Quantitative Measurement of the Magnetic Moment of Individual Magnetic Nanoparticles by Magnetic Force Microscopy

The quantitative measurement of the magnetization of individual magnetic nanoparticles (MNPs) using magnetic force microscopy (MFM) is described. Quantitative measurement is realized by calibration of the MFM signal using an MNP reference sample with traceably determined magnetization. A resolution of the magnetic moment of the order of 10-18 A m2 under ambient conditions is demonstrated, which is presently limited by the tip's magnetic moment and the noise level of the instrument. The calibration scheme can be applied to practically any magnetic force microscope and tip, thus allowing a wide range of future applications, for example in nanomagnetism and biotechnology

Structure-function studies of cytosolic phospholipase A2 and protein kinase C.

Structure-function studies of cytosolic phospholipase A2 and protein kinase C

Rab9 GTPase Regulates Late Endosome Size and Requires Effector Interaction for Its Stability

Rab9 GTPase resides in a late endosome microdomain together with mannose 6-phosphate receptors (MPRs) and the tail-interacting protein of 47 kDa (TIP47). To explore the importance of Rab9 for microdomain establishment, we depleted the protein from cultured cells. Rab9 depletion decreased late endosome size and reduced the numbers of multilamellar and dense-tubule–containing late endosomes/lysosomes, but not multivesicular endosomes. The remaining late endosomes and lysosomes were more tightly clustered near the nucleus, implicating Rab9 in endosome localization. Cells displayed increased surface MPRs and lysosome-associated membrane protein 1. In addition, cells showed increased MPR synthesis in conjunction with MPR missorting to the lysosome. Surprisingly, Rab9 stability on late endosomes required interaction with TIP47. Rabs are thought of as independent, prenylated entities that reside either on membranes or in cytosol, bound to GDP dissociation inhibitor. These data show that Rab9 stability is strongly influenced by a specific effector interaction. Moreover, Rab9 and the proteins with which it interacts seem critical for the maintenance of specific late endocytic compartments and endosome/lysosome localization

Stabilization of the high coercivity epsilon-Fe 23 O phase in the CeO2 - Fe2O3-SiO 2 nanocomposites

We have investigated the processes leading to the formation of the Fe2O3 and CeO2 nanoparticles in the SiO2 matrix in order to stabilize the ϵ-Fe2O3 as the major phase. The samples with two different concentrations of the Fe were prepared by sol-gel method, subsequently annealed at different temperatures up to 1100 °C, and characterized by the Mössbauer spectroscopy, Transmission Electron Microscopy (TEM), Powder X-ray Diffraction (PXRD), Energy dispersive X-ray analysis (EDX) and magnetic measurements. The evolution of the different Fe2O3 phases under various conditions of preparation was investigated, starting with the preferential appearance of the γ-Fe2O3 phase for the sample with low Fe concentration and low annealing temperature and stabilization of the major ϵ-Fe2O3 phase for high Fe concentration and high annealing temperature, coexisting with the most stable α-Fe2O3 phase. A continuous increase of the particle size of the CeO2 nanocrystals with increasing annealing temperature was also observed. The graphical abstract displays the most important results of our work. The significant change of the phase composition due to the variation of preparation conditions is demonstrated. As a result, significant change of the magnetic properties from superparamagnetic γ-Fe2O3 phase with negligible coercivity to the high coercivity ϵ-Fe2O3 phase has been observed. ⺠Research of the stabilization of the high coercivity ϵ-Fe2O3 in CeO2-Fe2O3/SiO2. ⺠Samples with two different concentrations of Fe and three annealing temperatures. ⺠Phase transition γ→ϵ→(β)→α with increasing annealing temperature and particle size. ⺠Elimination of the superparamagnetic phases in samples with higher content of Fe. ⺠Best conditions for high coercivity ϵ-Fe2O3 - higher Fe content and