[3dem] temperature depentend cryoTEM

[Frank Polzer]

Dear all,

 

I have recently observed trouble when I was trying to investigate polymer
colloids by cryoTEM that show a temperature-dependence in water. I would
like to investigate the particles at 10°C and 40°C solution temperature by
cryoTEM. They are expected to be bigger at low temperatures. Size should
decrease about 30% upon heating to 40°C. This has already been demonstrated
by Talmon et al. (http://pubs.acs.org/doi/abs/10.1021/la053198f). I am not
able to reproduce this using the Vitrobot. I end up with particle size at
low temperature being considerably smaller than expected and at high
temperature considerably bigger than expected (the latter I could explain
that upon approaching the liquid ethane interface the thin film cools down).


 

I am using FEI Vitrobot Mark IV and do the following procedure:

 

-          Equilibrating the dispersion with a thermostat for at least 1 h
(checked the thermostat already if it sets the temp. correctly)

-          Equilibrating the pipette tips in the same way

-          Equilibrating the Vitrobot for at least 1 h at 100% humidity and
the desired with tweezers and grids inserted (checked the Vitrobot already
if it sets the temp. correctly)

-          Then I apply 5µl of tempered solution onto the tempered grid in
the tempered Vitrobot chamber

-          I wait for another 10-15 min to avoid thermal fluctuations due to
sample transfer

-          I blot and shoot the grid in liquid Ethane using no drain time
and transfer it into the Gatan 914 holder

 

Does anyone have an idea what might change the solution temperature and
herein the particle size during vitrification (filter paper, cold ethane
vapor, etc.)?

 

Thank you for your help,

 

Frank

 

Dr. Frank Polzer 
TEM Group 
Institute of Physics 
Humboldt Universität zu Berlin 
Newtonstraße 15 
12489 - Berlin 
  
Tel.: +49 30 2093-4995 (office) 
Tel.: +49 30 2093-7829 (TEM) 
Fax: +49 30 2093-7886
  
 <mailto:frank.polzer at physik.hu-berlin.de> frank.polzer at physik.hu-berlin.de

 

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