scholarly journals Probing the stability and magnetic properties of magnetosome chains in freeze-dried magnetotactic bacteria

2020 ◽  
Vol 2 (3) ◽  
pp. 1115-1121
Author(s):  
Philipp Bender ◽  
Lourdes Marcano ◽  
Iñaki Orue ◽  
Diego Alba Venero ◽  
Dirk Honecker ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetite Nanoparticles ◽  
Magnetotactic Bacteria ◽  
Magnetic Compass ◽  
High Quality ◽  
Magnetospirillum Gryphiswaldense ◽  
Freeze Dried ◽  
A Chain ◽  
The Stability

Magnetospirillum gryphiswaldense biosynthesize high quality magnetite nanoparticles, called magnetosomes, and arrange them into a chain that behaves like a magnetic compass.

scholarly journals Configuration of the magnetosome chain: a natural magnetic nanoarchitecture

Nanoscale ◽  
2018 ◽  
Vol 10 (16) ◽  
pp. 7407-7419 ◽  
Author(s):  
I. Orue ◽  
L. Marcano ◽  
P. Bender ◽  
A. García-Prieto ◽  
S. Valencia ◽  
...  
Keyword(s):  
Magnetite Nanoparticles ◽  
Magnetic Compass ◽  
Magnetospirillum Gryphiswaldense ◽  
A Chain

Magnetospirillum gryphiswaldense is a microorganism with the ability to biomineralize magnetite nanoparticles, called magnetosomes, and arrange them into a chain that behaves like a magnetic compass.

scholarly journals Biologically controlled synthesis and assembly of magnetite nanoparticles

2015 ◽  
Vol 181 ◽  
pp. 71-83 ◽  
Author(s):  
Mathieu Bennet ◽  
Luca Bertinetti ◽  
Robert K. Neely ◽  
Andreas Schertel ◽  
André Körnig ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetite Nanoparticles ◽  
Super Resolution ◽  
Magnetotactic Bacteria ◽  
Biological Macromolecules ◽  
Free Standing ◽  
Magnetic Dipoles ◽  
Closed Ring ◽  
Major Player ◽  
Ring Structures

Magnetite nanoparticles have size- and shape-dependent magnetic properties. In addition, assemblies of magnetite nanoparticles forming one-dimensional nanostructures have magnetic properties distinct from zero-dimensional or non-organized materials due to strong uniaxial shape anisotropy. However, assemblies of free-standing magnetic nanoparticles tend to collapse and form closed-ring structures rather than chains in order to minimize their energy. Magnetotactic bacteria, ubiquitous microorganisms, have the capability to mineralize magnetite nanoparticles, the so-called magnetosomes, and to direct their assembly in stable chainsviabiological macromolecules. In this contribution, the synthesis and assembly of biological magnetite to obtain functional magnetic dipoles in magnetotactic bacteria are presented, with a focus on the assembly. We present tomographic reconstructions based on cryo-FIB sectioning and SEM imaging of a magnetotactic bacterium to exemplify that the magnetosome chain is indeed a paradigm of a 1D magnetic nanostructure, based on the assembly of several individual particles. We show that the biological forces are a major player in the formation of the magnetosome chain. Finally, we demonstrate by super resolution fluorescence microscopy that MamK, a protein of the actin family necessary to form the chain backbone in the bacteria, forms a bundle of filaments that are not only found in the vicinity of the magnetosome chain but are widespread within the cytoplasm, illustrating the dynamic localization of the protein within the cells. These very simple microorganisms have thus much to teach us with regards to controlling the design of functional 1D magnetic nanoassembly.

scholarly journals Synthesis and Magnetic Properties of a Superparamagnetic Nanocomposite “Pectin-Magnetite Nanocomposite”

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Jude Namanga ◽  
Josepha Foba ◽  
Derek Tantoh Ndinteh ◽  
Divine Mbom Yufanyi ◽  
Rui Werner Maçedo Krause
Keyword(s):  
Electron Microscopy ◽  
Magnetic Properties ◽  
Magnetite Nanoparticles ◽  
Quantum Interference ◽  
Size Control ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Freeze Dried ◽  
Drying Conditions

Magnetic nanocomposites composed of superparamagnetic magnetite nanoparticles in a pectin matrix were synthesized by an in situ coprecipitation method. The pectin matrix acted as a stabilizer and size control host for the magnetite nanoparticles (MNPs) ensuring particle size homogeneity. The effects of the different reactant ratios and nanocomposite drying conditions on the magnetic properties were investigated. The nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FT-IR) spectroscopy, and superconducting quantum interference device magnetometer (SQUID). Superparamagnetic magnetite nanoparticles with mean diameters of 9 and 13 nm were obtained, and the freeze-dried nanocomposites had a saturation magnetization of 54 and 53 emu/g, respectively.

Magnetic Bacteria as a Tool for Bioremediation of Heavy Metal Ion

2014 ◽  
Vol 955-959 ◽  
pp. 589-592
Author(s):  
Yi Ri Le Tu ◽  
Shingo Watanabe ◽  
Tatsuo Iwasa
Keyword(s):  
Heavy Metal ◽  
Magnetic Properties ◽  
Metal Ion ◽  
Heavy Metal Ions ◽  
Culture Media ◽  
Magnetotactic Bacteria ◽  
Pure Crystal ◽  
A Chain ◽  
Magnetospirillum Magnetotacticum ◽  
Saturation Remanence

Magnetotactic bacteria (MTB) are microorganism found in lake sediments and have a chain like organelle called magnetosome which is composed of highly pure crystal of magnetite (Fe3O4). We culturedMagnetospirillum magnetotacticum(MS-1) with culture media containing heavy metal ions such as Fe (standard media), Fe/Zn or Fe/Co and study on a possibility of MTB as a tool for bioremediation. In culture media containing Fe, Fe/Zn or Fe/Co, the growth rate of the bacteria was almost same. We measured the magnetic properties of the dried cells. The saturation magnetization (Ms) and the saturation remanence (Mr) of MS-1 cultured in Fe/Zn or Fe/Co media were decreased, but the coercivity (Hc) and the coercivity remanence (Hr) were increased from those of MS-1 cultured in the Fe media. The value ofMr/MsandHr/Hcwere ca. 0.5 and ca. 1.0, respectively. The changes in the magnetic properties of MS-1 cultured in Fe/Zn or Fe/Co media represent that MS-1 would take not only Fe, but also Zn or Co element in their environment. We discuss about a possible usage and advantages of MTB as a tool for bioremediation.

The Stability of the WHO Reference Thromboplastin NIBS & C 67/40

1979 ◽  
Vol 42 (04) ◽  
pp. 1135-1140 ◽  
Author(s):  
G I C Ingram
Keyword(s):  
Human Brain ◽  
Collaborative Study ◽  
Calibration Constant ◽  
Long Term Stability ◽  
Freeze Dried ◽  
Show Evidence ◽  
Human Material ◽  
Reference Preparation ◽  
The Stability

SummaryThe International Reference Preparation of human brain thromboplastin coded 67/40 has been thought to show evidence of instability. The evidence is discussed and is not thought to be strong; but it is suggested that it would be wise to replace 67/40 with a new preparation of human brain, both for this reason and because 67/40 is in a form (like Thrombotest) in which few workers seem to use human brain. A �plain� preparation would be more appropriate; and a freeze-dried sample of BCT is recommended as the successor preparation. The opportunity should be taken also to replace the corresponding ox and rabbit preparations. In the collaborative study which would be required it would then be desirable to test in parallel the three old and the three new preparations. The relative sensitivities of the old preparations could be compared with those found in earlier studies to obtain further evidence on the stability of 67/40; if stability were confirmed, the new preparations should be calibrated against it, but if not, the new human material should receive a calibration constant of 1.0 and the new ox and rabbit materials calibrated against that.The types of evidence available for monitoring the long-term stability of a thromboplastin are discussed.

Magnetic properties of bacterial magnetosomes and chemosynthesized magnetite nanoparticles

2008 ◽  
Vol 44 (2) ◽  
pp. 113-120 ◽  
Author(s):  
M. Timko ◽  
A. Dżarová ◽  
V. Závišová ◽  
M. Koneracká ◽  
A. Šprincová ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetite Nanoparticles

scholarly journals Coherent suppression of backscattering in optical microresonators

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Andreas Ø. Svela ◽  
Jonathan M. Silver ◽  
Leonardo Del Bino ◽  
Shuangyou Zhang ◽  
Michael T. M. Woodley ◽  
...  
Keyword(s):  
Quality Factor ◽  
Bulk Material ◽  
Near Field ◽  
High Quality Factor ◽  
Dual Frequency ◽  
High Quality ◽  
Frequency Combs ◽  
Optical Microresonators ◽  
Whispering Gallery ◽  
The Stability

AbstractAs light propagates along a waveguide, a fraction of the field can be reflected by Rayleigh scatterers. In high-quality-factor whispering-gallery-mode microresonators, this intrinsic backscattering is primarily caused by either surface or bulk material imperfections. For several types of microresonator-based experiments and applications, minimal backscattering in the cavity is of critical importance, and thus, the ability to suppress backscattering is essential. We demonstrate that the introduction of an additional scatterer into the near field of a high-quality-factor microresonator can coherently suppress the amount of backscattering in the microresonator by more than 30 dB. The method relies on controlling the scatterer position such that the intrinsic and scatterer-induced backpropagating fields destructively interfere. This technique is useful in microresonator applications where backscattering is currently limiting the performance of devices, such as ring-laser gyroscopes and dual frequency combs, which both suffer from injection locking. Moreover, these findings are of interest for integrated photonic circuits in which back reflections could negatively impact the stability of laser sources or other components.

scholarly journals Induction of Axonal Outgrowth in Mouse Hippocampal Neurons via Bacterial Magnetosomes

2021 ◽  
Vol 22 (8) ◽  
pp. 4126
Author(s):  
Sara De Vincentiis ◽  
Alessandro Falconieri ◽  
Frank Mickoleit ◽  
Valentina Cappello ◽  
Dirk Schüler ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Iron Oxide ◽  
Hippocampal Neurons ◽  
Magnetotactic Bacteria ◽  
Oxide Nanoparticles ◽  
Axonal Outgrowth ◽  
Mechanical Forces ◽  
Internalization Process ◽  
Oxide Crystals ◽  
Stimulation Of

Magnetosomes are membrane-enclosed iron oxide crystals biosynthesized by magnetotactic bacteria. As the biomineralization of bacterial magnetosomes can be genetically controlled, they have become promising nanomaterials for bionanotechnological applications. In the present paper, we explore a novel application of magnetosomes as nanotool for manipulating axonal outgrowth via stretch-growth (SG). SG refers to the process of stimulation of axonal outgrowth through the application of mechanical forces. Thanks to their superior magnetic properties, magnetosomes have been used to magnetize mouse hippocampal neurons in order to stretch axons under the application of magnetic fields. We found that magnetosomes are avidly internalized by cells. They adhere to the cell membrane, are quickly internalized, and slowly degrade after a few days from the internalization process. Our data show that bacterial magnetosomes are more efficient than synthetic iron oxide nanoparticles in stimulating axonal outgrowth via SG.

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