We would love to go steady with basic and applied studies one at a time, for better understanding the 'complex' biogeochemical processes in biosphere. Currently, we are particularly focusing to the following three challenges:
- Illustration of 'energetic flux' in a single organism, an interaction between organisms (e.g., symbiosis, parasitism, etc.), and a trophic transfer along food webs;
- Illumination of ‘key process’ responsible for the change in the stable isotope ratios (D/H, 13C/12C, 15N/14N, etc.) of organic compounds with respect to organisms’ physiology; and
- Evaluation of ‘universality' based on accurate understanding of 'generality vs. predictable fluctuation' or 'homogeneity vs. heterogeneity’ in the change in the isotope ratios of organic compounds in ecological and geochemical samples.
To do that, we also enjoy the challenges for developing new analytical methods (and new methodologies) of compound- and position-specific isotope analyses of organic compounds in natural samples.
Isotope analysis of organic compounds
During the past three decade, the analysis of stable isotope ratios of individual organic compounds has beed widely used in the study of biogeochemistry. While DNA analysis can visualize the biosphere in terms of species through genetic profiles, isotope analysis can visualize the biosphere in terms of the quantitative flux in physical and/or biochemical processes. The change in the isotope ratios (i.e., isotopic discrimination/fractionation) of organic commpounds are frequently quantified by the kinetic isotope effect and flux of the processes, and the wide array of biochemical reactions within organisms creates diverse and distinctive isotope ratios among organic compounds. The isotope ratios of organic compounds therefore can be useful for characterzing and quantifying any given processes in biosphere.
Key process responsible for the change in the stable isotope ratios
The process driving isotopic discrimination/fractionation during biosynthetic and breakdown pathways in organisms is defined as 'key process'. An identification of 'key process' is therefore indispensable for a fundermental understanding of 'universality' of the isotope ratios found in organisms, as well as for validating the accuracy and precision of the isotope evidence in application studies.