e"><a name="l00267"></a><span class="lineno">  267</span>&#160;                                              <span class="stringliteral">&#39;CA&#39;</span>,  <span class="comment"># calcium ion</span></div><div class="line"><a name="l00268"></a><span class="lineno">  268</span>&#160;                                              <span class="stringliteral">&#39;FAD&#39;</span>,  <span class="comment"># flavin-adenine dinucleotide</span></div><div class="line"><a name="l00269"></a><span class="lineno">  269<