3. Postere - rmr.medica.ro

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ignored or neglected due to the small dimensions
and slow evolution, or they are mistaken as easy
lesions.
We used THz spectroscopy to differentiate between
BCC and normal skin slices. Normal skin
and BCC samples with a surface of ~1 cm 2 were
embedded in paraffi n. THz spectroscopy experiments
were performed on 5, 10, 15 and 20 μ slices
mounted on 0.13-0.17 mm thick glass slides. In order
to establish the correlation between THz absorption
and tissue structure, we also performed a
histopathological analysis of the samples. Our results
show that, independent of thickness, the BCC
slides have an increased THz absorption in comparison
to the normal skin slides. The normal skin
dermis presents a higher THz absorption than the
normal skin hypodermis slides. Also, the solid BCC
samples present a higher THz absorption than BCC
samples with cystic aspects. The differences of absorption
between solid and cystic BCC samples are
a consequence of the differences in cell density.
Interacti ons of normal and mutant human
TPH2 with substrates and inhibitors by
molecular docking
Octavian Calborean, Maria Mernea,
Dan Florin Mihailescu
University of Bucharest, Faculty of Biology, Department
of Anatomy, Animal Physiology and Biophysics
Tryptophan hydroxylase (TPH) catalyzes the
hydroxylation of L-tryptophan into 5-hydroxytryptophan.
This is the fi rst and rate-limiting step in
the serotonin synthesis pathway. There are two human
isoforms of TPH: TPH1, primarily expressed
in the enterochromaffi n cells of the gastrointestinal
tract, and TPH2, expressed exclusively in neuronal
cells. The active form for both enzymes is the tetrameric
one. Single nucleotide polymorphisms of
TPH2 gene (Pro206Ser and Arg441His) are associated
with depression and bipolar disorder, as well
as sleep disorders and substance abuse. The 3D
structure of human TPH2 has not been experimentally
determined yet. Our objective was to investigate
the TPH2 binding physiology at the molecular
level and to explain the impact of mutations on
TPH2 interaction with substrates and the interaction
with inhibitors using molecular dynamics and
docking techniques. We used homology modeling
to build structural models of the tetramers of wild
type and mutant (Pro206Ser and Arg441His) TPH2
with Fe 3+ bound to 3 water molecules in the active
REVISTA MEDICALÅ ROMÂNÅ – VOLUMUL LIX, NR. 2, An 2012
catalytic site. We used as templates the known crystal
structures of several related enzymes: human
TPH1 with Fe 3+ bound to 3 water molecules and
dihydrobiopterine; rat and human phenylalanine
hydroxylases. We then refi ned the three models by
more than 10 nanoseconds of molecular dynamics
in aqueous solutions. We then docked the minimized
structures of tryptophan, tetrahydrobiopterin
(BH4), and two known inhibitors of human TPH1
(LP-533401 si LP-615819) to the TPH2 models.
For each docking of substrate of inhibitor, we extracted
10 binding positions for which we calculated
the interaction energies. Out of the 10 positions
we chose the one most favourable sterically and we
analyzed the details of its binding. The two mutant
models bind tryptophan and BH4 stronger than the
wild type, in accord with the experimentally determined
Michaelis constants. In the case of the two
inhibitors, we observed that LP-615819 binding to
TPH2 is less favourable energetically and sterically
then LP-533401. This result is in good correlation
with the experimentally determined binding constant
of LP-615819 to TPH1, that is less specifi c
than that of LP-533401.
Identi fi cati on of potenti al toxic eff ects of
up-converti ng nanoparti cles
Livia Petrescu 1 , Oti lia Cinteza 2 , Tudor Rosu 2 ,
Serban Georgescu 3 , Dan Florin Mihailescu 1
1 University of Bucharest, Faculty of Biology,
D.A.F.A.B. Department
2 University of Bucharest, Faculty of Chemistry,
3 Nati onal Insti tute for Laser,
Plasma and Radiati on Physics
One of the most important achievements of nanotechnology
is the luminescent nanoparticles used
for sensitive biological detection applications (immunoassay).
Different types of fl uorescent labels,
such as organic fl uorescent markers, green fl uorescent
protein (GFP) and lanthanide chelates, have
been reported. Compared to classical down conversion
markers, the fl uorescence of lanthanide chelates
have specifi c advantages. We can enumerate
their higher photostability and stronger luminescence.
We synthesized and characterized several categories
of up-converting nanoparticles: Y 2 O 3 :
Er +3 :Yb +3 , YVO 4 : Er +3 :Yb +3 , NaYF 4 : Er +3 :Yb +3 .
Of these NaYF 4 : Er +3 :Yb +3 proved to be the most
effi cient and suitable for bio<strong>medica</strong>l applications.
Synthesis of NaYF4:Yb:Er nanoparticles was
performed using hydrothermal method. Method