Surely not if the locations of those other atoms are strongly supported by 
density? And surely you would always select a rotamer that does not clash with 
its surroundings?

On 3/10/23, 17:32, "CCP4 bulletin board on behalf of Goldman, Adrian" 
<[email protected] <mailto:[email protected]> on behalf of 
[email protected] <mailto:[email protected]>> wrote:


Maybe simplest just to trim it back. I do worry that the presence of a wrong 
conformation will lead to inaccurate vdw clashes that could negatively affect 
other atoms.


Sent from my iPhone


> On 10 Mar 2023, at 18:25, Phil Jeffrey <[email protected] 
> <mailto:[email protected]>> wrote:
>
> On 3/10/23 4:05 AM, Julia Griese wrote:
>> Hi all,
>> My impression has been that the most common approach these days is to “let 
>> the B-factors take care of it”, but I might be wrong. Maybe it’s time to run 
>> another poll?
>> Personally, I call any other approach R-factor cosmetics. The goal in model 
>> building is not to achieve the lowest possible R-factors, it’s to build the 
>> most physically meaningful, most likely to be correct, model.
>
> And I could call your approach "model cosmetics".
>
> If you can't see the side-chain, you don't know where it is and you probably 
> don't even know where the centroid of the distribution is. Only in the case 
> of very short side-chains with few rotamers can you make a reasonable volume 
> approximation to where the side-chain is and "let the B-factors" smear out 
> the density to cover a range of the projected conformations.
>
> For longer side-chains, if you put it in a single conformation, you are very 
> likely NOT coming close to correctly modeling the actual distribution of the 
> conformations. So let's circle back on "most likely to be correct model" and 
> ask what we *actually* know about where the atoms are.
>
> Put your disordered Arg in with 10 alternate conformations, each with a 
> refined relative occupancy, and then let the B-factors smear that lot out, 
> and that's your better model.
>
> Phil Jeffrey
> Princeton
>
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