Analysis of the proteinaceous components of the organic matrix of calcitic sclerites from the soft coral Sinularia sp.

An organic matrix consisting of a protein-polysaccharide complex is generally accepted as an important medium for the calcification process. While the role this "calcified organic matrix" plays in the calcification process has long been appreciated, the complex mixture of proteins that is induced and assembled during the mineral phase of calcification remains uncharacterized in many organisms. Thus, we investigated organic matrices from the calcitic sclerites of a soft coral, Sinularia sp., and used a proteomic approach to identify the functional matrix proteins that might be involved in the biocalcification process. We purified eight organic matrix proteins and performed in-gel digestion using trypsin. The tryptic peptides were separated by nano-liquid chromatography (nano-LC) and analyzed by tandem mass spectrometry (MS/MS) using a matrix-assisted laser desorption/ionization (MALDI) - time-of-flight-time-of-flight (TOF-TOF) mass spectrometer. Periodic acid Schiff staining of an SDS-PAGE gel indicated that four proteins were glycosylated. We identified several proteins, including a form of actin, from which we identified a total of 183 potential peptides. Our findings suggest that many of those peptides may contribute to biocalcification in soft corals

Aspartic acid-rich proteins: the organic matrix of calcitic sclerites from the alcyonarian, Sinularia polydactyla

琉球大学21世紀プログラム「サンゴ礁島嶼系の生物多様性の総合解析」平成18年度成果発表会（平成19年3月10日開催）　招待講演会会場：琉球大学50周年記念館1F，ポスター発表会場：琉球大学大学会館3

Isotopic variation of molecular hydrogen in 20°–375°C hydrothermal fluids as detected by a new analytical method

[1] Molecular hydrogen (H2) is one of the most important energy sources for subseafloor chemolithoautotrophic microbial ecosystems in the deep-sea hydrothermal environments. This study investigated stable isotope ratios of H2 in 20°–375°C hydrothermal fluids to evaluate usefulness of the isotope ratio as a tracer to explore the H2-metabolisms. Prior to the observation, we developed an improved analytical method for the determination of concentration and stable isotope ratio of H2. This method achieved a relatively high sensitivity with a detection limit of 1 nmol H2 within an analytical error of 10‰ in the δDH2 value. The δDH2 values in the high-temperature fluids were between −405‰ and −330‰, indicating the achievement of the hydrogen isotopic equilibrium between H2 and H2O at around the hydrothermal end-member temperature. In contrast, several low-temperature fluids showed apparently smaller δDH2 values than those in the high-temperature fluids in spite of a negligible δDH2 change due to fluid-seawater mixing, suggesting the possibility of δDH2 change in the low-temperature fluids and the surrounding environments. Since the δDH2 change in low-temperature environments is not well explained by the very sluggish abiotic thermal isotopic equilibrium between H2 and H2O, it could be associated with (micro)biological H2-consuming and/or H2-generating metabolisms that would strongly promote the isotopic equilibrium at low temperatures. Our first detection of the δDH2 variation in deep-sea hydrothermal systems presents the availability of the δDH2 value as a new tracer for microbes whose enzymes catalyze D/H exchange in H2