Subject: Re: [ccp4bb] Can twinning be seen in the diffraction pattern?
Yes Ana, I agree although some non-merihedrals where the accident of cell
dimensions mean many spots can overlap but not quite exactly can seem a bit
smeary and "multiple.
Meridral twins do not usually look multipl
PS: For a microscopically visible example in proteins, see the lovely
cubic insulin interpenetrating non-merohedral twin crystallized by
Madhumati Sevvana (Fig. 11a; thankfully open-access article):
Madhumati Sevvana, Michael Ruf, Isabel Uson, George M. Sheldrick and
Regine Herbst-Irmer.
Far as I understand, twins may or may not have macroscopically
recognizable features. Macroscopic (and microscopic) features like
face angles, reaction on etching, polarization of light, etc. can
sometimes indicate twinning for at least a subset of cases, e.g. in
diamond, some forms of quartz,
1911 when none of us was born.
I think all of that is not just pure semantics. Am I wrong ?
Philippe Dumas
De: "Ana Luísa Moreira de Carvalho"
À: "CCP4BB"
Envoyé: Mercredi 17 Mars 2021 11:12:53
Objet: Re: [ccp4bb] Can twinning be seen in the diffraction pattern?
Yes Ana, I agree although some non-merihedrals where the accident of cell
dimensions mean many spots can overlap but not quite exactly can seem a bit
smeary and "multiple.
Meridral twins do not usually look multiple - they are usually only
revealed by the 2nd moment and other stats..
Eleanor
On
Just a short note on this: I often see colleagues using the word “twinning"
when referring to a crystal that is actually multiple (not single).
I think much confusion arises from this. For me, a twin crystal is the one that
looks single under the microscope and only intensity statistics reveal
You usually detect twinning most reliably from the intensity statistics -
CCP4I2 and Xtriage report those..
Eleanor
On Tue, 16 Mar 2021 at 07:31, Marina Gárdonyi <
marina@pharmazie.uni-marburg.de> wrote:
> Dear all,
>
> thanks to all who helped me solving the question. You sent me a lot of
>
Dear all,
thanks to all who helped me solving the question. You sent me a lot of
comments and information I have not taken into account.
After reading all the answers, I have come to the conclusion that the
spots that are very close to each other come from the long cell axis
(57-57-160)
: Re: [ccp4bb] Can twinning be seen in the diffraction pattern?
Dear Marina,
Mark seems to have hit the nail on the head. The left-hand picture of your
second jpg shows that you have an axis, at about 45 degrees from the horizontal
(and hence from the rotation axis), along which the spots
Dear Marina,
Mark seems to have hit the nail on the head. The left-hand picture of
your second jpg shows that you have an axis, at about 45 degrees from the
horizontal (and hence from the rotation axis), along which the spots are
very close. These spots seem to be only just separated on that
Hi Marina,
The close-together spots in the zoom inset of your figure I think are not split
spots, but separate reflections. They are close togeter because you appear to
have a unit cell with one axis much longer than the other two (we work on
elongated proteins, so we have some experience with
/DE
Sent: Friday, March 12, 2021 8:11 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: [ccp4bb] AW: [ccp4bb] Can twinning be seen in the diffraction pattern?
Dear Marina,
A lot can happen with twinning andthe crystallization process does not always
adhere to rules written in text books.
The first thing I woul
richt-
> Von: CCP4 bulletin board Im Auftrag von Marina
> Gárdonyi
> Gesendet: Freitag, 12. März 2021 11:31
> An: CCP4BB@JISCMAIL.AC.UK
> Betreff: [ccp4bb] Can twinning be seen in the diffraction pattern?
>
>
> Hello everyone,
>
> I am a PhD student at the Philipp
, 12. März 2021 11:31
An: CCP4BB@JISCMAIL.AC.UK
Betreff: [ccp4bb] Can twinning be seen in the diffraction pattern?
Hello everyone,
I am a PhD student at the Philipps-University in Marburg and I am currently
writing my thesis.
I have problems to understand whether in my case twinning c
Any twinning is due to overlapping diffraction patterns from two or more
different crystal fragments.
This means that the "intensity" measured is in fact the sum of two or more
different I(hkl) s eg in your case* I(hkl) obs* actually equals *I(h k l
) + sc (I -h -k l)* .
The diffraction can look
15 matches
Mail list logo
