plate was incubated with 50 ul of the gamma globulin fraction of pooled rabbit antimouse ldh c 4 sera after 4 hours incubation the plate was washed and then incubated with 100 ul well of 125 i goat antirabbit gamma globulin for 16 hours at 4 u00b0 c after exhaustive washing bound radioactivity was determined using a gamma counter synthesis of the peptide val asn met thr gly glu glu gly leu leu lys lys can be carried out employing solid phase techniques now well known in the art in a preferred procedure amino protected lysine representing the cooh terminal group of the above peptide is coupled to a conventional solid phase peptide synthesis resin such as chloromethyl polystyrene crosslinked with 1 to 2 divinyl benzene the amino protecting group is then selectively removed utilizing a suitable reagent whose nature will depend on the protecting group used in the preferred embodiment the t butyloxycarbonyl boc group is utilized for amino group protection and 40 trifluoracetic acid in methylene chloride is the selective deprotecting agent after deprotection the lysine is treated with protected lysine preferably u03b1boc u03b5carbobenzoxy l lysine and dicyclohexycarbodiimide in a manner known per se as to form a peptide bond between the free amino group of the lysine residue and the carboxyl group of protected lysine.