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- Chen, Nansheng, et al.
(författare)
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Identification of ciliary and ciliopathy genes in Caenorhabditis elegans through comparative genomics
- 2006
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Ingår i: Genome Biology. - : Springer Science and Business Media LLC. - 1465-6906 .- 1474-760X. ; 7:12, s. R126-
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Tidskriftsartikel (refereegranskat)abstract
- Background: The recent availability of genome sequences of multiple related Caenorhabditis species has made it possible to identify, using comparative genomics, similarly transcribed genes in Caenorhabditis elegans and its sister species. Taking this approach, we have identified numerous novel ciliary genes in C. elegans, some of which may be orthologs of unidentified human ciliopathy genes. Results: By screening for genes possessing canonical X-box sequences in promoters of three Caenorhabditis species, namely C. elegans, C. briggsae and C. remanei, we identified 93 genes ( including known X-box regulated genes) that encode putative components of ciliated neurons in C. elegans and are subject to the same regulatory control. For many of these genes, restricted anatomical expression in ciliated cells was confirmed, and control of transcription by the ciliogenic DAF-19 RFX transcription factor was demonstrated by comparative transcriptional profiling of different tissue types and of daf-19(+) and daf-19(-) animals. Finally, we demonstrate that the dye-filling defect of dyf-5( mn400) animals, which is indicative of compromised exposure of cilia to the environment, is caused by a nonsense mutation in the serine/threonine protein kinase gene M04C9.5. Conclusion: Our comparative genomics-based predictions may be useful for identifying genes involved in human ciliopathies, including Bardet-Biedl Syndrome ( BBS), since the C. elegans orthologs of known human BBS genes contain X-box motifs and are required for normal dye filling in C. elegans ciliated neurons.
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- Linke, H, et al.
(författare)
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Quantum ratchets and quantum heat pumps
- 2002
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Ingår i: Applied Physics A: Materials Science & Processing. - : Springer Science and Business Media LLC. - 1432-0630. ; 75:2, s. 237-246
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Tidskriftsartikel (refereegranskat)abstract
- Quantum ratchets are Brownian motors in which the quantum dynamics of particles induces qualitatively new behavior. We review a series of experiments in which asymmetric semiconductor devices of sub-micron dimensions are used to study quantum ratchets for electrons. In rocked quantum-dot ratchets electron-wave interference is used to create a non-linear voltage response, leading to a ratchet effect. The direction of the net ratchet current in this type of device can be sensitively controlled by changing one of the following experimental variables: a small external magnetic field, the amplitude of the rocking force, or the Fermi energy. We also describe a tunneling ratchet in which the current direction depends on temperature. In our discussion of the tunneling ratchet we distinguish between three contributions to the non-linear current-voltage characteristics that lead to the ratchet effect: thermal excitation over energy barriers, tunneling through barriers, and wave reflection from barriers. Finally, we discuss the operation of adiabatically rocked tunneling ratchets as heat pumps.
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- Löfgren, Anneli, et al.
(författare)
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Symmetry of magnetoconductance fluctuations of quantum dots in the nonlinear response regime
- 2006
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 73:23
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the symmetry of magnetoconductance fluctuations of phase-coherent, two-terminal quantum dots in the nonlinear regime of transport. Specifically, we consider open, ballistic quantum dots (electron billiards) with and without symmetry axes parallel and perpendicular to the current direction and formulate a set of novel symmetry relations not observed in devices with lower symmetry. We experimentally confirm these relations, demonstrating that high-quality materials and modern semiconductor technology allow the fabrication of devices with almost perfect symmetry. Small deviations from the intended symmetry, presumably due to impurities and fabrication limitations, do exist and can be detected. We also take into account circuit-induced asymmetries of the measured conductance due to bias-dependent depletion and demonstrate that this effect can be experimentally distinguished from rectification effects that are due to a lack of device symmetry. Some open questions regarding the role of a magnetic field in the nonlinear regime of transport are highlighted.
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