Roose B W, Zemerov S D, Dmochowski I J
Department of Chemistry , University of Pennsylvania , 231 South 34th St. , Philadelphia , PA 19104-6323 , USA . Email:
Chem Sci. 2017 Nov 1;8(11):7631-7636. doi: 10.1039/c7sc03601a. Epub 2017 Sep 20.
Genetically encoded magnetic resonance imaging (MRI) contrast agents enable non-invasive detection of specific biomarkers . Here, we employed the hyper-CEST Xe NMR technique to quantify maltose (32 nM to 1 mM) through its modulation of conformational change and xenon exchange in maltose binding protein (MBP). Remarkably, no hyper-CEST signal was observed for MBP in the absence of maltose, making MBP an ultrasensitive "smart" contrast agent. The resonance frequency of Xe bound to MBP was greatly downfield-shifted (Δ = 95 ppm) from the Xe peak, which facilitated detection in as well as multiplexing with TEM-1 β-lactamase. Finally, a Val to Ala mutation at the MBP-Xe binding site yielded 34% more contrast than WT, with Xe resonance frequency shifted 59 ppm upfield from WT. We conclude that engineered MBPs constitute a new class of genetically encoded, analyte-sensitive molecular imaging agents detectable by Xe NMR/MRI.
基因编码磁共振成像（MRI）造影剂能够非侵入性地检测特定生物标志物。在此，我们采用超化学交换饱和转移（hyper-CEST）氙核磁共振（NMR）技术，通过麦芽糖对麦芽糖结合蛋白（MBP）构象变化和氙交换的调节作用来定量检测麦芽糖（32 nM至1 mM）。值得注意的是，在没有麦芽糖的情况下，未观察到MBP的超化学交换饱和转移信号，这使得MBP成为一种超灵敏的“智能”造影剂。与氙峰相比，结合到MBP上的氙的共振频率发生了很大的向低场偏移（Δ = 95 ppm），这有利于检测，并且可以与TEM-1 β-内酰胺酶进行多重检测。最后，MBP与氙结合位点处的缬氨酸突变为丙氨酸后，造影效果比野生型（WT）提高了34%，氙的共振频率比野生型向高场偏移了59 ppm。我们得出结论，工程化的MBP构成了一类新的可通过氙核磁共振/磁共振成像检测的基因编码、对分析物敏感的分子成像剂。
