Element speciation analysis
Elements exist in various chemical forms(chemical species), e.g. a complex
with organic compounds, in biological and environmental system. The chemical
form determines essentiality, toxicity or bioavailability of an element.
Thus, "element speciation analysis" that identifies and quantifies the chemical form of an element, as well as total element determination, is necessary to clarify the behavior and function of an element in the biological and environmental system.
For element speciation analysis, I have used mainly the following two analytical
1. HPLC/ICP-MS(high performance liquid chromatography / inductively coupled
2. NMR(nuclear magnetic resonance spectrometry)
The figure shows size exclusion HPLC/ICP-MS chromatograms of rhamnogalacturonan
II-borate complex(dRG-II-B), which is isolated from an enzyme digest of
plant cell walls. In the dRG-II-B, a borate cross-links two RG-II molecules
by ester bonds. In the chromatograms, Ca, Sr, Ba, Pb peaks appear in the
same retention time with the B peak of dRG-II-B, indicating that these
metals are bound to dRG-II-B.
Plant nutritional biochemistry
Plants need only inorganic elements (minerals) as essential nutrients for
their growth and development. The essential elements needed in relatively
large and small amounts are referred to as macronutrients and micronutrients,
respectively. The elements recognized today as a macronutrient are N, P,
K , S, Ca, and Mg, and those as a micronutrient are Fe, Mn, Cu, Zn, Ni,
Mo, B, and Cl. In contrast, the essential nutrients for animals are organic
compounds such as carbohydrates, proteins, lipids, vitamins as well as
Inorganic elements occur in various chemical forms in a living body. The
movement (ca. absorption, transport) and function (ca. essentiality, toxicity)
of the minerals depends on their chemical forms. Therefore, to clarify
the chemical form of essential elements in plants are necessary to understanding
their movement and function in plants.
The figure is a model showing that boron(B), one of essential micronutrients
for vascular plants, binds two rhamnogalacturonan II(RG-II), and cross-links
pectin molecules in plant cell walls. B is thought to contribute to the
stabilization of cell wall structure by the pectin network. Metal ions
such as Ca, Sr, Ba and Pb are bound to dRG-II-B complex as mentioned above.
The metal binding is speculated to relate with structural stabilization
of the complex.