川口 眞理

In a ground-breaking recent study, we unveiled the remarkable cellular uptake of 60 nm ZnO and TiO2 nanoparticles by NIH/3T3 mouse skin fibroblasts under microwave irradiation. Even more stimulating is our current demonstration of the potent ability of Ag nanoparticles (147 nm) and Au nanoparticles (120 nm) to stifle the growth of Escherichia coli (E. coli—a prokaryote whose cells lack a membrane-bound nucleus and other membrane-bound organelles), vastly smaller than the NIH/3T3 cells, when exposed to significantly optimized low-power microwave irradiation conditions. Our rigorous assessment of the method’s effectiveness involved scrutinizing the growth rate of E. coli bacteria under diverse conditions involving silver and gold nanoparticles. This indisputably underscores the potential of microwave–nanoparticle interactions in impeding bacterial proliferation. Furthermore, our noteworthy findings on the uptake of fluorescent organosilica nanoparticles by E. coli cells following brief, repeated microwave irradiation highlight the bacteria’s remarkable ability to assimilate extraneous substances.

Abstract During the fertilization of fish eggs, the hardening of the egg envelope is mediated by transglutaminase (hTGase). After fertilization, TGase undergoes processing. We isolated hTGase from extracts of unfertilized and water-activated rainbow trout eggs. Rainbow trout hTGase (Rt-hTGase) appeared as an 80 kDa protein, and its processed form was 55 kDa. Their N-terminal amino acid sequences were nearly identical, suggesting processing in the C-terminal region. The specific activities were not significantly different, indicating that C-terminal processing does not activate the enzyme itself. We cloned the cDNA by reverse transcription polymerase chain reaction (RT-PCR) using degenerate primers followed by RACE-PCR. The deduced amino acid sequence of the cDNA was similar to that of factor XIII subunit A (FXIIIA). Molecular phylogenetic and gene syntenic analyses clearly showed that hTGase was produced by duplication of FXIIIA during the evolution to Teleostei. The 55 kDa processed form of Rt-hTGase is predominantly composed of an enzyme domain predicted from the amino acid sequence of the cDNA. It is hypothesized that the C-terminal domain of Rt-hTGase binds to egg envelope proteins, and that processing allows the enzyme to move freely within the egg envelope, increasing substrate–enzyme interaction and thereby accelerating hardening.