Protein Rotational Dynamics in Aligned Lipid Membranes Probed by Anisotropic T1ρ NMR Relaxation  Emmanuel O. Awosanya, Alexander A. Nevzorov  Biophysical Journal  Volume 114, Issue 2, Pages 392-399 (January 2018) DOI: 10.1016/j.bpj.2017.11.3740 Copyright © 2017 Biophysical Society Terms and Conditions

Figure 1 A modified SLF SAMPI4 pulse sequence incorporating a prelock of duration T for measuring individual T1ρ relaxation times for the resolved peaks in the 2D SLF spectrum. Biophysical Journal 2018 114, 392-399DOI: (10.1016/j.bpj.2017.11.3740) Copyright © 2017 Biophysical Society Terms and Conditions

Figure 2 Inhomogeneous 15N CSA linewidths in perpendicular bicelles calculated for an ideal α-helix tilted at 20° with respect to the axis of rotation at various values of the diffusion coefficient as indicated. At the highest value considered, D|| = 5 × 105 s−1, the theoretical rotational contribution to the 15N CSA linewidths is <15 Hz (or ∼0.3 ppm at 1H 500 MHz NMR frequency), which is challenging to assess experimentally. Slower rotational diffusion is manifested by larger anisotropy of linewidths at the perpendicular alignment of the bilayers. Biophysical Journal 2018 114, 392-399DOI: (10.1016/j.bpj.2017.11.3740) Copyright © 2017 Biophysical Society Terms and Conditions

Figure 3 (A) SAMPI4 spectrum of Pf1 coat protein obtained at 500 MHz 1H frequency with assigned NMR peaks for the transmembrane domain used for the fitting of anisotropic T1ρ relaxation times (assignment taken from (52)). (B) Given here are six (6) representative 15N relaxation profiles corresponding to the individual resonances L38, M42, V31, V35, G28, and I26 in the Pf1 SAMPI4 spectra (normalized by the first-point intensity) as a function of spin lock time fitted to single-exponential decays. To see this figure in color, go online. Biophysical Journal 2018 114, 392-399DOI: (10.1016/j.bpj.2017.11.3740) Copyright © 2017 Biophysical Society Terms and Conditions

Figure 4 A correlation plot of R1ρ versus the bond factor sin4 (θB), where θB is the angle that an NH bond makes with the axis of rotation. The rotational diffusion coefficient D|| = 8.0 × 105 s−1 was deduced from linear regression using Eqs. 10 and 12 with the linear regression coefficient R2 = 0.86. Error bars were determined from the exponential fits in the spin-locking experiments (Fig. 3 B; Table 1). Biophysical Journal 2018 114, 392-399DOI: (10.1016/j.bpj.2017.11.3740) Copyright © 2017 Biophysical Society Terms and Conditions

Figure 5 (A) Dipolar waves for the Pf1 coat protein transmembrane domain with the expected periodicity of 3.6, which is indicative of the angular anisotropy of dipolar couplings for an α-helix. (B) R1ρ relaxation profile for the assigned consecutive NMR peaks for the TM region of Pf1. A wavelike behavior of the R1ρ relaxation rates allows one to extract the value of the diffusion coefficient of 7.7 × 106 s−1 when the helix tilt of 22.3° from (A) is used in the fit. The error bars were determined from the exponential fits in the spin-locking experiments (Fig. 3 B; Table 1). Biophysical Journal 2018 114, 392-399DOI: (10.1016/j.bpj.2017.11.3740) Copyright © 2017 Biophysical Society Terms and Conditions