•High repeatability and intra- and inter-capillary precision were achieved.•Cross-contamination between polyelectrolyte vials lowers repeatability and efficiency.•PDADMAC/PSS coatings are durable ...over 100 runs and can be regenerated.•Average retention factors of 4×10−2 quantify low residual adsorption.•Proteins must be stored separately in water to avoid degradation.
Since the introduction of polyelectrolyte multilayers to protein separation in capillary electrophoresis (CE), some progress has been made to improve separation efficiency by varying different parameters, such as buffer ionic strength and pH, polyelectrolyte nature and number of deposited layers. However, CE is often overlooked as it lacks robustness compared to other separation techniques. In this work, critical parameters for the construction of efficient and reproducible Successive multiple ionic-polymer layers (SMIL) coatings were investigated, focusing on experimental conditions, such as vial preparation and sample conservation which were shown to have a significant impact on separation performances. In addition to repeatability, intra- and inter-capillary precision were assessed, demonstrating the improved capability of poly(diallyldimethylammonium chloride) / poly(sodium styrene sulfonate) (PDADMAC / PSS) coated capillaries to separate model proteins in a 2 M acetic acid background electrolyte when all the correct precautions are put in place (with run to run%RSD(tm) < 1.8%, day to day%RSD(tm) < 3.2% and cap to cap%RSD(tm) < 4.6%). The approach recently introduced to calculate retention factors was used to quantify residual protein adsorption onto the capillary wall and to assess capillary coating performances. 5-layer PDADAMAC / PSS coatings led to average retention factors for the five model proteins of ∼4×10−2. These values suggest a relatively low residual protein adsorption leading to reasonably flat plate height vs linear velocity curves, obtained by performing electrophoretic separations at different electrical voltages (-10 to -25 kV).
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Taylor dispersion analysis is an increasingly popular characterization method that measures the diffusion coefficient, and hence the hydrodynamic radius, of (bio)polymers, nanoparticles, or even ...small molecules. In this work, we describe an extension to current data analysis schemes that allows size polydispersity to be quantified for an arbitrary sample, thereby significantly enhancing the potentiality of Taylor dispersion analysis. The method is based on a cumulant development similar to that used for the analysis of dynamic light scattering data. Specific challenges posed by the cumulant analysis of Taylor dispersion data are discussed, and practical ways to address them are proposed. We successfully test this new method by analyzing both simulated and experimental data for solutions of moderately polydisperse polymers and polymer mixtures.
Understanding how orogenic topography controls the spatial distribution and isotopic composition of precipitation is critical for paleoaltitudinal reconstructions. Here, we determine the isotopic ...composition (δ18O and δD) of 82 small rivers and springs from small catchments in the Pyrenees. Calculation of the deuterium excess (d-excess) parameter allows the distinction of four distinct isotopic provinces with d-excess values of between 15 and 22‰ in the northwest, between 7 and 14‰ in the central northern Pyrenees and between 3 and 11‰ in the northeast. The southern Pyrenees have a homogenous d-excess signature ranging from 7 to 14‰. Our results show significant local moisture recycling and/or rain amount effect in the northwestern Pyrenees, and control by evaporation processes during rainfall events in the southern Pyrenees and for low elevated samples of the northeast of the range. Based on the distribution of d-excess values, we estimate contrasting isotope lapse rates of −2.9/−21.4‰/km (δ18O/δD) in the northwest, −2.7/−21.4‰/km (δ18O/δD) in the north central and −3.7/−31.7‰/km (δ18O/δD) in the northeastern Pyrenees. The southern Pyrenees show distinctly higher lapse rates of −9.5/−77.5‰/km (δ18O/δD), indicating that in this area the altitudinal effect in not the only parameter driving isotopic composition of rivers. Despite their relatively low topographic gradient, the Pyrenees exert a direct control on the isotopic composition of river waters, especially on their northern side. The variations in isotopic composition–elevation relationships documented along the strike of the range are interpreted to reflect an increasing continentality effect driven by wind trajectories parallel to the range, and mixing with Mediterranean air masses. Despite these effects, the measurable orographic effect on precipitation in the Pyrenees proves that the isotopic composition approach for reconstructing past topography is applicable to low-elevation orogens.
•We analyze the δ18O and δD composition of river water of the Pyrenees.•We distinguish four isotopic provinces around the Pyrenees.•Isotope composition of rivers are controlled by elevation in the northern Pyrenees.•Evaporation processes control the isotopic record of rivers in the southern Pyrenees.•Paleoelevation reconstructions are possible in the northern Pyrenees.
Core Ideas
An experimental setup was designed to observe and accurately locate hydraulic lift.
Water stable isotope enrichment was observed in topsoil layers.
The results could be successfully ...reproduced using a 3D soil–root model.
This study tested a method to quantify and locate hydraulic lift (HL, defined as the passive upward water flow from wetter to dryer soil zones through the plant root system) by combining an experiment using the stable water isotope 1H218O as a tracer with a soil–plant water flow model. Our methodology consisted in (i) establishing the initial conditions for HL in a large rhizobox planted with Italian ryegrass (Lolium multiflorum Lam.), (ii) labeling water in the deepest soil layer with an 18O‐enriched solution, (iii) monitoring the water O isotopic composition in soil layers to find out changes in the upper layers that would reflect redistribution of 18O‐enriched water from the bottom layers by the roots, and (iv) comparing the observed soil water O isotopic composition to simulation results of a three‐dimensional model of water flow and isotope transport in the soil–root system. Our main findings were that (i) the depth and strength of the observed changes in soil water O isotopic composition could be well reproduced with a modeling approach (RMSE = 0.2‰, i.e., equivalent to the precision of the isotopic measurements), (ii) the corresponding water volume involved in HL was estimated to account for 19% of the plant transpiration of the following day, i.e., 0.45 mm of water, and was in agreement with the observed soil water content changes, and (iii) the magnitude of the simulated HL was sensitive to both plant and soil hydraulic properties.
•TDA is suitable for sizing various vaccine antigens.•Polydispersity indexes of vaccine antigens can be obtained by TDA.•LOD varies as 1/t0, t0 being the average elution time.•The lower the pressure, ...the more sensitive the TDA method.•LOD varies as 1/Ld, Ld being the detection capillary length.
The development of a new vaccine requires the precise characterization of all the physicochemical parameters of the vaccine antigens, which are the molecules that induce the immune response. Taylor dispersion analysis (TDA) is a promising alternative technique for the determination of diffusion coefficients and hydrodynamic radii of proteins, macromolecules and nanoparticles. In this work, TDA was used to determine the hydrodynamic radius distribution and its average value of four antigens: diphtheria toxoid (DT), tetanus toxoid (TT), hepatitis B surface antigen (HBsAg) and polyribosyl-ribitol phosphate conjugated to tetanus toxoid (PRP-T). The robustness of the results obtained was investigated on bare fused silica capillary and hydroxypropylcellulose coated capillary. The impact of operational parameters on the limit of detection (LOD) and limit of quantification (LOQ) were studied from both theoretical and experimental points of view. The influence of the diameter and the length of the capillary on the LOD and LOQ were studied as well as the impact of the mobilization pressure. General guidelines for the choice of the initial operating conditions are given for the development of future TDA methods.
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► Controlled conditions experiments and deterministic models are complementary. ► We perform a multi-objective calibration of the SiSPAT-Isotope SVAT model. ► Model parameters distributions are ...inferred from the calibration. ► We simulate the evolutions of soil isotopic compositions and root water uptake. ► We provide guidelines for partitioning evapotranspiration in the field.
Stable isotopes of water (18O and 2H) are tracers of ecosystem processes and in particular of water vapour sources. They have been substantially used for evapotranspiration (ET) studies. Data gathered during a series of soil monoliths experiments under fully controlled conditions allowed the partitioning of ET fluxes into soil evaporation (Ev) and plant transpiration (Tr) from isotopic measurements along growth of a tall fescue cover. These data were used to calibrate SiSPAT-Isotope, a 1D Soil–Vegetation–Atmosphere Transfer (SVAT) model coupled with a module for isotopic transport in the soil and the atmosphere. For this, the soil isotopic module was extended to take into account plant water uptake by roots and the model was modified so that it could be constrained with collected input data (e.g. ET flux). The multi-objective calibration method allowed determining narrowed probability distributions for soil, plant and isotopic parameters of which some are currently debated and/or typically not measured in the field (e.g. kinetic fractionation factor during soil evaporation). Comparisons between simulation results corresponding to the “best compromise” parameter set with data (i.e. soil water pressure and contents, soil temperatures and heat fluxes, soil isotopic compositions, and root extraction depths) were provided to show the consistency of the calibration method. Guidelines were provided for the determination of the isotopic composition of evaporation in the field: we could emphasize the importance of values used for the kinetic fractionation factor and the impact of the heights at which atmospheric variables (air relative humidity and temperature, isotopic composition of atmospheric water vapour) are measured in the field.
Taylor dispersion analysis is an absolute and straightforward characterization method that allows determining the diffusion coefficient, or equivalently the hydrodynamic radius, from angstroms to ...submicron size range. In this work, we investigated the use of the Constrained Regularized Linear Inversion approach as a new data processing method to extract the probability density functions of the diffusion coefficient (or hydrodynamic radius) from experimental taylorgrams. This new approach can be applied to arbitrary polydisperse samples and gives access to the whole diffusion coefficient distributions, thereby significantly enhancing the potentiality of Taylor dispersion analysis. The method was successfully applied to both simulated and real experimental data for solutions of moderately polydisperse polymers and their binary and ternary mixtures. Distributions of diffusion coefficients obtained by this method were favorably compared with those derived from size exclusion chromatography. The influence of the noise of the simulated taylorgrams on the data processing is discussed. Finally, we discuss the ability of the method to correctly resolve bimodal distributions as a function of the relative separation between the two constituent species.
In the beginning: Mixed carboxylic phosphoric anhydrides 3, formed from 3′‐nucleotides 1 and amino acid N‐carboxyanhydrides 2, undergo competing rearrangement to 2′‐aminoacyl esters 4 and cyclization ...to 2′,3′‐cyclic phosphates 5. The intramolecular aminoacyl transfer is faster than the cyclization despite the ease with which 2′,3′‐cyclic phosphates are formed through any other form of phosphate activation.
Aggregation mechanisms of amyloid β peptides depend on multiple intrinsic and extrinsic physicochemical factors (e.g., peptide chain length, truncation, peptide concentration, pH, ionic strength, ...temperature, metal concentration, etc.). Due to this high number of parameters, the formation of oligomers and their propensity to aggregate make the elucidation of this physiopathological mechanism a challenging task. From the analytical point of view, up to our knowledge, few techniques are able to quantify, in real time, the proportion and the size of the different soluble species during the aggregation process. This work aims at demonstrating the efficacy of the modern Taylor dispersion analysis (TDA) performed in capillaries (50 μm i.d.) to unravel the speciation of β-amyloid peptides in low-volume peptide samples (∼100 μL) with an analysis time of ∼3 min per run. TDA was applied to study the aggregation process of Aβ(1-40) and Aβ(1-42) peptides at physiological pH and temperature, where more than 140 data points were generated with a total volume of ∼1 μL over the whole aggregation study (about 0.5 μg of peptides). TDA was able to give a complete and quantitative picture of the Aβ speciation during the aggregation process, including the sizing of the oligomers and protofibrils, the consumption of the monomer, and the quantification of different early- and late-formed aggregated species.
The hydrolysis of valine N-carboxyanhydride (NCA) in aqueous phosphate buffers was shown to proceed through nucleophilic catalysis via an aminoacyl phosphate intermediate that displays ...phosphorylating capabilities through a potentially prebiotic process that simulates modern biochemical metabolic pathways.
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