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Title: Size And Shape of Detergent Micelles Determined By Small-Angle X-Ray Scattering

Abstract

We present a systematic analysis of the aggregation number and shape of micelles formed by nine detergents commonly used in the study of membrane proteins. Small-angle X-ray scattering measurements are reported for glucosides with 8 and 9 alkyl carbons (OG/NG), maltosides and phosphocholines with 10 and 12 alkyl carbons (DM/DDM and FC-10/FC-12), 1,2-dihexanoyl-sn-glycero-phosphocholine (DHPC), 1-palmitoyl-2-hydroxy-sn-glycero-3-[phospho-rac-(1-glycerol)] (LPPG), and 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate (CHAPS). The SAXS intensities are well described by two-component ellipsoid models, with a dense outer shell corresponding to the detergent head groups and a less electron dense hydrophobic core. These models provide an intermediate resolution view of micelle size and shape. In addition, we show that Guinier analysis of the forward scattering intensity can be used to obtain an independent and model-free measurement of the micelle aggregation number and radius of gyration. This approach has the advantage of being easily generalizable to protein-detergent complexes, where simple geometric models are inapplicable. Furthermore, we have discovered that the position of the second maximum in the scattering intensity provides a direct measurement of the characteristic head group-head group spacing across the micelle core. Our results for the micellar aggregation numbers and dimensions agree favorably with literature values as far as they are available. Wemore » de novo determine the shape of FC-10, FC-12, DM, LPPG, and CHAPS micelles and the aggregation numbers of FC-10 and OG to be ca. 50 and 250, respectively. Combined, these data provide a comprehensive view of the determinants of micelle formation and serve as a starting point to correlate detergent properties with detergent-protein interactions.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Stanford Linear Accelerator Center (SLAC)
Sponsoring Org.:
USDOE
OSTI Identifier:
958667
Report Number(s):
SLAC-REPRINT-2009-006
Journal ID: ISSN 1089-5647; JPCBFK; TRN: US201001%%803
DOE Contract Number:
AC02-76SF00515
Resource Type:
Journal Article
Resource Relation:
Journal Name: J.Phys.Chem.B111:12427,2007; Journal Volume: 111; Journal Issue: 43
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; DETERGENTS; DIMENSIONS; ELECTRONS; MEMBRANE PROTEINS; RESOLUTION; SCATTERING; SHAPE; SULFONATES; CHEM, PHYS

Citation Formats

Lipfert, Jan, Columbus, Linda, Chu, Vincent B., Lesley, Scott A., Doniach, Sebastian, and /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept. /SLAC, SSRL /Pasteur Inst., Paris /Scripps Res. Inst. /Novartis Res. Found. Size And Shape of Detergent Micelles Determined By Small-Angle X-Ray Scattering. United States: N. p., 2009. Web.
Lipfert, Jan, Columbus, Linda, Chu, Vincent B., Lesley, Scott A., Doniach, Sebastian, & /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept. /SLAC, SSRL /Pasteur Inst., Paris /Scripps Res. Inst. /Novartis Res. Found. Size And Shape of Detergent Micelles Determined By Small-Angle X-Ray Scattering. United States.
Lipfert, Jan, Columbus, Linda, Chu, Vincent B., Lesley, Scott A., Doniach, Sebastian, and /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept. /SLAC, SSRL /Pasteur Inst., Paris /Scripps Res. Inst. /Novartis Res. Found. 2009. "Size And Shape of Detergent Micelles Determined By Small-Angle X-Ray Scattering". United States. doi:.
@article{osti_958667,
title = {Size And Shape of Detergent Micelles Determined By Small-Angle X-Ray Scattering},
author = {Lipfert, Jan and Columbus, Linda and Chu, Vincent B. and Lesley, Scott A. and Doniach, Sebastian and /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept. /SLAC, SSRL /Pasteur Inst., Paris /Scripps Res. Inst. /Novartis Res. Found.},
abstractNote = {We present a systematic analysis of the aggregation number and shape of micelles formed by nine detergents commonly used in the study of membrane proteins. Small-angle X-ray scattering measurements are reported for glucosides with 8 and 9 alkyl carbons (OG/NG), maltosides and phosphocholines with 10 and 12 alkyl carbons (DM/DDM and FC-10/FC-12), 1,2-dihexanoyl-sn-glycero-phosphocholine (DHPC), 1-palmitoyl-2-hydroxy-sn-glycero-3-[phospho-rac-(1-glycerol)] (LPPG), and 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate (CHAPS). The SAXS intensities are well described by two-component ellipsoid models, with a dense outer shell corresponding to the detergent head groups and a less electron dense hydrophobic core. These models provide an intermediate resolution view of micelle size and shape. In addition, we show that Guinier analysis of the forward scattering intensity can be used to obtain an independent and model-free measurement of the micelle aggregation number and radius of gyration. This approach has the advantage of being easily generalizable to protein-detergent complexes, where simple geometric models are inapplicable. Furthermore, we have discovered that the position of the second maximum in the scattering intensity provides a direct measurement of the characteristic head group-head group spacing across the micelle core. Our results for the micellar aggregation numbers and dimensions agree favorably with literature values as far as they are available. We de novo determine the shape of FC-10, FC-12, DM, LPPG, and CHAPS micelles and the aggregation numbers of FC-10 and OG to be ca. 50 and 250, respectively. Combined, these data provide a comprehensive view of the determinants of micelle formation and serve as a starting point to correlate detergent properties with detergent-protein interactions.},
doi = {},
journal = {J.Phys.Chem.B111:12427,2007},
number = 43,
volume = 111,
place = {United States},
year = 2009,
month = 4
}
  • The influence of counterion on micelle structure is examined for a series of trimethylammonium halide surfactants C{sub n}TAX = C{sub n}H{sub 2n+1} N(CH{sub 3}){sub 3}{sup +}X{sup {minus}}(X = NO{sub 3}, Br, CH{sub 3}SO{sub 4}, Cl, and OH) by small-angle neutron scattering. The variation of micelle structure as a function of chain length (n - 12, 14, and 16) and surfactant concentration (0.05, 0.1, and 0.2 mol dm{sup {minus}3}) is also studied. It was found that the aggregation number, N, increases in the order of NO{sub 3} > Br > CH{sub 3}SO{sub 4} > Cl >> OH. This order is roughlymore » correlated to the fractional micellar charge, {beta}, which follows the order OH > Cl > CH{sub 3}SO{sub 4} {approximately} Br {approximately}NO{sub 3}. Fractional charge changes very little and in an irregular fashion when n and/or surfactant concentration are increased, but the aggregation number increases with respect to both. 13 refs., 2 figs., 3 tabs.« less
  • We have characterized micelle structure and intermicelle interaction for the detergents lauryldimethylamine N-oxide, LDAO, and n-octyl-[beta]-D-glucoside, OG, under conditions used for protein crystallization using SANS. We found that LDAO and OG micelles differ significantly in size, sensitivity to heptanetriol, and nature of intermicelle interactions. Our results suggest that successful crystallization methods can be rationalized in terms of an optimization of micelle size, number density, flexibility of micelle radius of curvature, and suppression of intermicelle interactions. LDAO and OG micelles were found to differ significantly in size and shape. The LDAO micelle was found to be best fit as an ellipsoidmore » with semiaxes of 30.6 and 19.4 [angstrom], while the OG micelle was found to be spherical with a radius of 22.9 [angstrom]. The addition of heptanetriol to pure LDAO resulted in the formation of smaller, spherical, mixed micelles with radii in the range 17-21 [angstrom], depending upon conditions. The results suggest that both micelle size and curvature restrictions may contribute to the incompatibility of LDAO for protein crystallization in the absence of additional amphiphiles. 32 refs., 8 figs., 3 tabs.« less
  • A large group of functional nanomaterials employed in biomedical applications, including targeted drug delivery, relies on amphiphilic polymers to encapsulate therapeutic payloads via self-assembly processes. Knowledge of the micelle structures will provide critical insights into design of polymeric drug delivery systems. Core–shell micelles composed of linear diblock copolymers poly(ethylene glycol)-b-poly(caprolactone) (PEG-b-PCL), poly(ethylene oxide)-b-poly(lactic acid) (PEG-b-PLA), as well as a heterografted brush consisting of a poly(glycidyl methacrylate) backbone with PEG and PLA branches (PGMA-g-PEG/PLA) were characterized by dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) measurements to gain structural information regarding the particle morphology, core–shell size, and aggregation number. Themore » structural information at this quasi-equilibrium state can also be used as a reference when studying the kinetics of polymer micellization.« less
  • A large group of functional nanomaterials employed in biomedical applications, including targeted drug delivery, relies on amphiphilic polymers to encapsulate therapeutic payloads via self-assembly processes. Knowledge of the micelle structures will provide critical insights into design of polymeric drug delivery systems. Core–shell micelles composed of linear diblock copolymers poly(ethylene glycol)-b-poly(caprolactone) (PEG-b-PCL), poly(ethylene oxide)-b-poly(lactic acid) (PEG-b-PLA), as well as a heterografted brush consisting of a poly(glycidyl methacrylate) backbone with PEG and PLA branches (PGMA-g-PEG/PLA) were characterized by dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) measurements to gain structural information regarding the particle morphology, core–shell size, and aggregation number. Themore » structural information at this quasi-equilibrium state can also be used as a reference when studying the kinetics of polymer micellization.« less
  • X-rays are scattered in the small angle range on particles of colloidal dimensions. From the dependence of angle and the absolute value of the scattering intensity, conclusions can be drawn as to particle size and shape. Such measurements render valuable service, e.g., for the investigation of proteins, fibres, plastics, alloys, and catalysts. A review is given on principles of theory and apparatus and on experimental possibilities of the method. (auth)