@article{marek_tang_milikisiyants_nevzorov_smirnov_2015, title={Nanotube Array Method for Studying Lipid-Induced Conformational Changes of a Membrane Protein by Solid-State NMR}, volume={108}, ISSN={["1542-0086"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84921058848&partnerID=MN8TOARS}, DOI={10.1016/j.bpj.2014.11.011}, abstractNote={Anodic aluminum oxide substrates with macroscopically aligned homogeneous nanopores of 80 nm in diameter enable two-dimensional, solid-state nuclear magnetic resonance studies of lipid-induced conformational changes of uniformly (15)N-labeled Pf1 coat protein in native-like bilayers. The Pf1 helix tilt angles in bilayers composed of two different lipids are not entirely governed by the membrane thickness but could be rationalized by hydrophobic interactions of lysines at the bilayer interface. The anodic aluminum oxide alignment method is applicable to a broader repertoire of lipids versus bicelle bilayer mimetics currently employed in solid-state nuclear magnetic resonance of oriented samples, thus allowing for elucidation of the role played by lipids in shaping membrane proteins.}, number={1}, journal={BIOPHYSICAL JOURNAL}, publisher={Elsevier BV}, author={Marek, Antonin and Tang, Wenxing and Milikisiyants, Sergey and Nevzorov, Alexander A. and Smirnov, Alex I.}, year={2015}, month={Jan}, pages={5–9} }
 @article{tang_knox_nevzorov_2012, title={A spectroscopic assignment technique for membrane proteins reconstituted in magnetically aligned bicelles}, volume={54}, ISSN={["0925-2738"]}, DOI={10.1007/s10858-012-9673-y}, abstractNote={Oriented-sample NMR (OS-NMR) has emerged as a powerful tool for the structure determination of membrane proteins in their physiological environments. However, the traditional spectroscopic assignment method in OS NMR that uses the "shotgun" approach, though effective, is quite labor- and time-consuming as it is based on the preparation of multiple selectively labeled samples. Here we demonstrate that, by using a combination of the spin exchange under mismatched Hartmann-Hahn conditions and a recent sensitivity-enhancement REP-CP sequence, spectroscopic assignment of solid-state NMR spectra of Pf1 coat protein reconstituted in magnetically aligned bicelles can be significantly improved. This method yields a two-dimensional spin-exchanged version of the SAMPI4 spectrum correlating the (15)N chemical shift and (15)N-(1)H dipolar couplings, as well as spin-correlations between the (i, i ± 1) amide sites. Combining the spin-exchanged SAMPI4 spectrum with the original SAMPI4 experiment makes it possible to establish sequential assignments, and this technique is generally applicable to other uniaxially aligned membrane proteins. Inclusion of an (15)N-(15)N correlation spectrum into the assignment process helps establish correlations between the peaks in crowded or ambiguous spectral regions of the spin-exchanged SAMPI4 experiment. Notably, unlike the traditional method, only a uniformly labeled protein sample is required for spectroscopic assignment with perhaps only a few selectively labeled "seed" spectra. Simulations for the magnetization transfer between the dilute spins under mismatched Hartmann Hahn conditions for various B (1) fields have also been performed. The results adequately describe the optimal conditions for establishing the cross peaks, thus eliminating the need for lengthy experimental optimizations.}, number={3}, journal={JOURNAL OF BIOMOLECULAR NMR}, author={Tang, Wenxing and Knox, Robert W. and Nevzorov, Alexander A.}, year={2012}, month={Nov}, pages={307–316} }
 @article{tang_nevzorov_2011, title={Repetitive cross-polarization contacts via equilibration-re-equilibration of the proton bath: Sensitivity enhancement for NMR of membrane proteins reconstituted in magnetically aligned bicelles}, volume={212}, ISSN={["1090-7807"]}, DOI={10.1016/j.jmr.2011.06.028}, abstractNote={Thermodynamic limit of magnetization corresponding to the intact proton bath usually cannot be transferred in a single cross-polarization contact. This is mainly due to the finite ratio between the number densities of the high- and low-gamma nuclei, quantum–mechanical bounds on spin dynamics, and Hartmann–Hahn mismatches due to rf field inhomogeneity. Moreover, for fully hydrated membrane proteins refolded in magnetically oriented bicelles, short spin-lock relaxation times (T1ρ) and rf heating can further decrease cross polarization efficiency. Here we show that multiple equilibrations-re-equilibrations of the high- and low-spin reservoirs during the preparation period yield an over twofold gain in the magnetization transfer as compared to a single-contact cross polarization (CP), and up to 45% enhancement as compared to the mismatch-optimized CP-MOIST scheme for bicelle-reconstituted membrane proteins. This enhancement is achieved by employing the differences between the spin–lattice relaxation times for the high- and low-gamma spins. The new technique is applicable to systems with short T1ρ’s, and speeds up acquisition of the multidimensional solid-state NMR spectra of oriented membrane proteins for their subsequent structural and dynamic studies.}, number={1}, journal={JOURNAL OF MAGNETIC RESONANCE}, author={Tang, Wenxing and Nevzorov, Alexander A.}, year={2011}, month={Sep}, pages={245–248} }