Billeter, MartinNeri, DarioOtting, GottfriedQian, Yan QiuWüthrich, Kurt2026-03-232026-03-230925-2738PubMed:1392569ORCID:/0000-0002-0563-0146/work/209074906https://hdl.handle.net/1885/733807636Improved experimental schemes for the recently introduced J-modulated [15N,1H]-correlation experiment for measurements of the homonuclear amide proton-Cα proton vicinal coupling constants.3JHNα, in uniformly15N-labeled proteins are described, and a nonlinear fit procedure is presented for quantitative evaluation of3JHNα. The method was first tested with the N-terminal DNA-binding domain of the 434 repressor (M=7.3 kDa), where at 13 C precise values of3JHNα in the range 2.0-9.5 Hz were obtained for all residues with resolved15N-1H cross peaks. It was then applied to the Antennapedia homeodomain complexed to a synthetic 14-base pair DNA fragment (molecular weight of the complex ∼ 18 kDa). The3JHNα values measured were found to be in excellent agreement with those predicted from the secondary structure of this protein in the complex.18enJ-modulated [N,H]-COSYNMR structure of proteinsNonlinear fit of J-modulationProtein conformationVicinal spin-spin coupling constants199210.1007/BF018753200026861304