305 research outputs found
A novel approach to collision-induced dissociation (CID) for ion mobility-mass spectrometry experiments
Large microwave generation from d.c. driven magnetic vortex oscillators in magnetic tunnel junctions
Spin polarized current can excite the magnetization of a ferromagnet through
the transfer of spin angular momentum to the local spin system. This pure
spin-related transport phenomena leads to alluring possibilities for the
achievement of a nanometer scale, CMOS compatible and tunable microwave
generator operating at low bias for future wireless communications. Microwave
emission generated by the persitent motion of magnetic vortices induced by spin
transfer effect seems to be a unique manner to reach appropriate spectral
linewidth. However, in metallic systems, where such vortex oscillations have
been observed, the resulting microwave power is much too small. Here we present
experimental evidences of spin-transfer induced core vortex precessions in
MgO-based magnetic tunnel junctions with similar good spectral quality but an
emitted power at least one order of magnitude stronger. More importantly,
unlike to others spin transfer excitations, the thorough comparison between
experimental results and models provide a clear textbook illustration of the
mechanisms of vortex precessions induced by spin transfer
The influence and utility of varying field strength for the separation of tryptic peptides by ion mobility-mass spectrometry
Integrating Ion Mobility Mass Spectrometry with Molecular Modelling to Determine the Architecture of Multiprotein Complexes
Current challenges in the field of structural genomics point to the need for new tools and technologies for obtaining structures of macromolecular protein complexes. Here, we present an integrative computational method that uses molecular modelling, ion mobility-mass spectrometry (IM-MS) and incomplete atomic structures, usually from X-ray crystallography, to generate models of the subunit architecture of protein complexes. We begin by analyzing protein complexes using IM-MS, and by taking measurements of both intact complexes and sub-complexes that are generated in solution. We then examine available high resolution structural data and use a suite of computational methods to account for missing residues at the subunit and/or domain level. High-order complexes and sub-complexes are then constructed that conform to distance and connectivity constraints imposed by IM-MS data. We illustrate our method by applying it to multimeric protein complexes within the Escherichia coli replisome: the sliding clamp, (β2), the γ complex (γ3δδ′), the DnaB helicase (DnaB6) and the Single-Stranded Binding Protein (SSB4)
A mechanistic study of the H/D exchange reactions of protonated arginine and arginine-containing Di- and tripeptides
Evidence for structural variants of a- and b-type peptide fragment ions using combined ion mobility/mass spectrometry
Creation and annihilation of topological meron pairs in in-plane magnetized films
Merons which are topologically equivalent to one-half of skyrmions can exist only in pairs or groups in two-dimensional (2D) ferromagnetic (FM) systems. The recent discovery of meron lattice in chiral magnet Co8Zn9Mn3 raises the immediate challenging question that whether a single meron pair, which is the most fundamental topological structure in any 2D meron systems, can be created and stabilized in a continuous FM film? Utilizing winding number conservation, we develop a new method to create and stabilize a single pair of merons in a continuous Py film by local vortex imprinting from a Co disk. By observing the created meron pair directly within a magnetic field, we determine its topological structure unambiguously and explore the topological effect in its creation and annihilation processes. Our work opens a pathway towards developing and controlling topological structures in general magnetic systems without the restriction of perpendicular anisotropy and Dzyaloshinskii-Moriya interaction
The structure of gas-phase bradykinin fragment 1–5 (RPPGF) ions: An ion mobility spectrometry and H/D exchange ion-molecule reaction chemistry study
Observation of the magnetic domain structures in CuNi thin films at low temperatures
We report on the first experimental visualization of domain structure in
films of weakly ferromagnetic CuNi alloy with different
thickness at liquid helium temperatures. Improved high-resolution Bitter
decoration technique was used to map the magnetic contrast on the top of the
films well below the Curie temperature T ( 60 K). In contrast
to magnetic force microscopy, this technique allowed visualization of the
domain structure without its disturbance while the larger areas of the sample
were probed. Maze-like domain patterns, typical for perpendicular magnetic
anisotropy, were observed. The average domain width was found to be about 100
nm.Comment: 4 pages, 5 figures, will be published in JETP Let
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