title: Ethanol-perturbed amyloidogenic self-assembly of insulin: looking for origins of amyloid strains.
abstract: A model cosolvent, ethanol, has profound and diversified effects on the amyloidogenic self-assembly of insulin, yielding spectroscopically and morphologically distinguishable forms of beta-aggregates. The alcohol reduces hydrodynamic radii of insulin molecules, decreases enthalpic costs associated with aggregation-prone intermediate states, and accelerates the aggregation itself. Increasing the concentration of the cosolvent promotes curved, amorphous, and finally donut-shaped forms. According to FT-IR data, inter-beta-strand hydrogen bonding is stronger in fibrils formed in the presence of ethanol. Mechanisms underlying the polymorphism of insulin aggregates were investigated by spectroscopic (CD, FT-IR, and fluorescence anisotropy) and calorimetric (DSC and PPC) methods. The nonmonotonic character of the influence of ethanol on insulin aggregation suggests that both preferential exclusion (predominant at the low concentrations) and direct alcohol-protein interactions are involved. The perturbed hydration of aggregation nuclei appears to be a decisive factor in selection of a dominant mode of beta-strand alignment. It may override unfavorable structural consequences of an alternative strand-to-strand stacking, such as strained hydrogen bonding. A hypothetical mechanism of inducing different amyloid "strains" has been put forward. The cooperative character of fibril assembly creates enormous energy barriers for any interstrain transition, which renders the energy landscape comblike-shaped.
authors.affiliation: Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw, Poland. wdzwolak@unipress.waw.pl
authors.forename: Wojciech
authors.initials: W
authors.lastname: Dzwolak
authors.forename: Stefan
authors.initials: S
authors.lastname: Grudzielanek
authors.forename: Vytautas
authors.initials: V
authors.lastname: Smirnovas
authors.forename: Revanur
authors.initials: R
authors.lastname: Ravindra
authors.forename: Chiara
authors.initials: C
authors.lastname: Nicolini
authors.forename: Ralf
authors.initials: R
authors.lastname: Jansen
authors.forename: Anna
authors.initials: A
authors.lastname: Loksztejn
authors.forename: Sylwester
authors.initials: S
authors.lastname: Porowski
authors.forename: Roland
authors.initials: R
authors.lastname: Winter
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000145:classification / Q000378:metabolism*; D000817:Anilino Naphthalenesulfonates / Q000494:pharmacology; D000818:Animals; D052160:Benzothiazoles; D002151:Calorimetry; D002417:Cattle; D002942:Circular Dichroism; D000431:Ethanol / Q000494:pharmacology*; D007328:Insulin / Q000737:chemistry* / Q000145:classification / Q000378:metabolism*; D018625:Microscopy, Atomic Force; D011489:Protein Denaturation; D020836:Protein Structure, Quaternary / Q000187:drug effects; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D013844:Thiazoles / Q000494:pharmacology; D017186:Titrimetry
chemical_list: D000682:Amyloid; D000817:Anilino Naphthalenesulfonates; D052160:Benzothiazoles; D007328:Insulin; D013844:Thiazoles; C009462:thioflavin T; D000431:Ethanol; C027132:1-anilino-8-naphthalenesulfonate