Patent ID: 8323908

Claim:
A method of assessing the glycosylation state or functional quality of an IgG containing sample, which method comprises taking a first and a second sub-sample of the IgG-containing sample, and wherein steps (a) and (b) as set out below are applied to the first sub-sample, and steps (a) and (b) as set out below are applied to the second sub-sample except the EndoS polypeptide is substituted with an alternative IgG-binding reagent which is capable of binding unglycosylated and/or denatured, inactive IgG, wherein steps (a) and (b) are: (a) contacting said IgG-containing sample with an EndoS polypeptide which lacks IgG endoglycosidase activity, to thereby allow formation of a IgG-EndoS polypeptide complex; (b) separating said EndoS from the contacted sample; and wherein the method further comprises: (c) quantifying the amount of IgG bound to the EndoS polypeptide in the first sub-sample, and the amount of IgG bound to the alternative IgG-binding reagent in the second sub-sample; and (d) comparing both of the amounts of bound IgG determined in (c); and thereby assessing the glycosylation state or functional quality of an IgG containing sample, wherein said EndoS polypeptide which lacks IgG endoglycosidase activity is: (i) the EndoS polypeptide having the amino acid sequence of SEQ ID NO: 2; or (ii) a fragment of (i) containing residues 191 to 199 of SEQ ID NO: 2; or (iii) a fragment of (iii) in which said residues 191 to 199 of SEQ ID NO: 2 have one or more conservative substitutions, provided that glutamic acid is not present at position 199; and wherein each of (i), (ii) and (iii) has IgG-binding activity.