Evaluating SAXS Results on Aqueous Solutions of Various Bacterial Levan utilizing the String-of-Beads Model

Abstract

Polysaccharide levan is a homopolymer of fructose and is an important component of plants, yeast, fungi and some bacterial biofilms. In this paper we report on the structural properties of aqueous solutions of bacterial levan utilizing smallangle X-ray scattering and light microscopy. In addition to commercially available levan isolated from Zymomonas mobilis and Erwinia herbicola, we also studied levan isolated and purified from the biofilm of Bacillus subtilis. The smallangle X-ray scattering data were analyzed by the string-of-beads model that revealed qualitative differences in the structure of levan molecules. Levan can be represented as a semi-flexible chain that interacts intra-and inter-molecularly and therefore forms various suprastructures on larger size scales. Increasing the concentration of levan makes the levan structure more compact, which was observed on the nano as well as on the micro scale. The structures with most homogeneously distributed polymer local density were found in B. subtilis levan solutions.

Supramolecular structure of methyl cellulose and lambda- and kappa-carrageenan in water: SAXS study using the string-of-beads model

“…(Cerar et al, 2015)). We have also observed very similar behavior in some other cases (Benigar et al, 2015).…”

“…The experimental SAXS data was analyzed using the string-of-beads model, which is explained into detail elsewhere (Benigar et al, 2015;Benigar et al, 2016;Dogsa et al, 2008;Dogsa et al, 2014;Orehek et al, 2013). In the following text the basic features of this model and its application to interpreting SAXS data are briefly outlined.…”

“…For the SAXS data evaluation each modelled representative () Pq is tested according to the following expression for the total scattering function   Iq (Benigar et al, 2015;Benigar et al, 2016;Coviello et al, 1998;Dogsa et al, 2014;Orehek et al, 2013;Y. Yuguchi et al, 1996): (Cerar et al, 2015)).…”

“…Due to their chemical and structural variability they exhibit different structural and dynamic phenomena that continue to present a great research challenge, even for modern techniques. In our studies we focused on structural and dynamic investigations utilizing various scattering techniques, i.e., small-angle X-ray scattering (SAXS), static light scattering (SLS) and dynamic light scattering (DLS) Benigar et al, 2015;Benigar et al, 2016;Cerar, Jamnik, & Tomsic, 2015;Dogsa, Štrancar, Laggner, & Stopar, 2008;Dogsa et al, 2014;Orehek et al, 2013). The advantage of these techniques is that they are, in general, nondestructive and can directly probe the polymers in aqueous solutions.…”

“…Nonetheless, in the present study we successfully extend the range of the appropriate SAXS data analysis for the studied polysaccharide systems by also taking into account the contribution of the form factor of the polymer chain or its segments. We achieve this by applying the string-of-beads model (Benigar et al, 2015;Benigar et al, 2016;Dogsa et al, 2008;Dogsa et al, 2014;Orehek et al, 2013), which is briefly described later in the text and provides some additional information about the polymer structure in comparison to the classic approach. Furthermore, it also enables a straightforward visualization of the modeled molecular configurations and even of the anticipated modeled supramolecular structure of the system.…”