Biomolecular complexation on the “wrong side”

ǂa ǂcase study of the influence of salts and sugars on the interactions between bovine serum albumin and sodium polystyrene sulfonate

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

Abstract

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.

Keywords

kompleksacija protein-polielektrolit;saharoza;sukraloza;elektrostatske interakcije;ionospecifični efekti;protein-polyelectrolyte complexation;sucrose;sucralose;electrostatic interactions;salt-specific effects;

Data

Language:	English
Year of publishing:	2022
Typology:	1.01 - Original Scientific Article
Organization:	UL FKKT - Faculty of Chemistry and Chemical Technology
UDC:	577.322
COBISS:	122596099
ISSN:	1525-7797
Views:	71
Downloads:	37
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	Slovenian
Secondary keywords:	kompleksacija protein-polielektrolit;saharoza;sukraloza;elektrostatske interakcije;ionospecifični efekti;
Type (COBISS):	Article
Pages:	str. 4412-4426
Volume:	ǂVol. ǂ23
Issue:	ǂiss. ǂ10
Chronology:	10 Oct. 2022
DOI:	10.1021/acs.biomac.2c00933
ID:	16746398