Low-bandgap small molecule (SM) donors that can be solution-processed with fullerene acceptors (e.g. PC61/71BM) are proving particularly promising in bulk-heterojunction (BHJ) solar cells. Compared to their π-conjugated polymer counterparts, SM donors are well defined (monodispersed) and more synthetically modular -with relatively wide ranges of bandgaps achievable in stepwise couplings of various donor and acceptor motifs. However, the optimization of SM-fullerene morphologies and BHJ device efficiencies relies more specifically on the use of processing additives, post-processing thermal or solvent vapor annealing (SVA) approaches, and achieving adequate interpenetrating networks and structural order in BHJ thin films can be challenging. In this report, we examine the correlated effects of molecular structure and post-processing SVA on the BHJ solar cell performance of a set of π-extended SM donors composed of dithieno[3,2-b:2',3'-d]pyrrole (DTP) and 5,6-difluorobenzo[c][1,2,5]thiadiazole ([2F]BT) units. In these systems (SM1-3), the introduction of additional alkyl substituents and unsubstituted thiophene rings on the peripheral unit groups critically impacts the effects of SVA steps on BHJ solar cell efficiency. We show that the more π-extended and alkyl-substituted analogue SM3 stands out -with BHJ device efficiencies of ca. 6% obtained from SVA with CS2-while SVA-treated SM3-based active layers also show the most favorable ordering and carrier mobility patterns. However, unlike numbers of SM donors reported in recent years, DTP-[2F]BT SM analogues are in general not prone to dramatic performance variations in BHJ thin films cast with processing additives. Our results indicate that the role of SVA steps is not independent of the molecular structure of the SM donors used in the BHJ solar cells.

Lipid domains favour membrane perturbations induced by Aβ1–42, an amyloid peptide identified as a trigger of Alzheimer's disease. It is proposed that lipid packing defects at domain interfaces could act as adsorption and nucleation sites.

Due to an aging population, neurodegenerative diseases such as Alzheimer's disease (AD) have become a major health issue. In the case of AD, Aβ 1-42 peptides have been identified as one of the markers of the disease with the formation of senile plaques via their aggregation, and could play a role in memory impairment and other tragic syndromes associated with the disease. Many studies have shown that not only the morphology and structure of Aβ 1-42 peptide assembly are playing an important role in the formation of amyloid plaques, but also the interactions between Aβ 1-42 and the cellular membrane are crucial regarding the aggregation processes and toxicity of the amyloid peptides. Despite the increasing amount of information on AD associated amyloids and their toxicity, the molecular mechanisms involved still remain unclear and require in-depth investigation at the local scale to clearly decipher the role of the sequence of the amyloid peptides, of their secondary structures, of their oligomeric states, and of their interactions with lipid membranes. In this original study, through the use of Atomic Force Microscopy (AFM) related-techniques, high-speed AFM and nanoInfrared AFM, we tried to unravel at the nanoscale the link between aggregation state, structure and interaction with membranes in the amyloid/membrane interaction. Using three mutants of Aβ peptides, L34T, oG37C, and WT Aβ 1-42 peptides, with differences in morphology, structure and assembly process, as well as model lipidic membranes whose composition and structure allow interactions with the peptides, our AFM study coupling high spatial and temporal resolution and nanoscale structure information clearly evidences a local correlation between the secondary structure of the peptides, their fibrillization kinetics and their interactions with model membranes. Membrane disruption is associated to small transient oligomeric entities in the early stages of aggregation that strongly interact with the membrane, and present an antiparallel β-sheet secondary structure. The strong effect on membrane integrity that exists when these oligomeric Aβ 1-42 peptides interact with membranes of a particular composition could be a lead for therapeutic studies.

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One of the hallmarks of Alzheimer’s disease (AD) is the formation of neurofibrillary tangles, resulting from the aggregation of the tubulin associated unit protein (Tau), which holds a vital role...

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Misregulation of the signaling axis formed by EphA2 and its ligand, ephrinA1, causes aberrant cell-cell contacts and leads to cellular transformation and malignancy in cancer. However, the activation mechanism of EphA2 is poorly understood. Also, solid tumors exhibit the Warburg effect, which results in an acidic extracellular microenvironment. Taking advantage of this property, we have used a novel approach to design TYPE7 (transmembrane tyrosine kinase peptide for Eph), a membrane peptide that targets EphA2. TYPE7 is pHresponsive, a characteristic which provides solubility at neutral pH, but triggers membrane insertion in acidic conditions. Decreasing the pH leads to increased partitioning and insertion of the peptide into the membrane. TYPE7 has a membrane insertion pH 50 of 6.2 (the pH point for 50% insertion). However, in the presence of the TM/JM domains of EphA2, the pH 50 of TYPE7 increases to 6.9. This effect does not occur in the presence of an unrelated TM domain, indicating specific interaction between TYPE7 and EphA2. Using FRET, we have determined the free energy of dimerization (DG) of the TM/JM domains of EphA2; we assess how the presence of TYPE7 alters this value. The activation of EphA2 by TYPE7 shows important differences compared with activation by a cross-linked version of the ephrinA1 (EA1) ligand. Interestingly, TYPE7 activation does not involve phosphorylation of juxtamembrane residues Y588 and Y594, suggesting a novel mechanism to release juxtamembrane inhibition of the EphA2 kinase domain. Furthermore, while TYPE7 and EA1 inhibit cell migration with similar efficiency, EA1 induces formation of larger EphA2 oligomers than TYPE7. This suggests formation of smaller oligomers might be sufficient to fully activate EphA2. These results shed new light on the activation mechanism of EphA2.

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