Cyclo-dG, cyclo-dA are predominantly induced by the reaction of  radiation-induced DNA damage. Cyclo-purines are formed when a free radical is induced at the C5’ of the deoxyribose sugar by hydroxyl radicals, photolysis or other ionizing processes. The C5’ free radical inserts into the C8-N7 double bond of the adjacent purine residue to form 5’,8-cyclo-purine as either a 5’R or 5’S diastereomer. Of the two diastereomers, the (5’S) cyclo-purine appears to be the most cytotoxic.Cyclo-dA is more prevalent than cyclo-dG in DNA damage. Cyclo-purines have been shown to cause significant distortion of regular DNA helixes and these lesions are repaired not by BER (Base Excision Repair, repair of DNA by removing small non-helix-distorting base lesions)  but by NER (Nucleotide Excision Repair - primary repair of DNA lesions).

In the absence of repair by NER proteins, cyclo-purines accumulate in cells and can block mammalian RNA polymerase II and replicative DNA polymerases.  The distortion in nucleoside structure caused by the C5’-C8 covalent bond perturbs regular hydrogen bonding with the complementary base and has the potential to disrupt normal enzymatic activity in cells. Such DNA lesions may cause polymerase enzymes to be blocked and the efficiency and fidelity of DNA replication may be compromised. The potential for mutations to occur in cells is consequently magnified. cyclo-dA and cyclo-dG lesions are key components in the investigation and research of cellular DNA damage and repair.

Contact Biosynthesis for more information regarding 8-5'(5'S)-Cyclo-2'-deoxyguanosine, Cyclo-dG Oligonucleotide


Product Information


Product Name:

8-5'(5'S)-Cyclo-2'-deoxyguanosine, Cyclo-dG Oligonucleotide

Chemical Name:



DNA damage and repair

Modification Code:



Bio-Synthesis Inc. Oligo Structure



Delivery Format:


Shipping Conditions:

Room Temperature

Storage Conditions:

-20°C To -70°C
Oligonucleotides are stable in solution at 4°C for up to 2 weeks. Properly reconstituted material stored at -20°C should be stable for at least 6 months. Dried DNA (when kept at -20°C) in a nuclease-free environment should be stable for years.


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