52 CHARLES TANFORD [3 



themselves easily to interpretation of the kind of configurational change 

 which is taking place. No change in these properties, however, indicates 

 that no major configurational change at all is occurring. 



Serum Albumin. Serum albumin undergoes a reversible change in configura- 

 tion near pH 4, most clearly demonstrated by the electrophoretic behavior 

 near this pH.^ Below this pH the protein shows the behavior typical of 

 simple polyelectrolytes, as demonstrated by the effect of net charge and 

 ionic strength on viscosity,^^-^^^ shown in Fig. 7. The effect of charge on 



Fig. 7. Intrinsic viscosity of ribonuclease (Buzzell and Tanford^") and of bovine serum 

 albumin (Yang and Foster^i^^ Tanford, Buzzell et a/^^.gs) Ribonuclease at ionic strengths 

 ranging from 002 to 0-25 (/^), serum albumin at ionic strengths 001 (^), 003 (£)) and 

 0-15 (Q)- The arrows indicate the isoelectric points of the two proteins. 



pH 



Fig. 8. Sedimentation (^) and diffusion (Q) coefficients for serum albumin. Sedimenta- 

 tion coefficients (Harrington et aP^) at ionic strength 01, diffusion coefficients (Champagne 

 and Sadron,!* Kekwick^e) at ionic strength 0-15, except that at pH 2-3, which is at ionic 

 strength 033. 



