| protein G

Protein G is an immunoglobulin-binding protein expressed in group C and G streptococcal bacteria much like protein A but with differing binding specificities. It is a ~60-kDA (65 kDA for strain G148 and 58 kDa for strain C40)cell surface protein that has found application in purifying antibodies through its binding to the Fab and Fc region. The native molecule also binds albumin, but because serum albumin is a major contaminant of antibody sources, the albumin binding site has been removed from recombinant forms of protein G.
 

| Typical data

As the OD values of the standard curve may vary according to the conditions of the actual assay performance (e.g. operator, pipetting technique, wash technique or temperature effects), the operator should establish a standard curve for each test. Typical standard curve and data are provided below for reference only.

 

Concentration (ng/mL)	100	50	25	12.5	6.25	3.12	1.56	0
OD	2.11	1.26	0.8	0.5	0.33	0.24	0.19	0.08
Corrected OD	2.03	1.18	0.72	0.42	0.25	0.16	0.11	-

 

| Repeatability

Intra-assay Precision (Precision within an assay)：CV% < 10%; Inter-assay Precision (Precision between assays)：CV% < 10%
 

| Recovery

The recovery of protein G spiked at three different levels in samples throughout the range of the assay was evaluated in various matrices.

 

Sample Type	Range(%)	Average Recovery(%)
Serum(n=8)	88-102	97
Plasma(n=8)	94-107	103
Cell Culture Supernates(n=8)	96-110	105

 

| Linearity

Samples were spiked with high concentrations of protein G and diluted with Universal Diluent to produce samples with values within the range of the assay.

 

		Serum(n=4)	Plasma(n=4)	Cell Culture Supernates(n=4)
1 : 2	Range (%)	82-93	88-96	90-110
	Average (%)	91	93	97
1 : 4	Range (%)	89-103	87-110	105-115
	Average (%)	94	98	109