Compressibility of globular proteins in water at 25.degree.C

Abstract

The adiabatic compressibility, ft, of 14 globular proteins in water was determined at 25 °C by sound velocity measurements with a "sing around pulse method". All proteins studied showed positive compressibilities, suggesting a large internal compressibility for the proteins. To discuss the data obtained from the viewpoint of void and hydration of the proteins, a correlation was examined between ft and some molecular parameters such as the partial specific volume, hydrophobicity, and polarity of the proteins. Further, an attempt was made to estimate separately the contributions of void and hydration to the compressibility of proteins. These results revealed that a large negative compression of the void by pressure compensates a positive compression due to the hydration of the protein, resulting in a small positive value for ft. Such a large compressibility of the void supports the proposition that the increase in compressibility of the protein by denaturation is due to the high local concentration of nonpolar groups of denatured protein. From the obtained adiabatic compressibility data, the isothermal compressibility of six proteins was estimated by using the thermal expansion coefficient and the heat capacity data for the proteins.

Hydrogen Bond Network of Water around Protein Investigated with Terahertz and Infrared Spectroscopy

“…Water molecules interacting with protein exhibit some anomalous thermodynamical properties, such as freezing temperature (1), adiabatic compressibility (2), and specific heat capacity (3). It is widely believed that these peculiar characteristics of water in the vicinity of proteins provide biological functionalities to the protein molecule (4,5).…”

Solvent effects on the molecular structures of crude gliadins as revealed by density and ultrasound velocity measurements

“…To approximate the properties of the ideal isolated protein molecules, which have no intermolecular interactions, the apparent specific volume is extrapolated to the limit of zero protein concentration and the partial specific volume of the protein molecule in the solution, o v , is obtained as equation 3 (Gekko and Noguchi, 1974;Millero et al, 1976;Gekko and Noguchi, 1979;Gekko and Hasegawa, 1986;Gekko and Hasegawa, 1989;Gekko and Yamagami, 1991;Kamiyama and Gekko, 2000;Gekko et al, 2003;Gekko et al, 2004;Chalikian et al, 1993;Blandamer et al, 2001;Taulier et al, 2005).…”

“…For macromolecules such as protein molecules To RT M β is small and can be neglected (Stillinger, 1973;Kharakoz, 1992;Chalikian, 2003). (Gekko and Noguchi, 1979;Gekko and Hasegawa, 1986;Gekko and Hasegawa, 1989;Gekko and Yamagami, 1991;Kharakoz, 1992;Chalikian, 1998;Chalikian and Breslauer, 1998;Murphy et al, 1998;Chalikian, 2001;Gekko, 2002;Valdez et al, 2001;Chalikian, 2003;Gekko et al, 2003;Gekko et al, 2004;Bano and Marek, 2006 Taulier and Chalikian, 2002;Mori et al, 2006). …”

“…Thus, from equation 7, the value of β S is obtained as (Gekko and Noguchi, 1974;Gekko and Noguchi, 1979;Sarvazyan et al, 1979;Chavez et al, 1985;Gekko and Hasegawa, 1986;Sarvazyan, 1991;Chalikian et al, 1992;Kharakoz and Sarvazyan, 1993;Chalikian et al, 1994a;McClements, 1995;Tikhonov et al, 1995;Paci and Marchi, 1996;Hianik et al, 1997;Pinfield and Povey, 1997;Povey, 1997;Heremans and Smeller, 1998;Povey, 1998;Burakowski and Gliński, 2007;Raman et al, 2007).…”

“…According to the definition of compressibility coefficient (equation 7), the partial specific adiabatic compressibility coefficient, o S β , is expressed as: Thus, equation 15 gives (Gekko and Noguchi, 1974;Gekko and Noguchi, 1979;Gekko and Hasegawa, 1986;Gekko and Hasegawa, 1989;Gekko and Yamagami, 1991;Paci and Marchi, 1996;Kamiyama and Gekko, 2000;Gekko et al, 2003;Gekko et al, 2004) …”