Triplet excimer emission in a series of 4,4'-bis(N-carbazolyl)-2,2'-biphenyl derivatives.

Carbazole-based materials such as 4,4'-bis(N-carbazolyl)-2,2'-biphenyl (CBP) and its derivatives are frequently used as matrix materials for phosphorescent emitters in organic light emitting diodes (OLED)s. An essential requirement for such matrix materials is a high energy of their first triplet excited state. Here we present a detailed spectroscopic investigation supported by density functional theory (DFT) calculations on two series of CBP derivatives, where CH(3) and CF(3) substituents on the 2- and 2'-position of the biphenyl introduce strong torsion into the molecular structure. We find that the resulting poor coupling between the two halves of the molecules leads to an electronic structure similar to that of N-phenyl-3,6-dimethylcarbazole, with a high triplet-state energy of 2.95 eV. However, we also observe a triplet excimer emission centered at about 2.5-2.6 eV in all compounds. We associate this triplet excimer with a sandwich geometry of neighboring carbazole moieties. For compounds with the more polar CF(3) substituents, the lifetime of the intermolecular triplet excited state extends into the millisecond range for neat films at room temperature. We attribute this to an increased charge-transfer character of the intermolecular excited state for the more polar substituents.

Discordance in the effects of interleukin-1 on rat granulosa cell differentiation induced by follicle-stimulating hormone or activators of adenylate cyclase.

Recombinant human interleukin-1 (IL-1) inhibits the follicle-stimulating hormone (FSH)-induced development of luteinizing hormone (LH) receptors and suppresses progesterone secretion in cultured rat granulosa cells. Since activation of adenylate cyclase by FSH is considered to be the primary second messenger system responsible for differentiation of granulosa cells, we examined whether IL-1 could alter the FSH, cholera toxin, or forskolin-induced accumulation of cyclic adenosine 3', 5'-monophosphate (cAMP) from these cells. In addition, we sought to determine if IL-1 could influence differentiation induced by the cAMP analog, 8-bromo cAMP. Cells collected from ovaries of immature, diethylstilbestrol-treated rats were stimulated to differentiate by addition of FSH, cholera toxin, forskolin, or 8-bromo cAMP to the cultures. IL-1 or interleukin-2 (IL-2) was added to some of the tubes, and the primary cultures were incubated for various periods of time. At the end of the culture, the tubes were centrifuged, the medium was saved for progesterone and cAMP radioimmunoassay, and the cells were assayed for specific 125I-human chorionic gonadotropin (hCG) binding to determine the number of LH receptors. In the presence of FSH, IL-1, at a dose as small as 5 ng/ml, but not IL-2, significantly inhibited LH receptor formation and suppressed progesterone secretion in a dose-related manner. IL-1 also significantly suppressed FSH-induced cAMP accumulation after 72 h of incubation but did not appear to do so in a dose-related fashion. In the presence of FSH, IL-1 did not significantly alter the protein content of granulosa cells at the end of culture. During stimulation of granulosa cells with cholera toxin, forskolin, or 8-bromo cAMP, IL-1 significantly reduced LH receptor formation compared to that observed in the absence of IL-1. However, in contrast to IL-1 in the presence of FSH, IL-1 significantly augmented the forskolin-induced secretion of progesterone and accumulation of cAMP after 72 h at subsaturating doses of forskolin. Thus, IL-1 appeared to inhibit forskolin-induced and cholera toxin-induced formation of LH receptors even when cAMP levels were elevated. Similar to forskolin, 8-bromo cAMP-stimulated progesterone secretion was significantly enhanced by IL-1, but LH receptor formation was inhibited. Over a 72-h time course at single doses of FSH or forskolin, IL-1 did not affect cAMP accumulation until 48 h of culture, at which time IL-1 significantly suppressed FSH-induced, but augmented forskolin-induced, accumulation of cAMP.(ABSTRACT TRUNCATED AT 400 WORDS)

Interleukin 1: an inhibitor of luteinizing hormone receptor formation in cultured rat granulosa cells.

We have shown that interleukin 1 (IL 1) suppresses follicle-stimulating hormone (FSH)-induced progesterone secretion and 125I-labeled human chorionic gonadotropin (hCG) binding (a measurement of LH receptors) in cultured rat granulosa cells. The present study was designed to examine if the reduction of FSH-stimulated 125I-labeled hCG binding by IL 1 was caused by a decline in the binding capacity or by an alteration in the affinity of the LH receptor and, further, to determine the minimum period of exposure of the granulosa cells to IL 1 necessary to suppress 125I-labeled hCG binding. IL 1 produced a dose-dependent inhibition of 125I-labeled hCG binding in FSH-stimulated granulosa cells. Scatchard analysis revealed that this effect resulted from a reduction of the binding capacity of the LH receptor with no change in affinity. Also, a minimum of 12-24 h of exposure to IL 1 is necessary to significantly inhibit FSH-induced LH receptor formation. These results suggest that IL 1 decreases the number of LH receptors and that protein synthesis may be necessary for IL 1's action. However, a physiological/pathological role for IL 1 in ovarian regulation has yet to be established.

Interleukin-1 inhibits follicle stimulating hormone-induced differentiation in rat granulosa cells in vitro.

Increasing evidence suggests that factors secreted from cells of the immune system can affect endocrine function. In this report we show that the monokine, interleukin-1, inhibits follicle stimulating hormone-induced development of luteinizing hormone receptors and reduces progesterone secreted from cultured rat granulosa cells. These effects of interleukin-1 were observed in the physiological range of 10(-9) M. The ability of sex steroids to influence the immune response together with our results support the hypothesis that there is a bidirectional communication network which links the immune and reproductive endocrine systems.