Relation between Molal Volumes and Molal Compressibilities from the Viewpoint of the Scaled-Particle Theory. Prediction of the Apparent Molal Compressibilities of Transfer

1999

J. Am. Chem. Soc.

This paper reports the first characterization of the hydration properties of some amino acids and oligoglycines, low molecular weight analogues of proteins, in D2O. Specifically, the partial molar volumes, V°, and adiabatic compressibilities, K°S, of five α-amino acids and five oligoglycines have been determined in D2O at 25 °C. The resulting data have been used to estimate the volume and compressibility contributions of the component nonpolar (methylene group), polar (peptide group), and charged (oppositely charged amino and carboxyl terminal groups) chemical groups. It was found that the volume and compressibility contributions of these charged, polar, and nonpolar groups in D2O are “measurably” distinct from those in H2O. This distinction, in principle, may allow one to develop a method by which differential volumetric measurements of proteins in D2O and H2O can be used to gain insight into the nature of the solvent-exposed protein groups in the absence of detailed structural information.

Section: Discussionsupporting

confidence: 86%

Section: Discussionsupporting

confidence: 85%

Partial Molar Volumes and Adiabatic Compressibilities of a Series of Aliphatic Amino Acids and Oligoglycines in D₂O

Likhodi

1999

J. Am. Chem. Soc.

“…We used eqs and to compute a change in the cavity volume of a spherical particle with a diameter ranging from 4 to 10 Å accompanying its transfer from water to 2, 4, 6, and 8 M urea. In our analysis, we employed the hard-sphere diameter of water of 2.74 Å , and the diameter of urea of 4.41 Å. The latter has been evaluated from SPT-based calculations of changes in volume and compressibility accompanying the water-to-urea transfer of alkali-metal halides. , The coefficients of isothermal compressibility, β T ,0 , of urea solutions required in eq are not known.…”

Section: Thermodynamics Of Solvation In Binary Mixturesmentioning

confidence: 99%

“…In our analysis, we employed the hard-sphere diameter of water of 2.74 Å , and the diameter of urea of 4.41 Å. The latter has been evaluated from SPT-based calculations of changes in volume and compressibility accompanying the water-to-urea transfer of alkali-metal halides. , The coefficients of isothermal compressibility, β T ,0 , of urea solutions required in eq are not known. Instead, we used the coefficients of adiabatic compressibility, β S ,0 , which was determined from our densimetric and ultrasonic velocimetric measurements.…”

Section: Thermodynamics Of Solvation In Binary Mixturesmentioning

confidence: 99%

Volumetric Properties of Solvation in Binary Solvents

Lee

2009

J. Phys. Chem. B

The volumetric properties of solutes, including partial molar volume, compressibility, and expansibility, are determined by and, therefore, sensitive to the entire spectrum of solute-solvent interactions. However, applications of volumetric measurements to the study of solvation of solutes in binary solvents consisting of the principal solvent and a cosolvent are almost nonexistent. This deficiency partially reflects the lack of an adequate theoretical framework to rationalize the measured volumetric observables in terms of solute-principal solvent and solute-cosolvent interactions. To address this deficiency, we present in this work a simple statistical thermodynamic model describing solute thermodynamics in binary solvents. Based on the model, we derive relationships that link the partial molar volumetric properties of solutes with the extent and intensity of interactions of a solute with the principal solvent and the cosolvent. If the approximation of homogeneous solvation is introduced, the derived formalism can be simplified to a form that can be readily employed for practical treatment of experimental volumetric data on small solutes and/or individual atomic groups. As an example, we use this simplified formalism to rationalize the volumetric properties of the zwitterionic amino acid glycine in concentrated urea solutions. In general, the theoretical development presented in this work opens the way for systematic applications of volumetric measurements to quantitative characterization of solute-solvent interactions in complex solvents.

“…These and other differences in physical properties of light and heavy water render them unequal as solvents. Consequently, the thermodynamics of solvation of various atomic groups in light and heavy water is considerably different, which is reflected in corresponding changes in Gibbs free energy, enthalpy, entropy, heat capacity, volume, compressibility, and other thermodynamic characteristics upon transfer of various substances from H 2 O to D 2 O. − …”

Section: Introductionmentioning

confidence: 99%

Differential Hydration of α,ω-Aminocarboxylic Acids in D₂O and H₂O

and

2000

J. Am. Chem. Soc.

We report the relative molar sound velocity increments, [U], partial molar volumes, V°, expansibilities, E°, and adiabatic compressibilities, K°S, for a homologous series of eight α,ω-aminocarboxylic acids in D2O solution within the temperature range of 18−55 °C. We use the resulting data to estimate the volume, expansibility, and adiabatic compressibility contributions of the component aliphatic (methylene groups) and charged (oppositely charged amino and carboxyl termini) chemical groups. We compare these group contributions with similar group contributions for the same set of α,ω-aminocarboxylic acids in H2O (Chalikian, T. V.; Sarvazyan, A. P.; Breslauer, K. J. J. Phys. Chem. 1993, 97, 13017−13026). We use these data to characterize quantitatively the differential hydration properties of charged and hydrophobic groups in D2O and H2O. Taken together, our results suggest that the hydration properties of hydrophobic and charged groups in D2O, as reflected in their volume, expansibility, and compressibility contributions, are measurably distinct from those in H2O. Significantly, these volumetric characteristics of the solute hydration differ not only in their absolute values but also in their temperature dependences. Such characteristics should prove useful in developing a better understanding of the role of differential D2O/H2O hydration in modulating thermal and thermodynamic stability of proteins. In addition, these results represent a further step in building up an empirical database of differential volumetric parameters of protein functional groups in D2O and H2O. Such a database is required for developing a methodology in which differential volumetric measurements in D2O and H2O can be employed to gain insight into the amount and chemical nature of solvent-exposed protein groups in the absence of structural information.