We report the design, synthesis, and implemention in semiconducting polymers of a novel head-to-head linkage containing the TRTOR (3-alkyl-3′-alkoxy-2,2′-bithiophene) donor subunit having a single strategically optimized, planarizing noncovalent S•••O interaction. Diverse complementary thermal, optical, electrochemical, X-ray scattering, electrical, photovoltaic, and electron microscopic characterization techniques are applied to establish structure−property correlations in a TRTOR-based polymer series. In comparison to monomers having double S•••O interactions, replacing one alkoxy substituent with a less electron-donating alkyl one yields TRTOR-based polymers with significantly depressed (0.2−0.3 eV) HOMOs. Furthermore, the weaker single S•••O interaction and greater TRTOR steric encumberance enhances materials processability without sacrificing backbone planarity. From another perspective, TRTOR has comparable electronic properties to ring-fused 5Hdithieno[3,2-b:2′,3′-d]pyran (DTP) subunits, but a centrosymmetric geometry which promotes a more compact and ordered structure than bulkier, axisymmetric DTP. Compared to monosubstituted TTOR (3-alkoxy-2,2′-bithiophene), alkylation at the TRTOR bithiophene 3-position enhances conjugation and polymer crystallinity with contracted π−π stacking. Grazing incidence wide-angle X-ray scattering (GIWAXS) data reveal that the greater steric hindrance and the weaker single S•••O interaction are not detrimental to close packing and high crystallinity. As a proof of materials design, copolymerizing TRTOR with phthalimides yields copolymers with promising thin-film transistor mobility as high as 0.42 cm 2 /(V•s) and 6.3% power conversion efficiency in polymer solar cells, the highest of any phthalimide copolymers reported to date. The depressed TRTOR HOMOs imbue these polymers with substantially increased I on /I off ratios and V oc 's versus analogous subunits with multiple electron donating, planarizing alkoxy substituents. Implementing a head-to-head linkage with an alkyl/alkoxy substitution pattern and a single S•••O interaction is a promising strategy for organic electronics materials design.

Altered transforming growth factor-b (TGF-b) signalling has been implicated in tumour development and progression. However, the molecular mechanism behind this alteration is poorly understood. Here we show that profilin-2 (Pfn2) increases Smad2 and Smad3 expression via an epigenetic mechanism, and that profilin-2 and Smad expression correlate with an unfavourable prognosis of lung cancer patients. Profilin-2 overexpression promotes, whereas profilin-2 knockdown drastically reduces, lung cancer growth and metastasis. We show that profilin-2 suppresses the recruitment of HDAC1 to Smad2 and Smad3 promoters by preventing nuclear translocation of HDAC1 through protein-protein interaction at the C terminus of both proteins, leading to the transcriptional activation of Smad2 and Smad3. Increased Smad2 and Smad3 expression enhances TGF-b1-induced EMT and production of the angiogenic factors VEGF and CTGF. These findings reveal a new regulatory mechanism of TGF-b1/Smad signalling, and suggest a potential molecular target for the development of anticancer drugs.

Background-Recently, several new human coronaviruses have been identified.