Preparative isoelectric focusing of equine serum amyloid A. Detection of serum amyloid A (SAA) isoforms and assessment of purity of SAA separated by preparative isoelectric focusing (IEF) of freeze-dried equine acute phase serum dissolved in 8 M urea. A: Immunostained isoforms of SAA after isoelectric focusing of concentrated preparative IEF fractions with pH of <5, 5–6, 6–7, 7–7.5, 7.5-8, 8–8.5, 8.5-9, >9. A visible precipitate was seen in the application chamber (pI 5–6) after the preparative isoelectric focusing, and was subsequently dissolved in 8 M urea. Note that SAA was only detected in this precipitate (P). B: Silverstained gel following sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) of equine serum proteins separated in 7 of the pI-intervals by preparative isoelectric focusing. Molecular weights (MW) of the Bio-Rad standard (S) are given to the right. Note that several serum proteins were detected in the precipitate described above (P).