[3dem] CTF-correction with phase plate

[Philip Köck]

Hi.
Thanks for the paper.
If I read it correctly they simply model the phase plate as a constant phase shift (for all spatial frequencies above the cut-on).
There's also a paper by Danev where it's modeled as "1 minus a Gaussian with a standard deviation given by the radius of the spot" (charge spot, I assume).
I'm not sure about either of them, since a simple charge spot doesn't lead to a projected potential that looks like that. A very specific distribution of positive and negative charges would be required.

Are there any results on what the projected potential really looks like?
And what models are actually used for CTF-fitting images taken with phase plate?

All the best,

Philip


From: Sacha De Carlo <sacha.decarlo at dectris.com>
Sent: 27 May 2019 15:10:48
To: Philip Köck
Cc: microscopy at microscopy.com; 3dem at ncmir.ucsd.edu
Subject: Re: [3dem] CTF-correction with phase plate


You mean, apart from all the papers from Rado Danev?
How about this one here by the group of Hong-Wei Wang?


Cheers,
S.


On Mon, May 27, 2019 at 3:00 PM 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?


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