Search

Background Salt-soluble myofibrillar proteins (MPs) form the major protein component of meat and have several advantages over plant-derived proteins, including high digestibility and the presence of all the essential amino acids. However, MPs are not widely used because the presence of myosin filaments limits their functionality in low ionic strength media. Hence, an approach for effectively inhibiting or disrupting the formation of myosin filaments is a challenging issue in the development of novel meat protein based products. Scope and approach To develop a strategy for inhibiting or destroying the formation of myosin filaments, an understanding of the process of myosin self-association is needed at the molecular level. Hence, the present review systematically elaborates the assembly mechanism of myosin filaments and its relation to the functionality of MPs. Additionally, the review focuses on the description of several chemical and physical strategies, with an emphasis on advantages, disadvantages, and recent progress. Key findings and conclusions The assembly of myosin into filaments has been shown to be mediated by sequentially distributed charges in the myosin tail. Moreover, the dissociation of myosin filaments, leading to improved functional properties of the MPs, has been demonstrated by amino acid treatment, glycation, high-intensity ultrasonication (HIU), and high-pressure homogenization (HPH) in low ionic strength media. Nevertheless, these strategies still face a number of limitations and, hence, further research is needed in order to achieve large-scale industrial production. In addition, the enhanced development of novel meat protein based products requires a consideration of the thermal stability of MPs throughout the entire process from product sterilization through to preservation and consumption.

This review article provides a critical survey of work from 1904 to 2003 on the effects of low ionic strength in Red Blood Cells (RBCs) incubated in media with impermeable sugars such as sucrose. In 1904 Gürber A washed RBCs of different species with isotonic sucrose solution to eliminate the outside ions in order to better analyse their intracellular ionic composition; however, this approach was not feasible because of a substantial salt efflux from the cells. A prominent feature of the salt loss is the shrinking of the RBCs. A central role in the understanding of the ionic movements is thereby the new Donnan equilibrium of the anions. Experimental evidence has been given by Jacobs MH and Parpart AK in 1933. In the sucrose medium two phases could be predicted: 1) a very rapid anionic shift resulting in an unequal distribution of chloride and hydroxyl anions on both sides of the membrane and 2) a leakage of salts from the RBCs. In 1940 Wilbrandt W assumed that a positive membrane potential is in line with the salt loss at low ionic strength in RBCs. In 1977 Knauf PA, Fuhrmann GF, Rothstein S and Rothstein A observed in RBCs an inhibition of both, anion exchange and also of net anion efflux, by incubation with disulfonic stilbene derivates. At low ionic strength the Donnan equilibrium is immediately obtained by the Anion Exchanger Protein (AEP). The resulting positive membrane potential opens at least two new types of cation pores or channels. Thereby is the conductivity pathway for the anions, namely the AEP, in charge of the net anion loss at low ionic strength. The AEP pathway is extensively blocked by disulfonic stilbene compounds. The permeability ways for cations through these pores or channels are not yet explored.

A large number of researchers have endeavored to delineate the effects of injecting brine with a low ionic strength in oil reservoirs in the past decade. However, we still cannot conclude the overr...

It has been well known that Vibrio cholerae inhabit in environmental water. As many patients infected with cholera toxin-producing V. cholerae O1 (toxigenic V. cholerae O1) emerge in Kolkata, India, it has been thought that toxigenic V. cholerae O1 is easily detected in environmental water in Kolkata. However, we could not isolate toxigenic V. cholerae O1 from environmental water in Kolkata, though NAG Vibrio (generic name of V. cholerae non-O1/non-O139) is constantly detected. To clear the reason for the non-isolation of toxigenic V. cholerae O1, we examined the viability of V. cholera O1 and NAG Vibrios in the artificial low ionic strength aquatic solution. We found that the viability of toxigenic V. cholerae O1 in the solution is low, but that of NAG Vibrios is high. Subsequently, we examined the viability of NAG Vibrios possessing cholera toxin gene (ctx) in the same condition and found that the viability of these NAG Vibrios is low. These results indicate that the existence of ctx in V. cholerae affects the viability of V. cholerae in the aquatic solution used in this experiment. We thought that there was closely relation between the low viability of toxigenic V. cholerae O1 in the artificial low ionic strength aquatic solution and the low frequency of isolation of the strain from environmental water.

In this work, three triazine-type compounds were studied for their solubilities in aqueous and saline environments. Using potentiometric titration and gravimetric methods, the solubility of cyanuri...

To analyze the physicochemical properties of rabbit glycated myofibrillary protein (GMP) with different solubility ((15.10 ± 0.76)%, (35.03 ± 1.01)%, (55.06 ± 1.25)%, and (75.07 ± 1.86)%) in low ionic strength medium, the changes in SDS-PAGE, foaming properties, emulsifying properties, gelling properties, rheological properties, and thermal stability under different pH conditions were determined. The results indicated that GMP with (75.07 ± 1.86)% solubility had better foaming and emulsifying properties than GMP with (35.03 ± 1.01)% solubility at pH 6.0 and pH 7.5 did; however, GMP with (75.07 ± 1.86)% solubility had lower gel strength and showed more cracks in gel networks. Furthermore, the storage modulus (G′) of GMP increased as the solubility increased within the range of (15.10 ± 0.76)% to (35.03 ± 1.01)%, but decreased after the solubility reached (55.06 ± 1.25)%. Results also suggested that the glycation process can improve the thermal stability of myofibrillary protein; GMP with (75.07 ± 1.86)% solubility had the highest denaturation temperature. In conclusion, the physicochemical properties of rabbit GMP were affected by changes in solubility in low ionic strength medium; rabbit GMP with high solubility was more resistant to pH changes than native myofibrillary protein.

Binding of tetracationic porphyrin (TMPyP4+) to poly(rA) has been studied in neutral buffered solution of low ionic strength in a wide range of molar phosphate-to-dye ratios (P/D) using absorption ...

Expansion Microscopy (ExM) significantly improves the resolution of conventional diffraction-limited optical microscopy by using physically expanding biological samples. Combining ExM with single molecule localization microscopy (SMLM) could further enhance the resolving power of SMLM, which is typically on the order of 20-30 nm. However, to make this combination successful, we need to solve three key issues related to sample preparation, including mainly hydrogel shrinking in ionic photoswitching buffer, fluorescence photobleaching due to free-radical reaction and reduced labelling efficiency from protease digestion. Using polyacrylamide gel re-embedding or improved photoswitching buffer with low ionic strength are able to minimize or even solve the hydrogel shrinking problem, while the development of post-expansion labelling approaches avoids fluorescence bleaching. However, the preservation of protein epitopes (which determines the labelling efficiency) remains to be challenging. In this paper, we propose to tackle this challenge by inserting the highly selective and stable biotin-streptavidin interaction into the post-expansion labelling strategy. After upgrading the popular immunolabelling linkage scheme from Epitope-Primary antibody-Secondary antibody-Fluorophores to Epitope-Primary antibody-Secondary antibody-Biotin-Streptavidin-Fluorophores, we are able to label protein epitopes with Biotin, which is stable during the expansion process, and thus avoid the troublesome problem in preserving protein epitopes or antibody. We demonstrate that combining Ex-SMLM with the new post-expansion linkage scheme enables new possibility in resolving the detailed arrangement of the Nup133 proteins in nuclear pore complex, which helps researchers observe a clearer structure. This study provides new chances for studying the ultrastructural details of subcellular organelles or even biomacromolecules, using conventional SMLM system.

Due to the interaction of fertilizers with microplastics (MPs) and porous media, fertilization process would influence MPs transport and distributions in soil. The co-impacts of N fertilizers (both inorganic and organic N fertilizers) and humic substance on MPs transport/retention behaviors in porous media were examined in 10 mM KCl solutions at pH 6. NH4Cl and CO(NH2)2 were employed as inorganic and organic N fertilizers, respectively, while humic acid (HA) was used as model humic substance. We found that for all three sized MPs (0.2, 1 and 2 μm) without HA, both types of N fertilizers decreased their transport/increased their retention in porous media (both quartz sand and soil). N fertilizers adsorbed onto surfaces of MPs and sand/soil, lowering the electrostatic repulsion between MPs and porous media, thus contributed to the enhanced MPs deposition. MPs with N fertilizers in solutions more tightly attached onto porous media and thus were more difficult to be re-mobilized via low ionic strength solution elution. Via steric repulsion and increasing electrostatic repulsion between MPs and porous media due to adsorption onto their surfaces, HA could increase MPs transport with N fertilizers in solutions.

An interlaboratory test of pH measurements in rainwater has been conducted. Various types of electrodes and junction materials were used in this test. The results of this exercise verify that there are significant differences in the pH values of low ionic strength solutions reported by various laboratories. Other work suggests that these differences are due to residual liquid junction potentials. Furthermore, this test confirms the efficacy of using dilute solutions of a strong acid as working standards for pH measurements in acid deposition studies.

The assembly reaction of Escherichia coli ferritin A (EcFtnA) was studied using time-resolved small-angle X-ray scattering (SAXS). EcFtnA forms a cage-like structure that consists of 24 identical subunits and dissociates into dimers at acidic pH. The dimer maintains native-like secondary and tertiary structures and can reassemble into a 24-mer when the pH is increased. The time-dependent changes in the SAXS profiles of ferritin during its assembly were roughly explained by a simple model in which only tetramers, hexamers, and dodecamers were considered intermediates. The rate of assembly increased with increasing ionic strength and decreased with increasing pH (from pH 6 to pH 8). These tendencies might originate from repulsion between assembly units (dimers) with the same net charge sign. To test this hypothesis, ferritin mutants with different net charges (net-charge mutants) were prepared. In buffers with low ionic strength, the rate of assembly increased with decreasing net charge. Thus, repulsion between the assembly unit net charges was an important factor influencing the assembly rate. Although the differences in the assembly rate among net-charge mutants were not significant in buffers with an ionic strength higher than 0.1, the assembly rates increased with increasing ionic strength, suggesting that local electrostatic interactions are also responsible for the ionic-strength dependence of the assembly rate and are, on average, repulsive.

The objective of the present study was to establish a culture of Hyalella azteca that could be used for laboratory toxicity testing in low–ionic strength waters with electrical conductivities of

High intensity ultrasound (HIU) effects on soy 7S proteins in various pH (pH = 3.0 and 7.0) and ionic strengths (I = 0.1, 0.3 and 0.5) were investigated. When dissolved in pH = 7.0, the 7S proteins formed aggregates at the low ionic strength (I = 0.1), while large aggregates were dissociated as the ionic strengths increased (I = 0.3 or 0.5) after HIU treatments. Moreover, the 7S proteins were unfolded at I = 0.3 and I = 0.5 through HIU. When dissolved in pH = 3.0, the 7S proteins were extensively positively charged, which favored the HIU-induced denaturation of the proteins. When the ionic strengths were increased, the larger aggregates of the proteins were found after HIU. The electrostatic screening from the ions was essential for the unfolding/refolding and aggregating behavior of the HIU proteins, which was also proved from the structural measurements. The current study illustrated that environmental factors were of great importance for the HIU effects on food protein functionalities.

Most techniques allow detection of protein unfolding either by following the behaviour of single reporters or as an averaged all-or-none process. We recently added 2D NMR spectroscopy to the well-established techniques able to obtain information on the process of unfolding using resonances of residues in the hydrophobic core of a protein. Here, we questioned whether an analysis of the individual stability curves from each resonance could provide additional site-specific information. We used the Yfh1 protein that has the unique feature to undergo both cold and heat denaturation at temperatures above water freezing at low ionic strength. We show that stability curves inconsistent with the average NMR curve from hydrophobic core residues mainly comprise exposed outliers that do nevertheless provide precious information. By monitoring both cold and heat denaturation of individual residues we gain knowledge on the process of cold denaturation and convincingly demonstrate that the two unfolding processes are intrinsically different.

The use of monoclonal antibodies (mAbs) for the treatment of a variety of diseases is rapidly growing each year. Many mAbs are administered intravenously using i.v. bags containing 0.9% NaCl (normal saline). We studied the aggregation propensity of these antibody solutions in saline and compared it with a low ionic strength formulation buffer. The mAb studied in this work is prone to aggregate, and is known to form a viscoelastic network at the air-solution interface. We observed that this interfacial elasticity increased when formulated in saline. In the bulk, the mAbs exhibited a tendency to self-associate that was higher in saline. We also studied the aggregation of the mAbs in the presence of polysorbate-20, typically added to formulations to mitigate interfacial aggregation. We observed that with surfactants, the presence of salt in the buffer led to a greater mAb adsorption at the interface and resulted in the formation of more particulate aggregates. Our results show that the addition of salt to the buffer led to differences in the interfacial aggregation in mAb formulations, showing that stress studies used to screen for mAb aggregation intended for i.v. administration should be performed in conditions representative of their intended route of administration.

International audience; Only a limited and scattered knowledge is currently available on the conditions leading to the occurrence of sampling alteration at low ionic strength (

Directionality switching of the mitotic kinesin-5 Cin8 motor is caused by an asymmetric response of its active movement to drag., Directed active motion of motor proteins is a vital process in virtually all eukaryotic cells. Nearly a decade ago, the discovery of directionality switching of mitotic kinesin-5 motors challenged the long-standing paradigm that individual kinesin motors are characterized by an intrinsic directionality. The underlying mechanism, however, remains unexplained. Here, we studied clustering-induced directionality switching of the bidirectional kinesin-5 Cin8. Based on the characterization of single-molecule and cluster motility, we developed a model that predicts that directionality switching of Cin8 is caused by an asymmetric response of its active motion to opposing forces, referred to as drag. The model shows excellent quantitative agreement with experimental data obtained under high and low ionic strength conditions. Our analysis identifies a robust and general mechanism that explains why bidirectional motor proteins reverse direction in response to seemingly unrelated experimental factors including changes in motor density and molecular crowding, and in multimotor motility assays.

We report the adsorption characteristics and mechanisms of a strong polyanion, poly(styrenesulfonate), PSS, onto α-Al2O3 with large size (L-Al2O3) and small size (S-Al2O3) in this paper. Some effective conditions to the adsorption of PSS onto L-Al2O3 and S-Al2O3 such as adsorption time, pH, mass ratio of PSS to α-Al2O3, and ionic strength were systematically studied. Maximum adsorption capacities of PSS onto both L-Al2O3 and S-Al2O3 were achieved with adsorption time 120 min, mass ratio of PSS to α-Al2O3 20 mg/g, and ionic strength 50 mM NaCl. The PSS adsorption onto S-Al2O3 significantly decreased with increasing pH from 4 to 9 while PSS adsorption onto L-Al2O3 decreased insignificantly in the pH range 4–9. Adsorption of PSS onto both L-Al2O3 and S-Al2O3 increased with increasing salt from 0 to 50 mM NaCl, indicating that electrostatic and none-lectrostatic interactions controlled adsorption at low ionic strength. However, adsorption of PSS was independent on the ionic strength at salt concentration higher than 50 mM. The changes in surface charge after PSS adsorption onto L-Al2O3 and S-Al2O3 were determined by zeta potential while the differences of surface functional groups before and after PSS adsorption were characterized by Fourier-transform infrared spectroscopy (FT-IR). The zeta potential as a function of the mass ratio of PSS to L-Al2O3 and S-Al2O3 agreed well with the adsorption capacity against the mass ratio. Adsorption mechanisms of PSS onto L-Al2O3 and S-Al2O3 were also discussed based on the changes in zeta potential, the differences of surface functional groups, and adsorbed amount as a function of the mass ratio of PSS to α-Al2O3.

The cellulose nanocrystals (LSCNC) and nanofibrils (LSCNF) from lemon seeds were isolated, characterized and used to co-stabilize Pickering emulsions under different LSCNC/LSCNF ratio. The ratio of LSCNC and LSCNF obviously influenced the appearance and microstructure of emulsions. At a fixed total nanocellulose concentration (1 wt%), the LSCNC/LSCNF stabilized emulsions showed a gradual worsening performance with the increase of LSCNF proportion. However, at a fixed LSCNC concentration (0.5 wt%), as LSCNF addition increased from 0 wt% to 1 wt%, the droplet sizes of emulsions gradually decreased, and the viscoelasticity and stability of emulsions increased correspondingly. The obtained emulsions displayed a good pH and ionic strength stability. Notably, introducing LSCNF made LSCNC stabilize emulsions even at low ionic strength (

The qualitative characteristics of meat products are closely related to the functionality of muscle proteins. Myofibrillar proteins (MPs), comprising approximately 50% of total muscle proteins, are generally considered to be insoluble in solutions of low ionic strength (0.2 M), requiring high concentrations of salt (0.3 M) for solubilization. These soluble proteins are the ones which determine many functional properties of meat products, including emulsification and thermal gelation. In order to increase the utilization of meat and meat products, many studies have investigated the solubilization of MPs in water or low ionic strength media and determining their functionality. However, there still remains a lack of systematic information on the functional properties of MPs solubilized in this manner. Hence, this review will explore some typical techniques that have been used. The main procedures used for their solubilization, the fundamental principles and their functionalities in water (low ionic strength medium) are comprehensively discussed. In addition, advantages and disadvantages of each technique are summarized. Finally, future considerations are presented to facilitate progress in this new area and to enable water soluble muscle MPs to be utilized as novel meat ingredients in the food industry.

The bovine whey protein β-lactoglobulin will self-assemble into amyloid-like nanofibrils when heated at pH ≤ 3 and temperatures ≥75 °C. These fibrils have diameters

Liquid-liquid phase separation (LLPS) of a monoclonal antibody solution was investigated at low ionic strength in the presence of oligovalent anions, such as citrate, trimellitate, pyromellitate and mellitate. Phase separation was observed at the isoelectric point of the antibody at pH8.7 as well as in more acidic pH regions in the presence of the tested oligovalent ions. This can be attributed to charge neutralization via binding of the oligovalent anions to the positively charged antibody. The influence of the anion concentration on liquid-liquid phase separation with respect to the net charge of the antibody was examined. Similarities to the formation of a complex coacervate were shown to apply. These findings enable us to understand the usage of excipients to rationally induce or avoid liquid-liquid phase separation at low ionic strength. Furthermore we present a method to directly examine the competition of different ions for the solvation shell, called buffer equilibration.

It has been regarded that Vibrio cholerae O1 inhabit in environmental water. As many cholera patients emerge in Kolkata, it has been thought that V. cholerae O1 is easily detected in environmental water in Kolkata. However, the detection of V. cholerae O1 is rare, though other V. cholerae (NAG Vibrio) is constantly detected. To clear the reason for the difference of the detection rate of two Vibrios, we examined the viability of V. cholera O1 and NAG Vibrios in low ionic strength aquatic medium. We observed greater declining viability of V. cholerae O1 possessing cholera toxin gene (ctx) in low ionic strength solution, but the decline of NAG Vibrios non-possessing ctx is small. To evaluate the concerning of ctx in the viability, we examined the viabilities of V. cholerae O1which do not possess ctx and NAG Vibrios possessing ctx under the same condition. The result indicated that the existence of the ctx induces the decrease the viability of the host in low ionic strength solution. The decrease observed in this experiment might relate with the low detection of V. cholerae O1 possessing ctx in environmental water, though NAG Vibrio is constantly detected.

Lipobeads are spherical vesicles of lipid membrane supported by a hydrogel core that hold promise as next-generation biosensors. However, previous methods for generating lipobeads had limitations due to the use of organic solvents and low ionic strength solutions. To overcome these limitations, we developed a method for forming lipobeads by using a gel-assisted swelling approach. Our results show that lipobeads form in osmotic strength solution and supposed to contain no residual organic solvent.

It has been regarded that Vibrio cholerae O1 inhabit in environmental water. As many cholera patients emerge in Kolkata, it has been thought that V. cholerae O1 is easily detected in environmental water in Kolkata. However, the detection of V. cholerae O1 is rare, though other V. cholerae (NAG Vibrio) is constantly detected. To clear the reason for the difference of the detection rate of two Vibrios, we examined the viability of V. cholera O1 and NAG Vibrios in low ionic strength aquatic medium. We observed greater declining viability of V. cholerae O1 possessing cholera toxin gene (ctx) in low ionic strength solution, but the decline of NAG Vibrios non-possessing ctx is small. To evaluate the concerning of ctx in the viability, we examined the viabilities of V. cholerae O1which do not possess ctx and NAG Vibrios possessing ctx under the same condition. The result indicated that the existence of the ctx induces the decrease the viability of the host in low ionic strength solution. The decrease observed in this experiment might relate with the low detection of V. cholerae O1 possessing ctx in environmental water, though NAG Vibrio is constantly detected.

A sensitive assay for the functional activity of complement Factor I is described. This is based on its third proteolytic clip whereby Factor I cleaves cell-bound iC3b to cell-bound C3dg and soluble C3c, thereby abolishing conglutination of the cells. Factor H is required as a co-factor for Factor I activity. Because of the low affinity of iC3b for Factor H, the assay needs to be performed at low ionic strength. This assay is easier to perform than those based on the conversion of C3b to iC3b (the first two Factor I clips), there being no need for the unstable intermediate EAC142 or for purified C3.

The in-lab reproductive success of a strain of Hyalella azteca collected from Twin Lake, a water body located on the Canadian Nuclear Laboratories Chalk River Laboratories site, is sufficient to be used for effluent and (or) sediment toxicity assessments. This strain of Hyalella azteca enhances our capabilities to evaluate ecological risks in low ionic strength waters.

Impurities in indicator salts can significantly bias spectrophotometric pH determinations. In this work, two purified sulfonephthalein indicators, meta-cresol purple (mCP) and phenol red (PR), were tested for analysis of freshwater pH on the free hydrogen ion concentration scale. These two purified indicators were characterized for the first time under low ionic strength conditions, providing their molar absorption coefficients and dissociation constants along with their temperature dependence from 8 °C to 30 °C. At 25 °C, the infinite dilution constants ( pKIo) were determined to be 8.6606 and 8.0642 for mCP and PR, respectively. The accuracy and precision of the method, evaluated with a variety of buffers with known pH, were found to be +0.0014 pH units and ±0.0022 pH units, respectively (n = 30). The pH values of different freshwater samples were also determined using both indicators. The mCP and PR results were all within ± 0.01 pH units of each other with three out of seven pH differences within ± 0.001 pH units, indicating the high consistency between these two indicator methods. The work presented here is the first parallel comparison with two purified indicators used to determine pH of the same freshwater samples.

Summary The effects of 5 mm l-histidine (l-His) on water-binding capacity, gel strength, thermal gelling properties of chicken breast myofibrillar proteins (MPs) in 1 mm NaCl or 0.6 m NaCl solutions (pH 7.0) were investigated. l-His could significantly increase the solubility and thermal gelling ability of MPs in 1 mm NaCl. l-His at 1 mm NaCl shortened the water relaxation time and decreased the water mobility of MPs gel. l-His promoted the formation of MPs gel structure with small pores and thin strands at 1 mm NaCl. These resulted in the enhanced water retention and weak gel strength of MPs in low ionic strength solution. The water-binding capacity of MPs gels formed in 1 mm NaCl containing 5 mm l-His was equivalent to that with 0.6 m NaCl. The information could offer certain theoretical foundation to apply l-His as sodium salt substitute for developing low-salt meat gelling product with high yield.

The state of sodium humate in aqueous solution and on a solid surface is studied using various methods. It is shown that in aqueous solution at neutral pH and low ionic strength this substance exists in an associated state. The values of molecular mass of the molecules in the preparation studied (Aldrich) are determined to be 1, 3–6 and 15 kDa. A new adsorption-based approach for initial estimation of the molecular mass and size of humic acid molecules is proposed, which can be used instead of any specific sophisticated equipment. The size of the molecules of the studied preparation estimated in this way (in the range of 2.3 to 9.0 nm), agree well with data obtained by chromatographic and electron microscopic measurements, which confirm the reliability of the proposed method.

Permeability tests of the compacted bentonite-sand mixture using salt solutions were carried out. Exposure of the Ca type-bentonite to NaCl or KCl solutions after fully saturation with deionized water caused ion exchange of the montmorillonite. After Ca ion exchanged to Na ion, the swelling pressure of the sample increased and the permeability decreased when the low ionic strength condition, comparing with the initial value before Na ion exchange. While, after Ca ion exchanged to K ion, increase in the swelling pressure and reduction of the permeability were insignificant. K and Na ions showed the different effect of ion exchange on the engineering properties of the bentonite.

Protoplasts are extensively employed in plant cellular biology to develop somatic hybrids with agronomically important traits. The success of cellular biotechnology for marine macroalgae is in its inception owing to lack of a simple unified protocol for protoplasts preparation. Previous studies have employed multiple enzymes, mostly crude enzymes prepared in the laboratory from either microbes or marine animals that were invariably a source of inconsistent results. This study reports a simple protocol with reproducible protoplast yields from Ulvophycean species, and the advantage includes the use of a single commercial enzyme at a much lower concentration in low ionic strength medium. In addition, the enzyme reusability was established five times for the first time without compromising on the protoplast yield and viability. Development of such a facile protocol will propel the application of protoplasts in cellular biotechnology of Ulvophyceaen species, which have nowadays gained considerable importance in food and energy perspective. Keywords: Enzyme, genetic modification, green seaweed, protoplast, Ulva

In this paper, new data are reported on the protonation of phytate at T = 298.15 K in different ionic media and ionic strengths, namely NH4Cl(aq) (0.1 ⩽ I/mol · kg−1 ⩽ 1.9) and NaNO3(aq) (0.1 ⩽ I/mol · kg−1 ⩽ 5.4). A complete set of phytate protonation constants, with general formula HiPhy (with 1 ⩽ i ⩽ 7) was proposed. The data were modeled by a logarithmic empiric equation, as well as an Extended Debye–Huckel (EDH) and specific ion interaction theory (SIT) models. A strong similarity was found between protonation data in NH4Cl(aq), NaNO3(aq) and those previously reported in NaCl(aq), KCl(aq) and KNO3(aq), so that an unique set of thermodynamic protonation data has been proposed for phytate protonation at I ⩽ 0.15 mol · kg−1. Thermodynamic parameters obtained in these conditions can be useful to model the behavior of phytate in real aqueous systems at low ionic strengths. An empirical relationship has also been proposed for all the protonation data at 0 < I/mol · kg−1 ⩽ 0.15: TΔS (±1.5) = 11.7 − 0.72 · ΔG. Using literature data for the phytate protonation in (C2H5)4NI(aq), the weak complexes between Na+ or NH4+ and phytic acid have been calculated by the ΔpK method (i.e., by the comparison of the protonation constants determined in an interacting medium, such as NH4Cl(aq), and those obtained in a non-interacting supporting electrolytes, like tetraalkylammonium salts). In terms of weak complex formation constants, the results are similar for NaNO3(aq) and NH4Cl(aq), and twelve HiMjPhy species are reported together with their stability. For example, for the formation of the M6Phy species, it is: log β = 25.9 and 25.6 (±0.2) for M = Na+ and NH4+, respectively, at I = 0.1 mol · dm−3. This paper represents an advance in the understanding of the acid-base behavior of phytic acid in a wide number of ionic media at different ionic strengths.

Calibration of pH meters is usually performed with reference pH buffer solutions of low ionic strength, I ≤ 0.1 mol kg−1. For seawater pH measurements (I ≈ 0.7 mol kg−1), calibration buffers in high ionic strength matrix are required. The Harned cell, in association with the Nernst equation and a model for estimating the chloride ion activity coefficient, $$\gamma_{{{\text{Cl}}^{ - } }} ,$$ is the basis of the primary method for pH assignment to reference pH buffers. The semi-empirical Pitzer model is, in principle, adequate to estimate $$\gamma_{{{\text{Cl}}^{ - } }}$$ of complex solutions, namely seawater. Nevertheless, no assessment of the validity of the model for this matrix is known to the authors. This work aims at estimating the adequacy of the Pitzer model by assessing the metrological compatibility of mean activity coefficients, in this case $$\gamma_{ \pm } = \sqrt {\gamma_{{{\text{H}}^{ + } }} \gamma_{{{\text{Cl}}^{ - } }} }$$ estimated experimentally with the Harned cell, $$\gamma_{ \pm }^{\text{Exp}} ,$$ and using the Pitzer model, $$\gamma_{ \pm }^{\text{Ptz}}$$ . The measurement uncertainty considered in the compatibility test was estimated using the bottom-up approach, where components were combined by the numerical Kragten method after checking its adequacy. The compatibility of the estimated $$\gamma_{ \pm }$$ was assessed for solutions with increasing complexity and an ionic strength of 0.67 mol kg–1. $$\gamma_{ \pm }^{\text{Exp}}$$ and $$\gamma_{ \pm }^{Ptz}$$ are metrologically compatible for a confidence level of 95 % where the relative standard uncertainty of their difference ranged from 1.1 % to 3.1 % in all chloride solutions to approximately 6.3 % when sodium sulfate was also present. This led to assume the validity of the Pitzer model equations to estimate $$\gamma_{{{\text{Cl}}^{ - } }} ,$$ required to define reference pH values of buffer solutions with high ionic strength.

Miniaturized matrix solid-phase dispersion (MSPD) followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) has been proposed for the simultaneous analysis of different classes of synthetic dyes in confectionery and cosmetics intended for or mostly consumed by children. Selected compounds include most of the permitted dyes as food additives as well as some of the most frequently used to color cosmetic products in accordance with the respective European directives. MSPD procedure was optimized by means of experimental design, allowing an effective, rapid and simple extraction of dyes with low sample and reagents consumption (0.1g of sample and 2mL of elution solvent). LC-MS/MS was optimized for good resolution, selectivity and sensitivity using a low ionic strength mobile phase (3mM NH4Ac-methanol). Method performance was demonstrated in real samples showing good linearity (R≥0.9928) and intra- and inter-day precision (%RSD≤15%). Method LODs were ≤0.952μgg-1 and ≤0.476μgg-1 for confectionery and cosmetic samples, respectively. Recoveries of compounds from nine different matrices were quantitative. The validated method was successfully applied to 24 commercial samples (14 cosmetics and 10 foods) in which 9 of the selected dyes were found at concentrations up to 989μgg-1, exceeding in some cases the regulated maximum permitted limits. A non-permitted dye, Acid Orange 7, was found in one candy.

In the absence of added electrolyte, at ionic strengths below 0.5 mM, maximum extents on adsorption of 100 μM ligand onto 1.06 g L−1 FeOOH(goethite) increased in the order (2-phenylglycine) }{\text{SOH}} + {\text{L}}^{-} = {>}{\text{S}}\left( {\text{OH}} \right){\text{L}}^{ - }\) provided a better fit to experimental data for most ligands than the conventional stoichiometry \({>}{\text{SOH}} + {\text{H}}^{ + } + {\text{L}}^{ - } = {>}{\text{SL}}^{0} + {\text{H}}_{2} {\text{O}}\). Partial loss of waters of adsorption accompanying adsorption impedes the adsorption of strongly hydrated anions over less strongly hydrated ones.

Adsorption of sodium dodecyl sulfate (SDS) onto large α-alumina beads was systematically analyzed as functions of pH and NaCl concentration. The maximum adsorption density of SDS onto α-Al2O3 increases with decreasing pH due to the increase in equilibrium surface charge. Adsorption isotherms at different salt concentrations demonstrated a common intersection point (CIP) corresponding to charge neutralization. The obtained comprehensive data clarified the applicability of two-step adsorption and four-region models to describe the adsorption isotherms of SDS onto α-Al2O3 beads. Also, proton adsorption isotherms upon SDS uptake onto α-Al2O3 can be fitted by two-step adsorption model with almost the same parameters of surfactant adsorption for 0.001 and 0.01 M NaCl. Our finding indicates that proton adsorption takes place onto the adsorbed SDS. After passing through CIP, proton adsorption onto α-Al2O3 increases at low ionic strength while the amount of proton adsorption does not change for 0.1 M NaCl. Adsorption amount of proton as a function of SDS adsorption shows that only hemimicelles are plausible for case of low ionic strength. The increase in the proton adsorption is not significant at high ionic strength, suggesting the presence of admicelles on the surface of α-Al2O3 beads.

We present nanoslit confined DNA conformations at very low ionic strengths and a theory to explain most measurements for single DNA molecule size under strong nanoslit confinement. Very low ionic strength conditions not only increase the DNA persistence length dramatically, but also cause DNA molecules to swell to the extent that the effective diameter of DNA becomes larger than the nanoslit height. By accounting for these effects, our results and theory provide a reasonable clue for a current controversy regarding the dependence of the DNA conformation on slit height (h), persistence length (p), and effective diameter (w).

In this study, orange peel was utilized as low-cost adsorbent to remove furadan from aqueous solution by adsorption. All the experiments were conducted at 30 °C to investigate the effects adsorbent dose, pH value and ionic strength on furadan adsorption and the optimal experimental conditions were ascertained. The percentage removal (%) increased with an increase in the initial adsorbent dose, whereas the value of qe (mg.g-1) decreased with an increase in the initial adsorbent dose .The curve of qe and removal percentage can be divided into two stages (first stage: adsorbent dose between 0.05 and 0.20 g; second stage: adsorbent dose between 0.25 and 0.35 g). The value of qe (mg.g-1) for OP increased as the pH increase, and reached the maximum at pH 7.81, then decreased as the pH continue increasing. The initial pH value of furadan solution should be controlled between 7.50 and 8.00. In addition, the value of qe decreased sharp as the initial Na+ concentration was increased from 0 to 2.5 ×10-3 mol.L-1, then, the value of qe was not significantly altered beyond the initial Na+ concentration 2.5×10-3 mol.L-1. Therefore in order to enhance adsorption efficiency of furadan by OP, the subsequent experiments were carried out in the low ionic strength of furadan solution.

In this thesis the chromatography on DEAE-Cellulose 52 was used to isolate the crude polysaccharide from purple sweet potato (PPSP) . To get the purest polysaccharide from the purple sweet potato for the purpose, the influence of different pH environments and whether the fractions eluted with the high and low ionic strength eluents in corresponding pH environment during the elution process had the hybrid phenomenon were studied. Finally, results suggested that the purest polysaccharide of purple sweet potato would be got in the neutral and low ionic strength solution of NaCl when the crude polysaccharide was isolated by the chromatography column on DEAE-Cellulose 52 according to this study, and in this thesis the low ionic strength solution of NaCl was 11.7g.L-1, the elution rate of polysaccharide eluted with it was about 3% and the purity was about 94%.

Soil dissolved phosphorus (P) and colloidal P mobilization could be closely related to the degree of phosphorus saturation (DPS). Effects of a wide range of DPS on the distributions of dissolved P and colloidal P in a paddy soil profile were investigated in this study. Dissolved P and colloidal P in water-dispersible soil colloid suspension increased obviously with increasing DPS. The change point of DPS was at 0.12 by using a split-line model. Above the value, dissolved P (3.1 mg P kg −1 ) in soil profile would increase sharply and then transfer downward. Compared with dissolved P, colloidal P was the dominant fraction (78%–91%) of P in soil colloid suspension, and positively related to DPS without a significant change point. The high release of colloids in subsoils with low DPS was attributed to the low ionic strength and high pH value in subsoils. The DPS also had a significant and positive correlation with electrical conductivity (EC), but it showed a negative correlation with pH value. However, the concentration of colloidal P was not greatly correlated to the pH value, EC and optical density of the soil colloid suspension. The results indicated that DPS was an important factor that may affect the accumulation and mobilization of water-extractable colloidal P and dissolved P.

The effect of low ionic strength leading to reduced polyelectrolyte–protein interactions has been shown by in silico and in vitro experiments, suggesting polyelectrolyte rigidity increasing at low ionic strength, thus leading to reduced interactions with proteins. This contribution elucidates polyelectrolyte–protein precipitation in the 0–2.6-mS cm−1 ionic strength regime with polyelectrolyte rigidity determinations, using viscosimetry at these conditions, also considering protein charge distributions, using different proteins. Precipitation yields increased from 5 to 40 % at low ionic strength to up to 90 % at intermediate ionic strength, depending on protein and polyelectrolyte type, using lysozyme and three different monoclonal antibodies. Comparing precipitation behavior of the monoclonal antibodies, a qualitative correlation between required polyelectrolyte flexibility to enhance protein precipitation and protein average charge as well as hydrophobicity of the antibodies was discovered. Antibodies with lower average charge and less hydrophobicity required more flexible polyelectrolytes to enhance precipitation behavior by allowing interaction of the polyelectrolytes with proteins, attaching to positively charged protein patches while “circumnavigating” negatively charged protein areas. In contrast, antibodies with higher protein average charge showed increasing precipitation yields up to 90 % already at lower ionic strength, associated with then more rigid polyelectrolyte structures. Therefore, designing polyelectrolytes with specific chain flexibility could help to improve precipitation behavior toward specific target proteins in polyelectrolyte-driven purification techniques.

Glaciers and ice sheets are recognised as important components of global biogeochemical cycles. Chemical sensors have great potential for in situ monitoring in the cryosphere and are available for many analytes of interest, but they are frequently unsuitable for deployment since meltwaters are cold, turbid, experience freeze-thaw cycles and display low ionic strength and concentrations of target analytes. Here, we review in situ chemical sensors currently available for measurement of biogeochemically important analytes and assess their suitability for deployment. These include standard parameters such as dissolved oxygen and pH, along with macronutrients (nitrate/nitrite and phosphate), micronutrients (iron and manganese) and biogenic gases (methane). Where no commercial alternatives are available, we discuss sensors currently in development, and their applicability to these extreme environments. The information presented has great relevance for future science in polar environments, and for the ultimate goal of obtaining in situ data from extreme, inaccessible subglacial environments.

We review the interaction of charged polymeric systems with proteins. In solutions of low ionic strength there are many examples of proteins attracted to polyelectrolytes even if both systems carry the same overall charge. This attractive interaction is widespread, having been observed for single polyelectrolyte chains as well as for polyelectrolytes grafted to surfaces (polyelectrolyte brushes) and charged polymeric networks. In all cases, adding salt weakens the interaction considerably. We discuss the suggestion that the attractive force at low salinity originates from the asymmetry of interaction between charged polymer segments and charged patches on the surface of the protein globule. This can be explained if the attractive force is mainly due to a counterion release force, i.e., the polyelectrolyte chains become the multivalent counterions for the patches of opposite charge localized on the surface of the proteins. We review a selection of simple models that lead to semi-quantitative estimates of this force as the function of salt concentration.

Surface-tethered biomolecules play key roles in many biological processes and biotechnologies. However, while the physical consequences of such surface attachment have seen significant theoretical study, to date this issue has seen relatively little experimental investigation. In response we present here a quantitative experimental and theoretical study of the extent to which attachment to a charged –but otherwise apparently inert– surface alters the folding free energy of a simple biomolecule. Specifically, we have measured the folding free energy of a DNA stem loop both in solution and when site-specifically attached to a negatively charged, hydroxyl-alkane-coated gold surface. We find that, whereas surface attachment is destabilizing at low ionic strength it becomes stabilizing at ionic strengths above ~130 mM. This behavior presumably reflects two competing mechanisms: excluded volume effects, which stabilize the folded conformation by reducing the entropy of the unfolded state, and electrostatics, which, at lower ionic strengths, destabilizes the more compact folded state via repulsion from the negatively charged surface. To test this hypothesis we have employed existing theories of the electrostatics of surface-bound polyelectrolytes and the entropy of surface-bound polymers to model both effects. Despite lacking any fitted parameters, these theoretical models quantitatively fit our experimental results, suggesting that, for this system, current knowledge of both surface electrostatics and excluded volume effects is reasonably complete and accurate.

Binding properties are important for meat products and are substantially derived from the heat-induced gelation of myosin. We have shown that myosin is solubilized in a low ionic strength solution containing L-histidine. To clarify its processing characteristics, we investigated properties and structures of heat-induced gels of myosin solubilized in a low ionic strength solution containing L-histidine. Myosin in a low ionic strength solution formed transparent gels at 40-50°C, while myosin in a high ionic strength solution formed opaque gels at 60-70°C. The gel of myosin in a low ionic strength solution with L-histidine showed a fine network consisting of thin strands and its viscosity was lower than that of myosin in a high ionic strength solution at 40-50°C. The rheological properties of heat-induced gels of myosin at low ionic strength are different from those at high ionic strength. This difference might be caused by structural changes in the rod region of myosin in a low ionic strength solution containing L-histidine.

International audience; The aim of the study was to delineate and compare the proteomic maps of two muscles of dry-cured ham: the biceps femoris and the semimembranosus. For this purpose, we used two-dimensional electrophoresis on a subcellular muscle fraction: insoluble protein in low ionic strength buffer. After protein identification by MALDI–TOF mass spectrometry and bioinformatic analyses, we found differences in expression levels in the two muscles. Seventy-three proteins or fragments were differentially expressed: 43 were over-represented in semimembranosus and 30 in biceps femoris. Although the study was performed on the insoluble protein fraction in low strength ionic buffer, protein and fragment identifications by mass spectrometry showed that most of the proteins were involved in energy metabolism. The differences observed between the two muscles can be explained by the differences in salt and moisture content in the course of dry-cured ham processing.