The interaction of three dicationic (gemini) surfactants-3,3'-[1,6-(2,5-dioxahexane)]bis(1-dodecylimidazolium) chloride (oxyC2), 3,3'-[1,16-(2,15-dioxahexadecane)]bis(1-dodecylimidazolium) chloride (oxyC12), and 1,4-bis(butane)imidazole-1-yl-3-dodecylimidazolium chloride (C4)--with bovine serum albumin (BSA) has been studied by the use of small-angle X-ray scattering (SAXS), circular dichroism (CD), and (1)H nuclear magnetic resonance diffusometry. The results of CD studies show that the conformation of BSA was changed dramatically in the presence of all studied surfactants. The greater decrease (from 56 to 24%) in the α-helical structure of BSA was observed for oxyC2 surfactant. The radii of gyration estimated from SAXS data varied between 3 and 26 nm for the BSA/oxyC2 and BSA/oxyC12 systems. The hydrodynamic radius of the BSA/surfactant system estimated from NMR diffusometry varies between 5 and 11 nm for BSA/oxyC2 and 5 and 8 nm for BSA/oxyC12.
Gemini surfactants and their interactions with proteins have gained considerable scientific interest, especially when amyloidogenic proteins are taken into account. In this work, the influence of two selected dicationic (gemini) surfactants (3,3′-[1,8-(2,7-dioxaoctane)]bis(1-dodecylimidazolium) chloride and 3,3′-[1,12-(2,11-dioxadodecane)]bis(1-dodecylimidazolium) chloride) on two model proteins, bovine serum albumin (BSA) and hen egg white lysozyme (HEWL), have been investigated. A pronounced and sophisticated influence on BSA structure has been revealed, including a considerable change of protein radius of gyration as well as substantial alteration of its secondary structure. Radius of gyration has been found to rise significantly with addition of surfactants and to fall down for high surfactants concentration. Similarly, a remarkable fall of secondary structure (α-helix content) has been observed, followed by its partial retrieval for high surfactants concentration. A strong aggregation of BSA has been observed for a confined range of surfactants concentrations as well. In case of HEWL-gemini system, on the other hand, the protein-surfactant interaction was found to be weak. Molecular mechanisms explaining such behaviour of protein-surfactant systems have been proposed. The differences of properties of both studied surfactants have also been discussed.
The formation of amyloid plaques is being intensively studied, as this process underlies severe human diseases, including Alzheimer's disease, and the exact mechanism of this specific aggregation has not been resolved yet.
The amyloid aggregation process of amyloid β peptide is responsible for Alzheimer's disease, affecting millions of elderly people worldwide. Although there has been a great deal of attention directed toward tackling this disease, still no medicine has been found for this fatal disorder. To address this challenge, it is vital to thoroughly understand the molecular mechanism underlying the amyloid peptide aggregation process, as well as seek substances that could hamper this aggregation. In order to shed light on mechanisms leading to amyloidogenesis, we employed a microfluidic system to determine the possible influence of in vivo-like flow in the microchip channel itself on feline Aβ peptide amyloidogenesis. We have shown that shear forces occurring during such flow immensely accelerated peptide aggregation. We also tested the inhibitory influence of 3,3'-[1,6-(2,5-dioxahexane)]bis(1-dodecylimidazolium) dichloride gemini surfactant on peptide amyloidogenesis. Our results suggest that this surfactant may inhibit amyloid β fibril formation.
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