[3dem] Insertion of Holder 626

Mon Feb 24 13:01:35 PST 2020

If we order O-rings from Thermo, it cost one arm… Does anyone have references for « standard » O-rings that we can buy elsewhere for a much cheaper price?

To come back to the original questions, we still use 626 and other side-entry holders. Sometime we face vacuum problems. In our experience these are mainly due to (as already said):

- Dusts on the O-ring (or inside the airlock system). Inspect the O-ring and also try to blow dry-air inside the airlock. Maybe the airlock tube is damage, then ask Thermo for repair … :-(

- Dry O-rings: regularly put some (not a lot !) vacuum grease on it. Be careful not to scratch the metal when removing it or damaging the O-ring. Change it if dry or obviously damaged.

- One frequent issue with cryo-holders: do not fill the cryo-holder station with to much LN2, you may freeze the O-ring and it will inevitably lead to a vacuum leak (very reproducible!). To limit this issue, we slightly lift the cryo-holder station with a rectangular grid box to avoid LN2 going into contact with the O-ring. We (not every one of us) cool the cryo-stage inside the microscope. Then the work-station is cooled just before inserting the specimen grid on the holder. This also limits the risk of cooling the O-ring.

- We « pre-pump » the airlock, and pump for 1 min before inserting (on a Tecnai G2 Sphera). 3 min of pumping seams a lot!

- Change of the zeolithe, grease on the valve O-ring of the cryo-holder, periodic zeolithe cycle (we do it every session): it improves stability on our side.

Best

Denis

> Le 24 févr. 2020 à 21:26, David Stokes <stokes at nyu.edu> a écrit :
> 
> I used to do the following prior to every session:
> Remove o-ring from holder.
> Clean o-ring off with kimwipes and fingers (I didn't bother to use any solvent).
> Clean o-ring groove with kimwipes.
> Blow away fibers with compressed air.
> Lightly grease o-ring.
> Inspect o-ring and o-ring groove under dissecting scope and carefully remove any fibers prior to re-installation onto the holder.
> Don't scratch the o-ring groove. In fact, don't touch it with forceps. Use compressed air.
> 
> During the inspection process, you will see whether there are any nicks or flat spots in the o-ring. If so, then consider a replacement. If there is a scratch in the o-ring groove, then you might need a new holder (or maybe not).
> Also make sure you really have the right sized o-ring. At some point in ancient history, they changed the size slightly, such that CM200 o-ring was a bit fatter than the one for the CM12 stage.
> 
> David
> 
> 
> On 2/24/2020 3:10 PM, Sharon G Wolf wrote:
>> Terje
>> We also have suffered for years from vacuum breaks. We tried EVERYTHING. The most effective thing was to (believe it or  not) change the o-ring every single session.
>> Recently we understood this was due to the fibers and other "dirt"  that we observed on the o-rings every time we looked with the binocular after inserting and removing the holder from the microscopes, transfer stations or pumping station. We embarked on a “cleaning program” where we gently swab all the above mentioned devises. It’s now slowly getting better. We are still changing the o rings but we hope it will soon no longer be necessary, once all the "stuff" that accumulated over the years is cleaned out from those places.
>> Sharon
>> 
>> 
>> Sent from my iPhone
>> 
>>> On 24 Feb 2020, at 19:28, Dokland, Terje <dokland at uab.edu> wrote:
>>> 
>>> We have also had persistent vacuum break problems with our 626 holder in our Tecnai F20 over the past two years. About 50% of the time inserting the holder breaks the vacuum. I though it was unique to this holder, but with the Elsa holder that we recently acquired it is even worse: vacuum break about 90% if the time. We’ve changed O rings, had the airlock disassembled and cleaned, but the problem persists.
>>> 
>>> That being said, it never affected ice quality, and the temperature usually doesn’t go above -165 C. When the vacuum recovers it’s usually at 25-30 log or so and back to <10 within a half hour. It’s really annoying though.
>>> 
>>> In my experience as long as the temperature doesn’t rise above -150C you should be ok.
>>> 
>>> It helps to make sure the tip is very cold by submerging it completely in lN2 before inserting.
>>> 
>>> Terje
>>> 
>>> Sent from my iPhone
>>> 
>>>> On Feb 24, 2020, at 7:13 AM, TALAVERA PEREZ Ariel <Ariel.Talavera at ulb.be> wrote:
>>>> 
>>>> Dear all,
>>>> 
>>>> I am using a Gatan 626 holder on a side entry TALOS microscope. I am
>>>> getting problems with very frequent crystalline ice formation on the
>>>> grids. Some times I get a mix of vitreous and crystalline water, but
>>>> must of the time I only get crystalline water. I have been extra careful
>>>> during sample preparation, and transferring the grind on to the holder,
>>>> and I have done 48 hours holder bake out before insertion, but I still
>>>> get ice on the grid.
>>>> 
>>>> I monitored the temperature of the holder during the insertion process,
>>>> including 3 minutes for the Airlock pump. During those 3 minutes the
>>>> temperature rises up to -152.2. Can this be the reason of the unwanted
>>>> ice formation? How high can be the temperature of the holder to ensure a
>>>> nice vitreous water?
>>>> 
>>>> I am also getting vacuum problems while inserting the holder. This
>>>> process has resulted to be extremely, extremely sensitive. After the 3
>>>> minutes Airlock pumping (I cannot give longer time because of the
>>>> aforementioned temperature issue) as soon as I open the column port the
>>>> vacuum either rises to 99 Log or completely crashes the column vacuum.
>>>> This has happened with two different holders either cooled with liquid
>>>> nitrogen or at room temperature. So, my question: Is this insertion
>>>> process always that  picky or it can be that there is something wrong
>>>> with the holders/Airlock pump?
>>>> 
>>>> Thanks a lot in advanced.
>>>> 
>>>> Best regards.
>>>> 
>>>> Ariel
>>>> 
>>>> -- 
>>>> Ariel TALAVERA PEREZ, PhD
>>>> Center for Microscopy and Molecular Imaging (CMMI)
>>>> Laboratory of Microscopy
>>>> Université Libre de Bruxelles
>>>> Rue Adrienne Bolland, 8
>>>> B-6041 Gosselies, Belgium
>>>> Phone +32 (0)26509866
>>>> 
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> 
> -- 
> David L. Stokes
> Skirball Institute, Dept. of Cell Biology
> NYU School of Medicine
> http://stokeslab.med.nyu.edu/ <http://stokeslab.med.nyu.edu/>
> tel: 212-263-1580
> fax: 212-263-2150
> 
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