2'- O- (2- Aminoethylcarbamoyl)adenosine- 3', 5'- cyclic monophosphorothioate, Sp- isomer, immobilized on agarose gel (Sp-2'-AEC-cAMPS-Agarose)[2'- O- (2- Aminoethylcarbamoyl)adenosine- 3', 5'- cyclic monophosphorothioate, Sp- isomer, immobilized on agarose gel (Sp-2'-AEC-cAMPS-Agarose)]