Horseradish peroxidase that rapidly forms a covalent bond with antibodies or other proteins in the presence of 10 mM sodium cyanoborohydride at pH 9.5. Refrigerate for short term storage or keep frozen for long-term storage. Avoid repeated freeze/thaw cycles. Product is shipped FedEx overnight on ice packs within continental US. The first item is $30, additional items are shipped at no additional shipping costs.