Protein A (MW 42 kDa) is capable of binding to the Fc portion of immunoglobulins, especially IgGs, from a large number of species. One protein A molecule has been shown to bind at least 2 molecules of IgG simultaneously. The IgG binding domain of Protein A consists of three anti-parallel α-helicies, the third of which is disrupted when the protein is complexed with the Fc region of the immunoglobulins. Protein A will bind the Fc portion of human IgG subclasses, IgM, IgA and IgE; and mouse IgG1 (weakly), IgG2a, and IgG2b. Protein A also binds IgGs from other species, including monkey, rabbit, pig, guinea pig, dog, and cat.

Phycoethyrin: Phycoethyrin (R-PE) is a 240 kDa protein from the light-harvesting phycobilliprotein, phycoerythrin is composed of a protein part, organised in a hexameric structure of alpha and beta chains, covalently binding chromophores called phycobilins. In the phycoerythrin family, the phycobilins are: phycoerythrobilin, the typical phycoerythrin acceptor chromophore, and sometimes phycourobilin (marine organisms). Phycoerythrins are the phycobilliprotein which bind the highest number of phycobilins (up to six per alpha-beta subunit dimer).

R-PE purified from Poryhyra tenera; A565/A280 >5.0; A 1% 565 nm=82; Amax = 490, 545 and 566 nm; E max = 580 nm