ResearchPad - polymer-chemistry https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[Concept of an artificial muscle design on polypyrrole nanofiber scaffolds]]> https://www.researchpad.co/article/elastic_article_8464 Here we present the synthesis and characterization of two new conducting materials having a high electro-chemo-mechanical activity for possible applications as artificial muscles or soft smart actuators in biomimetic structures. Glucose-gelatin nanofiber scaffolds (CFS) were coated with polypyrrole (PPy) first by chemical polymerization followed by electrochemical polymerization doped with dodecylbenzensulfonate (DBS-) forming CFS-PPy/DBS films, or with trifluoromethanesulfonate (CF3SO3-, TF) giving CFS-PPy/TF films. The composition, electronic and ionic conductivity of the materials were determined using different techniques. The electro-chemo-mechanical characterization of the films was carried out by cyclic voltammetry and square wave potential steps in bis(trifluoromethane)sulfonimide lithium solutions of propylene carbonate (LiTFSI-PC). Linear actuation of the CFS-PPy/DBS material exhibited 20% of strain variation with a stress of 0.14 MPa, rather similar to skeletal muscles. After 1000 cycles, the creeping effect was as low as 0,2% having a good long-term stability showing a strain variation per cycle of -1.8% (after 1000 cycles). Those material properties are excellent for future technological applications as artificial muscles, batteries, smart membranes, and so on.

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<![CDATA[Analysis and modeling of coolants and coolers for specimen transportation]]> https://www.researchpad.co/article/N4e3aeb5c-7b13-42da-a06e-637c738940f8

Maintaining cold chain while transporting medical supplies and samples is difficult in remote settings. Failure to maintain temperature requirements can lead to degraded sample quality and inaccuracies in sample analysis. We performed a systematic analysis on different types of transport coolers (polystyrene foam, injection-molded, and rotational molded) and transport coolants (ice, cold packs, frozen water bottles) frequently in use in many countries. Polystyrene foam coolers stayed below our temperature threshold (6°C) longer than almost all other types of coolers, but were not durable. Injection-molded coolers were durable, but warmed to 6°C the quickest. Rotational molded coolers were able to keep temperatures below our threshold for 24 hours longer than injection molded coolers and were highly durable. Coolant systems were evaluated in terms of cost and their ability to maintain cold temperatures. Long lasting commercial cold packs were found to be less cost effective and were below freezing for the majority of the testing period. Frozen plastic water bottles were found to be a reusable and economical choice for coolant and were only below freezing briefly. Finally, we modeled the coolers performance at maintaining internal temperatures below 6°C and built a highly accurate linear model to predict how long a cooler will remain below 6°C. We believe this data may be useful in the planning and design of specimen transportation systems in the field, particularly in remote or resource limited settings.

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<![CDATA[The effect of NaOH pretreatment on coal structure and biomethane production]]> https://www.researchpad.co/article/Nec5b1db1-34f5-4425-bec1-1f1e431a6eb6

Biogenic CBM is an important component of detected CBM, which is formed by coal biodegradation and can be regenerated by anaerobic microorganisms. One of the rate-limiting factors for microbial degradation is the bioavailability of coal molecules, especially for anthracite which is more condense and has higher aromaticity compared with low-rank coal. In this paper, NaOH solution with different concentrations and treating time was employed to pretreat anthracite from Qinshui Basin to alter the coal structure and facilitate the biodegradation. The results showed that the optimal pretreatment conditions were 1.5 M NaOH treating for 12 h, under which the biomethane production was increased by 17.65% compared with untreated coal. The results of FTIR and XRD showed that NaOH pretreatment mainly reduced the multi-substituted aromatics, increased the C-O in alcohols and aromatic ethers and the branching degree of aliphatic chain, and decreased the aromatic ring structure, resulting in the improvement of coal bioavailability and enhancement of biomethane yield. And some organics with potential to generate methane were released to filtrate as revealed by GC-MS. Our results suggested that NaOH was an effective solution for pretreating coal to enhance biogenic methane production, and anthracite after treating with NaOH could be the better substrate for methanogenesis.

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<![CDATA[Crystal structures of Triosephosphate Isomerases from Taenia solium and Schistosoma mansoni provide insights for vaccine rationale and drug design against helminth parasites]]> https://www.researchpad.co/article/N340e3046-cb91-4c84-8d1b-fb2a65cf4cdb

Triosephosphate isomerases (TPIs) from Taenia solium (TsTPI) and Schistosoma mansoni (SmTPI) are potential vaccine and drug targets against cysticercosis and schistosomiasis, respectively. This is due to the dependence of parasitic helminths on glycolysis and because those proteins elicit an immune response, presumably due to their surface localization. Here we report the crystal structures of TsTPI and SmTPI in complex with 2-phosphoglyceric acid (2-PGA). Both TPIs fold into a dimeric (β-α)8 barrel in which the dimer interface consists of α-helices 2, 3, and 4, and swapping of loop 3. TPIs from parasitic helminths harbor a region of three amino acids knows as the SXD/E insert (S155 to E157 and S157 to D159 in TsTPI and SmTPI, respectively). This insert is located between α5 and β6 and is proposed to be the main TPI epitope. This region is part of a solvent-exposed 310–helix that folds into a hook-like structure. The crystal structures of TsTPI and SmTPI predicted conformational epitopes that could be used for vaccine design. Surprisingly, the epitopes corresponding to the SXD/E inserts are not the ones with the greatest immunological potential. SmTPI, but not TsTPI, habors a sole solvent exposed cysteine (SmTPI-S230) and alterations in this residue decrease catalysis. The latter suggests that thiol-conjugating agents could be used to target SmTPI. In sum, the crystal structures of SmTPI and TsTPI are a blueprint for targeted schistosomiasis and cysticercosis drug and vaccine development.

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<![CDATA[Polymer-fiber-coupled field-effect sensors for label-free deep brain recordings]]> https://www.researchpad.co/article/N12f161cb-ce31-436b-989e-fa44b0a6dffa

Electrical recording permits direct readout of neural activity but offers limited ability to correlate it to the network topography. On the other hand, optical imaging reveals the architecture of neural circuits, but relies on bulky optics and fluorescent reporters whose signals are attenuated by the brain tissue. Here we introduce implantable devices to record brain activities based on the field effect, which can be further extended with capability of label-free electrophysiological mapping. Such devices reply on light-addressable potentiometric sensors (LAPS) coupled to polymer fibers with integrated electrodes and optical waveguide bundles. The LAPS utilizes the field effect to convert electrophysiological activity into regional carrier redistribution, and the neural activity is read out in a spatially resolved manner as a photocurrent induced by a modulated light beam. Spatially resolved photocurrent recordings were achieved by illuminating different pixels within the fiber bundles. These devices were applied to record local field potentials in the mouse hippocampus. In conjunction with the raster-scanning via the single modulated beam, this technology may enable fast label-free imaging of neural activity in deep brain regions.

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<![CDATA[BioJava 5: A community driven open-source bioinformatics library]]> https://www.researchpad.co/article/5c6730bad5eed0c484f37fa8

BioJava is an open-source project that provides a Java library for processing biological data. The project aims to simplify bioinformatic analyses by implementing parsers, data structures, and algorithms for common tasks in genomics, structural biology, ontologies, phylogenetics, and more. Since 2012, we have released two major versions of the library (4 and 5) that include many new features to tackle challenges with increasingly complex macromolecular structure data. BioJava requires Java 8 or higher and is freely available under the LGPL 2.1 license. The project is hosted on GitHub at https://github.com/biojava/biojava. More information and documentation can be found online on the BioJava website (http://www.biojava.org) and tutorial (https://github.com/biojava/biojava-tutorial). All inquiries should be directed to the GitHub page or the BioJava mailing list (http://lists.open-bio.org/mailman/listinfo/biojava-l).

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<![CDATA[A specialized MreB-dependent cell wall biosynthetic complex mediates the formation of stalk-specific peptidoglycan in Caulobacter crescentus]]> https://www.researchpad.co/article/5c5df35ad5eed0c48458119b

Many bacteria have complex cell shapes, but the mechanisms producing their distinctive morphologies are still poorly understood. Caulobacter crescentus, for instance, exhibits a stalk-like extension that carries an adhesive holdfast mediating surface attachment. This structure forms through zonal peptidoglycan biosynthesis at the old cell pole and elongates extensively under phosphate-limiting conditions. We analyzed the composition of cell body and stalk peptidoglycan and identified significant differences in the nature and proportion of peptide crosslinks, indicating that the stalk represents a distinct subcellular domain with specific mechanical properties. To identify factors that participate in stalk formation, we systematically inactivated and localized predicted components of the cell wall biosynthetic machinery of C. crescentus. Our results show that the biosynthesis of stalk peptidoglycan involves a dedicated peptidoglycan biosynthetic complex that combines specific components of the divisome and elongasome, suggesting that the repurposing of preexisting machinery provides a straightforward means to evolve new morphological traits.

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<![CDATA[Temporal evolution and pathway models of poly(ethylene-terephthalate) degradation under multi-factor accelerated weathering exposures]]> https://www.researchpad.co/article/5c70673ad5eed0c4847c6c71

Photolytic and hydrolytic degradation of poly(ethylene-terephthalate) (PET) polymers with different stabilizers were performed under multiple accelerated weathering exposures and changes in the polymers were monitored by various evaluation techniques. Yellowing was caused by photolytic degradation and haze formation was induced by combined effects of photolytic and hydrolytic degradation. The formation of light absorbing chromophores and bleaching of the UV stabilizer additive were recorded through optical spectroscopy. Chain scission and crystallization were found to be common mechanisms under both photolytic and hydrolytic conditions, based on the infrared absorption of the carbonyl (C = O) band and the trans ethylene glycol unit, respectively. The degradation mechanisms determined from these evaluations were then used to construct a set of degradation pathway network models using the network structural equation modeling (netSEM) approach. This method captured the temporal evolution of degradation by assessing statistically significant relationships between applied stressors, mechanistic variables, and performance level responses. Quantitative pathway equations provided the contributions from mechanistic variables to the response changes.

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<![CDATA[Water-induced strong protection against acute exposure to low subzero temperature of adult Aedes albopictus]]> https://www.researchpad.co/article/5c61e909d5eed0c48496f6ed

As an important vector of dengue and Zika, Aedes albopictus has been the fastest spreading invasive mosquitoes in the world over the last 3–4 decades. Cold tolerance is important for survival and expansion of insects. Ae. albopictus adults are generally considered to be cold-intolerant that cannot survive at subzero temperature. However, we found that Ae. albopictus could survive for several hours’ exposure to -9 to -19 oC so long as it was exposed with water. Median lethal time (LT50) of Ae. albopictus exposed to -15 and -19 oC with water increased by more than 100 times compared to those exposed to the same subzero temperature without water. This phenomenon also existed in adult Aedes aegypti and Culex quinquefasciatus. Ae. albopictus female adults which exposed to low subzero temperature at -9 oC with water had similar longevity and reproductive capacity to those of females without cold exposure. Cold exposure after a blood meal also have no detrimental impact on survival capacity of female adult Ae. albopictus compared with those cold exposed without a blood meal. Moreover, our results showed that rapid cold hardening (RCH) was induced in Ae. albopictus during exposing to low subzero temperature with water. Both the RCH and the relative high subzero temperature of water immediate after cold exposure might provide this strong protection against low subzero temperature. The molecular basis of water-induced protection for Ae. albopictus might refer to the increased glycerol during cold exposure, as well as the increased glucose and hsp70 during recovery from cold exposure. Our results suggested that the water-induced strong protection against acute decrease of air temperature for adult mosquitoes might be important for the survival and rapid expansion of Ae. albopictus.

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<![CDATA[Synthesis and characterizations of o-nitrochitosan based biopolymer electrolyte for electrochemical devices]]> https://www.researchpad.co/article/5c706761d5eed0c4847c6f87

For the past decade, much attention was focused on polysaccharide natural resources for various purposes. Throughout the works, several efforts were reported to prepare new function of chitosan by chemical modifications for renewable energy, such as fuel cell application. This paper focuses on synthesis of the chitosan derivative, namely, O-nitrochitosan which was synthesized at various compositions of sodium hydroxide and reacted with nitric acid fume. Its potential as biopolymer electrolytes was studied. The substitution of nitro group was analyzed by using Attenuated Total Reflectance Fourier Transform Infra-Red (ATR-FTIR) analysis, Nuclear Magnetic Resonance (NMR) and Elemental Analysis (CHNS). The structure was characterized by X-ray Diffraction (XRD) and its thermal properties were examined by using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Whereas, the ionic conductivity of the samples was analyzed by electrochemical impedance spectroscopy (EIS). From the IR spectrum results, the nitro group peaks of O-nitrochitosan, positioned at 1646 and 1355 cm-1, were clearly seen for all pH media. At pH 6, O-nitrochitosan exhibited the highest degree of substitution at 0.74 when analyzed by CHNS analysis and NMR further proved that C-6 of glucosamine ring was shifted to the higher field. However, the thermal stability and glass transition temperatures were decreased with acidic condition. The highest ionic conductivity of O-nitrochitosan was obtained at ~10−6 cm-1. Overall, the electrochemical property of new O-nitrochitosan showed a good improvement as compared to chitosan and other chitosan derivatives. Hence, O-nitrochitosan is a promising biopolymer electrolyte and has the potential to be applied in electrochemical devices.

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<![CDATA[Physical assessment, spectroscopic and chemometric analysis of starch-based foils with selected functional additives]]> https://www.researchpad.co/article/5c6dc9cdd5eed0c48452a1f6

The paper presents the results of studies related to the impact of functional additives in the form of polylactide (PLA), polyvinyl alcohol (PVA), and keratin hydrolysate (K) on the physical characteristics of biopolymer foils. TPS granulate was obtained using a TS-45 single-screw extruder with L/D = 16. Foil was produced with the use of an L/D = 36 extruder with film-blowing section. The impact of the quantity and type of the functional additives on the processing efficiency and energy consumption of granulate extrusion, as well as the physical characteristics of the foil produced: thickness, basis weight, and colour were determined. By measuring the FTIR spectra it was determined the type and origin of the respective functional groups. It was observed that foils produced from granulates with the addition of 3% PVA were characterised by the lowest thickness and basis weight. Addition of 2 and 3% of PLA increased thickness and basis weight of starch-based foils significantly. Increasing the content of keratin in SG/K samples resulted in a decrease of brightness and intensify the yellow tint of foils, especially when 2 and 3% of keratin was used. In terms of the other samples, it was observed that the colour remained almost unchanged irrespective of the percentage content of the additive used. Infrared analyses conducted on foil containing PVA, PLA, and K revealed a change in spectra intensity in the frequency range associated with–OH groups originating from the forming free, intra- and intermolecular hydrogen bonds. Based on an analysis of the respective bands within the IR range it was also concluded that considerable structural changes took place with respect to the glycosidic bonds of starch itself. The application of the mentioned additives had a significant structural impact on the produced starch-based foils. Furthermore, the conducted UV-Vis analyses revealed a substantial increase in absorbance and a related reduction of the permeability (colour change) of the obtained materials in the range of ultraviolet and visible light.

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<![CDATA[Biophysical and structural characterization of a zinc-responsive repressor of the MarR superfamily]]> https://www.researchpad.co/article/5c6c75e4d5eed0c4843d0401

The uptake of zinc, which is vital in trace amounts, is tightly controlled in bacteria. For this control, bacteria of the Streptococcaceae group use a Zn(II)-binding repressor named ZitR in lactococci and AdcR in streptococci, while other bacteria use a Zur protein of the Ferric uptake regulator (Fur) superfamily. ZitR and AdcR proteins, characterized by a winged helix-turn-helix DNA-binding domain, belong to the multiple antibiotic resistance (MarR) superfamily, where they form a specific group of metallo-regulators. Here, one such Zn(II)-responsive repressor, ZitR of Lactococcus lactis subspecies cremoris strain MG1363, is characterized. Size Exclusion Chromatography-coupled to Multi Angle Light Scattering, Circular Dichroism and Isothermal Titration Calorimetry show that purified ZitR is a stable dimer complexed to Zn(II), which is able to bind its two palindromic operator sites on DNA fragments. The crystal structure of ZitR holo-form (Zn(II)4-ZitR2), has been determined at 2.8 Å resolution. ZitR is the fourth member of the MarR metallo-regulator subgroup whose structure has been determined. The folding of ZitR/AdcR metallo-proteins is highly conserved between both subspecies (cremoris or lactis) in the Lactococcus lactis species and between species (Lactococcus lactis and Streptococcus pneumoniae or pyogenes) in the Streptococcaceae group. It is also similar to the folding of other MarR members, especially in the DNA-binding domain. Our study contributes to better understand the biochemical and structural properties of metallo-regulators in the MarR superfamily.

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<![CDATA[Aggregation and interfacial phenomenon of amphiphilic drug under the influence of pharmaceutical excipients (green/biocompatible gemini surfactant)]]> https://www.researchpad.co/article/5c648cbcd5eed0c484c81680

In the current study, we have examined the interaction amongst an antidepressant drug amitriptyline hydrochloride (AMH) and ethane-1, 2-diyl bis(N,N-dimethyl-N-cetylammoniumacetoxy) dichloride (16-E2-16, a green gemini surfactant) through tensiometric and fluorimetric techniques in aqueous/electrolyte/urea solutions. Significant variations are observed in the various evaluated parameters in the present study. Gemini 16-E2-16 has outstanding surface properties along with a much lower cmc value, demonstrating very little toxicity as well as considerable antimicrobial activity. The cmc values of mixtures decrease through increase in mole fraction (α1) of 16-E2-16, which specifies the nonideality of the solution mixtures, along with demonstrating the occurrence of mixed micellization too. Negative βRub values signify on the whole attractive force of interaction between constituents of mixed micelles. Owing to the incidence of electrolyte NaCl (50 mmol.kg–1), lowering of the micelles’ surface charge happens, resulting in aggregation taking place at lower concentration while the presence of urea (NH2CONH2) halts micellization taking place, which means the cmc value increases in the attendance of urea. The ΔGmo values for all systems were negative along with the presence of electrolyte/urea. The excess free energy (Gex) of studied mixed systems was also estimated and found to be negative for all the systems. Using the fluorescence quenching method, the micelle aggregation number (Nagg) was evaluated and it was found that the contribution of gemini surfactant was always more than that of the AMH and their value enhances in the existence of electrolyte while decreasing in the attendance of NH2CONH2 in the system. In addition, other fluorescence parameters such as micropolarity (I1/I3), dielectric constant (Dexp) as well as Stern–Volmer binding constants (Ksv) of mixed systems were evaluated and the results showed the synergistic performance of the AMH + 16-E2-16 mixtures. Along with tensiometric and fluorimetric techniques, FT-IR spectroscopy was also engaged to reveal the interaction among constituents.

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<![CDATA[Microplastics in Mediterranean Sea: A protocol to robustly assess contamination characteristics]]> https://www.researchpad.co/article/5c6b267ad5eed0c484289b52

The study of microplastic pollution involves multidisciplinary analyses on a large number of microplastics. Therefore, providing an overview of plastic pollution is time consuming and, despite high throughput analyses, remains a major challenge. The objective of this study is to propose a protocol to determine how many microplastics must be analyzed to give a representative view of the particle size distribution and chemical nature, and calculate the associated margin error. Based on microplastic data from Tara Mediterranean campaign, this approach is explained through different examples. In this particular case, the results show that only 3% of the collected microplastics need to be analyzed to give a precise view on the scale of the North West Mediterranean Basin (error <5%), and 17.7% to give an overview manta per manta (error <10%). This approach could be an important practical contribution to microplastic studies.

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<![CDATA[Isolated diastolic potentials as predictors of success in ablation of right ventricular outflow tract idiopathic premature ventricular contractions]]> https://www.researchpad.co/article/5c648cdbd5eed0c484c8196e

Background and aims

Discrete potentials, low voltage and fragmented electrograms, have been previously reported at ablation site, in patients with premature ventricular contractions (PVCs) originating in the right ventricular outflow tract (RVOT). The aim of this study was to review the electrograms at ablation site and assess the presence of diastolic potentials and their association with success.

Methods

We retrospectively reviewed the electrograms obtained at the radiofrequency (RF) delivery sites of 48 patients subjected to ablation of RVOT frequent PVCs. We assessed the duration and amplitude of local electrogram, local activation time, and presence of diastolic potentials and fragmented electrograms.

Results

We reviewed 134 electrograms, median 2 (1–4) per patient. Success was achieved in 40 patients (83%). At successful sites the local activation time was earlier– 54 (-35 to -77) ms vs -26 (-12 to -35) ms, p<0.0001; the local electrogram had lower amplitude 1 (0.45–1.15) vs 1.5 (0.5–2.1) mV, p = 0.006, and longer duration 106 (80–154) vs 74 (60–90) ms, p<0.0001. Diastolic potentials and fragmented electrograms were more frequently present, respectively 76% vs 9%, p <0.0001 and 54% vs 11%, p<0.0001. In univariable analysis these variables were all associated with success. In multivariable analysis only the presence of diastolic potentials [OR 15.5 (95% CI: 3.92–61.2; p<0.0001)], and the value of local activation time [OR 1.11 (95% CI: 1.049–1.172 p<0.0001)], were significantly associated with success.

Conclusion

In this group of patients the presence of diastolic potentials at the ablation site was associated with success.

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<![CDATA[Inhibition of the Staphylococcus aureus c-di-AMP cyclase DacA by direct interaction with the phosphoglucosamine mutase GlmM]]> https://www.researchpad.co/article/5c50c481d5eed0c4845e8843

c-di-AMP is an important second messenger molecule that plays a pivotal role in regulating fundamental cellular processes, including osmotic and cell wall homeostasis in many Gram-positive organisms. In the opportunistic human pathogen Staphylococcus aureus, c-di-AMP is produced by the membrane-anchored DacA enzyme. Inactivation of this enzyme leads to a growth arrest under standard laboratory growth conditions and a re-sensitization of methicillin-resistant S. aureus (MRSA) strains to ß-lactam antibiotics. The gene coding for DacA is part of the conserved three-gene dacA/ybbR/glmM operon that also encodes the proposed DacA regulator YbbR and the essential phosphoglucosamine mutase GlmM, which is required for the production of glucosamine-1-phosphate, an early intermediate of peptidoglycan synthesis. These three proteins are thought to form a complex in vivo and, in this manner, help to fine-tune the cellular c-di-AMP levels. To further characterize this important regulatory complex, we conducted a comprehensive structural and functional analysis of the S. aureus DacA and GlmM enzymes by determining the structures of the S. aureus GlmM enzyme and the catalytic domain of DacA. Both proteins were found to be dimers in solution as well as in the crystal structures. Further site-directed mutagenesis, structural and enzymatic studies showed that multiple DacA dimers need to interact for enzymatic activity. We also show that DacA and GlmM form a stable complex in vitro and that S. aureus GlmM, but not Escherichia coli or Pseudomonas aeruginosa GlmM, acts as a strong inhibitor of DacA function without the requirement of any additional cellular factor. Based on Small Angle X-ray Scattering (SAXS) data, a model of the complex revealed that GlmM likely inhibits DacA by masking the active site of the cyclase and preventing higher oligomer formation. Together these results provide an important mechanistic insight into how c-di-AMP production can be regulated in the cell.

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<![CDATA[A comparison of emulsion stability for different OSA-modified waxy maize emulsifiers: Granules, dissolved starch, and non-solvent precipitates]]> https://www.researchpad.co/article/5c648d0bd5eed0c484c81df8

This work investigates the stability of emulsions prepared by using octenyl succinic anhydride (OSA)-modified waxy maize starch in the form of granules, dissolved starch, and non-solvent precipitated starch as Pickering emulsion stabilisers. The aim of this study was to investigate the effects of different forms of starches on the stability of emulsion using light microscopy, light scattering, and static multiple light scattering. All starch samples were hydrophobically modified with 3% (w/w) n-octenyl succinyl anhydride (OSA). Starch polymer solutions were prepared by dissolving OSA- modified starch in water in an autoclave at 140°C. Non-solvent precipitates were obtained through ethanol precipitation of dissolved waxy maize. The stability of the oil/water emulsions were different for the three forms of starches used. The granule-based emulsions were unstable, with only a small proportion of the granules adsorbed onto oil droplets, as viewed under a light microscope. The emulsions were observed to cream after 2 hours. The dissolved starch and non-solvent precipitate-based emulsions were stable towards creaming for months, and they had almost 100% emulsifying index (EI = 1) by visual observation and EI ~ 0.9 by multiple light scattering measurements. The results from light microscopy and multiple light scattering measurements indicated the occurrence of coalescence for all three types of emulsions. The coalescence was fastest within days for the granule stabilised system while it was slower both for the dissolved starch and non-solvent precipitate-based emulsions. The latter demonstrated the least degree of coalescence over time. Thus, it was concluded that differences in starch particle size and molecular structure influenced the emulsion droplet size and stability. A decreased particle size correlates to a decrease in droplet size, thus increasing stabilisation against creaming. However, stability towards coalescence was low for the large granules but was best for the non-solvent precipitate starch indicating that there is a window of optimal particle size for stability. Thus, best emulsifying properties were obtained with the non-solvent precipitates (~ 120 nm particle size) where the emulsions remained stable after one year of storage. In conclusion, this study illustrated the potentiality of non-solvent precipitated starch as emulsion stabilizers.

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<![CDATA[Drought stress affects the protein and dietary fiber content of wholemeal wheat flour in wheat/Aegilops addition lines]]> https://www.researchpad.co/article/5c633936d5eed0c484ae624e

Wild relatives of wheat, such as Aegilops spp. are potential sources of genes conferring tolerance to drought stress. As drought stress affects seed composition, the main goal of the present study was to determine the effects of drought stress on the content and composition of the grain storage protein (gliadin (Gli), glutenin (Glu), unextractable polymeric proteins (UPP%) and dietary fiber (arabinoxylan, β-glucan) components of hexaploid bread wheat (T. aestivum) lines containing added chromosomes from Ae. biuncialis or Ae. geniculata. Both Aegilops parents have higher contents of protein and β-glucan and higher proportions of water-soluble arabinoxylans (determined as pentosans) than wheat when grown under both well-watered and drought stress conditions. In general, drought stress resulted in increased contents of protein and total pentosans in the addition lines, while the β-glucan content decreased in many of the addition lines. The differences found between the wheat/Aegilops addition lines and wheat parents under well-watered conditions were also manifested under drought stress conditions: Namely, elevated β-glucan content was found in addition lines containing chromosomes 5Ug, 7Ug and 7Mb, while chromosomes 1Ub and 1Mg affected the proportion of polymeric proteins (determined as Glu/Gli and UPP%, respectively) under both well-watered and drought stress conditions. Furthermore, the addition of chromosome 6Mg decreased the WE-pentosan content under both conditions. The grain composition of the Aegilops accessions was more stable under drought stress than that of wheat, and wheat lines with the added Aegilops chromosomes 2Mg and 5Mg also had more stable grain protein and pentosan contents. The negative effects of drought stress on both the physical and compositional properties of wheat were also reduced by the addition of these. These results suggest that the stability of the grain composition could be improved under drought stress conditions by the intraspecific hybridization of wheat with its wild relatives.

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<![CDATA[New interfaces on MiD51 for Drp1 recruitment and regulation]]> https://www.researchpad.co/article/5c5ca2b5d5eed0c48441e93f

Mitochondrial fission is facilitated by dynamin-related protein Drp1 and a variety of its receptors. However, the molecular mechanism of how Drp1 is recruited to the mitochondrial surface by receptors MiD49 and MiD51 remains elusive. Here, we showed that the interaction between Drp1 and MiD51 is regulated by GTP binding and depends on the polymerization of Drp1. We identified two regions on MiD51 that directly bind to Drp1, and found that dimerization of MiD51, relevant to residue C452, is required for mitochondrial dynamics regulation. Our Results have suggested a multi-faceted regulatory mechanism for the interaction between Drp1 and MiD51 that illustrates the potentially complicated and tight regulation of mitochondrial fission.

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<![CDATA[R pyocin tail fiber structure reveals a receptor-binding domain with a lectin fold]]> https://www.researchpad.co/article/5c633948d5eed0c484ae63f5

R pyocins are ɸCTX-like myophage tailocins of Pseudomonas sp. Adsorption of R pyocins to target strains occurs by the interaction of tail fiber proteins with core lipopolysaccharide (LPS). Here, we demonstrate that N-terminally truncated R pyocin tail fibers corresponding to a region of variation between R-subtypes are sufficient to bind target strains according to R-subtype. We also report the crystal structures of these tail fiber proteins and show that they form an elongated helical trimer composed of three domains arranged linearly from N- to C-terminus: a baseplate proximal head, medial shaft, and distal foot. The head and shaft domains contain novel structural motifs. The foot domain, however, is composed of a conserved jellyroll fold and shares high structural similarity to the tail fiber of myophage AP22, podophage tailspike C-terminal domains (LKA-1 and ɸ297), and several eukaryotic adhesins (discoidin I/II, agglutinin, and octocoral lectin). Many of these proteins bind polysaccharides by means of their distal loop network, a series of highly variable loops at one end of the conserved jellyroll fold backbone. Our structures reveal that the majority of R-subtype specific polymorphisms cluster in patches covering a cleft formed at the oligomeric interface of the head domain and in a large patch covering much of the foot domain, including the distal loop network. Based on the structural variation in distal loops within the foot region, we propose that the foot is the primary sugar-binding domain of R pyocins and R-subtype specific structural differences in the foot domain distal loop network are responsible for binding target strains in an R-subtype dependent manner.

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