Turbidity Measurements Research Articles

The Kings River Experimental Watersheds: Infrastructure and data

AbstractThe Kings River Experimental Watersheds (KREW) were established in 2002 to expand our knowledge of catchment physical, chemical, and biological processes in Sierra Nevada headwater forests, and to better understand the impacts of prescribed burning and forest thinning on these processes. Two elevation strata (high and low) were selected for the KREW sites, with four independent catchments and one nested catchment within each stratum. Both high and low elevation study areas were instrumented for continuous measurements of meteorology, streamflow, and turbidity. Atmospheric and stream chemistry, suspended sediment concentration, and bedload sediment delivery were measured on a regular schedule. Soil chemical and physical properties and vegetation were systematically sampled before and after the initial thinning and prescribed burning treatments, which were implemented between 2012 and 2016. Post‐treatment data collection continues today as we explore opportunities for the second round of possible treatments. The critical research infrastructure and long‐term baseline data collection has been instrumental in building partnerships with downstream managers, end users, non‐governmental organizations, academic researchers, and national research programmes. Contributions to date include fundamental understanding of magnitude and variability of nutrient deposition; carbon, nutrient, and major ion dynamics in headwater streams; aquatic algae and macroinvertebrate populations; vegetation composition and structure; and streamflow responses to precipitation in the two elevation strata. Data from the experimental watersheds also support calibration and validation of diverse hydrologic models used for water resources planning.

Comparison of Time Resolved Optical Turbidity Measurements for Water Monitoring to Standard Real-Time Techniques.

Environmental water monitoring requires the estimation of the suspended solids load. In this paper, we compare the concentration range accessible through three different techniques: optical turbidity, acoustic backscattering and the newly in-lab developed time resolved optical turbidity. We focus on their comparison on measurements made in the laboratory on water suspensions of known particles and concentrations. We used laboratory grade kieselguhr, wheat starch and kaolin as suspended solid surrogates. The explored concentration domains are the ones, for the total suspended solid load, commonly encountered in wastewater and rivers in standard (less than 1 g/L to a few g/L) or extreme conditions such as floods or storm events (up to several dozen g/L). Regarding the operable concentration domain, the time resolved optical turbidity shows a clear advantage upon the other methods, whatever the kind of particle is.

Temperature- and Composition-Induced Multiarchitectural Transitions in the Catanionic System of a Conventional Surfactant and a Surface-Active Ionic Liquid

The mixture of the cationic surfactant, cetyltrimethylammonium bromide (CTAB), and anionic surface-active ionic liquid, 1-butyl-3-methylimidazoliumdodecyl sulfate (bmimDS), has been studied as a function of the mole fraction of CTAB, XCTAB, with the total surfactant concentration fixed at 50 mM using turbidity measurements, rheology, dynamic light scattering, differential scanning calorimetry, small-angle neutron scattering, and small-angle X-ray scattering techniques. The catanionic mixture has been found to exhibit phase transitions from vesicles to micelles as a function of temperature, with some mole fractions of CTAB showing dual transitions. Solutions of XCTAB = 0.2 to 0.5 exhibited a single transition from vesicles to cylindrical micelles at 45 °C. With an increase in the mole fraction of CTAB from 0.55 to 0.65, dual structural transitions at 30 and 45 °C were observed. The microstructural transition at 30 °C is ascribed to the vesicle aggregation process with smaller vesicles fusing into bigger ones, whereas the transition at 45 °C was evaluated to be the vesicle-to-cylindrical micelle transition. However, at higher mole fractions of CTAB, XCTAB from 0.65 to 0.90, a single transition from vesicles to small cylindrical/spherical micelles was observed in the solutions, at a lower temperature of 30 °C. To the best of our knowledge, such a microstructural transitions as a function of temperature in a single mixture of cationic and anionic surfactants without any additive has not been reported so far.

Tannin: An eco-friendly depressant for the green flotation separation of hematite from quartz

Reverse cationic flotation is the most known beneficiation method for the separation of fine hematite particles from silicates. In this process, the depression of the hematite surface is an essential factor. Thus, the development of environmentally friendly depressants plays a critical role. Tannin (TA) as a natural and eco-friendly organicreagent has not yet been considered for such a purpose. Through the reverse cationic flotation, the depression effect of TA was investigated by single and mixture of minerals. Micro-flotation tests and wettability analysis based on contact angle measurements by the captive bubble method (CBM) were conducted. The surface adsorption mechanism of TA on the hematite and quartz was explored through turbidity, zeta-potential measurements, surface adsorption tests, and Fourier transform infrared (FT-IR) analyses. The micro-flotation results indicated that TA could selectively depress more than 90% of hematite, while its effect on quartz floatability was negligible (<8% depressing). Surface wettability analysis demonstrated that TA in the presence of 30 mg/L collector could significantly increase the work of adhesion of hematite from 135.5 to 143.1 erg/cm2, whereas it increased the work of adhesion of quartz from 117.1 to 120.7 erg/cm2. Surface adsorption analysis depicted that in the presence of 100 mg/L TA, the adsorption amount of TA on the hematite surface was 0.99 mg/g, while this amount for quartz was 0.17 mg/g (around 6 times lower than hematite). Turbidity measurements, applied to clarify the aggregation – dispersion behavior of pure minerals in the TA presence, showed that TA had a dispersion effect on the quartz particles, whereas TA caused hematite aggregation. Surface analyses proved that TA selective adsorption occurred on the hematite surface mainly by chemisorption. In contrast, poor physical adsorption was the main interaction between TA and the quartz surface.

Inhibitory effect of naturally occurring Ocimum sanctum extract on α-Synuclein aggregation in aqueous solution

α-Synuclein (α-Syn) has a propensity to form amyloids and is one of the major causes of neurodegenerative disorders like Parkinson’s disease (PD). Despite a lot of research, there is no obviating therapy available for PD and related disorders. Therefore, discovering new inhibitors against α-Syn aggregation is a subject of intense research. Against this backdrop, we have investigated the attenuating effect of naturally occurring Ocimum sanctum (OS) against aggregation in aqueous solution using various biochemical and biophysical studies. In this report, Thioflavin (ThT) and Congo red binding assays have shown the hindering effect of OS extract on β-sheet formation in α-Syn, and eventually leading to inhibition of aggregation. ANS binding assay indicated its modulatory effect on hydrophobic patches of α-Syn protein. SDS-PAGE, turbidity measurement, and light scattering assays indicated the role of OS extract in increasing protein solubility. Morphological studies conducted by TEM and DLS suggested that OS extract prevents the formation of large fibrils. This work also extends to reveal the inhibitory and disaggregation effects of OS extract on A53T mutant induced aggregation and pre-existing fibrils respectively. Also, MTT assay implied the protective effect of OS extract on neuroblastoma cells against fibril induced cytotoxicity. Furthermore, docking studies of α-Syn with different molecules of OS extract navigated for putative interacting amino acid residues. Thus, due to the presence of polyphenolic compounds, OS extract binds with α-Syn and inhibits its aggregation. This study implicates that OS extract and associated molecules may become a potential therapeutic intervention against PD and other aggregation related disorders.

Optimal Spatiotemporal Scales to Aggregate Satellite Ocean Color Data for Nearshore Reefs and Tropical Coastal Waters: Two Case Studies

Remotely sensed ocean color data are useful for monitoring water quality in coastal environments. However, moderate resolution (hundreds of meters to a few kilometers) satellite data are underutilized in these environments because of frequent data gaps from cloud cover and algorithm complexities in shallow waters. Aggregating satellite data over larger space and time scales is a common method to reduce data gaps and generate a more complete time series, but potentially smooths out the small-scale, episodic changes in water quality that can have ecological influences. By comparing aggregated satellite estimates of Kd(490) with related in-water measurements, we can understand the extent to which aggregation methods are viable for filling gaps while being able to characterize ecologically relevant water quality conditions. In this study, we tested a combination of six spatial and seven temporal scales for aggregating data from the VIIRS instrument at several coral reef locations in Maui, Hawai‘i and Puerto Rico and compared these with in situ measurements of Kd(490) and turbidity. In Maui, we found that the median value of a 5-pixels, 7-days spatiotemporal cube of satellite data yielded a robust result capable of differentiating observations across small space and time domains and had the best correlation among spatiotemporal cubes when compared with in situ Kd(490) across 11 nearshore sites (R2 = 0.84). We also found long-term averages (i.e., chronic condition) of VIIRS data using this aggregation method follow a similar spatial pattern to onshore turbidity measurements along the Maui coast over a three-year period. In Puerto Rico, we found that the median of a 13-pixels, 13-days spatiotemporal cube of satellite data yielded the best overall result with an R2 = 0.54 when compared with in situ Kd(490) measurements for one nearshore site with measurement dates spanning 2016–2019. As spatiotemporal cubes of different dimensions yielded optimum results in the two locations, we recommend local analysis of spatial and temporal optima when applying this technique elsewhere. The use of satellite data and in situ water quality measurements provide complementary information, each enhancing understanding of the issues affecting coastal ecosystems, including coral reefs, and the success of management efforts.

Dynamics of Hyporheic Exchange Flux and Fine Particle Deposition Under Moving Bedforms

AbstractDeposition of fine suspended particles can reduce hyporheic exchange flux (HEF), which may result in impairment of various ecological processes. However, the dynamics of fine particle deposition and streambed clogging are still not well understood, especially when the bed is in motion. We conducted flume experiments to study the effects of coupled sand‐clay dynamics on HEF with episodic (pulse) inputs of suspended kaolinite. Three experiments with a mobile sand bed and constant discharge were conducted with repeated injection of suspended kaolinite pulses at fixed concentration increments of 0.16, 0.41, and 0.66 g/L, respectively. HEF and participating porewater volume were assessed using tracer tests. Kaolinite deposition rates were inferred from turbidity measurements while deposition patterns were measured using core samples. We found that fine sediment primarily accumulated within a layer below the bedform scour zone, and that this layer was thicker when kaolinite was added in larger pulses. HEF declined linearly over time as kaolinite accumulated in the bed sediment; an increase of 0.1% kaolinite in the bed led to a decrease in HEF of 26.6 cm/day, regardless of the pulse concentration. However, the same kaolinite increase led to a reduction of 50% in participating pore volume for larger kaolinite pulses, versus only 30% for the smallest pulse. These results indicate that clogging occurs not just during and after high‐flow events, but also under constant flow conditions in which episodic deposition of suspended clay by HEF leads to the formation of a low‐conductivity layer in the bed.

Research on the possibility of using loading materials to support the treatment of reservoir waters

The article presents the issues related to of the removal of suspensions and sediments from reservoir waters. In the conducted research, particular emphasis was placed on the techniques of using loading materials in the water treatment process. The research materials were four types of reservoir water, which was collected from the separators of wells exploiting natural gas deposits. These waters were characterized by high suspended solids (76–176 mg/dm3) and a varied degree of mineralization. The content of dissolved substances was determined in the range from 401 to 306 428 mg/dm3. The extracted reservoir waters are currently most often utilized by pumping into the absorbing horizons in depleted hydrocarbon reservoirs. The preparation of water for injection is limited only to the removal of easily settling solid particles and suspensions present in the extracted formation waters. The porosity and permeability of the deposit rocks determine the size of solid particles present in the water that can be forced into voids in the porous medium. In the process of water treatment by coagulation and flocculation, carried out in laboratory conditions, Flokor ASW was used as a coagulant, while Stabpol was used as a flocculant. Post-coagulation sludge is highly hydrated, so that its density is close to that of water, as a result of which sedimentation of sludge particles takes a long time. In order to increase the sedimentation rate of particles contained in the treated waters, ballasting materials, which were quartz sand and bentonites: powdery bentonite and bentonite preparation DuoBent 1, were successively introduced into the solutions. The effectiveness of the water treatment process was assessed by comparing the degree of turbidity of the solution above the sediment before and after adding a different amount of coagulant, flocculant and sediment-balancing materials. The turbidity measurement of the tested solutions allows to estimate the content of suspensions and colloids in them. Laboratory tests were carried out on the possibility of using selected materials ballasting suspensions in the process of reservoir water treatment. Effective doses of ballast materials recommended for use in the separation of suspensions from formation waters were determined. Research results presented in this paper show that the removal of suspended solids from formation waters can be carried out with the use of a properly prepared bentonite agent (DuoBent 1) with no need of adding other chemical compounds. The doses of the DuoBent 1 bentonite preparation, dosed into highly mineralized reservoir waters in order to remove turbidity, are relatively small. Adding bentonite into the treated waters in amounts exceeding 0.2 g/dm3 results in obtaining high clarity of the water intended for injection (turbidity at the level of 0–5 FAU). The results of the research can be implemented for practical use as a simple method of purifying reservoir water prior to injection into the formation.

Особенности временной изменчивости содержания кислорода в зарослях Zostera marina Linnaeus, 1753 в бухте Воевода (Амурский залив, Японское море)

В настоящее время мелководные бассейны с лугами Zostera marina L. рассматривают в качестве поглотителей атмосферного углекислого газа, способных сдерживать увеличение его концентрации. Благодаря своей высокой продуктивности взморник выделяет в среду большое количество кислорода. Для установления особенностей проявления продукционной активности мелководных бассейнов, покрытых лугами Z. marina, на примере бухты Воевода (Амурский залив, Японское море) проведён мониторинг гидрологических и продукционных параметров с различными интервалами измерений. Наблюдения продолжались 8,5 мес. (22.09.2012–07.06.2013). В зарослях Z. marina на глубине 4 м измеряли температуру, солёность, флуоресценцию хлорофилла и мутность с помощью гидрологической станции Water Quality Monitor с интервалом 3 часа. Малоинерционным оптическим кислородным датчиком ARO-USB определяли концентрацию растворённого кислорода с интервалом 1 час. Установлено два типа изменчивости содержания кислорода в среде: 1) долгопериодная изменчивость, обусловленная сезонными изменениями среды; 2) суточная в период ледостава, определяемая интенсивностью проникновения фотосинтетически активной радиации в подлёдную воду. В осенний сезон отмечены низкие концентрации кислорода, достигающие уровня гипоксии. Для зимнего и весеннего периодов содержание кислорода находилось, как правило, на уровне 100–130 % от насыщения. Высокую суточную изменчивость наблюдали в период ледостава, в отсутствие снега. В феврале амплитуда суточных колебаний концентрации кислорода достигала 730 мкмоль·кг−1, с трёхкратным пересыщением по отношению к атмосферному O2. Установлено, что максимальная скорость продукции кислорода, отнесённая к 1 г сырой массы Z. marina, составляет 6,5 мг O2·час−1·г−1. Суточная динамика кислорода в морской воде проанализирована в связи с физиологическими особенностями Z. marina (воздухоносные полости в побегах играют важную роль в динамике кислорода в среде), а также в связи с короткопериодными приливами.

Phenylalanine-Tethered pH-Responsive Poly(2-Hydroxyethyl Methacrylate).

A series of pH-responsive random copolymers comprised of 2-hydroxyethyl methacrylate (HEMA) and tert-butyl carbamate (Boc)-protected phenylalanine methacryloyloxyethyl ester (Boc-Phe-EMA) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization in N,N'-dimethylformamide (DMF) at 70 °C. The synthesized copolymers were comprehensively characterized using a combination of techniques, including 1 H NMR, FT-IR spectroscopy and size exclusion chromatography (SEC). Reactivity of each monomers towards controlled radical polymerization was evaluated by determining the reactivity ratios by virtue of extended Kelen-Tüdös method at high conversions revealed the higher reactivity of non-modified HEMA (rHEMA =1.03) in contrast to Boc-Phe-EMA (rBoc-Phe-EMA =0.48). Furthermore, the expulsion of the Boc-groups resulted copolymers with ionizable pendant primary ammonium and hydroxyl groups. To understand the glass transition behaviours of homo- and co-polymers, differential scanning calorimetric (DSC) measurements were carried out. The effect of HEMA content on the pH-sensitivity of the copolymers in aqueous medium was investigated through turbidity measurements. Finally, the counteranion exchange from trifluoroacetate to chloride provided copolymers with enhanced water solubility and unaltered phase transition pH.

Evaluation of the flocculation and dewatering performance of dual polymers for treating oil sands tailings

AbstractMature fine tailings produced in the processing of oil sands create serious water‐recovery problems; thus, it is important to characterize them and to improve the applicable dewatering technologies. Existing methods to dewater the tailings are found to be insufficient. Previous research has demonstrated that the addition of dual polymers is more efficient than using a single polymer to flocculate the fine tailings particles. Different from studies that took sophisticated procedures to assess the flocculation and dewatering efficiency of dual polymers, readily available and simple but effective experiments were conducted in this work. Evaluations were conducted with dual polymers comprised of low molecular weight poly(diallydimethylammonium chloride) (polyDADMAC) and high molecular weight cationic or anionic polyacrylamide (PAM). Turbidity and residual solids measurements for dewatered tailings treated with these polymers confirmed that the dual‐polymer approach yield superior performance compared to either polymer functioning alone. Zeta potential and microscopic observations indicated that the dosages of polyDADMAC and PAM that lead to near charge neutralization of the system result in maximal performance. We hypothesize that when dual polymers are added to the tailings, polyDADMAC acts to neutralize the charge and destabilize the fine particles, while high molecular weight PAM, either cationic or anionic, acts to aggregate the destabilized fines by the bridging mechanism. PolyDADMAC forms weak and tiny flocs when mixed with tailings particles. Cationic PAM transforms these small flocs into much larger ones, while anionic PAM connects them into aggregates. Therefore, synergism exists between polyDADMAC and PAM but this synergism is different, based on the charge of the PAM.

Design of azobenzene-bearing hydrogel with photoswitchable mechanics driven by photo-induced phase transition for in vitro disease modeling

Mechanics of the extracellular matrix (ECM) exhibit changes during many biological events. During disease progression, such as cancer, matrix stiffening or softening occurs due to crosslinking of the collagen matrix or matrix degradation through cell-secreted enzymes. Engineered hydrogels have emerged as a prime in vitro model to mimic such dynamic mechanics during disease progression. Although there have been a variety of engineered hydrogels, few can offer both stiffening and softening properties under the same working principle. In addition, to model individual disease progression, it is desirable to control the kinetics of mechanical changes. To this end, we describe a photoresponsive hydrogel that undergoes stiffness changes by the photo-induced phase transition. The hydrogel was composed of a copolymer of azobenzene acrylate monomer (AzoAA) and N,N-dimethyl acrylamide (DMA). By tuning the amount of azobenzene, the phase transition behavior of this polymer occurs solely by light irradiation, because of the photoisomerization of azobenzene. This phase behavior was confirmed at 37 °C by turbidity measurements. In addition, the crosslinked poly(AzoAA-r-DMA) gel undergoes reversible swelling-deswelling upon photoisomerization by ultraviolet or visible light. Furthermore, the poly(AzoAA-r-DMA) sheet gels exhibited modulus changes at different isomerization states of azobenzene. When MCF-7 cells were cultured on the gels, stiffening at different timepoints induced varied responses in the gene expression levels of E-cadherin. Not only did this suggest an adaptive behavior of the cells against changes in mechanics during disease progression, this also demonstrated our material's potential towards in vitro disease modeling. Statement of significanceDuring disease progression such as cancer, cellular microenvironment called extracellular matrix (ECM) undergoes stiffness changes. Hydrogels, which are swollen network of crosslinked polymers, have been used to model such dynamic mechanical environment of the ECM. However, few could offer both stiffening and softening properties under the same working principle. Herein, we fabricated a novel photoresponsive hydrogel with switchable mechanics, activated by photo-induced structural change of the polymer chains within the hydrogel. When breast cancer cells were cultured on our dynamic hydrogels, gene expression and morphological observation suggested that cells react to changes in stiffness by a transient response, as opposed to a sustained one. The photoresponsive hydrogel offers possibility for use as a patient-specific model of diseases.

Improved Heat Stability of Whey Protein Isolate by Glycation with Inulin

Glycation between proteins and sugars via the Maillard reaction has been shown to improve the heat stability of proteins. In this study, inulin, a healthy dietary fiber, was glycated with whey protein isolate (WPI), and the effects of reaction conditions were investigated. Conjugates were prepared by freeze-drying mixed WPI and inulin solutions at 1:1 to 6:1 WPI-to-inulin weight ratios followed by dry heating at 70, 75, or 80 °C for 12 to 72 h under uncontrolled, 44%, or 80% relative humidity. Heat stability was evaluated by turbidity, particle size, and rheological measurements. Degree of glycation was assessed by quantifying the loss of amino groups and the formation of the Amadori compounds. Results showed that conjugation led to improved heat stability, as shown by decreased turbidity and particle size as well as the ability to maintain the viscosity compared to control samples. Based on the loss of amino groups, the optimum glycation conditions were achieved with WPI–inulin mixtures at 2:1, 4:1, and 6:1 weight ratios and 80 °C temperature for 12 to 72 h without controlling the relative humidity. The improved heat stability could be due to an increase in negative charge as well as increased structural stabilization of the proteins. Under a limited degree of glycation, glycated WPI–inulin conjugates have great potential to be utilized as food ingredients, especially in the beverage industry.

Rapid Determination of Emulsion Stability Using Turbidity Measurement Incorporating Artificial Neural Network (ANN): Experimental Validation Using Video/Optical Microscopy and Kinetic Modeling.

Determination of emulsion stability has important applications in crude oil production, separation, and transportation. The turbidimetry method offers advantage of rapid determination of stability at a relatively low cost with good accuracy. In this study, the stability of an oil-in-water (O/W) emulsion prepared by dispersing heavy oil particles in the aqueous solution containing poly(vinyl alcohol) (PVA) has been determined using turbidity measurements. The turbidimetry theory of emulsion stability has been validated using experimental data of turbidity at different wavelengths (350–800 nm) and storage times (0–300 min). The artificial neural network (ANN) has been found to give good predictive performance of the turbidity data. The characteristic change in turbidity has been supported using particle size and distribution analyses performed using optical/video microscopy. The results obtained from the turbidimetry correlation show that the emulsion destabilization rate constant (κ′, min–1) is in the range of 0.01–0.04 min–1 (at wavelengths between 350 and 800 nm, respectively). The rate constant remains unchanged (κ′ = 0.02 min–1) between the wavelength of 375 and 650 nm. In addition, the demulsification rate constant (κ′ = 0.015 min–1) obtained from kinetic modeling using the bottle test is in close agreement with this value. The overall findings ultimately revealed that the turbidimetry method could be used to determine stability of typical O/W emulsions with an acceptable level of accuracy.

Femtosecond pulsed laser microscopy: a new tool to assess the in vitro delivered dose of carbon nanotubes in cell culture experiments

BackgroundIn vitro models are widely used in nanotoxicology. In these assays, a careful documentation of the fraction of nanomaterials that reaches the cells, i.e. the in vitro delivered dose, is a critical element for the interpretation of the data. The in vitro delivered dose can be measured by quantifying the amount of material in contact with the cells, or can be estimated by applying particokinetic models. For carbon nanotubes (CNTs), the determination of the in vitro delivered dose is not evident because their quantification in biological matrices is difficult, and particokinetic models are not adapted to high aspect ratio materials. Here, we applied a rapid and direct approach, based on femtosecond pulsed laser microscopy (FPLM), to assess the in vitro delivered dose of multi-walled CNTs (MWCNTs).Methods and resultsWe incubated mouse lung fibroblasts (MLg) and differentiated human monocytic cells (THP-1) in 96-well plates for 24 h with a set of different MWCNTs. The cytotoxic response to the MWCNTs was evaluated using the WST-1 assay in both cell lines, and the pro-inflammatory response was determined by measuring the release of IL-1β by THP-1 cells. Contrasting cell responses were observed across the MWCNTs. The sedimentation rate of the different MWCNTs was assessed by monitoring turbidity decay with time in cell culture medium. These turbidity measurements revealed some differences among the MWCNT samples which, however, did not parallel the contrasting cell responses. FPLM measurements in cell culture wells revealed that the in vitro delivered MWCNT dose did not parallel sedimentation data, and suggested that cultured cells contributed to set up the delivered dose. The FPLM data allowed, for each MWCNT sample, an adjustment of the measured cytotoxicity and IL-1β responses to the delivered doses. This adjusted in vitro activity led to another toxicity ranking of the MWCNT samples as compared to the unadjusted activities. In macrophages, this adjusted ranking was consistent with existing knowledge on the impact of surface MWCNT functionalization on cytotoxicity, and might better reflect the intrinsic activity of the MWCNT samples.ConclusionThe present study further highlights the need to estimate the in vitro delivered dose in cell culture experiments with nanomaterials. The FPLM measurement of the in vitro delivered dose of MWCNTs can enrich experimental results, and may refine our understanding of their interactions with cells.

Simple Regulation of the Self-Assembling Ability by Multimerization of Elastin-Derived Peptide (FPGVG) n Using Nitrilotriacetic Acid as a Building Block.

Elastin comprises hydrophobic repetitive sequences, such as Val-Pro-Gly-Val-Gly, which are thought to be important for the temperature-dependent reversible self-association (coacervation). Elastin and elastin-like peptides (ELPs), owing to their characteristics, are expected to be applied as base materials for the development of new molecular tools, such as drug-delivery system carrier and metal-scavenging agents. Recently, several studies have been reported on the dendritic or branching ELP analogues. Although the topological difference of the branched ELPs compared to their linear counterparts may lead to useful properties in biomaterials, the available information regarding the effect of branching on molecular architecture and thermoresponsive behavior of ELPs is scarce. To obtain further insight into the thermoresponsive behavior of branched ELPs, novel ELPs, such as nitrilotriacetic acid (NTA)–(FPGVG)n conjugates, that is, (NTA)-Fn analogues possessing 1–3 (FPGVG)n (n = 3, 5) molecule(s), were synthesized and investigated for their coacervation ability. Turbidity measurement of the synthesized peptide analogues revealed that (NTA)-Fn analogues showed strong coacervation ability with various strengths. The transition temperature of NTA-Fn analogues exponentially decreased with increasing number of residues. In the circular dichroism measurements, trimerization did not alter the secondary structure of each peptide chain of the NTA-Fn analogue. In addition, it was also revealed that the NTA-Fn analogue possesses one peptide chain that could be utilized as metal-scavenging agents. The study findings indicated that multimerization of short ELPs via NTA is a useful and powerful strategy to obtain thermoresponsive molecules.

Complex coacervation of pea protein isolate and tragacanth gum: Comparative study with commercial polysaccharides

The ability of pea protein isolates (PPI) to form complex coacervates with tragacanth gum was investigated. The coacervate formation was structurally compared to three other PPI-polysaccharide interaction models: arabic gum and sodium alginate (known to form coacervates with PPI) and tara gum, a galactomannan. The effects of the pH and protein/polysaccharide ratio were mainly investigated using turbidity and zeta potential measurements. Regarding the pH of soluble complex formation, the pH of complex coacervates increased with the increase in protein-anionic polysaccharide mixture ratio. SEM images revealed the ability of the spray-drying process to form spherical particles of pea protein-polysaccharide complexes. The specificity of the microparticle surface was protein-dependent. FTIR analyses of coacervates showed the electrostatic interaction between the PPI and the polysaccharides. The results showed that tragacanth gum could be used as an alternative to gum arabic to form complex coacervates with PPI based on zeta potential measurements and coacervation yield studies.

Effect of electrostatic interactions and complexes formation between nisin and bacterial exopolysaccharides on nisin antimicrobial efficacy

This study aims to describe interactions that may occur between nisin and bacterial exopolysaccharides (EPS) when they are present together in a model solution. For this purpose, two EPS, namely EPS-GM and EPS-BMS, produced by potential probiotic Bacillus tequilensis-GM and Leuconostoc citreum-BMS, respectively, were used. Results showed that maximal complexation occurred at pH 5.0 between anionic EPS (1.5 g/L) and cationic nisin (1 g/L) mainly through electrostatic interactions. Results provided by scanning electron microscopy, epifluorescence microscopy and turbidity measurements showed that EPS-GM was able to form bigger and higher amounts of complexes with nisin. The nisin antimicrobial activity was interestingly not affected and even improved after its complexation with EPS suggesting that these latter may act as protective agents of the nisin antimicrobial activity when applied in foods. The results of this study should help food technologists to optimize the physicochemical conditions for optimal formulation of food products containing EPS.

Complex coacervation of carboxymethyl konjac glucomannan and ovalbumin and coacervate characterization

Carboxymethyl konjac glucomannan (CMKGM) is an anionic derivative of konjac glucomannan (KGM). Its coacervation with ovalbumin (OVA) was investigated through turbidity and coacervate yield measurements and the resultant CMKGM-OVA coacervates were characterized as a function of phase separation pH. The results indicated that CMKGM could coacervate with OVA in pHs ranging from 2.0 to 4.5. OVA to CMKGM mass ratios higher than 1:1 led to insoluble coacervates, while lower ratios conferred soluble complexes. NaCl suppressed the interaction between CMKGM and OVA and could resuspend their precipitated coacervates. The interaction between the two polyelectrolytes was not affected in temperatures ranging from 25 °C to 55 °C, but was weakened in higher temperatures. The coacervation increased the thermal stability and induced structural changes in both the polyelectrolytes. Atomic force microscope observation revealed that the CMKGM-OVA coacervates separated in mass ratio 1:1 was not susceptible to aggregation, and quartz crystal microbalance with dissipation analysis demonstrated that OVA exhibited the strongest absorption towards CMKGM in pH 3.0 in multilayer mode. Hence, CMKGM is a promising polyelectrolyte for coacervation with proteins and could be used in the construction of targeted delivery systems through the electrostatic interaction with oppositely charged biopolymers.

Using Continuous Turbidity and Seismic Measurements to Unravel Sediment Provenance and Interaction Between Suspended and Bedload Transport in an Alpine Catchment

AbstractFine sediment transport results from the complexity of the interactions between the different modes of transport and the variety of possible sediment sources, from the river bed stocks remobilization to hillslopes erosion. From a 2‐year period in an Alpine catchment, we show how the combined use of continuous turbidity and seismic measurements can help to address these issues. In the studied catchment, the signals are more strongly correlated during the high flows of the snowmelt period than during the summer period when the river bed is stable and the hillslopes are no longer protected by a snow cover during storms. This sheds light on the seasonal control exerted by the river bed mobility and the snow cover on suspended sediment dynamics in mountainous catchments. It also questions the potential shift of this dynamics from river bed to hillslope dominated in a context of global warming.