Dynamic Nuclear Polarization of Amyloidogenic Peptide Nanocrystals: GNNQQNY, a Core Segment of the Yeast Prion Protein Sup35p

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• 作者：Patrick C. A. van der Wel ; Kan-Nian Hu ; Jó ; zef Lewandowski ; Robert G. Griffin
• 刊名：Journal of the American Chemical Society
• 出版年：2006
• 出版时间：August 23, 2006
• 年：2006
• 卷：128
• 期：33
• 页码：10840 - 10846
• 全文大小：259K
• 年卷期：v.128,no.33(August 23, 2006)
• ISSN：1520-5126

文摘

Dynamic nuclear polarization (DNP) permits a ~10²-10³ enhancement of the nuclear spinpolarization and therefore increases sensitivity in nuclear magnetic resonance (NMR) experiments. Here,we demonstrate the efficient transfer of DNP-enhanced ¹H polarization from an aqueous, radical-containingsolvent matrix into peptide crystals via ¹H-¹H spin diffusion across the matrix-crystal interface. The samplesconsist of nanocrystals of the amyloid-forming peptide GNNQQNY_7-13, derived from the yeast prion proteinSup35p, dispersed in a glycerol-water matrix containing a biradical polarizing agent, TOTAPOL. Thesecrystals have an average width of 100-200 nm, and their known crystal structure suggests that the sizeof the biradical precludes its penetration into the crystal lattice; therefore, intimate contact of the moleculesin the nanocrystal core with the polarizing agent is unlikely. This is supported by the observed differencesbetween 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 anaverage signal enhancement 120. This is slightly lower than the DNP enhancement of the solventmixture surrounding the crystals ( 160), and we show that it is consistent with spin diffusion across thesolvent-matrix interface. In particular, we correlate the expected DNP enhancement to several propertiesof the sample, such as crystal size, the nuclear T₁, and the average ¹H-¹H spin diffusion constant. Theenhanced ¹H polarization was subsequently transferred to ¹³C and ¹⁵N via cross-polarization, and allowedrapid acquisition of two-dimensional ¹³C-¹³C correlation data.