UV radiation causes dimerization of adjacent pyrimidine bases in DNA
(see Fig. 1),
which can lead to proliferation or cell death. With means of QM/MM
methods, we want to investigate recognition,
binding and repair of this defect by photolyase, which is hardly understood by now.
The enzyme photolyase (PL) catalyzes monomerization of
the dimers by light-induced electron transfer from an FAD cofactor
to the dimer (see Fig. 2)
Quantum chemical calculations in vacuo indicate, that the C5-C5' bond
of the dimer is the first to split after electron transfer leading to an
anionic radical dimer intermediate.
The subsequent splitting of the C6-C6' bond is assumed to occur in a
thermal reaction catalyzed by the enzyme. Electron transfer from the
anionic pyrimidine back to the FAD cofactor finally restores the native
state of the DNA and the initial state of the photolyase.
As an alternative reaction path, a simultaneous splitting of both bonds
has also been proposed, as former quantum mechanical calculations in vacuo
have revealed a high activation barrier for the cleavage
of the anionic dimer radical.
Vibrational analysis
Time-resolved FTIR-spectroscopy is a promising approach to resolve the
discussion on possible reaction intermediates and reaction constants
by experimental means.
The isolated spectral positions and the large intensities of the C=O
stretching modes between 1600 and 1800 cm-1 (see Fig. 3) suggest that
they might represent suitable candidates for the desired marker
modes.
Our calculations are accompanied by experiments carried out by E.
Schleicher and G. Richter in the group of A. Bacher
(
Biochemical
Institute, TU München).
#
# Mitarbeiter auflisten
#
$query='SELECT mitarbeiter_id, mitarbeiter.www_privat_lokal, mitarbeiter.vorname, mitarbeiter.name, mitarbeiter.id ';
$query.='FROM projektmitarbeiter, mitarbeiter ';
$query.='WHERE projektmitarbeiter.projekt_id=22';
$query.=' AND mitarbeiter.id=projektmitarbeiter.mitarbeiter_id';
$mnum=abfrage($query,$TBMIT);
#echo $mnum;
if ($mnum==0)
{echo '';}
else
{
echo '
Coworkers:
';
for($i=0;$i<$mnum;$i++)
{
if (strlen($TBMIT[$i]["www_privat_lokal"])>1)
echo '
';
else
echo '';
echo strtr($TBMIT[$i]["vorname"],$trans).' '.strtr($TBMIT[$i]["name"],$trans).'';
}
echo "
\n";
}
# Auflistung der Kollaborationen
$query='SELECT * ';
#$query='SELECT projektkollaboration.id, projekt.id, projekt.titel_en, ';
#$query='SELECT projektkollaboration.projekt1_id ';
$query.='FROM projektkollaboration, projekt ';
$query.='WHERE ((projektkollaboration.projekt2_id=22';
$query.=' AND projekt.id=projektkollaboration.projekt1_id)';
$query.=' OR (projektkollaboration.projekt1_id=22';
$query.=' AND projekt.id=projektkollaboration.projekt2_id))';
$kolnum=abfrage($query,$TBKOL);
#echo $kolnum;
if($kolnum>0)
{
echo '
Related Projects:
';
for($i=0; $i<$kolnum; $i++)
{
#echo 'projektkollab-id:'.$TBKOL[$i][0];
echo '
';
echo strtr($TBKOL[$i]["titel_en"],$trans).'';
}
echo "
\n";
}
#
# Publikationen auflisten
#
$query='SELECT publikation.id, titel, datum, journal, autoren ';
$query.='FROM projektpublikation, publikation ';
$query.='WHERE projektpublikation.projekt_id=22';
$query.=' AND publikation.id=projektpublikation.publikation_id';
$query.=' ORDER BY datum DESC';
$pubnum=abfrage($query,$TBPUB);
#echo $pubnum;
if ($pubnum>0)
{
echo '
Publikationen:
';
for($i=0; $i<$pubnum; $i++)
{
echo '
"'.strtr($TBPUB[$i]["titel"],$trans).'"';
echo '
'. strtr($TBPUB[$i]["autoren"],$trans).'
';
echo '
'.strtr($TBPUB[$i]["journal"],$trans).'
';
echo '
Details';
echo '
';
}
echo "
\n";
}
?>