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Biologically formed amorphous calcium carbonate
Steve Weiner1, Yael Levi-Kalisman, Sefi Raz
1Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel. steve.weiner@weizmann.ac.il
Connective Tissue Research
|September 4, 2003
Summary
Many organisms produce amorphous calcium carbonate (ACC), a difficult-to-detect biomineral. New research suggests ACC is more widespread and diverse than previously thought, potentially serving as a precursor to crystalline forms.
Area of Science:
- Biomineralization
- Materials Science
- Spectroscopy
Background:
- Organisms across taxa produce amorphous calcium carbonate (ACC), a biomineral known for its instability and solubility.
- The inherent instability and solubility of ACC pose challenges for its detection and characterization.
- ACC is suspected to be more prevalent than currently documented due to these analytical difficulties.
Purpose of the Study:
- To investigate the distribution and structural diversity of biogenic amorphous calcium carbonate (ACC).
- To highlight the utility of specific spectroscopic methods for characterizing ACC.
- To explore the potential roles of ACC in biomineralization processes.
Main Methods:
- Raman spectroscopy for in-situ analysis of wet samples.
- Extended X-ray absorption fine structure (EXAFS) for detailed short-range order analysis.
- Complementary techniques including infrared spectroscopy, TGA/DTA, TEM, and X-ray diffraction were employed.
Main Results:
- EXAFS spectral comparisons revealed distinct short-range order structures among different biogenic ACC phases.
- Raman spectroscopy proved effective for examining ACC in hydrated states.
- The study underscores the challenges in detecting and characterizing amorphous calcium carbonate.
Conclusions:
- Amorphous calcium carbonate (ACC) is likely more widespread in nature than currently recognized.
- Biogenic ACC exhibits structural diversity, with different phases possessing unique short-range order.
- ACC may function as a crucial transient precursor in the formation of crystalline calcium carbonate structures.