Biomolecular complexation on the “wrong side” : a case study of the influence of salts and sugars on the interactions between bovine serum albumin and sodium polystyrene sulfonate

Simončič, Matjaž (author), Hritz, Jozef (author), Lukšič, Miha (author)

In the protein purification, drug delivery, food industry, and biotechnological applications involving protein−polyelectrolyte complexation, proper selection of co-solutes and solution conditions plays a crucial role. The onset of (bio)macromolecular complexation occurs even on the so-called “wrong side” of the protein isoionic point where both the protein and the polyelectrolyte are net like-charged. To gain mechanistic insights into the modulatory role of salts (NaCl, NaBr, and NaI) and sugars (sucrose and sucralose) in protein−polyelectrolyte complexation under such conditions, interaction between bovine serum albumin (BSA) and sodium polystyrene sulfonate (NaPSS) at pH = 8.0 was studied by a combination of isothermal titration calorimetry, fluorescence spectroscopy, circular dichroism, and thermodynamic modeling. The BSA−NaPSS complexation proceeds by two binding processes (first, formation of intrapolymer complexes and then formation of interpolymer complexes), both driven by favorable electrostatic interactions between the negatively charged sulfonic groups (−SO$_3^−$) of NaPSS and positively charged patches on the BSA surface. Two such positive patches were identified, each responsible for one of the two binding processes. The presence of salts screened both short-range attractive and long-range repulsive electrostatic interactions between both macromolecules, resulting in a nonmonotonic dependence of the binding affinity on the total ionic strength for both binding processes. In addition, distinct anion-specific effects were observed (NaCl < NaBr < NaI). The effect of sugars was less pronounced: sucrose had no effect on the complexation, but its chlorinated analogue, sucralose, promoted it slightly due to the screening of long-range repulsive electrostatic interactions between BSA and NaPSS. Although short-range non-electrostatic interactions are frequently mentioned in the literature in relation to BSA or NaPSS, we found that the main driving force of complexation on the “wrong side” are electrostatic interactions.

• Language: English
• Keywords: protein-polyelectrolyte complexation, sucrose, sucralose, electrostatic interactions, salt-specific effects, carbohydrates, complexation, ionic strength, salts, titration
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Publication status: Published
• Publication version: Version of Record
• Year: 2022
• Number of pages: Str. 4412–4426
• Numbering: Vol. 23, iss. 10
• PID: 20.500.12556/RUL-141995
• UDC: 577.322
• ISSN on article: 1525-7797
• DOI: 10.1021/acs.biomac.2c00933
• COBISS.SI-ID: 122596099
• Publication date in RUL: 14.10.2022

Record is a part of a journal

• Title: Biomacromolecules
• Publisher: American Chemical Society
• ISSN: 1525-7797
• COBISS.SI-ID: 22445317

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: kompleksacija protein-polielektrolit, saharoza, sukraloza, elektrostatske interakcije, ionospecifični efekti