Low-Voltage and High-Performance Multilayer MoS₂ Field-Effect Transistors with Graphene Electrodes

Atomically thin two-dimensional (2D) materials are attractive because they have excellent material properties and channel length scalability. Fabrication of complex structures from these materials is also relatively easy. Accordingly, 2D materials such as molybdenum disulfide (MoS₂) have been intensively studied because of their novel properties for advanced electronics and optoelectronics. This study realizes the low-voltage and high-performance field-effect transistors with chemical vapor deposition-grown single layer graphene employed as the thinnest electrode and semiconducting multilayer (ML) MoS₂ utilized as a channel material. The two-terminal mobility of graphene-contacted ML MoS₂ using 15 nm Al₂O₃ as the top-gate dielectric layer is 131.2 cm²/(V s) at room temperature, which is higher than that of the previously reported metal/graphene-contacted MoS₂. The result demonstrates that van der Waals bonding at the graphene–MoS₂ interfaces and high-<i>k</i> dielectric provide an important step toward the realization of high-performance and low-voltage thin-film transistors

Directed Self-Assembly of Poly(3,3‴-dialkylquarterthiophene) Polymer Thin Film: Effect of Annealing Temperature

Self-assembly of π-conjugated polymers in desired manner plays a vital role in structure, orientations, crystalline packing, and also in electrical charge transport properties. Despite this, there is lack of thorough study about the direct formation of smooth, oriented, crystalline, and aligned films using self-assembly property of π-conjugated polymers. In this study, we have discussed the crystallization behavior and an easy method to study face-on orientation, crystallization, and alignment in organic films, giving as an example poly­(3,3‴-dialkylquarterthiophene) (PQT-12). The effect of annealing temperature (80 and 120 °C) is also studied for this polymer film as the ordering of the polymer backbone and side chains highly depends on temperature. We have directed the self-assembly of PQT-12 using facile “floating film transfer method (FTM)” for obtaining crystalline, oriented, smooth, and aligned polymer films directly without further processing. Unpolarized, polarized UV–vis spectra and selected area electron diffraction (SAED) pattern are used to investigate the ordering/crystallinity, orientation, and alignment (optical anisotropy) of PQT-12 polymer films. Further, an easy electrochemical method is explored to study the crystalline and amorphous phases in the polymer films. Atomic force microscopy (AFM) topography is carried out to study the surface morphology, which shows formation of very smooth films with roughness below 1 nm. Raman spectra show the increase in intensity of signal-to-noise ratio (SNR) (1457 cm^–1) and decrease in ratio of SNR intensity (1457 cm^–1/1393 cm^–1) as a function of annealing temperature. Finally, this study helps in improving the charge transport properties of films and is characterized into two modes, perpendicular and along the films surface with the effect of annealing temperature on PQT-12 films

Nucleo-Cytoplasmic Trafficking of TRIM8, a Novel Oncogene, Is Involved in Positive Regulation of TNF Induced NF-κB Pathway

<div><p>TNF induced nuclear factor kappa B (NF-κB) is one of the central signaling pathways that plays a critical role in carcinogenesis and inflammatory diseases. Post-translational modification through ubiquitin plays important role in the regulation of this pathway. In the current study, we investigated the role of TRIM8, member of RING family ubiquitin ligase in regulation of NF-κB pathway. We observed that TRIM8 positively regulates TNF induced NF-κB pathway. Different domains of TRIM8 showed discrete functions at the different steps in regulation of TNF induced NF-κB pathway. Ubiquitin ligase activity of TRIM8 is essential for regulation of NF-κB activation in both cytoplasm as well as nucleus. TRIM8 negates PIAS3 mediated negative repression of NF-κB at p65 by inducing translocation of PIAS3 from nucleus to cytoplasm as well as its turnover. TNF induces translocation of TRIM8 from nucleus to cytoplasm, which positively regulates NF-κB. The cytoplasmic translocation of TRIM8 is essential for TNF induced NF-κB but not for p65 mediated NF-κB regulation. TRIM8 also enhanced the clonogenic and migration ability of cells by modulating NF-κB. The further study will help to understand the role of TRIM8 in inflammation and cancer.</p> </div

Systematic Analysis of Small RNAs Associated with Human Mitochondria by Deep Sequencing: Detailed Analysis of Mitochondrial Associated miRNA

<div><p>Mitochondria are one of the central regulators of many cellular processes beyond its well established role in energy metabolism. The inter-organellar crosstalk is critical for the optimal function of mitochondria. Many nuclear encoded proteins and RNA are imported to mitochondria. The translocation of small RNA (sRNA) including miRNA to mitochondria and other sub-cellular organelle is still not clear. We characterized here sRNA including miRNA associated with human mitochondria by cellular fractionation and deep sequencing approach. Mitochondria were purified from HEK293 and HeLa cells for RNA isolation. The sRNA library was generated and sequenced using Illumina system. The analysis showed the presence of unique population of sRNA associated with mitochondria including miRNA. Putative novel miRNAs were characterized from unannotated sRNA sequences. The study showed the association of 428 known, 196 putative novel miRNAs to mitochondria of HEK293 and 327 known, 13 putative novel miRNAs to mitochondria of HeLa cells. The alignment of sRNA to mitochondrial genome was also studied. The targets were analyzed using DAVID to classify them in unique networks using GO and KEGG tools. Analysis of identified targets showed that miRNA associated with mitochondria regulates critical cellular processes like RNA turnover, apoptosis, cell cycle and nucleotide metabolism. The six miRNAs (counts >1000) associated with mitochondria of both HEK293 and HeLa were validated by RT-qPCR. To our knowledge, this is the first systematic study demonstrating the associations of sRNA including miRNA with mitochondria that may regulate site-specific turnover of target mRNA important for mitochondrial related functions.</p> </div

Analysis of isolated mitochondria.

<p>The mitochondria were isolated and purified from HEK293 and HeLa. (A) The protein contents of whole cell lysate, and purified mitochondria were normalized, resolved on 12.5% SDS-PAGE, transferred to PVDF membrane and probed with NDUFS2 and RPS9 antibody. (B) RNA was isolated from purified mitochondria and total cell. The subsequent cDNA was used for PCR amplification of mitochondrial encoded ND4 and cytosolic/nuclear specific β-actin. M: mitochondrial fraction; C: cellular lysate. (C) RNA was isolated from mitochondria. The nuclear RNA contamination in mitochondrial RNA was assessed by checking relative enrichment of mitochondrial encoded RNA (ND4, CYB) and nuclear encoded mRNA (TRIM4, MITA) by RT-qPCR as described in method section.</p

TRIM8 positively regulates TNFα induced NF-κB activation.

<p>(A) TRIM8 enhances TNFα induced NF-κB activation. HEK293 cells were transfected with TRIM8 and vector with NF-κB luciferase reporter constructs as described in materials and methods section. NF-κB activation was measured by Dual Glo luciferase assay. (B) TRIM8 induces p65 translocation to nucleus. Graphical representation of the numbers of cells with nuclear p65-GFP in TRIM8 and vector transfected cells as described in materials and method section. (C) TRIM8 positively regulates NF-κB at the level of p65. HEK293 cells were co-transfected with TRIM8, vector and specified gene. NF-κB activity was monitored by Dual Glo luciferase assay as described earlier. TRIM8 significantly enhances RIP1, cIAP1, TRAF2, IKKβ and p65 mediated NF-κB activation. (D) TRIM8 expression enhances p65 mediated NF-κB activation in HeLa cells. p65 overexpression was confirmed by western blotting. (E) TRIM8 knockdown suppresses p65 mediated NF-κB activation in HeLa cells. TRIM8 knockdown was validated by RT-PCR.</p

Nucleo-cytoplasmic translocation of TRIM8 is involved in regulation of NF-κB.

<p>(A) TRIM8 translocates to cytoplasm in the presence of TNFα. HEK293 cells were plated on cover slip and transfected with TRIM8-GFP. After 24 hours of transfection, the cells were treated with TNFα and fixed with 4% paraformaldehyde, stained with DAPI and visualized by confocal microscopy. Scale bar represent 7.5 µM. (B) Quantification of cells showing nuclear positive TRIM8-GFP in untreated and TNF treatment condition. (C) Time course analysis of nucleo-cytoplasmic localization of TRIM8 in response to TNF. Quantification of nuclear TRIM8-GFP positive cells in control and TNF treated conditions at indicated time points. (D) Leptomycin B suppresses TNF mediated cytoplasmic translocation of TRIM8. Quantification of cells showing nuclear TRIM8-GFP in indicated treatment conditions (Lepto = Leptomycin B). (E) Analysis of sub-cellular localization of TRIM8 in control and TNF treated cells. HEK293 cells were transfected with HA-TRIM8, nuclear and cytosolic fractions were isolated as described in materials and method. The fractions were analyzed by western blotting using indicated antibodies. (Lepto = Leptomycin B) (F) Leptomycin B suppresses TRIM8 mediated TNF induced NF-κB pathway. HEK293 was transfected with TRIM8, vector with or without p65, treated with Leptomycin B and NF-κB activation measured by Dual Glo luciferase assay. (Lepto = Leptomycin B) (G) Leptomycin B suppresses TAK1 induced NF-κB pathway. HEK293 was transfected with indicated constructs and NF-κB activation measured by Dual Glo luciferase assay (Lepto = Leptomycin B). Asterisk (*) indicates data changes are statistically significant between groups: p value<0.05 for SEM of minimum three independent experiments.</p

Cellular localization of different domains of TRIM8 and their role in NF-κB activation.

<p>(A) Schematic diagram showing TRIM8 domains and constructs used for transfection. (B) Cellular localization of TRIM8 deletion constructs. HeLa cells were plated on cover slip and transfected with GFP-tagged different deletion constructs of TRIM8. After 24 hours of transfection, the cells were fixed with 4% paraformaldehyde, stained with DAPI and visualized by confocal microscopy. Scale bar represent 7.5 µM. (C) RING domain is essential for positive regulation of TNF induced NF-κB activation. HEK293 was co-transfected with full length TRIM8, ΔRING, ΔB1, ΔCC, ΔC-ter, vector, treated with TNFα and NF-κB activation measured by Dual Glo luciferase assay. (D) RING, CC domain and C-terminal region of TRIM8 is essential for p65 mediated NF-κB activity. HEK293 was co-transfected with full length TRIM8, ΔRING, ΔB1, ΔCC, ΔC-ter, vector with p65-GFP and NF-κB activation measured by Dual Glo luciferase assay. Asterisk (*) indicates NF-κB activation significantly changed between groups: p value<0.05 for SEM of minimum three independent experiments.</p

Mapping sRNAs to human mitochondrial genome.

<p>The sequences obtained from the mitochondrial sRNA libraries from HEK293 and HeLa were aligned to mitochondrial genome. (A) An overview of mitochondria-associated sRNAs from HEK293 that aligned to mitochondrial genome. (B) An overview of mitochondria-associated sRNAs from HeLa that aligned to mitochondrial genome. (C) The miRNAs and putative novel miRNAs that aligned to mtDNA (determined by SOAP, MapMi, BLASTN and RNAhybrid) were mapped on mtDNA using Dynamo Software tool. The locations of known miRNAs and putative novel miRNAs that aligned to mtDNA are marked in red and blue respectively. If more than 1 miRNA aligned to same position, only 1 miRNA was marked.</p

Frequency of distribution of different classes of RNA associated with mitochondrial sRNA libraries.

<p>The unique sequences obtained from the sRNA libraries were subjected to a series of sequence similarity searches using specific databases (rRNAs, tRNAs, snRNAs, snoRNAs, miRNAs, other non-coding RNAs). The sequences that did not match with any known sequence were considered as unannotated sequences. (A) An overview of sRNA associated with mitochondria of HEK293. (B) An overview of sRNA associated with the mitochondria of HeLa. The unique clean tags of repeat associated sequences were further categorized to determine the diversity of repeat associated RNA. (C) Detailed clustering of repeat-associated RNAs from mitochondria of HEK293. (D) Detailed clustering of repeat-associated RNAs from mitochondria of HeLa.</p