Dynamic nuclear polarization of amyloidogenic peptide nanocrystals: GNNQQNY, a core segment of the yeast prion protein Sup35p
Dynamic nuclear polarization of amyloidogenic peptide nanocrystals: GNNQQNY, a core segment of the yeast prion protein Sup35p
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DOI：
10.1021/ja0626685
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发表时间：
2006-08-23
影响因子：
15
通讯作者：
Griffin, Robert G.
中科院分区：
文献类型：
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作者：
van der Wel, Patrick C. A.;Hu, Kan-Nian;Griffin, Robert G.
动态核极化(DNP)允许类似于10(2)-10(3)的核自旋极化增强，因此提高了核磁共振(NMR)实验的灵敏度。在这里，我们展示了DNP增强的H-1极化通过H-1-H-1自旋扩散通过基质-晶体界面有效地从含自由基的水溶液基质转移到多肽晶体中。这些样品由淀粉样形成肽GNNQQNY(7-13)的纳米晶体组成，该多肽来自酵母蛋白Sup35P，分散在含有双自由基极化剂TOTAPOL的甘油-水基质中。这些晶体的平均宽度为100-200 nm，它们的已知晶体结构表明，双自由基的大小阻止了其渗透到晶格中；因此，纳米晶体核心中的分子不太可能与极化剂亲密接触。这是由观察到的溶剂和纳米晶体中增强极化随时间增长的差异而得到支持的。然而，在5T和90K记录的DNP增强魔角旋转(MAS)谱显示平均信号增强epsilon接近120。这略低于晶体周围溶剂混合物的DNP增强(epsilon约为160)，我们表明这与溶剂-基质界面上的自旋扩散是一致的。特别是，我们将预期的DNP增强与样品的几个性质关联起来，例如晶体尺寸、核T-1和平均H-1-H-1自旋扩散常数。增强的H-1极化随后通过交叉极化转移到C-13和N-15，并允许快速获取二维C-13-C-13关联数据。
Dynamic nuclear polarization (DNP) permits a similar to 10(2)-10(3) enhancement of the nuclear spin polarization and therefore increases sensitivity in nuclear magnetic resonance (NMR) experiments. Here, we demonstrate the efficient transfer of DNP-enhanced H-1 polarization from an aqueous, radical-containing solvent matrix into peptide crystals via H-1-H-1 spin diffusion across the matrix-crystal interface. The samples consist of nanocrystals of the amyloid-forming peptide GNNQQNY(7-13), derived from the yeast prion protein Sup35p, dispersed in a glycerol-water matrix containing a biradical polarizing agent, TOTAPOL. These crystals have an average width of 100-200 nm, and their known crystal structure suggests that the size of the biradical precludes its penetration into the crystal lattice; therefore, intimate contact of the molecules in the nanocrystal core with the polarizing agent is unlikely. This is supported by the observed differences between the time-dependent growth of the enhanced polarization in the solvent versus the nanocrystals. Nevertheless, DNP-enhanced magic-angle spinning (MAS) spectra recorded at 5 T and 90 K exhibit an average signal enhancement epsilon approximate to 120. This is slightly lower than the DNP enhancement of the solvent mixture surrounding the crystals (epsilon approximate to 160), and we show that it is consistent with spin diffusion across the solvent-matrix interface. In particular, we correlate the expected DNP enhancement to several properties of the sample, such as crystal size, the nuclear T-1, and the average H-1-H-1 spin diffusion constant. The enhanced H-1 polarization was subsequently transferred to C-13 and N-15 via cross-polarization, and allowed rapid acquisition of two-dimensional C-13-C-13 correlation data.