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

Gekko Kunihiko

Araga Mariko

Kamiyama Tadashi

Ohmae Eiji

Akasaka Kazuyuki

Biophysical Chemistry

There are some theoretical arguments related to interpreting the adiabatic compressibility (beta(s)) of a protein determined from the sound velocity and the difference between beta(s) and isothermal compressibility (beta(T)). To address these problems experimentally, we constructed a high-pressure oscillating densitometer and used it to measure the apparent specific volume of bovine serum albumin as a function of pressure (0.1-78 MPa) and temperature (5-35 degrees C). The beta(T) determined from plots of the apparent specific volume vs. pressure was slightly larger than beta(s) at all temperatures examined, with the difference between the two compressibilities increasing as the temperature was decreased. Only at room temperature did the observed beta(T) agree with those estimated from beta(s) using the heat capacity and the thermal expansibility of the protein, suggesting that there are significant as-yet-unknown mechanisms that affect protein compressibility.

Isothermal compressibility

Adiabatic compressibility

Bovine serum albumin

Specific volume

Biology [ 460 ]

eng

Elsevier Science BV

Copyright (c) 2009 Elsevier B. V.

[ISSN] 0301-4622

[DOI] 10.1016/j.bpc.2009.06.008

[NCID] AA00566073

[DOI] http://dx.doi.org/10.1016/j.bpc.2009.06.008