Carbon-13 NMR in Conformational Analysis of Nucleic Acid Fragments 2. A Reparametrization of the Karplus Equation for Vicinal NMR Coupling Constants in CCOP and HCOP Fragments

Publisher Website
Google Scholar
Abstract
13C-31P coupling constants of 10 oligoribonucleoside phosphates, measured at a number of temperatures, are presented. The combination of these data with 1H-31 couplings of the same compounds leads to the derivation of two new and mutually consistent sets of Karplus parameters: J(CCOP) = 6.9cos2φ - 3.4cosφ + 0.7 J(HCOP) = 15.3cos2φ - 6. 1cosφ + 1.6 At the same time new values for the base sequence dependent magnitude of the trans conformer of the backbone angle E ∈(C4′-C3′-03′-P) are calculated. The present results show that the magnitude of ∈(t) in right-handed ribo helices is confined to the range 214°-226° (average 219°), which is in much better agreement with single crystal X-ray studies (average 218°) than were previous deductions from NMR spectroscopic results (average 208°).

This publication has 40 references indexed in Scilit: