Carbon States in Carbon-Encapsulated Nickel Nanoparticles Studied by Means of X-Ray Absorption, Emission, and Photoelectron Spectroscopies

Electronic structure of nickel nanoparticles encapsulated in carbon was characterized by photoelectron, X-ray absorption, and X-ray emission spectroscopies. Experimental spectra are compared with the density of states calculated in the frame of the density functional theory. The carbon shell of Ni nanoparticles has been found to be multilayer graphene with significant (about 6%) amount of Stone--Wales defects. Results of the experiments evidence protection of the metallic nanoparticles from the environmental degradation by providing a barrier against oxidation at least for two years. Exposure in air for 2 years leads to oxidation only of the carbon shell of Ni@C nanoparticles with coverage of functional groups.Comment: 16 pages, 6 figures, accepted in J. Phys. Chem.

Mto2 multisite phosphorylation inactivates non-spindle microtubule nucleation complexes during mitosis

Microtubule nucleation is highly regulated during the eukaryotic cell cycle, but the underlying molecular mechanisms are largely unknown. During mitosis in fission yeast Schizosaccharomyces pombe, cytoplasmic microtubule nucleation ceases simultaneously with intranuclear mitotic spindle assembly. Cytoplasmic nucleation depends on the Mto1/2 complex, which binds and activates the γ-tubulin complex and also recruits the γ-tubulin complex to both centrosomal (spindle pole body) and non-centrosomal sites. Here we show that the Mto1/2 complex disassembles during mitosis, coincident with hyperphosphorylation of Mto2 protein. By mapping and mutating multiple Mto2 phosphorylation sites, we generate mto2-phosphomutant strains with enhanced Mto1/2 complex stability, interaction with the γ-tubulin complex and microtubule nucleation activity. A mutant with 24 phosphorylation sites mutated to alanine, mto2[24A], retains interphase-like behaviour even in mitotic cells. This provides a molecular-level understanding of how phosphorylation ‘switches off' microtubule nucleation complexes during the cell cycle and, more broadly, illuminates mechanisms regulating non-centrosomal microtubule nucleation

Back on track – On the role of the microtubule for kinesin motility and cellular function

The evolution of cytoskeletal filaments (actin- and intermediate-filaments, and the microtubules) and their associated motor- and non-motor-proteins has enabled the eukaryotic cell to achieve complex organizational and structural tasks. This ability to control cellular transport processes and structures allowed for the development of such complex cellular organelles like cilia or flagella in single-cell organisms and made possible the development and differentiation of multi-cellular organisms with highly specialized, polarized cells. Also, the faithful segregation of large amounts of genetic information during cell division relies crucially on the reorganization and control of the cytoskeleton, making the cytoskeleton a key prerequisite for the development of highly complex genomes. Therefore, it is not surprising that the eukaryotic cell continuously invests considerable resources in the establishment, maintenance, modification and rearrangement of the cytoskeletal filaments and the regulation of its interaction with accessory proteins. Here we review the literature on the interaction between microtubules and motor-proteins of the kinesin-family. Our particular interest is the role of the microtubule in the regulation of kinesin motility and cellular function. After an introduction of the kinesin–microtubule interaction we focus on two interrelated aspects: (1) the active allosteric participation of the microtubule during the interaction with kinesins in general and (2) the possible regulatory role of post-translational modifications of the microtubule in the kinesin–microtubule interaction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42588/1/10974_2005_Article_9052.pd

Mass spectrometry of complex compound of bis-thiourea-lead (II) chloride

Complex compounds of lead salts and thiourea are of interest due to the possibility of their practical application as precursors in the deposition of metal sulphide films. It is relevant to establish the relationship between the composition and structure of the initial complex compounds and the structure of the sulphides formed as a result of their thermal destruction. This paper presents the results of studying the complex compounds formed in an aqueous solution of lead chloride and thiourea. The structure of the complex compounds was determined by matrix-assisted laser desorption/ionisation mass spectrometry. The mass spectrometry data confirmed the formation of the [Pb((NH2)2CS)2Cl2] complex in the solution, which is a precursor in the deposition of PbS films. It was demonstrated that mass spectrometry fragmentation of the molecular ion of the [Pb((NH2)2CS)2Cl2] compound leads to the formation of a lead sulphide ion. The obtained data confirm the formation of the lead-sulphur bonds in the inner sphere of the complex compound, which are fragments of the crystal structure of the prospective sulphide formed during the thermolysis of the comple

CLINICAL AND ROENTGENOLOGICAL CRITERIA OF SPINE-PELVIS RATIOS IN CHILDREN WITH DYSPLASTIC FEMUR SUBLUXATION

Aim of the study — to identify clinical and roentgenological criteria of the sagittal profile status of spine-pelvis segment in children with dysplastic femur subluxation.Material and Methods. The present study included 40 female patients (50 hip joints) aged from 12 to 17 years (14.7±1.58) with unilateral and bilateral hip joint instability due to dysplasia. Children were divided into two groups – the first group included 30 patients (30 hip joints) with unilateral femur subluxation, the second group – 10 patients (20 hip joints) with bilateral femur subluxation. All patients underwent a standard orthopaedic clinical examination using a specialized scale to objectify complaints. All patients underwent X-ray examination of hip joints in AP and Lauenstein projections, CT scanning as well as lateral panoramic roentgenography of C1-S1 including femoral bones in standing position of the patient.Results. The authors observed a strong positive correlation between sacrum inclination and lumbar lordosis curvature, antetorsion angle of proximal femur and sacrum inclination angle, severity of pain syndrome during impingement test and sacrum tilt: Pearson correlation coefficient was 0.71, 0.81 and 0.88 respectively. The authors reported in all patients a thoracic normokyphosis and lumbar hyperlordosis with excessive pelvis anteversion. Global sagittal disbalance was observed in all patients.Conclusion. Apart from typical anatomical and roentgenological changes in pelvic and femoral componentsof the joint the children with dysplastic femur subluxation are characterized by excessive pelvic anteversion. Criteria of above parameters are identical and do not depend on the number of joints involved into the pathological process. Cranial dislocation of femoral head results to abnormalities of sagittal spine-pelvis ratios. Pathological process in hip joints and abnormality of spine-pelvis ratios results in negative changes of sagittal spine profile in the form of hyperlordosis, of physiological criteria of thoracic kyphosis and of the global sagittal disbalance. All of the above leads to overload of spinal motion segments and development of spine degenerative and dystrophic changes at early age

Electronic structure of Sr<SUB>2</SUB>RuO<SUB>4</SUB>: X-ray fluorescence emission study

The results of measurements of O 1s total X-ray-fluorescence yield and Ru N2,3 and O K&#945; X-ray fluorescence emission spectra of Sr2RuO4 and Sr2RuO4.25 are presented. An excitation energy dependence of the O K&#945; X-ray emission spectra (XES) was observed in both compounds. The energy dependence of the spectra is attributed to the excitation of inequivalent O (1) in-plane and O(2) apical oxygens. The O(1) 2p and O(2) 2p density of states distribution in the valence band of Sr2RuO4 was found to be different in accordance with the results of band-structure calculations. O(1) 2p states are found to be mixed with Ru 4d(t2g) states providing the formation of p bonds. While the O Ka XES spectra are in fair agreement with band structure calculations, the theoretical two-peak distribution of Ru N2,3 XES is found to be different with respect to the intensity ratios and widths of the peaks of Ru N2,3 XES. These differences are attributed to a decrease of intensity of radiative 4d-4p transitions in the vicinity of the Fermi level (where the localization of Ru 4d states is higher than at the bottom of the valence band) due to a strong Koster-Kronig transition