11 research outputs found
Wachstumsminderung
X-ray absorption near edge structure (XANES) analysis in combination with synchrotron radiation induced total reflection X-ray fluorescence (SR-TXRF) acquisition was used to determine the oxidation state of Fe in human cancer cells and simultaneously their elemental composition by applying a simple sample preparation procedure consisting of pipetting the cell suspension onto the quartz reflectors.
XANES spectra of several inorganic and organic iron compounds were recorded and compared to that of different cell lines. The XANES spectra of cells, independently from the phase of cell growth and cell type were very similar to that of ferritin, the main Fe store within the cell. The spectra obtained after CoCl2 or NiCl2 treatment, which could mimic a hypoxic state of cells, did not differ noticeably from that of the ferritin standard. After 5-fluorouracil administration, which could also induce an oxidative-stress in cells, the absorption edge position was shifted toward higher energies representing a higher oxidation state of Fe. Intense treatment with antimycin A, which inhibits electron transfer in the respiratory chain, resulted in minor changes in the spectrum, resembling rather the N-donor Fe-,′-dipyridyl complex at the oxidation energy of Fe(III), than ferritin. The incorporation of Co and Ni in the cells was followed by SR-TXRF measurements
Tuning plasmonic field enhancement and transients by far-field coupling between nanostructures
We study how the collective effects of nanoparticles arranged in rectangular
arrays influence their temporal plasmon response and field enhancement
property. By systematically changing the lattice constant for arrays containing
identical metal nanorods, we experimentally demonstrate how grating induced
effects affect the position and, more importantly, the broadening of extinction
spectra. We correlate these effects with the achievable field enhancement and
the temporal duration of plasmon transients and formulate criteria for the
generation of enhanced few-cycle localized plasmon oscillations.Comment
Molecular interactions between DPPC and morphine derivatives: a DSC and EPR study
The interaction between different morphine derivatives (morphine, codeine, N-methyl-morphine, N-methyl-codeine)
and a-L-dipalmitoyl phosphatidylcholine (DPPC) liposomes was studied with differential scanning calorimetry (DSC)
and electron paramagnetic resonance (EPR) spectroscopy. Small unilamellar DPPC-liposomes with the given
morphine-derivative were prepared by sonication. The size distribution of liposomes was checked by dynamic light
scattering (DLS). The amount of entrapped morphine was determined spectrophotometrically. Our results indicate that
the morphine and its derivatives principally interact with the lipid head groups, and this interaction leads to a decrease
in the mobility of the polar head groups, especially in case of codeine and N-methyl-codeine.
# 2002 Elsevier Science B.V. All rights reserved
Studies on molecular interactions between nalidixic acid and liposomes
The interaction between nalidixic acid sodium salt (NANa) and liposomes prepared from alfa-l-dipalmitoyl-phosphatidylcholine
(DPPC) or from its binary mixture with dioleoyl-phosphatidylcholine (DOPC)was studied with differential scanning calorimetry
(DSC) and electron paramagnetic resonance (EPR) spectroscopy. We evaluated the role of broadband ultraviolet-B (UV-B)
irradiation on the molecular interactions between the lipids and the NANa, and determined the decay-kinetics of the incorporated
spin labeled fatty-acid free radicals. Multilamellar and unilamellar vesicles were prepared by sonication and extrusion. The
entrapment efficiencies were determined spectrophotometrically. The size-distribution of the liposomes and its change in time
was checked by dynamic light scattering (DLS). Our results indicate thatNANa mainly interacts with lipid head groups. However,
its effect and presumably the formation of the free radicals, induced by broadband ultraviolet-B, is not localized only to the head
group region of the lipid molecules. Depending on DOPC content, interaction between the NANa and the lipids modifies the
phase-transition parameters of the liposome dispersions