: Thursday, February 05, 2015 3:52 PM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] proton scattering by X-rays
Mark,
In the small-molecule crystal structures I work with it's relatively common to
see localized difference electron density along covalent bonds or in the places
you'd expect to see
What about the bogey of Fourier truncation ripples--I have heard many have
been fooled by the into thinking they were seeing orbitals. How does one
tell the difference?
Indeed, there are such dangers. Hints are here:
On the possibility of observation of valence electron density for
Mark,
In the small-molecule crystal structures I work with it's relatively
common to see localized difference electron density along covalent bonds
or in the places you'd expect to see lone pairs during refinement after
you've fit and modeled the atoms reasonably well and the phases are
, February 05, 2015 9:28 PM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] proton scattering by X-rays
Not very well. When you look in the originally quoted article, there is really
not much difference in the ED for H+ and H- (which are conveniently both shown
in Fig 2). You build a model
bulletin board [CCP4BB@JISCMAIL.AC.UK] de la part de Keller, Jacob
[kell...@janelia.hhmi.org]
Envoyé : jeudi 5 février 2015 21:53
À : CCP4BB@JISCMAIL.AC.UK
Objet : Re: [ccp4bb] proton scattering by X-rays
What about the bogey of Fourier truncation ripples--I have heard many have been
fooled
...@gmail.com
To: CCP4BB CCP4BB@JISCMAIL.AC.UK
Sent: Mon, Feb 2, 2015 11:33 am
Subject: [ccp4bb] proton scattering by X-rays
Dear BB
I have (again) realised how limited by understanding of our subject is.
In Nature’s online site
http://www.nature.com/nature/journal/vaop
in chemistry class,
orbitals are not imaginary.
Mark
-Original Message-
From: Doug Ohlendorf oh...@umn.edu
To: CCP4BB CCP4BB@JISCMAIL.AC.UK
Sent: Mon, Feb 2, 2015 11:29 am
Subject: Re: [ccp4bb] proton scattering by X-rays
But, how with x-rays can one experimentally tell the difference
the opposite charges when doing this?
Perhaps one should let this rest!
Colin
-Original Message-
From: Tim Gruene [mailto:t...@shelx.uni-ac.gwdg.de]
Sent: 03 February 2015 22:57
To: Nave, Colin (DLSLtd,RAL,LSCI); ccp4bb
Subject: Re: [ccp4bb] proton scattering by X-rays
Hi Colin,
I
PM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] proton scattering by X-rays
Hi Tim
Although my SHELX comment was in jest, your point illustrates the programs
versatility. You are also right about the flat(ish) form factor for the proton.
To get to a resolution where there is a cross over
); ccp4bb
Subject: Re: [ccp4bb] proton scattering by X-rays
Hi Colin,
you can add f' for every atom type in SHELXL yourself, so in that sense, it has
been incorporated in SHELX. Bear in mind that the nucleus is point-like to
X-rays at ordinary wavelengths so that it should not have a form factor like
Subject: Re: [ccp4bb] proton scattering by X-rays
Hi Colin,
you can add f' for every atom type in SHELXL yourself, so in that sense, it
has been incorporated in SHELX. Bear in mind that the nucleus is point-like
to X-rays at ordinary wavelengths so that it should not have a form factor
but
doubtless it has been incorporated in to SHELX.
Colin
From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Ian
Tickle
Sent: 02 February 2015 13:35
To: ccp4bb
Subject: Re: [ccp4bb] proton scattering by X-rays
Peter, if it's a covalently-bonded H atom it surely
@JISCMAIL.AC.UK
Subject: [ccp4bb] proton scattering by X-rays
Dear BB
I have (again) realised how limited by understanding of our subject is.
In Nature’s online site
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14110.ht
ml?WT.ec_id=NATURE-20150129 there is a paper
Thank you all for explaining, I'm glad it was my pedantic lack of ability
to get over the description and think of the chemistry that was the
problem. Of course the positive charge would not be localised just on the
hydrogen, it is not really just a proton and so it will have some electron
Dear BB
I have (again) realised how limited by understanding of our subject is.
In Nature’s online site
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14110.html?WT.ec_id=NATURE-20150129
there is a paper describing an X-ray structure determined with sub-atomic
data (nice!). The
Peter, if it's a covalently-bonded H atom it surely can't be a bare proton,
it must have at least some partial electron around it for the (possibly
partial) covalent bond, enough to diffract X-rays anyway. As you say the
proton itself is invisible to X-rays.
Cheers
-- Ian
On 2 February 2015 at
From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Ian Tickle
Sent: 02 February 2015 13:35
To: ccp4bb
Subject: Re: [ccp4bb] proton scattering by X-rays
Peter, if it's a covalently-bonded H atom it surely can't be a bare proton, it
must have at least some partial electron
://biosci.cbs.umn.edu/bmbb/ohlen_lab/index.html
-Original Message-
From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Colin Nave
Sent: Monday, February 02, 2015 9:04 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] proton scattering by X-rays
“As you say the proton
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