Carboxy radicals, crosslinking

These data demonstrate that in the reaction of the peptide, and the protein as well, crosslinking reactions lead to a strongly restricted rotation of the pyrazinium radical and to an immobilization of the radical, thus inhibiting die resolution of the EPR signal. We therefore proposed the broad singlet to represent protein-bound l,4-bis-(5-amino-5-carboxy-l-pentyl) pyrazinium... 

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