Hello Matthew,

This is a very good point. With good maps one can tell if it’s the correct hand 
by visually inspecting the alpha-helices (or from features of the quaternary 
structure for some complexes), but sometimes it is more difficult. I don’t know 
how em_placement and emplace_local behave with left-handed maps. My guess is 
that they would give a solution but with a very poor LLG score.

I have accidentally run ModelAngelo [1, 2] on a left-handed map and in this 
case the failure mode is very clear: you get many disconnected short fragments 
in a left-handed map, but a much more complete and connected atomic model in a 
right-handed map. But the run time is in the same order of magnitude (a bit 
worse when using the left-handed map).

If em_placement and emplace_local fail faster on left-handed maps, that would 
be interesting to know (maybe I’ll test that sometime). But I don’t think 
there’s a hand detection method faster than visual inspection, and if the 
resolution is too poor for that, then systematically running rigid-body fitting 
and automated model building against both hands seems warranted.

Cheers,

Guillaume

[1]: https://github.com/3dem/model-angelo

[2]: https://doi.org/10.1038/s41586-024-07215-4


On 27 Nov 2024, at 20:29, Matthew Snee 
<[email protected]<mailto:[email protected]>> wrote:

Hi Gloria

I didn’t see this mentioned (perhaps I missed it). But if you are struggling to 
get your initial docking solution,  do check that your hand is correct.  If 
your map is good enough you can possibly get it by building small trial 
sections (alpha helices can be good), for more challenging lower resolution 
ones you can just try both.

Best wishes

Matthew.

Sent from Outlook for iOS<https://aka.ms/o0ukef>
________________________________
From: CCP4 bulletin board <[email protected]<mailto:[email protected]>> 
on behalf of Gloria Borgstahl 
<[email protected]<mailto:[email protected]>>
Sent: Tuesday, November 26, 2024 11:50:18 PM
To: [email protected]<mailto:[email protected]> 
<[email protected]<mailto:[email protected]>>
Subject: [ccp4bb] cryoEM molecular replacement

This Message Is From a New External Sender
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Hello Friends,
We are finally using cryoEM when the crystallography got too hard!  We have a 
crystal structure for the hexamer.  What is the easiest software tool to swing 
a monomer or hexamer into the cryoEM density?
Thank you, Gloria

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