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Sandro Keller - One of the best experts on this subject based on the ideXlab platform.
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influence of mg2 and ca2 on nanodisc formation by diisobutylene Maleic Acid dibma copolymer
Chemistry and Physics of Lipids, 2019Co-Authors: Bartholomaus Danielczak, Annette Meister, Sandro KellerAbstract:Most membrane-solubilising amphiphilic copolymers such as diisobutylene/Maleic Acid (DIBMA) and styrene/Maleic Acid (SMA) carry high negative charge densities. Their polyanionic character results in strong Coulombic repulsion, both between polymer chains and lipid membranes during the solubilisation process as well as among polymer-encapsulated nanodiscs after solubilisation. Coulombic repulsion is attenuated by charge screening and, more efficiently, by counterion association, which is particularly strong for multivalent cations binding to polyanionic copolymers. Here, we investigated the effects of the two common alkaline earth metal ions Mg2+ and Ca2+ on the solubilisation properties of and the nanodiscs formed by DIBMA. By quantifying the kinetics and the equilibrium efficiency of lipid solubilisation by static and dynamic light scattering, respectively, we found that millimolar concentrations of Mg2+ or Ca2+ accelerated DIBMA-mediated lipid solubilisation several-fold and resulted in considerably smaller nanodiscs than without divalent cations. Time-resolved Forster resonance energy transfer spectroscopy revealed that collisional transfer of phospholipids among nanodiscs was up to ∼20 and ∼25 times faster in the presence of 10 mM Mg2+ or 7.5 mM Ca2+ than in the absence of divalent cations. These major effects of Mg2+ and Ca2+ contrasted with a moderate influence on the morphology and the thermotropic phase behaviour of the nanodiscs. Finally, we compared the yields of membrane-protein extraction from Escherichia coli membranes, which increased by up to two-fold upon addition of Mg2+ or Ca2+. None of these effects could be explained by Coulombic screening alone, as the change in ionic strength resulting from low millimolar concentrations of divalent cations was minor. Thus, we conclude that Mg2+ and Ca2+ specifically associated with DIBMA to neutralise part of the polymer's carboxylate groups.
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formation of lipid bilayer nanodiscs by diisobutylene Maleic Acid dibma copolymer
Langmuir, 2017Co-Authors: Abraham Olusegun Oluwole, Bartholomaus Danielczak, Carolyn Vargas, Johannes Klingler, Jonathan O Babalola, Georg Pabst, Sandro KellerAbstract:Membrane proteins usually need to be extracted from their native environment and separated from other membrane components for in-depth in vitro characterization. The use of styrene/Maleic Acid (SMA) copolymers to solubilize membrane proteins and their surrounding lipids into bilayer nanodiscs is an attractive approach toward this goal. We have recently shown that a diisobutylene/Maleic Acid (DIBMA) copolymer similarly solubilizes model and cellular membranes but, unlike SMA(3:1), has a mild impact on lipid acyl-chain order and thermotropic phase behavior. Here, we used fluorescence spectroscopy, small-angle X-ray scattering, size-exclusion chromatography, dynamic light scattering, and 31P nuclear magnetic resonance spectroscopy to examine the self-association of DIBMA and its membrane-solubilization properties against lipids differing in acyl-chain length and saturation. Although DIBMA is less hydrophobic than commonly used SMA(3:1) and SMA(2:1) copolymers, it efficiently formed lipid-bilayer nanodiscs th...
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thermodynamics of nanodisc formation mediated by styrene Maleic Acid 2 1 copolymer
Scientific Reports, 2017Co-Authors: Anne Grethen, Abraham Olusegun Oluwole, Bartholomaus Danielczak, Carolyn Vargas, Sandro KellerAbstract:Styrene/Maleic Acid copolymers (SMA) have recently attracted great interest for in vitro studies of membrane proteins, as they self-insert into and fragment biological membranes to form polymer-bounded nanodiscs that provide a native-like lipid-bilayer environment. SMA copolymers are available in different styrene/Maleic Acid ratios and chain lengths and, thus, possess different charge densities, hydrophobicities, and solubilisation properties. Here, we studied the equilibrium solubilisation properties of the most commonly used copolymer, SMA(2:1), by monitoring the formation of nanodiscs from phospholipid vesicles using 31P nuclear magnetic resonance spectroscopy, dynamic light scattering, and differential scanning calorimetry. Comparison of SMA(2:1) phase diagrams with those of SMA(3:1) and diisobutylene/Maleic Acid (DIBMA) revealed that, on a mass concentration scale, SMA(2:1) is the most efficient membrane solubiliser, despite its relatively mild effects on the thermotropic phase behaviour of solubilised lipids. In contrast with previous kinetic studies, our equilibrium experiments demonstrate that the solubilisation of phospholipid bilayers by SMA(2:1) is most efficient at moderately alkaline pH values. This pH dependence was also observed for the solubilisation of native Escherichia coli membranes, for which SMA(2:1) again turned out to be the most powerful solubiliser in terms of the total amounts of membrane proteins extracted.
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solubilization of membrane proteins into functional lipid bilayer nanodiscs using a diisobutylene Maleic Acid copolymer
Angewandte Chemie, 2017Co-Authors: Abraham Olusegun Oluwole, Bartholomaus Danielczak, Carolyn Vargas, Jonathan O Babalola, Annette Meister, Sandro KellerAbstract:: Once removed from their natural environment, membrane proteins depend on membrane-mimetic systems to retain their native structures and functions. To this end, lipid-bilayer nanodiscs that are bounded by scaffold proteins or amphiphilic polymers such as styrene/Maleic Acid (SMA) copolymers have been introduced as alternatives to detergent micelles and liposomes for in vitro membrane-protein research. Herein, we show that an alternating diisobutylene/Maleic Acid (DIBMA) copolymer shows equal performance to SMA in solubilizing phospholipids, stabilizes an integral membrane enzyme in functional bilayer nanodiscs, and extracts proteins of various sizes directly from cellular membranes. Unlike aromatic SMA, aliphatic DIBMA has only a mild effect on lipid acyl-chain order, does not interfere with optical spectroscopy in the far-UV range, and does not precipitate in the presence of low millimolar concentrations of divalent cations.
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influence of lipid bilayer properties on nanodisc formation mediated by styrene Maleic Acid copolymers
Nanoscale, 2016Co-Authors: Rodrigo Cuevas Arenas, Carolyn Vargas, Johannes Klingler, Sandro KellerAbstract:Copolymers of styrene and Maleic Acid (SMA) have gained great attention as alternatives to conventional detergents, as they offer decisive advantages for studying membrane proteins and lipids in vitro. These polymers self-insert into artificial and biological membranes and, at sufficiently high concentrations, solubilise them into disc-shaped nanostructures containing a lipid bilayer core surrounded by a polymer belt. We have used 31P nuclear magnetic resonance spectroscopy and dynamic light scattering to systematically study the solubilisation of vesicles composed of saturated or unsaturated phospholipids by an SMA copolymer with a 3 : 1 styrene/Maleic Acid molar ratio at different temperatures. Solubilisation was thermodynamically rationalised in terms of a three-stage model that treats various lipid/polymer aggregates as pseudophases. The solubilising capacity of SMA(3 : 1) towards a saturated lipid is higher in the gel than in the liquid–crystalline state of the membrane even though solubilisation is slower. Although the solubilisation of mixed fluid membranes is non-selective, the presence of a non-bilayer phospholipid lowers the threshold at which the membrane becomes saturated with SMA(3 : 1) but raises the polymer concentration required for complete solubilisation. Both of these trends can be explained by considering the vesicle-to-nanodisc transfer free energies of the lipid and the polymer. On the basis of the phase diagrams thus obtained, re-association of polymer-solubilised lipids with vesicles is possible under mild conditions, which has implications for the reconstitution of proteins and lipids from nanodiscs into vesicular membranes. Finally, the phase diagrams provide evidence for the absence of free SMA(3 : 1) in vesicular lipid suspensions.
Abraham Olusegun Oluwole - One of the best experts on this subject based on the ideXlab platform.
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formation of lipid bilayer nanodiscs by diisobutylene Maleic Acid dibma copolymer
Langmuir, 2017Co-Authors: Abraham Olusegun Oluwole, Bartholomaus Danielczak, Carolyn Vargas, Johannes Klingler, Jonathan O Babalola, Georg Pabst, Sandro KellerAbstract:Membrane proteins usually need to be extracted from their native environment and separated from other membrane components for in-depth in vitro characterization. The use of styrene/Maleic Acid (SMA) copolymers to solubilize membrane proteins and their surrounding lipids into bilayer nanodiscs is an attractive approach toward this goal. We have recently shown that a diisobutylene/Maleic Acid (DIBMA) copolymer similarly solubilizes model and cellular membranes but, unlike SMA(3:1), has a mild impact on lipid acyl-chain order and thermotropic phase behavior. Here, we used fluorescence spectroscopy, small-angle X-ray scattering, size-exclusion chromatography, dynamic light scattering, and 31P nuclear magnetic resonance spectroscopy to examine the self-association of DIBMA and its membrane-solubilization properties against lipids differing in acyl-chain length and saturation. Although DIBMA is less hydrophobic than commonly used SMA(3:1) and SMA(2:1) copolymers, it efficiently formed lipid-bilayer nanodiscs th...
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thermodynamics of nanodisc formation mediated by styrene Maleic Acid 2 1 copolymer
Scientific Reports, 2017Co-Authors: Anne Grethen, Abraham Olusegun Oluwole, Bartholomaus Danielczak, Carolyn Vargas, Sandro KellerAbstract:Styrene/Maleic Acid copolymers (SMA) have recently attracted great interest for in vitro studies of membrane proteins, as they self-insert into and fragment biological membranes to form polymer-bounded nanodiscs that provide a native-like lipid-bilayer environment. SMA copolymers are available in different styrene/Maleic Acid ratios and chain lengths and, thus, possess different charge densities, hydrophobicities, and solubilisation properties. Here, we studied the equilibrium solubilisation properties of the most commonly used copolymer, SMA(2:1), by monitoring the formation of nanodiscs from phospholipid vesicles using 31P nuclear magnetic resonance spectroscopy, dynamic light scattering, and differential scanning calorimetry. Comparison of SMA(2:1) phase diagrams with those of SMA(3:1) and diisobutylene/Maleic Acid (DIBMA) revealed that, on a mass concentration scale, SMA(2:1) is the most efficient membrane solubiliser, despite its relatively mild effects on the thermotropic phase behaviour of solubilised lipids. In contrast with previous kinetic studies, our equilibrium experiments demonstrate that the solubilisation of phospholipid bilayers by SMA(2:1) is most efficient at moderately alkaline pH values. This pH dependence was also observed for the solubilisation of native Escherichia coli membranes, for which SMA(2:1) again turned out to be the most powerful solubiliser in terms of the total amounts of membrane proteins extracted.
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solubilization of membrane proteins into functional lipid bilayer nanodiscs using a diisobutylene Maleic Acid copolymer
Angewandte Chemie, 2017Co-Authors: Abraham Olusegun Oluwole, Bartholomaus Danielczak, Carolyn Vargas, Jonathan O Babalola, Annette Meister, Sandro KellerAbstract:: Once removed from their natural environment, membrane proteins depend on membrane-mimetic systems to retain their native structures and functions. To this end, lipid-bilayer nanodiscs that are bounded by scaffold proteins or amphiphilic polymers such as styrene/Maleic Acid (SMA) copolymers have been introduced as alternatives to detergent micelles and liposomes for in vitro membrane-protein research. Herein, we show that an alternating diisobutylene/Maleic Acid (DIBMA) copolymer shows equal performance to SMA in solubilizing phospholipids, stabilizes an integral membrane enzyme in functional bilayer nanodiscs, and extracts proteins of various sizes directly from cellular membranes. Unlike aromatic SMA, aliphatic DIBMA has only a mild effect on lipid acyl-chain order, does not interfere with optical spectroscopy in the far-UV range, and does not precipitate in the presence of low millimolar concentrations of divalent cations.
Michael R. Jones - One of the best experts on this subject based on the ideXlab platform.
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the effectiveness of styrene Maleic Acid sma copolymers for solubilisation of integral membrane proteins from sma accessible and sma resistant membranes
Biochimica et Biophysica Acta, 2017Co-Authors: David J K Swainsbury, Nicholas Foster, Rienk Van Grondelle, S Scheidelaar, Antoinette J Killian, Michael R. JonesAbstract:Abstract Solubilisation of biological lipid bilayer membranes for analysis of their protein complement has traditionally been carried out using detergents, but there is increasing interest in the use of amphiphilic copolymers such as styrene Maleic Acid (SMA) for the solubilisation, purification and characterisation of integral membrane proteins in the form of protein/lipid nanodiscs. Here we survey the effectiveness of various commercially-available formulations of the SMA copolymer in solubilising Rhodobacter sphaeroides reaction centres (RCs) from photosynthetic membranes. We find that formulations of SMA with a 2:1 or 3:1 ratio of styrene to Maleic Acid are almost as effective as detergent in solubilising RCs, with the best solubilisation by short chain variants (
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The effectiveness of styrene-Maleic Acid (SMA) copolymers for solubilisation of integral membrane proteins from SMA-accessible and SMA-resistant membranes
Biochimica et Biophysica Acta - Biomembranes, 2017Co-Authors: David J K Swainsbury, Nicholas Foster, Rienk Van Grondelle, S Scheidelaar, J. Antoinette Killian, Michael R. JonesAbstract:Solubilisation of biological lipid bilayer membranes for analysis of their protein complement has traditionally been carried out using detergents, but there is increasing interest in the use of amphiphilic copolymers such as styrene Maleic Acid (SMA) for the solubilisation, purification and characterisation of integral membrane proteins in the form of protein/lipid nanodiscs. Here we survey the effectiveness of various commercially-available formulations of the SMA copolymer in solubilising Rhodobacter sphaeroides reaction centres (RCs) from photosynthetic membranes. We find that formulations of SMA with a 2:1 or 3:1 ratio of styrene to Maleic Acid are almost as effective as detergent in solubilising RCs, with the best solubilisation by short chain variants (< 30 kDa weight average molecular weight). The effectiveness of 10 kDa 2:1 and 3:1 formulations of SMA to solubilise RCs gradually declined when genetically-encoded coiled-coil bundles were used to artificially tether normally monomeric RCs into dimeric, trimeric and tetrameric multimers. The ability of SMA to solubilise reaction centre-light harvesting 1 (RC-LH1) complexes from densely packed and highly ordered photosynthetic membranes was uniformly low, but could be increased through a variety of treatments to increase the lipid:protein ratio. However, proteins isolated from such membranes comprised clusters of complexes in small membrane patches rather than individual proteins. We conclude that short-chain 2:1 and 3:1 formulations of SMA are the most effective in solubilising integral membrane proteins, but that solubilisation efficiencies are strongly influenced by the size of the target protein and the density of packing of proteins in the membrane.
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bacterial reaction centers purified with styrene Maleic Acid copolymer retain native membrane functional properties and display enhanced stability
Angewandte Chemie, 2014Co-Authors: David J K Swainsbury, Rienk Van Grondelle, S Scheidelaar, Antoinette J Killian, Michael R. JonesAbstract:Integral membrane proteins often present daunting challenges for biophysical characterization, a fundamental issue being how to select a surfactant that will optimally preserve the individual structure and functional properties of a given membrane protein. Bacterial reaction centers offer a rare opportunity to compare the properties of an integral membrane protein in different artificial lipid/surfactant environments with those in the native bilayer. Here, we demonstrate that reaction centers purified using a styrene Maleic Acid copolymer remain associated with a complement of native lipids and do not display the modified functional properties that typically result from detergent solubilization. Direct comparisons show that reaction centers are more stable in this copolymer/lipid environment than in a detergent micelle or even in the native membrane, suggesting a promising new route to exploitation of such photovoltaic integral membrane proteins in device applications.
Bartholomaus Danielczak - One of the best experts on this subject based on the ideXlab platform.
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influence of mg2 and ca2 on nanodisc formation by diisobutylene Maleic Acid dibma copolymer
Chemistry and Physics of Lipids, 2019Co-Authors: Bartholomaus Danielczak, Annette Meister, Sandro KellerAbstract:Most membrane-solubilising amphiphilic copolymers such as diisobutylene/Maleic Acid (DIBMA) and styrene/Maleic Acid (SMA) carry high negative charge densities. Their polyanionic character results in strong Coulombic repulsion, both between polymer chains and lipid membranes during the solubilisation process as well as among polymer-encapsulated nanodiscs after solubilisation. Coulombic repulsion is attenuated by charge screening and, more efficiently, by counterion association, which is particularly strong for multivalent cations binding to polyanionic copolymers. Here, we investigated the effects of the two common alkaline earth metal ions Mg2+ and Ca2+ on the solubilisation properties of and the nanodiscs formed by DIBMA. By quantifying the kinetics and the equilibrium efficiency of lipid solubilisation by static and dynamic light scattering, respectively, we found that millimolar concentrations of Mg2+ or Ca2+ accelerated DIBMA-mediated lipid solubilisation several-fold and resulted in considerably smaller nanodiscs than without divalent cations. Time-resolved Forster resonance energy transfer spectroscopy revealed that collisional transfer of phospholipids among nanodiscs was up to ∼20 and ∼25 times faster in the presence of 10 mM Mg2+ or 7.5 mM Ca2+ than in the absence of divalent cations. These major effects of Mg2+ and Ca2+ contrasted with a moderate influence on the morphology and the thermotropic phase behaviour of the nanodiscs. Finally, we compared the yields of membrane-protein extraction from Escherichia coli membranes, which increased by up to two-fold upon addition of Mg2+ or Ca2+. None of these effects could be explained by Coulombic screening alone, as the change in ionic strength resulting from low millimolar concentrations of divalent cations was minor. Thus, we conclude that Mg2+ and Ca2+ specifically associated with DIBMA to neutralise part of the polymer's carboxylate groups.
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formation of lipid bilayer nanodiscs by diisobutylene Maleic Acid dibma copolymer
Langmuir, 2017Co-Authors: Abraham Olusegun Oluwole, Bartholomaus Danielczak, Carolyn Vargas, Johannes Klingler, Jonathan O Babalola, Georg Pabst, Sandro KellerAbstract:Membrane proteins usually need to be extracted from their native environment and separated from other membrane components for in-depth in vitro characterization. The use of styrene/Maleic Acid (SMA) copolymers to solubilize membrane proteins and their surrounding lipids into bilayer nanodiscs is an attractive approach toward this goal. We have recently shown that a diisobutylene/Maleic Acid (DIBMA) copolymer similarly solubilizes model and cellular membranes but, unlike SMA(3:1), has a mild impact on lipid acyl-chain order and thermotropic phase behavior. Here, we used fluorescence spectroscopy, small-angle X-ray scattering, size-exclusion chromatography, dynamic light scattering, and 31P nuclear magnetic resonance spectroscopy to examine the self-association of DIBMA and its membrane-solubilization properties against lipids differing in acyl-chain length and saturation. Although DIBMA is less hydrophobic than commonly used SMA(3:1) and SMA(2:1) copolymers, it efficiently formed lipid-bilayer nanodiscs th...
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thermodynamics of nanodisc formation mediated by styrene Maleic Acid 2 1 copolymer
Scientific Reports, 2017Co-Authors: Anne Grethen, Abraham Olusegun Oluwole, Bartholomaus Danielczak, Carolyn Vargas, Sandro KellerAbstract:Styrene/Maleic Acid copolymers (SMA) have recently attracted great interest for in vitro studies of membrane proteins, as they self-insert into and fragment biological membranes to form polymer-bounded nanodiscs that provide a native-like lipid-bilayer environment. SMA copolymers are available in different styrene/Maleic Acid ratios and chain lengths and, thus, possess different charge densities, hydrophobicities, and solubilisation properties. Here, we studied the equilibrium solubilisation properties of the most commonly used copolymer, SMA(2:1), by monitoring the formation of nanodiscs from phospholipid vesicles using 31P nuclear magnetic resonance spectroscopy, dynamic light scattering, and differential scanning calorimetry. Comparison of SMA(2:1) phase diagrams with those of SMA(3:1) and diisobutylene/Maleic Acid (DIBMA) revealed that, on a mass concentration scale, SMA(2:1) is the most efficient membrane solubiliser, despite its relatively mild effects on the thermotropic phase behaviour of solubilised lipids. In contrast with previous kinetic studies, our equilibrium experiments demonstrate that the solubilisation of phospholipid bilayers by SMA(2:1) is most efficient at moderately alkaline pH values. This pH dependence was also observed for the solubilisation of native Escherichia coli membranes, for which SMA(2:1) again turned out to be the most powerful solubiliser in terms of the total amounts of membrane proteins extracted.
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solubilization of membrane proteins into functional lipid bilayer nanodiscs using a diisobutylene Maleic Acid copolymer
Angewandte Chemie, 2017Co-Authors: Abraham Olusegun Oluwole, Bartholomaus Danielczak, Carolyn Vargas, Jonathan O Babalola, Annette Meister, Sandro KellerAbstract:: Once removed from their natural environment, membrane proteins depend on membrane-mimetic systems to retain their native structures and functions. To this end, lipid-bilayer nanodiscs that are bounded by scaffold proteins or amphiphilic polymers such as styrene/Maleic Acid (SMA) copolymers have been introduced as alternatives to detergent micelles and liposomes for in vitro membrane-protein research. Herein, we show that an alternating diisobutylene/Maleic Acid (DIBMA) copolymer shows equal performance to SMA in solubilizing phospholipids, stabilizes an integral membrane enzyme in functional bilayer nanodiscs, and extracts proteins of various sizes directly from cellular membranes. Unlike aromatic SMA, aliphatic DIBMA has only a mild effect on lipid acyl-chain order, does not interfere with optical spectroscopy in the far-UV range, and does not precipitate in the presence of low millimolar concentrations of divalent cations.
Antoinette J Killian - One of the best experts on this subject based on the ideXlab platform.
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the effectiveness of styrene Maleic Acid sma copolymers for solubilisation of integral membrane proteins from sma accessible and sma resistant membranes
Biochimica et Biophysica Acta, 2017Co-Authors: David J K Swainsbury, Nicholas Foster, Rienk Van Grondelle, S Scheidelaar, Antoinette J Killian, Michael R. JonesAbstract:Abstract Solubilisation of biological lipid bilayer membranes for analysis of their protein complement has traditionally been carried out using detergents, but there is increasing interest in the use of amphiphilic copolymers such as styrene Maleic Acid (SMA) for the solubilisation, purification and characterisation of integral membrane proteins in the form of protein/lipid nanodiscs. Here we survey the effectiveness of various commercially-available formulations of the SMA copolymer in solubilising Rhodobacter sphaeroides reaction centres (RCs) from photosynthetic membranes. We find that formulations of SMA with a 2:1 or 3:1 ratio of styrene to Maleic Acid are almost as effective as detergent in solubilising RCs, with the best solubilisation by short chain variants (
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solubilization of lipids and lipid phases by the styrene Maleic Acid copolymer
European Biophysics Journal, 2017Co-Authors: Juan Dominguez J Pardo, S Scheidelaar, Jonas M Dorr, Martijn C Koorengevel, Aditya Iyer, Ruud C Cox, Vinod Subramaniam, Antoinette J KillianAbstract:A promising tool in membrane research is the use of the styrene-Maleic Acid (SMA) copolymer to solubilize membranes in the form of nanodiscs. Since membranes are heterogeneous in composition, it is important to know whether SMA thereby has a preference for solubilization of either specific types of lipids or specific bilayer phases. Here, we investigated this by performing partial solubilization of model membranes and analyzing the lipid composition of the solubilized fraction. We found that SMA displays no significant lipid preference in homogeneous binary lipid mixtures in the fluid phase, even when using lipids that by themselves show very different solubilization kinetics. By contrast, in heterogeneous phase-separated bilayers, SMA was found to have a strong preference for solubilization of lipids in the fluid phase as compared to those in either a gel phase or a liquid-ordered phase. Together the results suggest that (1) SMA is a reliable tool to characterize native interactions between membrane constituents, (2) any solubilization preference of SMA is not due to properties of individual lipids but rather due to properties of the membrane or membrane domains in which these lipids reside and (3) exploiting SMA resistance rather than detergent resistance may be an attractive approach for the isolation of ordered domains from biological membranes.
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the styrene Maleic Acid copolymer a versatile tool in membrane research
European Biophysics Journal, 2016Co-Authors: Jonas M Dorr, S Scheidelaar, Martijn C Koorengevel, Juan J Dominguez, Marre Schafer, Cornelis A Van Walree, Antoinette J KillianAbstract:A new and promising tool in membrane research is the detergent-free solubilization of membrane proteins by styrene–Maleic Acid copolymers (SMAs). These amphipathic molecules are able to solubilize lipid bilayers in the form of nanodiscs that are bounded by the polymer. Thus, membrane proteins can be directly extracted from cells in a water-soluble form while conserving a patch of native membrane around them. In this review article, we briefly discuss current methods of membrane protein solubilization and stabilization. We then zoom in on SMAs, describe their physico-chemical properties, and discuss their membrane-solubilizing effect. This is followed by an overview of studies in which SMA has been used to isolate and investigate membrane proteins. Finally, potential future applications of the methodology are discussed for structural and functional studies on membrane proteins in a near-native environment and for characterizing protein–lipid and protein–protein interactions.
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bacterial reaction centers purified with styrene Maleic Acid copolymer retain native membrane functional properties and display enhanced stability
Angewandte Chemie, 2014Co-Authors: David J K Swainsbury, Rienk Van Grondelle, S Scheidelaar, Antoinette J Killian, Michael R. JonesAbstract:Integral membrane proteins often present daunting challenges for biophysical characterization, a fundamental issue being how to select a surfactant that will optimally preserve the individual structure and functional properties of a given membrane protein. Bacterial reaction centers offer a rare opportunity to compare the properties of an integral membrane protein in different artificial lipid/surfactant environments with those in the native bilayer. Here, we demonstrate that reaction centers purified using a styrene Maleic Acid copolymer remain associated with a complement of native lipids and do not display the modified functional properties that typically result from detergent solubilization. Direct comparisons show that reaction centers are more stable in this copolymer/lipid environment than in a detergent micelle or even in the native membrane, suggesting a promising new route to exploitation of such photovoltaic integral membrane proteins in device applications.
