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Optimizing Reporter Gene Expression for Molecular Magnetic Resonance Imaging
Published in Shoogo Ueno, Bioimaging, 2020
Qin Sun, Frank S. Prato, Donna E. Goldhawk
The contribution of individual MTB genes to the process of magnetosome formation has been examined in both prokaryotes and eukaryotes. With the exception of mamB, mamE, mamI, and mamL, single deletion of many magnetosome genes in MTB produces irregularities in the biomineral crystal structure or its arrangement within the cell but does not destroy the compartment. There may be redundant functions among magnetosome proteins or subtle changes in magnetosome function that are not readily detected using common microbiology measures, like Cmag56,57 or a simple lab magnet.58 If instead of responding to the geomagnetic field (25–65 µTesla59), the objective is an in vivo response to MRI at clinical field strengths on the order of 3 Tesla (3T), then cells bearing the same type of iron biomineral would respond differently to the change in external field strength. As discussed below (in Section 9.4), the interaction of iron biomineral with the magnetic field in turn has an effect on relaxation rates of the proton, which is observed with MRI. This influence of iron will vary depending on the oxidation state, size, and shape of the crystal. Hence, diverse MR signals could be genetically programmed by taking advantage of the remarkable number of magnetosome sizes and shapes evident in diverse species of MTB.
Energy Medicine: Focus on Nonthermal Electromagnetic Therapies
Published in Len Wisneski, The Scientific Basis of Integrative Health, 2017
Len Wisneski, Bernard O. Williams
Binhi and Rubin (2007) recently have criticized assumptions of the so-called thermal threshold or thermal noise paradox. They reject the assumptions that electromagnetic field effects must be power processes. They propose that signals controlling magnetic resonance conditions influence the probability that a process will proceed rather than acting with the power of an either/or trigger. By modifying the electromagnet environment, subtle signals may shift the tendencies for cellular activities, rather than turning such activities on or off. Binhi and Rubin also offer magnetosomes, biological structures that are sensitive to magnetic flux, as another candidate for a mechanism of biological sensitivity to very weak magnetic forces. Magnetite crystals are present in many organisms. Bacteria use magnetosomes for orientation in the magnetic environment, and some bird species navigate using the Earth's magnetic field, possibly relying on magnetosomes. Magnetite crystals are present in human brain tissue, estimated at concentrations of 108 crystals per gram (Kirschvink et al., 1992). Alternatively, Dobson provided an estimate of about 50 ng/g (Dobson, 2002).
Genetic Approaches for Modulating MRI Contrast
Published in Michel M. J. Modo, Jeff W. M. Bulte, Molecular and Cellular MR Imaging, 2007
Eric T. Ahrens, William F. Goins, Clinton S. Robison
Many organisms produce intracellular, biomineralized, superparamagnetic nanocrystals incorporating iron. The magnetosome structure of the magnetotactic bacteria is a dramatic example.24 Assembling magnetosomes within the bacteria creates a magnetic dipole moment in the cell and a biomagnetic compass. However, the precise genetic control of magnetosome formation is complex and involves many loci.25,26 There are many examples of paramagnetic metalloproteins, particularly ferritins, found in nature. Ferritins are part of a superfamily of iron storage proteins that are found in virtually all animals, plants, fungi, and bacteria.
Exploring the potential of the dynamic hysteresis loops via high field, high frequency and temperature adjustable AC magnetometer for magnetic hyperthermia characterization
Published in International Journal of Hyperthermia, 2020
Irati Rodrigo, Idoia Castellanos-Rubio, Eneko Garaio, Oihane K. Arriortua, Maite Insausti, Iñaki Orue, José Ángel García, Fernando Plazaola
Naturally, thermal or stochastic fluctuation of the object in the liquid works to remove the orientation effect, so, large net and permanent magnetic moments are essential to produce a full alignment of the magnetic object with the field. In such case, the reduced remanence magnetization becomes much higher than 0.5 for almost any AC field amplitude. The mechanical orientation along the field lines can be observed very clearly in sample D, and in a weaker way in samples B and C, composed of particles of smaller size. It is obvious that this mechanism is size-sensitive, and also happens with isolated or non-interacting particles. However, this effect has been reported as particularly intense in magnetotactic bacteria [27,57], where the chain arrangement of magnetosomes strongly favors the orientation of bacteria in water-based solutions. Similar behaviors have been observed in free Fe MNPs at 25 mT [58] and FeC MNPs at 44 mT (both at 93 kHz) [29]. It is worthy to note that particles of samples B, C and D have a trend toward chaining with the aim to reduce the magneto-static energy (as shown in Figure 5(d)). These chains can carry a large permanent magnetic moment. Particularly in sample D, this tendency is stronger and the large squareness of the AC loops (for any field amplitude) could suggest the formation of large chains with well-defined easy axis that become mostly aligned in the magnetic field lines during AC magnetometry experiments. However, the rotation of each individual particle toward the field lines can also contribute to this mechanism and must be considered as a possible explanation.
MagA increases MRI sensitivity and attenuates peroxidation-based damage to the bone-marrow haematopoietic microenvironment caused by iron overload
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Yingying Shen, Cunjing Zheng, Yunpu Tan, Xinhua Jiang, Li Li
The iron concentration is expected to influence MRI signals, so several iron-related genes have been studied as “MRI markers”, including magA. In Magnetospirillum magneticum species AMB-1, magA was initially believed to participate in magnetosome synthesis [14]. More recently, MagA has been recognized as a nonessential magnetosome protein [15] located outside the magnetosome genomic island [16,17]. Typically, a magnetosome consists of a lipid bilayer surrounding a magnetite crystal (Fe3O4 in AMB-1). The magA gene encodes an integral membrane protein with homology to the bacterial H+/Fe2+ antiporter family of proteins coupled to ATPase [18,19]. With MagA expressed in the Escherichia coli, cells have been shown to transport Fe2+ in an energy-dependent manner, leading to accumulation of Fe2+ in the vesicle [14,18].
Cellular biogenesis of metal nanoparticles by water velvet (Azolla pinnata): different fates of the uptake Fe3+ and Ni2+ to transform into nanoparticles
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2021
Ratima Janthima, Sineenat Siri
Metal nanoparticles (NPs) have received many research interests due to their outstanding chemical and physical properties at the nanoscale size, which were suitable for diverse applications such as catalysts, optics, biomedical, and environmental applications [1–8]. According to the high demand for these NPs, various approaches for their synthesis have been proposed, mainly via physical and chemical methods. In the physical methods, metal NPs are produced through the reduction of a bulk metal to nanosized metal particles by cutting, milling, or laser-irradiating [9,10]. In contrast, chemical methods are less expensive and simpler than physical methods, making them suitable for an industrial mass-production of metal NPs. Chemical synthesis is based on a reduction of metal ions to zero-valent metal and eventually assembled to NPs. This synthesis requires reducing and stabilizing agents, in which chemical reagents and polymers are generally used [11]. Alternatively, there were reports of biogenesis of metal NPs in living organisms. Some bacteria could produce intracellular metal NPs. For example, Bacillus sp. reduced Ag+ ions to Ag0 and formed the crystalline structure of silver NPs in the periplasmic space after exposure to the aqueous AgNO3 solution. Some bacteria could produce intracellular metal NPs. For example, Bacillus sp. reduced Ag+ ions to Ag0 and formed crystalline structure of silver NPs in the periplasmic space after exposing to the aqueous AgNO3 solution. Magnetotactic bacteria could produce membrane-bound iron NPs accumulated in specific intracellular organelles, the magnetosomes, from the uptake of iron ions [12]. In principle, these bacteria synthesize iron NPs via the binding of the uptake Fe3+ with iron-binding molecules, chelation them to Fe2+, and controlled nucleation and growth of FeNPs in magnetosomes by specific genes and proteins [13]. Nevertheless, the intracellular formation of MNPs in the higher eukaryotes, particularly macrophytes, remains inexplicit.