[3dem] partial gird de-vitrification in ultra-thin tip holders

[Garry P Morgan]

Hello all,
This is a question for those of you who have/use a Gatan Elsa holder, or any side entry cryo-holder with an ultra thin tip.  We have a high-tilt (thin tip) Elsa holder, and lately I’ve been seeing crystalline ice throughout the thinner areas of my cryo-grids, to the extent that I can see a diffracted electron beam on the grid bars in my low mag maps. In areas where the ice is on the thick side, the sample looks well vitrified. This consistently occurs when using the Elsa holder, but not with our older 626 holders  (so I confident that I’m not mishandling my grids and doing something to warm them up after plunge freezing). I monitor the holder temperature throughout the transfer process, and this result can be seen even when the holder temperature readout remains close to -180C the entire time (ie, from transfer station, to airlock, to column). Has anyone else seen this? I’m wondering if the ultra thin tip could be allowing enough heat to partially devitrify my grid, but not enough to register a temp rise on the holder temp sensor.
I’m open to any thoughts on how this might occur, and what could be done to prevent it.  i can send an image of my map if my explanation isn’t sufficient.
thanks,
Garry

________________________________
Garry Morgan
Director  —  Boulder EM Services —  Department of MCD Biology
Campus Box 347  —  University of Colorado  —  Boulder, CO 80309
phone:  303-492-8402

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