Impact of nucleic acid self-alignment in a strong magnetic field on the interpretation of indirect spin-spin interactions

0458986 - ÚOCHB 2017 RIV NL eng J - Journal Article
Vavrinská, A. - Zelinka, J. - Šebera, Jakub - Sychrovský, Vladimír - Fiala, R. - Boelens, R. - Sklenář, V. - Trantírek, L.
Impact of nucleic acid self-alignment in a strong magnetic field on the interpretation of indirect spin-spin interactions.
Journal of Biomolecular NMR. Roč. 64, č. 1 (2016), s. 53-62. ISSN 0925-2738. E-ISSN 1573-5001
R&D Projects: GA ČR GA13-27676S
Grant - others:AV ČR(CZ) M200551205
Institutional support: RVO:61388963
Keywords : NMR * DFT calculations * spin-spin interactions * magnetic field
Subject RIV: CF - Physical ; Theoretical Chemistry
Impact factor: 2.410, year: 2016
http://link.springer.com/article/10.1007/s10858-015-0005-x

Heteronuclear and homonuclear direct (D) and indirect (J) spin-spin interactions are important sources of structural information about nucleic acids (NAs). The Hamiltonians for the D and J interactions have the same functional form; thus, the experimentally measured apparent spin-spin coupling constant corresponds to a sum of J and D. In biomolecular NMR studies, it is commonly presumed that the dipolar contributions to Js are effectively canceled due to random molecular tumbling. However, in strong magnetic fields, such as those employed for NMR analysis, the tumbling of NA fragments is anisotropic because the inherent magnetic susceptibility of NAs causes an interaction with the external magnetic field. This motional anisotropy is responsible for non-zero D contributions to Js. Here, we calculated the field-induced D contributions to 33 structurally relevant scalar coupling constants as a function of magnetic field strength, temperature and NA fragment size. We identified two classes of Js, namely (1)J(CH) and (3)J(HH) couplings, whose quantitative interpretation is notably biased by NA motional anisotropy. For these couplings, the magnetic field-induced dipolar contributions were found to exceed the typical experimental error in J-coupling determinations by a factor of two or more and to produce considerable over-or underestimations of the J coupling-related torsion angles, especially at magnetic field strengths >12 T and for NA fragments longer than 12 bp. We show that if the non-zero D contributions to J are not properly accounted for, they might cause structural artifacts/bias in NA studies that use solution NMR spectroscopy.
Permanent Link: http://hdl.handle.net/11104/0259189