Magic Angle-Oriented Sample Spinning (MAOSS): A New Approach toward Biomembrane Studies

✍ Scribed by Clemens Glaubitz; Anthony Watts

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 281 KB
• Volume: 130
• Category: Article
• ISSN: 1090-7807
• DOI: 10.1006/jmre.1997.1344

✦ Synopsis

The application of magic angle sample spinning (MAS) NMR . The different approaches involve, on the one hand, to uniformly aligned biomembrane samples is demonstrated as static NMR on uniformly aligned samples (2) and, on the a new general approach toward structural studies of membrane other, magic angle sample spinning (MAS) NMR applied proteins, peptides, and lipids. The spectral linewidth from a multito powder-type samples, as recently reviewed by Smith and lamellar lipid dispersion is dominated, in the case of protons, by Groesbeek (3). The clear potential of the first method is in the dipolar coupling. For low-g or dilute spins, however, the chemacquiring molecular orientation as well as structure conical shift anisotropy dominates the spectral linewidth, which is straints. A remarkable resolution can be achieved in cases reduced by the two-dimensional order in a uniformly aligned lipid where the sample is extremely well oriented, as recently membrane. The remaining line broadening, which is due to orienshown for the fd coat protein (4). The second approach tational defects (''mosaic spread'') can be easily removed at low has less requirements toward sample preparation, but allows spinning speeds. This orientational order in the sample also allows the anisotropic intermolecular motions of membrane components rather specific studies such as intermolecular torsion angle (such as rotational diffusion, t c Å 10 010 s) for averaging dipolar and distance measurements or probing of specific interacinteractions to be utilized, e.g., by placing the membrane normal tions (3, 5, 6).

parallel to the rotor axis. The dramatic resolution improvement Specifically in the case of membrane-bound peptides, the for protons which are achieved in a lipid sample at only 220 Hz two central questions to be resolved are the structure in the spinning speed in a 9.4 T field is slightly better than any data membrane and the orientation with respect to the membrane published to date using ultra-high fields (up to 17.6 T) and high-( 2) . The central technical difficulties are to obtain a suffispeed spinning (14 kHz). Additionally, the analysis of spinning ciently high resolution for the nuclei of interest ( 1 H, 13 C, sidebands provides valuable orientational information. We present 15 N) , to utilize dipolar and J couplings for obtaining structhe first 1 H, 31 P, and 13 C MAS spectra of uniformly aligned dimyristural constraints, and to obtain information about the orientoylphosphatidylcholine (DMPC) bilayers. Also, 1 H resolution entation of specific sites in the peptide with respect to the hancement for the aromatic region of the M13 coat protein reconstituted into DMPC bilayers is presented. This new method com-bilayer (7 ).

bines the high resolution usually achieved by MAS with the

Here, the application of MAS to uniformly aligned memadvantages of orientational constraints obtained by working with branes and for obtaining both orientation and structure informacroscopically oriented samples. We describe the general potenmation in one unified approach is demonstrated.

tial and possible perspectives of this technique. ᭧ 1998 Academic Press

In order to explain the approach we start from the MAS Key Words: solid-state NMR; MAS; oriented membranes; peppoint of view and summarize very briefly the theoretical tides, lipids.

foundations. The spin interaction Hamiltonian in spherical tensor notation (spin parameters A kq , lattice parameters T kq ) is given by (8) Contract FMRX-CT96-0004). C. Glaubitz is the recipient of a C. Rhodes Scholarship.