[3dem] Vacuum pump for glow discharge purposes

Tue Mar 6 15:23:17 PST 2018

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/> http://www.tedpella.com/ 

530-243-2200 ext. 266

Cell 530-768-3953

 <mailto:vlad_speransky at tedpella.com> 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
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

On Mar 1, 2018, at 9:29 AM, Lena Maria Muckenfuss <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
----------------------------------------------

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