Date: 16:00 – 18:00, Friday, October 22, 2021
Speaker: Wataru Takahagi
Title: Geoelectrochemical ammonia adsorption on nano-crystalline mackinawite in early ocean alkaline hydrothermal systems
講演者：高萩航
Estimating where and how the building blocks of life were supplied before the emergence of life is a challenge for origin-of-life studies. Nitrogen is an essential substance that makes up life and is found in nitrogen-containing biomolecules such as amino acids and nucleobases. The emergence of life required highly concentrated reactive nitrogen (e.g., NH3, NO3–) as a starting material to synthesize organic molecules and build up the life structure. Summers and Chang estimated steady-state ammonia concentration in the primitive ocean range in 3.6-70 µM, which is significantly higher than the value in the present ocean (< 1 µM); However, it is much lower than those used in abiotic synthesis experiments of biomolecules. Thus, a sufficient supply of ammonia was necessary for the emergence of life, but no such mechanism has been reported. Here we propose that nanocrystalline mackinawite (FeSnano) could have played a role in the storage and release of ammonia depending on the electrochemical potential of the hydrothermal vent surface. Due to spontaneous geoelectrochemical reduction around the hydrothermal vents, some FeSnano seems to be negatively charged and electrostatically adsorbed with ammonium. It was found that FeSnano can retain about 170 times more ammonia per unit mass than seawater under applying –0.8 VSHE. These reductive-phase sulfide minerals produced by electro-reduction in early hydrothermal vents are an example of localized reductive mineral evolution; therefore, resulting in minerals act as reservoirs of the building blocks of life.
Speaker: Hui Hsin Khoo
Title: Development of hyphenated imaging of elemental and molecular substances using LA-ICP-MS/DBDI-MS
Biological functions of metal-containing compounds typically depend on the element itself and the location of the compound in a biological system (Yu et al., 2009; Sodhi & Paul, 2019). Information on these compounds allow us to understand the function of metal to the molecule, as well as the interaction and effect of the targeted metal-containing compounds on the surrounding substances. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a routine analytical method for elemental imaging due to high spatial resolution (5 – 200 μm) and high ionisation efficiency of most elements. This technique. However, ICP has a high excitation temperature (6,000–10,000 K), causing molecular substances to be atomised within the ion source. Matrix-assisted laser desorption/ionisation (MALDI)-MS can be a complementary technique for the identification of molecular species. Bianga et al. reported using LA-ICP-MS and MALDI-MS for elemental and molecular imaging of Pt-metallodrugs in tumours. However, this approach involves analysis on different sample slices. To overcome the above limitation, we have developed a plasma ion source (dielectric barrier discharge ionisation: DBDI) designed exclusively for molecular analysis to complement LA-ICP-MS, as well as aiming to develop an analytical method to obtain distribution information simultaneously from the same sample. A UV femtosecond laser system (Jupiter Solid Nebulizer, ST Japan), for solid sampling, was hyphenated in parallel with both an elemental and molecular mass spectrometer via split stream. Elemental analysis was performed using a quadrupole ICP-MS (iCAP TQ, Thermo Fisher Scientific), whereas the DBDI ion source coupled to a mass spectrometer (Qtrap 5500, AB Sciex) was used for molecular analysis. This presentation will give details on instrumentation and preliminary results obtained by the system.