Immunoassay and partial characterisation of serumtransferrin from Atlantic salmon (Salmo salar L.)

Atlantic salmon (Salmo salar L.) serum transferrin was purified by rivanolprecipitation followed by anion exchange liquid chromatography and polyacrylamide gel electrophoresis. Transferrin was identified by radio-iron and analysed by amino terminal sequencing. Electrophoresis showed isoforms of transferrin both on native and denaturating polyacrylamide gels. All isoforms had identical amino terminal sequences and sialic acid linked to galactose. Removal of sialic acid groups by neuramidase treatment of single and mixed transferrin isoforms revealed five different charge forms suggesting the presence of up to four sialic acid residues on Atlantic salmon serum transferrin. onal and monoclonal antibodies against salmon transferrin were produced and used in an enzyme-linked immunosorbent assay (ELISA). The sensitivity of the assay is high with the lowest detectable transferrin concentration being 0·5-1 ng ml −1. No cross activity of the assay with serum from horse, rabbit or rainbow trout could be detected. The within-assay variabilities were 2·5 and 7% when assayed within and between dilutions of the Atlantic salmon serum samples, respectively.