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Your search keyword '"Javad N. Farahani"' showing total 3 results
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3 results on '"Javad N. Farahani"'

1. Prospects of Resonant Optical Antennas for Nano-Analysis

Author

Bert Hecht, Peter Mühlschlegel, Javad N. Farahani, Hans-Jürgen Eisler, Dieter W. Pohl, Olivier J.F. Martin, and Paolo Biagioni

Subjects
Atomic force microscope (afm), Metal nano structures, Resonant optical antennas, Chemistry, QD1-999
Abstract

Suitably shaped metal nano structures act as resonant optical antennas that efficiently collect light and confine it to a subwavelength volume. Vice versa, light emission from nano volumes can be enhanced by coupling to antenna structures. We give a short introduction to antenna theory and discuss recent experiments that show the feasibility of achieving strong field enhancement using resonant dipole antennas for near infrared wavelengths. By scanning an optical antenna fabricated at the apex of an AFM tip over individual quantum dots, we observe enhanced emission of the latter while it is in close proximity of the antenna feed gap. Resonant optical antennas hold promise to be applied for spectroscopic characterization of nano structures with high spatial resolutions and single-molecule sensitivity.

Published
2006
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2. Direct synthesis of lamin A, bypassing prelamin a processing, causes misshapen nuclei in fibroblasts but no detectable pathology in mice

Author

Michael M. Weinstein, Loren G. Fong, Laurent A. Bentolila, Ui Jeong Yun, Hea-Jin Jung, Stephen G. Young, Shao H. Yang, Emily Farber, Jan Lammerding, Javad N. Farahani, Catherine Coffinier, Chika Nobumori, Brandon S.J. Davies, and Ziwei Li

Subjects
congenital, hereditary, and neonatal diseases and abnormalities, animal structures, Blotting, Western, Biology, Biochemistry, Methylation, LMNA, Mice, Gene knockin, medicine, Animals, Nuclear protein, Protein Precursors, Molecular Biology, Conserved Sequence, Crosses, Genetic, Cell Nucleus, Mice, Knockout, integumentary system, nutritional and metabolic diseases, Nuclear Proteins, Cell Biology, Fibroblasts, Embryo, Mammalian, Lamin Type A, Molecular biology, Stop codon, Introns, Cell nucleus, medicine.anatomical_structure, Phenotype, Microscopy, Fluorescence, embryonic structures, Vertebrates, Mutagenesis, Site-Directed, Nuclear lamina, Protein farnesylation, Lamin, Protein Modification, Translational
Abstract

Lamin A, a key component of the nuclear lamina, is generated from prelamin A by four post-translational processing steps: farnesylation, endoproteolytic release of the last three amino acids of the protein, methylation of the C-terminal farnesylcysteine, and finally, endoproteolytic release of the last 15 amino acids of the protein (including the farnesylcysteine methyl ester). The last cleavage step, mediated by ZMPSTE24, releases mature lamin A. This processing scheme has been conserved through vertebrate evolution and is widely assumed to be crucial for targeting lamin A to the nuclear envelope. However, its physiologic importance has never been tested. To address this issue, we created mice with a "mature lamin A-only" allele (Lmna(LAO)), which contains a stop codon immediately after the last codon of mature lamin A. Thus, Lmna(LAO/LAO) mice synthesize mature lamin A directly, bypassing prelamin A synthesis and processing. The levels of mature lamin A in Lmna(LAO/LAO) mice were indistinguishable from those in "prelamin A-only" mice (Lmna(PLAO/PLAO)), where all of the lamin A is produced from prelamin A. Lmna(LAO/LAO) exhibited normal body weights and had no detectable disease phenotypes. A higher frequency of nuclear blebs was observed in Lmna(LAO/LAO) embryonic fibroblasts; however, the mature lamin A in the tissues of Lmna(LAO/LAO) mice was positioned normally at the nuclear rim. We conclude that prelamin A processing is dispensable in mice and that direct synthesis of mature lamin A has little if any effect on the targeting of lamin A to the nuclear rim in mouse tissues.

Published
2010

3. Bow-tie optical antenna probes for single-emitter scanning near-field optical microscopy.

Author

Javad N Farahani, Jürgen Eisler, Dieter W Pohl, Michaël Pavius, Philippe Fl, Philippe Gasser, and Bert Hecht

Subjects
*MICROSCOPY, *QUANTUM dots, *PHOTOLUMINESCENCE, *SPECTRUM analysis
Abstract

A method for the fabrication of bow-tie optical antennas at the apex of pyramidal Si3N4atomic force microscopy tips is described. We demonstrate that these novel optical probes are capable of sub-wavelength imaging of single quantum dots at room temperature. The enhanced and confined optical near-field at the antenna feed gap leads to locally enhanced photoluminescence (PL) of single quantum dots. Photoluminescence quenching due to the proximity of metal is found to be insignificant. The method holds promise for single quantum emitter imaging and spectroscopy at spatial resolution limited by the engineered antenna gap width exclusively. [ABSTRACT FROM AUTHOR]

Published
2007
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