The micelle to vesicle transition of lipids and detergents in the presence of a membrane protein: towards a rationale for 2D crystallization

Dolder, Max; Engel, Andréas; Zulauf, M.

doi:10.1016/0014-5793(96)00180-9

Cited by 65 publications

(70 citation statements)

References 21 publications

(29 reference statements)

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“…A slow dialysis technique (45) was used to conduct self-assembly experiments with PAP channels and lipids over a wide range of mCLRs. Like for membrane proteins (46), the concentration of PAP channels in the membrane had a significant effect on the morphology of the resulting PAP channellipid aggregates as observed by negative-stain electron microscopy (EM) (Fig. 4A).…”

Section: Simulationsmentioning

confidence: 90%

Highly permeable artificial water channels that can self-assemble into two-dimensional arrays

Shen

Wen

Erbakan

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

159

246

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Bioinspired artificial water channels aim to combine the high permeability and selectivity of biological aquaporin (AQP) water channels with chemical stability. Here, we carefully characterized a class of artificial water channels, peptide-appended pillar [5]arenes (PAPs). The average single-channel osmotic water permeability for PAPs is 1.0(±0.3) × 10 −14 cm 3 /s or 3.5(±1.0) × 10 8 water molecules per s, which is in the range of AQPs (3.4∼40.3 × 10 8 water molecules per s) and their current synthetic analogs, carbon nanotubes (CNTs, 9.0 × 10 8 water molecules per s). This permeability is an order of magnitude higher than first-generation artificial water channels (20 to ∼10 7 water molecules per s). Furthermore, within lipid bilayers, PAP channels can self-assemble into 2D arrays. Relevant to permeable membrane design, the pore density of PAP channel arrays (∼2.6 × 10 5 pores per μm 2 ) is two orders of magnitude higher than that of CNT membranes (0.1∼2.5 × 10 3 pores per μm 2 ). PAP channels thus combine the advantages of biological channels and CNTs and improve upon them through their relatively simple synthesis, chemical stability, and propensity to form arrays.artificial aquaporins | artificial water channels | peptide-appended pillar [5]arene | single-channel water permeability | two-dimensional arrays T he discovery of the high water and gas permeability of aquaporins (AQPs) and the development of artificial analogs, carbon nanotubes (CNTs), have led to an explosion in studies aimed at incorporating such channels into materials and devices for applications that use their unique transport properties (1-9). Areas of application include liquid and gas separations (10-13), drug delivery and screening (14), DNA recognition (15), and sensors (16). CNTs are promising channels because they conduct water and gas three to four orders of magnitude faster than predicted by conventional Hagen-Poiseuille flow theory (11). However, their use in large-scale applications has been hampered by difficulties in producing CNTs with subnanometer pore diameters and fabricating membranes in which the CNTs are vertically aligned (4). AQPs also efficiently conduct water across membranes (∼3 billion molecules per second) (17) and are therefore being studied intensively for their use in biomimetic membranes for water purification and other applications (1, 2, 18). The largescale applications of AQPs is complicated by the high cost of membrane protein production, their low stability, and challenges in membrane fabrication (1).Artificial water channels, bioinspired analogs of AQPs created using synthetic chemistry (19), ideally have a structure that forms a water-permeable channel in the center and an outer surface that is compatible with a lipid membrane environment (1). Interest in artificial water channels has grown in recent years, following decades of research and focus on synthetic ion channels (19). However, two fundamental questions remain: (i) Can artificial channels approach the permeability and selectivity of AQP water chan...

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Section: Simulationsmentioning

confidence: 90%

Highly permeable artificial water channels that can self-assemble into two-dimensional arrays

Shen

Wen

Erbakan

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

159

246

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“…Unfortunately, the number of AqpZs inserted per vesicle has not been determined in this or other AqpZ studies (5); hence, we cannot offer a definitive conclusion. However, other studies have shown that vesicles with a AqpZ-to-lipid weight ratio of 1:1 can be synthesized by using slow detergent removal methods (32,33). This indicates that higher permeabilities might be possible with other reconstitution methods.…”

Section: Discussionmentioning

confidence: 99%

Highly permeable polymeric membranes based on the incorporation of the functional water channel protein Aquaporin Z

Kumar

Grzelakowski

Zilles

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

657

643

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The permeability and solute transport characteristics of amphiphilic triblock-polymer vesicles containing the bacterial water-channel protein Aquaporin Z (AqpZ) were investigated. The vesicles were made of a block copolymer with symmetric poly-(2-methyloxazoline)-poly-(dimethylsiloxane)-poly-(2-methyloxazoline) (PMOXA 15-PDMS110-PMOXA 15) repeat units. Light-scattering measurements on pure polymer vesicles subject to an outwardly directed salt gradient in a stopped-flow apparatus indicated that the polymer vesicles were highly impermeable. However, a large enhancement in water productivity (permeability per unit driving force) of up to Ϸ800 times that of pure polymer was observed when AqpZ was incorporated. The activation energy (E a) of water transport for the protein-polymer vesicles (3.4 kcal/mol) corresponded to that reported for water-channel-mediated water transport in lipid membranes. The solute reflection coefficients of glucose, glycerol, salt, and urea were also calculated, and indicated that these solutes are completely rejected. The productivity of AqpZ-incorporated polymer membranes was at least an order of magnitude larger than values for existing salt-rejecting polymeric membranes. The approach followed here may lead to more productive and sustainable water treatment membranes, whereas the variable levels of permeability obtained with different concentrations of AqpZ may provide a key property for drug delivery applications.permeability ͉ triblock copolymer ͉ water treatment B iological membranes have excellent water transport characteristics, with certain membranes able to regulate permeability over a wide range. The permeability of membranes such as those present in the proximal tubules of the human kidney (1) can be increased by insertion of specific water-channel membrane proteins known as Aquaporins (AQPs). Other biological membranes, such as those in mammalian optic lenses (2), erythrocytes (3), and many other cell membranes (4) are constitutively AQP-rich. The permeabilities of AQP-rich membranes are orders of magnitude higher than those observed for unmodified phospholipid membranes (5). Additionally, some members of the AQP family have excellent solute retention capabilities for small solutes such as urea, glycerol, and glucose, even at high water transport rates (5, 6). These properties result from the unique structure of the water-selective AQPs. These AQPs have six membrane-spanning domains and a unique hourglass structure (7) with conserved charged residues that form a pore that allows both selective water transport and solute rejection. The AQP used in this study was a bacterial aquaporin from Escherichia coli, Aquaporin Z (AqpZ). AqpZ was selected because it can enhance the permeability of lipid vesicles by an order of magnitude while retaining small uncharged solutes (5). Additionally, AqpZ can be expressed in relatively large quantities in E. coli and has been reported to be quite stable under different reducing conditions and at temperatures of 4°C (5)-properties that make it att...

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“…(1,2,6,(10)(11)(12) Nucleotides and polynucleotides will bind to cationic lipids (13,14) and polynucleotides, polyamines and lipids will all associate to form regular structures with some similarity to bacteriophage. (15,16) Micelle-to-vesicle transitions are promoted by the presence of peptides and proteins (17) and the interactions are component-selective. (18,19) Contrary to intuition, partial incompatibility of molecules enhances selfassembly (20) as does increasing temperature near ambient temperature.…”

Section: Self-assembly and The Origins Of Composomesmentioning

confidence: 99%

Compositional complementarity and prebiotic ecology in the origin of life

Hunding¹,

Képès²,

Lancet³

et al. 2006

BioEssays

100

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We hypothesize that life began not with the first self-reproducing molecule or metabolic network, but as a prebiotic ecology of co-evolving populations of macromolecular aggregates (composomes). Each composome species had a particular molecular composition resulting from molecular complementarity among environmentally available prebiotic compounds. Natural selection acted on composomal species that varied in properties and functions such as stability, catalysis, fission, fusion and selective accumulation of molecules from solution. Fission permitted molecular replication based on composition rather than linear structure, while fusion created composomal variability. Catalytic functions provided additional chemical novelty resulting eventually in autocatalytic and mutually catalytic networks within composomal species. Composomal autocatalysis and interdependence allowed the Darwinian co-evolution of content and control (metabolism). The existence of chemical interfaces within complex composomes created linear templates upon which self-reproducing molecules (such as RNA) could be synthesized, permitting the evolution of informational replication by molecular templating. Mathematical and experimental tests are proposed.

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The micelle to vesicle transition of lipids and detergents in the presence of a membrane protein: towards a rationale for 2D crystallization

Cited by 65 publications

References 21 publications

Highly permeable artificial water channels that can self-assemble into two-dimensional arrays

Highly permeable artificial water channels that can self-assemble into two-dimensional arrays

Highly permeable polymeric membranes based on the incorporation of the functional water channel protein Aquaporin Z

Compositional complementarity and prebiotic ecology in the origin of life

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