Nonideality of Water-Hexafluoropropanol Mixtures as Studied by X-Ray Small Angle Scattering

Kuprin, Sergei; Gräslund, and Astrid; Ehrenberg, Anders; Koch, Michel H. J.

doi:10.1006/bbrc.1995.2889

Cited by 61 publications

(69 citation statements)

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“…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.…”

Section: Construction Of Solvation Energy Of Relaxationsupporting

confidence: 88%

“…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).…”

Section: Construction Of Solvation Energy Of Relaxationmentioning

confidence: 95%

“…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.…”

Section: Construction Of Solvation Energy Of Relaxationmentioning

confidence: 99%

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

Othon

Kwon

Lin

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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Protein structural integrity and flexibility are intimately tied to solvation. Here, we examine the effect that changes in bulk and local solvent properties have on protein structure and stability. We observe the change in solvation of an unfolding of the protein model, melittin, in the presence of a denaturant, trifluoroethanol. The peptide system displays a well defined transition in that the tetramer unfolds without disrupting the secondary or tertiary structure. In the absence of local structural perturbation, we are able to reveal exclusively the role of solvation dynamics in protein structure stabilization and the (un)folding pathway. A sudden retardation in solvent dynamics, which is coupled to the change in protein structure, is observed at a critical trifluoroethanol concentration. The large amplitude conformational changes are regulated by the local solvent hydrophobicity and bulk solvent viscosity.fluoresence spectroscopy ͉ preferential solvation ͉ protein folding ͉ ultrafast hydration

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Section: Construction Of Solvation Energy Of Relaxationsupporting

confidence: 88%

Section: Construction Of Solvation Energy Of Relaxationmentioning

confidence: 95%

Section: Construction Of Solvation Energy Of Relaxationmentioning

confidence: 99%

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

Othon

Kwon

Lin

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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“…The effect of TFE is not clearly understood. Besides its different dielectric constant and hydrogen bonding properties as compared with pure water (Llinds & Klein, 1975;Nelson & Kallenbach, 1986), the heterogeneity of TFE-water mixtures resulting from the immiscibility of the two components could be very important, as recently detected by small-angle X-ray scattering measurements (Kuprin et al, 1995). This study suggest that alcohols (specially fluorinated ones) behave as other amphiphilic molecules, and at relatively high concentrations can form some kind of pool of extended structures.…”

Section: G E Y T V D V a D K G Y T L N I K F A G Dmentioning

confidence: 58%

Conformational analysis of peptides corresponding to all the secondary structure elements of protein L B1 domain: Secondary structure propensities are not conserved in proteins with the same fold

1997

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The solution conformation of three peptides corresponding to the two P-hairpins and the a-helix of the protein L B1 domain have been analyzed by circular dichroism (CD) and nuclear magnetic resonance spectroscopy (NMR). In aqueous solution, the three peptides show low populations of native and non-native locally folded structures, but no well-defined hairpin or helix structures are formed. In 30% aqueous trifluoroethanol (TFE), the peptide corresponding to the a-helix adopts a high populated helical conformation three residues longer than in the protein. The hairpin peptides aggregate in TFE, and no significant conformational change occurs in the NMR observable fraction of molecules. These results indicate that the helical peptide has a significant intrinsic tendency to adopt its native structure and that the hairpin sequences seem to be selected as non-helical. This suggests that these sequences favor the structure finally attained in the protein, but the contribution of the local interactions alone is not enough to drive the formation of a detectable population of native secondary structures. This pattern of secondary structure tendencies is different to those observed in two structurally related proteins: ubiquitin and the protein G B 1 domain. The only common feature is a certain propensity of the helical segments to form the native structure. These results indicate that for a protein to fold, there is no need for large native-like secondary structure propensities, although a minimum tendency to avoid non-native structures and to favor native ones could be required.Keywords: peptide structure; protein folding; protein G; protein L; secondary structure; ubiquitin Experimental and theoretical analysis of protein folding suggest that there is an energy gap between the native and the other possible conformations of a protein (Anfinsen, 1973;Bryngelson et al., 1995), and that this is a necessary and sufficient condition for folding (Sali et al., 1994). The occurrence of this gap requires the set of interactions to be stronger in the native structure than in any of the possible non-native conformations. There are two types of interactions: local, which occur between amino acids close in the primary sequence, and non-local (Dill, 1990). Local interactions participate to define secondary structure, while non-local Laboratory,

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“…The evidence for microheterogeneity in HFIP-water mixtures comes primarily from small-angle X-ray scattering (SAXS), 10 wide-angle X-ray scattering (WAXS), NMR and mass spectrometry (MS) studies. 11 In the study of Kuprin et al, 10 a sharp turn at 30% HFIP and another inflecting point at about 70% HFIP were found in the average scattering intensity dependent plot.…”

mentioning

confidence: 99%