Energy distributions of field emitted electrons from carbon nanosheets: manifestation of the quantum size effect

We emphasize the importance of experiments with voltage dependent field emission energy distribution analysis in carbon nanosheets. Our analysis shows the crucial influence of the band structure on the energy distribution of field emitted electrons in few-layer graphene. In addition to the main peak we found characteristic sub-peaks in the energy distribution. Their positions strongly depend on the number of layers and the inter-layer interaction. The discovery of these peaks in field emission experiments from carbon nanosheets would be a clear manifestation of the quantum size effect in these new materials.Comment: accepted for publication in JETP Letter

Effect of Temperature Gradient Direction in the Catalyst Nanoparticle on CNTs Growth Mode

To improve the understanding on CNT growth modes, the various processes, including thermal CVD, MP-CVD and ECR-CVD, have been used to deposit CNTs on nanoporous SBA-15 and Si wafer substrates with C2H2 and H2 as reaction gases. The experiments to vary process parameter of ΔT, defined as the vector quantities of temperature at catalyst top minus it at catalyst bottom, were carried out to demonstrate its effect on the CNT growth mode. The TEM and TGA analyses were used to characterize their growth modes and carbon yields of the processes. The results show that ΔT can be used to monitor the temperature gradient direction across the catalyst nanoparticle during the growth stage of CNTs. The results also indicate that the tip-growth CNTs, base-growth CNTs and onion-like carbon are generally fabricated under conditions of ΔT > 0, <0 and ~0, respectively. Our proposed growth mechanisms can be successfully adopted to explain why the base- and tip-growth CNTs are common in thermal CVD and plasma-enhanced CVD processes, respectively. Furthermore, our experiments have also successfully demonstrated the possibility to vary ΔT to obtain the desired growth mode of CNTs by thermal or plasma-enhanced CVD systems for different applications

Recent progress and perspectives of space electric propulsion systems based on smart nanomaterials

Miniaturized spacecraft built from advanced nanomaterials are poised for unmanned space exploration. In this review, the authors examine the integration of nanotechnology in electric propulsion systems and propose the concept of self-healing and adaptive thrusters

Antitumor activity of Ru(III) complexes carrying beta-diketonato ligands in vitro and in vivo

Purpose: To investigate the antitumor activity of two newly synthesized ruthenium(III) [Ru(III)] compounds carrying bidentate ligands: (acac)-acetylacetonate, [Ru(acac)(3)], and (tfac)-trifluoroacetylacetonate [Ru(tfac)(3)]. Materials and methods: The activity of ruthenium(III) analogues was evaluated on HeLa, B16, and Femx cell lines for cytotoxicity in vitro using MTT assay, and inhibition on tumor invading ability in vitro using cell migration and invasion assays, whereas inhibition of tumor growth in vivo was estimated on advanced B16 murine melanoma model. Both compounds were also investigated in combinations with cisplatin, oxaliplatin, or poly ADP-ribose polymerase-1 (PARP-1) inhibitor, in order to determine the pattern of mutual interactions. Results: Applied as single drugs, Ru(tfac)(3) showed high cytotoxic activity against HeLa and Femx cell lines, while Ru(acac)(3) did not reach the IC(50) on any of the cell lines tested. In combinations, Ru(acac)(3) with cisplalin gained synergistic interaction, antagonistic with oxaliplatin, and of different kind with (PARP-1) inhibitor in concentration-and cell line-dependent manner. Ru(acac)(3) exhibited inhibition of HeLa cell migration and gelatinolytic activity of MMP-2 and MMP-9. Ru(tfac)(3) complexes didnot induce significant reduction of melanoma growth in vivo, whereas Ru(acac)(3) did, but the latter failed to contribute in lifespan improvement. Conclusion: The investigated ruthenium complexes showed different levels of antitumor activity in vitro and in vivo, implicating on different mechanisms of their action as well as diverse perspectives in cancer treatment

Antitumor activity of Ru(III) complexes carrying beta-diketonato ligands in vitro and in vivo

Purpose: To investigate the antitumor activity of two newly synthesized ruthenium(III) [Ru(III)] compounds carrying bidentate ligands: (acac)-acetylacetonate, [Ru(acac)(3)], and (tfac)-trifluoroacetylacetonate [Ru(tfac)(3)]. Materials and methods: The activity of ruthenium(III) analogues was evaluated on HeLa, B16, and Femx cell lines for cytotoxicity in vitro using MTT assay, and inhibition on tumor invading ability in vitro using cell migration and invasion assays, whereas inhibition of tumor growth in vivo was estimated on advanced B16 murine melanoma model. Both compounds were also investigated in combinations with cisplatin, oxaliplatin, or poly ADP-ribose polymerase-1 (PARP-1) inhibitor, in order to determine the pattern of mutual interactions. Results: Applied as single drugs, Ru(tfac)(3) showed high cytotoxic activity against HeLa and Femx cell lines, while Ru(acac)(3) did not reach the IC(50) on any of the cell lines tested. In combinations, Ru(acac)(3) with cisplalin gained synergistic interaction, antagonistic with oxaliplatin, and of different kind with (PARP-1) inhibitor in concentration-and cell line-dependent manner. Ru(acac)(3) exhibited inhibition of HeLa cell migration and gelatinolytic activity of MMP-2 and MMP-9. Ru(tfac)(3) complexes didnot induce significant reduction of melanoma growth in vivo, whereas Ru(acac)(3) did, but the latter failed to contribute in lifespan improvement. Conclusion: The investigated ruthenium complexes showed different levels of antitumor activity in vitro and in vivo, implicating on different mechanisms of their action as well as diverse perspectives in cancer treatment

Integrin alpha(5)beta(1): a new purification strategy based on immobilized peptides

Wobbe L, Zimmermann D, Wissbock M, et al. Integrin alpha(5)beta(1): a new purification strategy based on immobilized peptides. Journal of Peptide Research. 2005;66(Suppl. 1):22-29.Novel efficient and robust affinity chromatography material: There are several strategies known for the purification of integrins by affinity chromatography, but the disadvantages of common strategies like insufficient selectivity or compelling conditions for the elution still require alternatives. A new strategy, based on the immobilized C-terminally modified peptide Ac-Gly-Ala-c-(Cys(SS)-Arg-Arg-Glu-Thr-Ala-Trp-Ala-Cys(SS))-Gly-Ala-O(CH2 CH2O)(2)CH2CH2-NH2 allows for the affinity purification of the integrin alpha(5)beta(1). While RGD peptides have been proven in the past to be inappropriate for selective purification of integrins by affinity chromatography, the new peptide can be efficiently used for selective enrichment of the integrin alpha(5)beta(1). It is a specific ligand of the target protein, but does not contain an RGD sequence. The application of well-characterized affinity chromatography material with a site-specifically immobilized peptide allows to obtain integrin alpha(5)beta(1) in a single chromatography step without contamination by other integrins. This process combines the advantages of a selective and monospecific protein-ligand recognition with mild elution conditions and a low sensitivity of the immobilized ligand with respect to column regeneration

Integrin alpha(5)beta(1) ligands: Biological evaluation and conformational analysis

Zimmermann D, Guthohrlein EW, Malesevic M, et al. Integrin alpha(5)beta(1) ligands: Biological evaluation and conformational analysis. ChemBioChem. 2005;6(2):272-276

Synthesis and characterization of a novel Pd(II) complex with the condensation product of 2-(diphenylphosphino) benzaldehyde and ethyl hydrazino acetate. Cytotoxic activity of the synthesized complex and related Pd(II) and Pt(II) complexes

A new palladium(II) complex I of the condensation product of 2-(diphenylphosphino)benzaldehyde (dpba) and ethyl hydrazinoace-tate (etha) was synthesized and characterized by elemental analyses, IR, and H-1 NMR spectroscopy. The bound ligand is a bidentate (PN chromophore), the remaining two coordination places being occupied by chloride ions in overall square planar geometry. The cytotoxic activity of the complex I and two related Pd(II) and Pt(II) complexes 2 and 3 was tested against a panel of four tumor cell lines. The activity of the complexes was similar to that of cisplatin, the most widely used metal-based antitumor drug. It is important to notice that complexes 2 and 3 were active to cisplatin-resistant U2-OS/Pt cells. Cell cycle alteration investigation, apoptotic assay and gelatin zymography in relation to invasion and metastasis of tumor cells, were performed with all the investigated complexes on Human cervix carcinoma (HeLa) cells. The results suggest that I has a similar effect to cisplatin, inducing apoptosis followed by arrest of cells in S phase of cell cycle, while 2 and 3 induce apoptosis without significant perturbations of cell cycle distribution. (c) 2006 Elsevier Inc. All rights reserved