Cryo-EM Imaging

Casting a cold eye on customers’ problems with Cryo-electron Microscopy

Intertek MSG provides low temperature Cryo-EM analysis for the study of aqueous systems. The high-vacuum conditions occurring in electron microscopes and their associated preparation instruments have, in the past, precluded the study of wet materials.  The process of drying water-containing samples invariably creates artefacts and often destroys features of interest.  The emergence of variable-vacuum microscopes allows only partial hydration of such samples.  New instrumentation uses low temperatures to overcome these problems, and allows us to image “wet” samples with little or no loss or distortion of material. 

Images like this picture of raw potato cells are generated on Intertek's high-resolution field-emission SEM with the aid of the Gatan  Alto-2500 cryo-system.  This allows Intertek MSG to cool small samples rapidly, and to maintain them at low temperatures during their subsequent fracture and etching, sputter-coating, transfer to the microscope and imaging. 

The key to success in studying aqueous systems such as plant tissues lies in rapidity of cooling, to avoid the formation of ice crystals.  To this end, we have acquired a Gatan Cryoplunge device, which fires a small sample into a condensed cryogen at   -180ºC. 

The  Cryoplunge also incorporates a controlled blotting system, enabling us to prepare rapidly-frozen thin-film suspensions of samples such as liposomes, viruses and macromolecules for cryo-TEM examination.  

Other in-house methods of cryo-preparation include low-temperature sectioning of materias on the Reichert Ultracut/FC4 system.  In addition to generating ultra-thin and semi-thin sections for the cryo-TEM, this device can also be used to provide cryo-planed flat surfaces for subsequent back scatter imaging, or etching and secondary electron imaging in the SEM.

This growing suite of low-temperature methods is enabling us to apply a broad range of imaging and analytical techniques to materials which were, only a few years ago, inaccessible to electron microscopy.