Applications of Variable-angle Sample Spinning Experiments to the Measurement of Scaled Residual Dipolar Couplings and ¹⁵N CSA in Soluble Proteins

Abstract

NMR spectra of ubiquitin in the presence of bicelles at a concentration of 32% w/v have been recorded at 700 MHz under sample spinning conditions at the magic angle (54.7°) and at an angle of 45.5°. At the magic angle, the ¹H–¹⁵N HSQC spectrum of ubiquitin in bicelles is virtually indistinguishable from the one recorded on the protein in solution. Spinning the sample at the magic angle creates an isotropic environment with no preferred bicelle orientations, thus allowing the determination of scalar coupling constants. For an angle of rotation of 45.5°, the bicelles orient with their normal perpendicular to the spinning axis leading to the observation of strong residual dipolar couplings and chemical shift variations of the ¹⁵N resonances.