An inhibitor bound form of human beta secretase, also known as memapsin 2 and BACE, particularly in a glycosylated form as expressed in Chinese hamster ovary, HEK293 cells, or in insect cells as part of a Baculovirus expression system has been crystallized, and the three dimensional x-ray crystal structure has been solved to 3. The irradiation energy per pulse and the irradiation energy per sweeping unit line length of the pulsed laser are limited to a certain range. The intermediate ring is rotatably mounted to the hub via a first bearing arrangement. The mass portion also defines a clip securement pocket in which an attachment portion of the spring clip is inserted such that the clip is fixed to the mass portion.