Molecular thermodynamics of heat‐induced protein unfolding in aqueous media

Cioci, Federico; Lavecchia, Roberto

doi:10.1002/aic.690430225

Cited by 19 publications

(18 citation statements)

References 63 publications

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“…In the case of ethanol addition, both ␣ and ␥ decrease, leading to a reduced driving force for hydrophobic aggregation. This general picture is consistent with experimental data on additive effects on protein stability (58)(59)(60).…”

Section: (D) Shown Is the Ratio P N͞supporting

confidence: 80%

“…Addition of ethanol has similar effects, but in the opposite direction. In both cases, changes in the asymptotic values (Ϸ5 dynes͞cm for 2 M NaCl and Ϸ30 dynes͞cm for 40 mol% ethanol solution) are consistent with experimental data on vapor-liquid surface tensions of their aqueous solutions (57,58). Further, we find that the EgelstaffWidom lengthscale, ␥ ϱ b , increases somewhat with salt addition and decreases with ethanol addition, consistent with our calculations.…”

Section: (D) Shown Is the Ratio P N͞supporting

confidence: 80%

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Hydrophobic hydration from small to large lengthscales: Understanding and manipulating the crossover

Rajamani

Truskett

Garde

2005

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

276

329

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Small and large hydrophobic solutes exhibit remarkably different hydration thermodynamics. Small solutes are accommodated in water with minor perturbations to water structure, and their hydration is captured accurately by theories that describe density fluctuations in pure water. In contrast, hydration of large solutes is accompanied by dewetting of their surfaces and requires a macroscopic thermodynamic description. A unified theoretical description of these lengthscale dependencies was presented by Lum, Chandler, and Weeks [(1999) J. Phys. Chem. B 103, 4570 -4577]. Here, we use molecular simulations to study lengthscale-dependent hydrophobic hydration under various thermodynamic conditions. We show that the hydration of small and large solutes displays disparate dependencies on thermodynamic variables, including pressure, temperature, and additive concentration. Understanding these dependencies allows manipulation of the small-tolarge crossover lengthscale, which is nanoscopic under ambient conditions. Specifically, applying hydrostatic tension or adding ethanol decreases the crossover length to molecular sizes, making it accessible to atomistic simulations. With detailed temperaturedependent studies, we further demonstrate that hydration thermodynamics changes gradually from entropic to enthalpic near the crossover. The nanoscopic lengthscale of the crossover and its sensitivity to thermodynamic variables imply that quantitative modeling of biomolecular self-assembly in aqueous solutions requires elements of both molecular and macroscopic hydration physics. We also show that the small-to-large crossover is directly related to the Egelstaff-Widom lengthscale, the product of surface tension and isothermal compressibility, which is another fundamental lengthscale in liquids. molecular dynamics ͉ salt and additive effects ͉ density fluctuations ͉ nonpolar solvation B iological self-assembly processes in aqueous solutions are driven by water-mediated interactions between constituents taking part in the assembly. Of these, hydrophobic interactions have received particular attention because of their relevance to protein folding and interactions, micelle and membrane formation, and molecular recognition (1-5). Theoretical work in this direction has been focused on the modeling of primitive hydrophobic phenomena, such as hydration and association of small hydrophobic particles in water (6-13). However, biological assembly occurs over a spectrum of lengthscales from that of an amino acid to proteins and larger. Naturally, fundamental understanding of the lengthscale dependence of hydration and association of hydrophobic solutes in water will be relevant to the quantitative modeling of realistic macromolecular processes (14,15).Small hydrophobic solutes can be accommodated into the open hydrogen-bonded network of liquid water without significant perturbations. Indeed, theories that model density fluctuations over small lengthscales in pure water provide a quantitative description of the hydration thermodynamics of small...

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Section: (D) Shown Is the Ratio P N͞supporting

confidence: 80%

Section: (D) Shown Is the Ratio P N͞supporting

confidence: 80%

Hydrophobic hydration from small to large lengthscales: Understanding and manipulating the crossover

Rajamani

Truskett

Garde

2005

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

276

329

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“…The laser beam is attenuated through a series of neutral density filters and defocused using a long focal length lens to make the irradiance delivered to the sample approximately 15 mW/cm 2 . This relatively low-irradiance delivery is used to ensure that any protein unfolding is not due to thermal effects from the absorbed light [43] since heat is well known to denature proteins [44]. The solutions were exposed to increasing total energy doses of 0, 4.5, 13.5 and 27 J/cm 2 .…”

Section: Irradiationmentioning

confidence: 99%

Photoinduced partial unfolding of tubulin bound to meso‐tetrakis(sulfonatophenyl) porphyrin leads to inhibition of microtubule formation in vitro

McMicken

Thomas

Brancaleon

2013

Journal of Biophotonics

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The irradiation of the complex formed by meso-tetrakis (sulfonatophenyl) porphyrin (TSPP) and tubulin was investigated as well as its effects on the structure and function of the protein. We have used tubulin as a model target to investigate whether photoactive ligands docked to the protein can affect the structure and function of the protein upon exposure to visible light. We observed that laser irradiation prompts bleaching of the porphyrin which is accompanied by a sharp decrease (∼2 ns) in the average fluorescence lifetime of the protein and a change in the dichroic spectrum consistent with a decrease of helical structure. The result indicated the photoinduced partial unfolding of tubulin. We also observed that such partial conformational change inhibits the formation of microtubules in vitro. We investigated whether photosensitization of reactive oxygen species was responsible for these effects. Even upon removal of O2 the protein still undergoes conformational changes indicating that irradiation of the bound porphyrin does not require the presence of O2 to prompt conformational and functional effects opening the possibility that other mechanisms (e.g., charge transfer) are responsible for the photoinduced mechanism.

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“…These results suggest that sorbitol is preferentially excluded from the air-water surface, whereas glycerol is preferentially accumulated, i.e., it is surface active (Cioci, 1996). Air is relatively hydrophobic, hence we would expect sorbitol to be preferentially excluded from any hydrophobic patches on a globular protein's surface, whereas glycerol would be preferentially accumulated around these groups (Cioci, 1996;Cioci & Lavecchia, 1997). The surface of a globular protein is highly heterogeneous, consisting of functional groups of differing polarity, shape and size.…”

Section: Surface Tension Measurementsmentioning

confidence: 83%

“…Previous authors have indicated that surface tension measurements made at an air-cosolvent/solvent solution interface are correlated to the conformational stability of globular proteins (Cioci, 1996;Cioci & Lavecchia, 1997, 1998. A linear relationship has been observed between the thermal denaturation temperature (T m ) of some globular proteins and the surface tension of the cosolvent solutions in which they are dissolved, i.e., cosolvents that increase the surface tension tend to increase the T m of globular proteins (Cioci, 1996).…”

Section: Surface Tension Measurementsmentioning

confidence: 92%

Impact of cosolvents (polyols) on globular protein functionality: Ultrasonic velocity, density, surface tension and solubility study

2008

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Molecular thermodynamics of heat‐induced protein unfolding in aqueous media

Cited by 19 publications

References 63 publications

Hydrophobic hydration from small to large lengthscales: Understanding and manipulating the crossover

Hydrophobic hydration from small to large lengthscales: Understanding and manipulating the crossover

Photoinduced partial unfolding of tubulin bound to meso‐tetrakis(sulfonatophenyl) porphyrin leads to inhibition of microtubule formation in vitro

Impact of cosolvents (polyols) on globular protein functionality: Ultrasonic velocity, density, surface tension and solubility study

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