Hydration mobility in peptide structures

Chirgadze, Yu. N.; Ovsepyan, A. M.

doi:10.1002/bip.1972.360111017

Cited by 30 publications

(6 citation statements)

References 6 publications

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“…(1) The time-average conformation of lysozyme in the partially hydrated powder is closely similar to and possibly identical with the conformation in solution, as shown by measurements sensitive to conformation, for example, the following: the CD spectrum of the dry film is similar to the CD spectrum in solution (Chirgadze & Ovsepyan, 1972); Tempone spin-spin interaction is invariant to hydration (Rupley et al, 1980); enzymatic activity is observed at 0.2 h (Rupley et al, 1980); the thermal stability of lysozyme increases sharply with decrease in hydration below 0.3 h (Fujita & Noda, 1978). Thus, the high hydration conformation of lysozyme is frozen in as the hydration level is reduced.…”

Section: ~0mentioning

confidence: 73%

Hydrogen exchange of lysozyme powders. Hydration dependence of internal motions

Schinkel¹,

Downer²,

Rupley³

1985

Biochemistry

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The rate of exchange of the labile hydrogens of lysozyme was measured by out-exchange of tritium from the protein in solution and from powder samples of varied hydration level, for pH 2, 3, 5, 7, and 10 at 25 degrees C. The dependence of exchange of powder samples on the level of hydration was the same for all pHs. Exchange increased strongly with increased hydration until reaching a rate of exchange that is constant above 0.15 g of H2O/g of protein (120 mol of H2O/mol of protein). This hydration level corresponds to coverage of less than half the protein surface with a monolayer of water. No additional hydrogen exchange was observed for protein powders with higher water content. Considered in conjunction with other lysozyme hydration data [Rupley, J. A., Gratton, E., & Careri, G. (1983) Trends Biochem. Sci. (Pers. Ed.) 8, 18-22], this observation indicates that internal protein dynamics are not strongly coupled to surface properties. The use of powder samples offers control of water activity through regulation of water vapor pressure. The dependence of the exchange rate on water activity was about fourth order. The order was pH independent and was constant from 114 to 8 mol of hydrogen remaining unexchanged/mol of lysozyme. These results indicate that the rate-determining step for protein hydrogen exchange is similar for all backbone amides and involves few water molecules. Powder samples were hydrated either by isopiestic equilibration, with a half-time for hydration of about 1 h, or by addition of solvent to rapidly reach final hydration. Samples hydrated slowly by isopiestic equilibration exhibited more exchange than was observed for samples of the same water content that had been hydrated rapidly by solvent addition. This difference can be explained by salt and pH effects on the nearly dry protein. Such effects would be expected to contribute more strongly during the isopiestic equilibration process. Solution hydrogen exchange measurements made for comparison with the powder measurements are in good agreement with published data. Rank order was proven the same for all pHs by solution pH jump experiments. The effect of ionic strength on hydrogen exchange was examined at pH 2 and pH 5 for protein solutions containing up to 1.0 M added salt. The influence of ionic strength was similar for both pHs and was complex in that the rate increased, but not monotonically, with increased ionic strength.

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Section: ~0mentioning

confidence: 73%

Hydrogen exchange of lysozyme powders. Hydration dependence of internal motions

Schinkel¹,

Downer²,

Rupley³

1985

Biochemistry

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“…Zaks and Klibanov studied the cosolvent effect on enzyme catalysis (54, 55) and suggested that some of the hydration water acts as "lubricant" or "plasticizer" that provides the enzyme with sufficient conformational flexibility needed for catalysis. This lubrication is attributed to the ability of water molecules to form hydrogen bonding with the functional groups on the polypeptide chain, and thereby enables the conformational mobility, i.e., the sliding of adjacent polypeptide segments (56). This water species is distinct from that tightly-bound to charged groups which are immobilized by electrostriction (40).…”

Section: Discussionmentioning

confidence: 99%

Viscous cosolvent effect on the ultrasonic absorption of bovine serum albumin

Almagor¹,

Yedgar²,

Gavish³

1992

Biophysical Journal

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Protein-ligand binding and enzyme activity have been shown to be regulated by solvent viscosity, induced by the addition of viscous cosolvents. This was indirectly interpreted as an effect on protein dynamics. However, viscous cosolvents might affect dynamic, e.g., viscosity, as well as thermodynamic properties of the solution, e.g., activity of solution components. This work was undertaken to examine the effect of viscous cosolvent on the structural dynamics of proteins and its correlation with dynamic and thermodynamic solution properties. For this purpose we studied the effect of viscous cosolvent on the specific ultrasonic absorption, delta mu, of bovine serum albumin, at pH = 7.0 and at 21 degrees C, and frequency range of 3-4 MHz. Ultrasonic absorption (UA) directly probes protein dynamics related to energy dissipation processes. It was found that the addition of sucrose, glycerol, or ethylene glycol increased the BSA delta mu. This increase correlates well with the solvent viscosity, but not with the cosolvent mass concentration, activity of the solvent components, dielectric constant, or the hydration of charged groups. On the grounds of these results and previously reported findings, as well as theoretical considerations, we propose the following mechanism for the solvent viscosity effect on the protein structural fluctuations, reflected in the UA: increased solvent viscosity alters the frequency spectrum of the polypeptide chain movements; attenuating the fast (small amplitude) movements, and enhancing the slow (large amplitude) ones. This modulates the interaction strength between the polypeptide and water species that "lubricates" the chain's movements, leading to larger protein-volume fluctuation and higher ultrasonic absorption. This study demonstrates that solvent viscosity is a regulator of protein structural fluctuations.

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“…However, until now, precise protein structural transitions promoted by desiccation as well as the reversibility of these processes are not often quantified [34,[40][41][42][43]. The present analysis displays that drying α-chymotrypsin solutions or α-chymotrypsin-montmorillonite suspensions promoted a similar unfolding of at least two different β-structures either in anhydrous and hydrated domains.…”

Section: Discussionmentioning

confidence: 94%