[3dem] "leopard skin" ice

Bob Grassucci rg2502 at columbia.edu
Thu Nov 21 06:23:39 PST 2013


Hi Frank,
Let me put in my "2 cents".  What you are seeing as you call leopard 
spots is most likely from hydrophobic carbon.  If you clean you 
quantifoil grids before using them to get rid of any residual plastic 
and glow discharge them well enough this should disappear.  There is 
also a type of ice that we call snake skin which can be from the 
freezing as Dan suggests.  Contamination that builds up over time is 
usually less structured (unless it is crystalline) than what you are 
seeing and will build up over time as Guenther suggests.  Hope this helps.
Bob

On 11/20/2013 3:56 PM, Guenter Resch wrote:
> Hi Frank,
>
>> During the last weeks, I frequently observe what I believe is so-called
>> leopard skin ice in my vitrified samples (plunge frozen in ethane using
>> Mark IV Vitrobot).
> is this an artefact that builds up on the specimen over time or is it something present from the first moment on? What kind of microscope are you using?
>
> We once experienced a similar issue on our Polara - it turned out the copper braids connecting the conduction rods with the specimen were worn out and left the sample at a temperature slightly too high. Replacing the braids did eliminate the problem.
>
> Best regards,
>
> 	Guenter
>




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