. Since MB has a high absorption coefficient, the intensity of the reflected white light to the charge-coupled device (CCD) detector decreased. In the presence of the Aβ oligomers that have high affinity to the immobilized aptamer, the MB/quadruplex complex broke and MB washed away from the aptasensor. Therefore, the intensity of the reflected white light to the CCD detector increased. The increased signal intensity of the aptasensor has a logarithmic relationship with the concentration of Aβ oligomers. The proposed aptasensor exhibited a good response to the concentration of Aβ oligomers in the range of 0.5–50.0 μg × mL−1. The experimental detection limit was of 0.02 μg × mL−1 (at 3σ/S). The proposed optical aptasensor exhibited good selectivity, linear range, and stability.

Characterization of hydrosoluble fraction and oligomers in poly(vinylidene chloride) latexes by capillary electrophoresis using electrophoretic mobility modeling

The characterization of hydrosoluble oligomers in latexes is an important topic in emulsion polymerization since oligomers are suspected to be responsible for latex destabilization. In this work, the hydrosoluble fraction of poly(vinylidene chloride) latexes synthesized by emulsion polymerization of three monomers (acrylic acid, methyl acrylate, vinylidene chloride) was characterized by capillary electrophoresis (CE). CE using direct UV detection permitted to estimate residual monomers and surfactants concentrations contained in the latexes serums. Water soluble oligomers, polymerization initiator (persulfate) and other inorganic anions were detected by indirect UV detection. The oligomers content in the dry extract of serum was estimated to be about 6% (% m/m) represented mainly by 9 different compounds belonging to 3 different families. Using a semi-empirical electrophoretic mobility modeling, the charge number of these oligomers was estimated to be −2 and the molar masses were estimated in the range of ∼300–550 g.mol−1. Oligomer samples obtained by surfactant-free polymerization, with different initial monomers proportions, provided qualitatively 14 different oligomers, including the 9 oligomers previously detected in the serums. Finally, the latex was characterized (electrophoretic mobility and zeta potential) using its serum as a background electrolyte. This approach could be very useful to study the behavior of the latexes, and possibly destabilization effect, in analytical conditions very close to its real environment / applications.

Determining the migration of nadic acid, terephthalic acid, isophthalic acid and two oligomers from polyester food cans into food in the U.S. market

Concentrations of three monomers used in the manufacture of polyester resins for food cans, isophthalic acid (IPA), terephthalic acid (TA) and nadic acid (NA), and two oligomers were determined in canned food samples. All canned foods were purchased in local supermarkets in the United States. Concentrations of IPA and TA were determined to be from below the limit of detection in tomato sauce to 69 μg/kg in coconut milk, while the highest concentration of NA was found in pumpkin at 21 μg/kg. Estimated concentrations of oligomers in the food samples ranged from non-detect to 595 μg/kg. The influence of the storage time, lot type, and retail outlet on the migration concentrations was also investigated.

Residual Monomer Content Affects the Interpretation of Plastic Degradation

Plastic degradation rates in the marine environment are essential to understand. This study demonstrates that in plastic-microbial interaction experiments, residual monomeric and oligomeric content of PA6 significantly influences the development of dissolved organic carbon. While it is well recognized that additives in plastics should be considered during the inception of plastic-exposure experiments, residual monomers have yet to be prominently considered in the same light. As such, in degradation studies where residual contents of monomers and/or oligomers are not considered, degradation of synthetic polymers could be significantly overestimated. The substantial conversion of these monomeric and oligomeric leachates also has implications for plastic-biofilm development studies and microplastic-biota-based ingestion experiments.

Mechanisms of Protein Fibril Formation in Amyloid Beta and Lysozyme Proteins

Rigid fibril (RFs) formation of amyloid proteins is a precursor to many degenerative disorders, thus understanding the kinetics behind their generation could yield important information with respect to disease pathology. These amyloid proteins exhibit what is known as the “critical oligomer concentration” (COC), exhibiting similar behavior as that of micelle formation by surfactants. At low concentrations these proteins generate only smaller oligomeric species and RFs, upon crossing the COC the growth of globular oligomers (gOs) and curvilinear fibrils (CFs) begin, aggregate species that have been shown to be strongly correlated with disease pathology. Below the COC, RFs result in a sigmoidal rise with an initial lag period generated by delayed polymer nucleation. Above the COC, the rapid generation of gOs/CFs result in the elimination of the initial lag period, followed by a secondary rise due to RF growth, producing a biphasic onset. Here, we simulate the growth kinetics of amyloid beta and lysozyme proteins utilizing the theory of nucleated polymerization with off-pathway aggregation, with the assumption that on-pathway nucleation and off-pathway aggregation occur so rapidly that they can be represented as a single step. We show that in order to simulate experimental fibril formation, the primary nucleation rate must be significantly decreased at initial monomer concentration where there is a significant amount of off-pathway aggregates, resulting in a corresponding increase in initial lag periods. In addition, attempting similar fitting with models of the same type produce comparable trends, further supporting our initial findings, and hinting at a possibly inhibitory effect on RF growth by gOs/CFs.

A study of optimization parameters for the development of ultraviolet cured low-acid optically clear adhesive

This study introduced multi-quality optimization using the Taguchi method combined with response surface methodology (RSM) and the particle swarm optimization (PSO) method for synthesizing pressure sensitive adhesives (PSAs) of ultraviolet curing optically clear adhesives (OCAs). The process parameters used in this study included 2-ethylhexyl acrylate (2-EHA) monomer content, the photoinitiator content and the oligomer content using N,N-dimethylacrylamide and acrylic acid. The quality responses included the peel strength, the transmittance, the haze and the refractive index. The Taguchi method was adopted because it could reduce the number of experiments and cost, as well as effectively arriving at a single optimum parameter. The results from the Taguchi method were combined with RSM and PSO to obtain a single composition that has the optimum response for all qualities. The results of the confirmation experiment showed that the optimum parameters were 80 wt% of 2-EHA content, 4.32 wt% of photoinitiator content and 45 wt% of oligomer content, which could obtain the peel strength at 720.3 g/25.4 mm, transmittance up to 97.94%, haze of only 1.93% and refractive index at 1.48. All of qualities meet the industrial requirement of OCA PSAs.

Unusual stability exhibited by (AT)XN12(AT)Y motif associated with high fetal hemoglobin levels

Quasi-palindromic sequences (AT)XN12(AT)Y present in HS2 (hypersensitive site 2) of the human β-globin locus are known to be significantly associated with increased fetal hemoglobin (HbF) levels. High HbF levels in some adults arise due to pathological conditions such as sickle cell disease and β-thalassemia. However, elevated levels of HbF are also associated with a reducing morbidity and mortality in patients with β-thalassemia and thus ameliorate the severity of the disease. Using gel-electrophoresis, ultraviolet (UV)-thermal denaturation, and circular dichroism (CD) techniques, we demonstrated that it exhibits a hairpin-duplex equilibrium. Intramolecular species (hairpin) were observed in both low and high salt concentrations in gel assay studies displaying the unusual stability of intramolecular species even at the high counter-ion concentration. The unusual stability of hairpin secondary structures was also demonstrated by the monophasic nature of the melting profiles for the oligonucleotides which persisted at low as well as high salt and oligomer concentrations. Change in CD spectra as a function of oligomer concentration indicates that the bimolecular duplex formation is selectively favored over monomolecular hairpin formation at and above 9 µM oligomer concentration. Thus, we hypothesize that imperfect inverted repeat sequence (AT)XN12(AT)Y of HS2 of β-globin gene LCR forms the unusually stable hairpins which may result in the formation of a cruciform structure that may be recruited for binding by various nuclear proteins that could result in elevated HbF levels.Communicated by Ramaswamy H. Sarma.

Evaluation of Temporal Aggregation Processes Using Spatial Intensity Distribution Analysis.

Small proteinaceous oligomeric species contribute to the formation of larger aggregates, a phenomenon that is of direct relevance to the characterization of protein aggregation in biopharmaceuticals and understanding the underlying processes contributing to neurodegenerative diseases.The ability to monitor in situ oligomerization and aggregation processes renders imaging and image analysis an attractive approach for gaining a mechanistic insight into early processes contributing to the formation of larger aggregates in disease models and biologics. The combination of image analysis tools enables the detection of both oligomeric and larger aggregate subtype in contrast to conventional kinetic-based approaches that lack the ability to resolve dimers from monomeric moieties in samples containing mixed populations.In this chapter, we describe the process for confocal time series image acquisition for monitoring the in situ loss of monomers, and the subsequent analysis pipeline using spatial intensity distribution analysis (SpIDA) to evaluate oligomer content.

Structural and functional comparability study of anti-CD20 monoclonal antibody with reference product.

BackgroundCell surface protein, CD20, is extensively expressed on the surface of B cells. Antibodies targeting CD20 protein are being used to treat B-cell malignancies and B-cell mediated autoimmune diseases. Considering the cost of therapy with innovator monoclonal antibodies for these diseases, development of biosimilar products for the treatment of such diseases provides affordable solution to rising healthcare costs.Materials and MethodsReference products of rituximab (six batches) were procured and stored as per manufacturer's instructions. Cell lines used in bioassay were procured from American Type Culture Collection and all other reagents used for analysis were of analytical grade. Primary structure was studied by intact mass analysis, peptide fingerprinting, peptide mass fingerprinting and sequence coverage analysis. Higher order structure was studied by circular dichroism, ultraviolet-visible spectroscopy, fluorescence spectroscopy, and disulfide bridge analysis. Different isoforms of reference product and SB-02 were identified using capillary isoelectric focusing and capillary zone electrophoresis. Glycosylation was studied by N-glycan mapping using LC-ESI-MS, point of glycosylation, released glycan analysis using ultra performance liquid chromatography (UPLC). Product related impurities such as oligomer content analysis and oxidized impurities were studied using size exclusion chromatography and reverse phase high performance liquid chromatography, respectively.Results and ConclusionHere, we report physicochemical and biological characterizations of Sun Pharma’s proposed biosimilar (SB-02) to rituximab, a monoclonal anti-CD20 antibody approved for the treatment of non-Hodgkin’s lymphoma and chronic lymphocytic leukemia. SB-02 and rituximab exhibited indistinguishable primary as well as higher-order structure upon analyzing with the array of analytical and extended characterization methods according to statistical methods. The molecule also displayed comparability to reference product in post-translational modifications and charge heterogeneity. In functional bioassays, SB-02 demonstrated comparable potency with respect to reference product. Our results indicate highly similar quality profile between SB-02 and rituximab.

A Multichannel Time-Tagged Time-Resolved (TTTR) Model for Quantification of Oligomer Concentrations Based on Antibunching Effect.

Molecule/protein aggregation causes many devastating and incurable diseases in human bodies. For example, studies have revealed that protein oligomers formed at the early stage are toxic and may be mostly responsible for some diseases. In the fundamental research, differentiation of different protein oligomers and quantification of the concentrations are important and challenging. Here, we have developed a multichannel time-tagged time-resolved (TTTR) confocal fluorescence model based on antibunching effect to solve the problem. The key point of the model is that n-oligomers labeled with n-dyes cannot emit more than n photons at one time. By assuming that all labeling dyes behave perfectly as noninteractive individual dyes, the analytic relationship between photon-emission probability and oligomer concentrations has been derived. Simulations have been carried out to verify the model, in which differentiation and concentration quantification of up to tetraoligomers can be realized with a relative error <10% in an eight-channel TTTR confocal setup with eight single-photon detectors.

Oligomers in polyethylene furanoate - identification and quantification approach via LC-UV LC-MS response ratio

ABSTRACTPolyethylene furanoate polymer is intended to be used as a food contact material. A PEF polymer sample was investigated for its oligomer composition by solvent extraction and using HRLC-MS. The 20 oligomers found were divided into four groups: group I contains cyclic oligomers consisting of furandicarboxylic acid and monoethylene glycol units, group II comprises cyclic oligomers consisting of furandicarboxylic acid, monoethylene glycol units and one diethylene glycol unit, group III are cyclic oligomers were two monoethylene glycol units are substituted by diethylene glycol units and group IV are linear oligomers consisting of furandicarboxylic acid and monoethylene glycol units. Oligomers of group I account for around 87% of the total oligomer content, group II oligomers 12% and group III oligomers 1%. The contribution of group IV oligomers is very small: less than 0.05%. MS-MS experiments showed similar fragmentation patterns for all oligomers. The results of this study demonstrate that oligomers are abundant in the PEF material and are potential migrants to foods that are in contact with the polymer. Oligomers of group I and group II have the same absorption maxima in UV detection which was used to develop a quantification approach for these oligomers using dimethyl 2,5-furandicarboxylate as external standard.

Synthesis of Amphiphilic Oligomers of Acrylic Acid

Synthesis of amphiphilic oligomers of acrylic acid via radical polymerization in the presence of thiols as molecular mass regulators is described. The effect of the length of the introduced hydrophobic terminal group on the critical micellization concentration of the acrylic acid oligomers has been elucidated. It has been shown that the incorporation of an antituberculous drug (prothionamide) in the micelles of acrylic acid oligomers is enhanced with the increase in the length of the hydrophobic moiety. The preparation of hydroxyapatite-filled calcium-polycarboxylate bone cements containing prothionamide (promising for the sealing of postoperative cavities) is described.

A novel electrochemical aptasensor based on nontarget-induced high accumulation of methylene blue on the surface of electrode for sensing of α-synuclein oligomer

This study describes a novel electrochemical aptasensor for detection of α-synuclein (α-syn) oligomer, an important biomarker related to Parkinson's and Alzheimer's diseases. The sensing platform is based on exonuclease I (Exo I), terminal deoxynucleotidyl transferase (TdT) and methylene blue. The aptasensor exploits the improved sensitivity because of applications of TdT and Exo I and also a label-free aptamer (Apt). Furthermore, direct immobilization of complementary strand of aptamer (CS) instead of Apt on the surface of electrode prohibits Apt self-assembled monolayer aggregation and keeps the function of the Apt. In the absence of α-syn oligomer, TdT enhances lengths of Apt and CS and so, increases accumulation of methylene blue as redox agent on the surface of electrode, leading to a strong current signal. While in the presence of α-syn oligomer, Exo I digests CS on the electrode surface, resulting in less accumulation of methylene blue on the electrode surface and a weak current signal. The relative electrochemical signal of the aptasensor increased linearly with the logarithm of α-syn oligomer concentration in the range from 60 pM to 150 nM. The detection limit was 10 pM. Furthermore, the sensor showed high precision and repeatability for detection of α-syn oligomer in serum samples.

Degradation of Post-consumer PLA: Hydrolysis of Polymeric Matrix and Oligomers Stabilization in Aqueous Phase

Degradation of post-consumer PLA to lactic acid was analysed in order to assess the economic feasibility of the PLA chemical recycling process. Hydrolysis of PLA, in batch reactor, was analysed in the temperature range of 443–473 K, under autogenous pressure and a constant PLA to water ratio (equal to approximately 0.11 by weight), without the use of a catalyst. The experimental results suggest that the complete degradation of PLA can be obtained using relatively low reaction-times with the production of a mixture containing the monomer and traces of the dimer of lactic acid. The overall process was modelled using a two-step process: bulk degradation of PLA (in the solid or molten phase) with the solubilisation of low molecular weight oligomers, and their subsequent hydrolysis in water (stabilization). The model describes the trend of oligomer concentrations in the aqueous phase and PLA conversion as a function of time with both high accuracy and agreement with experimental results.

Picomolar concentrations of oligomeric alpha-synuclein sensitizes TLR4 to play an initiating role in Parkinson\u2019s disease pathogenesis

Despite the wealth of genomic and transcriptomic data in Parkinson’s disease (PD), the initial molecular events are unknown. Using LD score regression analysis, we show significant enrichment in PD heritability within regulatory sites for LPS-activated monocytes and that TLR4 expression is highest within human substantia nigra, the most affected brain region, suggesting a role for TLR4 inflammatory responses. We then performed extended incubation of cells with physiological concentrations of small alpha-synuclein oligomers observing the development of a TLR4-dependent sensitized inflammatory response with time, including TNF-α production. ROS and cell death in primary neuronal cultures were significantly reduced by TLR4 antagonists revealing that an indirect inflammatory mechanism involving cytokines produced by glial cells makes a major contribution to neuronal death. Prolonged exposure to low levels of alpha-synuclein oligomers sensitizes TLR4 responsiveness in astrocytes and microglial, explaining how they become pro-inflammatory, and may be an early causative event in PD.

Boron-containing UV-curable oligomer-based linseed oil as flame-retardant coatings: synthesis and characterization

A boron-containing UV-curable oligomer was derived from linseed oil, phenylboronic acid and glycidyl methacrylate to use in flame-retardant coating applications. The synthesized UV-curable oligomer was characterized for its structural and physicochemical properties by means of Fourier transform infrared (FTIR), 1H and 11B-nuclear magnetic resonance (NMR) spectroscopy techniques. The boron-containing UV-curable oligomer (BELO) was added to a conventional polyurethane acrylate (PUA) at varying concentrations ranging from 10 to 40 wt% in the presence of a photoinitiator and a reactive diluent. LOI and UL-94 tests were performed to understand the flame-retardancy behavior of the synthesized BELO oligomer, and the results revealed that the flame retardancy of UV-curable coatings enhanced as the percentage of BELO oligomer in the coating formulations increased. The glass transition temperature (Tg) and thermal stability of cured coatings were analyzed by differential scanning calorimetry and thermogravimetric analysis, respectively. The TGA analysis showed that char yield at 600 °C increased by increasing the BELO oligomer content. The mechanical properties, and stain, solvent, and chemical resistance and thermal behavior of the coatings were investigated. Incorporation of BELO into the PUA coating formulations and the comparison of the properties of BELO-incorporated PUA coatings with those of the conventional PUA coating exhibited interesting results.

All organic near ultraviolet photodetectors based on bulk hetero-junction of P3HT and DH6T

The effect of oligomer concentration on the performance of polymer and oligomer blended system based photo-detectors was investigated. Improvement in dark rectification ratio and photoresponse of diode were observed in the blended system photodetectors compared to pristine polymer based photodetectors. The photodetectors fabricated with poly(3-hexylthiophene) (P3HT) and α, ω-di-hexyl-sexithiophene (DH6T) were tuned to two different wavelengths namely 525 nm and 400 nm respectively, corresponding to the maximum of the absorption of polymer and oligomer materials respectively. It was observed that the effective conjugation length and disorder in the polymer chains critically affect the photoresponse of organic optoelectronic devices. In this study, improvement in effective conjugation length and disorder were observed as the concentration of DH6T in the blend was increased; leading to the enhancement in the photoresponse of the fabricated device with these blends. Herein, with the increase of DH6Tconcentartion in the blended thin films, the photoresponsivity of fabricated photodetectors towards near UV at ∼400 nm wavelength in addition to the 525 nm wavelength was found to be increased. Comparable photosensitivity (∼1.6 × 103) and responsivity (∼18 A W−1) were achieved for both the wavelengths separately, in the blended photodetectors fabricated with a DH6T concentration of 40%. Such devices tuned to dual wavelength may also find their application in the field of optically switched logic gates.

Role of soluble aluminum species in the activating solution for synthesis of silico-aluminophosphate geopolymers

An aluminosilicate precursor, such as metakaolin, can be transformed into a cement-like geopolymer binder via a phosphate activation approach. This paper identifies the effect of the addition of aluminum species into the phosphate activating solution on the formation of such geopolymers, from the fresh to the hardened state. Activating solutions with Al/P molar ratios of 0, 0.1, and 0.3 were prepared by blending monoaluminum phosphate (MAP) and orthophosphoric acid (OPA). The rheological properties, fluidity, and setting times of the fresh geopolymer pastes and the compressive strength of the hardened geopolymer matrices were studied. Liquid-state 27Al and 31P nuclear magnetic resonance (NMR) measurements for the chemical environments of Al and P, and spectroscopic, thermal, and microscopic analyses revealed that the soluble aluminum in the phosphate activating solution played an important role during the geopolymerization process. Seeding of aluminum species through inclusion in the activating solution allowed a rapid sol/gel transition that improved the rheological properties and setting time of the fresh geopolymer pastes at ambient temperature. However, although the increased concentration of aluminum phosphate oligomers promoted by the soluble aluminum addition contributed to the formation of a compact matrix with high early strength, it hinders the ongoing reaction of metakaolin in the later period, which has a detrimental influence on ongoing strength development beyond 7 days of curing.