[3dem] CTF-correction with phase plate

[Wim Hagen]

Dear Philip,

I am not aware of any CTF-estimation package that applies the correct model for a Volta phase plate. The Volta patch to give the un-scattered beam its phase shift has a size I the back focal plane, meaning it gives a soft cut-on, see figure 2B in https://elifesciences.org/articles/23006 <https://elifesciences.org/articles/23006> . The workaround for this is to start fitting CTF past 20Å. This then requires a nice thin particle-crowded sample to stil successfully fit enough Thon-rings to estimate defocus, astigmatism and the additional phase shift parameter.

Best,

Wim

> On 27. May 2019, at 13:16, Philip Köck <Philip.Koeck at ki.se> wrote:
> 
> Dear all.
> I'm trying to find out how the contribution of a hole free or Volta phase plate to the PCTF is described mathematically in various packages that are used for cryo-EM of macromolecules.
> The physics behind it would also be of interest.
> Does anybody know a reference or have some material that can be shared?
> 
> 
> När du skickar e-post till Karolinska Institutet (KI) innebär detta att KI kommer att behandla dina personuppgifter. Här finns information om hur KI behandlar personuppgifter <https://ki.se/medarbetare/integritetsskyddspolicy>. 
> 
> Sending email to Karolinska Institutet (KI) will result in KI processing your personal data. You can read more about KI’s processing of personal data here <https://ki.se/en/staff/data-protection-policy>. 
> _______________________________________________
> 3dem mailing list
> 3dem at ncmir.ucsd.edu <mailto:3dem at ncmir.ucsd.edu>
> https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem <https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.ncmir.ucsd.edu/pipermail/3dem/attachments/20190527/acccc278/attachment.html>