Electron transfer characteristics of amino acid adsorption on epitaxial graphene FETs on SiC substrates

Clarifying the adsorption characteristics of biomolecules on graphene surfaces is critical for the development of field-effect transistor (FET)-based biosensors for detecting pH, DNA, proteins, and other biomarkers. Although there are many reports on biomolecule detection using graphene FETs, the detection mechanism has not yet been clarified. In this study, the adsorption behavior and electron transfer characteristics of 20 proteinogenic amino acids on graphene field-effect transistors are investigated. Large single-crystal graphene films were epitaxially grown on SiC substrates by a resist-free metal stencil mask lithography process then patterned by air plasma etching to form FET devices. Amino acids with different charge conditions (positive or negative charge) were introduced onto the epitaxial graphene surface in solution. The charge neutral points of the drain current vs gate voltage curves shifted in the negative gate voltage direction after the introduction of all amino acids, regardless of the type of amino acid and its charge condition. These amino acid adsorption characteristics agree well with previously reported protein adsorption characteristics on epitaxial graphene surfaces, indicating that the adsorption of proteins in the liquid phase occurs by electron doping to the graphene surface. These results indicate that non-specific protein binding always leads to electron doping of epitaxial graphene FETs

New chemically induced skin tumour susceptibility loci identified in a mouse backcross between FVB and dominant resistant PWK

<p>Abstract</p> <p>Background</p> <p>A variety of skin cancer susceptibility among mouse strains has allowed identification of genes responsible for skin cancer development. Fifteen <it>Skts </it>loci for skin tumour susceptibility have been mapped so far by using the two-stage skin carcinogenesis model [induced by 7.12-dimethylbenz(a)anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA)]. A few responsible genes have been identified using wild-derived dominant resistant <it>Mus spretus </it>mice, and one has been confirmed as a low penetrance cancer susceptibility gene in a variety of human cancers.</p> <p>Results</p> <p>In the present study, we found that wild-derived PWK mice developed no tumour by treatment with the two-stage skin carcinogenesis protocol. This phenotype is dominant resistant when crossed with the highly susceptible strain FVB. By analyzing the F1 backcross generation between PWK and FVB, we found empirical evidence of significant linkage at the new loci <it>Skts-fp1 </it>on chromosome 4 and suggestive linkage on chromosomes 1, 3, 11, 12 and 14 for skin tumour susceptibility. <it>Skts-fp1 </it>includes the <it>Skts7 </it>interval, which was previously mapped by a <it>Mus spretus </it>and NIH backcross. We also observed suggestive linkage on chromosomes 1 and 2 in the female population only, while suggestive linkage on chromosomes 14 and 15 only was observed in the male population. A significant genetic interaction was seen between markers of <it>D11Mit339</it> and <it>D16Mit14</it>.</p> <p>Conclusion</p> <p>Analysis of this new cross may facilitate the identification of genes responsible for mouse skin cancer susceptibility and may reveal their biological interactions.</p

Thermal desorption of structured water layer on epitaxial graphene

Thermal desorption of the structured water layer on graphene was observed in this study via electrical conductivity measurements. Specifically, a structured water layer was formed on the graphene surface via deionized water treatment, following which we examined the thermal desorption process of the layer using sheet resistance measurements. The water molecules acting as a p-type dopant were strongly adsorbed on graphene, forming a solid layer. Consequently, the layer was completely removed from the graphene surface at 300⁡°C. The thermal desorption spectrum of the structured water layer on graphene was quantitatively obtained by converting the measured sheet resistance to carrier density change

Association of predicted pathogenic mutations in mitochondrial ND genes with distant metastasis in NSCLC and colon cancer

Cancer cells have more mutations in their mitochondrial DNA (mtDNA) than do normal cells, and pathogenic mutations in the genes encoding mitochondrial NADH dehydrogenase (ND) subunits have been found to enhance the invasive and metastatic ability of various tumour cells in animal experiments. However, it is unknown whether single-nucleotide variants (SNVs) of the ND genes that decrease complex I activity are involved in distant metastasis in human clinical samples. Here, we demonstrated the enhancement of the distant metastasis of Lewis lung carcinoma cells by the ND6 13885insC mutation, which is accompanied by the overexpression of metastasis-related genes, metabolic reprogramming, the enhancement of tumour angiogenesis and the acquisition of resistance to stress-induced cell death. We then sequenced ND genes in primary tumour lesions with or without distant metastases as well as metastatic tumour lesions from 115 patients with non-small cell lung cancer (NSCLC) and colon cancer, and we subsequently selected 14 SNVs with the potential to decrease complex I activity. Intriguingly, a significant correlation was observed (P < 0.05 by Chi-square test) between the incidence of the selected mutations and distant metastasis. Thus, these results strongly suggest that pathogenic ND gene mutations participate in enhancing distant metastasis in human cancers

Graphene-Based Nano-Electro-Mechanical Switch with High On/Off Ratio

Locally defined nanomembrane structures can be produced in graphene films on a SiC substrate with atomic steps. The contact conductance between graphene and a metal-coated nanoprobe in scanning probe microscopy can be drastically reduced by inducing local buckling of the membranes. Repeatable current switching with high reproducibility can be realized. The on/off ratio can be varied from about 105 to below 10 by changing the contact force. At a low contact force, the contact conductance changes from 10μS (‘‘ON’’ state) to 100pS (‘‘OFF’’ state). This novel device structure could represent a new path to electrical switching at the nanoscale

A synthetic small molecule for rapid induction of multiple pluripotency genes in mouse embryonic fibroblasts.

Cellular reprogramming involves profound alterations in genome-wide gene expression that is precisely controlled by a hypothetical epigenetic code. Small molecules have been shown to artificially induce epigenetic modifications in a sequence independent manner. Recently, we showed that specific DNA binding hairpin pyrrole-imidazole polyamides (PIPs) could be conjugated with chromatin modifying histone deacetylase inhibitors like SAHA to epigenetically activate certain pluripotent genes in mouse fibroblasts. In our steadfast progress to improve the efficiency of SAHA-PIPs, we identified a novel compound termed, δ that could dramatically induce the endogenous expression of Oct-3/4 and Nanog. Genome-wide gene analysis suggests that in just 24 h and at nM concentration, δ induced multiple pluripotency-associated genes including Rex1 and Cdh1 by more than ten-fold. δ treated MEFs also rapidly overcame the rate-limiting step of epithelial transition in cellular reprogramming by switching "[Formula: see text]" the complex transcriptional gene network

Effects of UV light intensity on electrochemical wet etching of SiC for the fabrication of suspended graphene

We report on the effects of UV light intensity on the photo assisted electrochemical wet etching of SiC(0001) underneath an epitaxially grown graphene for the fabrication of suspended structures. The maximum etching rate of SiC(0001) was 2.5µm/h under UV light irradiation in 1wt% KOH at a constant current of 0.5mA/cm2. The successful formation of suspended structures depended on the etching rate of SiC. In the Raman spectra of the suspended structures, we did not observe a significant increase in the intensity of the D peak, which originates from defects in graphene sheets. This is most likely explained by the high quality of the single-crystalline graphene epitaxially grown on SiC

Microscopic Raman study of graphene on 4H-SiC two-dimensionally enhanced by surface roughness and gold nanoparticles

We present microscopic Raman spectroscopy measurements on single-layer graphene epitaxially grown on 4H-SiC by a thermal decomposition method. We collected spectral data with spatial resolution, which allowed us to obtain two-dimensionally enhanced Raman mapping images. Shallow holes in SiC, which had areas of 5 to 20 µm and depths of 100 nm, enhanced the Raman intensity of the 2D band of graphene. A monolayer of gold nanoparticle (AuNP) aggregates was successfully prepared by dropping and drying a colloidal suspension of AuNPs. The AuNP exhibited 30-fold enhanced the Raman spectra in the wavenumber range of 1550–1700 cm−1. Locally enhanced Raman intensity was also demonstrated using a glass microbead

Specific mitochondrial DNA mutation in mice regulates diabetes and lymphoma development

It has been hypothesized that respiration defects caused by accumulation of pathogenic mitochondrial DNA (mtDNA) mutations and the resultant overproduction of reactive oxygen species (ROS) or lactates are responsible for aging and age-associated disorders, including diabetes and tumor development. However, there is no direct evidence to prove the involvement of mtDNA mutations in these processes, because it is difficult to exclude the possible involvement of nuclear DNA mutations. Our previous studies resolved this issue by using an mtDNA exchange technology and showed that a G13997A mtDNA mutation found in mouse tumor cells induces metastasis via ROS overproduction. Here, using transmitochondrial mice (mito-mice), which we had generated previously by introducing G13997A mtDNA from mouse tumor cells into mouse embryonic stem cells, we provide convincing evidence supporting part of the abovementioned hypothesis by showing that G13997A mtDNA regulates diabetes development, lymphoma formation, and metastasis—but not aging—in this model