Hysteresis reversion in graphene field-effect transistors.

To enhance performances of graphene/SiO(2) based field-effect transistors (FETs), understanding of the transfer of carriers through the graphene/SiO(2) interface is crucial. In this paper, we have studied the temperature dependent transfer characters of graphene FETs. Hysteresis loop is shown to be dominated by trapping/detrapping carriers through the graphene/SiO(2) interface.

Effect of contact barrier on electron transport in graphene.

The influence of the barrier between metal electrodes and graphene on the electrical properties was studied on a two-electrode device. A classical barrier model was used to analyze the current-voltage characteristics. Primary parameters including barrier height and effective resistance were achieved. The electron transport properties under magnetic field were further investigated. An abnormal peak-valley-peak shape of voltage-magnetoresistance curve was observed. The underlying mechanisms were discussed under the consideration of the important influence of the contact barrier. Our results indicate electrical properties of graphene based devices are sensitive to the contact interface.

[Effect of a novel tyrosine kinase inhibitor HHGV678 on growth inhibition of Bcr-Abl wild type and IM-resistant cell lines in vitro].

This study was aimed to compare HHGV678 with imatinib (IM) in growth inhibition of Bcr-Abl wild type and IM-resistant cell lines, investigate the possibility of replacing IM with HHGV678 in treatment of chronic myeloid leukemia (CML) and IM-resistant CML patients. Viability of two Bcr-Abl wild type cell lines (K562 and 32Dp210) and 16 IM-resistant cell lines (K562R and 15 Bcr-Abl point mutant cell lines) treated with HHGV678 and IM was analyzed by MTT. The apoptosis of those cells was identified by flow cytometry with Annexin V staining and DNA ladder analysis. Western blot was applied for detecting the expression of Bcr-Abl and phosphotyrosine protein levels. The results indicated that HHGV678 significantly inhibited the growth of two Bcr-Abl wild types and IM-resistant cell lines in dose-dependent manner except cell line of T315I point mutant. IC(50) results showed that the growth inhibition of HHGV678 was 15.5 and 28-fold higher than that of IM in K562, 32Dp210 and 1.4 to 124.3-fold higher than that of IM in 15 IM-resistant cell lines respectively. Compared with IM, HHGV678 more significantly inhibited phosphotyrosine kinase protein of the cells mentioned above at different concentrations. With most importance, HHGV678 of 10.0 micromol/L induced cell apoptosis of 40.06% and 33.32% in K562R and 32Dp210(T315I) cell lines, which were much higher than that of IM (19.77% and 10.68%). It is concluded that HHGV678 is more effective than IM in the growth inhibition of Bcr-Abl wild type cell lines and IM-resistant cell lines, especially in strongest IM-resistant cell lines. Further studies are needed to show whether HHGV678 may be a novel targeting drug in treatment of CML and IM-resistant CML patients.

[Growth inhibition and differentiation of imatinib-resistant chronic myeloid leukemia cell induced by cell differentiation agent in vitro].

OBJECTIVE: To investigate the effects of uroacitide (CDA-2), a cell differentiation agent, on the growth inhibition and differentiation of imatinib-(IM) resistant chronic myeloid leukemia (CML) cells. METHODS: IM resistant CML cell line K562R was established from the line K562. K562 and K562R CML cells were cultured with CDA-2 of different concentrations. MTI method was used to detect the survival rates. Bone marrow cells of IM-resistant and non-IM-resistant CML patients were collected and co-incubated with K562 and K562R cells. MTT and colony-forming assays were used to evaluate the efficacy of CDA-2 treatment for cell growth in K562 and K562R cell lines, and IM-resistant or non-IM-resistant bone marrow cells of the CML patients; Annexin-V staining was employed to detect the apoptosis. Cell differentiation was assessed by flow cytometry analysis with CD11b/CD14 markers, reverse transcriptase PCR (RT-PCR) for mRNA levels of NCF-1 and ORM-1 genes and Giemsa staining for the observation in morphology. Cell cycle distribution was detected by stained with propidium iodide and then analyzed by flow cytometer. RT-PCR also was employed for the expression of DNA methyltransferase. RESULTS: Significant cell growth inhibition was found at a dose-dependent manner in the IM-resistant K562R cell line and IM-resistant bone marrow cells of the CML patients compared with the non-resistant K562 cell line and bone marrow cells of the CML patients following 7 days exposure to CDA-2. Although CDA-2 could significantly induce the apoptosis of K562R (15.38%) compared with K562 (5.28%) (P < 0.05), the major reason for the cell growth inhibition of K562R is CDA-2-induced cell differentiation, including the increase of expression of differentiation-related antigens CD11b/CD14, mRNA expression of NCF-1 and ORM-1, and cell cycle arrest in G1-phase at a dose-dependent manner. Because CDA-2 could significantly activate the p21 and p27 gene expression, downregulate the expression of cyclin D1, and down-regulate the expressions of DNMT1 and DNMT(3B) at mRNA level, CDA-2 might be a DNMT inhibitor for restoring some gene function that involved in cell cycle control by demethylation. CONCLUSION: Inhibiting the growth and inducing the differentiation of K562R cells, CDA-2 is very likely to be a potential agent for the treatment of IM resistance CML patients.