Clarification of the internal deterioration mechanism in polymer solar cells is an important issue for further improvement of not only device durability but also initial device performance. In particular, the charge accumulation at polymerchain ends has been discussed for such an internal deterioration mechanism. However, the direct correlation between polymerchain-end structures and performance deterioration has not yet been investigated from a microscopic viewpoint. Here, we report direct evidence of the internal deterioration mechanism due to the charge accumulation at polymer-chain ends by operando electron spin resonance (ESR) spectroscopy at the molecular level. Using semiconducting polymers with different molecular chain-end structures, that is, poly[(3,4-ethylenedioxythiophene-2,5-diyl)-(9,9-dioctylfluorene-2,7-diyl)] (PEDOTF) with bromine ends (PEDOTF-Br) and that with hydrogen ends (PEDOTF-H), we demonstrate the correlation between the chain-end structures and solar-cell durability, showing a larger amount of charge accumulation and larger performance deterioration for PEDOTF-Brbased solar cells compared to those for PEDOTF-H-based solar cells, owing to the inhabitation of charge transport and the formation of additional potentials in the cells. The origins of observed charge accumulation are precisely clarified with the fitting analyses of operando light-induced ESR spectra and density functional theory calculation, demonstrating that the main internal deterioration is due to the charge accumulation at polymer-chain ends from a microscopic viewpoint. Because such charge accumulation also affects the initial device performance, the optimization of polymer-chain ends will be important for further improvement of not only device durability but also initial device performance for other polymer solar cells.

Although the interface between poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and perovskite layers is one of the key factors to determine the open-circuit voltage of inverted perovskite solar cells, this interface remains poorly understood. We investigated the interface by electron spin resonance spectroscopy and found that the PEDOT undergoes dedoping in contact with the perovskite. The holes in PEDOT were reduced by electron transfer from the perovskite. Additional electron transfer occurred upon light irradiation. The electron transfer would be related to lower open-circuit voltages of the inverted structure compared to those of mesoporous and planar structures.

The deamidation of glutamine (Gln) residues, which occurs non-enzymatically under physiological conditions, triggers protein denaturation and aggregation. Gln residues are deamidated via the cyclic glutarimide intermediates to l-α-, d-α-, l-β-, and d-β-glutamate residues. The production of these biologically uncommon amino acid residues is implicated in the pathogenesis of autoimmune diseases. The reaction rate of Gln deamidation is influenced by the C-terminal adjacent (N +1) residue and is highest in the Gln-glycine (Gly) sequence. Here, we investigated the effect of the (N + 1) Gly on the mechanism of Gln deamidation and the activation barrier using quantum chemical calculations. Energy-minima and transition-state geometries were optimized by the B3LYP density functional theory, and MP2 calculations were used to obtain the single-point energy. The calculated activation barrier (85.4 kJ mol−1) was sufficiently low for the reactions occurring under physiological conditions. Furthermore, the hydrogen bond formation between the catalytic ion and the main chain of Gly on the C-terminal side was suggested to accelerate Gln deamidation by stabilizing the transition state.

<b><i>Background:</i></b> Mast cells play a central role in allergic responses such as food allergy, asthma, allergic rhinitis, and allergic conjunctivitis. Symptoms in the early phase of these allergic diseases are primarily caused by histamine. However, due to the high histidine content in the cytosol and low histamine content in secretory granules, separating and quantifying histamine from histidine is often difficult. <b><i>Objectives:</i></b> We studied a method for rapid and sensitive quantitation of mast cell-derived histamine and evaluated its application to allergic disease research. <b><i>Methods:</i></b> Bone marrow-derived mouse mast cells (BMMCs) were employed in this study. IgE-sensitized BMMCs were activated by FcεRI cross-linking. After activation, both the histamine released to the supernatant and histamine remaining in BMMCs were didansylated and then analyzed by high-performance liquid chromatography with fluorescence detection (HPLC-FD). Didansyl histamine was synthesized as a standard material. <b><i>Results:</i></b> Synthetic didansyl histamine was detected by HPLC-FD with a peak retention time of 18.5 min. Very high linearity of the standard curve was maintained at concentrations of 10 pg/μL or less when the didansyl histamine method was used. This method enables detection of histamine released from 1 × 10⁵ BMMCs. In addition, the histamine concentration in the supernatant due to spontaneous release was also determined. Finally, the ratio of histamine release was highly correlated with the degranulation ratio. <b><i>Conclusion:</i></b> These results indicate that the proposed method using didansylated histamine to determine mast cell-derived histamine is highly useful for allergy research applications.

The ATP-binding cassette subfamily A member 1 (ABCA1) and member 7 (ABCA7) proteins are known to implicate in the membrane lipids trafficking. Previous our studies demonstrated that the differentiation and its process of the bonemarrow cells to mast cells (BMMC) had no difference between the ABCA1 knock-out mice (A1KO), the ABCA7 knockout mice (A7KO) and the wild-type mice (WT). In this study, we investigated the functional difference between A1KO-BMMC, A7KO-BMMC and WT-BMMC.[Method] The bone marrow cells were cultured in RPMI1640 supplemented with 5 ng/mL of IL-3 for 4 weeks or more, and were differentiated into WT-BMMC, A1KO-BMMC and A7KO-BMMC. The surface expression of the high affinity IgE receptor FcRI was evaluated by flow cytometry. The BMMCs were degranulated by FcRI cross-linking, and the degranulation ratio was evaluated by -hexosaminidase assay. As well, the phosphorylation of Syk and Gab2, that are involved in the downstream of FcRI signal transduction pathways, were detected by Western blot analysis. Further, the total cholesterol, the cholesterol ester and the phospholipids contents in BMMCs were measured using commercial kits.[Results and Discussion] There was no difference in the surface expression of FcRI between WT-BMMC, A1KO-BMMC and A7KO-BMMC. After FcRI aggregation, the 50 % decrease of the degranulation ratio was observed in both A1KO-BMMC and A7KO-BMMC, compared with WT-BMMC. Both Syk and Gab2 phosphorylation were observed in A1KO-BMMC and WT-BMMC. Although Syk phosphorylation was observed, Gab2 phosphorylation was not detected in A7KO-BMMC. The contents of cholesterol and cholesterol ester had no difference in WT-BMMC and A7KO-BMMC, although these contents were higher in A1KO-BMMC. It has been known that the conditional deletion of Gab2 causes decline of IgE-dependent degranulation. As well, it has also been reported that the membrane fluidity is changed by cholesterol contents and the degranulation ratio is changed by the alteration of membrane fluidity. These findings and our results suggest that ABCA1 protein may be associated with the alteration of cell-membrane fluidity whereas ABCA7 protein is involved in the mechanisms of Gab2 phosphorylation. And these may potentially be relevant to the decline of mast cell degranulation.