Globulin, blood plasma molecular weight

Distribution. Lead in blood partitions between plasma and red blood cells, with the larger fraction (90-99%) associated with red blood cells (Cake et al. 1996 DeSilva 1981 Everson and Patterson 1980 Manton and Cook 1984 Ong and Lee 1980a). Lead in plasma binds to albumin and y -globulins (Ong and Lee 1980a). The fraction that is not bound to protein exists largely as complexes with low molecular weight sulfhydryl compounds these may include cysteine, homocysteine, and cysteamine (Al-Modhefer et al. 1991). Approximately 75% was bound to protein when whole human blood was incubated with 50 ig/dL lead (as lead chloride) approximately 90% of the bound lead was associated with albumin (Ong and Lee 1980a). However, the fraction of lead in plasma bound to protein would be expected to vary with the plasma lead concentration. 

Among the colloids prepared from human blood and used for plasma volume expansion, human serum albumin (HSA) and plasma protein fractions (PPF) are the most important products. HSA is a monodisperse, relatively symmetrical protein with a calculated molecular weight between 66,300 and 69,000 daltons, prepared from plasma by fractionation (for review, see Tullis 1977). PPF is a solution of plasma proteins containing about 85% albumin and 15% globulins of which the... 

Albumin contributes to around 80% of the total osmotic pressure of the plasma proteins. Because of its considerably low molecular weight compared to globulin, it is a more effective species osmotlcally. Therefore, a loss or deficiency of plasma albumin has a more negative effect on fluid balance in the body. Lowered plasma albumin leads to diminished blood volume which precipitates into a state of haemorrhagic shock. 

In the blood plasma of mammals there is present a -pseudo-globulin called transferrin or siderophilin, and which at a definite point in its molecule forms an iron complex. This protein, whose molecular weight is in the region of 90,000, makes up about 3% by weight of the plasma proteins. The iron is complexed by it in the ferric form and only in the presence of COg. When the level of iron in the plasma is at its normal value, which in man is 129y/100 ml., the transferrin is saturated to the extent of 30% of the maximum amount of iron which it can carry. The same protein can also fix copper. 

The blood plasma contains non-haem glycometalloprotein transferrin, which serves as a transport form of iron. Transferrin is pink coloured and contains Fe + bound to the apoprotein with a molecular weight of 86kDa, which belongs to the group of Pj-globulins. A transferrin molecule consists of two identical subunits, each of which contains one binding site for iron. 

A high molecular weight (820 000) plasma protein which migrates electrophoretically in the a2-globulin region. It is retained in the blood in nephrotic syndrome, when the smaller molecular weight plasma proteins are lost in the urine, and, in this condition, levels may even be increased because of feedback stimulation of protein synthesis. 

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