Fluoroalcohol-induced structural changes of proteins: some aspects of cosolvent-protein interactions

Abstract

The conformational transitions of bovine beta-lactoglobulin A and phosphoglycerate kinase from yeast induced by hexafluoroisopropanol (HFIP) and trifluoroethanol (TFE) have been studied by dynamic light scattering and circular dichroism spectroscopy in order to elucidate the potential of fluoroalcohols to bring about structural changes of proteins. Moreover, pure fluoroalcohol-water mixed solvents were investigated to prove the relation between cluster formation and the effects on proteins. The results demonstrate that cluster formation is mostly an accompanying phenomenon because important structural changes of the proteins occur well below the critical concentration of fluoroalcohol at which the formation of clusters sets in. According to our light scattering experiments, the remarkable potential of HFIP is a consequence of extensive preferential binding. Surprisingly, preferential binding seems to play a vanishing role in the case of TFE. However, the comparable Stokes radii of both proteins in the highly helical state induced by either HFIP or TFE point to a similar degree of solvation in both mixed solvents. This shows that direct binding or an indirect mechanism must be equally taken into consideration to explain the effects of alcohols on proteins. The existence of a compact helical intermediate with non-native secondary structure on the transition of beta-lactoglobulin A from the native to the highly helical state is clearly demonstrated.

Solvation in protein (un)folding of melittin tetramer–monomer transition

“…In particular, from knowledge of the TFE dependence of the bulk solvent viscosity (25), at the transition concentration we estimate there is at least 40% TFE around Trp, Ϸ4 times the bulk concentration. Previous X-ray and dynamic light scattering experiments (15,32,33) and molecular modeling studies (20) suggest that the maximum for solvent clustering in water cosolvent occurs near 30-40% (vol/ vol) TFE and that the alcohol concentration is approximately twice that of the bulk concentration; in accord with our solvation measurements. However, we are unaware of another study in which the dynamics associated with solvent clustering near the protein surface have been measured.…”

“…These results indicate TFE and other fluorinated alcohols create a coating around the peptide, expelling water from the peptide surface, and that the density of TFE is Ϸ2 times higher at the surface of the peptide than that of the bulk concentration (20). Fluorinated alcohols such as TFE and hexafluoroisopropanol have also been shown to aggregate appreciably in water-alcohol mixtures (15,32,33). These clusters have been reported to form a maximum size at a concentration of Ϸ40% (vol/vol) of TFE (32,33).…”

“…Fluorinated alcohols such as TFE and hexafluoroisopropanol have also been shown to aggregate appreciably in water-alcohol mixtures (15,32,33). These clusters have been reported to form a maximum size at a concentration of Ϸ40% (vol/vol) of TFE (32,33). At higher concentrations (Ͼ50%) the clusters diminish in size because of the increased homogeneity of the solvent.…”

Hierarchical Structures of Bone and Bioinspired Bone Tissue Engineering

“…[186] It has been shown that fluoroalcohols result in conformational change of native proteins, [187] and electrospun fibers lack typical 67nm cross-banding of native collagen. [187][188][189][190] Although collagenous bone grafts provide greater bioactivity and biocompatibility with bone tissue, thereby favoring tissue regeneration, [191,192] these biological functions depend on the unique ultrastructural axial periodicity of collagen. [188] Electrospun collagen nanofibers present poor mechanical properties and thermal stability, which result in collagen denature during the electrospinning process.…”

Molecular Self‐Recognition: Rotational Spectra of the Dimeric 2‐Fluoroethanol Conformers

“…[1,2] NMR spectroscopy, [3] X-ray diffraction, [4] circular dichroism, [5] FTIR spectroscopy [6] and molecular dynamics approaches [7] have enriched our understanding of the mechanism of the fluoroalcohol intervention in peptide binding. A detailed picture of this important process, on the other hand, is still lacking.…”