Freeze substitution system
After high pressure freezing, samples can be processed by various methods for TEM observation. The routine technique used at the MPIPZ is freeze substitution and resin embedding (in contrast to cryo-TEM). Freeze substitution is the process of simultaneously dehydrating and chemically fixing a sample with a fixative of choice by slowly increasing the temperature. With the help of the Leica EM AFS2 automatic freeze substitution system, the temperature in the processing chamber can be controlled between -140 °C and +70 °C and a large number of freeze substitution programs can be stored. The Leica EM AFS2 also comprises a LED UV lamp for UV polymerisation of acrylic resins. Depending on the freeze substitution medium and the type of resin, samples can be used for mere ultrastructural observation or immunogold labelling.