Search

The optimal conditions for the preparation of maltotriose-conjugated chicken myofibrillar proteins (Mfs), exhibiting high solubility in low ionic strength medium, through the Maillard reaction were investigated using random-centroid optimization. Parameters of temperature, relative humidity (RH), reaction time, and maltotriose to chicken Mfs mixing ratio were examined, resulting in 13 vertices. Evaluations were carried out related to each individual vertex, and the optimal preparatory conditions resulting in the highest solubility were determined as follows: temperature of 53 degrees C, RH of 45 %, reaction time of 38.5 h, and maltotriose to chicken Mfs mixing ratio of 4.24 (w/w), presenting 54.9 +/- 1.9 % solubility in low ionic strength medium. Its hydroxyl radical averting capacity showed 8.1 +/- 0.4 mu mol of gallic acid equivalent per gram of protein. The thermal gel-forming ability of chicken Mfs was retained by the maltotriose-conjugation.

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.

Liquid–liquid phase separation underlies the membrane-less compartmentalization of cells. Intrinsically disordered low-complexity domains (LCDs) often mediate phase separation, but how their phase behavior is modulated by folded domains is incompletely understood. Here, we interrogate the interplay between folded and disordered domains of the RNA-binding protein hnRNPA1. The LCD of hnRNPA1 is sufficient for mediating phase separation in vitro. However, we show that the folded RRM domains and a folded solubility-tag modify the phase behavior, even in the absence of RNA. Notably, the presence of the folded domains reverses the salt dependence of the driving force for phase separation relative to the LCD alone. Small-angle X-ray scattering experiments and coarse-grained MD simulations show that the LCD interacts transiently with the RRMs and/or the solubility-tag in a salt-sensitive manner, providing a mechanistic explanation for the observed salt-dependent phase separation. These data point to two effects from the folded domains: (i) electrostatically-mediated interactions that compact hnRNPA1 and contribute to phase separation and (ii) increased solubility at higher ionic strengths mediated by the folded domains. The interplay between disordered and folded domains can modify the dependence of phase behavior on solution conditions and can obscure signatures of physicochemical interactions underlying phase separation., Graphical Abstract Graphical AbstracthnRNPA1 phase separation is highly salt sensitive. Phase separation of the low-complexity domain (LCD) of hnRNPA1 increases with NaCl. In contrast, phase separation of full-length hnRNPA1 is salt-sensitive. At low NaCl concentrations, electrostatic RRM–LCD interactions occur and can contribute positively to phase separation, but they are screened at high NaCl concentrations. The folded domains solubilize hnRNPA1 under these conditions and prevent phase separation.

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.

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

Graphical abstract, Highlights • The assembly behavior of myosin molecules limits the development of interfacial proteins. • High-intensity ultrasound (HIU) disrupted the filamentous myosin structure. • HIU improved the physical stability of myofibrillar protein (MPs) emulsion. • HIU pretreatment promoted the adsorption and rearrangement of MPs at the O/W interface. • HIU pretreatment enhanced the inter-droplet interactions., The specific molecular behavior of myofibrillar proteins (MPs) in low-salt media limits the development of muscle protein-based emulsions. This study aimed to evaluate the potential of high-intensity ultrasound (HIU; 150, 300, 450, and 600 W) to improve the physical stability of MP emulsion at low ionic strength and decipher the underlying mechanism. According to the physical stability analysis, HIU pretreatment, especially at 450 W power, significantly improved the physical stability of MP emulsions, as evidenced by the reduced particle size, enhanced inter-droplet interactions, and increased uniformity of the droplet size distribution (p

Measuring pH in glacial meltwaters is challenging, because they are cold, remote, subject to freeze‐thaw cycles and have low ionic strength. Traditional methods often perform poorly there; glass electrodes have high drift and long response times, and spectrophotometric techniques are unpractical in cold, remote environments. Ion selective field effect transistor (ISFET) sensors are a promising alternative, proven in marine and industrial applications. We assess the suitability of two models of ISFET, the Honeywell Durafet and Campbell Scientific Sentron, for use in glacial melt through a series of lab and field experiments. The sensors have excellent tolerance of freeze‐thaw and minimal long‐term drift, with the Durafet experiencing less drift than the Sentron model. They have predictable response to temperature, although the Durafet housing causes some lag during rapid cycling, and the impact of stirring is an order of magnitude less than that of glass electrodes. At low ionic strength ( 7 with consistent diurnal cycles from the very first meltwater flows. We recommend that ISFET sensors are used to assess the pH of glacial meltwater, since their tolerance is significantly better than alternative methods: the Durafet is accurate to ± 0.2 pH when waters are > 1 mmol L−1 ionic strength, and ± 0.3 pH at

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.

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.

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.

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.

Charged food hydrocolloids provide structure and texture in manufactured foods by their organization and electrostatic interactions with other species and small ions. These electrostatic interactions depend on their actual charge density which cannot be predicted from pKa values of weakly charged monomers. In practice, this is circumvented by the use of an ‘apparent pKa’ (pKa (app)) which depends on solution ionic strength and type of counter-ions. pKa (app) values for food hydrocolloids are poorly documented, especially in low ionic strength solvents. Titration of a metachromatic alginate-ortho-toluidine blue complex revealed a sigmoidal, pH-dependent, dye metachromasy response with its centre located at pH = pKa (app). To test the suitability of this approach for the determination of pKa (app), five food hydrocolloids and a synthetic polyanion are analysed and the results are compared to classical methods such as potentiometric titration. Metachromasy is shown to occur when the polymer inter-charge distance is 4.5 Å; the complex stoichiometry depending on inter-charge distance. pKa (app) of stoichiometric complexes at low ionic strength (1 mM phosphate buffer) were successfully determined (alginate 4.5, sodium carboxymethylcellulose 4.6, κ-carrageenan 1.2, polyphosphate 2.1 and polyacrylic acid 5.8) and are comparable to values obtained by potentiometric titration. Further, it is shown that pKa (app) determination by metachromatic dye titration is feasible for stoichiometric polymer-dye complexes at low concentrations (20–200 μM) in low ionic strength (

We report a high-speed lateral flow strategy for a fast biosensing with an improved selectivity and binding affinity even under harsh conditions. In this strategy, biosensors were fixed at a location away from the center of a round shape disk, and the disk was rotated to create the lateral flow of a target solution on the biosensors during the sensing measurements. Experimental results using the strategy showed high reaction speeds, high binding affinity, and low nonspecific adsorptions of target molecules to biosensors. Furthermore, binding affinity between target molecules and sensing molecules was enhanced even in harsh conditions such as low pH and low ionic strength conditions. These results show that the strategy can improve the performance of conventional biosensors by generating high-speed lateral flows on a biosensor surface. Therefore, our strategy can be utilized as a simple but powerful tool for versatile bio and medical applications.

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.

Polymersomes and complex coacervates have been the subject of considerable interest due to their wide application as compartments for the encapsulation of various actives. In this paper, we present for the first time that the transformation of small unilamellar vesicles (polymersomes) to coacervate microdroplets is possible by a simple adjustment of the ionic strength. We demonstrated that a pair of zwitterionic-ionic copolymers self-assembles in an aqueous medium forming small unilamellar polymersomes. Cryo-transmission electron microscopy showed that the polymersomes had a diameter of 120 ± 49 nm and a membrane thickness of 25–30 nm. The polymersomes are stable at low ionic strength including physiological conditions, but they can be transformed into the coacervate microdroplets of several µm in diameter by increasing the salt concentration. The process can be reversed by reducing the salt concentration, what leads to the spontaneous formation of giant or small polymersomes. These studies contribute to the development of polymeric materials that can self-organize into ionic strength- responsive vesicular and solid structures (without the use of organic solvents) potentially useful for compartmentalization.

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.

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.

Morphological response (MR) of red blood cells represents a triphasic sequence of spontaneously occurring shape transformation between different shape states upon transfer the cells into isotonic sucrose solution in the order: S(0) (initial discoid shape in physiological saline)--S(1) (echinocytic shape at the beginning of MR, phase 1)--S(2) (intermediate discoid shape, phase 2)--S(3) (final stomatocytic shape, phase 3). In this paper, the dynamics of cell shape changes was investigated by non-invasive light fluctuation method and optical microscopy. Among 12 possible transitions between four main shape states, we experimentally demonstrate here an existence of nine transitions between neighbour or remote states in this sequence. Based on these findings and data from the literature, we may conclude that red blood cells are able to change their shape through direct transitions between four main states except transition S(1)--S(0), which has not been identified yet. Some shape transitions and their temporal sequence are in accord with predictions of bilayer couple concept, whereas others for example transitions between remote states S(3)--S(1), S(1)--S(3) and S(3)--S(0) are difficult to explain based solely on the difference in relative surface areas of both leaflets of membrane suggesting more complex mechanisms involved. Our data show that MR could represents a phenomenon in which the major role can play pH and chloride-sensitive sensor and switching mechanisms coupled with transmembrane signaling thus involving both cytoskeleton and membrane in coordinated shape response on changes in cell ionic environment.

Fast DNA detection remains of great interest in human genetics, medicine, and drug discovery. The detection of DNA hybridisation makes the screening of point mutations in potential cancer genes or DNA fingerprinting for phylogenesis purposes possible (S.W. Yeung, T.M.H. Lee, H. Cai, and I.M. Hsing, A DNA biochip for on-the-spot multiplexed pathogen identification, Nucleic Acids Research 34 (2006), p. e118; P. Liepold, H. Wieder, H. Hillebrandt, A. Friebel, G. Hartwich, DNA-arrays with electrical detection: a label-free low cost technology for routine use in life sciences and diagnostics, Bioelectrochemistry, 67 (2005), pp. 143–150). The speed, cost and reliability of the hybridisation detection is of high importance. Electronic detection of hybridisation events using standard CMOS-fabricated devices such as Field Effect Transistors (FETs) promises fast, label-free and multiplexed read-out systems. Moreover, they hold the advantage of high-throughput and minimalisation, which makes them ideal for implement...

Environmental context Knowledge of the speciation of metals, especially of the free metal ion concentration, is essential to understand the fate of these elements in rivers and their effects on living organisms. On-site analyses are preferred for these measurements as they allow problems associated with sample transportation and preservation to be avoided. In this context, an on-site methodology based on an electrochemical method and screen-printed sensors has been developed in the laboratory and validated on site. Abstract An on-site methodology has been developed for the direct determination of free Zn2+ with AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) in freshwaters. This implementation includes: (i) the use of screen-printed electrodes, which provide good limits of detection and easy transportation and deployment; (ii) no need for sample purging; (iii) a calibration in a synthetic river solution that reproduces the speciation changes of the natural samples well and allows oxygen interference to be minimised; (iv) the addition of a background electrolyte up to 0.01molL–1 in both the calibration and freshwater samples; (v) chemical stripping chronopotentiometry as the quantification stage of AGNES. This procedure minimises the effects of working at low ionic strength and in the presence of dissolved oxygen. In the laboratory, the methodology was checked with different natural samples taken from rivers Garonne, Gave de Cauterets and Gave de Pau in the Pyrenees. Results appeared in good agreement with theoretical estimations computed from Visual Minteq. On-site measurements were performed for the first time with AGNES in the Gave de Cauterets in Soulom (France) and the results were corroborated with purged measurements performed in the laboratory.

Within the UK blood transfusion services, there is currently no recommendation for the use of either clotted or anticoagulated samples for antibody identification testing. This report describes three cases in which the detection of IgM antibodies was impeded by the use of anticoagulated samples. Two patient samples, referred for compatibility testing, were both identified as having IgM complement-activating anti-S and the remaining case involved an antenatal patient with IgM complement-activating anti-Vel. In all three cases, the coincidental referral and investigation of both clotted and anticoagulated samples led to the discrepancy in serum and plasma test results becoming apparent. Potential errors in selection of suitable blood for transfusion and appropriate antenatal management were avoided by correct identification of the antibodies present using the clotted samples. Immunohematology 2006;22:72–77.

A flow‐through, low ionic strength nutrient solution system was used in four experiments to establish elongation rates, time to maximum length of individual root hairs, and temporal changes in length in small populations of root hairs in a genotype from a population of cv ‘Tamar’ white clover (Trifolium repens L.) previously selected for long root hairs. Young root hairs showed pronounced pulsatile growth, with relative extension rates increasing four‐fold over the basal rate. In older hairs the amplitude and frequency of the pulsatile growth declined as hairs approached their full length. At the average root hair elongation rate over all hairs and experiments (3.3 mm h‐1) it would take 4.5 days for the longest root hair observed (363 μm) to reach its final length, and 2.4 days to reach the population mean root hair length of 190 μm. Re‐analysis of the data using a Bayesian technique gave an estimate of 2.0 days for root hairs to reach the population mean length. The results suggest that root tip...

Sorption of nonylphenol on Na-montmorillonite was studied by batch experiment and compared with that on α-SiO2, α-Al2O3 and gibbsite. It was found that sorption of nonylphenol on Na-montmorillonite reached the equilibrium state within 24 h, and that the interlayer width of Na-montmorillonite did not change before and after the sorption. These suggest that nonylphenol was sorbed on the outer surface of Na-montmorillonite. Sorption isotherms of nonylphenol on Na-montmorillonite, α-SiO2, α-Al2O3 and gibbsite were studied. Sorption amount of nonylphenol on the surface of octahedral sheets of Na-montmorillonite was found to be identical to that of gibbsite. On the other hand, sorption amount on α-Al2O3 was smaller, and that on α-SiO2 was fairly few. Dependence of sorption onto Na-montmorillonite on pH and ionic strength was also examined. Sorption amount was found to increase monotonously with pH. Sorption amount decreased with ionic strength in the low ionic strength region, reached to a minimum and then increased with ionic strength. These results might suggest that nonylphenol was sorbed on the broken-edges of octahedral alumina sheets of Na-montmorillonite.

The molecular chaperone DnaK prevents intracellular protein misfolding and aggregation by transiently binding with newly synthesized polypeptides and protein-folding intermediates. DnaK preferentially binds to peptides with basic residues (Arg/Lys) present on the outside of a hydrophobic core. The electrostatic contribution toward DnaK/peptide binding was determined by measuring the dissociation constant of DnaK complexes with two fluorescein-labeled peptides (f-NRLLLTG and f-NALLLTG) using fluorescence anisotropy. The measured dissociation constants, Kd, differ significantly at low ionic strength: at 20 mM phosphate buffer; Kd for DnaK and f-NRLLLTG is 0.2 μM while that for DnaK and f-NALLLTG is 1 μM. This difference, attributed to stronger Coulombic binding in the case of f-NRLLLTG, vanishes at high ionic strength due to electrostatic screening. For f-NRAAATG, no interaction with DnaK was apparent, showing that hydrophobic interactions are essential in chaperone/peptide binding. The ionic strength depe...

Dilute electrostatically stabilized aqueous solutions of hexa-acylated (C14) lipid A diphosphate from Escherichia coli form stable and regularly shaped colloidal crystals in a size range of approximately 50-1000 nm in width and 50-100 nm in thickness. The formation of these nanocrystals occurs over a range of volume fractions between 3.5 × 10-3 and 1.2 × 10-2 and at a low ionic strength, ~10-5. The shape of these crystals appears to be cubic or rhombohedral, and when exposed to the electron beam, these fragile nanocrystals are easily damaged. Electron diffraction patterns obtained from single particles reveal that they are orientated (001) crystals that conform to a trigonal or hexagonal unit cell (a = 3.65 ± 0.07 nm and c = 1.97 ± 0.04 nm), revealing crystal-like pore walls that exhibit structural periodicity with a spacing of 0.65 nm and are at least four times the size of the unit cell adopted by lipid A diphosphate.

Denaturing polyacrylamide gel electrophoresis (SDS-PAGE) was used to separate and identify the proteins soluble in low ionic strength buffer that were extracted from Semimembranosus and Biceps femoris muscles from raw hams and after curing for 11 months. The samples analysed were taken from three white pig crosses produced by three different selective breeding enterprises: cross A (75% Duroc-25% Landrace), cross B (50% Duroc-25% Landrace-25% Large White) and cross C (75% Duroc-25% Landrace). The electrophoretic profiles for the two muscles from the raw hams were qualitatively similar, but the profiles for the muscles from the cured hams revealed changes in the electrophoretic bands in the range of 66–149 kDa. The relative concentrations of certain proteins differed in both the raw and cured hams from the three crosses. Curing resulted in the loss of electrophoretic bands, chiefly for the higher molecular weights; the appearance of new protein fragments, primarily in the range of 9–22 kDa, and quantitative variations in certain polypeptides.

A sequential NMR based approach is proposed for measurements of high log K values at low ionic strength. [31P] NMR technique is used to determine the protonation constants of 1,2-diaminoethane-N,N,N′,N′-tetra(methylenephosphonic acid) (EDTPH, H8L) at 25°C in 0.1 mol-dm−3 KNO3 and at 37°C in 0.15 mol-dm−3 NaCl at pH 11–14. For equilibrium L + H ⇔ HL log K are found to be 13.3 (0.1) and 12.9 (0.1), respectively.

The heteroaggregation of engineered nanoparticles (ENPs) with natural colloids (NCs), which are ubiquitous in natural surface waters, is a crucial process affecting the environmental transport and fate of ENPs. Attachment efficiencies for heteroaggregation, αhetero, are required as input parameters in environmental fate models to predict ENP concentrations and contribute to ENP risk assessment. Here, we present a novel method for determining αhetero values by using a combination of laser diffraction measurements and aggregation modeling based on the Smoluchowski equation. Titanium dioxide nanoparticles (TiO2 NPs, 15 nm) were used to demonstrate this new approach together with larger silicon dioxide particles (SiO2, 0.5 μm) representing NCs. Heteroaggregation experiments were performed at different environmentally relevant solution conditions. At pH 5 the TiO2 NPs and the SiO2 particles are of opposite charge, resulting in αhetero values close to 1. At pH 8, where all particles are negatively charged, αhetero was strongly affected by the solution conditions, with αhetero ranging from 2 concentrations. The presence of humic acid stabilized the system against heteroaggregation.

We present a method of calculating the electric charge density of glass and silica surfaces in contact with aqueous electrolytes for two cases of practical relevance that are not amenable to standard techniques: surfaces of low specific area at low ionic strength and surfaces interacting strongly with a second anionic surface., 7 pages, including 3 figures