Proteins Take up Water Before Unfolding

Groot, C. C. M.; Bakker, Huib J.

doi:10.1021/acs.jpclett.6b00708

Cited by 15 publications

(22 citation statements)

References 45 publications

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“…Hence, the slowing down of the hydration water appears to scale with the number of hydrophobic CH groups contained in the caffeine/taurine molecule. This result agrees with previous studies showing that hydrophobic groups have a significantly stronger retardation effect on surrounding water molecule than hydrophilic groups [14,21,22].…”

Section: Determination Of the Slow Water Fractionsupporting

confidence: 93%

“…Both caffeine and taurine are observed to slow down the reorientational dynamics of surrounding water molecules. For other organic and biological solutes a similar slowing down of the water molecules in their hydration shells has been observed [11,17,22,23]. It is also quite generally found that in the case of dilute solution (no aggregation), the number of slow water molecules scales quite well with the size of the solute.…”

Section: Discussionsupporting

confidence: 60%

“…It is also quite generally found that in the case of dilute solution (no aggregation), the number of slow water molecules scales quite well with the size of the solute. In the case of aggregation [21] or folding [22] the number of slow water molecules per solute molecule is reduced because the hydrophobic groups are partly shielded from the interaction with water.…”

Section: Discussionmentioning

confidence: 99%

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Caffeine and taurine slow down water molecules

et al. 2019

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In this work we study the effect of caffeine and taurine on the mobility of water molecules at 298 K using femtosecond mid-infrared and dielectric relaxation spectroscopy. We observe both molecules to have a slowing down effect on the mobility of surrounding water molecules: a single caffeine molecule slows down ∼9 water molecules, a single taurine molecule slows down ∼4 water molecules. The reorientation time constant of these slow water molecules is 4-5 times longer than the reorientation time constant of 2.5 ps of water molecules in bulk liquid water.

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Section: Determination Of the Slow Water Fractionsupporting

confidence: 93%

Section: Discussionsupporting

confidence: 60%

Section: Discussionmentioning

confidence: 99%

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Caffeine and taurine slow down water molecules

et al. 2019

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“…Therefore, the thicknesses detected by QCM-A, such as 100 and 200 nm (Figs 3 , 4 and 6 ), are much larger than the actual thickness of the denatured SOD1. As proteins are denatured their structures become looser allowing them to take up more water molecules due to the increased surface area that is exposed to water [ 41 ]. Therefore, QCM-A appears to have detected an extra aqueous layer which loosely associates with the denatured SOD1 as a layer thickness.…”

Section: Resultsmentioning

confidence: 99%

Cu/Zn-superoxide dismutase forms fibrillar hydrogels in a pH-dependent manner via a water-rich extended intermediate state

et al. 2018

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Under certain conditions, amyloid-like fibrils can develop into three-dimensional networks and form hydrogels by a self-assembly process. When Cu/Zn superoxide dismutase (SOD1), an anti-oxidative enzyme, undergoes misfolding, fibrillar aggregates are formed, which are a hallmark of a certain form of familial amyotrophic lateral sclerosis (ALS). However, the issue of whether SOD1 fibrils can be assembled into hydrogels remains to be tested. Here, we show that the SOD1 polypeptides undergo hydrogelation accompanied by the formation of thioflavin T-positive fibrils at pH 3.0 and 4.0, but not at pH 5.0 where precipitates are formed. The results of viscoelastic analyses indicate that the properties of SOD1 hydrogels (2%) were similar to and slightly more fragile than a 0.25% agarose gel. In addition, monitoring by a quartz crystal microbalance with admittance analysis showed that the denaturing of immobilized SOD1 on a sensor under the hydrogelation conditions at pH 3.0 and 4.0 resulted in an increase in the effective acoustic thickness from ~3.3 nm (a folded rigid form) to ~50 and ~100 nm (an extended water-rich state), respectively. In contrast, when SOD1 was denatured under the same conditions at pH 5.0, a compact water-poor state with an effective acoustic thickness of ~10 nm was formed. The addition of physiological concentrations of NaCl to the pH 4.0 sample induced a further extension of the SOD1 with larger amounts of water molecules (with an effective acoustic thickness of ~200 nm) but suppressed hydrogel formation. These results suggest that different denatured intermediate states of the protein before self-assembly play a major role in determining the characteristics of the resulting aggregates and that a conformational change to a suitable level of extended water-rich intermediate state before and/or during intermolecular assembling is required for fibrillation and hydrogelation in the case of globular proteins.

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“…Considering that the currently used acid concentration was 0.5 mol L −1 , the molecular weight reductions observed in the present study suggest that the temperature has a more pronounced influence than acid concentration. A possible reason for this may be that higher hydrolysis temperatures assist in protein unfolding and increase molecular mobility allowing a solvent penetration in intraparticle regions, thereby weakening inter‐ and intramolecular bonds and protein interactions . However, some larger insoluble microalgae protein‐rich particles remained in the loading cell as indicated by the dark color even after acid hydrolysis at 85 °C for 4 h (Fig.…”

Section: Resultsmentioning

confidence: 99%

An erosion‐type hydrolysis behavior of insoluble protein fraction from Chlorella protothecoides

et al. 2019

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BACKGROUND: Acid-induced hydrolysis of proteins has been used to improve the solubility and functional properties of various proteins, and could be a promising tool to facilitate the use of currently underutilized insoluble microalgae protein-rich fractions in food applications. However, the results of a prior study showed an unusual resistance of an insoluble microalgae protein-rich fraction to acid hydrolysis at room temperature.RESULTS: In the present study, the insoluble protein-rich fraction extracted from microalgae Chlorella prothothecoides was treated with 0.5 mol L −1 hydrochloric acid at 25, 45, 65 or 85 ∘ C for 0-4 h. The results showed that hydrolysis of the fraction at 85 ∘ C for 4 h led to decreases in the amount of insoluble protein-rich aggregates and the formation of fragments with a lower molecular weight, as well as an increase in protein solubility by approximately 40%. Nevertheless, some aggregated insoluble protein-rich particles remained, even after hydrolysis at 85 ∘ C for 4 h.CONCLUSION: The higher temperature improved the efficiency of the acid hydrolysis of the insoluble protein fraction from microalgae Chlorella prothothecoides, which is highly acid-resistant. Overall, an erosion-based mechanism was suggested for the acid hydrolysis of insoluble microalgae protein fraction.

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Proteins Take up Water Before Unfolding

Cited by 15 publications

References 45 publications

Caffeine and taurine slow down water molecules

Caffeine and taurine slow down water molecules

Cu/Zn-superoxide dismutase forms fibrillar hydrogels in a pH-dependent manner via a water-rich extended intermediate state

An erosion‐type hydrolysis behavior of insoluble protein fraction from Chlorella protothecoides

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