Single-polyp metabolomics for coral health assessment.

Coral reef ecosystems supported by environmentally sensitive reef-building corals face serious threats from human activities. Our understanding of these reef threats is hampered by the lack of sufficiently sensitive coral environmental impact assessment systems. In this study, we established a platform for metabolomic analysis at the single-coral-polyp level using state-of-the-art mass spectrometry (probe electrospray ionization/tandem mass spectrometry; PESI/MS/MS) capable of fine-scale analysis. We analyzed the impact of the organic UV filter, benzophenone (BP), which has a negative impact on corals. We also analyzed ammonium and nitrate samples, which affect the environmental sensitivity of coral-zooxanthella (Symbiodiniaceae) holobionts, to provide new insights into coral biology with a focus on metabolites. The method established in this study breaks new ground by combining PESI/MS/MS with a technique for coral polyps that can control the presence or absence of zooxanthellae in corals, enabling functions of zooxanthellae to be assessed on a polyp-by-polyp basis for the first time. This system will clarify biological mechanisms of corals and will become an important model system for environmental impact assessment using marine organisms.

Development of New D,L-Methionine-based Gelators.

D,L-Methionine was chosen as a starting material for the preparation of a new gelator N-10-undecenoyl-D,L-methionylaminooctadecane (DL-Met-R18). Three oligo (dimethylsiloxane)-containing gelators, DL-Met-R18/Si3, DL-Met-R18/Si7-8, and DL-Met-R18/Si14-15, were also prepared from DL-Met-R18 by hydrosilylation reactions. Their gelation abilities were evaluated on the basis of the minimum gel concentration using nine solvents. Compound DL-Met-R18 was able to gelate liquid paraffin and silicone oil, but it crystallized in most solvents. However, DL-Met-R18/Si7-8 resulted to be the best gelator, gelling eight solvents at low concentrations. The results of gelation tests demonstrated that the ability to form stable gels decreases in the following order: DL-Met-R18/Si7-8 ≈ DL-Met-R18/Si14-15 > DL-Met-R18/Si3 >> DL-Met-R18. The aspects and thermal stabilities of the gels were investigated using three-component mixtures of solvents composed of hexadecyl 2-ethylhexanoate, liquid paraffin, and decamethylcyclopentasiloxane (66 combinations). DL-Met-R18/Si3, DL-Met-R18/Si7-8, and DL-Met-R18/Si14-15 could form gels with all these mixed solvent combinations; particularly, DL-Met-R18/Si7-8 gave rise to transparent or translucent gels. FT-IR spectra suggested that the formation of hydrogen bonds between the NH and C=O groups of the amides is one of driving forces involved in the gelation process. Aggregates comprising three-dimensional networks were studied by transmission electron microscopy. Moreover, the viscoelastic behavior of the gels was investigated by rheology measurements.