Riggle Brittany A, Wang Yanfei, Dmochowski Ivan J
Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104-6323, United States.
J Am Chem Soc. 2015 Apr 29;137(16):5542-8. doi: 10.1021/jacs.5b01938. Epub 2015 Apr 20.
Here we present a "smart" xenon-129 NMR biosensor that undergoes a peptide conformational change and labels cells in acidic environments. To a cryptophane host molecule with high Xe affinity, we conjugated a 30mer EALA-repeat peptide that is α-helical at pH 5.5 and disordered at pH 7.5. The (129)Xe NMR chemical shift at room temperature was strongly pH-dependent (Δδ = 3.4 ppm): δ = 64.2 ppm at pH 7.5 vs δ = 67.6 ppm at pH 5.5, where Trp(peptide)-cryptophane interactions were evidenced by Trp fluorescence quenching. Using hyper-CEST NMR, we probed peptidocryptophane detection limits at low-picomolar (10(-11) M) concentration, which compares favorably to other NMR pH reporters at 10(-2)-10(-3) M. Finally, in biosensor-HeLa cell solutions, peptide-cell membrane insertion at pH 5.5 generated a 13.4 ppm downfield cryptophane-(129)Xe NMR chemical shift relative to pH 7.5 studies. This highlights new uses for (129)Xe as an ultrasensitive probe of peptide structure and function, along with potential applications for pH-dependent cell labeling in cancer diagnosis and treatment.
在此，我们展示了一种“智能”的氙-129核磁共振生物传感器，它在酸性环境中会发生肽构象变化并标记细胞。对于具有高氙亲和力的穴醚主体分子，我们连接了一个30聚体EALA重复肽，该肽在pH 5.5时呈α螺旋结构，在pH 7.5时无序。室温下的（129）Xe核磁共振化学位移强烈依赖于pH值（Δδ = 3.4 ppm）：在pH 7.5时δ = 64.2 ppm，而在pH 5.5时δ = 67.6 ppm，其中色氨酸（肽）-穴醚相互作用通过色氨酸荧光猝灭得以证明。使用超极化化学交换饱和转移核磁共振（hyper-CEST NMR），我们在低皮摩尔（10^(-11) M）浓度下探测了肽穴醚的检测限，这与其他核磁共振pH报告分子在10^(-2)-10^(-3) M时相比具有优势。最后，在生物传感器-海拉细胞溶液中，相对于pH 7.5的研究，pH 5.5时肽插入细胞膜导致穴醚-（129）Xe核磁共振化学位移向低场移动了13.4 ppm。这突出了氙-129作为肽结构和功能的超灵敏探针的新用途，以及在癌症诊断和治疗中pH依赖的细胞标记的潜在应用。
