[3dem] Alkylamine vapor while glow discharge

[Jacques Dubochet]

Thank you Wim for the comment. Yes it is as you say.

Concerning the hydrophilic/hydrophobic nature of the amyl-amine  
(pentylamine) glow-discharged film, we had the following observation.
Simple tests for the  hydrophobiciy/hydrophilicy of a grid consist in
- touching the edge of the dry grid with a drop of water. If the  
surface is very hydrophilic, the drop spread immediately over the  
whole surface.
- touching the edge of the grid covered with a drop of water with a  
blotting paper. If the surface is very hydrophilic the water goes in  
the blotting paper but a thin layer of water always remains on the  
whole grid.
The strange thing with amyl-amine treated film (as I was used to do  
it) is that the film was hydrophobic according to the first test but   
hydrophilic according the second test, once the drop was  forced on  
the surface.
We proposed some explanations but they have never been seriously  
tested as far as I know.
Complicated!

Jacques Dubochet
Honorary professor.
DEE, Biophore, 3203
University of Lausanne
CH-1015-Lausanne
Jacques.Dubochet at unil.ch
Phone (office): +21 692 4187




Le 12 févr. 09 à 09:27, Willem Tichelaar a écrit :

> Hi Eduardo,
>
> Just in case somebody hasn't told you yet: glow-discharging in an  
> amine atmosphere was, as far as I know, originally used to get  
> nucleic acids adhered to carbon film; the reference is: Dubochet et  
> al., J. Ultrastr. Res. 35 (1971) 147-167.
>
> Since nucleic acids are negatively charged at neutral pH, they do  
> not attach to a carbon film that has been glow-discharged in  
> residual air, because this process results in a negatively charged  
> surface.
>
> As far as I know, Jacques advocated to carry out glow-discharging  
> in amine and in residual air in separate vacuum recipients: once a  
> device is contaminated with an amine, it will remain contaminated  
> with this compound. The glow-discharging device that he had built  
> at the EMBL has two vacuum recipients, each with its own pump.
>
> Best,
> Willem Tichelaar
>
>
> Eduardo Sanz Garcia wrote:
>> The use of alkylamine vapors in glow discharge apparatus makes the
>> grid positively charged. But I found some contradictory information
>> about the hydrophobicity:
>> Some say that it makes the surface hydrophilic, others hydrophobic.
>> If it makes the surface hydrophobic, while is still used in cryoEM?
>> Shouldn't that prevent the fluid from spreading evenly on the grid
>> surface?
>> Does someone have experience in this type of treatment?
>>
>> Additionally,
>> Has someone use magnesium acetate, lysine or polylysine after glow
>> discharge to make the surface positively charged?
>>
>> Thank you.
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>>
>>
>
> -- 
> Willem Tichelaar, Ph.D.
> European Molecular Biology Laboratory
> Meyerhofstr. 1
> 69117 Heidelberg, Germany
>
> phone: +49 (0)6221 387 193; fax: +49 (0)6221 387 519
>
>
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