14 research outputs found
Experimental evidence for Berry curvature multipoles in antiferromagnets
Berry curvature multipoles appearing in topological quantum materials have
recently attracted much attention. Their presence can manifest in novel
phenomena, such as nonlinear anomalous Hall effects (NLAHE). The notion of
Berry curvature multipoles extends our understanding of Berry curvature effects
on the material properties. Hence, research on this subject is of fundamental
importance and may also enable future applications in energy harvesting and
high-frequency technology. It was shown that a Berry curvature dipole can give
rise to a 2nd order NLAHE in materials of low crystalline symmetry. Here, we
demonstrate a fundamentally new mechanism for Berry curvature multipoles in
antiferromagnets that are supported by the underlying magnetic symmetries.
Carrying out electric transport measurements on the kagome antiferromagnet
FeSn, we observe a 3rd order NLAHE, which appears as a transverse voltage
response at the 3rd harmonic frequency when a longitudinal a.c. current drive
is applied. Interestingly, this NLAHE is strongest at and above room
temperature. We combine these measurements with a scaling law analysis, a
symmetry analysis, model calculations, first-principle calculations, and
magnetic Monte-Carlo simulations to show that the observed NLAHE is induced by
a Berry curvature quadrupole appearing in the spin-canted state of FeSn. At a
practical level, our study establishes NLAHE as a sensitive probe of
antiferromagnetic phase transitions in other materials, such as moir\'e
superlattices, two-dimensional van der Waal magnets, and quantum spin liquid
candidates, that remain poorly understood to date. More broadly, Berry
curvature multipole effects are predicted to exist for 90 magnetic point
groups. Hence, our work opens a new research area to study a variety of
topological magnetic materials through nonlinear measurement protocols
Entropy Beacon: A Hairpin-Free DNA Amplification Strategy for Efficient Detection of Nucleic Acids
Generating Giant Membrane Vesicles from Live Cells with Preserved Cellular Properties
Biomimetic giant membrane vesicles, with size and lipid compositions comparable to cells, have been recognized as an attractive experimental alternative to living systems. Due to the similarity of their membrane structure to that of body cells, cell-derived giant plasma membrane vesicles have been used as a membrane model for studying lipid/protein behavior of plasma membranes. However, further application of biomimetic giant membrane vesicles has been hampered by the side-effects of chemical vesiculants and the utilization of osmotic buffer. We herein develop a facile strategy to derive giant membrane vesicles (GMVs) from mammalian cells in biofriendly medium with high yields. These GMVs preserve membrane properties and adaptability for surface modification and encapsulation of exogenous molecules, which would facilitate their potential biological applications. Moreover, by loading GMVs with therapeutic drugs, GMVs could be employed for drug transport to tumor cells, which represents another step forward in the biomedical application of giant membrane vesicles. This study highlights biocompatible GMVs with biomimicking membrane surface properties and adaptability as an ideal platform for drug delivery strategies with potential clinical applications
Biostable L‑DNAzyme for Sensing of Metal Ions in Biological Systems
DNAzymes, an important type of metal
ion-dependent functional nucleic
acid, are widely applied in bioanalysis and biomedicine. However,
the use of DNAzymes in practical applications has been impeded by
the intrinsic drawbacks of natural nucleic acids, such as interferences
from nuclease digestion and protein binding, as well as undesired
intermolecular interactions with other nucleic acids. On the basis
of reciprocal chiral substrate specificity, the enantiomer of D-DNAzyme,
L-DNAzyme, could initiate catalytic cleavage activity with the same
achiral metal ion as a cofactor. Meanwhile, by using the advantage
of nonbiological L-DNAzyme, which is not subject to the interferences
of biological matrixes, as recognition units, a facile and stable
L-DNAzyme sensor was proposed for sensing metal ions in complex biological
samples and live cells
Engineering a 3D DNA-Logic Gate Nanomachine for Bispecific Recognition and Computing on Target Cell Surfaces
Among
the vast number of recognition molecules, DNA aptamers generated
from cell-SELEX exhibit unique properties for identifying cell membrane
biomarkers, in particular protein receptors on cancer cells. To integrate
all recognition and computing modules within a single structure, a
three-dimensional (3D) DNA-based logic gate nanomachine was constructed
to target overexpressed cancer cell biomarkers with bispecific recognition.
Thus, when the Boolean operator “AND” returns a true
value, it is followed by an “ON” signal when the specific
cell type is presented. Compared with freely dispersed double-stranded
DNA (dsDNA)-based molecular circuits, this 3D DNA nanostructure, termed
DNA-logic gate triangular prism (TP), showed better identification
performance, enabling, in turn, better molecular targeting and fabrication
of recognition nanorobotics
Fluorescence Resonance Energy Transfer-Based DNA Nanoprism with a Split Aptamer for Adenosine Triphosphate Sensing in Living Cells
We have developed
a DNA nanoprobe for adenosine triphosphate (ATP)
sensing in living cells, based on the split aptamer and the DNA triangular
prism (TP). In which nucleic acid aptamer was split into two fragments,
the stem of the split aptamer was respectively labeled donor and acceptor
fluorophores that underwent a fluorescence resonance energy transfer
if two ATP molecules were bound as target molecule to the recognition
module. Hence, ATP as a target induced the self-assembly of split
aptamer fragments and thereby brought the dual fluorophores into close
proximity for high fluorescence resonance energy transfer (FRET) efficiency.
In the in vitro assay, an almost 5-fold increase in <i>F</i><sub>A</sub>/<i>F</i><sub>D</sub> signal was observed,
the fluorescence emission ratio was found to be linear with the concentration
of ATP in the range of 0.03–2 mM, and the nanoprobe was highly
selective toward ATP. For the strong protecting capability to nucleic
acids from enzymatic cleavage and the excellent biocompatibility of
the TP, the DNA TP nanoprobe exhibited high cellular permeability,
fast response, and successfully realized “FRET-off”
to “FRET-on” sensing of ATP in living cells. Moreover,
the intracellular imaging experiments indicated that the DNA TP nanoprobe
could effectively detect ATP and distinguish among changes of ATP
levels in living cells. More importantly, using of the split aptamer
and the FRET-off to FRET-on sensing mechanism could efficiently avoid
false-positive signals. This design provided a strategy to develop
biosensors based on the DNA nanostructures for intracellular molecules
analysis