An improved specimen loader for cryo-scanning electron microscopy.

Abstract

Cryo-electron microscopy of cryofixed samples is a well-established and accepted technique for imaging liquid-containing specimens without removing water and other volatile components. There are many steps between cryofixation and cryo-observation in the microscope, during which the sample and sample holder need to be handled. One such major step is the loading of the specimen onto the sample holder and the fixing of the sample holder onto the transfer mechanism. During this handling, the specimen is often exposed (mostly inadvertently) to moisture in the atmosphere, which results in frost deposition. The new specimen loader described here is designed to overcome the traditional tedious handling and to achieve ease in specimen loading. The modifications made are mainly towards allowing movement of the liquid freon cup, eliminating the need for a lock-screw and improving the shape of the stage holder, which makes the mounting of the specimen holder easy, thereby permitting smooth specimen loading without too much handling and with consequent reduced frost deposition.