Specific volume of proteins

Fig. 5. Hydration dependence of the volume of human serum albumin crystals. Specific volume of crystals of the dimer form of human serum albumin as a function of water content, o, Determined during drying , determined during rehydration. Extrapolated intercepts of solid line Up = 0.734 cm /g and = 0.995 cm= /g. The dashed line with arrowheads indicates the region of failure of the simple linear relationship and of deviation of partial specific volumes of protein and water from the dilute solution values. From Richards (1977).

Equation 5.9 has been derived from a correlation of data obtained with compounds with molecular weights between 100 and 500, and it does not give good estimates of the diffusion coefficient of polymers, especially proteins. Nevertheless, as the specific volume of proteins is nearly constant, around 0.73 [17], their molecular volume is proportional to their molecular weight, and Eq. 5.9 predicts values of the diffusion coefficient between 0.5 and 1 x 10 ... 

McMeekin TL, Marshall K (1952) Specific volumes of proteins and the relationship to their amino acid contents. Science 116 142-143... 

The removal of the 24- and 18-kDa polypeptides decreased the distance by about 7 %, whereas the further removal of the 33-kDa polypeptide decreased the distance only by 1 A. This suggests that the 24- and 18-kDa polypeptides bind closer to d" " than the 33-kDa polypeptide. The distance allotted for these peripheral polypeptides (approx. 8 X) is much smaller than the radii (21, 19 and 17 A for 33-, 24- and 18-kDa proteins, respectively) calculated from their molecular masses and the partial specific volume of protein (0.72 cm for a spherical molecule. This may be due to the assumption that the inner surface of the PS-II membrane is flat even when the membrane binds the peripheral polypeptides. Based on the present work and the analogy of PS II with the bacterial reaction center, v/e propose a model for structural organization of PS II in Fig. 3. 

To estimate the mass concentration of water in plasma a volume displacement effect by proteins and lipids has to be taken into account and is integrated in the mass concentration factor for standard plasma specimens. The correction factor for the mean specific volume of proteins is assumed to be 0.73 and 1.03 for lipids, respectively ... 

The partial specific volume of proteins can be measured experimentally [11,12] or can be estimated from the amino acid composition of the protein using equation... 

The partial specific volume of protein does not significantly change with temperature within that range. 

The present review reports a critical summary of experimental values of partial specific and isopotential specific volumes of proteins, and of partial molar and partial specific volumes of low-molecular compounds of special relevance to protein chemistry. Included are also the volumes of some other (bio)polymers of interest. In addition to the tabulation of observed values many calculated volume data are presented. Furthermore, theoretical and practical aspects of volume determinations are discussed and a comprehensive description of incremental approaches for the calculation of both small and large molecules is presented. 

The temperature dependence of the specific volume of proteins outside the range of thermal stability (usually outside the linear range between 4 and 45 °C) is complex and nonlinear. A plot of specific volume vs. temperature may display several sections, the thermal effects depending on the protein under investigation and the environmental conditions (e.g., pH, solvent, presence of additives). For example, a... 

---