[3dem] Use of methanol in cryo-EM samples

[Matthias Wolf]

Hi Jie,

As Ruben mentioned, there is no problem from the point of view of the cryo-TEMs, but the issue is rather about the effect of organic solvent on your sample and on the image quality. The bottom line is that most organic solvents result in much reduced dose tolerance compared to vitreous ice.

We have imaged inorganic samples at LN2 temperature in frozen DMF, which is even more radiation-sensitive than methanol. Adding water, if miscible, can increase the dose-tolerance of the solvent.

For an excellent study about the dose tolerance of various solvents, see this paper by Zhang et al: https://urldefense.com/v3/__https://onlinelibrary.wiley.com/doi/full/10.1002/rpm.20230025__;!!Mih3wA!GcaNfE81R9yrQOQH7KwIWIPJHFkPIA2lTyV5mdAQ8Eu9xqw9OWCo-n-7_qu-l3GTTxiJS3Oyzp7hiE2iP5dVcGUaLZQ$ 

Best regards,

    Matthias

________________________________
From: 3dem <3dem-bounces at ncmir.ucsd.edu> on behalf of Ruben Diaz Avalos <rdiaz at lji.org>
Sent: Thursday, May 9, 2024 2:59 AM
To: Jie Zhang <jiezhang518 at utexas.edu>
Cc: 3dem at ncmir.ucsd.edu <3dem at ncmir.ucsd.edu>
Subject: Re: [3dem] Use of methanol in cryo-EM samples

Hi Jie,

I have used up to 20% methanol (and ethanol, acetonitrile, acetone...) in some samples; the amount of solvent in the frozen samples is so minimal that there is no way they can cause any damage to anything, but I can tell you that the beam-induced movement of these samples is much worse than in a purely aqueous buffer.

Ruben.

On Wed, May 8, 2024 at 9:44 AM Jie Zhang <jiezhang518 at utexas.edu<mailto:jiezhang518 at utexas.edu>> wrote:
Hi everyone,
I am trying to use methanol in my cryo-EM samples (specifically for Glacios and Krios). Is there anyone who has prepared the grids with samples containing more than 10& methanol? I just want to make sure high concentration of methanol is okay for these machines.
Thank you.

Best regards,
Jie Zhang


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