Cryomicroscopy - just getting warmed up!

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On the 12 & 13th of November 2013 I attended the 25th anniversary meeting of the UK Cryo Microscopy Group at the University of Birmingham. This group has been meeting annually to discuss and present research in the area of cryomicroscopy and cryogenic sample preparation techniques and this year was no exception. A full report of the meeting will be presented by our Editor, Julian Heath, in the January issue of M&A, but in this blog I'd like to give my thoughts on what this milestone meeting meant for me and indeed what it means for all of microscopy.

We all know the basic problem that water and vacuum don't mix, which is an issue for electron microscopists interested in imaging biological samples without the shrinkage caused by drying. Almost as long as there have been scanning electron microscopes, there have been scientists and engineers who have tried to stabilise high water (or other volatile) systems in order to allow microscopy and microanalysis. Even before the scanning electron microscope became a reality, researchers were trying to preserve samples for analysis, without the use of fixatives and stains. In fact the first cryosections were for light microscopes, and therefore didn't require the stringent and ice crystal-free preparation of today.

The trials and tribulations of these early pioneers (some of who attended the meeting and spoke at the first meeting in 1988!) were utterly fascinating to hear. We learned that they frequently attempted to create the tools (often using items begged, borrowed or repurposed) and protocols that just didn't exist – all with the aim of being able to stabilise, manipulate and analyse samples in the microscope. In the mid-60s the high-pressure freezer was pioneered in Switzerland, however, it was not until 1985 that a commercial product was launched. Until then sample freezing was mostly done in liquid nitrogen or nitrogen slush (for faster freezing), however this still resulted in ice crystal formation.

At the November meeting, we heard from Keith Ryan about his experiments freezing in liquid propane and ethane in the 70s and 80s, as he attempted to avoid ice formation. Another pioneer, recently honoured by a Royal Microscopical Society meeting, was Alice Warley who successfully performed elemental analysis (EDS) on nitrogen slush plunge-frozen biological samples, something virtually unheard of at the time! I found this especially impressive as the aim of her experiments was to probe elements (calcium, sodium and potassium) in the face of the (unavoidable) ice damage.

Cryo-SEM image of powdery mildew Erysiphe on wheat, circa 1983, courtesy of Jill Webb. Scale bar = 10 um.

The inspirational presentations from both Keith and Alice, coupled with stunning images from Jill Webb, presented on behalf of John Sargent, reminded me that we don’t always have to have the latest kit or perform an extremely involved preparation procedures to get the information you need, sometimes 'good enough' will do.

There were presentations from Helen Saibil and Richard Henderson, who spoke on the origins and developments in single particle cryoelectron microscopy, and Kent McDonald gave an overview of cryotechniques, in particular freeze-substitution (resin embedding and staining at low temperatures), which is now being linked together with other microscopy techniques (watch out for a future blog post).

All things considered, the meeting brought home to me that there are many developments and approaches we owe to cryomicroscopy and the demands placed on the instruments and operators who choose to dabble with high-water content samples. Without these pioneers and the chance to come together, discuss, swap ideas, brainstorm and push forward the boundaries of what is possible, I doubt cryo-EM in the UK would be where it is today. Keep up the good work CMG!

What do you think? Is cryomicroscopy still a growth area? Did you attend the meeting? I’d love to hear from you.

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