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

[Paul Chipman]

Hi Guobin,

The ice thickness is a product of the environmental  conditions 
(humidity, temperature), the composition of the sample, the blotting 
duration, pressure and paper and also the characteristics of the 
grid.  I don't think the grid hole size or periodicity alone dictates 
your ice thickness.  With the Quantifoil 7/2 we can get vitreous ice 
that ranges from ~25-800nm.  And, as Yifan mentioned, we can also get 
ice too thick to image through.

Cheers,
Paul

>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
>************************************************************
>
>


-- 
Paul Chipman
Electron Microscopy Facility Manager
Dept. of Biology, Purdue University
Lilly Hall, Rm. B216
Phone: 765-494-1487
Fax:765-496-1189
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