Volumetric properties of aqueous solutions of bovine serum albumin, human serum albumin, and human hemoglobin

Abstract

In order to take into account the Fermi distribution function a t finite T for the number of occupied states in eq 8 and 9, it is useful to divide the integral eq 5 into three parts:The first integral gives the number of occupied states for the temperature equal to 0 K. The second integral represents the occupied states above E F and the third the vacant states below EF. SinceflE -EF) andf(EF -E) decay quickly with increasing values of IE -EFI, one can approximate the second and third integral by developing D(E) in a power series around D(EF).with z = E -EF/(kT) and the minus sign valid for the third integral.Introducing the new parameter z, the difference between the second and third integral AZ is -k T dzOne sees that by inserting the series of eq A2 into eq A3 all terms cancel except those of the second term of the series:The last integral has the value 0.8225'' and replacing dz by dE, one obtains as the final approximationThe integral over all occupied states in an electronic energy band, Z(EF) of eq 5 , can therefore be approximated by Registry No. Graphite, 7782-42-5.Proteinsolvent and protein-protein interactions in aqueous solutions are interpreted from calculated partial specific volumes (&O), adiabatic compressibilities (&O). and expansibilities (&O) obtained from high-precision density and sound velocity measurements at 20,25, 30, 35, and 40 OC. The results provide some information about the structural and dynamic features of these proteins and show a greater dependence of volumetric data on hydrophobicity than on any other protein characteristic. Hemoglobin has a larger content of apolar amino acids in a quaternary structure and this is reflected by larger changes in dVo, &.so, and deo with temperature, relative to the serum albumins which have fewer apolar amino acids and a tertiary structure. Subtle differences between the globular structure of BSA and HSA are revealed from compressibility and expansibility data which not only support some previous observations but also provide new information about the surface polarity and distribution of hydrophobicity within these molecules. A slight but systematic concentration dependence of &, $J~,~, and is observed in this temperature range which is interpreted in terms of protein dynamics. It is argued that, with increasing temperature, microunfolding of the protein molecule increases the probability of exposing some of the buried apolar residues to the solvent, thereby altering the surface hydration. The mechanism of solutesolute interactions thus changes as the hydration shells of interacting protein molecules begin to overlap. IntroductionOne convenient way to study intermolecular interactions is by thermodynamic methods. A number of studies of protein solutions

Pressure dependence of the apparent specific volume of bovine serum albumin: Insight into the difference between isothermal and adiabatic compressibilities

“…The β T values calculated from the slopes by least-squares regression analysis are listed in Table 1 with the v values at atmospheric pressure. These v values differ slightly from the reported partial specific volumes at infinite dilution [6,7,21] because the protein concentration dependence of v was neglected in the present study. Evidently, the observed β T values involve large experimental errors (0.78-1.62 × 10 − 11 Pa − 1 ) compared with those (0.1-0.5× 10 − 11 Pa − 1 ) of β s values [5].…”

“…(6). For BSA in water, α was determined to be 5.04 × 10 − 4 K − 1 from the temperature dependence of v over 5-40°C (Table 1), which is very close to the value (4.97 × 10 − 4 K − 1 ) reported previously [5,7].…”

“…On the other hand, the β s value can be more easily and accurately determined by measuring the sound velocity (U) and density (d) using the NewtonLaplace equation: β s = 1/dU 2 . Therefore, the β s values of many proteins have been measured by this method and widely used for investigating the hydration state, compactness or flexibility (volume fluctuation), conformational change, and structure-function relationship of proteins [2][3][4][5][6][7][8][9][10][11][12].…”

The Hydration of Globular Proteins as Derived from Volume and Compressibility Measurements: Cross Correlating Thermodynamic and Structural Data

“…The concentrations of the remaining proteins were determined spectrophotometrically using the following specific extinction coefficients: bovine serum albumin, e278 = 0.658 lg −1 cm −1 (Noelken & Timasheff, 1967); hemoglobin, e278 = 1.873 lg −1 cm −1 (Iqball & Verrall, 1987); ovalbumin, e280 = 0.750 lg −1 cm −1 (Katz & Miller, 1971); a-chymotrypsinogen A, e282 = 1.97 lg −1 cm −1 (Jackson & Brandts, 1970); a-chymotrypsin, e280 = 2.00 lg −1 cm −1 (Privalov & Khechinashvili, 1974); b-lactoglobulin, e278 = 0.960 lg −1 cm −1 (Townend et al, 1960); myoglobin, e409 = 8.99 lg −1 cm −1 (Crumpton & Polson, 1965); a-lactalbumin, e280 = 2.09 lg −1 cm −1 (Wetlaufer, 1967); lysozyme, e281.5 = 2.635 lg −1 cm −1 (Sophianopulos et al, 1962); cytochrome c, e409 = 8.56 lg −1 cm −1 (Robinson et al, 1983). We independently verified all of these e values by dry weight analysis.…”

How thick is the layer of thermal volume surrounding the protein?

“…The obtained results clearly show that the experimental data are reproduced when using thermal volume thickness of D p = 0.6 Å in the model. In the next steps the value D p = 0.6 Å (obtained Table 3 Volumetric properties of chosen proteins determined by Monte Carlo simulation at D p = 0.6Å (n h -number of bound water molecules; V M + V T + V h -sum of the protein intrinsic volume V M , thermal volume V T and volume of hydration layer V h ; v 0 MC -apparent specific volume; q 3Å -water density in 3Å layer surrounding protein surface) and experimental specific volume v 0 [11] 0.745 [43] 0.746 [45] 0.751 [46] previously for the cytochrome c) is incorporated into the model. The calculation method is tested for the remaining five proteins with this fixed value of D p. The partial specific volume v 0 MC , the hydration layer volume V h , the thermal volume V T and the water density q 3Å in a 3 Å thick layer around a macromolecule are calculated for each protein.…”