An investigator purified a protein (protein x) from e. coli.
sheinjected protein x into rabbits to generate antibodies
thatrecognize and bind to protein x. using an
electrophoretictechnique, she separated the proteins from a crude
cell extract andused the antibody to locate protein x on the gel.
to her surprise, the antibody bound not only with protein x but also
with a secondunrelated protein (protein y). when proteins x and y
weresequenced, she found that the sequence of residues 67-78,
inprotein x and that of residues 120-131 in protein y were
identical. the investigator rationalize the data, recognizing
thatantigenic determinants (epitopes) of proteins are clusters of
aminoacids.