title: Effect of 5-alkyl substitution of uracil on the thermal stability of poly [d(A-r5U)] copolymers.
abstract: The thermal transition of poly[d(A-r5U)] polydeoxynucleotides (where r was a hydrogen atom, or a methyl, ethyl, n-propyl, n-butyl or n-pentyl group) was studied by measuring the derivative melting profiles of the polymers in the range of 0.01--0.36 M K+, at pH 6.8. According to the Tm values, polydeoxynucleotide analogues show lower thermal stability than poly[d(A-T)] at any counterion concentration applied. At a given salt concentration, Tm of the alkyl analogues decreased as the number of carbon atoms (n) in the r substituent of poly[d(A-r5U)] increased. 1/Tm plotted against against 1/n yielded a linear relationship. Cooperativity of the melting of all poly[d(A--U)] analogues decreased with the increase of salt concentration in the solution. This change depended again on 5-substitution of the uracil moiety of poly[d(A-U)]. Smallest decrease was observed in the case of poly[d(A--U)] whereas largest decrease was shown by poly[d(A-pe5U)] (pe=pentyl group).
mesh_terms: D000478:Alkylation; D004355:Drug Stability; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D011063:Poly A-U; D011089:Polydeoxyribonucleotides; D013329:Structure-Activity Relationship; D013696:Temperature; D014498:Uracil / Q000031:analogs & derivatives*
chemical_list: D011089:Polydeoxyribonucleotides; D011063:Poly A-U; D014498:Uracil