The present invention relates to the three dimensional structure of ZAP-70 protein tyrosine kinase and describes methods of making a crystal of ZAP-70 and purification of the catalytic domain of ZAP-70 for use in crystallization. The upper portion is removably mounted to the lower portion wherein the upper portion may be removed from the lower portion. The lid member blocks the opening of the tray and has a plurality of pores. With the spot-welding electrode being arranged on the side of the hinge plate and with the hinge plate and the side plate being in press contact by the spot-welding electrodes, energization is carried out for welding. The display medium is included in an electrophoretic display device by including the medium in a multiplicity of individual reservoirs of a display layer or layers that is located between conductive substrates. When the sheet feed unit is drawn from the body to a predetermined position, the sheet feed unit is rotatable downward by weight of the sheet feed unit and the sheet output unit rotates upward with rotation of the sheet feed unit.