5 research outputs found
Fano meets Stokes: Four-order-of-magnitude enhancement of asymmetric Brillouin light scattering spectra
Observation of Fano resonances in various physical phenomena is usually ascribed to the coupling of discrete states with background continuum, as it has already been reported for various physical phenomena. Here, we report on Fano lineshapes of nonthermal GHz phonons generated and observed with pumped Brillouin light scattering in gold-silicon thin membranes, overlapping the broad zero-shift background of yet questionable origin. The system's broken mid-plane symmetry enabled the generation of coherent quasi-symmetric and quasi-antisymmetric Lamb acoustic waves/phonons, leading to the four orders-of-magnitude enhancement of Brillouin light scattering. Notably, the membrane asymmetry resulted also in the mode-dependent Stokes and anti-Stokes Fano lineshapes asymmetry
Morphology and Magnetic Structure of the Ferritin Core during Iron Loading and Release by Magnetooptical and NMR Methods
Ferritins are proteins, which serve as
a storage and transportation capsule for iron inside living organisms.
Continuously charging the proteins with iron and releasing it from
the ferritin is necessary to assure proper management of these important
ions within the organism. On the other hand, synthetic ferritins have
great potential for biomedical and technological applications. In
this work, the behavior of ferritin during the processes of iron loading
and release was examined using multiplicity of the experimental technique.
The quality of the protein’s shell was monitored using circular
dichroism, whereas the average size and its distribution were estimated
from dynamic light scattering and transmission electron microscopy
images, respectively. Because of the magnetic behavior of the iron
mineral, a number of magnetooptical methods were used to gain information
on the iron core of the ferritin. Faraday rotation and magnetic linear
birefringence studies provide evidence that the iron loading and the
iron-release processes are not symmetrical. The spatial organization
of the mineral within the protein’s core changes depending
on whether the iron was incorporated into or removed from the ferritin’s
shell. Magnetic optical rotatory dispersion spectra exclude the contribution
of the Fe(II)-composed mineral, whereas joined magnetooptical and
nuclear magnetic resonance results indicate that no mineral with high
magnetization appear at any stage of the loading/release process.
These findings suggest that the iron core of loaded/released ferritin
consists of single-phase, that is, ferrihydrite. The presented results
demonstrate the usefulness of emerging magnetooptical methods in biomedical
research and applications
Temperature dependent FCS studies using a long working distance objective: Viscosities of supercooled liquids and particle size
In this work, we describe new experimental setups for Fluorescence Correlation Spectroscopy (FCS) where a long working distance objective is used. Using these setups, FCS measurements in a broad temperature range for a small sample volume of about 50 μlcan be performed. The use of specially designed cells and a dry long working distance objective was essential for avoiding temperature gradients in the sample. The performance of the new setups and a traditional FCS setup with immersion objectives is compared. The FCS data in combination with the Stokes-Einstein (SE) relation were used to obtain the values of the nanoviscosity of a fluid. We show for selected molecular van der Waals supercooled liquids that despite the fact that in these systems, a characteristic length scale can be defined, the nanoviscosity obtained from FCS is in a very good agreement with the macroscopic (rheometric) viscosity of the sample in a broad temperature range. This result corroborates the applicability of the SE relation to supercooled liquids at temperatures above 1.2 Tg. We also show that the temperature dependent size of thermoresponsive microgel particles can be determined by FCS using the designed cells and a long working distance objective in a broader size range without a need to use the correction procedure since the size correction is proportional to the square of the ratio of the hydrodynamic radius to the confocal volume size