Petkova Aneta T, Tycko Robert
Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA.
J Magn Reson. 2004 May;168(1):137-46. doi: 10.1016/j.jmr.2004.02.007.
We describe investigations of the effects of rotational resonance (R(2)) on solid state (13)C NMR spectra of uniformly (13)C-labeled samples obtained under magic-angle spinning (MAS), and of the utility of R(2) measurements as structural probes of peptides and proteins with multiple uniformly labeled residues. We report results for uniformly (13)C-labeled L-alanine and L-valine in polycrystalline form, and for amyloid fibrils formed by the 15-residue peptide A beta(11-25) with uniform labeling of a four-residue segment. The MAS NMR spectra reveal a novel J-decoupling effect at R(2) conditions that may be useful in spectral assignments for systems with sharp (13)C MAS NMR lines. Pronounced dependences of the apparent isotropic (13)C NMR chemical shifts on MAS frequency near R(2) conditions are also observed. We demonstrate the feasibility of quantitative (13)C-(13)C distance determinations in L-valine, and qualitative determinations of inter-residue (13)C-(13)C contacts in A beta(11-25) fibrils. Finally, we demonstrate a "relayed" R(2) technique that may be useful in structural measurements on systems with poorly resolved (13)C MAS NMR lines.
我们描述了旋转共振（R(2)）对在魔角旋转（MAS）下获得的均匀（13）C标记样品的固态（13）C NMR谱的影响，以及R(2)测量作为具有多个均匀标记残基的肽和蛋白质的结构探针的效用。我们报告了多晶形式的均匀（13）C标记的L-丙氨酸和L-缬氨酸，以及由15个残基的肽Aβ(11-25)形成的淀粉样纤维的结果，该肽的一个四残基片段具有均匀标记。MAS NMR谱揭示了在R(2)条件下一种新的J-去耦效应，这可能对具有尖锐（13）C MAS NMR谱线的系统的谱归属有用。还观察到在R(2)条件附近，表观各向同性（13）C NMR化学位移对MAS频率有明显的依赖性。我们证明了在L-缬氨酸中进行定量（13）C-（13）C距离测定以及在Aβ(11-25)纤维中进行残基间（13）C-（13）C接触定性测定的可行性。最后，我们展示了一种“中继”R(2)技术，这可能对具有分辨率较差的（13）C MAS NMR谱线的系统的结构测量有用。
