Testing Classical Approach to Polymer Solutions on SAXS Data of λ-Carrageenan, κ-Carrageenan and Methylcellulose Systems.

In this paper we present the performance of the classical approach to polymer solutions in evaluation and interpretation of the experimental SAXS data obtained for aqueous solutions of two gelling polysaccharides κ-carrageenan and methylcellulose and a non-gelling polysaccharide λ-carrageenan. In a systematic structural SAXS study of various types of polymer solutions we pointed out and discussed the issues encountered and connected to the fact that the studied gels are obviously not "homogeneous gels" in terms of the structural details that the SAXS technique can resolve and the issues connected to the limited experimental resolution of the SAXS technique for such systems. In parallel the necessary modifications of the classical approach equations for the evaluation of the SAXS data are discussed. Furthermore, the detailed structural results of the studied aqueous polymeric systems in liquid state, during the onset of the gelation, and even in the gel state are presented.

Modular and tunable alternative surfactants for biopharmaceuticals provide insights into Surfactant's Structure-Function relationship.

Surface-induced aggregation of protein therapeutics is opposed by employing surfactants, which are ubiquitously used in drug product development, with polysorbates being the gold standard. Since poloxamer 188 is currently the only generally accepted polysorbate alternative, but cannot be ubiquitously applied, there is a strong need to develop surfactant alternatives for protein biologics that would complement and possibly overcome known drawbacks of existing surfactants. Yet, a severe lack of structure-function relationship knowledge complicates the development of new surfactants. Herein, we perform a systematic analysis of the structure-function relationship of three classes of novel alternative surfactants. Firstly, the mode of action is thoroughly characterized through tensiometry, calorimetry and MD simulations. Secondly, the safety profiles are evaluated through cell-based in vitro assays. Ultimately, we could conclude that the alternative surfactants investigated possess a mode of action and safety profile comparable to polysorbates. Moreover, the biophysical patterns elucidated here can be exploited to precisely tune the features of future surfactant designs.

Solvation of nonionic poly(ethylene oxide) surfactant Brij 35 in organic and aqueous-organic solvents.

HYPOTHESIS: By combining the experimental small- and wide-angle x-ray scattering (SWAXS) method with molecular dynamics simulations and the theoretical 'complemented-system approach' it is possible to obtain detailed information about the intra- and inter-molecular structure and dynamics of the solvation and hydration of the surfactant in organic and mixed solvents, e.g., of the nonionic surfactant Brij 35 (C12E23) in alcohols and aqueous alcohol-rich ternary systems. This first application of the complemented-system approach to the surfactant system will promote the use of this powerful methodology that is based on experimental and calculated SWAXS data in studies of colloidal systems. By applying high-performance computing systems, such an approach is readily available for studies in the colloidal domain. EXPERIMENTS: SWAXS experiments and MD simulations were performed for binary Brij 35/alcohol and ternary Brij 35/water/alcohol systems with ethanol, n-butanol and n-hexanol as the organic solvent component at 25 °C. FINDINGS: We confirmed the presence of solvated Brij 35 monomers in the studied organic media, revealed their preferential hydration and discussed their structural and dynamic features at the intra- and inter-molecular levels. Anisotropic effective surfactant molecular conformations were found. The influence of the hydrophobicity of the organic solvent on the hydration phenomena of surfactant molecules was explained.

Structural, rheological and dynamic aspects of hydrogen-bonding molecular liquids: Aqueous solutions of hydrotropic tert-butyl alcohol.

HYPOTHESIS: The structural details, viscosity trends and dynamic phenomena in t-butanol/water solutions are closely related on the molecular scales across the entire composition range. Utilizing the experimental small- and wide-angle x-ray scattering (SWAXS) method, molecular dynamics (MD) simulations and the 'complemented-system approach' method developed in our group it is possible to comprehensively describe the structure-viscosity-dynamics relationship in such structurally versatile hydrogen-bonded molecular liquids, as well as in similar, self-assembling systems with pronounced molecular and supramolecular structures at the intra-, inter-, and supra-molecular scales. EXPERIMENTS: The SWAXS and x-ray diffraction experiments and MD simulations were performed for aqueous t-butanol solutions at 25 °C. Literature viscosity and self-diffusion data were also used. FINDINGS: The interpretive power of the proposed scheme was demonstrated by the extensive and diverse results obtained for aqueous t-butanol solutions across the whole concentration range. Four composition ranges with qualitatively different structures and viscosity trends were revealed. The experimental and calculated zero-shear viscosities and molecular self-diffusion coefficients were successfully related to the corresponding structural details. The hydrogen bonds that were, along with hydrophobic effects, recognized as the most important driving force for the formation of t-butanol aggregates, show intriguing lifetime trends and thermodynamic properties of their formation.

Supramolecular structure vs. rheological properties: 1,4-Butanediol at room and elevated temperatures.

HYPOTHESIS: The molecular hydrogen-bonding process in liquids with relatively small molecules, like butan-1,4-diol (BDO), results in interesting molecular-aggregation phenomena. These are reflected in a supramolecular self-assembly type of structure that is also expected to importantly influence the rheological properties of the system. The combination of experimental and theoretical methods should be able to reveal such influences in the important feedstock chemical BDO at low and moderate temperatures and further provide an application of the verified BDO model for a theoretical study of the structure at higher temperatures, for which serious health hazards make extensive experimental studies difficult. EXPERIMENTS: BDO was studied in the temperature range between 25 and 225 °C utilizing the experimental small- and wide-angle x-ray scattering method, molecular dynamics simulations, and the 'complemented-system approach'. FINDINGS: The theoretical results were experimentally verified and revealed important novel temperature-dependent structure and viscosity-related information, e.g., on aggregate sizes and self-diffusion coefficients, that would remain hidden in purely experimental studies. BDO has diverse applicability in many fields of research and industry, where it is often exposed to high temperatures. Using an experimentally verified model we were able to calculate reliable viscosity and self-diffusion coefficient values for the BDO molecules under such conditions.

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

A detailed data analysis utilizing the string-of-beads model was performed on experimental small-angle X-ray scattering (SAXS) curves in a targeted structural study of three, very important, industrial polysaccharides. The results demonstrate the quality of performance for this model on three polymers with quite different thermal structural behavior. Furthermore, they show the advantages of the model used by way of excellent fits in the ranges where the classic approach to the small-angle scattering data interpretation fails and an additional 3D visualization of the model's molecular conformations and anticipated polysaccharide supramolecular structure. The importance of this study is twofold: firstly, the methodology used and, secondly, the structural details of important biopolymers that are widely applicable in practice.

Physicochemical data on aqueous polymeric systems of methyl cellulose and lambda- and kappa-carrageenan: SAXS, rheological, densitometry, and sound velocity measurements.

General as well as more specific physicochemical data obtained by studying the structure and various dynamical properties of aqueous polymer systems of methyl cellulose, [Formula: see text]carrageenan, and [Formula: see text]carrageenan are presented in graphical and numeric tabular form. The data provide basic polymer characterization info as also a specific structural and dynamical info for aqueous solutions of three industrially very important polymers (food additives) that are available commercially. The commercial availability has much bigger impact to applications, research and connected advances, when the basic substances are well characterized - a feature that is still missing for many commercially available polymers unfortunately.