Hen egg-white lysozyme (HEWL) crystals have been studied by means of double-crystal synchrotron topography. The crystals reveal a number of features that are quite well known in hydrothermally grown inorganic crystals: dislocations, growth bands and growth sector boundaries. Dislocations in the (110) sectors have been characterized as edge dislocations with Burgers vector parallel to the c axis. They are distinguishable only under weak beam conditions. The presence of edge dislocations shown in this paper is consistent with the spiral growth steps previously reported. This spiral growth on protein crystals has been observed many times by surface techniques.
