Competitive ion-exchange adsorption of proteins: competitive isotherms with controlled competitor concentration

The competitive adsorption processes inevitably present in chromatographic separations of complex mixtures have not been extensively studied. This is partly due to the difficulty of measuring true competitive isotherms, in which all system parameters (including competitor concentrations) are held constant. We report a novel approach to determining competitive protein adsorption isotherms in which the competitor concentration is held constant across the entire isotherm. By using the heme prosthetic group in cytochrome b5 as a quantitative spectrophotometric label, competitive isotherms between cytochrome b5 and alpha-lactalbumin can be constructed. Similarly, manganese-substituted protoporphyrin IX heme replacement allows the non-perturbing labeling of individual cytochrome b5 conservative surface charge mutants by replacement of a single atom in the interior of the protein. This labeling allows the study of competition between cytochrome b5 charge mutants of identical size and shape, which differ only in charge arrangement. Using these techniques, the effect of competing species on equilibrium behavior and the apparent heterogeneity of anion-exchange adsorbents in the presence of competitors can be quantitatively studied by fitting the data to two popular single-component binding models, the Temkin and the Langmuir-Freundlich (L-F) isotherms.     

Nonstationary processes in an ion-exchange membranes-diaphragm-ion-exchange resin system. 2. Electroosmosis

Electroosmosis through a diaphragm and/or an ion-exchange resin layer has been experimentally studied at different relative positions thereof. The velocity of electroosmosis has been calculated with allowance for averaged field strengths found for the diaphragm and ion-exchange resin from the potential drop values measured for cell sections. It has been shown that the time dependences of electroosmosis velocity are related to nonstationary polarization processes proceeding in the system.     

Protein adsorption and transport in dextran-modified ion-exchange media. III. Effects of resin charge density and dextran content on adsorption and intraparticle uptake

Custom-synthesized variants of the commercial Capto S resin were used to examine the effects of resin charge density and dextran content on protein adsorption and intraparticle uptake. For the small protein lysozyme, resin charge density had the greatest effect on equilibrium capacity, consistent with calculations suggesting that lysozyme capacity should be limited by the available charge on the resin. Isocratic retention data and confocal microscopy imaging for this protein revealed a consistent ordering of the resins linking stronger protein-resin interactions with higher static capacities but slower intraparticle uptake rates over the range of properties studied. For the larger protein lactoferrin, it was found that increasing dextran content led to increased protein exclusion from the dextran layer, but that increasing resin charge density helped overcome the exclusion, presumably due to the increased electrostatic attraction between the resin and protein. Collectively examining the lysozyme and lactoferrin data along with information from previous studies suggests that a trade-off in maximizing dynamic capacities should exist between static capacities that increase to a finite extent with increased resin charge density and uptake rates that decrease with increased charge density. Column breakthrough data for lysozyme and lactoferrin appear to support the hypothesis, though it appears that whether a resin charge density is low or high must be considered in relation to the protein charge density. Using these trends, this work could be useful in guiding resin selection or design.     

Binary adsorption of globular proteins on ion-exchange media

Adsorption equilibrium of binary pairs of lysozyme (LYS), cytochrome c (CYC) and ribonuclease A (RNase) has been measured on different cation-exchange media at various solution conditions. Adsorption patterns largely follow the intrinsic protein–surface interactions, but can differ significantly for different pairs or even for one pair at different solution conditions. LYS/CYC adsorption shows similar behavior on all the adsorbents examined, with competitive adsorption dominated by LYS and the presence of LYS reducing the adsorption of CYC significantly. Simultaneous and sequential measurements for LYS/CYC show that the order of adsorption does not have a significant effect on the adsorption equilibrium. For LYS/RNase, LYS is consistently more strongly adsorbed. For CYC/RNase, both proteins can display significant adsorption, depending on the pH and salt concentration. A model based on colloidal energetics is developed to calculate the binary adsorption isotherms using parameter values obtained from single-component isotherms. The calculated adsorption is in good agreement with experimental results, with significantly better representation than for other commonly used binary isotherms.     

Atomic absorption spectrometric determination of trace copper in water by sorption on an ion-exchange resin and direct atomization of the resin

Traces of copper ions are sorbed on a cation-exchange resin, and a copper-loaded resin bead is inserted directly into a graphite furnace for atomic absorption spectrometry. The procedure is used for the determination of copper ( > 2 pg ml^?1) in tap and various distilled waters.     

Nonstationary processes in an ion-exchange membranes-diaphragm-ion-exchange resin system. 1. Concentration polarization

Potential drop distribution in a system comprising ion-exchange membranes, a diaphragm, and an ion-exchange resin layer has been experimentally studied and theoretically analyzed. It has been established that the potential drop is redistributed in the system due to not only different electrical resistances of its elements, but also their concentration polarization, which depends on both the voltage applied to electrodes and relative positions of the system elements.     

Microstructure and swelling behavior of ion-exchange resin

The microstructure and swelling kinetics of ion-exchange resins having sulfonic acid groups were investigated by small-angle neutron scattering (SANS) and swelling experiments as functions of the crosslinking density (CD), pH, and the salt concentration (C_salt). The swelling kinetics was analyzed on the basis of the Tanaka-Fillmore swelling equation for the cooperative diffusion of polymer gels. The swelling behavior was very sensitive to CD, but not to pH and C_salt. The SANS intensity functions, I(q), were independent of CD and well described with a power law function, I(q) ∼ q^−D, where q and D are the magnitude of the scattering vector and the mass-fractal dimension, respectively. D was estimated to be ∼2, indicating that the resin consisted of a rather coarsely interconnected domains irrespective of CD at swelling equilibrium. It was found that CD is the most important parameter determining the swelling power of ion-exchange resin. However, no remarkable variations were found in the microstructure in the order of tens to hundreds of angstrom. © 1996 John Wiley & Sons, Inc.     

Modeling of the dynamic adsorption of an anionic dye through ion-exchange membrane adsorber

The present study examines the dynamic adsorption through ion-exchange membrane adsorbers. The model used in the study includes convection, axial dispersion with simultaneous adsorption and desorption of the solute in the membrane. Adsorption and desorption processes give the Langmuir isotherm for the equilibrium. The mathematical model makes use of dimensionless parameters in terms of characteristic times for the different mechanisms that take place during the process (convection, dispersion, adsorption and desorption characteristic times). The model has five independent dimensionless parameters. Three of these parameters are related to the equilibrium isotherm and the other two are related to the dynamic process. Equilibrium and dynamic experiments were carried out in order to fit their respective parameters. In order to examine the suitability of the model to describe real processes, the adsorption of an anionic dye (Orange-G) through the ion-exchange membrane adsorber was investigated as a function of dye and KCl concentration, obtaining strong correlation between fitted and experimental breakthrough curves. The results show the relative importance of axial dispersion, adsorption and desorption as a function of operational variables.     

Synergistic flame-retardant effects of ammonium polyphosphate and AC-Fe2O3 in epoxy resin

Journal of Thermal Analysis and Calorimetry - The synergistic flame-retardant and smoke suppression properties of ammonium polyphosphate (APP) and activated carbon-supported Fe2O3 (AC-Fe2O3) on...     

Microchemical detection of hydrazines using ion-exchange resin grains

Summary By using colourless ion-exchange resins in the respective colour reactions of hydrazines with selenious acid and-naphthylamine, with diazotizedp-aminobenzaldehyde, with formaldehyde-tetrazobenzidine, and with formaldehyde-p-nitrobenzenediazonium salt, the sensitivities of these colour reactions can be increased. About 30 hydrazines have been tested by the present resin spot tests and the limits of identification are reported.

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Zusammenfassung Durch Anwendung farbloser Ionenaustauscherharze für Farbreaktionen von Hydrazinen mit Selenigsäure und-Naphthylamin, mit diazotiertem p-Aminobenzaldehyd, mit Formaldehyd und Tetrazobenzidin, mit Formaldehyd und p-Nitrobenzoldiazoniumsalz läßt sich die Empfindlichkeit dieser Reaktionen erhöhen. Etwa 30 Hydrazine wurden nach der angegebenen Harztüpfelmethode getestet und deren Nachweise mit üblichen Tüpfelreaktionen verglichen.

     

Development of a temperature-responsive agarose-based ion-exchange chromatographic resin

A temperature-responsive ion-exchange resin (ItBA) has been prepared by grafting poly(N-isopropylacrylamide-co-acrylic acid-co-tert-butylacrylamide; ItBA) onto cross-linked agarose. A carboxymethylated ion exchanger (CM) of similar charge density was also prepared. Maximum adsorption capacities (B_max) for lactoferrin at 20 °C and 50 °C were determined for both resins by batch adsorption procedures. Dynamic adsorption and desorption characteristics of the CM and ItBA with lactoferrin were established, as well as the ability of ItBA to selectively adsorb and desorb lactoferrin in the presence of other proteins. With the CM-agarose resin there was no significant difference between the B_max values obtained at 20 °C and 50 °C. However, for the agarose-based ItBA resin the B_max value at 50 °C was almost three times higher than the B_max value at 20 °C. Dynamically, lactoferrin adsorbed to the ItBA packed column at 50 °C with a significant proportion of the adsorbed lactoferrin desorbed by reducing the temperature to 20 °C. In addition, anionic proteins did not adsorb to the ItBA packed column, and did not interfere with the dynamic adsorption/desorption behaviour of lactoferrin. These results indicate that this new temperature-responsive agarose-based ItBA resin has potential for the fractionation of whey proteins, with good selectivity for cationic proteins.     

Microchemical detection of several elements using ion-exchange resin

Summary A new method of carrying out confirmatory tests is proposed. Colourless or slightly yellow anion-exchange resins are used as media for the tests. Both sensitivity and selectivity can be increased because of the well-known properties of ion-exchange resins. Co(IT) and Cr(VI) can be detected by very simple procedure; to a drop of sample solution a few particles of anion-exchange resin (RCl form) are added and after some time a drop of reagent [ammonium thiocyanate to Co(II) and hydrogen peroxide to Cr(VI)] is added. The change in colour of the particles of ion exchange resin is observed with the aid of magnifying glass. The limit of identification of sky blue colour of the cobalt complex is 0.16g and its limiting concentration is 1 1.3×10⁵. The limit of identification of violet-blue colour of the Cr(VI) complex is 0.3g and its limiting concentration is 1 10⁵. Ge(IV) can also be detected easily by a slightly modified method; the particles of an anion-exchange resin with low cross linking are previously impregnated with hematoxylin solution and those yellow particles are transfered to a drop of sample solution. The limit of identification of the red-violet colour of the Ge(IV) complex is 0.005g and its limiting concentration is 1 6×10⁶. Interfering substances, such as Fe³⁺ and Bi³⁺, can be removed completely with the aid of a cation-exchange resin which is added just before adding the particles of anion-exchange resin. The limiting proportions are also described in each case.

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Zusammenfassung Eine neue Methode für die Ausführung analytischer Nachweise wird vorgeschlagen. Hierzu werden farblose oder hellgelb gefärbte Anionenaustaiischer verwendet. Die Empfindlichkeit und Selektivität läßt sich infolge der bekannten Eigenschaften von Austauscherharzen steigern. Kobalt(II) und Chrom(VI) können in einfacher Weise nachgewiesen werden; zu einem Tropfen der Probelösung gibt man wenige Körnchen des Anionenaustauschers (RCl-Form) und setzt nach einiger Zeit einen Tropfen Reagens [Ammoniumrhodanid für Kobalt(II) und Wasserstoffperoxyd für Chrom(VI)] zu. Die Farbveränderung der Ionenaustauscherpartikel wird mit einem Vergrößerungsglas beobachtet. Die Erfassungsgrenze für die himmelblaue Farbe des Kobalt(II)komplexes beträgt 0,16g, die Grenzkonzentration 1 1,3·10⁵. Die Erfassungsgrenze für die violettblaue Farbe des Chrom(VI)-komplexes 0,3g, die Grenzkonzentration 1 10⁵. Germanium (IV) läßt sich ebenso leicht nach einer etwas abgeänderten Methode nachweisen; die Teilchen eines Anionenaustauscherharzes mit geringer Kettenverzweigung werden zunächst mit einer Hämatoxylinlösung imprägniert, dann bringt man diese gelb gefärbten Körnchen zu einem Tropfen der Probelösung. Die Erfassungsgrenze für die rotviolette Farbe des Germanium(IV)komplexes beträgt 0,0005.g, die Grenzkonzentration 1 6·10⁶. Störende Substanzen, wie Eisen(III) und Wismut(III), können mit Hilfe eines Kationenaustauschers, den man unmittelbar vor dem Anionenaustauscher zusetzt, vollständig entfernt werden. Die Grenzverhältnisse werden für jeden dieser Nachweise angegeben.

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Résumé L'auteur propose une nouvelle méthode permettant d'effectuer des tests de confirmation. A cet effet, on emploie des résines échangeuses d'anions incolores ou légèrement jaunâtres. Les propriétés bien connues des résines échangeuses d'ions permettent d'obtenir une sensibilité et une sélectivité accrues. Le cobalt(II) et le chrome(VI) peuvent être décelés de façon très simple: à une goutte de la solution à étudier on ajoute quelques particules de résine échangeuse d'anion (de forme RCl) puis, après un certain temps, une goutte de réactif (thiocyanate d'ammonium dans le cas du cobalt II et eau oxygénée dans le cas du chrome VI). On observe à l'aide d'une loupe le changement de coloration des particules de la résine échangeuse d'ions. Pour le bleu ciel du cobalt, la limite d'identification est 0,16g et la concentration limite 1 3×10⁵. Pour le complexe bleu violacé du chrome(VI) elle est de 0, 3g et la concentration limite 1 10⁵. A l'aide d'une légère modification de la méthode il devient également possible de déceler Ge(IV): les particules d'une résine échangeuse d'anions à chaîne peu ramifiée sont préalablement imprégnées d'une solution d'hématoxyline; elles ont alors une coloration jaune et sont introduites dans une goutte de solution à étudier. La coloration rouge violacé du complexe de Ge(IV) permet d'atteindre une limite d'identification de 0,005g et une concentration limite d'identification de 0,005g et une concentration limite de 1 6×10⁶. Les substances gênantes telles que Fe³⁺ ou Bi³⁺ peuvent être éliminées complètement à l'aide d'une résine échangeuse de cations que l'on introduit immédiatement avant l'addition des particules de la résine échangeuse d'anions. Les proportions limites sont également indiquées dans chaque cas.

     

Identification of selective ion-exchange resin for fluoride sorption

The defluoridation capacity (DC) of a chelating resin, namely Indion FR 10 (IND), and Ceralite IRA 400 (CER), an anion-exchange resin, were compared under various equilibrating conditions for the identification of selective sorbent. The results showed that chelating resin is more selective than an anion-exchange resin for fluoride removal. The fluoride sorption was reasonably explained using Freundlich and Langmuir isotherms. The surface morphology of resins before and after fluoride sorption was observed using scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) was used for the determination of functional groups responsible for fluoride sorption. Various thermodynamic parameters such as DeltaG0, DeltaH0, DeltaS0, and Ea have been calculated to understand the nature of sorption. The sorption kinetic mechanism was studied with reaction-based and diffusion-based models. The sorption process was found to be controlled by pseudo-second-order and particle diffusion models. The performance of the resins studied has been tested with field samples collected from a fluoride-endemic area.     

Base-dependent competitive adsorption of single-stranded DNA on gold

We characterize the room-temperature adsorption of single-stranded DNA homo-oligonucleotides from solution onto polycrystalline Au films, including competitive adsorption between all possible pairs of unmodified oligomers. Fourier transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopy analysis of the resulting films shows that oligonucleotides adsorb with a strongly base-dependent affinity, adenine (A) > cytosine (C) >/= guanine (G) > thymine (T). In competitive adsorption experiments on Au, oligo(dA) strongly dominates over the other oligonucleotides. The relative adsorption affinity of oligo(dA) is so great that it competes effectively against adsorption of thiolated oligomers and even causes hybridized oligo(dA).oligo(dT) duplexes to denature in the presence of Au.     

大孔吸附树脂对天麻素的吸附与分离特性的研究

研究了AB 8、NKA 9和S 83种大孔吸附树脂对中药天麻提取液中有效成分天麻素的吸附与分离特性。结果表明,NKA 9和S 8树脂对天麻素具有较好的吸附和解吸特性。其中经NKA-9树脂纯化的天麻素纯度为16.4%,比粗提物的天麻素纯度提高了1倍多。     

Studies on the adsorption behaviors of Pb(II) onto an acyl-thiourea resin

In this paper, an acyl-thiourea resin (PIDTR) was synthesized and its adsorption performances to Pb(II) were investigated by adsorption tests, scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses. A pH of 6.0 was found to be the optimum pH to obtain the maximum adsorption capacity in 12 hours of equilibration time. The Langmuir model was well fitted to the adsorption data with adsorption capacity of 0.756?mmol?·?g^?1. The adsorption kinetics showed that the adsorption process experienced liquid film diffusion and chemical reaction. The thermodynamic studies indicated that the adsorption for Pb(II) was spontaneous and endothermic. The results of SEM suggested that Pb(II) adsorbed on the surface of PIDTR. The FTIR and XPS analyses further confirmed Pb(II) might chemisorb onto PIDTR surfaces and N–Pb, O–Pb, and S–Pb were formed with the breakage of C?O, C?S, and N-H bonds in the PIDTR molecule.     

A predictive approach to correlating protein adsorption isotherms on ion-exchange media

The equilibrium adsorption of three small basic proteins was measured on cation exchangers under various solution conditions and was used as the basis for developing a predictive approach for correlating adsorption behavior. A mechanistically based isotherm model is used to model the equilibrium adsorption so as to facilitate isotherm prediction using minimal experimental data. The model explicitly considers the contributions of protein-surface and protein-protein interactions, and decoupling them allows each to be correlated with different experimental measurements. Specifically, protein-surface interactions are related to chromatographic data in the form of the isocratic retention factor (k'), while protein-protein interactions are analyzed on the basis of high-coverage isotherm data on an arbitrary stationary phase. Analysis of experimental data within this framework reveals a high level of consistency. The model is also used to facilitate prediction of adsorption isotherms on other ion-exchange media using isotherms on one adsorbent.