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Probing the Peptidyl Transferase Center of Ribosomes Containing Mutant 23s rRNA with Photoreactive tRNACaci, Nicole C 01 January 2008 (has links) (PDF)
There is strong crystallographic evidence that the 23S rRNA is the only catalytic entity in the peptidyl transferase center. Various mechanisms for the catalysis of peptidyl transfer have been proposed. Recently, attention has been given to the idea that the 23S rRNA simply acts to position the tRNA for spontaneous peptidyl transfer and that chemical catalysis may play only a secondary role. Conserved nucleotides U2585 and U2506 are thought to be involved in positioning the 3’ ends of A- and P-site substrates based on the crystallographic evidence, and because mutagenesis at these sites severely impairs peptide bond formation. In this study, pure populations of ribosomes with either U2585A or U2506G mutations in the 23S rRNA were analyzed to test the hypothesis that substitutions at nucleotides U2585 and U2506 in the peptidyl transferase center impair peptide bond formation by altering the position of the 3’ end of P-site tRNA relative to the 23S rRNA. Pure populations of mutant or wild-type ribosomes were obtained by an affinity tagging system and probed with 32P-labeled [2N3A76]tRNAPhe to determine how the 3’ end of tRNA interacts with the ribosomal proteins and 23S RNA at the peptidyl transferase center. Some of the data for the ribosomes with a G at position 2506 are consistent with a model suggested by Schmeing and coworkers in which nucleotide U2506 breaks from its original wobble base pair with nucleotide G2583 during A-site tRNA binding and swings towards the 3’ end of P-site tRNA, while nucleotide U2585 simultaneously moves away from the 3’ end of P-site tRNA.
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Development of Photoreactive Organic Compounds with Large Two-Photon Absorption Cross SectionsUrdabayev, Nurtay 01 June 2006 (has links)
No description available.
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Apparatus to Deliver Light to the Tip-sample Interface of an Atomic Force Microscope (AFM)Thoreson, Erik J. 03 October 2002 (has links)
"An apparatus for the delivery of radiation to the tip-sample interface of an Atomic Force Microscope (AFM) is demonstrated. The Pulsed Light Delivery System (PLDS) was fabricated to probe photoinduced conformational changes of molecules using an AFM. The PLDS is 67 mm long, 59 mm wide, and 21 mm high, leaving clearance to mount the PLDS and a microscope slide coated with a thin film of photoactive molecules beneath the cantilever tip of a stand-alone AFM. The PLDS is coupled into a fiber pigtailed Nd:Yag frequency doubled laser, operating at a wavelength of 532 nm. The radiation delivered to a sample through the PLDS can be configured for continuous or pulsed mode. The maximum continuous wave (CW) power delivered was 0.903 mW and the minimum pulse width was 12.3 ms (maximal 401 ms), corresponding to a minimal energy of 0.150 nJ (maximal 362 nJ), and had a cycle duration of 10.0 ms. The PLDS consists of micro-optical components 3.0 mm and smaller in diameter. The optical design was inspired by the three-beam pick-up method used in CD players, which could provide a method to focus the pulse of light onto the sample layer. In addition, the system can be easily modified for different operational parameters (pulse width, wavelength, and power). As proof that the prototype design works, we observed a photoinduced ‘bimetallic’ bending of the cantilever, as evidenced by observing no photoinduced bending when a reflective-coated cantilever was replaced by an uncoated cantilever. Using the apparatus will allow investigation of many different types of molecules exhibiting photoinduced isomerization."
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Two-dimensional CCD position sensor system for active magnetic bearingsSithole, Phila Elvis January 2007 (has links)
M. Tech. Digital Technology. / This dissertation reports on an optical-based two-dimensional position sensor for use in
Active Magnetic Bearings (AMB) to measure the position of the levitated rotor. The
motivation for the deployment of optical technology is the well-known advantage of high
precision contactless displacement measurement. The radial and axial edges of the rotor are
illuminated by red and green laser beams respectively. The position of the rotor is
determined from its image projected on a Charge Coupled Device (CCD) sensor. The
measuring principle is demonstrated as a position sampler in the closed loop control of an
active magnetic bearing model.
The image representing the position is processed with a real-time algorithm on a Field
Programmable Logic Gate Array. The principle of operation of a CCD as a position sensor
is analysed in order to establish how the image captured by the CCD can be processed to
determine the position of the rotor. A simple AMB is modelled in which the sensor acts as
a feedback position device. The main objective of the model is to evaluate the accuracy of
the system. The purpose of the overall sensing technique to be used is to achieve highly
accurate and precise measurements with CCD-based optical metrology.
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Synthese photoreaktiver Polymere zur optischen Strukturierung dünner SchichtenGeorgi, Ulrike 01 July 2014 (has links) (PDF)
Diese Arbeit beschäftigt sich mit der Synthese neuer photoreaktiver Polymere, die bei Bestrahlung mit Licht (Hg-Dampflampe, fs-gepulster Ti:Sa-Laser) definierte Reaktionen durchlaufen. Mittels kontrolliert-radikalischer Polymerisation und anschließender polymeranaloger Reaktion wurden verschiedene Azobenzen-Derivate, Arylazosulfonat-Derivate und photolabil geschützte Aminogruppen (Nitroveratryloxycarbonyl, Nvoc) in Methacrylat-Polymere eingeführt. Diese Strukturen wurden ausführlich hinsichtlich ihrer Struktur und vor allem ihrer photochemischen Eigenschaften (Extinktionskoeffizienten, Zerfallskinetik) untersucht. Dünne Schichten (d<30nm) der so hergestellten Materialien wurden bei der Entwicklung einer neuen photolithographischen Methode, der plasmonischen Nanolithographie, eingesetzt.
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Synthese photoreaktiver Polymere zur optischen Strukturierung dünner SchichtenGeorgi, Ulrike 09 May 2014 (has links)
Diese Arbeit beschäftigt sich mit der Synthese neuer photoreaktiver Polymere, die bei Bestrahlung mit Licht (Hg-Dampflampe, fs-gepulster Ti:Sa-Laser) definierte Reaktionen durchlaufen. Mittels kontrolliert-radikalischer Polymerisation und anschließender polymeranaloger Reaktion wurden verschiedene Azobenzen-Derivate, Arylazosulfonat-Derivate und photolabil geschützte Aminogruppen (Nitroveratryloxycarbonyl, Nvoc) in Methacrylat-Polymere eingeführt. Diese Strukturen wurden ausführlich hinsichtlich ihrer Struktur und vor allem ihrer photochemischen Eigenschaften (Extinktionskoeffizienten, Zerfallskinetik) untersucht. Dünne Schichten (d<30nm) der so hergestellten Materialien wurden bei der Entwicklung einer neuen photolithographischen Methode, der plasmonischen Nanolithographie, eingesetzt.:INHALTSVERZEICHNIS
ABBILDUNGSVERZEICHNIS
TABELLENVERZEICHNIS
ABKÜRZUNGS- UND SYMBOLVERZEICHNIS
1 EINLEITUNG UND ZIELSTELLUNG
2 THEORETISCHE GRUNDLAGEN
2.1 PHOTOREAKTIVE POLYMERE
2.1.1 Azobenzenhaltige Polymere und deren Anwendungen
2.1.2 Arylazosulfonathaltige Polymere und deren Anwendungen
2.1.3 Photolabil geschützte Amine in Polymeren und zur Oberflächenstrukturierung
2.2 NICHT-LINEAR OPTISCHE EFFEKTE - FREQUENZVERDOPPLUNG
2.3 OBERFLÄCHENPLASMONENRESONANZ UND SHG AN METALLISCHEN NANOPARTIKELN
2.4 PHOTOCHEMISCHE STRUKTURIERUNG DÜNNER SCHICHTEN
2.5 NANOLITHOGRAPHISCHE STRUKTURIERUNG MITTELS PLASMONISCHER EFFEKTE AN METALLNANOSTRUKTUREN
3 ERGEBNISSE UND DISKUSSION
3.1 AZOBENZENHALTIGE POLYMERE
3.1.1 Synthese niedermolekularer Azobenzen-Derivate
3.1.2 Anbindung an Polymermatrix
3.1.3 Photochemische matrixabhängige Untersuchung der Isomerisationskinetik
3.1.4 Bestrahlung in dünnen Schichten mit gepulstem Femtosekunden-Laser
3.2 ARYLAZOSULFONATHALTIGE POLYMERE
3.2.1 Kontrolliert-radikalische Polymerisation von Arylazosulfonat-Monomeren
3.2.1.1 Synthese der arylazosulfonathaltigen Monomere
3.2.1.2 RAFT-Polymerisation von (AS-Mon2)
3.2.2 Polymeranaloge Einführung von Arylazosulfonateinheiten
3.2.3 Präparation und Bestrahlung dünner Schichten
3.3 PHOTOLABIL GESCHÜTZTE AMINOPOLYMERE
3.3.1 Synthese von statistischen Nvoc-geschützten Aminocopolymeren
3.3.1.1 Anbindung des Nvoc-geschützten Amins über Esterbindung
3.3.1.2 Anbindung des Nvoc-geschützten Amins über Reaktion mit Nvoc-Cl
3.3.2 Nvoc-haltige Diblockcopolymere
3.3.2.1 Synthese von P(MMA-co-GMA)-b-P(MMA-co-NvocCMS)
3.3.2.2 Synthese von P(MMA-co-MAA)-b-P(MMA-co-NvocAEMA)
3.3.3 Präparation dünner Schichten der (Block-)Copolymere
3.3.4 Bestrahlung mit gepulstem Femtosekunden-Laser
4 ZUSAMMENFASSUNG UND AUSBLICK
5 EXPERIMENTALTEIL
5.1 ANALYTISCHE METHODEN
5.2 AUFBAU FÜR DIE FS-LASER-BESTRAHLUNG
5.3 VERWENDETE CHEMIKALIEN
5.4 SYNTHESEN
5.4.1 Azobenzen-Derivate
5.4.1.1 Niedermolekulare Verbindungen
5.4.1.2 Polymerisationen und polymeranaloge Reaktionen
5.4.2 Arylazosulfonate
5.4.2.1 Niedermolekulare Verbindungen
5.4.2.2 Freie radikalische Polymerisation
5.4.2.3 RAFT-Polymerisationenen
5.4.2.4 Polymeranaloge Reaktion
5.4.3 Nvoc-geschützte (Block-)Copolymere
5.4.3.1 Niedermolekulare Verbindungen
5.4.3.2 Polymerisationen
5.4.3.3 Polymeranaloge Reaktionen
5.5 WAFERREINIGUNG UND PRÄPARATION DÜNNER SCHICHTEN
LITERATURVERZEICHNIS
DANKSAGUNG
VERSICHERUNG
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