Re: [ccp4bb] atomic FF used in SFALL

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CCP4bb <-- 2007 <-- October 2007 <-- 11 October 2007

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Subject: Re: atomic FF used in SFALL
From: Eleanor Dodson ccp4 {- at -} YSBL {- dot -} YORK {- dot -} AC {- dot -} UK
Date: 2007-10-11

I wrote that - is a constant a Gaussian? Anyway that is how I got 5 -
and it is the

9-parameter Cromer-Mann approximation..

And Yes - each component is added to the B value to build up the real space atomic density.

as you show.

Eleanor

Bernhard Rupp wrote:
> Dear All,
>
> I read in SFALL docu that a "2- or 5-Gaussian"
> approximation for SFs is used - I quote from SFALL docu:
>
> begin----------------------------------------------------------------
> a1*exp(-b1*s*s) + a2*exp(-b2*s*s) - 2 Gaussian approximation
> (Agarwal, 1978)
> or as:
>
> a1*exp(-b1*s*s) + a2*exp(-b2*s*s) + a3*exp(-b3*s*s)
> + a4*exp(-b4*s*s) + c
> - 5 Gaussian approximation
> -------------------------------------------------------------------end
> Note:
>
> 1) The second formula is a 4, not 5 Gaussian approximation -
> Is it the 9-parameter Cromer-Mann approximation?
>
> 2) If so, one would need to convert this (reciprocal space) scattering
> function into real space e-density when making the map to be FFTed:
>
> rho(r) -> FT -> f(s) <-this f(s) is what the scattering formula above
> describes
>
> for example from
>
> recip: exp(-Bs*s/4) I would get FT-1 -> real:
> ((4pi/B)**3/2)exp(-4pi**2*r**2/B)
>
> and use that actually to decribe the atom shape in the map generation. True?
>
>
> Thx,
>
> br
> -----------------------------------------------------------------
> Bernhard Rupp
> 001 (925) 209-7429
> +43 (676) 571-0536
> br@qedlife.com
> bernhardrupp@sbcglobal.net
> http://www.ruppweb.org/
> -----------------------------------------------------------------
> Every day above ground is a good day.
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>
>
>

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CCP4bb <-- 2007 <-- October 2007 <-- 11 October 2007

Previous message:
Subject: Re: His tag does not bind.
From: Tim Gruene tg {- at -} SHELX {- dot -} UNI-AC {- dot -} GWDG {- dot -} DE
Date: 2007-10-11

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Subject: Refmac and planar amide restraint
From: Jason Greenwald jason {- dot -} greenwald {- at -} PHYS {- dot -} CHEM {- dot -} ETHZ {- dot -} CH
Date: 2007-10-11