title: Atomic model and micelle dynamics of QS-21 saponin.
abstract: QS-21 is a saponin extracted from Quillaja saponaria, widely investigated as a vaccine immunoadjuvant. However, QS-21 use is mainly limited by its chemical instability, significant variety in molecular composition and low tolerance dose in mammals. Also, this compound tends to form micelles in a concentration-dependent manner. Here, we aimed to characterize its conformation and the process of micelle formation, both experimentally and computationally. Therefore, molecular dynamics (MD) simulations were performed in systems containing different numbers of QS-21 molecules in aqueous solution, in order to evaluate the spontaneous micelle formation. The applied methodology allowed the generation of micelles whose sizes were shown to be in high agreement with small-angle X-ray scattering (SAXS). Furthermore, the ester linkage between fucose and acyl chain was less solvated in the micellar form, suggesting a reduction in hydrolysis. This is the first atomistic interpretation of previous experimental data, the first micellar characterization of saponin micelles by SAXS and first tridimensional model of a micelle constituted of saponins, contributing to the understanding of the molecular basis of these compounds.
authors.affiliation: Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Av Bento Gonçalves 9500, CP 15005, Porto Alegre 91500-970, RS, Brazil. conrado.pedebos@ufrgs.br.
authors.forename: Conrado
authors.initials: C
authors.lastname: Pedebos
authors.affiliation: Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Av Bento Gonçalves 9500, CP 15005, Porto Alegre 91500-970, RS, Brazil. laerciofachin@cbiot.ufrgs.br.
authors.forename: Laércio
authors.initials: L
authors.lastname: Pol-Fachin
authors.affiliation: Departament de Tecnologia Química i de Tensioactius, Institut de Química Avançada de Catalunya, IQAC_CSIC, Jordi Girona, 18-26, Barcelona 08034, Spain. ramon.pons@iqac.csic.es.
authors.forename: Ramon
authors.initials: R
authors.lastname: Pons
authors.affiliation: Instituto de Física, Universidade Federal do Rio Grande do Sul, CP15051, Porto Alegre 91501-970, RS, Brazil. cilaineteix@if.ufrgs.br.
authors.forename: Cilâine V
authors.initials: CV
authors.lastname: Teixeira
authors.affiliation: Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Av Bento Gonçalves 9500, CP 15005, Porto Alegre 91500-970, RS, Brazil. hverli@cbiot.ufrgs.br.
authors.forename: Hugo
authors.initials: H
authors.lastname: Verli
mesh_terms: D008823:Micelles; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D012503:Saponins / Q000737:chemistry*; D053838:Scattering, Small Angle; D012996:Solutions; D012997:Solvents; D014961:X-Ray Diffraction
chemical_list: D008823:Micelles; D012503:Saponins; D012996:Solutions; D012997:Solvents; C078785:saponin QA-21V1