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Journal of the American Chemical Society Aug 2016Under physiological conditions, protein oxidation and misfolding occur with very low probability and on long times scales. Single-molecule techniques provide the ability...
Under physiological conditions, protein oxidation and misfolding occur with very low probability and on long times scales. Single-molecule techniques provide the ability to distinguish between properly folded and damaged proteins that are otherwise masked in ensemble measurements. However, at physiological conditions these rare events occur with a time constant of several hours, inaccessible to current single-molecule approaches. Here we present a magnetic-tweezers-based technique that allows, for the first time, the study of folding of single proteins during week-long experiments. This technique combines HaloTag anchoring, sub-micrometer positioning of magnets, and an active correction of the focal drift. Using this technique and protein L as a molecular template, we generate a magnet law by correlating the distance between the magnet and the measuring paramagnetic bead with unfolding/folding steps. We demonstrate that, using this magnet law, we can accurately measure the dynamics of proteins over a wide range of forces, with minimal dispersion from bead to bead. We also show that the force calibration remains invariant over week-long experiments applied to the same single proteins. The approach demonstrated in this Article opens new, exciting ways to examine proteins on the "human" time scale and establishes magnetic tweezers as a valuable technique to study low-probability events that occur during protein folding under force.
Topics: Bacterial Proteins; Magnets; Mechanical Phenomena; Protein Folding
PubMed: 27409974
DOI: 10.1021/jacs.6b05429 -
International Journal of Nanomedicine 2020Although the incidence of central nervous system injuries has continued to rise, no promising treatments have been elucidated. Erythropoietin plays an important role in... (Review)
Review
Although the incidence of central nervous system injuries has continued to rise, no promising treatments have been elucidated. Erythropoietin plays an important role in neuroprotection and neuroregeneration as well as in erythropoiesis. Moreover, the current worldwide use of erythropoietin in the treatment of hematologic diseases allows for its ready application in patients with central nervous system injuries. However, erythropoietin has a very short therapeutic time window (within 6-8 hours) after injury, and it has both hematopoietic and nonhematopoietic receptors, which exhibit heterogenic and phylogenetic differences. These differences lead to limited amounts of erythropoietin binding to in situ erythropoietin receptors. The lack of high-quality evidence for clinical use and the promising results of in vitro/in vivo models necessitate fast targeted delivery agents such as nanocarriers. Among current nanocarriers, noncovalent polymer-entrapping or polymer-adsorbing erythropoietin obtained by nanospray drying may be the most promising. With the incorporation of magnetic nanocarriers into an erythropoietin polymer, spatiotemporal external magnetic navigation is another area of great interest for targeted delivery within the therapeutic time window. Intravenous administration is the most readily used route. Manufactured erythropoietin nanocarriers should be clearly characterized using bioengineering analyses of the in vivo size distribution and the quality of entrapment or adsorption. Further preclinical trials are required to increase the therapeutic bioavailability (in vivo biological identity alteration, passage through the lung capillaries or the blood brain barrier, and timely degradation followed by removal of the nanocarriers from the body) and decrease the adverse effects (hematological complications, neurotoxicity, and cytotoxicity), especially of the nanocarrier.
Topics: Animals; Drug Carriers; Erythropoietin; Humans; Magnets; Trauma, Nervous System
PubMed: 33311979
DOI: 10.2147/IJN.S287456 -
Magnetic Resonance in Medicine Jan 2021To design a low-cost, portable permanent magnet-based MRI system capable of obtaining in vivo MR images within a reasonable scan time.
PURPOSE
To design a low-cost, portable permanent magnet-based MRI system capable of obtaining in vivo MR images within a reasonable scan time.
METHODS
A discretized Halbach permanent magnet array with a clear bore diameter of 27 cm was designed for operation at 50 mT. Custom-built gradient coils, RF coil, gradient amplifiers, and RF amplifier were integrated and tested on both phantoms and in vivo.
RESULTS
Phantom results showed that the gradient nonlinearity in the y-direction and z-direction was less than 5% over a 15-cm FOV and did not need correcting. For the x-direction, it was significantly greater, but could be partially corrected in postprocessing. Three-dimensional in vivo scans of the brain of a healthy volunteer using a turbo spin-echo sequence were acquired at a spatial resolution of 4 × 4 × 4 mm in a time of about 2 minutes. The T -weighted and T -weighted scans showed a good degree of tissue contrast. In addition, in vivo scans of the knee of a healthy volunteer were acquired at a spatial resolution of about 3 × 2 × 2 mm within 12 minutes to show the applicability of the system to extremity imaging.
CONCLUSION
This work has shown that it is possible to construct a low-field MRI unit with hardware components costing less than 10 000 Euros, which is able to acquire human images in vivo within a reasonable data-acquisition time. The system has a high degree of portability with magnet weight of approximately 75 kg, gradient and RF amplifiers each 15 kg, gradient coils 10 kg, and spectrometer 5 kg.
Topics: Brain; Extremities; Humans; Magnetic Resonance Imaging; Magnets; Phantoms, Imaging
PubMed: 32627235
DOI: 10.1002/mrm.28396 -
PLoS Biology Aug 2016
Topics: Animals; Bacterial Physiological Phenomena; Caenorhabditis elegans; Chiroptera; Earth, Planet; Ferrosoferric Oxide; Humans; Magnetic Phenomena; Magnets; Spatial Navigation
PubMed: 27551729
DOI: 10.1371/journal.pbio.2000613 -
Sensors (Basel, Switzerland) Jun 2023The safety of railway transportation is crucial to social and economic development. Therefore, real-time monitoring of the rail is particularly necessary. The current...
The safety of railway transportation is crucial to social and economic development. Therefore, real-time monitoring of the rail is particularly necessary. The current track circuit structure is complex and costly, posing challenges to monitoring broken tracks using alternative methods. As a non-contact detection technology with a lower environmental impact, electromagnetic ultrasonic transducers (EMATs) have become a concern. However, traditional EMATs have problems such as low conversion efficiency and complex modes, which can limit their effectiveness for long-distance monitoring. Therefore, this study introduces a novel dual-magnet phase-stacked EMAT (DMPS-EMAT) design comprising two magnets and a dual-layer winding coil arrangement. The magnets are positioned at a distance equal to the wavelength of the A0 wave from each other, while the center distance between the two sets of coils beneath the transducer is also equal to the wavelength. After analyzing the dispersion curves of the rail waist, it was determined that the optimal frequency for long-distance rail monitoring is 35 kHz. At this frequency, adjusting the relative positions of the two magnets and the coil directly underneath to be one A0 wavelength can effectively excite a constructive interference A0 wave in the rail waist. The simulation and experimental results show that DMPS-EMAT excited a single-mode A0 wave, resulting in a 1.35-times increase in amplitude.
Topics: Magnets; Computer Simulation; Technology; Transducers; Transportation
PubMed: 37420749
DOI: 10.3390/s23125583 -
Sensors (Basel, Switzerland) 2011Thick-film magnetoelastic sensors vibrate mechanically in response to a time varying magnetic excitation field. The mechanical vibrations of the magnetostrictive... (Review)
Review
Thick-film magnetoelastic sensors vibrate mechanically in response to a time varying magnetic excitation field. The mechanical vibrations of the magnetostrictive magnetoelastic material launch, in turn, a magnetic field by which the sensor can be monitored. Magnetic field telemetry enables contact-less, remote-query operation that has enabled many practical uses of the sensor platform. This paper builds upon a review paper we published in Sensors in 2002 (Grimes, C.A.; et al. Sensors 2002, 2, 294-313), presenting a comprehensive review on the theory, operating principles, instrumentation and key applications of magnetoelastic sensing technology.
Topics: Animals; Biosensing Techniques; Blood Coagulation; Elasticity; Humans; Magnetics; Models, Theoretical; Signal Processing, Computer-Assisted
PubMed: 22163768
DOI: 10.3390/s110302809 -
The Journal of Physiology Apr 2016The standard method of magnetic nerve activation using pulses of high current in coils has drawbacks of high cost, high electrical power (of order 1 kW), and limited...
KEY POINTS
The standard method of magnetic nerve activation using pulses of high current in coils has drawbacks of high cost, high electrical power (of order 1 kW), and limited repetition rate without liquid cooling. Here we report a new technique for nerve activation using high speed rotation of permanent magnet configurations, generating a sustained sinusoidal electric field using very low power (of order 10 W). A high ratio of the electric field gradient divided by frequency is shown to be the key indicator for nerve activation at high frequencies. Activation of the cane toad sciatic nerve and attached gastrocnemius muscle was observed at frequencies as low as 180 Hz for activation of the muscle directly and 230 Hz for curved nerves, but probably not in straight sections of nerve. These results, employing the first prototype device, suggest the opportunity for a new class of small low-cost magnetic nerve and/or muscle stimulators.
ABSTRACT
Conventional pulsed current systems for magnetic neurostimulation are large and expensive and have limited repetition rate because of overheating. Here we report a new technique for nerve activation, namely high-speed rotation of a configuration of permanent magnets. Analytical solutions of the cable equation are derived for the oscillating electric field generated, which has amplitude proportional to the rotation speed. The prototype device built comprised a configuration of two cylindrical magnets with antiparallel magnetisations, made to rotate by interaction between the magnets' own magnetic field and three-phase currents in coils mounted on one side of the device. The electric field in a rectangular bath placed on top of the device was both numerically evaluated and measured. The ratio of the electric field gradient on frequency was approximately 1 V m(-2) Hz(-1) near the device. An exploratory series of physiological tests was conducted on the sciatic nerve and attached gastrocnemius muscle of the cane toad (Bufo marinus). Activation was readily observed of the muscle directly, at frequencies as low as 180 Hz, and of nerves bent around insulators, at frequencies as low as 230 Hz. Nerve-muscles, with the muscle elevated to avoid its direct activation, were occasionally activated, possibly in the straight section of the nerve, but more likely in the nerve where it curved up to the muscle, at radius of curvature 10 mm or more, or at the nerve end. These positive first results suggest the opportunity for a new class of small, low-cost devices for magnetic stimulation of nerves and/or muscles.
Topics: Animals; Bufo marinus; Electromagnetic Fields; Magnets; Muscle, Skeletal; Sciatic Nerve; Transcutaneous Electric Nerve Stimulation
PubMed: 26661902
DOI: 10.1113/JP271743 -
Pediatrics and Neonatology Oct 2020The ingestion of multiple magnets may lead to severe complications including bowel obstruction, perforation, fistula, peritonitis, short bowel syndrome, life-threatening...
BACKGROUND
The ingestion of multiple magnets may lead to severe complications including bowel obstruction, perforation, fistula, peritonitis, short bowel syndrome, life-threatening injuries, and even death. The annual case number of high-powered neodymium magnets ingestion has been increasing in the western world and the dearth of available data demonstrates that this issue has been neglected in Taiwan.
METHODS
We searched the electronic medical records of our institution for patients younger than 18 years old who were diagnosed with, who had ever visited our emergency department, or been hospitalized for magnetic foreign body ingestion between January 2009 and March 2018. Demographic data including the number, shape, and size of magnets ingested, the clinical presentation, type of intervention, and complications were reviewed.
RESULTS
Thirteen patients who met the enrollment criteria were analyzed. One patient was documented between 2009 and 2013, and twelve were documented between January 2014 and March 2018. Five of the cases documented between 2014 and 2018 had ingested Buckyballs. The median age of the patients was 5 years. All of the patients with clinical symptoms had ingested more than one magnet and required endoscopic or surgical intervention. Bowel perforation or deep ulcer with impending perforation was found in three patients during surgery.
CONCLUSION
The number of children who visited our emergency department or were hospitalized due to the ingestion of magnets has increased recently. The presence of high power of neodymium magnets in many products increases the risk of ingesting multiple magnets resulting in serious complications. Therefore, stricter policies are needed to prevent children from obtaining products that contain magnets.
Topics: Child; Child, Preschool; Eating; Emergency Service, Hospital; Female; Foreign Bodies; Humans; Infant; Intestinal Perforation; Magnets; Male; Retrospective Studies
PubMed: 32682694
DOI: 10.1016/j.pedneo.2020.06.003 -
Sensors (Basel, Switzerland) Nov 2015A technology platform based on a remotely controlled and stepwise transport of an array arrangement of superparamagnetic beads (SPB) for efficient molecular uptake,... (Review)
Review
A technology platform based on a remotely controlled and stepwise transport of an array arrangement of superparamagnetic beads (SPB) for efficient molecular uptake, delivery and accumulation in the context of highly specific and sensitive analyte molecule detection for the application in lab-on-a-chip devices is presented. The near-surface transport of SPBs is realized via the dynamic transformation of the SPBs' magnetic potential energy landscape above a magnetically stripe patterned Exchange-Bias (EB) thin film layer systems due to the application of sub-mT external magnetic field pulses. In this concept, the SPB velocity is dramatically influenced by the magnitude and gradient of the magnetic field landscape (MFL) above the magnetically stripe patterned EB substrate, the SPB to substrate distance, the magnetic properties of both the SPBs and the EB layer system, respectively, as well as by the properties of the external magnetic field pulses and the surrounding fluid. The focus of this review is laid on the specific MFL design in EB layer systems via light-ion bombardment induced magnetic patterning (IBMP). A numerical approach is introduced for the theoretical description of the MFL in comparison to experimental characterization via scanning Hall probe microscopy. The SPB transport mechanism will be outlined in terms of the dynamic interplay between the EB substrate's MFL and the pulse scheme of the external magnetic field.
Topics: Biosensing Techniques; Magnetics; Magnets; Microfluidic Analytical Techniques; Nanotechnology
PubMed: 26580625
DOI: 10.3390/s151128854 -
Nature Communications Dec 2022Natural superlattice structures MnBiTe(BiTe) (n = 1, 2, ...), in which magnetic MnBiTe layers are separated by nonmagnetic BiTe layers, hold band topology, magnetism...
Natural superlattice structures MnBiTe(BiTe) (n = 1, 2, ...), in which magnetic MnBiTe layers are separated by nonmagnetic BiTe layers, hold band topology, magnetism and reduced interlayer coupling, providing a promising platform for the realization of exotic topological quantum states. However, their magnetism in the two-dimensional limit, which is crucial for further exploration of quantum phenomena, remains elusive. Here, complex ferromagnetic-antiferromagnetic coexisting ground states that persist down to the 2-septuple layers limit are observed and comprehensively investigated in MnBiTe (n = 1) and MnBiTe (n = 2). The ubiquitous Mn-Bi site mixing modifies or even changes the sign of the subtle interlayer magnetic interactions, yielding a spatially inhomogeneous interlayer coupling. Further, a tunable exchange bias effect, arising from the coupling between the ferromagnetic and antiferromagnetic components in the ground state, is observed in MnBiTe(BiTe) (n = 1, 2), which provides design principles and material platforms for future spintronic devices. Our work highlights a new approach toward the fine-tuning of magnetism and paves the way for further study of quantum phenomena in MnBiTe(BiTe) (n = 1, 2) as well as their magnetic applications.
Topics: Magnets; Bias
PubMed: 36496444
DOI: 10.1038/s41467-022-35184-7