[3dem] Vacuum pump for glow discharge purposes

Tue Mar 6 17:37:50 PST 2018

Hi,

I had replied to Lena, but with this email, I feel that I should send my information to the whole community regarding the oil pump on the EasyGlow:

The oil was a problem at first, because the air inlet was taking in air that had tiny oil droplets (as seen by small contamination on every grid).  I added filters for the input and output hoses, and the problem went away.

I use this GD for all of my grid freezing, but there are some samples from others for which it is just too much.  What do I mean?  Well, the best vacuum it can pull is not as low as our VERY old Pelco GD, so the glow is much brighter, and the charge stronger, even with only 5 seconds of current.  Perhaps one could wait a period for the grid to lose some of the charge, but I haven’t tried that.  Also, a lab wanted to use it for Formvar/carbon coated grids and negative stain, and it broke every grid square.

Sincerely,
Esther

On Mar 6, 2018, at 6:23 PM, Vlad Speransky <vlad_speransky at tedpella.com<mailto:vlad_speransky at tedpella.com>> wrote:

Dear Lena, John, and others,

I'm Vlad, in charge of the easiGlowTM and cryo-EM supplies here at Ted Pella.  Since I took over the easiGlow two years ago, I’ve been hearing occasional but persistent requests for an oil-free pump. Seeing Lena’s post, thought I would share the following with all current and future easiGlow users.

On oil in the GD4 pump:
The GD4 pump has a special valve to prevent any backflow of oil into the instrument, so that is not an issue. Some people still want "no oil in the room", which is a bit OCD, considering how well ventilated modern preparation rooms are, but would perhaps be a concern if the pump did generate a significant amount of oil. However, it would do that only after long continuous operation, when the pump becomes warm (and it never gets even close to that with the easiGlow). And even then, there's a special Oil Mist Filter, that blue  cylindrical thing you see on top of the pump. We have at least one easiGlow unit in most or all top cryo-EM labs here in the US and Canada, and to our knowledge, all are operated with the standard GD4 pump.

On oil-free pump alternatives for the easiGlow:
The easiGlow has steep requirements to the vacuum pump, that's one of the reasons it is so robust and reliable, giving you highly reproducible results, quickly. The pump must have what is called "classic progressive pump down curve", in addition to being able to pump down fast, and it must hold the vacuum very stably. We tested many pumps before finally arriving at this GD4, which has proved to be as good as a major brand name pump selling for 3x the price. An oil-free pump of comparable performance would cost upwards of $5,000 US and be quite large (thus the Edwards XDS6i will likely work, although we have not tested it here). That's why 10 years ago when the easiGlow was first introduced we dismissed that option.

Having said all that, we are now in fact considering introducing an Oil-Free Pump, as a purchase or upgrade option. The reason is that some customers still want that, whether that is justified or not, and I feel now that the price is not much of an issue for such customers. We can of course introduce such pump only after a very thorough testing, as we are going to fully support the modified setup. So this may take a little while. Meanwhile of course anyone is free to try use their easiGlow with any pump they choose (and I would be interested in any feedback), but we at this point can only fully support it with the GD4.

@John on the edge of the bell jar being easy to chip:
That is absolutely correct. I always advise folks to use both hands when putting the chamber back in place, and use the free fingers to securely center it. But of course things can happen in a multi-user facility, and after hearing over the phone a couple times how the chamber edge “chipped itself”, I included among the highly recommended accessories for new buyers a protective L-shaped rubber gasket that goes around to cover the entire edge. The gasket is $76.80, but we are right now making it part of the standard product, free of charge.

Best wishes,
Vlad

Vlad Speransky, PhD
Life Sciences Product Specialist
Ted Pella, Inc.
http://www.tedpella.com/
530-243-2200 ext. 266
Cell 530-768-3953
vlad_speransky at tedpella.com<mailto:vlad_speransky at tedpella.com>

From: 3dem [mailto:3dem-bounces at ncmir.ucsd.edu] On Behalf Of John Rubinstein
Sent: Thursday, March 01, 2018 6:28 PM
To: Lena Maria Muckenfuss
Cc: 3dem at ncmir.ucsd.edu<mailto:3dem at ncmir.ucsd.edu>
Subject: Re: [3dem] Vacuum pump for glow discharge purposes

Dear Lena,

We’ve used the Pelco easiGLOW extensively with the standard pump for the past four or five years. It works nicely and I think it is great system. My only criticism is that if users aren’t careful it is easy to chip the bottom edge of the bell jar when removing it or putting it in place, which makes the bell jar incapable of making a seal (I think a replacement bell jar is just a few hundred dollars).

Best,
John
--
John Rubinstein
Molecular Medicine Program
The Hospital for Sick Children Research Institute
686 Bay Street, Rm. 20-9705
Toronto, ON
Canada
M5G 0A4
Tel: (+001) 416-813-7255
Fax: (+001) 416-813-5022
www.rubinsteinlab.org<http://www.rubinsteinlab.org/>

On Mar 1, 2018, at 9:29 AM, Lena Maria Muckenfuss <l.muckenfuss at bioc.uzh.ch<mailto:l.muckenfuss at bioc.uzh.ch>> wrote:

Dear list members,

we are about to purchase a "easiGlow” glow discharge system from PELCO for single-particle cryo-EM purposes and were wondering if anyone has experience with the supplied GD4 rotary vacuum pump, which is not oil-free. Are the concerns of oil leaking into the chamber true and is it worth purchasing an oil-free pump (e.g. Edwards XDS6i) instead? We would be very thankful about any experience you are willing to share.

Best wishes,

Lena

----------------------------------------------
Lena M. Muckenfuss
PhD student
Group of Prof. Martin Jinek
University of Zurich
Department of Biochemistry
Winterthurerstr. 190
CH-8057 Zurich
+41 44 635 555 | 44-L-82
----------------------------------------------

_______________________________________________
3dem mailing list
3dem at ncmir.ucsd.edu<mailto:3dem at ncmir.ucsd.edu>
https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem
_______________________________________________
3dem mailing list
3dem at ncmir.ucsd.edu<mailto:3dem at ncmir.ucsd.edu>
https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.ncmir.ucsd.edu/pipermail/3dem/attachments/20180307/5b74088d/attachment-0001.html>