Limited proteolysis by a prostatic endopeptidase, the sperm-activating factor initiatorin, regulates the activation of pro-carboxypeptidase B in the seminal fluid of the silkworm, Bombyx mori.

A prostate trypsin-like serine endopeptidase called initiatorin (BmIni) is an essential factor in triggering the sperm maturation response of the silkworm, Bombyx mori. BmIni has been predicted to specifically cleave the carboxyl side of two consecutive arginine residues present in certain seminal plasma and sperm proteins, but the actual substrates are still unknown. In an attempt to elucidate the molecular mechanism underlying the sperm maturation signaling pathway, in this study, we examined whether BmIni activates the seminal carboxypeptidase B (BmCPB) protein through specific degradation. First, we confirmed in vitro that the inactive BmCPB present in unmated male vesicula (v.) seminalis is activated by treatment with BmIni or trypsin. Molecular cloning of the gene encoding the seminal BmCPB protein has shown that BmCPB is produced as a secreted proenzyme and may be activated after a trypsin-like protease cleaves the boundary between the prodomain and the enzyme site. In support of these findings, both trypsin and BmIni significantly activated recombinant Pro-BmCPB, which was successfully expressed and purified as a proenzyme in Escherichia coli; moreover, two specific cleavage forms appeared in the activation by BmIni that did not appear in that by trypsin. Therefore, a recombinant protein with a mutated diarginine motif (Arg109-Arg110), which is presumed to be a pre-cleavage site of BmCPB based on its high homology with bovine CPB, was prepared and treated with BmIni. As a result, the two specific degraded peptides were no longer observed, and simultaneously the activation was suppressed. Taken together, these findings lead to the conclusion that zymogen BmCPB, which is synthesized and secreted in male reproductive organs, is activated by sequence-dependent proteolysis by BmIni during ejaculation and in the female reproductive organs, providing a clue to the mechanism underlying seminal plasma and/or sperm protein degradation by BmIni in the sperm maturation cascade of B. mori.

Electron spin polarization generated by transport of singlet and quintet multiexcitons to spin-correlated triplet pairs during singlet fissions.

Singlet fission (SF) is expected to exceed the Shockley-Queisser theoretical limit of efficiency of organic solar cells. Transport of spin-entanglement in the triplet-triplet pair state via one singlet exciton is a promising phenomenon for several energy conversion applications including quantum information science. However, direct observation of electron spin polarization by transport of entangled spin-states has not been presented. In this study, time-resolved electron paramagnetic resonance has been utilized to observe the transportation of singlet and quintet characters generating correlated triplet-triplet (T + T) exciton-pair states by probing the electron spin polarization (ESP) generated in thin films of 6,13-bis(triisopropylsilylethynyl)pentacene. We have clearly demonstrated that the ESP detected at the resonance field positions of individual triplet excitons is dependent on the morphology and on the detection delay time after laser flash to cause SF. ESP was clearly explained by quantum superposition of singlet-triplet-quintet wavefunctions via picosecond triplet-exciton dissociation as the electron spin polarization transfer from strongly exchange-coupled singlet and quintet TT states to weakly-coupled spin-correlated triplet pair states. Although the coherent superposition of spin eigenstates was not directly detected, the present interpretation of the spin correlation of the separated T + T exciton pair may pave new avenues not only for elucidating the vibronic role in the de-coupling between two excitons but also for scalable quantum information processing using quick T + T dissociation via one-photon excitation.

Scandium-catalyzed carbon-carbon bond-forming reactions of 3-sulfanyl- and 3-selanylpropargyl alcohols.

The scandium-catalyzed substitution reactions of the phenylsulfanyl and phenylselanyl propargyl alcohols 3a- i and 7a- h regioselectively proceeded to give the propargylated compounds 4 and 8 in high yields.