Electron Spin Resonance of Organic Radicals Derived from Amino Acids in Calcified Fossils

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Abstract
The electron spin resonance of calcified fossils of coral, mollusk shells and bone has revealed that the quintet spectrum which was assigned to alanine radicals actually consists of 7 equally spaced hyperfine lines with isotropic spin-Hamiltonian parameters of g=2.0039 and A=2.17 mT. X-ray irradiation and subsequent heating of CaCO3 doped with L-valine yield the same septet. The septet detected in the fossils and the L-valine-doped CaCO3 is attributable to (CH3)2Ċ-radicals. Only irradiation produces nonparamagnetic precursors which alter to the radicals by postheating. A detailed model of the radical and its formation process are discussed. Multiline spectra arising in L-alanine-doped and glycinedoped CaCO3 are unlike those in irradiated L-alanine and glycine reagents. Models are proposed for the centers in the L-alanine-doped and glycine-doped CaCO3.