A series of 10,10 0 -bis(2-(N-alkylphenothiazine-3-yl)vinyl)-9,9 0 -bianthracene compounds (PVBAn, n ¼ 2, 8, 12 and 16) with different lengths of N-alkyl chains have been designed and synthesized to systematically investigate the effect of chain length on their solid-state fluorescence properties. The results showed that these compounds emitted strong fluorescence in solution and in the solid state. Their emission wavelengths were also strongly affected by solvent polarity, indicating intramolecular charge transfer (ICT) transitions. Interestingly, the fluorescence emission and grinding-induced spectral shifts of PVBAn solids are alkyl length-dependent. PVBA2 shows the smallest fluorescence and absorption spectrum shifts under mechanical force stimuli. Homologues with longer alkyl chains exhibit similar mechanochromic behaviors and larger fluorescence contrasts after grinding. Moreover, the fluorescence emission of ground solid PVBA16 can recover at room temperature, but other compounds need high temperatures for fluorescence to be restored. Differential scanning calorimetry experiments reveal that the cold-crystallization temperature difference is responsible for thermal restoration behaviors. This work demonstrates the feasibility of tuning the solid-state optical properties of fluorescent organic compounds by combining the simple alteration of chemical structure and the physical change of aggregate morphology under external stimuli.

Two L-phenylalanine derivatives with 5,8-bis(2-(carbazol-3-yl)vinyl)quinoxaline (PCQ) and 5,8-bis[2-(carbazol-3-yl)]-2,3-dimethylquinoxaline (DCQ) as fluorophores were synthesized, and their photophysical properties were measured and compared. The two compounds were found to gelate some organic solvents and self-assemble into 1D nanofibers in gels. The wet gel of PCQ emitted a weak orange fluorescence, but the DCQ gel had a strong green one. This result can be due to the presence of two methyl groups and the nonplanar conformation of fluorophore in DCQ. The gel film of DCQ also showed significantly stronger fluorescence than that of PCQ. Thus, the wet gel and xerogel film of DCQ were selected to study their sensing properties to acids. The yellow wet gel of DCQ transformed into a brown sol upon the addition of 0.2 equiv trifluoroacetic acid (TFA), accompanied by emission quenching. The xerogel film of DCQ rapidly responded to volatile acids, such as TFA, HCl, and HOAc. The fluorescence of the xerogel film was gradually quenched with increased concentration of volatile acid vapors. The fibrous film exhibited low detection limits for volatile acid. The detection limits of the thin films for TFA, HCl, and HOAc reached 43, 122, and 950 ppb, respectively.

A hydrogen bonded complex could self-assemble into one-dimensional fibers in its gel phase. The fibrous film could be used as a sensor to detect and discriminate aromatic and aliphatic amines.

Myostatin (MSTN), associated with the “double muscling” phenotype, affects muscle growth and fat deposition in animals, whereas how MSTN affects adipogenesis remains to be discovered. Here we show that MSTN can act through the MEF2C/miR222/SCD5 cascade to regulate fatty acid metabolism. We generated MSTN-knockout (KO) cloned Meishan pigs, which exhibits typical double muscling trait. We then sequenced transcriptome of subcutaneous fat tissues of wild-type (WT) and MSTN-KO pigs, and intersected the differentially expressed mRNAs and miRNAs to predict that stearoyl-CoA desaturase 5 (SCD5) is targeted by miR222. Transcription factor binding prediction showed that myogenic transcription factor 2C (MEF2C) potentially binds to the miR222 promoter. We hypothesized that MSTN-KO upregulates MEF2C and consequently increases the miR222 expression, which in turn targets SCD5 to suppress its translation. Biochemical, molecular and cellular experiments verified the existence of the cascade. This novel molecular pathway sheds light on new targets for genetic improvements in pigs.