Referate

Ohne Zusammenfassung     

Referate

Ohne Zusammenfassung     

CENP-C is a blueprint for constitutive centromere–associated network assembly within human kinetochores

Kinetochores are multisubunit complexes that assemble on centromeres to bind spindle microtubules and promote faithful chromosome segregation during cell division. A 16-subunit complex named the constitutive centromere–associated network (CCAN) creates the centromere–kinetochore interface. CENP-C, a CCAN subunit, is crucial for kinetochore assembly because it links centromeres with the microtubule-binding interface of kinetochores. The role of CENP-C in CCAN organization, on the other hand, had been incompletely understood. In this paper, we combined biochemical reconstitution and cellular investigations to unveil how CENP-C promotes kinetochore targeting of other CCAN subunits. The so-called PEST domain in the N-terminal half of CENP-C interacted directly with the four-subunit CCAN subcomplex CENP-HIKM. We identified crucial determinants of this interaction whose mutation prevented kinetochore localization of CENP-HIKM and of CENP-TW, another CCAN subcomplex. When considered together with previous observations, our data point to CENP-C as a blueprint for kinetochore assembly.     

Charge Transport Anisotropy in Highly Oriented Thin Films of the Acceptor Polymer P(NDI2OD‐T2)

The nanomorphology of the high mobility polymer poly{[N,N′‐bis(2‐octyldodecyl)‐1,4,5,8‐naphthalenedicarboximide‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} P(NDI2OD‐T2) in thin films is explored as a function of different annealing conditions and correlated to optical and electrical properties. While nanofibrils with face‐on orientation in form I are obtained directly after spin‐coating and annealing below the melt transition temperature, clear evidence of lamellar structures is found after melt‐annealing followed by slow cooling to room temperature. Interestingly these structural changes are accompanied by distinct changes in the absorption patterns. Electron diffraction measurements further show clear transitions towards predominant edge‐on oriented chains in form II upon melt‐annealing. Large‐scale alignment with dichroic ratios up to 10 and improved order is achieved by high temperature rubbing and subsequent post‐rubbing annealing. These highly oriented morphologies allow anisotropic in‐plane charge transport to be probed with top‐gate transistors parallel and perpendicular to the polymer chain direction. Mobilities up to 0.1 cm² V^‐1 s^‐1 are observed parallel to the polymer chain, which is up to 10 times higher than those perpendicular to the polymer chain.     

Voltage‐Induced Formation of Accumulation Layers at Electrode Interfaces in Organic Solar Cells

This work reports on organic bulk heterojunction solar cells based on poly(3‐hexylthiophene) (P3HT) blended with [6,6]‐phenyl‐C61 butyric acid methyl ester (PCBM) in a configuration with so‐called interdigital nanoelectrodes, i.e., vertical electrodes on substrates structured in the submicrometer range. In this setup, both electrodes are in place prior to the deposition of the photoactive blend solution and therefore allow for the application of a voltage during drying of the blend. A strong correlation is observed between the photovoltaic performance of these devices and the voltage that is applied during film formation. Even the polarity of the solar cells can be controlled with this method. It is suggested that this is a consequence of a strong segregation of donor and acceptor phases at the electrode interfaces induced by the applied voltage. Further experiments on planar solar cell geometries, including a solvent‐vapor treatment and the introduction of an additional layer of pure P3HT, as well as numerical simulations, are presented. All results obtained are consistent with the suggested hypothesis.     

Population sex ratio shift from fledging to recruitment: consequences for demography in a philopatric seabird

In many dimorphic bird species, offspring sex ratio is skewed towards the production of the smaller sex. Offspring sex ratio can be biased in monomorphic birds however, and the demographic consequences of such bias are unknown. Sex-specific mortality and dispersal are fundamental mechanisms of sex ratio adjustment at the population level, but evidence for adjustments is weak and feedback into population dynamics poorly understood. Here, we link sex ratio at fledging with sex-specific subadult return and recruitment at the Banter See common tern Sterna hirundo colony. Using molecular sexing methods and a remote detection system, we permanently tracked individuals from four complete cohorts (n=1171 fledglings) across these life-history stages at their natal colony site, which permitted a structured analysis of sex ratio across multiple seasons. Sex ratio shifted significantly from significant daughter dominance at fledging to higher proportions of natal males among recruits; return and recruitment rates of sons were significantly higher than daughters (p≤0.002). No significant between-year differences were detected. 47.4% of natal male recruits were paired with a non-natal female, but only 37.0% of natal female recruits had a non-natal partner. Elasticity analysis suggested that natal males have a greater influence on natal population growth rate than natal females. Sex biased dispersal is the most probable reason for these results indicating higher emigration to and immigration from other colonies in females, the less territorial and less philopatric sex. This pattern may be related to different gender roles in parental duties and with respect to competition for local resources.     

Schriftenschau

Ohne Zusammenfassung     

On the Molecular Origin of Charge Separation at the Donor–Acceptor Interface

Fullerene‐based acceptors have dominated organic solar cells for almost two decades. It is only within the last few years that alternative acceptors rival their dominance, introducing much more flexibility in the optoelectronic properties of these material blends. However, a fundamental physical understanding of the processes that drive charge separation at organic heterojunctions is still missing, but urgently needed to direct further material improvements. Here a combined experimental and theoretical approach is used to understand the intimate mechanisms by which molecular structure contributes to exciton dissociation, charge separation, and charge recombination at the donor–acceptor (D–A) interface. Model systems comprised of polythiophene‐based donor and rylene diimide‐based acceptor polymers are used and a detailed density functional theory (DFT) investigation is performed. The results point to the roles that geometric deformations and direct‐contact intermolecular polarization play in establishing a driving force (energy gradient) for the optoelectronic processes taking place at the interface. A substantial impact for this driving force is found to stem from polymer deformations at the interface, a finding that can clearly lead to new design approaches in the development of the next generation of conjugated polymers and small molecules.