Mass spectrometry kit including a cross-linked antibody or fragment thereof

Abstract

An anti-immunoglobulin specific antibody (or fragment thereof), characterised that the antibody or fragment thereof comprises one or more non-disulphide cross-links between at least one heavy chain or fragment thereof and at least one light chain or fragment thereof of the antibody or fragment thereof. A method purifying an anti-immunoglobulin specific antibody (or fragment thereof), characterised that the antibody or fragment thereof comprises one or more non-disulphide cross-links between at least one heavy chain or fragment thereof and at least one light chain or fragment thereof of the antibody or fragment thereof. A method of quantifying an amount of a subject analyte, or a fragment of an analyte in a sample from the subject comprising: (i) adding to the sample a predetermined amount of one or more control analytes or fragments thereof, which are distinguishable from the equivalent subject analyte or fragment; (ii) measuring the relative amount of the subject analyte or fragment and the amount of the control analyte or fragment in the sample; and (iii) comparing the relative amount of subject analyte or fragment to the relative amount of control analyte or fragment, to quantify the amount of analyte or fragment in the original subject sample.