From: Yi Wang, PhD (
Date: Sun Jul 06 2014 - 17:58:04 CDT

What I used to do is to put a 100% irrelevant atom at that point and then just make use of the “within x of [atomselect XXX]” function.


Yi (Yves) Wang, PhD
Chinese Academy of Science

在 2014年7月7日,上午5:02,Josh Vermaas <> 写道:

> There isn't a direct way of doing this. Indirectly, you'd need to first calculate the reference point, then use math operations to determine if it is less than a distance away from the reference point. For example, if you determined your center of mass to be at the point (x0, y0, z0), this selection string will get you the points within radius of the center of mass.
> sqr(x-x0)+sqr(y+y0)+sqr(z-z0) < sqr(radius)
> -Josh Vermaas
> On 7/4/14, 10:48 AM, Gurunath Katagi wrote:
>> Dear All,
>> I am trying to calculate the number of tyrosine within certain distance from the geometric centre of the molecule.
>> If the calculation was based on some atom, then it would have been
>> <selection> within <distance> of protein
>> Now I that i am not getting which atom to take reference from, can you please let me know how to go about this..?
>> eg; <selection> within <distance> of <center of mass>
>> thank you
>> Gurunath