|
Visualizing Ligand Molecules
in Twilight Electron Density
Christian X.
Weichenbergera*,
Edwin
Pozharskib*
and
Bernhard
Ruppc
aCenter
for Biomedicine,
European
Academy of Bozen/Bolzano (EURAC),
Viale Druso 1,
Bozen/Bolzano,
I-39100,
Italy,
bUniversity
of Maryland,
Baltimore,
MD,
USA,
and ck.k.
Hofkristallamt,
991 Audrey
Place,
Vista,
CA,
92084,
USA
Correspondence email:
Christian.Weichenberger@eurac.edu;
epozh001@umaryland.edu
Synopsis
We present a software
script for facilitating analysis and visual inspection of ligand
molecules in context of the electron density maps calculated from
experimental data associated with protein structures determined
by X-ray crystallography.
Original Abstract (2013)
Three-dimensional models of protein structures
determined by X-ray crystallography are based on the
interpretation of experimentally derived electron density maps.
The real-space correlation coefficient (RSCC)
provides an easily comprehensible, objective measure for
residue-based fit of atom coordinates with electron density.
Among protein structure models, protein-ligand complexes are of
special interest, given their contribution to understanding the
molecular underpinnings of biological activity and to drug
design. For consumers of such models it is not trivial to
determine the degree to which ligand structure modelling is
biased by subjective electron density interpretation. We present
a standalone script, Twilight, for analysis, visualization, and annotation of a
pre-filtered set of 2,815 protein/ligand complexes deposited
with the PDB as of January 15, 2012, with ligand
RSCC values that are
below a threshold of 0.6. The script runs on various platforms
and is available for download at
https://www.ruppweb.org/twilight/.
Download this
Acta Crystallographica F paper
and its companion in
Acta Crystallographica D
describing the actual findings from the IUCr web site
(preferred) or
request a link by email. Please read also the editorial
Expectation bias and information content
Z. Dauter,
M. S. Weiss,
H. Einspahr and
E. N. Baker,
Acta Crystallogr. D69, 141 (2013).
The
TWILIGHT GUI tool itself has been
discontinued - but you can
download sortable Excel tables of the small molecule
LIGAND and
PEPTIDE collections.
|
Twilight
(I)
Twilight reloaded: The peptide experience |
|
Techniques, tools and best practices for
ligand electron-density analysis and results from their application
to deposited crystal structures.
E. Pozharski,
C. X. Weichenberger and
B. Rupp,
Acta Crystallogr D69, 150-167 (2013)
Visualizing Ligand
Molecules in Twilight Electron Density.
C. X. Weichenberger,
E. Pozharski and
B. Rupp,
Acta Crystallogr. F69(2), 195-200(2013)
Twilight reloaded: The Peptide Experience.
C. X. Weichenberger, E. Pozharski, B. Rupp. Acta Crystallogr.
D73, 211-222 (2017). Extension of peptide
ligands with a composite score. Tables only, not compatible with
Twilight GUI.
2018-2020 Twilight reloaded (peptide) files,
cumulative: pepligands-2020-01-15.tsv
|
|
Download
program Change
Log |
|
A new
Twilight GUI, necessary due
to SSL requirements and changes in the fetch destination for PDB data
files, needs to be
downloaded from here.
The old 2012 version is still available
here.
Here is the readme file for installing
Twilight and the
update info. |
|
Data files -> Change
Log |
|
The Twilight program distribution comes packaged with
a data file current to the respective revision year (i.e., the current
2018 Twilight program distribution includes data only
up to 2018, and you need to also download the latest complete data file.
Note that there are changes (See Change Log)
to the archiving and possible differences on entry availibility due to
retirement of the Uppsala EDS.
The complete data file contains data up to the specified release
date, whereas the yearly data file only contains PDB entries that have
become available between the previous update's release date
and the current release date.
NOTE: The data files are .bz2 compressed files- please
unzip them before starting TWILIGHT
Here is the
readme file for installing
Twilight |
|
My
texbook |
|
A useful resource if you want to learn more about
protein crystallography, ligand structures, and structure validation |
|
For now |
|
You can still use the web tutorial for free! |
|