@article{SaffertAdamlaSchiewecketal.2016, author = {Saffert, Paul and Adamla, Frauke and Schieweck, Rico and Atkins, John F. and Ignatova, Zoya}, title = {An Expanded CAG Repeat in Huntingtin Causes+1 Frameshifting}, series = {The journal of biological chemistry}, volume = {291}, journal = {The journal of biological chemistry}, publisher = {American Society for Biochemistry and Molecular Biology}, address = {Bethesda}, issn = {0021-9258}, doi = {10.1074/jbc.M116.744326}, pages = {18505 -- 18513}, year = {2016}, abstract = {Maintenance of triplet decoding is crucial for the expression of functional protein because deviations either into the -1 or +1 reading frames are often non-functional. We report here that expression of huntingtin (Htt) exon 1 with expanded CAG repeats, implicated in Huntington pathology, undergoes a sporadic +1 frameshift to generate from the CAG repeat a trans-frame AGC repeat-encoded product. This +1 recoding is exclusively detected in pathological Htt variants, i.e. those with expanded repeats with more than 35 consecutive CAG codons. An atypical +1 shift site, UUC C at the 5 end of CAG repeats, which has some resemblance to the influenza A virus shift site, triggers the +1 frameshifting and is enhanced by the increased propensity of the expanded CAG repeats to form a stem-loop structure. The +1 trans-frame-encoded product can directly influence the aggregation of the parental Htt exon 1.}, language = {en} } @article{DragoPawlakWeithoff2020, author = {Drago, Claudia and Pawlak, Julia and Weithoff, Guntram}, title = {Biogenic aggregation of small microplastics alters their ingestion by a common freshwater micro-invertebrate}, series = {Frontiers in Environmental Science}, volume = {8}, journal = {Frontiers in Environmental Science}, publisher = {Frontiers Media}, address = {Lausanne}, issn = {2296-665X}, doi = {10.3389/fenvs.2020.574274}, pages = {11}, year = {2020}, abstract = {In recent years, increasing concerns have been raised about the environmental risk of microplastics in freshwater ecosystems. Small microplastics enter the water either directly or accumulate through disintegration of larger plastic particles. These particles might then be ingested by filter-feeding zooplankton, such as rotifers. Particles released into the water may also interact with the biota through the formation of aggregates, which might alter the uptake by zooplankton. In this study, we tested for size-specific aggregation of polystyrene microspheres and their ingestion by a common freshwater rotifer Brachionus calyciflorus. The ingestion of three sizes of polystyrene microspheres (MS) 1-, 3-, and 6-mu m was investigated. Each MS size was tested in combination with three different treatments: MS as the sole food intake, MS in association with food algae and MS aggregated with biogenic matter. After 72 h incubation in pre-filtered natural river water, the majority of the 1-mu m spheres occurred as aggregates. The larger the particles, the higher the relative number of single particles and the larger the aggregates. All particles were ingested by the rotifer following a Type-II functional response. The presence of algae did not influence the ingestion of the MS for all three sizes. The biogenic aggregation of microspheres led to a significant size-dependent alteration in their ingestion. Rotifers ingested more microspheres (MS) when exposed to aggregated 1- and 3-mu m MS as compared to single spheres, whereas fewer aggregated 6-mu m spheres were ingested. This indicates that the small particles when aggregated were in an effective size range for Brachionus, while the aggregated larger spheres became too large to be efficiently ingested. These observations provide the first evidence of a size- and aggregation-dependent feeding interaction between microplastics and rotifers. Microplastics when aggregated with biogenic particles in a natural environment can rapidly change their size-dependent availability. The aggregation properties of microplastics should be taken into account when performing experiments mimicking the natural environment.}, language = {en} } @phdthesis{Hinz2012, author = {Hinz, Justyna}, title = {Factors modifying the aggregation of atrophin-1 acting in cis and in trans}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-60385}, school = {Universit{\"a}t Potsdam}, year = {2012}, abstract = {Ten polyQ (polyglutamine) diseases constitute a group of hereditary, neurodegenerative, lethal disorders, characterized by neuronal loss and motor and cognitive impairments. The only common molecular feature of polyQ disease-associated proteins is the homopolymeric polyglutamine repeat. The pathological expansion of polyQ tract invariably leads to protein misfolding and aggregation, resulting in formation of the fibrillar intraneuronal deposits (aggregates) of the disease protein. The polyQ-related cellular toxicity is currently attributed to early, small, soluble aggregate species (oligomers), whereas end-stage, fibrillar, insoluble aggregates are considered to be benign. In the complex cellular environment aggregation and toxicity of mutant polyQ proteins can be affected by both the sequences of the corresponding disease protein (factors acting in cis) and the cellular environment (factors acting in trans). Additionally, the nucleus has been suggested to be the primary site of toxicity in the polyQ-based neurodegeneration. In this study, the dynamics and structure of nuclear and cytoplasmic inclusions were examined to determine the intrinsic and extrinsic factors influencing the cellular aggregation of atrophin-1, a protein implicated in the pathology of dentatorubral-pallidoluysian atrophy (DRPLA), a polyQ-based disease with complex clinical features. Dynamic imaging, combined with biochemical and biophysical approaches revealed a large heterogeneity in the dynamics of atrophin-1 within the nuclear inclusions compared with the compact and immobile cytoplasmic aggregates. At least two types of inclusions of polyQ-expanded atrophin-1 with different mobility of the molecular species and ability to exchange with the surrounding monomer pool coexist in the nucleus of the model cell system, neuroblastoma N2a cells. Furthermore, our novel cross-seeding approach which allows for monitoring of the architecture of the aggregate core directly in the cell revealed an evolution of the aggregate core of the polyQ-expanded ATN1 from one composed of the sequences flanking the polyQ domain at early aggregation phases to one dominated by the polyQ stretch in the later aggregation phase. Intriguingly, these changes in the aggregate core architecture of nuclear and cytoplasmic inclusions mirrored the changes in the protein dynamics and physico-chemical properties of the aggregates in the aggregation time course. 2D-gel analyses followed by MALDI-TOF MS (matrix-assisted laser desorption/ionization time of flight mass spectrometry) were used to detect alterations in the interaction partners of the pathological ATN1 variant compared to the non-pathological ATN1. Based on these results, we propose that the observed complexity in the dynamics of the nuclear inclusions provides a molecular explanation for the enhanced cellular toxicity of the nuclear aggregates in polyQ-based neurodegeneration.}, language = {en} } @article{SchubertDolfenFrischetal.2012, author = {Schubert, Marcel and Dolfen, Daniel and Frisch, Johannes and Roland, Steffen and Steyrleuthner, Robert and Stiller, Burkhard and Chen, Zhihua and Scherf, Ullrich and Koch, Norbert and Facchetti, Antonio and Neher, Dieter}, title = {Influence of aggregation on the performance of All-Polymer Solar Cells containing Low-Bandgap Naphthalenediimide Copolymers}, series = {dvanced energy materials}, volume = {2}, journal = {dvanced energy materials}, number = {3}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1614-6832}, doi = {10.1002/aenm.201100601}, pages = {369 -- 380}, year = {2012}, abstract = {The authors present efficient all-polymer solar cells comprising two different low-bandgap naphthalenediimide (NDI)-based copolymers as acceptors and regioregular P3HT as the donor. It is shown that these naphthalene copolymers have a strong tendency to preaggregate in specific organic solvents, and that preaggregation can be completely suppressed when using suitable solvents with large and highly polarizable aromatic cores. Organic solar cells prepared from such nonaggregated polymer solutions show dramatically increased power conversion efficiencies of up to 1.4\%, which is mainly due to a large increase of the short circuit current. In addition, optimized solar cells show remarkable high fill factors of up to 70\%. The analysis of the blend absorbance spectra reveals a surprising anticorrelation between the degree of polymer aggregation in the solid P3HT:NDI copolymer blends and their photovoltaic performance. Scanning near-field optical microscopy (SNOM) and atomic force microscopy (AFM) measurements reveal important information on the blend morphology. It is shown that films with high degree of aggregation and low photocurrents exhibit large-scale phase-separation into rather pure donor and acceptor domains. It is proposed that, by suppressing the aggregation of NDI copolymers at the early stage of film formation, the intermixing of the donor and acceptor component is improved, thereby allowing efficient harvesting of photogenerated excitons at the donoracceptor heterojunction.}, language = {en} } @article{TietjenHuth2006, author = {Tietjen, Britta and Huth, Andreas}, title = {Modelling dynamics of managed tropical rainforests - An aggregated approach}, series = {Ecological modelling : international journal on ecological modelling and engineering and systems ecolog}, volume = {199}, journal = {Ecological modelling : international journal on ecological modelling and engineering and systems ecolog}, number = {4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0304-3800}, doi = {10.1016/j.ecolmodel.2005.11.045}, pages = {421 -- 432}, year = {2006}, abstract = {The overuse of rainforests in the last century and its consequences necessitate a rethinking of logging policies. To this end models have been developed to simulate rainforest dynamics and to allow optional management strategies to be evaluated. Parameterisation of presently existing models for a certain site needs a lot of work, thus the parameterisation effort is too high to apply the models to a wide range of rainforests. Hence, in this paper we introduce the simplified model FORREG using the knowledge we have gained from a more complex model, FORMIX3-Q. The FORREG model uses differential equations to determine the volume growth of three successional species groups. Parameterisation is simplified by a genetic algorithm, which determines the required internal model parameters from characteristics of the forest dynamics. The new model is employed to assess the sustainability of various logging policies in terms of yield and damage. Results for three forests are discussed: (1) the tropical lowland rain forest in the Deramakot Forest Reserve, (2) the Lambir National Park in Malaysia and (3) a subtropical forest in Paraguay. Our model reproduces both undisturbed forest dynamics and dynamics of logged forests simulated with FORMIX3-Q very well. However, the resultant volumes of yield and damage differ slightly from those gained by FORMIX3-Q if short logging cycles are simulated. Choosing longer logging cycles leads to a good correspondence of both models. For the Deramakot Forest Reserve different logging cycles are compared and discussed. (c) 2006 Elsevier B.V. All rights reserved.}, language = {en} } @phdthesis{Hechenbichler2021, author = {Hechenbichler, Michelle}, title = {New thermoresponsive amphiphilic block copolymers with unconventional chemical structure and architecture}, doi = {10.25932/publishup-54182}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-541822}, school = {Universit{\"a}t Potsdam}, pages = {XIX, 186}, year = {2021}, abstract = {Das Aggregationsverhalten von amphiphilen Blockcpoolymeren ist wichtig f{\"u}r zahlreiche Anwendungen, beispielsweise in der Waschmittelindustrie als Verdicker oder in der Pharmazie zur kontrollierten Freisetzung von Wirkstoffen. Wenn einer der Bl{\"o}cke thermoresponsiv ist, kann das Aggregationsverhalten zus{\"a}tzlich {\"u}ber die Temperatur gesteuert werden. W{\"a}hrend sich die bisherigen Untersuchungen solcher „intelligenten" Systeme zumeist auf einfache Diblockcopolymere beschr{\"a}nkt haben, wurde in der vorliegenden Arbeit die Komplexit{\"a}t der Polymere und damit die Vielseitigkeit dieser Systeme erh{\"o}ht. Dazu wurden spezifische Monomere, verschiedene Blockl{\"a}ngen, unterschiedliche Architekturen und zus{\"a}tzliche funktionelle Gruppen eingef{\"u}hrt. Durch systematische {\"A}nderungen wurde das Struktur-Wirkungsverhalten solcher thermoresponsiver amphiphiler Blockcopolymere untersucht. Dabei sind die Blockcopolymere typischerweise aus einem permanent hydrophoben „Sticker", einem permanent hydrophilen Block sowie einem thermoresponsiven Block, der ein Lower Critical Solution Temperature (LCST) Verhalten zeigt, aufgebaut. W{\"a}hrend der permanent hydrophile Block aus N,N Dimethylacrylamid (DMAm) bestand, wurden f{\"u}r den thermoresponsiven Block unterschiedliche Monomere, n{\"a}mlich N n Propylacrylamid (NPAm), N iso Propylacrylamid (NiPAm), N,N Diethylacrylamid (DEAm), N,N Bis(2 methoxyethyl)acrylamid (bMOEAm), oder N Acryloylpyrrolidin (NAP) mit entsprechend unterschiedlichen LCSTs von 25, 32, 33, 42 und 56 °C verwendet. Die Blockcopolymere wurden mittels aufeinanderfolgender reversibler Additions-Fragmentierungs-Ketten{\"u}bertragungspolymerisation (RAFT Polymerisation) hergestellt, um Polymere mit linearer, doppelt hydrophober sowie symmetrischer Quasi Miktoarm Architektur zu erhalten. Dabei wurden wohldefinierte Blockgr{\"o}ßen, Endgruppen und enge Molmassenverteilungen (Ɖ ≤ 1.3) erzielt. F{\"u}r komplexere Architekturen, wie die doppelt thermoresponsive und die nicht symmetrische Quasi Miktoarm Architekturen, wurde RAFT mit Atomtransfer-Radikalpolymerisation (ATRP) oder Single Unit Monomer Insertion (SUMI), kombiniert. Die dabei erhaltenen Blockcopolymere hatten ebenfalls wohldefinierte Blockl{\"a}ngen, allerdings war die Molmassenverteilung generell breiter (Ɖ ≤ 1.8) und Endgruppen gingen zum Teil verloren, da komplexere Syntheseschritte n{\"o}tig waren. Das thermoresponsive Verhalten in w{\"a}ssriger L{\"o}sung wurde mittels Tr{\"u}bungspunktmessung und Dynamischer Lichtstreuung (DLS) untersucht. Unterhalb der Phasen{\"u}berganstemperatur waren die Polymere l{\"o}slich in Wasser und mizellare Strukturen waren in der DLS sichtbar. Oberhalb der Phasen{\"u}bergangstemperatur war das Aggregationsverhalten dann stark abh{\"a}ngig von der Architektur und der chemischen Struktur des thermoresponsiven Blocks. Thermoresponsive Bl{\"o}cke aus PNAP und PbMOEAm mit einer Blockl{\"a}nge von DPn = 40 zeigten keinen Tr{\"u}bungspunkt (CP) bis hin zu 80 °C, da durch den angebrachten hydrophilen PDMAm Block die bereits hohe LCST der entsprechenden Homopolymere bei den Blockcopolymeren weiter erh{\"o}ht wurde. Blockcopolymere mit PNiPAm, PDEAm und PNPAm hinggeen zeigten abh{\"a}ngig von der Architektur und Blockgr{\"o}ße unterschiedliche CP's. Oberhalb der CP's waren gr{\"o}ßere Aggregate vor allem f{\"u}r die Blockcopolymere mit PNiPAm und PDEAm sichtbar, wohingegen der Phasen{\"u}bergang f{\"u}r Blockcopolymere mit PNPAm stark abh{\"a}ngig von der jeweiligen Architektur war und entsprechend kleinere oder gr{\"o}ßere Aggregate zeigte. Um das Aggregationsverhalten besser zu verstehen, wurden Fluoreszenzstudien an PDMAm und PNiPAm Homo und Blockcopolymeren mit linearer Architektur durchgef{\"u}hrt, welche mit komplement{\"a}ren Fluoreszenzfarbstoffen an den entgegengesetzten Kettenenden funktionalisiert wurden. Das thermoresponsive Verhalten wurde dabei sowohl in Wasser als auch in {\"O}l-in-Wasser Mikroemulsion untersucht. Die Ergebnisse zeigten, dass das Blockcopolymer sich, {\"a}hnlich wie die anderen hergestellten Architekturen, bei niedrigen Temperaturen wie ein Polymertensid verh{\"a}lt. Dabei bilden die hydrophoben Stickergruppen den Kern und die hydrophilen Arme die Corona der Mizelle. Oberhalb des Phasen{\"u}bergangs des PNiPAm Blocks verhielten sich die Blockcopolymere allerdings wie assoziative Telechele mit zwei nicht symmetrischen hydrophoben Endgruppen, die sich untereinander nicht mischten. Daher bildeten die Blockcopolymere anstatt aggregierter „Blumen"-Mizellen gr{\"o}ßere, dynamische Aggregate. Diese sind einerseits {\"u}ber die urspr{\"u}nglichen Mizellkerne bestehend aus den hydrophoben Sticker als auch {\"u}ber Cluster der kollabierten thermoresponsiven Bl{\"o}cke miteinander verkn{\"u}pft. In Mikroemulsion ist diese Art der Netzwerkbildung noch st{\"a}rker ausgepr{\"a}gt.}, language = {en} } @article{SimonovaIvanovMeleshkoetal.2020, author = {Simonova, Maria and Ivanov, Ivan and Meleshko, Tamara and Kopyshev, Alexey and Santer, Svetlana and Yakimansky, Alexander and Filippov, Alexander}, title = {Self-assembly of molecular brushes with polyimide backbone and amphiphilic block copolymer side chains in selective solvents}, series = {Polymers}, volume = {12}, journal = {Polymers}, number = {12}, publisher = {MDPI}, address = {Basel}, issn = {2073-4360}, doi = {10.3390/polym12122922}, pages = {15}, year = {2020}, abstract = {Three-component molecular brushes with a polyimide backbone and amphiphilic block copolymer side chains with different contents of the "inner" hydrophilic (poly(methacrylic acid)) and "outer" hydrophobic (poly(methyl methacrylate)) blocks were synthesized and characterized by molecular hydrodynamics and optics methods in solutions of chloroform, dimethylformamide, tetrahydrofuran and ethanol. The peculiarity of the studied polymers is the amphiphilic structure of the grafted chains. The molar masses of the molecular brushes were determined by static and dynamic light scattering in chloroform in which polymers form molecularly disperse solutions. Spontaneous self-assembly of macromolecules was detected in dimethylformamide, tetrahydrofuran and ethanol. The aggregates size depended on the thermodynamic quality of the solvent as well as on the macromolecular architectural parameters. In dimethylformamide and tetrahydrofuran, the distribution of hydrodynamic radii of aggregates was bimodal, while in ethanol, it was unimodal. Moreover, in ethanol, an increase in the poly(methyl methacrylate) content caused a decrease in the hydrodynamic radius of aggregates. A significant difference in the nature of the blocks included in the brushes determines the selectivity of the used solvents, since their thermodynamic quality with respect to the blocks is different. The macromolecules of the studied graft copolymers tend to self-organization in selective solvents with formation of a core-shell structure with an insoluble solvophobic core surrounded by the solvophilic shell of side chains.}, language = {en} }