8- (2- Aminoethylamino)adenosine- 3', 5'- cyclic monophosphorothioate, Sp- isomer, immobilized on agarose gel (Sp-8-AEA-cAMPS-Agarose)[8- (2- Aminoethylamino)adenosine- 3', 5'- cyclic monophosphorothioate, Sp- isomer, immobilized on agarose gel (Sp-8-AEA-cAMPS-Agarose)]