N6- (2- Aminoethyl)adenosine- 3', 5'- cyclic monophosphorothioate, Sp- isomer, immobilized on agarose gel (Sp-6-AE-cAMPS-Agarose)[N6- (2- Aminoethyl)adenosine- 3', 5'- cyclic monophosphorothioate, Sp- isomer, immobilized on agarose gel (Sp-6-AE-cAMPS-Agarose)]