Optical gating with organic building blocks : A quantitative model for the fluorescence modulation of photochromic perylene bisimide dithienylcyclopentene triads

We investigated the capability of molecular triads, consisting of two strong fluorophores that were covalently linked to a photochromic molecule, for optical gating. Therefore we monitored the fluorescence intensity of the fluorophores as a function of the isomeric state of the photoswitch. From the analysis of our data we develop a kinetic model that allows us to predict quantitatively the degree of the fluorescence modulation as a function of the mutual intensities of the lasers that are used to induce the fluorescence and the switching of the photochromic unit. We find that the achievable contrast for the modulation of the fluorescence depends mainly on the intensity ratio of the two light beams and appears to be very robust against absolute changes of these intensities. The latter result provides valuable information for the development of all-optical circuits which would require to handle different signal strengths for the input and output levels

PARP1 proximity proteomics reveals interaction partners at stressed replication forks

PARP1 mediates poly-ADP-ribosylation of proteins on chromatin in response to different types of DNA lesions. PARP inhibitors are used for the treatment of BRCA1/2-deficient breast, ovarian, and prostate cancer. Loss of DNA replication fork protection is proposed as one mechanism that contributes to the vulnerability of BRCA1/2-deficient cells to PARP inhibitors. However, the mechanisms that regulate PARP1 activity at stressed replication forks remain poorly understood. Here, we performed proximity proteomics of PARP1 and isolation of proteins on stressed replication forks to map putative PARP1 regulators. We identified TPX2 as a direct PARP1-binding protein that regulates the auto-ADP-ribosylation activity of PARP1. TPX2 interacts with DNA damage response proteins and promotes homology-directed repair of DNA double-strand breaks. Moreover, TPX2 mRNA levels are increased in BRCA1/2-mutated breast and prostate cancers, and high TPX2 expression levels correlate with the sensitivity of cancer cells to PARP-trapping inhibitors. We propose that TPX2 confers a mitosis-independent function in the cellular response to replication stress by interacting with PARP1

Light controls light: single molecules as optical switches

In recent years much attention has been given to design multistate molecular components with functionalities that cover the range from simple switches to logic gates [1-3]. In this regard photochromic molecules, i.e., molecules that can be interconverted between two bistable forms by light, have played an important role. Promising candidates that fulfill obvious demands such as high photochemical/ photophysical stability and high fatigue resistance are compounds of the family of diarylethenes [2,3]. However, a serious drawback of this class of molecules is a low fluorescence quantum yield. Therefore we adapted the strategy developed by Irie and coworkers [2,3], to chemically synthesize complex tailor-made triads consisting of a photochromic dithienylcyclopentene (DCP) unit covalently linked to two peryline bisimide (PBI) molecules that are known as strong fluorophores, see fig.1 inset top left. This facilitates the combination of high fatigue resistance and high fluorescence quantum yield. Illumination with light in the UV spectral region induces a ring-closure reaction of the DCP and leads to a state with suppressed fluorescence from the PBIs, whereas light in the VIS spectral region yields a ring opening reaction of the DCP and restores the fluorescence from the PBI units. This allowed us to verify functionalities like optical gating and amplifying, yet where the electrons have been replaced by photons as signal carriers [4-6], see fig.1

Light controls light: single molecules as optical switches

In recent years much attention has been given to design multistate molecular components with functionalities that cover the range from simple switches to logic gates [1-3]. In this regard photochromic molecules, i.e., molecules that can be interconverted between two bistable forms by light, have played an important role. Promising candidates that fulfill obvious demands such as high photochemical/ photophysical stability and high fatigue resistance are compounds of the family of diarylethenes [2,3]. However, a serious drawback of this class of molecules is a low fluorescence quantum yield. Therefore we adapted the strategy developed by Irie and coworkers [2,3], to chemically synthesize complex tailor-made triads consisting of a photochromic dithienylcyclopentene (DCP) unit covalently linked to two peryline bisimide (PBI) molecules that are known as strong fluorophores, see fig.1 inset top left. This facilitates the combination of high fatigue resistance and high fluorescence quantum yield. Illumination with light in the UV spectral region induces a ring-closure reaction of the DCP and leads to a state with suppressed fluorescence from the PBIs, whereas light in the VIS spectral region yields a ring opening reaction of the DCP and restores the fluorescence from the PBI units. This allowed us to verify functionalities like optical gating and amplifying, yet where the electrons have been replaced by photons as signal carriers [4-6], see fig.1

Finanzmärkte – Unternehmungen – Informationen: Ergebnisse des Projektes im Wintersemester 2016/2017

Der vorliegende Beitrag der Wirtschaftswissenschaftlichen Schriften ist ein Sammelband, der die Beiträge der Studierenden des 2. Fachsemesters im Masterstudiengang General Management aus dem Wintersemester 2016/2017 umfasst. Die Einzelbeiträge wurden in einer zwei Monate dauernden Projektarbeit im Herbst 2016 erarbeitet und im Januar 2017 präsentiert. Der Themenschwerpunkt für dieses Jahr lag auf dem Bereich "Immobilien/Wohnungspolitik". Innerhalb dieser Vorgabe wurde ein breites Spektrum bearbeitet, das von der Gefahr einer Immobilienpreisblase über wohnungspolitische Themen (Gentrifizierung, Mietpreisbremse, sozialer Wohnungsbau) bis hin zum Markt für Tiny-Houses reichte. Das Besondere dieser Ausarbeitungen liegt darin, dass sie in Form eines journalistischen Artikels aufgebaut sind und die Autoren die Aufgabe hatten, eine auch für Nichtfachleute geeignete Form der Darstellung zu finden. Besonderer Wert wurde auch auf einen gut lesbaren Schreibstil und die Vielfalt der Gestaltungsformen gelegt. Die Arbeiten liegen hier in der Originalversion vor und wurden nicht redigiert. Die Fakten wurden nach bestem Wissen ermittelt, jedoch besteht kein Anspruch auf Richtigkeit und Vollständigkeit