Spektroskopische Eigenschaften kovalent an Glas gebundener Fluoreszenzfarbstoffe und farbstoffmarkierter Peptide

Aufgabe dieser Arbeit war es zu zeigen, dass man sowohl unterschiedlich markierte Peptide, als auch gleich markierte Peptide mit und ohne Tryptophan in ihrer spezifischen Umgebung anhand ihrer Fluoreszenzlebensdauer auf Einzelmolekülebene mit hoher Sicherheit identifizieren und unterscheiden kann. Zu diesem Zweck wurden Markierungsfarbstoffe in Lösung und kovalent auf amino-modifizierte Glasoberflächen gebunden untersucht. Ein Peptid enthält Trp, das andere eine nicht-kopplungsfähige Aminosäure. Der Farbstoff wurde an einen zur variablen Aminosäure benachbarten Lys-Rest gebunden. Die farbstoffmarkierten Peptide wurden dann über ihren C-Terminus an amino-modifizierte Glasoberflächen gekoppelt. Die auf trockenen Glasoberflächen gebundenen Fluoreszenzfarbstoffe und farbstoffmarkierten Peptide wurden mittels konfokaler spektral-auflösender Fluoreszenz-Lebensdauer-Mikroskopie (SFLIM) untersucht. Weitere Messungen erfolgten nach Zugabe einer Flüssigkeit (FTP), die die auf der Oberfläche liegenden Moleküle aufrichtet und damit eine andere Farbstoffumgebung schafft. An den Farbstoff-Peptiden von MR121 war ein markanter Abfall der Lebensdauer durch die Wechselwirkung mit Trp zu beobachten. Carbocyanin-Farbstoffe wie Cy5 zeigten keine spektroskopischen Unterschiede durch die Nähe zu Trp. Allerdings muss sich Trp in unmittelbarer Nachbarschaft zum Farbstoff befinden. Schon eine Aminosäure mehr zwischen Trp und Lys-MR121 verringert die gegenseitige Wechselwirkung so stark, dass praktisch kein Unterschied mehr in den Lebensdauern mit und ohne Trp erkennbar ist. Die reinen Farbstoffe, gemischt auf Glasoberflächen gekoppelt, konnten auf Einzelmolekülebene mit einer Zuordnungssicherheit, aus der Überlappung der Gauß-Kurven ihrer Lebensdauerverteilungen errechnet, von 92 für Cy5/MR121 insgesamt unterschieden werden. Für unterschiedlich markierte Peptide wurden Sicherheiten von 99 für Uni370-Cy5/Uni370-MR121 insgesamt und von 98 für Uni371-Cy5/Uni371-MR121 insgesamt gefunden

D-brane superpotentials and RG flows on the quintic

The behaviour of D2-branes on the quintic under complex structure deformations is analysed by combining Landau-Ginzburg techniques with methods from conformal field theory. It is shown that the boundary renormalisation group flow induced by the bulk deformations is realised as a gradient flow of the effective space time superpotential which is calculated explicitly to all orders in the boundary coupling constant.Comment: 24 pages, 1 figure, v2:Typo in (3.14) correcte

Antiarrhythmic Medication in Neonates and Infants with Supraventricular Tachycardia

Supraventricular tachycardia (SVT) is the most common arrhythmia in neonates and infants, and pharmacological therapy is recommended to prevent recurrent episodes. This retrospective study aims to describe and analyze the practice patterns, effectiveness, and outcome of drug therapy for SVT in patients within the first year of life. Among the 67 patients analyzed, 48 presented with atrioventricular re-entrant tachycardia, 18 with focal atrial, and one with atrioventricular nodal re-entrant. Fetal tachycardia was reported in 27%. Antiarrhythmic treatment consisted of beta-receptor blocking agents in 42 patients, propafenone in 20, amiodarone in 20, and digoxin in 5. Arrhythmia control was achieved with single drug therapy in 70% of the patients, 21% needed dual therapy, and 6% triple. Propafenone was discontinued in 7 infants due to widening of the QRS complex. After 12 months (6-60), 75% of surviving patients were tachycardia-free and discontinued prophylactic treatment. Patients with fetal tachycardia had a significantly higher risk of persistent tachycardia (p: 0.007). Prophylactic antiarrhythmic medication for SVT in infancy is safe and well tolerated. Arrhythmia control is often achieved with single medication, and after cessation, most patients are free of arrhythmias. Infants with SVT and a history of fetal tachycardia are more prone to suffer from persistent SVT and relapses after cessation of prophylactic antiarrhythmic medication than infants with the first episode of SVT after birth

Advanced cell culture performance by rational media design based on in depth process understanding

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Matrix factorisations and D-branes on K3

D-branes on K3 are analysed from three different points of view. For deformations of hypersurfaces in weighted projected space we use geometrical methods as well as matrix factorisation techniques. Furthermore, we study the D-branes on the T^4/\Z_4 orbifold line in conformal field theory. The behaviour of the D-branes under deformations of the bulk theory are studied in detail, and good agreement between the different descriptions is found.Comment: 35 pages, no figure

Symmetries of perturbed conformal field theories

The symmetries of perturbed conformal field theories are analysed. We explain which generators of the chiral algebras of a bulk theory survive a perturbation by an exactly marginal bulk field. We also study the behaviour of D-branes under current-current bulk deformations. We find that the branes always continue to preserve as much symmetry as they possibly can, i.e. as much as is preserved in the bulk. We illustrate these findings with several examples, including permutation branes in WZW models and B-type D-branes in Gepner models.Comment: 30 pages, 3 figures. V2: Small error in eq. (2.14) correcte

Ligand crowding at a nascent signal sequence

We have systematically analyzed the molecular environment of the signal sequence of a growing secretory protein from Escherichia coli using a stage- and site-specific cross-linking approach. Immediately after emerging from the ribosome, the signal sequence of pOmpA is accessible to Ffh, the protein component of the bacterial signal recognition particle, and to SecA, but it remains attached to the surface of the ribosome via protein L23. These contacts are lost upon further growth of the nascent chain, which brings the signal sequence into sole proximity to the chaperone Trigger factor (TF). In its absence, nascent pOmpA shows extended contacts with L23, and even long chains interact in these conditions proficiently with Ffh. Our results suggest that upon emergence from the ribosome, the signal sequence of an E. coli secretory protein gradually becomes sequestered by TF. Although TF thereby might control the accessibility of pOmpA's signal sequence to Ffh and SecA, it does not influence interaction of pOmpA with SecB