Benzoic acid and its methyl and propyl para-hydroxy derivatives are approved food preservatives and flavoring agents. Inclusive use of these additives in food, pharmaceuticals, and beauty and healthcare industries however raises concern about the quality and shelf life of the products. The safety levels of benzoates are controversial, even though studies have indicated that they may produce adverse health effects. This study employs nuclear magnetic resonance (NMR), infrared (IR), fluorescence anisotropy, the molecular docking approach, and electron microscopy to examine lysozyme, myoglobin, and cytochrome c under acidic and neutral-pH conditions and finds that benzoates bind to multiple independent sites on proteins by hydrogen-bonding and π-stacking interactions, although electrostatic interactions may also appear as neutral-pH conditions are approached. The benzoate-bound proteins enter the aggregation pathway to produce amorphous and perhaps occasional fibrillar structures. The concentration of benzoates needed to induce protein aggregation is much lower than the microbicidal and inhibitory concentrations prescribed by Food and Agriculture Organization of the United Nations.
Although considerable information is available regarding protein-sodium dodecyl sulfate (SDS) interactions, it is still unclear as to how much SDS is needed to denature proteins.The role of protein charge and micellar surfactant concentration on amyloid fibrillation is also unclear. This study reports on equilibrium measurements of SDS interaction with six model proteins and analyzes the results to obtain a general understanding of conformational breakdown, reorganization and restructuring of secondary structure, and entry into the amyloid fibrillar state. Significantly, all of these responses are entirely resolved at much lower than the critical micellar concentration (CMC) of SDS. Electrostatic interaction of the dodecyl sulfate anion (DS − ) with positive surface potential on the protein can completely unfold both secondary and tertiary structures, which is followed by protein chain restructuration to α-helices. All SDS-denatured proteins contain more α-helices than the corresponding native state. SDS interaction stochastically drives proteins to the aggregated fibrillar state. K E Y W O R D S amyloid fibrillation, protein-SDS interactions, SDS denaturation, SDS unfolding 1 | INTRODUCTIONThe wide range of applications of the sodium dodecyl sulfate (SDS)protein system, including a fundamental understanding of molecular structures in micelle mimetics of membranes [1] and industrial production of washes and hygiene products, has led to numerous studies on it. Work on the influence of SDS in protein folding [2] and metal ion binding, [3] thermodynamics and kinetics of proteinsurfactant interactions [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and forces involved therein, [21,22] and the complexity of changes brought about in the protein structure, [17,18,23,24] has been carried out. Nevertheless, questions remain, including the structure of the SDS-protein complex, the resistance of β-sheet proteins to denaturation, [6,11] shifting and restructuration of β ! α secondary structures, [22,25] the role of electrostatic vs hydrophobic interactions in altering the conformational landscape, [24] and the SDS-to-protein ratio-dependent aggregation of the complex. [5] The difficulties arise partly from the protein-specific SDS-resistance, termed kinetic stability, [6] anomalous SDS effects, [26] and the strong binding of the ionic surfactant to protein side chains, which allows only a narrow window in the submillimolar concentration for experimental work. For example, guanidinium hydrochloride which binds weakly to proteins is needed at molar concentrations to denature proteins, but substantial changes in the structure and conformation of proteins already take place at micromolar concentrations of SDS. [16] This study aims to provide a unified conceptual understanding of the action of SDS on protein structures and conformation with reference to the surfactant-binding isotherm and possible modes of binding. Experiments have been performed with six proteins: lysozyme, cytochrome c, myoglobin, α-lactalbumin, ...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.