RELEASE AND ANALYSIS OF POLYPEPTIDES AND GLYCOPOLYPEPTIDES FROM FORMALIN-FIXED, PARAFFIN WAX-EMBEDDED TISSUE

Archival tissue specimens are commonly stored as formalin-fixed, paraf fin wax-embedded blocks. Formalin fixation facilitates excellent morph ological preservation and the immunoreactivity of many antigens is pre served, but formalin-induced chemical cross-linking of proteins render s them insoluble and inaccessible to standard biochemical extraction a nd analytical methods. Thus, biochemical analysis of tissue components identified by histochemistry, with the advantage of long-term clinica l follow-up, is precluded. We have applied cyanogen bromide cleavage, a technique used routinely for fragmenting proteins for sequencing exp eriments, to solubilize transferrin polypeptides and glycopolypeptides from formalin-fixed, paraffin wax-embedded rat liver. Cyanogen bromid e cleaves protein specifically at methionine residues, yielding a pred ictable array of polypeptide fragments. Subsequent oligosaccharide ana lysis of the transferrin glycopolypeptides by anion exchange chromatog raphy confirmed that, in addition to successful release of polypeptide chains, sialylated oligosaccharide structures remained intact after c yanogen bromide cleavage. This approach may have wide applicability to a range of research interests in which correlation of tissue biochemi stry with long-term follow-up is advantageous. (C) 1998 Chapman & Hall .