Stellenanzeige: Doktorand/in
Stellenanzeigen-Kennnummer: ????
Einrichtung: Institut für Anorganische Chemie
Ansprechpartner: Dr. B. Dittrich
Besetzungsdatum: 01.11.2007
Veröffentlichungsdatum: 25.09.2007
In der Arbeitsgruppe Birger Dittrich am Institut für Anorganische Chemie der Georg-August-Universität Göttingen ist ab 1. November eine Stelle einer/eines
Doktorandin/Doktoranden
- Entgeltgruppe 13 TV-L/2 -
mit einer regelmäßigen Arbeitszeit von 40 Stunden/Woche zu besetzen.
Die Stellenausschreibung in Englischer Sprache lautet wie folgt:
The project will investigate and focus on ‘middle sized’
molecules (about 50 – 100 non-hydrogen atoms). The phase problem of such
structures can still be solved with direct methods. With the invariom
approach it is possible to model such important fragments as sugars or
nucleic acids. The class of molecules that will be central to this part of
the project will be antibiotics from biological source. Target molecules,
for which a study seems promising or that are already under investigation,
are the original form of thiostrepton, where no coordinates were
deposited, nosiheptide, erythromycin, streptomycin and
vancomycin. Smaller molecules with antibacterial activity which are
already quite well studied are amoxicillin and other members of the
group of the penicillins, or more recent examples of the oxazolidinone class
like moxifloxacin, norfloxacin, enoxacin and ciprofloxacin that
inhibit peptide deformylase. As these examples show there is a large
group of molecules that would deserve a detailed electron density study.
It is anticipated that the time frame for this sub-project will be three years.
As the size of these molecules allows conventional methodology and approaches,
studying these systems will allow to gain practical experience and
theoretical knowledge that can be applied to bigger molecules at a later
stage. To have diffraction data of high quality available is necessary
for the research project.
Stellenanzeige: Post-Doktorand/in
Stellenanzeigen-Kennnummer: ????
Einrichtung: Institut für Anorganische Chemie
Ansprechpartner: Dr. B. Dittrich
Besetzungsdatum: 01.11.2007
Veröffentlichungsdatum: 25.09.2007
In der Arbeitsgruppe Birger Dittrich am Institut für Anorganische Chemie der Georg-August-Universität Göttingen sind ab 1. November eine Stelle einer/eines
Post-Doktorandin/Post-Doktoranden
- Entgeltgruppe 13 TV-L -
mit einer regelmäßigen Arbeitszeit von 40 Stunden/Woche zu besetzen.
Die Stellenausschreibung in Englischer Sprache lautet wie folgt:
This research project will be devoted
to further more fundamental methodological developments, including programming
work. In collaboration also with Prof. Dylan Jayatilaka the invariom
approach will be developed. The description of the electron density
via the multipole model will be replaced by a quantum chemical one; this
will allow to use the structure factors as providing only additional information
and to rely stronger on prior information. By replacing a model with a
limited number of parameters, the information of the scattering experiment
will be combined with an energy minimization of the system. This makes
obsolete the need for reducing the number of variables depending on the
number of structure factors available. The methodology is partly based
upon concepts introduced in 1998 by Jayatilaka and improved later.
Such wavefunction fitting using experimental information
promises to succeed in avoiding the shortcomings of the multiple model. A
main disadvantage of the multipole model is that the parameters do not express
any physical meaning. Calculation of physical properties requires that
approximate expressions using the parameterized electron density description
have to be evaluated. Invarioms could then be based on an electron
density description as it is used in quantum chemistry:
For macromolecules, for which the energy minimization
is not technically feasible due to the number of atoms, an approximate
electron density distribution could be obtained by least-squares fitting to
the experimental geometry without energy minimization of the wavefunction.
Based on such invariom based experimental wavefunction properties
like the electrostatic interaction energy, dipole and multipole moments and
the electrostatic potential could be obtained directly without the need to
simulate a diffraction experiment and structure factors. These aims can
not be fulfilled using the multipole formalism.
These works will require familiarity with the modern programming languages
PERL, C++ and FORTRAN95. Usually such expertise can not be
expected from a doctoral student. Apart from programming, knowledge in
crystallography will equally be required. The position will be available for three years.