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Self-Assembly of the Bio-Surfactant Aescin in Solution: A Small-Angle X-ray Scattering and Fluorescence Study

1
Physical and Biophysical Chemistry, Bielefeld University, 33615 Bielefeld, Germany
2
Organic and Bioorganic Chemistry, Bielefeld University, 33615 Bielefeld, Germany
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Colloids Interfaces 2019, 3(2), 47; https://doi.org/10.3390/colloids3020047
Received: 22 February 2019 / Revised: 16 April 2019 / Accepted: 17 April 2019 / Published: 25 April 2019
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Abstract

This work investigates the temperature-dependent micelle formation as well as the micellar structure of the saponin aescin. The critical micelle concentration ( c m c ) of aescin is determined from the concentration-dependent autofluorescence (AF) of aescin. Values between c m c aescin , AF (10 C) = 0.38 ± 0.09 mM and c m c aescin , AF (50 C) = 0.32 ± 0.13 mM were obtained. The significance of this method is verified by tensiometry measurements. The value determined from this method is within the experimental error identical with values obtained from autofluorescence ( c m c aescin , T ( WP ) (23 C) = 0.33 ± 0.02 mM). The structure of the aescin micelles was investigated by small-angle X-ray scattering (SAXS) at 10 and 40 C. At low temperature, the aescin micelles are rod-like, whereas at high temperature the structure is ellipsoidal. The radii of gyration were determined to ≈31 Å (rods) and ≈21 Å (ellipsoid). The rod-like shape of the aescin micelles at low temperature was confirmed by transmission electron microscopy (TEM). All investigations were performed at a constant pH of 7.4, because the acidic aescin has the ability to lower the pH value in aqueous solution. View Full-Text
Keywords: saponin; aescin; critical micelle concentration (cmc); autofluorescence; small-angle X-ray scattering (SAXS); transmission electron microscopy (TEM); micelle structure saponin; aescin; critical micelle concentration (cmc); autofluorescence; small-angle X-ray scattering (SAXS); transmission electron microscopy (TEM); micelle structure
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Dargel, C.; Geisler, R.; Hannappel, Y.; Kemker, I.; Sewald, N.; Hellweg, T. Self-Assembly of the Bio-Surfactant Aescin in Solution: A Small-Angle X-ray Scattering and Fluorescence Study. Colloids Interfaces 2019, 3, 47.

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Colloids Interfaces EISSN 2504-5377 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
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