The 6-thioguanine/5-methyl-2-pyrimidinone base pair.
As part of a program to determine the physical possibility of expanding the number of types of base pairs in DNA, the pairing stabilities of the analog bases 6-thioguanine (GS) and 5-methyl-2-pyrimidinone (TH) in oligodeoxynucleotides were measured. Procedures were developed to synthesize oligodeoxynucleotides with the analog bases. The sequences of the synthesized oligomers were T-C-G-A-C-G-G-X-Y-C-C-G. An enzymatic procedure was developed to measure relative association constants of oligomer pairs with the self complementary reference oligomer, X = A and Y = T, K(T/A) = K. The results were K(C/G) = (5 +/- .5)K, K(TH/GS) = K/(1 +/- .5), K(T/G) = K/(9 +/- 3), K(TH/G) = K/(25 +/- 5), K(C/GS) less than K/30, K(TH/A) less than K/40, K(T/GS) less than K/40, K(C/A) less than K/40. The results with the standard bases are consistent with other methods of measurement. The stability of the base pair GS/TH is approximately the same as the standard base pair A/T.
Rappaport
H P
HP
Biology Department, Temple University, Philadelphia, PA 19122.
D006860:Hydrogen Bonding; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis; D011744:Pyrimidinones; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D013866:Thioguanine
D009838:Oligodeoxyribonucleotides; D011744:Pyrimidinones; C056905:5-methyl-2-pyrimidinone; D013866:Thioguanine