Ribbon diagram of human <a href="https://en.wikipedia.org/wiki/carbonic_anhydrase" class="extiw" title="w:carbonic anhydrase">carbonic anhydrase</a> II. <a href="https://en.wikipedia.org/wiki/Zinc" class="extiw" title="w:Zinc">Zinc</a> ion visible at center.<br>Created using <a href="https://en.wikipedia.org/wiki/PyMOL" class="extiw" title="w:PyMOL">PyMOL</a> (<a rel="nofollow" class="external free" href="http://www.pymol.org">http://www.pymol.org</a>) and <a href="https://en.wikipedia.org/wiki/GIMP" class="extiw" title="w:GIMP">GIMP</a>.
<span class="int-own-work" lang="en">Own work</span>
From <a href="https://en.wikipedia.org/wiki/Protein_Data_Bank" class="extiw" title="w:Protein Data Bank">PDB</a> entry <a rel="nofollow" class="external text" href="http://www.rcsb.org/pdb/cgi/explore.cgi?pdbId=1CA2">1CA2</a>.