= Nuclear pore localization experiment
In a 1982 experiment, purified <nucleoplasmin> was labeled with radioactive <iodine> and cleaved by <proteolysis>. <Microinjection> delivered cargo into <Xenopus laevis> <oocyte> <cytoplasm>. Manually separated <cell nuclei> and <cytoplasm> were compared by <gel electrophoresis> and <autoradiography>; section <autoradiography> checked internal localization. Tail-bearing cargo entered the <cell nucleus>; tailless cores did not. Direct nuclear <microinjection> retained the cores: the tails mattered for entry, but the assay did not identify a receptor.<A polypeptide domain that specifies migration of nucleoplasmin into the nucleus by Colin Dingwall and others>[Cell 30, 449–458: Figures 2–3, 5 and 7; The Trypsin-resistant Core Remains in the Nucleus after Nuclear Injection]{ref}
\Image[/nuclear-pore-localization-assay.png]
{title=Changing cargo and injection site separates nuclear entry from retention}
{description=Original qualitative summary of the <nucleoplasmin> comparisons above. Symbols represent localization, not measured counts or copied source images.}
Direct nuclear <microinjection> bypassed entry, distinguishing failure to enter from failure to remain inside a <cell nucleus>.
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