[3dem] contamination...leopard?

[Wim Hagen]

In the very early days it was even suggested to use ethane to "coat the sample” as a measure of preventing transfer contamination:

-------------- next part --------------
A non-text attachment was scrubbed...
Name: j.1365-2818.1986.tb02802.x.pdf
Type: application/pdf
Size: 490301 bytes
Desc: not available
URL: <http://mail.ncmir.ucsd.edu/pipermail/3dem/attachments/20220105/d08848fe/attachment-0001.pdf>
-------------- next part --------------


Best,
Wim

> On 5. Jan 2022, at 14:45, Reinhard Rachel <Reinhard.Rachel at biologie.uni-regensburg.de> wrote:
> 
> I see your point, Wim. 
> 
>> On systems with side-entry cryo-holders, the pump-time for holder insertion
> 
>> is limited and pressure is not measured by the vacuum system. 
> 
> it is measured on our 2100F. 
> I doubt that 20 sec is a good time for cryo-transfer. Vacuum always needs
> time!
> the sample temperature should be kept low enough for quite some time (120 /
> 180 sec, at least). 
> but the vacuum improves quite considerable when going from short pump times
> (20sec) up to 180 sec. or even longer. 
> this is at least the case for the air-lock/gonio of our 2100F (holder with two
> O-rings ...). 
> thus: 
> - tilting to -30 or -35 degrees is fully sufficient
> - pumping up to 120/180 sec (or even longer?) is fine, and the sample looks
> fine, too. 
> 
>> If a grid 
>> contains a lot of frozen ethane (from a fast transfer from ethane into
> liquid 
>> nitrogen on the plunge freezer), this ethane will sublimate in vacuum: too 
>> much ethane and/or short pump time -> column vacuum crashes as the ion
> getter 
>> pumps see a lot of ethane coming in when the holder is inserted. 
> 
> this is the point - thank you, Wim. 
> thus, I think Tobias & Co may try longer times for pre-pumping in the
> air-lock? 
> I do not know this type of air-lock in the Halo -  but it might work. 
> 
> kind regards,
> Reinhard
> 
> -- 
> Prof. Dr. Reinhard Rachel
> University of Regensburg
> Centre for EM / Anatomy
> Faculty of Biology & Preclin. Med.
> Universitaetsstrasse 31
> D-93053 Regensburg - Germany
> tel +49 941 943 -2837, -1666
> mail reinhard.rachel at biologie.uni-regensburg.de
> office: VKL 3.1.29 
> member of the IFSM board
> 
> Next microscopy conferences:
> - MC2023, DGE: 26.2.-2.3. 2023
> - next European EM conf.: EMC2024 in Kopenhagen, August 2024
> - IMC20 in Busan, South Korea: Sept, 2023
> - next Microbiol. conferences:  VAAM 20-23 Febr 2022 Düsseldorf
>