418 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1945 



Table 1. — Relative dimensions of NACL, glucose, hemoglobin, red blood cells, and 

 the various plasma proteins 



Among plasma proteins certain of the globulins are twice as long 

 as the albumins, and the protein that forms the matrix of the blood 

 clot, fibrinogen, is a rod-shaped molecule 6 times as long as albumin. 

 Fibrinogen is almost 30 times as long as its diameter. Its solutions 

 are therefore extremely viscous, viscosity being a function not of the 

 size of molecules but rather of their asymmetry. Fibrinogen is present 

 in the plasma, however, to only 0.24 to 0.3 percent, representing 4 to 5 

 percent of the plasma proteins. By contrast, the albumins represent 

 55 to 60 percent of the plasma proteins, are by far the most soluble, 

 and their solutions are the least viscous. 



Elementary considerations indicate different ways in which the size 

 and shape of the plasma proteins influence the blood. The osmotic 



RELATIVE DIMENSIONS OF VARIOUS PROTEINS 



Sco/e 



100 A No* Ci" Glucose 



Hemoglobin Serum Albumin 



Serum ^-Globulin 



Fibrinogen 

 Figure 1. — Relative dimensions of various blood proteins. If the serum albumin 

 molecule were the length of this page, a red cell would be the size of a football 

 stadium. A value of about 6,000,000,000,000 is obtained for the weight of Ava- 

 gadro's number of red blood cells, which are therefore about a billion times the 

 weight of a serum albumin molecule. Values: hemoglobin, 68,000; serum 

 albumin, 69,000; serum and globulin, 156,000; fibrinogen, 500,000. Scale models 

 and many of the estimates by Oncley. 



