Dairy Chemistry And Biochemistry

(^198) DAIRY CHEMISTRY AND BIOCHEMISTRY
, H-chain
Figure 4.29 Models of IgG, IgA, IgD, IgE and IgM. (a) Structural model of IgG, before and
after fragmentation by pepsin and papain and reduction with a sulphydryl reagent. Solid black
chain portion = variable regions; light chain portion = constant regions. Small black lines
represent disulphide and half-cystine (-SH) groups. Small black dots in Fc regions represent
attached carbohydrate groups. The various parts of the model are labelled. (b) The structure
of four classes of immunoglobulins are shown with monomeric IgA, dimeric IgA and secretory
IgA. Location of the J-chain, secretory component (SC) and carbohydrate is approximate.
(From Larson, 1992.)