Range Of Ionic Strengths Research Articles

Nanopore-Confined Bilayers: A Model of Biomembranes with Defined Curvature and a Tool for Oriented Sample Magnetic Resonance

It is well established that biological function of cellular membranes is determined by both membrane proteins and the membrane biochemical composition. Moreover, the membrane shape/local curvature may also play a role in modulating membrane properties and the proteins’ function. While specific biomembrane compositions are more readily replicated in biophysical bench experiments, formation of bilayers of specific shapes and curvature represents a more challenging task. Macroscopic alignment of such membranes – an important prerequisite of high resolution magnetic resonance and other studies – is even more difficult especially over a broad range of experimental conditions such pH, ionic strength, and temperature. Here we describe methods for forming self-assembled lipid nanotubular bilayers inside cylindrical nanopores composed of anodic aluminum oxide (AAO). Such hybrid nanostructures, named lipid nanotube arrays, represent a new type of substrate-supported and macroscopically-aligned lipid bilayers of defined curvature that have many attractive features for both membrane biophysics and structure-function protein studies by spectroscopic techniques. Optical properties of AAO allow for assessing the integrity of membrane protein complexes by UV-vis while high density of the deposited lipids and proteins enable examination by other biophysical methods, including DSC, QCM, and magnetic resonance. The latter studies have shown that the individual lipids in such nanopore-confined structures maintain fast uniaxial diffusion and a high degree of macroscopic alignment. The macroscopic alignment enables detailed studies of effects of lipid composition on structure of integral membrane proteins by solid state oriented sample NMR, EPR and DEER. Accessibility of either both or mainly inner leaflet of the nanotubular bilayers to water-soluble species provides for studies of protein, peptides, and drug binding. Supported by DE-FG02-02ER15354 to AIS.

The role of nanofiltration membrane surface charge on the scale-prone ions concentration polarization for low or medium saline water softening

Based on the fact that when inlet bulk solution with low or medium concentration was involved, scaling was apt to appear on nanofiltration (NF) membrane surface in retentate side. Therefore, study on its surface charge performance under threshold concentration condition is necessary. Two polyamide composite NF membranes (DL and DK) were characterized with streaming potential (Es), zeta (ξ) potential and other measurements encountering with a wide ionic strength range (1.5–108 mol·m−3). Then, the interactional relations between membrane surface charge and concentration polarization (CP) degree, along with the relevant constituting factors were investigated. The results showed that even when the sparingly soluble salt concentration for CaSO4 exceeded its threshold point, both NF membranes at pressure drop of 180 kPa still exhibited low and medium-intensity surface electrokinetic phenomena (−5.94 ≤ Es ≤ −3.41 mV; −38.82 ≤ ξ-potential ≤ −36.34 mV). It turned out that solvent flux decreased almost linearly, but measured concentrations of the scalant ions in NF retentate streams increased slightly at first and then rapidly with the enlargement of ξ-potential, respectively. Meanwhile, mass transfer coefficient and boundary layer thickness had a negligible change in the scope of testing ξ-potential. Therefore, CPSO42− and CPCa2+ decreased apparently with ξ-potential becoming less negative for the adopted NF membranes.

One-Pot Multi-Enzymatic Production of Purine Derivatives with Application in Pharmaceutical and Food Industry

Biocatalysis reproduce nature’s synthetic strategies in order to synthesize different organic compounds. Natural metabolic pathways usually involve complex networks to support cellular growth and survival. In this regard, multi-enzymatic systems are valuable tools for the production of a wide variety of organic compounds. Methods: The production of different purine nucleosides and nucleoside-5′-monophosphates has been performed for first time, catalyzed by the sequential action of 2′-deoxyribosyltransferase from Lactobacillus delbrueckii (LdNDT) and hypoxanthine-guanine-xanthine phosphoribosyltransferase from Thermus themophilus HB8 (TtHGXPRT). Results: The biochemical characterization of LdNDT reveals that the enzyme is active and stable in a broad range of pH, temperature, and ionic strength. Substrate specificity studies showed a high promiscuity in the recognition of purine analogues. Finally, the enzymatic production of different purine derivatives was performed to evaluate the efficiency of multi-enzymatic system LdNDT/TtHGXPRT. Conclusions: The production of different therapeutic purine nucleosides was efficiently catalyzed by LdNDT/TtHGXPRT. In addition, the resulting by-products were converted to IMP and GMP. Taking all of these features, this bioprocess entails an efficient, sustainable, and economical alternative to chemical synthetic methods.

Eu(iii) and Cm(iii) tetracarbonates - in the quest for the limiting species in solution.

The structural and spectroscopic properties of the compounds [C(NH2)3]5[Gd:M(CO3)4(H2O)]·0.75H2O (1) and [C(NH2)3]5[Y:M(CO3)4]·2H2O (2) (M = Eu, Cm) were determined. The crystals contain differently hydrated tetracarbonate complexes, [M(CO3)4(H2O)]5- and [M(CO3)4]5-, which were used as structural and spectroscopic models of Eu(iii) and Cm(iii) tetracarbonate species in aqueous solutions. The luminescence spectra of the crystals were used to establish the stoichiometry and stability of the limiting species of the aqueous Eu(iii) and Cm(iii) carbonate systems at different temperatures and in a broad range of ionic strengths. By implementing this method together with the Pitzer approach used for the description of highly concentrated systems, it was possible to determine the thermodynamic functions of the reaction [Eu(CO3)3]3- + CO32- ⇆ [Eu(CO3)4]5- under standard conditions for the first time (ΔH° = 31.4 ± 2 kJ mol-1 and ΔS° = 82 ± 10 J mol-1 K-1). The proposed model for Eu(iii) carbonates is consistent with the data recorded for the Cm(iii)-carbonate systems. The presented results are important not only from the point of view of environmental issues, but also for the coordination chemistry of f-elements in general.

Modeling solubility and acid-base properties of some polar side chain amino acids in NaCl and (CH3)4NCl aqueous solutions at different ionic strengths and temperatures

The aim of the paper is to perform a critical analysis of the thermodynamic properties of five L-α-amino acids, namely arginine, aspartic acid, glutamic acid, glutamine and histidine. New potentiometric measurements to determine protonation constants and solubility (not for arginine) in NaCl and (CH3)4NCl aqueous solutions are reported, in order to investigate the medium effect. A preliminary analysis of the state of art evidenced the considerable amount of data in the ionic strength range 0 < I/mol kg−1 ≤ 0.1 and a lack of data (especially for arginine and glutamine) above 0.1 mol kg−1. For this reason, this paper deals with an analysis of both the literature and the new experimental data, assigning a weight to each datum as a function of its reliability. The ionic strength dependence of the protonation constants was interpreted using the EDH (Extended Debye-Hückel), the SIT (Specific ion Interaction Theory) and the Pitzer approaches. Simultaneous analysis of solubility data and protonation constants allowed us to obtain the Setschenow and the activity coefficients of all the species involved in the equilibria. The differences between the two media were also interpreted considering the formation of weak complexes between the ions of the supporting electrolytes and the ligands according to the complex formation model.Finally, recommended, tentative or provisional data for protonation constants and protonation enthalpy changes of the five amino acids at different temperatures and ionic strengths are provided.

Enzymatic Production of Non‐Natural Nucleoside‐5′‐Monophosphates by a Thermostable Uracil Phosphoribosyltransferase

AbstractThe use of enzymes as biocatalysts applied to synthesis of modified nucleoside‐5′‐monophosphates (NMPs) is an interesting alternative to traditional multistep chemical methods which offers several advantages, such as stereo‐, regio‐, and enantioselectivity, simple downstream processing, and mild reaction conditions. Herein we report the recombinant expression, production, and purification of uracil phosphoribosyltransferase from Thermus themophilus HB8 (TtUPRT). The structure of TtUPRT has been determined by protein crystallography, and its substrate specificity and biochemical characteristics have been analyzed, providing new structural insights into the substrate‐binding mode. Biochemical characterization of the recombinant protein indicates that the enzyme is a homotetramer, with activity and stability across a broad range of temperatures (50–80 °C), pH (5.5–9) and ionic strength (0–500 mm NaCl). Surprisingly, TtUPRT is able to recognize several 5 and 6‐substituted pyrimidines as substrates. These experimental results suggest TtUPRT could be a valuable biocatalyst for the synthesis of modified NMPs.

Solubility equilibria in the uric acid–ammonium urate–water system

Solubility constants reported in the literature for ammonium hydrogenurate (NH4HU), an occasional constituent of urinary calculi in humans, show a large scatter, probably due to the tendency of hydrogenurates to form supersaturated solutions that persist over long periods of time. In this study, the solubility of NH4HU(s) was measured as a function of p[H] = − lg{[H+]/mol dm−3} (4.5–8) and temperature (25 and 37 °C) at constant ionic strength, I c = 0.300 mol dm−3 NH4Cl, which is similar to the ionic strength of urine. Highly reproducible values for the solubility product (K s0) of NH4HU(s) were obtained. The first dissociation constant (K 1) of uric acid determined in this work agrees well with values obtained in our previous studies of uric acid solubilities in electrolyte solutions relevant to urolithiasis. This study confirms our earlier findings that in the ionic strength range of urine, the solubilities of uric acid and hydrogen urates as a function of p[H] can be described consistently by unique values of their solubility constants (K s, K s0) and the first dissociation constant of uric acid (K 1). In addition, no appreciable complexation between uric acid or hydrogenurates and other urine constituents has been found.

Long-Term Experimental Determination of Solubilities of Micro-Crystalline Nd(III) Hydroxide in High Ionic Strength Solutions: Applications to Nuclear Waste Management

In this study, the experimental results from long-term solubility experiments up to 1146 days on micro-crystalline neodymium hydroxide, Nd(OH)3(micro-cr), in high ionic strength solutions at 298.15 K under well-constrained conditions, are presented. Hydrogen ion concentrations in our experiments are controlled by the dissolution of Nd(OH)3(micro-cr) without artificial adjustment with addition of either an acid or a base, preventing the possibility of phase change that could be induced especially by addition of a base. Such an experimental design also provides the information about the hydrogen ion concentrations buffered by the dissolution of Nd(OH)3, which is currently lacking. The solubility data produced in this work, applicable to geological repositories in high ionic strength environments, are compared with the solubilities of Am(OH)3(s) predicted by using the Waste Isolation Pilot Plant (WIPP) thermodynamic model. The predicted values for Am(OH)3(s) are in good agreement with the experimental values for Nd(OH)3(micro-cr) obtained in this work. Our experimental data indicate that the pHm (negative logarithm of hydrogen ion concentration on a molal scale) buffered by dissolution of Nd(OH)3(micro-cr) ranges from ~ 9.5 to ~ 9.9. As the equilibrium constant for amorphous neodymium hydroxide, Nd(OH)3(am), is useful for several fields, the equilibrium constant regarding the dissolution of Nd(OH)3(am) for the following reaction, $$ {\text{Nd}}\left( {\text{OH}} \right)_{3} \left( {\text{am}} \right) + 3{\text{H}}^{ + } = {\text{Nd}}^{3 + } + 3{\text{H}}_{2} {\text{O}}\left( {\text{l}} \right) $$ is also obtained by evaluating the experimental data in a wide range of ionic strengths from the literature by using the WIPP thermodynamic model. The $$ \log_{10} K_{{{\text{s}}0}}^{0} $$ at 298.15 K for the above reaction obtained in this work is 16.85 ± 0.20 (2σ), which is similar to, but slightly lower than, the values in the literature evaluated in the low ionic strength range. This value can be applied to amorphous americium hydroxide, Am(OH)3(am), using Nd(III) as an analog to Am(III).

A critical approach to the toxic metal ion removal by hazelnut and almond shells

The adsorption capacity of ground hazelnut (HS) and almond (AS) shells towards Pb(II) and Cd(II) has been studied at pH = 5, in NaNO3 and NaCl ionic media, in the ionic strength range 0.05-0.5molL-1. Kinetic and equilibrium experiments were carried out by using the Differential Pulse Anodic Stripping Voltammetry technique to check the amount of the metal ion removed by HS and AS materials. Different kinetic and equilibrium equations were used to fit experimental data and a statistical study was done to establish the suitable model for the data fitting. A speciation study of the metal ions in solution was also done in order to evaluate the influence of the ionic medium on the adsorption process. TGA-DSC, FT-IR, and SEM-EDX techniques were used to characterize the adsorbent materials. The mechanism of metal ions adsorption was explained on the basis of the results obtained by the metal ions speciation study and the characterization of materials.

Different transport behaviors of Bacillus subtilis cells and spores in saturated porous media: Implications for contamination risks associated with bacterial sporulation in aquifer

In this study, we compared the transport characteristics of Bacillus subtilis cells and their spores in saturated porous media. Both the bacteria cells and spores were readily transported under lower ionic strengths (IS) (1mM), featuring high mass recovery rates (>75%). The bacteria cells recovery rate declined to 58.05% when the IS increased to 100mM; but the spores recovery rate remained at 74.54%. Spores appear to be more mobile than bacterial cells over wide range of IS. Surface properties and breakthrough curves analysis of the two bio-particles (cells and spores) indicated that attachment, straining and blocking mechanisms contribute differently to deposition processes. The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory further indicated that the particles attachment may primarily occurred at the secondary energy minimum. More important, XDLVO calculations showed that the dominant forces changed with IS, altering the efficiency of particles attachment. The electric double layer repulsion mainly controlled particle deposition at 1mM. In contrast, the van der Waals attraction and Lewis acid-base interactions dominated particle deposition at 100mM. This study showed that spores are more mobile than bacteria cells in subsurface environment. Given that spores form under harsh environmental conditions, we must consider spore formation and transport when groundwater microbial contamination occurs.

Development and application of the diffusive gradients in thin films technique for simultaneous measurement of methcathinone and ephedrine in surface river water

In this study, a passive sampling technique, diffusive gradients in thin films (DGT) was developed to simultaneously measure two drugs, methcathinone (MC) and ephedrine (EPH) in surface water. Four types of binding gels and four types of filter membranes were tested for the optimal configuration. XAD18 agarose binding gel and agarose diffusive gel, together with polyethersulfone filter membrane were used for measuring MC and EPH in the DGT device. 5% NH3 in acetonitrile was used as the elution solvent, with the elution efficiency for MC and EPH higher than 71%. At 25°C, the diffusion coefficients of MC and EPH in the diffusive gel were 7.60×10−6cm2s−1 and 6.62×10−6cm2s−1, respectively. The DGT was effective in a wide range of pH (4–11) and ionic strength (NaCl: 0.001–0.5M). The DGT device was deployed in Beijing urban surface water for successive 7days to measure the time-weighted concentrations of MC and EPH. Results showed that EPH was detected in all samples, while MC was below its detection limit. DGT concentrations were comparable to the concentrations determined by SPE. This study demonstrated that the developed DGT method was effective to monitor the two drugs in surface water in situ.

Pickering emulsions stabilized by media-milled starch particles

A simple, organic solvent-free media-milling process was applied to modify the structure and morphology of maize starch granules. During the milling process, the sizes of starch granules reduced dramatically while their crystalline structure was largely damaged as verified by differential scanning calorimetry and X-ray diffraction. The surface hydrophobicity of milled starch was also characterized by contact angle measurement. These media-milled starch suspensions with different starch concentrations (i.e., 2.4%, 7.2% and 10.0%) were used as stabilizers to form Pickering emulsions. The droplet sizes of the Pickering emulsions prepared in this study ranged from approximately 10μm to 900μm depending on the milling time and the initial starch concentration. The droplet sizes decreased with prolonged milling time and increased initial starch concentration. Milled starch particles of around 100nm anchored at the emulsion interfaces were observed by cryo-scanning electron microscopy. Although some emulsions creamed immediately after homogenization, most emulsions exhibited stability against coalescence during the long-term storage of 6months. The emulsions also exhibited benign stability against a wide range of pH, ionic strength and temperature conditions. This research provides a new green approach to form food-grade emulsions to deliver active food ingredients.

Synthesis and ion-exchange studies of resins derived from 2,2′-dihydroxybiphenyl-diamine-formaldehyde

Terpolymeric resins (2,2′-DHBPBDF) (DHBP = dihydroxybiphenyl; BD = butylenediamine; F = formaldehyde) were synthesized by the condensation of 2,2′-DHBP, 1,4-BD and formaldehyde in the presence of an acid catalyst with varied molar ratios of reacting monomers. Resin composition was determined on the basis of its elemental analyses. Their number-average molecular weight was determined by conductometric titration in non-aqueous media. The viscosity measurements were carried out in N,N-dimethylformamide at room temperature. Ultraviolet–visible, infrared and proton nuclear magnetic resonance spectral studies were undertaken to elucidate the structure of these resins. The thermal stability and kinetics of the thermal decomposition of these newly synthesized resins have been evaluated on the basis of thermogravimetric analysis and differential thermal analysis. The ion-exchange properties of these resins were studied for different metal ions. A batch equilibrium method was employed to study the selectivity of metal ion uptake. The study was carried out over a wide range of pH and ionic strengths of different electrolytes.

Measuring Nanoparticle Attachment Efficiency in Complex Systems.

As process-based environmental fate and transport models for engineered nanoparticles are developed, there is a need for relevant and reliable measures of nanoparticle behavior. The affinity of nanoparticles for various surfaces (α) is one such measure. Measurements of the affinity of nanoparticles obtained by flowing particles through a porous medium are constrained by the types of materials or exposure scenarios that can be configured into such column studies. Utilizing glass beads and kaolinite as model collector surfaces, we evaluate a previously developed mixing method for measuring nanoparticle attachment to environmental surfaces, and validate this method with an equivalent static column system over a range of organic matter concentrations and ionic strengths. We found that, while both impacted heteroaggregation rates in a predictable manner when varied individually, neither dominated when both parameters were varied. The theory behind observed nanoparticle heteroaggregation rates (αβB) to background particles in mixed systems is also experimentally validated, demonstrating both collision frequency (β) and background particle concentration (B) to be independent for use in fate modeling. We further examined the effects of collector particle composition (kaolinite vs glass beads) and nanoparticle surface chemistry (PVP, citrate, or humic acid) on α, and found a strong dependence on both.

Catanionic Coacervate Droplets as a Surfactant-Based Membrane-Free Protocell Model.

We report on the formation of surfactant-based complex catanionic coacervate droplets in mixtures of decanoic acid and cetylpyridinium chloride or cetyltrimethylammonium bromide. We show that coacervation occurs over a broad range of composition, pH, and ionic strength. The catanionic coacervates consist of elongated micelles, sequester a wide range of solutes including water-soluble organic dyes, polysaccharides, proteins, enzymes, and DNA, and can be structurally stabilized by sodium alginate or gelatin-based hydrogelation. These results suggest that catanionic coacervates could be exploited as a novel surfactant-based membrane-free protocell model.

Catanionic Coacervate Droplets as a Surfactant‐Based Membrane‐Free Protocell Model

AbstractWe report on the formation of surfactant‐based complex catanionic coacervate droplets in mixtures of decanoic acid and cetylpyridinium chloride or cetyltrimethylammonium bromide. We show that coacervation occurs over a broad range of composition, pH, and ionic strength. The catanionic coacervates consist of elongated micelles, sequester a wide range of solutes including water‐soluble organic dyes, polysaccharides, proteins, enzymes, and DNA, and can be structurally stabilized by sodium alginate or gelatin‐based hydrogelation. These results suggest that catanionic coacervates could be exploited as a novel surfactant‐based membrane‐free protocell model.

Ethyl Cellulose Nanoparticles at the Alkane-Water Interface and the Making of Pickering Emulsions.

Pickering emulsions stabilized by nanoparticles have recently received great attention for their remarkable stability, in part a consequence of irreversible adsorption. In this study, we generate Pickering oil-in-water emulsions stabilized by ethyl cellulose (EC) nanoparticles without the addition of surfactants. Over a range of ionic strength and EC nanoparticle concentrations, a series of dynamic interfacial tension (IFT) measurements complemented by extended DLVO theoretical computations are conducted to quantitatively describe the behavior of EC nanoparticles at the interface of water with different alkanes. Regardless of ionic strength, there is no barrier against the adsorption of EC nanoparticles at the alkane-water interfaces studied and the particles tightly cover these interfaces with near maximal coverage (i.e., 91%). Remarkably, the rate of approach to maximum coverage of the alkane-water interface by EC nanoparticles during the later stages of adsorption is accelerated in the presence of salt at concentrations below the critical coagulation concentration (CCC), unlike the air-water interface. Above the CCC, alkane-water interfaces behave similar to air-water interfaces, showing decay in the adsorption flux which is attributed to an increase in surface blocking originating from the attachment of nanoparticles to nanoparticles already adsorbed at the interface. These findings shed light on particle-particle and particle-interface colloidal interactions at and near fluid-fluid interfaces, thereby improving our ability to use hydrophobic EC nanoparticles as emulsion stabilizers.

A modified DGT technique for the simultaneous measurement of dissolved inorganic nitrogen and phosphorus in freshwaters

A modified diffusive gradients in thin films (DGT) technique uses both a mixed binding layer (PrCH and A520E resins for NH4-N and NO3-N, respectively) and multiple binding layers (Metsorb binding layer for PO4-P overlying the mixed binding layer) for the simultaneous measurement of dissolved inorganic nitrogen (nitrate and ammonium) and phosphate in freshwater (INP-DGT). High uptake and elution efficiencies were determined for a mixed (PrCH/A520E) binding gel for dissolved inorganic nitrogen and an agarose-based Metsorb binding layer for PO4-P. Diffusion coefficients (D) obtained from DGT time-series experiments (conductivity 180 μS cm−1) for NH4-N, NO3-N and PO4-P agreed well with those measured using individual DGT techniques in previous studies, but were characterised over a wider range of ionic strengths here. D for NO3-N and PO4-P were constant over a range of ionic strengths (between 100 and 800 μS cm−1) while the diffusion coefficient for NH4-N decreased with increasing ionic strength, as reported previously. The measurement of NH4-N, NO3-N and PO4-P using the INP-DGT was independent of pH (3.5–8.5) and quantitative over varying ionic strength ranges (up to 0.004 mol L−1 NaCl for NH4-N, up to 0.014 mol L−1 NaCl for NO3-N and over 0.1 mol L−1 NaCl for PO4-P) for a 24 h deployment time. Performance of INP-DGT in synthetic freshwaters with differing conductivity indicated the three nutrients were affected differently, with NH4-N measurements being most sensitive. Representative performance was determined for NO3-N (90–330 μS cm−1) and PO4-P (all tested conductivities) over a 72 h deployment period and for NH4-N (<330 μS cm−1) over a 24 h deployment period. Field validations showed that the ratios of INP-DGT concentrations to the average concentrations from grab samples were generally between 0.80 and 1.13 over 24 and 48 h deployment periods. To ensure the representative performance of INP-DGT for all three nutrients, the conductivity should not exceed 400 μS cm−1 and deployment times should be no longer than 24 h. The results of this study have demonstrated that INP-DGT could provide a cost-effective monitoring technique for measuring time-weighted average concentrations of dissolved inorganic nutrients in many freshwaters.

Co4N Nanowires: Noble-Metal-Free Peroxidase Mimetic with Excellent Salt- and Temperature-Resistant Abilities.

Compared to natural enzymes, nanomaterial-based artificial enzymes have attracted immense attention because of their high stability and cost-effectiveness. In this study, cobalt nitride (Co4N) as a noble-metal-free artificial enzyme exhibiting highly intrinsic peroxidase-like activity and good stability was reported. Kinetic studies revealed that the resultant Co4N nanowires (NWs) exhibited a stronger affinity for 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 than HRP. Compared to Co3O4 NWs, Co4N NWs exhibited highly improved catalytic activities, with H2O2 exhibiting an apparent Km approximately 2 orders of magnitude less than that of Co3O4. In particular, the peroxidase-like activity of Co4N was maintained well over a wide range of temperatures and ionic strength. A Co4N-based method was further developed for the detection of glucose with good sensitivity and reliability. Because of advantages such as easy storage, cost-effectiveness, high sensitivity, and outstanding stability, Co4N NWs demonstrate the potential for replacing noble-metal-based peroxidase mimetics in a wide range of promising applications.

Pineapple peel bromelain extraction using gemini surfactant-based reverse micelle – Role of spacer of gemini surfactant

Abstract In this study, the reverse micelles from gemini surfactants pentamethylene-α,ω-bis(dodecyldimethylammonium bromide), dodecamethylene-α,ω-bis(dodecyldimethylammonium bromide), pentamethylene-α,ω-bis(cetyl-dimethylammonium bromide) and octamethylene-α,ω-bis(cetyldimethylammonium bromide) were used to extract bromelain from pineapple peel. The extraction parameters including pH, ionic strength and surfactant content were studied. It was found that the reverse micelle from dodecamethylene-α,ω-bis (dodecyldimethylammonium bromide) could extract more active bromelain in a much wider range of pH, surfactant content and ionic strength than the reverse micelles from the other gemini surfactants, and the optimum activity recovery, purification fold and protein extraction efficiency with dodecamethylene-α,ω-bis (dodecyldimethylammonium bromide) were 160 %, 2.7 and 59 %, respectively. Pineapple peel accounts for the largest waste proportion of pineapple. This study investigated the effect of gemini surfactant structure on extraction efficiency of bromelain from pineapple peel by reverse micelle extraction, and hence, should be helpful for understanding the potency of gemini surfactant in protein extraction.