Realization of two Fourier-limited solid-state single-photon sources

We demonstrate two solid-state sources of indistinguishable single photons. High resolution laser spectroscopy and optical microscopy were combined at T = 1.4 K to identify individual molecules in two independent microscopes. The Stark effect was exploited to shift the transition frequency of a given molecule and thus obtain single photon sources with perfect spectral overlap. Our experimental arrangement sets the ground for the realization of various quantum interference and information processing experiments.Comment: 6 page

Molecules as Sources for Indistinguishable Single Photons

We report on the triggered generation of indistinguishable photons by solid-state single-photon sources in two separate cryogenic laser scanning microscopes. Organic fluorescent molecules were used as emitters and investigated by means of high resolution laser spectroscopy. Continuous-wave photon correlation measurements on individual molecules proved the isolation of single quantum systems. By using frequency selective pulsed excitation of the molecule and efficient spectral filtering of its emission, we produced triggered Fourier-limited single photons. In a further step, local electric fields were applied to match the emission wavelengths of two different molecules via Stark effect. Identical single photons are indispensible for the realization of various quantum information processing schemes proposed. The solid-state approach presented here prepares the way towards the integration of multiple bright sources of single photons on a single chip.Comment: Accepted for publication in J. Mod. Opt. This is the original submitted versio

Critical review of supercritical carbon dioxide extraction of selected oil seeds

Supercritical carbon dioxide extraction, as a relatively new separation technique, can be used as a very efficient process in the production of essential oils and oleoresins from many of plant materials. The extracts from these materials are a good basis for the new pharmaceutical products and ingredients in the functional foods. This paper deals with supercritical carbon dioxide extraction of selected oil seeds which are of little interest in classical extraction in the food industry. In this article the process parameters in the supercritical carbon dioxide extraction, such as pressure, temperature, solvent flow rate, diameter of gound materials, and moisture of oil seed were presented for the following seeds: almond fruits, borage seed, corn germ, grape seed, evening primrose, hazelnut, linseed, pumpkin seed, walnut, and wheat germ. The values of investigated parameters in supercritical extraction were: pressure from 100 to 600 bar, temperature from 10 to 70oC, diameter of grinding material from 0.16 to 2.0 mm, solvent flow used from 0.06 to 30.0 kg/h, amount of oil in the feed from 10.0 to 74.0%, and moisture of oil seed from 1.1 to 7.5%. The yield and quality of the extracts of all the oil seeds as well as the possibility of their application in the pharmaceutical and food, industries were analyzed

Detection of Single Molecules Illuminated by a Light-Emitting Diode

Optical detection and spectroscopy of single molecules has become an indispensable tool in biological imaging and sensing. Its success is based on fluorescence of organic dye molecules under carefully engineered laser illumination. In this paper we demonstrate optical detection of single molecules on a wide-field microscope with an illumination based on a commercially available, green light-emitting diode. The results are directly compared with laser illumination in the same experimental configuration. The setup and the limiting factors, such as light transfer to the sample, spectral filtering and the resulting signal-to-noise ratio are discussed. A theoretical and an experimental approach to estimate these parameters are presented. The results can be adapted to other single emitter and illumination schemes.Comment: 7 pages, 5 figure

Acupuncture in Seasonal Allergic Rhinitis (ACUSAR) - Design and Protocol of a Randomised Controlled Multi-Centre Trial

Background: We report on the study design and protocol of a randomised controlled trial (Acupuncture in Seasonal Allergic Rhinitis, ACUSAR) that investigates the efficacy of acupuncture in the treatment of seasonal allergic rhinitis (SAR). Objective: To investigate whether acupuncture is non-inferior or superior to (a) penetrating sham acupuncture and (b) rescue medication in the treatment of SAR. Design: 3-armed, randomised controlled multi-centre trial with a total follow-up time of 16 weeks in the 1st year and 8 weeks in the 2nd year. Setting: 41 physicians in 37 out-patient units in Germany specialised in acupuncture treatment. Patients: 400 seasonal allergic rhinitis patients with clinical symptoms and test-positive (skin-prick test and/or specific IgE) to both birch and grass pollen. Interventions: Patients will be randomised in a 2:1:1 ratio to one of three groups: (a) semi-standardised acupuncture plus rescue medication (cetirizine); (b) penetrating sham acupuncture at non-acupuncture points plus rescue medication; or (c) rescue medication alone for 8 weeks (standard treatment group). Acupuncture and sham acupuncture will consist of 12 treatments per patient over 8 weeks. Main Outcome Measures: Average means of the Rhinitis Quality of Life Questionnaire (RQLQ) overall score and the Rescue Medication Score (RMS) between weeks 6 and 8 in the first year, adjusted for baseline values. Outlook: The results of this trial available in 2011 will have a major impact on the decision of whether acupuncture should be considered as a therapeutic option in the treatment of SAR

Strong extinction of a laser beam by a single molecule

We present an experiment where a single molecule strongly affects the amplitude and phase of a laser field emerging from a subwavelength aperture. We achieve a visibility of -6% in direct and +10% in cross-polarized detection schemes. Our analysis shows that a close to full extinction should be possible using near-field excitation.Comment: 5 pages, 4 figures, submitted to PR

Spontaneous emission enhancement of a single molecule by a double-sphere nanoantenna across an interface

We report on two orders of magnitude reduction in the fluorescence lifetime when a single molecule placed in a thin film is surrounded by two gold nanospheres across the film interface. By attaching one of the gold particles to the end of a glass fiber tip, we could control the modification of the molecular fluorescence at will. We find a good agreement between our experimental data and the outcome of numerical calculations

Translation elongation factor P and its post-translational modification enzyme EpmA

Protein translation is a non-uniform process, whereby especially proline-containing motifs lead to ribosome stalling events. Elongation factor P (EF P) rescues the ribosome by stimulation of peptidyl transfer. The four known subgroups of bacterial EF-Ps either require post-translational modification (PTM) established by EpmABC/EarP/YmfI or are functional without PTM. In Escherichia coli, the aminomutase EpmB converts (S)-α-lysine into (R)-β-lysine, which is subject to a two-step reaction catalyzed by lysyl-tRNA synthetase paralog EpmA. First, (R)-β-lysyl-adenylate is formed, from which the β-lysyl moiety is subsequently transferred to the ε-amino group of lysine 34 of EF P. This thesis focuses on the interplay of EF-P and EpmA which ensures EF P functionality in vivo and was used to modify EF-P with seven unnatural substrates in vitro. To detect PTM status two universal peptide antibodies, nonselective for the bacterial origin of EF-P, were generated and three subtypes of one-dimensional isoelectric focusing were established (native/denaturating horizontal, vertical). EpmA and EF-P protein copy numbers indicated balanced coordination to ensure outright modification status of EF-P during all growth phases, but no mutual regulation. EpmA’s donor substrate promiscuity was pinpointed to permit C6 scaffolds with at least an amino group at α- ((R/S)-α-lysine, 5-hydroxy-(S)-α-lysine), β- ((R/S)-β-lysine, (R)-3-aminocapronic acid) or ε-position (6-aminocapronic acid). In addition, EpmA variant A298G enabled modification of EF-P with (S)-α-ornithine. For the first time, known natural PTMs of EF P were expanded by seven synthetic PTMs. In vitro transcription translation assay demonstrated superiority of (R)-β-lysylation in ribosome rescue, explaining its evolutionary selection. Modification of EF-P with (S)-α-lysine was successfully achieved in vivo, when (R)-β-lysine synthesis was impeded (E. coli ΔepmB) and epmA(_A298G) overexpressed. In Bacillus subtilis, the ratio of unmodified-to-modified EF P varied over time. Out of 13 tested aminotransferase genes dat, epsN, gsaB, ilvK and yhdR are potentially involved in the yet unsolved modification pathway. In summary, the present work not only provides new biochemical insights into the functionalization of EF-P, but also paves the way to modify proteins post-translationally using EpmA.Die Translation von Proteinen ist kein gleichförmiger Prozess. Besonders bei Polyprolinmotiven treten Verzögerungen des Ribosoms auf. Hier übernimmt Elongationsfaktor P (EF-P) eine helfende Funktion und stimuliert den Peptidyltransfer. Die vier bekannten Gruppen von bakteriellen EF-P benötigen entweder posttranslationale Modifikation (PTM) durch EpmABC/EarP/YmfI, oder sind ohne PTM funktional. In Escherichia coli wandelt die Aminomutase EpmB (S)-α-Lysin in (R)-β-Lysin um. Ein Paralog der Lysyl-tRNA-Synthetase, EpmA, katalysiert die folgende zweistufige Reaktion. Erst wird (R)-β-Lysyladenylat gebildet, dessen β-Lysylgruppe dann auf die ε-Aminogruppe von Lysin 34 von EF-P übertragen wird. Diese Dissertation widmet sich dem Zusammenspiel von EF-P und EpmA. Dieses stellt in vivo die Funktion von EF-P sicher, in vitro erlaubt es die Modifikation von EF P mit sieben unnatürlichen Substraten. Zur Detektion des PTM Status wurden zwei universelle Peptidantikörper etabliert, die EF-P unabhängig von dessen bakterieller Herkunft detektieren, sowie drei Formen der eindimensionalen Isoelektrischen Fokussierung (nativ/denaturierend horizontal, vertikal). Die Kopienzahlen von EpmA und EF-P sind aufeinander abgestimmt, um vollständige Modifikation von EF-P in allen Wachstumsphasen sicherzustellen. Sie regulieren sich aber nicht gegenseitig. Die Promiskuität von EpmA erlaubt Donorsubstrate mit C6-Ketten, die zumindest eine Aminogruppe in α- ((R/S)-α-Lysin, 5-Hydroxy-(S)-α-lysin), β- ((R/S)-β-Lysin, (R)-3-Aminohexansäure) oder ε-Position (6-Aminohexansäure) haben. Zusätzlich ermöglicht die Enzymvariante EpmA_A298G (S)-α-Ornithylierung von EF-P. Erstmals konnten so die natürlichen PTMs von EF-P um sieben synthetische PTMs erweitert werden. In vitro Transkriptions/Translations-Assays zeigten die wirkungsvollste Ribosomen-rettung bei (R)-β-lysyliertem EF-P, was dessen evolutionäre Auswahl erklärt. In vivo gelang die Modifikation von EF-P mit (S)-α-Lysin, wenn die Fähigkeit zur (R)-β-Lysinsynthese fehlte (E. coli ΔepmB) und epmA(_A298G) überexprimiert wurde. In Bacillus subtilis variiert das Verhältnis von unmodifiziertem zu modifiziertem EF-P. Von 13 untersuchten Genen, die Aminotransferasen kodieren, sind dat, epsN, gsaB, ilvK und yhdR möglicherweise am ungeklärten Modifikationsweg beteiligt. Zusammengefasst liefert die vorliegende Arbeit nicht nur neue biochemische Einsichten in die Funktionalisierung von EF-P, sondern eröffnet auch einen neuen Weg, Proteine mittels EpmA posttranslational zu modifizieren