FURTHER STUDIES ON THE SORPTION OF H2O AND D2O VAPORS BY LYSOZYME AND THE DEUTERIUM—HYDROGEN EXCHANGE EFFECT1

Hnojewyj, Wasyl S.; Reyerson, L. H.

doi:10.1021/j100827a007

Cited by 41 publications

(27 citation statements)

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“…Equation (1) shows that the upswing in water uptake, as dominated by the second term, is expected to be temperature-independent when plotted versus the relative pressure P / P 0 [6]. Isotherm data taken above room temperature indeed confirm this expectation [21, 24]. However, this is no longer the case in lysozyme below 10°C.…”

Section: Resultsmentioning

confidence: 99%

Temperature dependence of lysozyme hydration and the role of elastic energy

et al. 2011

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Water plays critical roles in protein dynamics and functions. However, the most basic property of hydration—the water sorption isotherm—remains inadequately understood. Surface adsorption is the commonly adopted picture of hydration. Since it does not account for changes in the conformational entropy of proteins, it is difficult to explain why protein dynamics and activity change upon hydration. The solution picture of hydration provides an alternative approach to describe the thermodynamics of hydration. Here, the flexibility of proteins could influence the hydration level through the change of elastic energy upon hydration. Using nuclear magnetic resonance to measure the isotherms of lysozyme in situ between 18 and 2°C, the present work provides evidence that the part of water uptake associated with the onset of protein function is significantly reduced below 8°C. Quantitative analysis shows that such reduction is directly related to the reduction of protein flexibility and enhanced cost in elastic energy upon hydration at lower temperature. The elastic property derived from the water isotherm agrees with direct mechanical measurements, providing independent support for the solution model. This result also implies that water adsorption at charged and polar groups occurring at low vapor pressure, which is known for softening the protein, is crucial for the later stage of water uptake, leading to the activation of protein dynamics. The present work sheds light on the mutual influence of protein flexibility and hydration, providing the basis for understanding the role of hydration on protein dynamics.

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Section: Resultsmentioning

confidence: 99%

Temperature dependence of lysozyme hydration and the role of elastic energy

et al. 2011

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“…The samples were then equilibrated at 5°C, 0% RH prior to exposure to humidity levels of 11, 23, 33, 43, 59, and 75% RH over H 2 O. Previous studies have shown no significant isotope effect on water sorption in lyophilized proteins 36 . Each humidity level was maintained until the signal was constant, requiring ~6.5 h at low RH and ~2 h at higher RH.…”

Section: Methodsmentioning

confidence: 99%

Localized Hydration in Lyophilized Myoglobin by Hydrogen–Deuterium Exchange Mass Spectrometry. 1. Exchange Mapping

2012

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The local effects of hydration on myoglobin (Mb) in solid matrices containing mannitol or sucrose (1:1 w/w, protein:additive) were mapped using hydrogen-deuterium exchange with mass spectrometric analysis (HDX-MS) at 5°C and compared to solution controls. Solid powders were exposed to D2O(g) at controlled activity (aw) followed by reconstitution and analysis of the intact protein and peptides produced by pepsin digestion. HDX varied with matrix type, aw, and position along the protein backbone. HDX was less in sucrose matrices than in mannitol matrices at all aw while the difference in solution was negligible. Differences in HDX in the two matrices were detectable despite similarities in their bulk water content. The extent of exchange in solids is proposed as a measure of the hydration of exchangeable amide groups, as well as protein conformation and dynamics; pepsin digestion allows these effects to be mapped with peptide-level resolution.

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“…The hydration enthalpies were calculated from the temperature dependence of the water vapor pressure in the range 25-40 • C. Bone studied the water sorption by lysozyme in the range 1.5-19% (g g −1 ) [8]. Calculations were done using the temperature dependence of the water vapor pressure in the range 6-46 • C. From the temperature dependence of the water sorption isotherms in the range 17-57 • C, Hnojewyj and Reyerson calculated differential heats of water sorption [9]. The most important assumption of this method is that the hydration enthalpy does not depend on the temperature.…”

Section: Introductionmentioning

confidence: 99%

“…These enthalpies [6][7][8][9][10][11][12][13][14] (estimated from the temperature dependencies of water sorption and the calorimetrically measured heat effects) contain total information on the binary water-enzyme systems including the corresponding conformational changes in the enzyme structure and glass transition. However, no attempt has been undertaken to estimate simultaneously the enzyme and water contributions to the enthalpy of binary enzyme-water systems in the entire range of water contents.…”

Section: Introductionmentioning

confidence: 99%