[3DEM] A question about ice thickness of cryo-EM

Hu, Guobin guohu at UTMB.EDU
Wed Feb 16 07:51:50 PST 2005


Hi Yifan,

 

Thanks for your response. You brought a really good suggestion. I love
to try it. However due to our very limited access to the scope and due
to the fact that we don't have a CCD camera, I prefer to get a direct
answer to the question from our 3DEM community. I guess some people do
have experience on this issue.

By the way, as indicated in my previous message, the purpose for me to
estimate the maximum of ice thickness is for my image analysis, which
implied that the ice thickness is still appropriate for imaging. On the
other hand, my experience suggested that ice thickness varies on
different type of grids, for example, on 7/2 quantifoil holy grids, I
usually get thinner ice than that on 3.5/1 quantifoil holy grids. But I
have never tried to figure out how significant the difference of ice
thickness could be. 

I'm still waiting for more response and an answer. Thanks for attention
and help!

 

Regards,

Guobin 

 

 

-----Original Message-----
From: Yifan Cheng [mailto:Yifan_Cheng at hms.harvard.edu] 
Sent: Tuesday, February 15, 2005 6:39 PM
To: Hu, Guobin ; 3dem at ucsd.edu
Subject: Re: [3DEM] A question about ice thickness of cryo-EM

 

Hi

 

Well, the ice can be very very very thick no matter what grids you use. 

Did you ever get cryo grids which is too thick to be seen through?

 

What you can do to measure the ice thickness is to burn a small hole in 

the middle of the ice. Then tilt you holder to a high tilt say 60 degree


and measure the size of the hole. This can tell you how thick is your 

ice. Then you can calibrate it with your CCD camera by measure the 

counts over an empty hole and over ice. Next time just by comparing the 

CCD counts over ice and empty hole will give you some fairly good 

estimation about your ice thickness. Good luck

 

Yifan

 

 

 

Hu, Guobin wrote:

 

> Hi colleagues,

> 

>  

> 

> For our image analysis, we need to estimate the maximum ice thickness
in 

> our cryo-EM specimen on 3.5/1 quantifoil grids. We may be able to 

> estimate that based on the thickness of carbon foil. As indicated by
the 

> quantifoil product catalogue, the standard thickness of carbon foil is


> 12 nm. While observations of our cryo-EM micrographs have suggested
that 

> the thickness of carbon foil is definitely much larger than 12 nm.
Does 

> anybody have an idea of what the maximum thickness of ice could be on 

> quantifoil grids (3.5/1)?

> 

> Thanks for help!

> 

> Guobin Hu

> 

>  

> 

>  

> 

 

-- 

 

************************************************************

Yifan Cheng, Ph.D.

Department of Cell Biology, Harvard Medical School

240 Longwood Avenue, Boston, MA 02115, USA

Phone: 1-617-432-4095 (office), 432-4097 (wet lab),

              432-4708 (EM lab), 432-4107 (computer lab);

Fax:   1-617-432-1144 (department)

email: Yifan_Cheng at hms.harvard.edu

************************************************************

 

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