Small-angle X-ray scattering reveals hollow nanostructures in ι- and κ-carrageenan/surfactant complexes

被引:21
作者
Shtykova, EV
Shtykova, EV
Volkov, VV
Konarev, PV
Dembo, AT
Makhaeva, EE
Ronova, IA
Khokhlov, AR
Reynaers, H
Svergun, DI
机构
[1] Russian Acad Sci, Inst Crystallog, Moscow 117333, Russia
[2] Moscow MV Lomonosov State Univ, Dept Phys, Moscow 117234, Russia
[3] Russian Acad Sci, Inst Organoelement Cpds, Moscow 117813, Russia
[4] Catholic Univ Louvain, Lab Mol Struct Chem, B-3001 Heverlee, Belgium
[5] European Mol Biol Lab, D-22603 Hamburg, Germany
关键词
small-angle X-ray scattering; internal structure; gel/surfactant complex; iota- and kappa-carrageenan;
D O I
10.1107/S0021889803006198
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Complexes of polyelectrolyte gels with oppositely charged surfactants form ordered polymer matrices with unique structure properties, which can be used in a wide range of medical, chemical and physical applications. Ordered matrices made of natural components are of special interest for medical and biological purposes. In the present study, self-organised complexes of native iota- and kappa-carrageenans formed with oppositely charged cetylpyridinium chloride (CPC) are prepared and structurally characterised using small-angle X-ray scattering (SAXS). Starting from the molar ratio CPC/(charge of carrrageenan) of 0.2, the carrageenan gel shrinks and ordered motifs in its internal structure are formed. The internal order in the sample is reflected by the Bragg peaks in the scattering patterns which permit to compute periodicity and characteristic sizes of the ordered regions. Moreover, strong central scattering appears and the calculated fractal dimensions indicate that these regions are organised in well defined clusters. The periodicity of the ordered motifs computed from the Bragg peaks in the scattering patterns corresponds to the width of the surfactant bilayer (about 4.0 nm) for all the complexes. The crystallite size ranges from 25 nm to 40 nm depending on the type of carrageenan and on the amount of CPC. A model of the ordered fragments is proposed whereby the carrageenan/surfactant bilayers are regularly packed at the walls of hollow cylindric clusters with the outer radius of about 8 nm and height 40 nm. More detailed ab initio models indicate that these particles are formed by bent worm-like substructures with the cross-section coinciding to the thickness of the carrageenan/CPC bilayer. Thanks to a higher charge density per monomer, iota-carrageenans form more regular structures than kappa-carrageenans.
引用
收藏
页码:669 / 673
页数:5
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