The interaction of a single quantum dot with a bowtie antenna is demonstrated for visible light. The antenna is generated at the apex of a Si3N4 atomic force microscopy tip by focused ion beam milling. When scanned over the quantum dot, its photoluminescence is enhanced while its excited-state lifetime is decreased. Our observations demonstrate that the relaxation channels of a single quantum emitter can be controlled by coupling to an efficiently radiating metallic nanoantenna.

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.Lamin A, one of the principal protein components of the nuclear lamina, is generated from prelamin A by a series of four enzymatic post-translational processing steps (1, 2). First, the cysteine in the C-terminal CAAX motif is farnesylated by protein farnesyltransferase. Second, the last three amino acids of the protein (i.e. the -AAX) are clipped off, a redundant activity of two membrane proteases of the endoplasmic reticulum (ER), 2 RCE1 and ZMPSTE24 (2, 3). Third, the newly exposed farnesylcysteine is methylated by ICMT (4), a membrane methyltransferase of the ER. Finally, the last 15 amino acids of the protein (including the C-terminal farnesylcysteine methyl ester) are clipped off by ZMPSTE24, releasing mature lamin A. Lamin A and lamin C, both "A-type" lamins, are splice variants of LMNA (5, 6). Lamin C does not contain a CAAX motif and therefore does not undergo any of the C-terminal post-translational processing steps.The prelamin A processing pathway has attracted considerable attention from medical geneticists, cell biologists, and pharmacologists (1, 7-11). Hutchinson-Gilford progeria syndrome (HGPS), the classic progeroid disorder of children, is caused by point mutations leading to a 50-amino acid internal deletion within the C-terminal region of prelamin A (7, 8). This deletion does not affect protein farnesylation/methylation but abolishes the final cleavage by ZMPSTE24, resulting in the accumulation of a farnesylated, truncated ...

A method for the fabrication of bow-tie optical antennas at the apex of pyramidal Si 3 N 4 atomic 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.High-precision engineering of prototype devices that show function through their design and high complexity is a key target of applied nanoscale science and nanotechnology. Resonant optical antennas in the field of nano-photonics, with their architecture stimulated by their radio frequency counterparts, synergistically combine (i) electromagnetic field confinement and enhancement defined by the size of their feed gap width and (ii) impedance matching of optical waves mediated by the effective length of their antenna arms [1]. The control of sub-wavelength confined and enhanced optical fields pushes the limit in optical characterization [2][3][4] manipulation [5][6][7], and optimization of single nanoscale light sources for information processing [8][9][10][11] on the nanometre scale. In particular, the impedance matching of optical waves opens an efficient pathway to transfer near-field information into the optical far-field, and vice versa [12].In this paper, we present a strategy for designing bow-tie optical antennas at the apex of Si 3 N 4 atomic force microscopy (AFM) cantilever tips. We demonstrate that, even in this complex geometry, it is possible to control key antenna parameters such as overall length and width of the feed gap by focused-ion-beam milling. Merging well-established scanning probe technology with the concept of resonant optical antennas [13,14] leads to a powerful new method of scanning optical microscopy in which an engineered optical hot spot is used as an optical probe [15]. We demonstrate the application of scanning optical antennas to the imaging of single quantum dots at room temperature. We show that the emission of individual quantum dots is enhanced when scanned across the antenna feed gap while concomitantly their excited-state lifetime is reduced. The field confinement, characterized by

suitably shaped metal nanostructures 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.