A1 Refereed original research article in a scientific journal
Hydrolytic stability of 2 ',3 '-O-methyleneadenos-5 '-yl 2 ',5 '-di-O-methylurid-3 '-yl 5 '-O-methylurid-3 '(2 ')-yl phosphate: implications to feasibility of existence of phosphate-ranched RNA under physiological conditions
Authors: Lonnberg T, Kiiski J, Mikkola S
Publisher: ROYAL SOC CHEMISTRY
Publication year: 2005
Journal: Organic and Biomolecular Chemistry
Journal name in source: ORGANIC & BIOMOLECULAR CHEMISTRY
Journal acronym: ORG BIOMOL CHEM
Volume: 3
Issue: 6
First page : 1089
Last page: 1096
Number of pages: 8
ISSN: 1477-0520
DOI: https://doi.org/10.1039/b500054h
Abstract
Hydrolytic reactions of 2',3'-O-methyleneadenos-5'-yl 2', 5'-di-O-methylurid-3'-yl 5'-O-methylurid-3'(2')-yl phosphate (1a,b) have been followed by RP-HPLC over a wide pH range to evaluate the feasibility of occurrence of phosphate- branched RNA under physiological conditions. At pH < 2, where the decomposition of 1a, b is. rst order in [H3O+], the P-O5' bond is cleaved 1.5 times as rapidly as the P-O3' bond. Under these conditions, the reaction probably proceeds by an attack of the 2'-OH on the phosphotriester monocation. Over a relatively wide range from pH 2 to 5, the hydrolysis is pH-independent, referring to rapid initial deprotonation of the attacking 2'-OH followed by general acid catalyzed departure of the leaving nucleoside. The P-O5' bond is cleaved 3 times as rapidly as the P-O3' bond. At pH 6, the reaction becomes. rst order in [HO-], consistent with an attack of the 2 - oxyanion on neutral phosphate. The product distribution is gradually inversed: in 10 mmol L-1 aqueous sodium hydroxide, cleavage of the P-O3' bond is favored over P-O5' by a factor of 7.3. The results of the present study suggest that the half-life for the cleavage of 1a, b under physiological conditions is only 100 s. Even at pH 2, where 1a, b is most stable, the half-life for its cleavage is less than one hour and the isomerization between 1a and 1b is even more rapid than cleavage. The mechanisms of the partial reactions are discussed.
Hydrolytic reactions of 2',3'-O-methyleneadenos-5'-yl 2', 5'-di-O-methylurid-3'-yl 5'-O-methylurid-3'(2')-yl phosphate (1a,b) have been followed by RP-HPLC over a wide pH range to evaluate the feasibility of occurrence of phosphate- branched RNA under physiological conditions. At pH < 2, where the decomposition of 1a, b is. rst order in [H3O+], the P-O5' bond is cleaved 1.5 times as rapidly as the P-O3' bond. Under these conditions, the reaction probably proceeds by an attack of the 2'-OH on the phosphotriester monocation. Over a relatively wide range from pH 2 to 5, the hydrolysis is pH-independent, referring to rapid initial deprotonation of the attacking 2'-OH followed by general acid catalyzed departure of the leaving nucleoside. The P-O5' bond is cleaved 3 times as rapidly as the P-O3' bond. At pH 6, the reaction becomes. rst order in [HO-], consistent with an attack of the 2 - oxyanion on neutral phosphate. The product distribution is gradually inversed: in 10 mmol L-1 aqueous sodium hydroxide, cleavage of the P-O3' bond is favored over P-O5' by a factor of 7.3. The results of the present study suggest that the half-life for the cleavage of 1a, b under physiological conditions is only 100 s. Even at pH 2, where 1a, b is most stable, the half-life for its cleavage is less than one hour and the isomerization between 1a and 1b is even more rapid than cleavage. The mechanisms of the partial reactions are discussed.
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