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In Drosophila melanogaster and other insects, the seminal fluid proteins (SFPs) and male sex pheromones that enter the female with sperm during mating are essential for fertility and induce profound post-mating effects on female physiology. The SFPs in D. melanogaster and other taxa include several members of the large gene family known as odorant binding proteins (Obps). Work in Drosophila has shown that some Obp genes are highly expressed in the antennae and can mediate behavioral responses to odorants, potentially by binding and carrying these molecules to odorant receptors. These observations have led to the hypothesis that the seminal Obps might act as molecular carriers for pheromones or other compounds important for male fertility, though functional evidence in any species is lacking. Here, we used functional genetics to test the role of the seven seminal Obps in D. melanogaster fertility and the post-mating response (PMR). We found that Obp56g is required for male fertility and the induction of the PMR, whereas the other six genes are dispensable. We found males lacking Obp56g fail to form a mating plug in the mated female’s reproductive tract, leading to ejaculate loss and reduced sperm storage, likely due to its expression in the male ejaculatory bulb. We also examined the evolutionary history of these seminal Obp genes, as several studies have documented rapid evolution and turnover of SFP genes across taxa. We found extensive lability in gene copy number and evidence of positive selection acting on two genes, Obp22a and Obp51a. Comparative RNAseq data from the male reproductive tract of multipleDrosophilaspecies revealed that Obp56g shows high male reproductive tract expression in a subset of taxa, though conserved head expression across the phylogeny. Together, these functional and expression data suggest that Obp56g may have been co-opted for a reproductive function over evolutionary time. 

Great progress has been made in the past decade in the use of pincer-ligated transition metal complexes for the reduction of dinitrogen. Such complexes, however, have required 'pre-activation' by a strong reducing agent like Na/Hg or KC8 to achieve reductive N2 splitting. In this study, non-innocent pincer molybdenum(III) trihalide complexes, (PhPN5P)MoCl3 and (tBuPPHP)MoBr3, bearing acidic E-H (E = N or P) protons on the ligand periphery, have been utilized to investigate deprotonative N2 splitting. These complexes can be activated in the presence of KOtBu, without the need for a strong reductant. Reaction with KOtBu presumably affords (PhPN5P*)MoCl2 and (tBuPPP)MoBr2 respectively, through the loss of HX across the E-M bond. N2 binding at the vacant coordination site on the metal is followed by splitting of N2 to afford nitrides (PhPN5P*)MoVI(N)Cl2 and (tBuPPP)MoV(N)Br. Previous studies have demonstrated the reduction of molybdenum nitrides to ammonia in the presence of chem. reductants and proton sources but little is known about the relative reactivity of various nitrides and the detailed sequence of events leading to ammonia formation and regeneration of the active species. We, therefore, have begun an investigation of such catalytic cycles for ammonia formation. Mechanistic studies of the new complex (iPrPSP)Mo and of Nishibayashi's (tBuPNpyP)Mo systems, including DFT and electrochemical studies, revealed characteristic roles of the halides in splitting dinitrogen. A new pathway leading to the formation of ammonia and regeneration of the catalyst was elucidated.