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Highly ordered thin films of pseudorotaxane consisting of the host cyclic molecule, dibenzo[24]crown-8 (DB24C8), and the guest axle molecule, N-(xylylammonium)-methylferrocene, were prepared on solid substrates via solution casting followed by annealing. Collective evidence obtained from X-ray diffraction, differential scanning calorimetry, polarised optical microscopy (POM) and grazing incident wide-angle X-ray scattering (GIWAXS) experiments indicates that the specially architectured host and guest molecules can first form a highly ordered crystalline phase upon solvent evaporation. Annealing of this phase at temperatures above 130 °C leads to an irreversible transition of the crystal phase to a high-temperature (HT) crystalline phase with triclinic crystalline domain sizes of 50–100 μm. When cooled back to room temperature, the HT phase undergoes a solid–solid phase transition to a low-temperature (LT) crystalline phase of a similar triclinic form but favouring a tighter packing of axle molecules. Thermally reversible LT–HT phase transitions were consistently evidenced via in situ observations by POM and X-ray scattering and are attributed to a subtle ordering competition between the host cyclic molecules and guest axle molecules. This local structural transition, however, only slightly affects the stability of the layering frame structure of the pseudorotaxane film, in which the supermolecular complex adopts an edge-on orientation with the cyclic molecular plane being perpendicular to the substrate and is interlocked via interactions with the axle molecules. The results demonstrate the feasibility of self-assembled pseudorotaxane films with thermally driven phase transitions as a possible molecular switch. [ABSTRACT FROM AUTHOR]

A thermally crosslinkable poly(cyclopentadithiophene-alt-benzothiadiazole) (PCPDTBT) analogue copolymer with 2-ethylhexyl group and 5-hexenyl group on 4,4-positions of cyclopentadithiophene has been synthesised by palladium catalyzed Suzuki coupling reaction. Space-Charge Limited Current (SCLC) devices show hole mobility of up to 3 × 10−4 cm2 V−1 s−1. In addition, organic photovoltaics (OPVs) were fabricated using fullerene derivatives as acceptor materials. The best performing device exhibited Power Conversion Efficiency (PCE) at 2.0%, which could be improved to 3.7% after inclusion of dithiol additives. Most significantly, the lifetime of the OPV was enhanced by the crosslinking; when light soaked at 1 sun of irradiance, a half-life, t1/2 = 419 hours was measured, which is 51% improvement over an OPV using standard PCPDTBT. This higher stability is accounted for the crosslinkable structure of the polymer after annealing. The crosslinking reaction was confirmed by solubility tests, Fourier transform infrared spectroscopy and morphological analysis conducted by Atomic Force Microscopy and simultaneous synchrotron grazing-incidence small-/wide-angle X-ray scattering. [ABSTRACT FROM AUTHOR]

Our previous genome-wide association studies showed that DNA methyltransferase 1 (DNMT1) is associated with increased susceptibility to type 2 diabetes (T2D) in Han Chinese individuals. Here, we aimed to further evaluate the role of DNMT1 in T2D. We performed a genome-wide DNA methylation array and found that the nuclear receptor subfamily 4 group A member 1 (NR4A1) promoter was hypermethylated in patients with T2D and in a mouse model of T2D. Moreover, DNA hypermethylation of the NR4A1 promoter reduced NR4A1 mRNA expression. Transient transfection of human NR4A1 into RIN-m5F and 293T cells caused DNMT1 inhibition and induced insulin receptor activation. NR4A1knockdown by shRNA resulted in overexpression of DNMT1 and inhibition of insulin receptor, suggesting that the NR4A1 gene is involved in the epigenetics pathway. Furthermore, T2D model mice treated with the DNMT1 inhibitor aurintricarboxylic acid (ATA) showed reduced activation of DNMT1 in pancreatic β cells; this effect reversed the changes in NR4A1 expression and decreased blood glucose in T2D model mice. Thus, our results showed for the first time that DNMT1 caused NR4A1 DNA hypermethylation and blocked insulin signaling in patients with T2D. Importantly, ATA therapy may be useful for decreasing blood glucose levels by reversing NR4A1-dependent insulin signaling. These findings improve our understanding of the crucial roles of these regulatory elements in human T2D., Competing Interests: The authors declare that they have no competing interests associated with this article.