title: Chi 1 angle information from a simple two-dimensional NMR experiment that identifies trans 3JNC gamma couplings in isotopically enriched proteins.
abstract: New quantitative J correlation experiments are used for measuring all two- and three-bond couplings between 15N and aliphatic side-chain carbons in proteins uniformly enriched in 13C and 15N. Results show that 3JNC beta and 2JNC beta invariably are very small. Therefore, a simple and relatively sensitive two-dimensional spin-echo difference experiment can be used to identify residues with a 3JN gamma coupling substantially larger than 1 Hz, indicative of a trans arrangement between N and C gamma. This measurement therefore provides chi 1 angle information for residues with an aliphatic C gamma carbon, and thereby also aids in making stereospecific assignments of H beta resonances. Experiments are demonstrated for ubiquitin and for a complex between calmodulin and a 26-residue peptide.
authors.affiliation: Laboratory of Chemical Physics, National Institutes of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Hu
authors.forename: A
authors.initials: A
authors.lastname: Bax
mesh_terms: D000595:Amino Acid Sequence; D002247:Carbon Isotopes; D006801:Humans; D007553:Isotope Labeling / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008969:Molecular Sequence Data; D009587:Nitrogen Isotopes; D011506:Proteins / Q000737:chemistry*; D014452:Ubiquitins / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D011506:Proteins; D014452:Ubiquitins