Lower case PDB codes work in internal links, e.g. [[4cpa]], but upper case codes don't, e.g. [[4CPA]]. Similarly, links to Proteopedia from outside have the same problem, e.g.[http://proteopedia.org/wiki/index.php/4cpa http://proteopedia.org/wiki/index.php/4cpa] vs. [http://proteopedia.org/wiki/index.php/4CPA http://proteopedia.org/wiki/index.php/4CPA].