2 research outputs found
Complete Exchange of the Hydrophobic Dispersant Shell on Monodisperse Superparamagnetic Iron Oxide Nanoparticles
High-temperature synthesized monodisperse
superparamagnetic iron
oxide nanoparticles are obtained with a strongly bound ligand shell
of oleic acid and its decomposition products. Most applications require
a stable presentation of a defined surface chemistry; therefore, the
native shell has to be completely exchanged for dispersants with irreversible
affinity to the nanoparticle surface. We evaluate by attenuated total
reflectance−Fourier transform infrared spectroscopy (ATR−FTIR)
and thermogravimetric analysis/differential scanning calorimetry (TGA/DSC)
the limitations of commonly used approaches. A mechanism and multiple
exchange scheme that attains the goal of complete and irreversible
ligand replacement on monodisperse nanoparticles of various sizes
is presented. The obtained hydrophobic nanoparticles are ideally suited
for magnetically controlled drug delivery and membrane applications
and for the investigation of fundamental interfacial properties of
ultrasmall core–shell architectures
pH and Potential Transients of the <i>bc</i><sub>1</sub> Complex Co-Reconstituted in Proteo-Lipobeads with the Reaction Center from Rb. sphaeroides
His-tag
technology is employed to bind membrane proteins, such
as the <i>bc</i><sub>1</sub> complex and the reaction center
(RC) from Rhodobacter sphaeroides,
to spherical as well as planar surfaces in a strict orientation. Subsequently,
the spherical and planar surfaces are subjected to in situ dialysis
to form proteo-lipobeads (PLBs) and protein-tethered bilayer membranes,
respectively. PLBs based on Ni-nitrileotriacetic acid-functionalized
agarose beads that have diameters ranging from 50 to 150 μm
are used to assess proton release and membrane potential parameters
by confocal laser-scanning microscopy. The pH and potential transients
are thus obtained from <i>bc</i><sub>1</sub> activated by
the RC. To assess the turnover of <i>bc</i><sub>1</sub> excited
by the RC in a similar setting, we used the planar surface of an attenuated
total reflection crystal modified with a thin gold layer to carry
out time-resolved surface-enhanced IR absorption spectroscopy triggered
by flash lamp excitation. The experiments suggest that both proteins
interact in a cyclic manner in both environments. The activity of
the proteins seems to be preserved in the same manner as that in chromatophores
or reconstituted in liposomes