2'- O- (2- Aminoethylcarbamoyl)guanosine- 3', 5'- cyclic monophosphate, immobilized on agarose gel (2'-AEC-cGMP-Agarose)[2'- O- (2- Aminoethylcarbamoyl)guanosine- 3', 5'- cyclic monophosphate, immobilized on agarose gel (2'-AEC-cGMP-Agarose)]