Discontinuous resolution range for fit?

Submitted by oliverbclarke on Thu, 2017-06-15 13:18

Forums

ctffind & ctftilt

Hi,

With large (and fairly sparse) particles such as RyRs, I often find that I have strong Thon rings at low to medium resolution (presumambly from the protein), and then nice Thon rings at ~3-4 Å (from the solvent). This is particularly evident when processing using movie frames as input. (see example attached).

CTFFIND does a pretty good job of fitting both, but I wonder in such a case whether there might be some benefit in using discontinous resolution ranges for the CTF fit - e.g. 20-6Å for the protein, and 4-3 Å for the solvent?

Cheers
Oli

Alexis Thu, 2017-06-15 14:03

Hi Oli,

I have noticed exactly what you describe in many datasets. I have not directly tested what you suggest, but I concluded that in such datasets it was well worth fitting to ~3A. I would speculate that ignoring the midrange may not buy much in terms of SNR.

I wouldn't mind playing around with this in my spare time though... I will contact you offline to see if you could share this one movie for testing purposes. No guarantees I'll implement what you suggest, but I might.

Cheers,
Alexis