Some aspects of developing instruments for cryomethods.
Well-known advantages of specimen preparation by cryomethods are accompanied by some disadvantages resulting mainly from the inadequate level of the presently existing laboratory technology and instruments. For this reason prospects of cryomethod development are to a large extent determined by a possibility of creating effective instruments mostly suitable for cryomethods. We believe this problem can be solved by elaborating exchangeable plug-in units and module-vacuum equipment capable of performing a lot of operations without removing the specimen from the vacuum. Following these principles we have designed a vacuum cryotome which allows a simple insertion and removal of the specimen through the airlock, its reliable protection against heating and contamination, and to slice the object, etching of the specimen surface in a wide range of temperatures, casting the surface with carbon and metal shadow and to making replicas. Shadowing can be done at angles varying from 15 to 90 degrees including a rotating specimen. The specimen holder and the knife have a precise thermostabilization in a wide range of temperatures. When the object is rotating, thermostabilization is preserved. The cooled screen with a vast surface safely protects the specimen against thermal radiation of the chamber walls and against oil and water contamination. Unification of the fixation sites of all exchangeable instruments, application of the same airlocks to all inlet orifices of the vacuum chamber provide a wide variability and exchange of measuring and operating devices, in- and outlet of the specimen without dis- and reevacuation of the chamber.