Size and shape of globular micelles formed in aqueous solution by n-alkyl polyoxyethylene ethers

Tanford, Charles; Nozaki, Yoshiyuki; Rohde, Michael F.

doi:10.1021/j100531a007

Cited by 277 publications

(178 citation statements)

References 7 publications

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“…Triton X-114 is a polydisperse nonionic detergent, p-(1,1,3,3-tetramethylbutyl)phenoxypolyoxyethylene glycol, containing an average of 7.5 oxyethylene units per molecule. Above its critical micelle concentration at 4°C, it forms micelles each containing about 140 detergent molecules (9) with the p-octylphenyl groups sequestered in a hydrophobic core and the hydrophilic polyoxyethylene glycol residues in a random-coil conformation in the outer shell of the micelle (17 (5). Although the subunits have somewhat different molecular weights, they show striking homologies in their amino acid sequences as deduced from the nucleotide sequences of the corresponding cDNAs (22,23).…”

Section: Discussionmentioning

confidence: 99%

Anomalous interaction of the acetylcholine receptor protein with the nonionic detergent Triton X-114.

Maher¹,

Singer²

1985

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

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AISTRACT Integral membrane proteins that form water-filied channels through membranes often exist as aggregates of similar or identical subunits spanning the membrane.It has been suggested that the insertion into the membrane of the channel-forming domains of the subunits may impart unusual structural features to the membrane-intercalated portions of the protein. To test this proposal, we have investigated the interaction of a multisubunit channel-forming integral membrane protein, the acetylcholine receptor protein, with the nonionic detergent Triton X-114. Whereas non-channelforming integral membrane proteins that have heretofore been studied form mixed micelles with the detergent, the acetylcholine receptor was excluded from the Triton X-114 micelles. The structural implications of this result are discussed.In an early thermodynamic analysis of membrane structure (1), it was predicted that a class of integral membrane proteins exists that form water-filled channels through membranes and that mediate the permeability of membranes to ions and small polar molecules. It was proposed that such a channel-forming protein generally would consist of a specific noncovalently bound aggregate of a small number n of identical or similar subunits spanning the membrane, with the channel running down the n-fold symmetry axis of the aggregate. To allow for thermodynamic stability, it was suggested that the portion of the exterior surface of the aggregate that was intercalated into the lipid bilayer would be mainly hydrophobic, but that the central channel might be lined with some of the ionic and polar amino acid residues of the subunits, in contact with the water in the channel. The purpose of such a structure would be to permit low-energy-requiring quaternary rearrangements (1, 2) of the subunits to occur, which would result in the directed translocation of specific ions and small polar molecules through the channel across the membrane. In further consideration of this model, it was pointed out (3, 4) that the insertion of such a hydrophilic channel through a membrane is not a trivial problem and, furthermore, that certain thermodynamically satisfactory mechanisms for such insertion might necessitate distinctive structural properties for channel-forming proteins, which would not be shared with other types of integral membrane proteins (see Discussion).In the years since these predictions were made, several integral membrane proteins involved in membrane transport and permeability have been characterized in sufficient detail to show that they indeed consist of subunit aggregates forming transmembrane channels down their central axes. Among the best studied of these integral membrane proteins is the acetylcholine receptor (AcChoR) (for a recent review, see ref. To test the proposition that channel-forming proteins might have distinctive structural characteristics not shared by other types of integral membrane proteins, we have studied the partitioning behavior of AcChoR in Triton X-114 phase-separation experiments as describe...

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Section: Discussionmentioning

confidence: 99%

Anomalous interaction of the acetylcholine receptor protein with the nonionic detergent Triton X-114.

Maher¹,

Singer²

1985

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

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“…In the case of classical micelles and microemulsions containing at least one surfactant with a well-defined head group "bound" to the oil-water interface, the volume of micelle and microemulsion droplet is controlled by the area per molecule at the interface (as well as topology) (32)(33)(34). The free energy of micelle formation vs. the area per surfactant molecule (the lateral equation of state) is a function with a deep minimum (35).…”

Section: Hydration Vs Entropy Balancementioning

confidence: 99%

How to explain microemulsions formed by solvent mixtures without conventional surfactants

Zemb

Klossek

Lopian

et al. 2016

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

179

195

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Ternary solutions containing one hydrotrope (such as ethanol) and two immiscible fluids, both being soluble in the hydrotrope at any proportion, show unexpected solubilization power and allow strange but yet unexplained membrane enzyme activity. We study the system ethanol-water-octanol as a simple model of such kinds of ternary solutions. The stability of "detergentless" micelles or microemulsions in such mixtures was proposed in the pioneering works of Barden and coworkers [Smith GD, Donelan CE, Barden RE (1977) J Colloid Interface Sci 60(3):488-496 and Keiser BA, Varie D, Barden RE, Holt SL (1979) J Phys Chem 83(10):1276-1281] in the 1970s and then, neglected, because no general explanation for the observations was available. Recent direct microstructural evidence by light, X-ray, and neutron scattering using contrast variation reopened the debate. We propose here a general principle for solubilization without conventional surfactants: the balance between hydration force and entropy. This balance explains the stability of microemulsions in homogeneous ternary mixtures based on cosolvents.A dding slightly hydrophobic compounds to water can lead to structureless solutions, aggregate formation, or even, formation of defined structures, such as micelles, in the case where the added compound is a surfactant. In ternary or quaternary mixtures containing at least one type of surfactant, the formation of microemulsions usually occurs in specific parts of the phase diagram. These macroscopically homogeneous, transparent liquids are composed of well-defined microstructures with specific signatures in scattering experiments (1). It was only recently that similar structures, designated as "pre-Ouzo," were found and characterized in ternary mixtures of two partly miscible solvents and one hydrotropic cosolvent (2). In this paper, we present a theory that explains and even predicts the existence of such structures in "detergentless" formulations.Ouzo, Limoncello, and Pommeau liquors are popular in several European countries and produced by maceration of plants with a specific amount of ethanolic solutions containing some waterinsoluble compounds (3). Adding water to those solutions leads to spontaneous formation of fine emulsions with a remarkable stability, a phenomenon that is called the "Ouzo effect" (4). Even common mouthwash products show a similar phenomenon. In common, they entirely clear up on addition of ethanol and get milky with the addition of water (5).Ternary surfactant-free model systems, such as decane-waterisobutoxyethanol [as studied by Shinoda and Kunieda (6)], however, show this Ouzo effect only for specific points in the composition diagram. The precondition for such behavior seems to be the mixture of two miscible (either completely or at least to a large degree) solvents 1 and 2 with a solute that can also be a liquid (7) (e.g., anethole in the case of Ouzo; component 3). This component 3 must be highly soluble in one solvent (e.g., ethanol) but poorly soluble in the other one (e.g., water) (8).Where...

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“…The volume of the rod-shaped particle observed in the microscope studies is 1 .0 ± 0.3 x 10 " cm'' (prolate ellipsoid) or 1 .5 ± 0.3 x 10-' x cm'' (cylinder), well within experimental error of that obtained in solution . C l.Ex micelles are hydrated to the extent of 0.8 g Hz0/g detergent (18) . If we assume that this is the major contribution to the hydration of the particle in solution, we calculate a minimum hydrodynamic radius of 8.2 f 0.3 rim, an f/ft,,,-tr, of 1 .8 ± 0.1 and an axial ratio of 15 ± 1 for the apo B-C,=E" complex studied in solution.…”

Section: Shadow Casting Of the Apo B-c12e8 Complexmentioning

confidence: 99%

Characterization of apolipoprotein B from human serum low density lipoprotein in n-dodecyl octaethyleneglycol monoether: an electron microscope study.

Zampighi¹,

Reynolds²,

Watt³

1980

The Journal of Cell Biology

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We have studied the structure of the totally delipidated polypeptide (apolipoprotein B [apo B]) present in low-density serum lipoprotein in detergent (n-dodecyl octaethyleneglycol monoether) solution by electron microscopy . The protein-detergent complex appears as a rodshaped particle, 75-80 nm long and 4.5-5.5 nm wide. The volume of this particle is consistent with the previously published composition reported by Watt and Reynolds (1980, Biochemistry 19:1593-1598 of two copies of apo B and five to six equivalent micelles of detergent . The asymmetric particle possesses a high degree of flexibility and a strong tendency to self-associate in an orderly fashion . The extent of this association is pH dependent .The main vehicle for plasma cholesterol transport is low-density lipoprotein (LDL), a quasi spherical particle 20-23 nm in diameter. The major subspecies of LDL in human plasma is LDL,, defined as a relatively homogeneous population of particles having a hydrated density of 1 .02-1 .063 g/cma. Numerous studies ofholo-LDL, have suggested that it is composed of a hydrophobic core of triglycerides and cholesteryl esters that are rendered water soluble by an as yet undefined "packaging" property of the protein (apolipoprotein B [apo B]) and associated phospholipids. Nuclear magnetic resonance studies have demonstrated that all phospholipid head groups are accessible to the aqueous milieu (23).Data from numerous laboratories have shown an invariant mass (510,000 daltons) of apo B in all LDL and very lowdensity lipoprotein (VLDL) particles (for a review, see reference 19). Empirical estimates of the polypeptide chain molecular weight by SDS gel electrophoresis (7,11,14) and chemical cleavage (2), have been reported and yield conflicting results. However, the molecular weight in concentrated solutions of guanidinium chloride has been determined by sedimentation equilibrium (a rigorous thermodynamic technique) in two laboratories and found to be 255,000 daltons (13, 17) . Therefore, LDL, must contain two copies of apo B per particle (dimeric) .Both ionic and nonionic detergents have been used to study the protein component of holo-LDL, (6,8,14,16,21). Inves-THE JOURNAL OF CELL BIOLOGY " VOLUME 87 DECEMBER 1980 555-561 ©The Rockefeller University Press " 0021-9525/80/12/0555/07 $1 .00 tigation of the properties of apo B (5, 12) in the presence of bound detergent (such as SDS, Triton X-100, and n-dodecyl octaethyleneglycol monoether [C12E8]) indicates that the dimeric form (8,16,21) ofthis protein is retained when all native lipids are removed. Additionally, the nonionic detergent, C12E8, maintains the secondary structure of apo B as assessed by circular dichroism (21).Unlike holo-LDL,, apo B in this detergent appears to be highly asymmetric with a frictional ration (f/fm r1.dm,ed 1) of 2.0-2.3. Hydrodynamic studies with spherical or nearly spherical globular proteins characteristically give frictional ratios between 1 .0 and 1 .3. Because f/fm; (1,yarated) is a measure of both the deviation of a particle f...

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Size and shape of globular micelles formed in aqueous solution by n-alkyl polyoxyethylene ethers

Cited by 277 publications

References 7 publications

Anomalous interaction of the acetylcholine receptor protein with the nonionic detergent Triton X-114.

Anomalous interaction of the acetylcholine receptor protein with the nonionic detergent Triton X-114.

How to explain microemulsions formed by solvent mixtures without conventional surfactants

Characterization of apolipoprotein B from human serum low density lipoprotein in n-dodecyl octaethyleneglycol monoether: an electron microscope study.

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