The ricin (<a rel="nofollow" class="external text" href="http://www.pdb.org/pdb/explore/explore.do?structureId=2AAI">2aai</a>) structure
<a href="//commons.wikimedia.org/wiki/User:AzaToth" title="User:AzaToth">AzaToth</a>
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<span class="int-own-work" lang="en">Own work</span>