Quantum chemical modeling of through-hydrogen bond spin-spin coupling in amides and ubiquitin

Authors
Citation
A. Bagno, Quantum chemical modeling of through-hydrogen bond spin-spin coupling in amides and ubiquitin, CHEM-EUR J, 6(16), 2000, pp. 2925-2930
Citations number
24
Categorie Soggetti
Chemistry
Journal title
CHEMISTRY-A EUROPEAN JOURNAL
ISSN journal
09476539 → ACNP
Volume
6
Issue
16
Year of publication
2000
Pages
2925 - 2930
Database
ISI
SICI code
0947-6539(20000818)6:16<2925:QCMOTB>2.0.ZU;2-P
Abstract
Through-hydrogen bond spin-spin coupling has been investigated computationa lly in the formamide dimer and in fragments of the protein ubiquitin. The F ermi-contact term was calculated by finite perturbation theory with the B3L YP DFT method with several basis sets. The distance and angular dependence of the (3)J(N,C) coupling constant (N-H ... O=C) in the hydrogen-bonded for mamide dimer was firstly examined for a wide range of mutual arrangements, also in relation to the stability of the dimer. The magnitude of (3)J(N,C) is relatively insensitive to the dihedral angle between the two amide plane s. whereas values between 1-2 Hz are calculated for a variety of arrangemen ts, including non-linear hydrogen bonds, in agreement with the shape of som e occupied, low-lying molecular orbitals which connect donor and acceptor. Then, fragments of the ubiquitin protein (for which such coupling constants are experimentally available) were generated by removing from the experime ntal structure all amino acids except those involved in hydrogen bonding, a nd coupling constants were calculated for such fragments. Although calculat ed (3)J(N,C) values are sometimes overestimated, they generally correlate w ith the corresponding experimental values.