Octaethylene Glycol Mono Research Articles

Micellar size changing in the systems of octaethylene glycol mono(n-dodecyl) ether without and with poly(acrylic acid)

Aqueous octaethylene glycol mono(n-dodecyl) ether (C12E8) solutions, in the absence and presence of poly(acrylic acid) (PAA) are studied by means of viscosity, pH, refractive index, static fluorescence and dynamic light scattering measurements. At high surfactant concentrations, these properties present inflection points. They are different by the classical critical points (critical micelle concentration and critical interaction concentrations) of such systems and appear at almost the same surfactant concentration, irrespective of the polymer presence. The results are interpreted in terms of micellar size and shape changes. Some images collected with two microscopes prove these changes and the coexistence of various shaped aggregates.

Comparing the spectral properties of pyrene as free molecule, label and derivative in some colloidal systems

This paper investigates the behavior of pyrene as free molecule (probe), label and derivative in some colloidal systems. Aqueous octaethylene glycol mono n-dodecyl ether (C12E8) with or without poly(acrylic acid) (PAA), and a hydrophobically modified polyacrylate are considered. The effect of C12E8 on PAA labeled with pyrene is also studied. As a probe, pyrene has a typical behavior in the absence or presence of PAA. The labeled PAA has the peak corresponding to the sandwich excimer even in the absence of surfactant. The pyrene derivative is 4-(N′,N′-diphenyl-hydrazine)-3,5-dinitrobenzoic acid 2-oxo-2-pyren-2-yl-ethyl ester. Its fluorescence emission is low and bathochromically shifted by 9nm with respect to pyrene. The low fluorescence emission of derivative is due to its self-quenching. The data reveal that pyrene probe is located in the free or polymer-bound micelles. The labels on PAA create hydrophobic domains and shrink the polymer coil. By surfactant addition, labeled pyrene is solubilized in micelles palisade layer, closer to the ethylene oxide (EO) chains. The derivative is also located into the micellar palisade layer, in the proximity of the EO groups. The fluorophore behavior is discussed in relation to the critical points of surfactant and polymer–surfactant systems.

Changes in Octaethyleneglycol Mono N-Dodecyl Ether Micelles in Aqueous 1,4-Dioxane Solutions

The structures of micelles of the surfactant Octaethyleneglycol mono n-dodecyl ether (C12E8, BL-8SY) in 0-80% aqueous 1,4-dioxane solutions (pH 7.2, ionic strength 2.44 mM) were investigated by small-angle X-ray scatter- ing. C12E8 forms the core-shell discus micelle in 0-80% aqueous 1,4-dioxane solutions. Changing properties of aqueous 1,4-dioxane solution did not affect the outside-shapes of C12E8 micelles; however, it might be resulted in changing the structures of C12E8 micelles from normal core-shell discus micelles to reverse core-shell discus micelles in 1,4-dioxane concentrations between 40 and 60%.

Use of Glycerol-Containing Media To Study the Intrinsic Fluorescence Properties of Detergent-Solubilized Native or Expressed SERCA1a

Rapid irreversible inactivation of Ca (2+)-free states of detergent-solubilized SERCA1a (sarco-endoplasmic reticulum calcium ATPase 1a) has so far prevented the use of Trp fluorescence for functional characterization of this ATPase after its solubilization in various detergents. Here we show that using 20-40% glycerol for protection makes this fluorescence characterization possible. Most of the ligand-induced Trp fluorescence changes previously demonstrated to occur for SERCA1a embedded in native sarcoplasmic reticulum membranes were observed in the combined presence of glycerol and detergent, although the results greatly depended on the detergent used, namely, octaethylene glycol mono- n-dodecyl ether (C 12E 8) or dodecyl maltoside (DDM). In particular, at pH 6, we found a C 12E 8-dependent unexpectedly huge reduction in SERCA1a affinity for Ca (2+). We suggest that a major reason for the different effects of the two detergents is that high concentrations of C 12E 8, but not of DDM, slow down the E2 to E1 transition in solubilized and delipidated SERCA1a. Independently of the characterization of the specific effects of various detergents on SR vesicles, our results open the way to functional characterization by Trp fluorescence of heterologously expressed and purified mutants of SERCA1a in the presence of detergent, without their preliminary reconstitution into liposomes. As an example, we used the E309Q mutant to demonstrate our previous suspicion that Ca (2+) binding to Site I of SERCA1a in fact slightly reduces Trp fluorescence, and consequently that the rise in this fluorescence generally observed when two Ca (2+) ions bind to WT SERCA1a mainly reflects Ca (2+) binding at Site II of SERCA1a.

Layer-by-layer deposition of shortened nanotubes or polyethylene glycol-derivatized nanotubes on liposomes: A tool for increasing liposome stability

A simple strategy for preparing potential drug delivery systems is presented which appears to be a good alternative to stealth liposomes in terms of stability in buffered aqueous solutions. Microcapsules have been prepared by deposition of shortened and polyethylene glycol-derivatized nanotubes onto positively charged multilamellar vesicles using the layer-by-layer technique. The stability of microcapsules has been determined turbidimetrically by measuring the rate of microcapsule breakdown induced by addition of a destabilizing agent such as the nonionic surfactant octaethyleneglycol mono- n-dodecyl ether. The investigated microcapsules have proven to be more stable than both pure liposomes and stealth liposomes.

The aggregation of nonionic surfactants in the presence of poly(methacrylic acid)

The solution properties of homogeneous hexaethylene and octaethylene glycol mono(n-dodecyl) ethers, C12E6 and C12E8, respectively, and octaethylene glycol mono(n-decyl) ether, C10E8, with poly(methacrylic acid) (PMA) were investigated by dye solubilization, surface tension, fluorescence, viscosity, and pH measurements. The data were discussed regarding non-cooperative and cooperative binding of surfactant to polymer. Whereas in the interaction with poly(acrylic acid) (PAA), the critical aggregation concentrations (cac or T 1) of these surfactants were lower than the respective critical micelle concentration (cmc), in that with the more hydrophobic PMA, T 1’s of C12E6 and C12E8 were higher than the respective cmc, but that of C10E8 was lower than its cmc. These may be ascribed to the hydrophobic microdomains (HMD) of the PMA coil in water, probably in its inside. It is considered that some surfactants are bound first to the HMD non-cooperatively and then they are abruptly bound cooperatively at T 1. This raises T 1 higher than cmc when the cmc is low, and the amount bound by the HMD is relatively large and vice versa. T 1 of C12E6 or C12E8 is the former case, and that of C10E8 is the latter. Thus, different from PAA, T 1 for PMA + nonionic surfactant system consists of the amount of non-cooperative binding and the cac of the cooperative binding in equilibrium. Therefore, this T 1 has a different meaning from that for PAA and should be called apparent T 1. As the binding to the HMD is dependent on PMA concentration and cac is not, which is like in the PAA system, separation of apparent T 1 from the HMD binding was achieved by extrapolating T 1’s to zero PMA concentration (denoted intrinsic T 1). This value for C12E8 was found to be lower than the respective cmc and also lower than the respective T 1 for PAA. With increase in surfactant concentration, the pH of PMA solution rose and demonstrated a peak. This pH rise and fall may be induced by loosening of the HMD coil due to binding increase and by rearrangement of PMA + surfactant complex in high surfactant concentrations region. By raising the initial pH, the HMD were loosened; consequently, T 1 rose a little, and at higher pH, no surfactant binding took place.

Dioctadecyldimethylammonium bromide vesicles prepared by the surfactant removal method

Dioctadecyldimethylammonium bromide (DODAB) is a double chain vesicle-forming cationic surfactant, whereas octa-ethyleneglycol mono- n-dodecyl ether (C 12E 8) is a single chain micelle-forming nonionic surfactant. At room temperature (ca. 22 °C) C 12E 8 molecules self-assemble in water as micelles while DODAB is insoluble. A mixture of DODAB and C 12E 8, however, can be soluble in water at room temperature depending on the relative amount of the compounds. We report the formation of small unilamellar vesicles (SUVs) by dialyzing at room temperature a mixture of 1.0 mM DODAB with 10 mM C 12E 8 in water. Extended bilayers are formed as well in equilibrium with vesicles. Such structures are viewed by a cryogenic transmission electron microscopy (cryo-TEM) image.

Noninteracting versus Interacting Poly(N-isopropylacrylamide)-Surfactant Mixtures at the Air−Water Interface

Two polymer-surfactant mixtures have been studied at the air-water interface using neutron reflectivity and surface tension techniques. For the noninteracting system poly(N-isopropylacrylamide) (PNIPAM)/octaethyleneglycol mono n-decyl ether (C10E8), the adsorption behavior is competitive and driven purely by surface pressure (pi). When pi(polymer) > pi(surfactant), the surface layer consists of almost pure polymer, and for pi(polymer) < pi(surfactant), the polymer is displaced from the surface by the increasing pressure of the surfactant. Beyond the CMC, the polymer is completely displaced from the surface. For the interacting system PNIPAM/sodium dodecyl sulfate (SDS) where the two species interact strongly in the bulk beyond the critical aggregation concentration (CAC), the surface behavior is more original. Earlier neutron reflectivity studies investigated PNIPAM adsorption behavior where the SDS was contrast-matched to the solvent. In the present study, complementary measurements of SDS adsorption where PNIPAM is contrast-matched to the solvent give a complete view of the surface composition of the mixed system. At a constant polymer concentration, with increasing SDS, three main regimes are obtained. For C(SDS) < CAC, adsorption is governed by simple competition and PNIPAM is predominant at the interface. At intermediate SDS concentration (CAC < C(SDS) < x2, where x2 indicates the predominance of free SDS micelles), interfacial behavior is governed by bulk polymer-surfactant interaction. Adsorbed polymer is displaced from the interface to form PNIPAM-SDS complex in the bulk. SDS adsorption remains weak since most of the SDS molecules are used to form bulk polymer-surfactant aggregates. Further increase in SDS concentration results in continued displacement of PNIPAM and an abrupt increase in SDS adsorption. This is a result of saturation of bulk polymer chain with adsorbed micelles. Interestingly, beyond x2, PNIPAM is not completely displaced from the surface. A mixed PNIPAM-SDS adsorbed layer with enhanced packing of the SDS monolayer is formed.

Modeling of the Adsorption Kinetics of Surfactants at the Liquid−Fluid Interface of a Pendant Drop

This paper presents a theoretical model for simulating the adsorption kinetics of a surfactant at the liquid-fluid interface of a pendant drop. The diffusion equation is solved numerically by applying the semidiscrete Galerkin finite element method to obtain the time-dependent surfactant concentration distributions inside the pendant drop and inside the syringe needle that is used to form the pendant drop. With the obtained bulk surfactant concentration distributions, the adsorption at the interface is determined by using the conservation law of mass. It should be noted that the theoretical model developed in this study considers the actual geometry of the pendant drop, the depletion process of the surfactant inside the pendant drop, and the mass transfer of the surfactant from the syringe needle to the pendant drop. The present pendant-drop model is applied to study the adsorption kinetics of surfactant C10E8 (octaethylene glycol mono n-decyl ether) at the water-air interface of a pendant drop. The numerical results show that the Ward and Tordai equation, which was derived for adsorption from a semi-infinite surfactant solution to a planar interface, is unsuitable for interpreting the dynamic surface or interfacial tension data measured by using the pendant-drop-shape techniques, especially at low initial surfactant concentrations. The spherical-drop model, which assumes the pendant drop to be a perfectly spherical drop with the same drop volume, can be used to interpret the dynamic surface or interfacial tension data for pendant drops either with high initial surfactant concentrations or with low initial surfactant concentrations in short adsorption durations only. For pendant drops with low initial surfactant concentrations in long adsorption durations, the theoretical model developed in this study is strongly recommended.

Characterisation of nickel(II) extraction by 2-hydroxy-5-nonylacetophenone oxime (LIX 84) in a micellar phase

The properties of the nickel(II)/2-hydroxy-5-nonylacetophenone oxime (HNAPO), an active ingredient in LIX 84, extraction system were characterised in a micellar system. The extinction coefficient, λ max of HNAPO (316 nm) and the Ni 2+ complex (387 nm) in a neutral micellar system, poly dispersed octa-ethyleneglycol mono- n -dodecyl ether (G 12 A 8 ) were determined as 3100 and 3500 M −1 cm −1 , respectively. HNAPO was found to have a neutral micellar phase and bulk aqueous phase p K a of 11.5 and 12.5, respectively. The extraction equilibrium constant, K ex, was determined to be 10 −8.0 , and the deviation from theory observed at high pH can be accounted for by consideration of the competition for nickel(II) ions by hydroxide ions and HNAPO. A micellar phase of octa-ethyleneglycol mono- n -dodecyl ether (C 12 E 8 ) was determined to be an appropriate model of the free oil/water interface from the solubilised location of HNAPO. Utilising the interfacial probe, 4-heptadecyl-7-hydroxy coumarin (HHC) allowed the determination of the electrostatic surface potential of mixed micelles of G 12 A 8 and sodium dodecyl sulphate (SDS) or dodecyl trimethyl ammonium chloride (DTAC). The electrostatic surface potential was a linear function of the number of additional surfactant monomers within the G 12 A 8 micelle, for the concentration range studied. For G 12 A 8 /DTAC mixed micelles, the surface potential was given by +1.1 mV per DTAC molecule per micelle, and for G 12 A 8 /SDS mixed micelles the relationship was −1.4 mV per SDS molecule per micelle.

Spin Probe Study on the Interaction of Chitosan-Derived Polymer Surfactants with Lipid Membrane

Chitosan-derived polymer surfactants, sulfated N-acyl-chitosan (S–Cn–Chitosan), were synthesized and compared with commonly used low-molecular-weight surfactants, sodium dodecyl sulfate (SDS), dodecyltrimethyl ammonium chloride (DTAC), and octaethyleneglycol mono n-dodecyl ether (BL8SY), in their interaction with a lipid membrane using a spin probe method. A suspension of dipalmitoylphosphatidyl-choline (DPPC) spin-labeled strongly (10%) with a spin probe, 1-palmitoyl-2-(12-doxyl) stearoyl-phosphatidylcholine, was mixed with the surfactant solutions. The dissolution time of the DPPC membrane was estimated from the peak height change vs time, which was caused by the decrease in spin–exchange interaction. The times were 2, 4, and 70 s for BL8SY, SDS, and DTAC and 1.2 and 8.8 h for S–C10–Chitosan and S–C14–Chitosan, respectively, showing that the dissolution of the lipid membrane with polymer surfactants was far slower than that with low-molecular-weight surfactants. In addition, the time depended on the length of the alkyl chains of the polymer surfactants. Simulations of the ESR spectra of the DPPC-surfactant systems containing small amounts of surfactants were carried out in order to examine how the membrane structure was changed by the incorporation of surfactant molecules. By this analysis, it was revealed that the rigidity of the membrane was decreased by the addition of low-molecular-weight surfactants in the order of DTAC>SDS>BL8SY, inverse to the order of dissolution times. S–Cn–Chitosan, in contrast, increased the rigidity of the membrane, suggesting that polymer surfactants adhered to the lipid membrane and tightly enfolded the riposome anchoring their alkyl chains.

Overproduction in yeast and rapid and efficient purification of the rabbit SERCA1a Ca 2+-ATPase

Large amounts of heterologous C-terminally his-tagged SERCA1a Ca 2+-ATPase were expressed in yeast using a galactose-regulated promoter and purified by Ni 2+ affinity chromatography followed by Reactive red chromatography. Optimizing the number of galactose inductions and increasing the amount of Gal4p transcription factor improved expression. Lowering the temperature from 28°C to 18°C during expression enhanced the recovery of solubilized and active Ca 2+-ATPase. In these conditions, a 4 l yeast culture produced 100 mg of Ca 2+-ATPase, 60 and 22 mg being pelleted with the heavy and light membrane fractions respectively, representing 7 and 1.7% of total proteins. The Ca 2+-ATPase expressed in light membranes was 100% solubilized with L-α-lysophosphatidylcholine (LPC), 50% with n-dodecyl β- D-maltoside (DM) and 25% with octaethylene glycol mono- n-dodecyl ether (C 12E 8). Compared to LPC, DM preserved specific activity of the solubilized Ca 2+-ATPase during the chromatographic steps. Starting from 1/6 (3.8 mg) of the total amount of Ca 2+-ATPase expressed in light membranes, 800 μg could be routinely purified to 50% purity by metal affinity chromatography and then 200 μg to 70% with Reactive red chromatography. The purified Ca 2+-ATPase displayed the same K m for calcium and ATP as the native enzyme but a reduced specific activity ranging from 4.5 to 7.3 μmol ATP hydrolyzed/min/mg Ca 2+-ATPase. It was stable and active for several days at 4°C or after removal of DM with Bio-beads and storage at −80°C.

Comparing Decyl-β-maltoside and Octaethyleneglycol Mono n-Decyl Ether in Mixed Micelles with Dodecyl Benzenesulfonate: 2. Interaction of Mixed Micelles with Polyvinylpyrrolidone

The interactions between polyvinylpyrrolidone (PVP) and a mixture of anionic and nonionic surfactants have been investigated by surface tension measurements. The surfactant mixtures are decyl-β-maltoside (C10M) with dodecyl benzenesulfonate (C12BS) and octaethyleneglycol mono n-decyl ether (C10EO8) with C12BS. Surface tension measurements of the surfactant mixtures in the presence of PVP show that C10EO8 competes more effectively than C10M with PVP in the interaction with C12BS.

Comparing Decyl-β-maltoside and Octaethyleneglycol Mono n-Decyl Ether in Mixed Micelles with Dodecyl Benzenesulfonate: 1. Formation of Mixed Micelles

In this study the mixed micelle behavior of an alkyl polyglycoside is compared to a surfactant of polyoxyethylene type, by means of surface tension measurements. The two nonionic surfactants are compared in mixed micelle systems together with an anionic surfactant. The surfactant mixtures are: decyl-β-maltoside (C10M) with dodecyl benzenesulfonate (C12BS) and octaethyleneglycol mono n-decyl ether (C10EO8) with C12BS. The mixture of C10M and C10EO8 is also studied. Critical micelle concentration (CMC) and the concentration at which the surface tension reduction is 20 mNm−1 (C20) are determined at different mixing ratios of the surfactant mixtures. By applying the nonideal mixed micelle theory, interaction parameters at CMC (βCMC) and C20 (βC20) are calculated for the surfactant mixtures. The results show that the C10M–C12BS mixture has a βCMC parameter of −2.1, whereas the βCMC parameter for the C10EO8–C12BS mixture is −3.3, indicating a weaker net attractive interaction between C10M and C12BS than between C10EO8 and C12BS. This is attributed to a small negative and positive charge of the respective nonionic surfactants. This is supported by a slightly negative βCMC parameter obtained for the surfactant mixture C10M–C10EO8, indicating a small net attractive interaction between the two nonionic surfactants.

A quartz crystal microbalance study of the removal of solid organic soils from a hard surface in aqueous surfactant solution

A quartz crystal microbalance (QCM) has been employed to monitor the removal of two model solid organic soils, dotriacontane and tripalmitin, from the hard surface of the QCM crystal in aqueous surfactant solutions of octa-ethyleneglycol mono n-dodecyl ether (C 12E 8). We have investigated the effect of varying the thickness of the soil coating on soil removal and the effect of soaking the soil in high-purity water for an extended period of time before adding surfactant. The QCM results support the view that net soil removal is preceded by a stage of water and surfactant penetration into the soil. The rate of penetration and rate of removal depends on the soil type. Water and surfactant take longer to penetrate dotriacontane compared to tripalmitin coatings. The removal process also occurs over a longer period of time in the case of dotriacontane coatings. The percentage of material removed is less for dotriacontane, compared to tripalmitin coatings. The initial coating thickness on the hard surface does not appear to govern the final percentage of soil removed, at least in the thickness range accessible to the QCM (approximately ≤800 nm). Immersing the soil coated surfaces in water for a relatively long time, hastens the onset of the removal stage after surfactant is added but does not significantly influence the rate and extent of removal from the hard surface.

The Reduction in Electroporation Voltages by the Addition of a Surfactant to Planar Lipid Bilayers

The effects of a nonionic surfactant, octaethyleneglycol mono n-dodecyl ether (C 12E 8), on the electroporation of planar bilayer lipid membranes made of the synthetic lipid 1-pamitoyl 2-oleoyl phosphatidylcholine (POPC), was studied. High-amplitude (∼100–450 mV) rectangular voltage pulses were used to electroporate the bilayers, followed by a prolonged, low-amplitude (∼65 mV) voltage clamp to monitor the ensuing changes in transmembrane conductance. The electroporation thresholds of the membranes were found for rectangular voltage pulses of given durations. The strength-duration relationship was determined over a range from 10 μs to 10 s. The addition of C 12E 8 at concentrations of 0.1, 1, and 10 μM to the bath surrounding the membranes decreased the electroporation threshold monotonically with concentration for all durations ( p < 0.0001). The decrease from control values ranged from 10% to 40%, depending on surfactant concentration and pulse duration. For a 10- μs pulse, the transmembrane conductance 150 μs after electroporation ( G 150) increased monotonically with the surfactant concentration ( p = 0.007 for 10 μM C 12E 8). These findings suggest that C 12E 8 incorporates into POPC bilayers, allowing electroporation at lower intensities and/or shorter durations, and demonstrate that surfactants can be used to manipulate the electroporation threshold of lipid bilayers.

Effect of nonionic surfactant addition on bacterial metabolism of naphthalene: Assessment of toxicity and overflow metabolism potential

Two factors potentially accounting for the variability of bioremediation outcomes when surfactant micelles are used to increase polycyclic aromatic hydrocarbon (PAH) bioavailability were investigated: (1) surfactant toxicity and (2) the link between microbial metabolism and the intended effect of surfactant addition, enhanced solubilization and mass transfer from a solid phase. The nonionic surfactant, octaethyleneglycol mono n-dodecyl ether, did not alter the metabolism of succinate and glucose by an isolate from a creosote-contaminated soil indicating that the surfactant is nontoxic. When the culture was supplied with solid naphthalene, growth was limited by the dissolution of solid naphthalene after the aqueous-phase naphthalene was depleted. Moreover, increasing dissolution rate by increasing interfacial surface area increased the microbial growth rate. However, increasing bioavailability further by increasing interfacial surface area, introducing convective mass transfer, and adding surfactant were all found to reduce growth rate and prompt incomplete metabolism of naphthalene to a compound whose UV absorption corresponds to 1,2-naphthaquinone. Lowering the surfactant concentration diminished the metabolic overflow and permitted sustained growth. The results suggest that different mismatches between solubilization/mass transfer and metabolic capacity may be among the factors responsible for variable bioremediation outcomes.

Some critical points in the interaction between homogeneous non-ionic surfactants and poly(acrylic acid)

Single hexaethylene glycol mono( n-dodecyl) ether or octaethylene glycol mono( n-dodecyl) ether in aqueous solution and their mixtures with poly(acrylic acid) (PAA) were studied by surface tension, fluorescence, dye solubilization, viscosity and pH methods. The CMC and several critical surfactant concentrations for the interaction were determined. The starting point of micellar aggregation on the PAA chain ( T 1) and the point at which free micelles appeared in the solution were found and identified by the various methods. The concentration at which free surfactant molecules reappear in the system, was a transitional range rather than a critical point and was identified with certainty only by surface tension measurements. The data were discussed taking into account the interaction of both ethoxylated and hydrophobic moieties of the surfactant with PAA (i.e. hydrogen bonding and hydrophobic bonding respectively). Finally, the relationship between T 1 and the ethoxylated and hydrophobic moieties of the surfactants was considered.

Phase behaviour of systems of a non-ionic surfactant and a non-ionic polymer in aqueous solution

The phase behaviour of different non-ionic surfactant/non-ionic polymer/water systems has been studied. The surfactants investigated are tetraethylene glycol mono( n-dodecyl) ether (C 12E 4) and octaethylene glycol mono( n-dodecyl) ether (C 12E 8), and the polymers chosen are a linear random copolymer of ethylene oxide and propylene oxide (UCON) and ethyl hydroxyethyl cellulose (EHEC); all components display a lower consolute curve. The phase behaviour is strongly dependent on the distances from the phase separation limits of the two components, except that the phase behaviour of systems with a given polymer is similar. However, on changing the polymer, a marked change in phase behaviour is displayed. For systems with UCON, the miscibility between the surfactant and the polymer is of crucial importance in determining the phase behaviour. The polymer and the surfactants simply act as a preferred solvent for each other compared to water. In this case, the cloud points of the ternary mixtures depend essentially on the component with the lowest solubility, i.e. UCON in the C 12E 8/UCON/water mixture and C 12E 4 in the C 12E 4/UCON/water mixture. When the component with the higher solubility (C 12E 8 in C 12E 8/UCON/water and UCON in C 12E 4/UCON/water) is substituted for water, the lower consolute boundary shifts upwards. In systems with EHEC, however, the lower consolute boundaries pass through a minimum on adding surfactant to a binary EHEC—water solution, which could be attributed to an attractive interaction and the formation of a strong complex between the polymer and the surfactant.

Enzymatic deglycosylation of human Band 3, the anion transport protein of the erythrocyte membrane. Effect on protein structure and transport properties.

The structural and functional roles of the single asparagine (N)-linked oligosaccharide chain of Band 3 (AE1), the anion transport protein of the human erythrocyte membrane, were examined. Purified Band 3 (M(r) = 95,000) in 0.1% octaethylene glycol mono n-dodecyl ether (C12E8) detergent solution was deglycosylated using N-glycosidase F. This treatment sharpened the protein band on sodium dodecyl sulfate gel electrophoresis and decreased its apparent molecular weight by 5,000. The purified membrane domain could be deglycosylated under similar conditions, causing a shift from a broad band centered at 55 kDa to a sharp 46-kDa band. Band 3 was shown to bind tomato lectin, and loss of lectin binding on blots provided a sensitive assay for deglycosylation. Carbohydrate analysis revealed that greater than 80% of the oligosaccharide could be removed from Band 3 by N-glycosidase F digestion. The deglycosylated protein maintained its dimeric structure and level of detergent binding but had a smaller Stokes radius (RS = 72 A) than native Band 3 (RS = 75 A). The Stokes radius of the membrane domain (RS = 60 A) also decreased upon deglycosylation (RS = 58 A). Circular dichroism studies showed that deglycosylation did not change the secondary structure of Band 3 or the membrane domain. The sensitivity of Band 3 or the membrane domain to proteolytic digestion by trypsin or proteinase K was also unaffected by deglycosylation. The deglycosylated protein aggregated more rapidly and was much more readily precipitable by ammonium sulfate. The deglycosylated protein bound the anion transport inhibitor 4-benzamido-4'-amino-stilbene-2,2'-disulfonate with the same affinity (Kd = 1 microM) as the native protein. Transport studies using reconstituted Band 3 and resealed ghosts showed that deglycosylated Band 3 retained its ability to transport anions. We conclude that removal of the oligosaccharide chain from Band 3 and any resultant structural changes had no effect on the transport function of this protein.