What is the pI of IgG?

Dom Spinella dspinella at chugaibio.com
Fri Feb 20 12:16:32 EST 1998

> >All,
> >
> >I have been reading through Maniatias, Current Protocols in Mol. Bio.,
> >etc. but I have been unable to find a reference to the pI of IgG. I need
> >to find out since I believe I may have a proteoglycan which elutes off of
> >DEAE not far after the contaminating IgG.
> >
> >If anyone can forward a little wisdom it would be greatly appreciated.
> >
> >Thank you in advance,
> >
> >Brian Thoma
> >Univ. of Texas at San Antonio
> >Extracellular Matrix Laboratory

Well Brian, you posted this question a few days ago to the Methods and
Reagents Usegroup, and I'm afraid the answer is still the same.  It can
range from as low as 5 to as much as 12 depending on the individual
antibody molecule in question. However, to give you a bit more detail, a
sampling of about 50 human myeloma proteins yielded the following
results for the four subclasses of IgG:

IgG1  Average pI = 8.6 with a S.D. of 0.4
IgG2  Average pI = 7.4 with a S.D. of 0.6
IgG3  Average pI = 8.3 with a S.D. of 0.7
IgG4  Average pI = 8.0 with a S.D. of 0.8

Source: Hamilton, R.G "The Human IgG Subclasses" Calbiochem Corporation

Hope this helps.

--Dom Spinella

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